Drawings and principle of the rocket furnace. Do-it-yourself rocket furnace drawings and manufacturing process. Simple metal ovens

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The rocket stove was used by many peoples of the world long before the advent of modern home and household stoves. It served, first of all, for heating the dwelling and provided a warm sleeping place in the house. Cooking also played an important role. When designing the stove design, it was necessary to come up with a system that could operate at the highest possible efficiency when loaded with low quality wood fuel (in dry and wet form).

Nowadays, it is used for heating, for cooking, and also as an interior element. You can make a rocket stove with your own hands practically from improvised means. It all depends on its purpose and the place where it will be used.

There are many types and designs of a rocket furnace - from the simplest to multifunctional. For efficient operation, it is necessary to follow some rules for the operation of the furnace structure. There are 2 basic principles of operation of a rocket furnace, regardless of its configuration:

free circulation of released gases from the fuel through the formed furnace channels, without manual chimney draft;
afterburning of pyrolysis gases released from fuel burnout under conditions of insufficient oxygen supply.

Design, characteristics and application

The rocket stove owes its unique name to the characteristic stove hum that can be heard throughout the entire combustion process. It is remotely similar to the sound of a rocket taking off. The similarity with a rocket is also that in it, in the process of combustion, a jet thrust is created. The conical shape of the furnace can also be associated with the name, but this is not the main characteristic.

There are 2 types of furnace construction (shown in the diagrams):

The simplest rocket oven

The simplest design of a direct combustion rocket furnace is 2 pipes connected by a branch - a Russian rocket furnace.

The down tube is separated by a metal plate. The upper part of the pipe is approximately 2/3 of the total space where the main fuel is directly laid. The lower part serves as a primitive blower, which provides air exchange in the furnace.

The fuel filling in this case is horizontal. When laid vertically, a rocket-type furnace consists of two vertical pipes of different lengths, and a third horizontal one, which serves as a connecting channel. The latter performs the function of a furnace.

The simplest form of a jet stove is installed, usually outdoors, for the purpose of cooking food and heating water.

For the manufacture of a stationary simple brick rocket furnace, a material is used that is installed on a heat-resistant platform.

In order to achieve higher performance, new elements were added to the simplest design of the stove.

The diagram shows a camp jet furnace. The lower pipe is divided by a special jumper into a fuel compartment (2) and a compartment for venting air into the combustion area (3). The upper part of the furnace consists of a riser pipe, around which a heat-insulating composition (4) is laid, which is closed on top by an external metal casing (1).

The operation of the furnace is as follows: fuel (straw, paper) that warms up the furnace is placed in the fuel compartment, after burning through which the main fuel (wood chips, rods, etc.) is added. In the process of active combustion, hot gases are formed that rise along the riser and exit to the outside. A stand for cooking utensils is installed on the pipe cut, taking into account the gap of 7-10 mm. Otherwise, if the necessary clearance is not maintained, the outlet for oxygen draft will be blocked, which, in turn, raises the hot gases up. The combustion process will stop.

If the conditions for creating air draft are met, even with the furnace door closed, the combustion process will not stop. Here, the second principle of operation of a long-burning rocket furnace is partially triggered - the afterburning of pyrolysis gases in conditions of insufficient oxygen supply.

For this principle to work in full, it is necessary to provide the rocket furnace with high-quality thermal insulation of the secondary combustion chamber, because for the processes of formation and combustion of gases, temperature requirements must be met.

advanced design

This type of rocket stove in an advanced configuration can be used at home for both cooking and heating rooms. In addition to the fuel compartment and the pipe, there is a second building in it, at the top of which a hob is installed, and the chimney is led to the street. You can heat a room with an area of up to 50 sq.m. with such a stove.

As a result of the modernization, useful qualities and efficiency are increased due to the fact that the long-burning rocket furnace acquires several unique and important properties:

in contrast to the simple design of the rocket furnace, the advanced one uses a second outer casing, a thermally insulating material around the combustion pipe, a hermetically sealed upper part of the casing, which creates conditions for maintaining a high temperature for a long time;
an independent opening for secondary air supply in the modernized furnace performs optimal blowing, while in a simple design an open furnace is used for this;
the chimney system is designed in such a way that the heated gas flow does not immediately rush out of the pipe, but passes through the furnace channels, ensuring high-quality afterburning of the secondary fuel, heating the hob and uniform heat transfer of the air in the room through the heated furnace body.

The improved design uses additional elements focused on creating high heat transfer and multifunctionality of the rocket furnace. Two principles of operation of the furnace are actively involved here. First, there is a preliminary combustion of solid fuel, which, during combustion, releases pyrolysis gases, which are used as secondary fuel.

The principle of operation of a rocket furnace of this design is shown in detail in the diagram on the left. The fuel compartment (1) is loaded with fuel for pre-combustion. In the zone of the most active heat exchange (2), under conditions of insufficient supply of primary oxygen (A), regulated by a damper (3), pyrolysis gases are released. They rush to the end of the fire channel (5), where they are burned out. Favorable conditions for the combustion of gases are created due to the high thermal insulation of the structure and the continuously incoming flow of secondary oxygen (B).

The hot gas then rises up the internal channel of the riser pipe (7) under the housing cover, which is often equipped under the hob (10), due to continuous high-temperature heating. There, the accumulation of gas diverges through the channels located between the riser and the outer furnace body (6). In conditions of constant heating of the body, its walls accumulate heat, from which the air in the room heats up. After that, the gas flow descends down the channel, and then goes up into the chimney pipe (11).

The burning process can last several hours. For maximum heat transfer of the furnace and complete combustion of pyrolysis gases, it is necessary to maintain a consistently high temperature in the riser. To do this, it is placed in a pipe of a slightly larger diameter, which is called a shell (8). The formed space between the two pipes is tightly filled with a heat-resistant composition, such as sifted sand, to provide thermal insulation in the pipe.

Features of the operation of the rocket furnace

Before loading the main fuel, the furnace must be warmed up. This is more about large and multifunctional rocket ovens. In them, without preheating, thermal energy will be used for nothing.
To accelerate the furnace, dry paper, wood shavings, and straw are placed in an open blower. Sufficient heating of the furnace can be determined by the hum in the furnace, which subsequently subsides. Then, the main fuel is put into the heated rocket stove, which is ignited by the accelerating fuel.
At the beginning of the combustion of the main fuel, the blower door is opened completely. After a while, as the stove rumble appears, the blower is covered until the rumble is replaced by a whisper. In the future, to assess the state of combustion of the furnace, it is also necessary to focus on the “stove sound”, slightly opening the blower door when it subsides and covering it when a rumble occurs.
The larger the reactive oven, the smaller the fresh air opening needed. It is advisable to use a separate blower in such a furnace.
The adjustment of the power of the furnace operation can occur only due to the amount of fuel put in, but not due to the air supply.
When making a large rocket furnace on your own, its bunker should be made with a tight-fitting lid, without gaps and cracks. Otherwise, a stable operating mode of the furnace will not be ensured, which is fraught with the consumption of excess fuel energy.
Contrary to popular belief, a rocket stove for a bath is not suitable for installation, since the stove does not emit sufficient infrared radiation, which is necessary for heating walls and giving off convection to the air masses in a bath. The rocket stove for a bath, theoretically, can only be installed using the Shirokov-Khramtsov stove type, the characteristics of which are given below.
A rocket stove for a garage is a mobile version of a stove design that can quickly heat up a room. The main element is a heating tank from a pipe.

Fuel types

With proper assembly and operation, a rocket stove can be fired with any type of solid fuel, wood and its waste. For example, branches, leaves, firewood, coal, corn stalks, cones, pieces of chipboard, pieces of furniture. It is possible to load fuel into the furnace both in dry and raw form. This is especially true for its operation in natural conditions, where it is not always possible to find dry raw materials.

Varieties of rocket furnaces

The rocket furnace can be made independently or to order from various materials. Here it is necessary to focus on the possibilities and available resources.

Gas cylinder stove

A used gas cylinder is a common material for making a stove. The convenience of its use lies in the fact that it is, in fact, a ready-made blank of an elongated cone-shaped furnace body. Fuel costs are minimal, and the heat generated will heat a room up to 50 sq.m. The material of the cylinder must be chosen not explosive and resistant to high temperatures and heat. The best option is a solid metal propane tank with a capacity of 50 liters, a diameter of 35 cm and a height of 85 cm. This volume is enough to burn any type of fuel.

Also, for the manufacture of a portable rocket furnace from a gas cylinder, volumes of 12 and 27 liters are used, but with less heat transfer. The cylinder can be purchased at a special gas station.

Before starting the manufacture of the furnace, gas is vented from the cylinder by opening the valve for a while. Then, a simple potbelly stove is made. Next, the upper part of the cylinder is cut off, the hole for the valve remains. A round hole with a welded steel strip is cut out at the top, which serves as the basis for the chimney.

brick oven

It can be both stationary and traveling. Hastily folded, in 15-20 minutes, a dry rocket stove made of bricks, brick fragments or cobblestones will do an excellent job of cooking and heating water. The disadvantage of such a furnace is the low fuel economy and low heat transfer. Heating the bricks in the chimney up to 1000 degrees allows the structure to quickly enter the operating mode. At the same time, the rocket does not smoke due to the fact that at such a temperature all the fuel burns without residue.

Rocket furnace with water jacket

The most commonly used stationary furnace type. The peculiarity of such a furnace is that heat transfer is not only for heating the air in the room, but also for water. To do this, a rocket furnace with a water circuit is connected to a heat storage tank - to create an autonomous water supply system. Ideal for use in a country house or in private water, because the device helps to reduce heating and water heating costs, which is very economical.

Barrel oven

A common model for home heating. Low-cost in manufacturing and energy-intensive in heat transfer. Often equipped with a warm bed. Able to heat a room of more than 50 square meters. m. For the manufacture of the stove, a standard 200-liter barrel with a diameter of 607 mm is perfect. This diameter can be reduced by almost half, which is convenient for embedding a riser pipe made from a gas cylinder or tin buckets with a diameter of 300-400 mm. In a word, the oven can be made from improvised materials.

Shirokov-Khramtsov oven

Domestic modernization of the rocket furnace. The main material is heat-resistant concrete, which creates excellent thermodynamics in the structure. Due to the stable operation of the furnace and the low thermal conductivity of the material, part of the heat comes out in the form of infrared radiation, which is impossible with other types of furnaces. If you use heat-resistant glass, then the stove can be adapted for a fireplace. The disadvantage of installing such a furnace is the high cost of the material, the preparation of which will require a concrete mixer.

stove-stove

For cooking and preparations at home and outdoors, an improved oven design with a wide hob for installing several containers is installed. A vertical riser pipe with a firebox welded to it is located directly under the hob, providing high-temperature heating. Accumulating under the cover of the panel, the gases exit through a horizontal pipe, heating the entire area of the panel evenly, and rush to the exit through the vertical chimney channel.

How to DIY

Let's take a closer look at the manufacture of a do-it-yourself rocket stove with a stove bench. Its design is more cumbersome, more difficult to install than the types of furnaces listed above, but thanks to step-by-step instructions and diagrams, it will not be difficult to build it yourself. The main thing is to follow all installation recommendations.

Step by step instructions on how to make a rocket stove:

First, make a 10 cm deepening for installing the fuel compartment, laying it out with fireclay bricks. Then you need to install the formwork along the construction line. For a stronger foundation, you can use building reinforcement or mesh, laying it on a brick base.
Using a level, lay out the base for the combustion chamber.
Then you need to fill the structure with concrete, and allow to dry for a day. After the mortar has set, you can continue to build the furnace.

Lay out the base of the furnace, laying the bricks in a continuous order.
Form the side walls by laying several rows of masonry.
Complete the arrangement of the lower channel of the rocket, taking into account the order.
Then you need to lay a row of transverse bricks so that the riser pipe and the combustion chamber remain open, and the combustion chamber is hidden.

You need to take the body of the old boiler and cut it off on both sides so that you end up with a pipe that is wide in diameter.
A flange is installed in the lower part of the body from under the fuel and lubricants, into which the pipe of the horizontal heat exchanger will be installed. To maintain the tightness and safety of the product, it is necessary to provide for the use of continuous welds in the work.

After that, the outlet pipe crashes into the barrel. The barrel is cleaned of rust, covered with a primer and several layers of heat-resistant paint.
To the chimney, located horizontally, you need to weld a side outlet to form an ash pan. To facilitate its cleaning, during the operation of the furnace, the channel must be equipped with a sealed flange.
Next, a fire tube is laid out of refractory bricks, observing the dimensions of 18 × 18 cm square. When laying out the internal channel, it is important to observe strict verticality for the stable operation of the furnace. To do this, you can use a body kit or level.

It is necessary to put a casing on the flame tube, and place perlite balls in the resulting space. The lower part of the riser must be hermetically covered with a clay mixture to prevent spillage of the heat insulator.
Then the fuel cap is made - using the previously cut off part from the boiler. For convenience, a handle can be welded to the lid.
Mix the clay mortar with sawdust (do not allow the product to crack), up to 50% of the total volume. The result is the so-called "adobe grease", which needs to be coated with the appearance of the resulting structure to mask unsightly details and increase thermal insulation.

Next, the appearance of the furnace is formed. The furnace circuit is laid out. To do this, you can use different materials: stone, brick, sandbags. The inner part is filled with rubble, and the upper part is smeared with adobe mixture.
A 200-liter barrel, which serves as an external furnace body, is installed on a previously prepared base. Be sure to install the barrel so that the lower pipe is on the side of the couch. Further, the lower part is covered with clay for sealing.
Then, from the corrugated pipe, you need to form a channel for supplying air from the street, bring it to the fuel compartment. Without installing such a channel, a do-it-yourself rocket stove will consume warm air from the room during operation.

After the construction of the main part of the furnace structure, a training kindling is carried out to check the free removal of gases through a horizontal chimney.
The heat exchanger pipes are connected to the lower branch pipe, mounted on a red brick base.
Next, you need to install the chimney pipe with your own hands, hermetically sealing all connections with an asbestos cord or refractory coating.
At the end, the couch must be shaped in the same way as before - when forming the main body. If you leave the barrel open, without masking with adobe, then the heat during combustion will instantly enter the room. If the barrel is covered with adobe completely, leaving the lid intact, then the heat will accumulate in the body, which will create excellent conditions for cooking on the hob.

Instead of a barrel, you can use a gas cylinder (rocket stove from a gas cylinder), and instead of a boiler, you can use pipes fitted to the shape, tin buckets. When creating a rocket furnace with your own hands, it is very important to observe accuracy and proportionality in size using drawings. This will guarantee a long and efficient operation of the do-it-yourself long-burning furnace.

The benefits of using homemade rocket stoves in everyday life are significant. The construction of the furnace does not require large economic costs (for materials, heating) and time (it takes a maximum of 3-4 days to manufacture the furnace).

High performance and heat transfer with unpretentious fuel loading is ideal. You can decorate the oven in any way you like, thereby adding a new interior element to the house.

To date, quite a lot of varieties and models of wood-burning stoves have been developed and implemented. In this series, the do-it-yourself rocket furnace built with your own hands, the drawings of which will be presented below, fully justifies all expectations. Such a heating structure, of course, deserves close attention, as it has some specific advantages that are indispensable in certain conditions.

This version of the wood stove is simple and original in design and does not require a large number of expensive components and materials for the manufacture. Probably anyone can install such a stove, having made it on their own, even if they have no experience in the construction of such structures, but who can read the provided drawings and work with some tools.

It is interesting to note that, if necessary, a rocket stove can be made even in 20–30 minutes, for example, from an iron can. However, if you make every effort, it is possible to get a comfortable stationary structure for your home with a heated bench that can even replace an ordinary sofa.

The principle of operation of the rocket oven

The rocket stove was originally conceived as one of the functional survival items in difficult conditions. Therefore, its design had to meet certain criteria:

Efficient space heating.
Possibility of cooking.
High efficiency of the device when using various wood fuels of any quality for heating.
The ability to report fuel without stopping the combustion process.
In addition, the stove had to keep warm for at least 6-7 hours to enable the owners to spend the night in comfortable conditions.
Maximum safety of the structure, in terms of eliminating the possibility of carbon monoxide seepage into the room.
Another condition that had to be met was the simplicity and accessibility of the design for its manufacture by any non-professional.

Therefore, the basis was taken basic principles several types of heating appliances operating on wood solid fuels:

Free circulation of heated air and gases through all channels. The furnace works without forced blowing, and the chimney creates draft, which draws out the products of combustion. The higher the pipe is raised, the more intense the thrust in it.
The principle of afterburning the gases released during combustion from the fuel (pyrolysis), which is used in long-burning devices. This principle of operation is extremely important due to the high efficiency of the device, which is achieved by creating special conditions for the afterburning of pyrolysis gases for the most complete consumption of the energy potential inherent in the fuel.

The term "pyrolysis" means the decomposition of solid fuel into volatile substances, under the influence of high temperatures and simultaneous "oxygen starvation". Under certain conditions, they are able to burn out, also releasing a large amount of thermal energy. At the same time, it is important to know that the pyrolysis of insufficiently dried wood takes place for quite a long time in the gas phase, that is, the released pyrolysis gas will require a lot of heat to create a mixture (wood gas) that can burn completely. Therefore, it is not recommended to use wet fuel for the rocket stove.

A variety of rocket stoves - from simple to complex

The simplest design of a rocket furnace

In a simple design of a rocket stove, heated by bundles of branches or torches, the combustion products almost immediately go into the chimney, without having time to form combustible wood gas in the stove body, so it will not be possible to heat the room with it. Such ovens can only be used for cooking. This model is manufactured in stationary and mobile versions; only the principle of free circulation of heated air operates in it, since it does not create the required conditions for a full-fledged pyrolysis process.

In such furnaces, a small section of pipe is used as a fuel chamber. It can have a horizontal position, as shown in the diagram, or be turned up. In the latter case, fuel is loaded vertically.

After igniting the fuel placed in the pipe, the heated gases released from it rush up the vertical section of the pipe to the outside.

On top of the vertical pipe and install containers for cooking or heating water. In order for the gases to freely escape to the outside, and the bottom of the tank does not completely block the draft in the pipe, a special metal stand is installed on top of the stove. She creates a gap of the right size, which helps maintain traction.

Above - a very original stand for a container of heated water

By the way, this simplest type of furnace device was invented first, and because of the furnace opening turned upwards and the flame escaping from it, the furnace most likely got the name rocket. In addition, if the furnace mode is incorrect, the structure emits a whistling “rocket” rumble, but if the furnace is set up correctly, it rustles quietly.

Advanced Rocket Furnace

Since, using the simplest rocket stove with a free exit of gases, it is impossible to heat the room, the design was later supplemented with a heat exchanger and smoke ducts.

After the improvements made, the whole principle of operation of the rocket furnace has changed somewhat.

In order to keep the high temperature of the heated air in the vertical pipe, they began to insulate it with a fire-resistant material, and then close it on top with another metal case made from a larger diameter pipe or a metal barrel with a closed top.
A door was installed on the opening of the furnace, and a separate channel for secondary air appeared in the lower part of the furnace. Through it, blowing began to be carried out (necessary for the afterburning of pyrolysis gases), which previously occurred through an open firebox.
In addition, the chimney was moved to the lower part of the hull, which forced the heated air to circulate throughout the hull, bypassing all internal channels, and not escaping directly into the atmosphere.

The products of combustion, having a high temperature, first began to rise to the ceiling of the outer case, accumulate there and heat it, which made it possible to use the outer horizontal surface as a hob. Then, the gas flow cools down and goes down, turns into a knee and only from there goes into the chimney.
Due to the inflow of secondary air, afterburning of gases occurs at the end of the lower horizontal channel, which significantly increases the efficiency of the furnace. The free circulation of gases creates a self-regulating system that limits the flow of air into the combustion chamber, since it is supplied only as the hot gases cool down under the "ceiling" of the housing.

A very popular scheme - from a metal profile and an old gas cylinder

The stove model shown in the figure works like a “potbelly stove” and has a chimney brought out to the street. However, it is unsuitable for use in residential premises, since in it, with changes in external pressure, a reverse draft may occur, which will contribute to the entry of carbon monoxide into the premises. Therefore, such a stove should always be supervised, and it is most often used for heating utility rooms or a garage.

Rocket stove with warm bed

According to the principle of afterburning pyrolysis gases, a rocket furnace with a stove bench is also arranged, but in this embodiment, the heat exchanger is a structure of combined long channels coming from the stove and laid or formed from non-combustible plastic materials under the stove bench surface.

It should be noted that such a heating system is by no means new, and, in fact, such a rocket stove has a rather rich history. It was invented a long time ago, presumably in Manchuria, called " kan", and is still traditional for peasant houses in China and Korea.

Similar stoves called "kan" have long been used to heat homes in East Asia.

The system is a wide couch made of stone, brick and clay, inside which the air heated in the furnace passes through the arranged channels, which are essentially an elongated chimney. Passing through this labyrinth and gradually giving off heat, the gas flow, cooling down, exits into a chimney 3000 ÷ 3500 mm high, located on the street, next to the house.

The stove itself is located at one end of the bench and, as a rule, is equipped with a hob, which allows it to be used for cooking.

From above, the stone-clay construction "kan" is covered with straw or bamboo mats, or a wooden flooring is arranged there. At night, the couches were used as beds, and during the day - in the form of a seat, on which, traditionally for Asian peoples, a special low table 300 mm high was installed - after which a meal was held.

This heating system is quite economical in terms of fuel consumption, since it is enough to use an average thickness of a branch to heat it. Such a rocket stove is able to retain heat for a long time, creating comfortable conditions for sleeping throughout the night.

And Korean stoves "ondol" probably became the prototypes of modern "warm floors"

Korean homes use a heating system similar to " kan", which is called "ondol". This heating option, unlike the Chinese one, is not arranged inside the couch, but under the entire floor of the house. In principle, it can be argued that this method of transferring and distributing heat to residential premises seems to have formed the basis for the design of the modern "warm floor" system.

Furnace design with connected pipes to it can be clearly seen in the diagram presented.

In our time, with today's rich variety of materials, the channels in this furnace design can be made of metal pipes laid in the form of a coil and well thermally insulated with non-combustible materials. Therefore, the last section of the chimney system can exit from the structure of the bench next to the stove itself or at the end of the bench, and then go through the wall into the chimney pipe installed on the street.

In the presented diagram, you can see the results of design work, which made it possible to achieve a relatively simple circuit with high efficiency, as well as meeting all the requirements for a speech rocket.

Fuel is loaded into the furnace hole vertically. Then it is set on fire, and, burning out, gradually settles down. The air that supports combustion enters the bottom of the combustion chamber through an opening that plays the role of a blower. It must provide sufficient air flow for the afterburning of the released products of the thermal decomposition of wood. But, at the same time, there should not be too much air, since it can cool the initially released gases, and in this case the process of afterburning pyrolysis gases will not be able to take place, and the combustion products will settle on the walls of the housing.

In this variant, the top-loading furnace has on the furnace chamber blank cover, which eliminate the risk of gases entering the room when creating reverse thrust.

In a completely isolated volume of released gas, thermal energy is generated, temperature and pressure increase, and thrust increases. As the fuel burns, the burning gases go through the channels of the furnace body into the heat exchanger, heating the internal surfaces along the way. Since the channels have a complex configuration, gases are retained inside the furnace for a longer time, giving off heat to the body and channel surfaces, which in turn, they heat the surface of the couch and, accordingly, the room itself.

Over time, any furnace and its channels require cleaning from soot deposits. In this design, the problem area is the heat exchanger pipes located inside the bench. In order to carry out these preventive measures without problems, at the level of the heat exchanger turning from the furnace body into the pipes under the bench, a hermetically closing cleaning door is installed (indicated in the diagram as “Secondary Airtight Ash Pit”). It is in this place that all the unburned products of the thermal decomposition of wood concentrate and settle. The door is periodically opened and the passages are cleaned of soot - this process guarantees long-term operation of the chimney. In order for the door to close tightly, asbestos gaskets must be fixed to its inner edges.

How to properly heat a rocket stove?

To get the maximum heating effect, it is recommended to heat up the furnace before laying the bulk of the fuel. This process is carried out using paper, dry shavings or sawdust, which are ignited in a firebox. When the system warms up, it will change the emitted sound - it may die out or change its tone. The main fuel is placed in the heated unit, which will ignite from the heat already created by heating.

Any firewood and even thin branches are suitable for a rocket stove, but the main thing is that they are dry.

Until the fuel flares up well, the door of the combustion chamber or blower must be kept open . But only when the fire becomes intense, and the stove buzzes, the door is covered. Then, in the process of burning, the access of air from the blower is gradually blocked - here you need to focus on the tone of the stove sound. If the air damper is accidentally closed, and the intensity of the flame has decreased, it must be opened again and the stove will flare up with renewed vigor.

Advantages and disadvantages of a rocket stove

Before proceeding to the description of the manufacturing process of the rocket furnace, it is desirable to summarize the information about its advantages and disadvantages.

Rocket stoves are quite popular due to their positive qualities , which include:

Simplicity of design and a small amount of materials.
Even a novice master can make any of the furnace designs, if desired.
The construction of a rocket furnace does not require the purchase of expensive building materials.
Undemanding to the forced draft of the chimney, self-regulation of the furnace.
High efficiency of the rocket furnace with a pyrolysis gas afterburning system.
Possibility of adding fuel during furnace firing.

Despite the large number of advantages of this design, its work has a number of shortcomings :

When using the simplest design of a rocket stove, only dry branches and splinter can be used, since excess moisture can give back thrust. In a more complex system of the device, the use of wet wood is also not recommended, because it will not give the right temperature for pyrolysis to occur.
The rocket stove cannot be left unattended during combustion, as this is very unsafe.
This type of device is unsuitable for heating a bath, as it does not give enough heat in the infrared range, which is especially important for a steam room. A rocket stove with a stove bench can only be suitable for a rest room in a bath building.

Video: dissenting opinion on rocket stoves

Making a rocket stove with a bench

Rocket stoves can be of different sizes, and a variety of materials are used for their manufacture - these are metal pipes, barrels and gas cylinders, bricks and clay. A combined option is also quite acceptable, consisting of pipes, stones, clay and sand. It is he who deserves special attention.

From a gas cylinder, you can make a stove that is simple in design, including using it for the option with a stove bench.

How to make a simple stove in itself is more or less clear from the above drawings and a description of its work, so it is worth considering the manufacture of a heating unit equipped with a stove bench.

Video: homemade rocket stove from a gas cylinder

You may be interested in information on how to do with step by step instructions

To make it completely clear what and where is located in the design of the rocket furnace, this scheme will be used to describe the work.

So, the considered furnace-rocket consists of the following elements:

1a- a blower with an air supply regulator, with which the stove is adjusted to the desired mode;
1b- a fuel chamber (bunker) with a blind cover;
1v- a channel for supplying secondary air, which ensures complete combustion of pyrolysis gases emitted by wood;
1g– flame tube 150÷200 mm long;
1d- primary chimney (riser), with a diameter of 70 ÷ 100 mm.

The flame tube must not be made too long or too short. If this element is too long, then the secondary air in it will quickly cool down and the process of afterburning pyrolysis gases will not reach the end.

The entire design of the flame tube and riser must be thermally insulated as efficiently as possible. The task of this node is to ensure the complete combustion of pyrolysis gases and the supply of hot masses from the riser to other channels, which will already transfer heat to the room and to the bench.

Here it should be noted that in order to obtain the optimal efficiency from the furnace, the diameter R the aizer should be made with a size of 70 mm, and if the goal is to achieve the maximum power of the furnace, then it should be made with a diameter of 100 mm. In this case, the length of the flame tube should be 150÷200 mm. Further, when describing the installation of the furnace, the dimensions will be given for both cases.

It is impossible to immediately let the heated air from the riser into the heat storage, since its temperature reaches 900÷1000 degrees. High-quality heat-resistant heat-accumulating materials have a rather high price, therefore, most often, adobe (clay mixed with chopped straw) is used for these purposes. This material has a high heat capacity potential, but is not heat-resistant, so the design of the secondary furnace (cylinder body) begins with an air temperature converter, which must be heated to only 300 degrees. Part of the generated heat is immediately given into the room and replenishes the current heat loss.

The described functions are performed by the furnace body, made from a standard 50 l gas cylinder.

2a- cover of the furnace body. Under it, heated air enters from the riser;
2b- a cooking surface, which is heated from the inside by heated gases leaving the riser;
2c– metal insulation of the riser (shell);
2g– heat exchange channels. Heated gas enters them, dispersing under the ceiling of the case;
2d– the lower metal part of the case;
2nd– exit from the housing to the cleaning chamber.

The main task in the arrangement of these parts of the furnace is to ensure complete tightness of the chimney line.

In the housing (drum), at a height of ⅓ from its "ceiling", the gases cool down and already have a normal temperature for their entry into the accumulator. Approximately from this height and to the floor of the room, the oven thermally insulated several layers of different compositions - this process is called lining.

3a- the second cleaning chamber, through which the heat exchanger ("hog"), located under the bench, is cleaned from carbon deposits;
3b– sealed door of the second cleaning chamber;
4 - "hog", a long horizontal section of the chimney, located under the stove bench.

After passing through the pipes of the "hog" and almost completely giving off heat to the adobe stove, the gases escape through the main chimney channel into the atmosphere.

Having dealt with the device of the rocket furnace in detail, you can proceed to its construction.

Building a rocket oven with a stove bench - step by step

First of all, you need to prepare lining compositions. Their components will cost quite inexpensively, since they can often be found completely free of charge, literally under your feet:

5a- adobe. As mentioned above, this is clay mixed with chopped straw and mixed with water to the density of the masonry mortar. Clay for making adobe is suitable for any, since it will not be influenced by external atmospheric influences;
5 B- kiln clay mixed with crushed stone. This will be the main heat insulator. The mortar should have the consistency of a mixture for laying bricks;
5v- heat-resistant lining, made of kiln clay and fireclay sand in proportions of 1: 1 and having the consistency of plasticine;
5g- ordinary sifted sand;
5d - medium-fat clay for kiln masonry.

Step-by-step work on the design is carried out in the following sequence:

Bed for a couch

Having prepared all the necessary compositions, a bed is made - a wooden durable shield of the desired configuration. Its frame is made of timber with a section of 100 × 100 mm. Frame - with cells measuring 600 × 900 mm under the stove and 600 × 1200 mm under the bench. If a curvilinear shape of the couch is planned, then it is brought to the desired configuration with the help of boards and scraps of timber.

Bed - frame base for further construction of the furnace structure

The frame is sheathed with a grooved board 40 mm thick - it is fixed across the long sides of the frame. Later, after the installation of the furnace is completed, the side facade of the bed will be sheathed with drywall. All parts of the wooden structure of the bed must be impregnated with a biocide, and then stained twice with a water-based emulsion.

Further, on the floor, in the place of the room where the stove will be installed, mineral cardboard (cardboard made of basalt fibers) 4 mm thick is laid, the size and shape are fully consistent with the parameters of the bed. Directly under the stove, a sheet of roofing iron is fixed on top of the cardboard, which will come out from under the stove in front of the firebox by 200 ÷ 300 mm.

Then, the bed is transferred and firmly installed on the selected and made location oven, so that the frame stands stably, without play. At the end of the future couch, at a height of 120 ÷ 140 mm above the level of the bed, a hole for the chimney is arranged in the wall.

Formwork and pouring the first level of adobe mixture

A solid formwork is installed along the entire contour of the bed, having a height (A -40 ÷ 50 mm) and a smooth upper edge.

An adobe mixture (5a) is poured into the formwork and its surface is leveled using a rule. Formwork sides serve as beacons for leveling.

Production of the furnace body

While the adobe filling will dry, and this process will take 2-3 weeks, you can start making the furnace body from a cylinder. It should be noted that a rocket stove is made from a barrel in the same way.

Cutting a gas cylinder and making a cap with a "skirt"

The first step is to cut off the top from an empty cylinder to obtain a hole with a diameter of 200 ÷ 220 mm. Further, this hole is closed with a 4 mm thick steel round timber prepared in advance - this surface will play the role of a hob. After that, another cut is made below the hob by 50 ÷ 60 mm in order to get a lid.
On the outer perimeter of the resulting cover is welded, so-called"skirt" made of thin sheet steel. The width of the skirt should be 50 ÷ 60 mm, the seam of this strip is welded. If there is no experience in welding work, then it is better to entrust this process to a professional.
After that, along the entire circumference of the skirt, stepping back from the lower edge of 20 ÷ 25 mm, holes are evenly drilled into which the bolts will be screwed.
Further, the lower empty part of the cylinder is cut off at a height of approximately 70 mm from the bottom. Then, a hole is cut in the bottom of the cylinder for the riser to enter the body.
After that, it is necessary to fix a well-woven asbestos cord on the inner edge of the lid with Moment glue, and then immediately put it on the cylinder body and press it down with a load of 2.5 ÷ 3 kg from above. The cord will serve as a sealing gasket. Further, through the holes in the metal “skirt”, through holes are drilled in the cylinder body, in which the threads for the bolts are cut.
After that, you need to measure the depth of the hull, since it is necessary to determine the height of the riser.
Then the cap is removed from the cylinder to protect the gasket from being completely impregnated with glue, otherwise the asbestos will lose its elasticity.

Production of the furnace part of the furnace

The next step is to make elements from a square pipe (or channel) with a section of 150 × 150 mm: 1a - blower, 1b - combustion chamber; 1d - flame channel.

The riser (1d) is made from a round pipe with a diameter of 70 ÷ 100 mm.

The angle of insertion of the combustion chamber (bunker) into the blower and flame tube can vary within 45 ÷ 60 degrees from the horizontal. Its upper edge is placed flush with the protruding blower element, as shown in the diagram.

In the lower part of the blower and flame tube, it is necessary to separate the secondary air channel (1c). It is separated by a metal plate 3 ÷ 4 mm thick. Its rear edge should end exactly at the level of the front wall of the riser, and the front edge should go ahead of the blower by 25÷30 mm. The plate is pinpointed in four places by welding inside the pipe.

Then, at the end of the flame tube, a hole is cut from above, into which the riser is welded at a right angle, and the end of this channel is closed with a metal square, also fixed by welding.

Must be installed on the blower door - latch to help regulate the air supply. The cover for the combustion chamber is made of galvanized metal. The hopper does not require hermetic closure - the main thing is that the lid fits snugly against the inlet.

After that, the finished structure is coated with a solution of 5v. A solid lining is made only at the bottom, and the sides and top of the blower are left free from the lining. In order for the coating mixture to dry out faster, the structure is put on the pole with a blower chamber. It is necessary to ensure that the mixture from the surfaces does not slip and does not opal, since the lining plays a big role in retaining heat. If this happens, then the coating must be done again, using a fatter clay.

Rocket Furnace Insulation

After the adobe layer has dried, a formwork is installed to equip the heat-resistant thermal insulation for the furnace. It is done only under the location of the furnace. The height of the formwork will be 100÷110 mm together with the adobe layer.

The installed formwork is filled with composition 5b and leveled along the beacons, which will serve as the sides of the formwork. On the main diagram, this layer is marked with the letter B.

Production of the bottom part of the drum and shell

The shell is made from a round pipe with a diameter of 150 ÷ 200 mm or it is rolled from a steel sheet.

The bottom round timber, which will be laid inside the drum, is cut out of sheet metal with a thickness of 1.5 ÷ 2 mm, and a round hole is cut out in the middle of it. The diameter of the circumference of this element should be 4 mm less than the inner size of the cylinder, and the diameter of the middle cutout for the shell should be 3 mm larger than its outer diameter.

Installation of the furnace structure

After the thermal insulation layer has dried in the formwork, a furnace structure is mounted on it. It is installed by controlling the level vertically and horizontally, and then fixed on the heat-insulating layer with the help of pegs. Then, around the furnace, formwork is installed with a height of 350 ÷ 370 mm from the floor. Here it should be taken into account that the cleaning chamber (3a) and its door (3b) must be installed next to the solidified mixture (5b) with which the formwork will be filled. The connection (2e) of the cleaning chamber with the heat exchange channel (2g) will pass over the lining composition poured into the formwork. The mixture is also aligned to the ideal, level with formwork, with regulations.

cleaning chamber

While the mixture is drying in the formwork, you can start manufacturing a cleaning chamber with a door and a transition to a heat exchanger. It is made of galvanized steel, 1.5 ÷ 2 mm thick, and its front part is made of metal 4 ÷ 6 mm. A hole with a diameter of 150 ÷ 180 mm is cut out in the side part of the cleaning chamber to install the end of the chimney pipe, which will pass under the lounger.

The door of the cleaning chamber is made with a size of 160 × 160 mm, also from steel of 4 ÷ 6 mm. Before its installation, a sealing gasket made of mineral cardboard is installed along the perimeter of the inner surface. The door itself is screwed to the chamber box with fixing bolts, for which threads are cut in the drilled holes.

This diagram shows the dimensions of all elements and the place of installation and connection of the chamber with the drum (cylinder). Further, after fitting the elements, a 70 mm window is cut out in the lower part of the furnace drum, into which the connecting channel (2e) will be mounted by welding.

The corrugated pipes under the bench can be located arbitrarily, depending on the configuration of the lounger, it is only important to adhere to the dimensions indicated on the drawing for the manufacture of the cleaning chamber, indicated under the letters A, B and C. How to properly connect the "boar" pipe will be discussed below.

Drum mounting

When the solution in the formwork dries, it is removed. On the riser, on top of the frozen thermal insulation, they put on a combustion system drum made of a gas cylinder. The drum is currently mounted without a cover - its installation is shown in the diagram.

Solution 5b is laid out on the bottom part of the installed drum, and with the help of a spatula, a surface inclined by 6–8 degrees is formed from it, towards the outlet window of the cleaning chamber. Then, on the riser, a round timber from a metal sheet is put on and lowered to the bottom of the drum and pressed against the laid mortar. From the middle hole around the riser, the solution is selected, otherwise it will not be possible to install the shell pipe. After that, the pipe itself is put on the freed space on the riser and slightly screwed into the solution. All gaps formed along the outer and inner contours are smeared with clay (5d).

Fuel structure lining from the inside

After installing the shell and hearth, it is not necessary to wait for the thermal insulation solution to dry, you can immediately proceed to the riser lining. The composition (5g) is poured into the shell, around the riser, in 6÷7 layers. Each of the layers must be compacted as much as possible, while wetting the dry mixture with water from a spray bottle. From above, this space filled with sand is closed with a clay layer (cork) 50 ÷ 60 mm thick, using a solution of 5d.

Cleaning chamber installation

After mounting the drum, you need to install a cleaning chamber. Installing the box is not difficult - for this, a layer of solution 5d is applied to the transition channel and the hole in the drum, as well as to the side and bottom of the box, which has a thickness of 3 ÷ 4 mm. The box is put in place, and the transition channel window (2e) is inserted into the prepared opening of the drum and is well pressed and pressed down. The solution that comes out on the sides is immediately smeared. The entrance of the cleaning chamber to the drum must be well sealed, therefore, if there are gaps left, they must be sealed well.

Laying the thermal insulation layer

Formwork for level G

Further, a formwork is installed along the outer contour of the bed, just as in the manufacture of level A. The height of this level G must be displayed, focusing on the hole for connecting the “hog”. Above the upper edge of the hole, the level should be raised by about 80÷100 mm.

Formwork filling

The next step is filling the formwork with adobe mortar (5a) to the bottom edge of the hole prepared for the installation of the "hog" in the cleaning chamber one side, and at the end of the bed - to the lower edge of the outlet for the chimney.

The mixture is laid out and leveled by hand, while making sure that the mass is as close as possible to the previous layer. Thus, from the cleaning chamber to the chimney outlet rise is formed for pipes "hog", the height difference of which should be 15 ÷ 30 mm. This design is necessary so that the couch warms up evenly.

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Installation of a corrugated pipe

The next step is to stretch the corrugated pipe over the entire length of the bed. One end is connected to the cleaning chamber, inserted into the hole to a depth of 20÷25 mm and flaring inside the chamber with a flathead screwdriver through the cleaning door. Then the entrance of the pipe to the ash pan is coated with a solution of 5d, and the beginning of the pipe 150 ÷ 200 mm is coated with adobe. This will fix the rub well in the desired position and prevent it from slipping out of the hole during further work.

After that, the pipe in the formwork is laid in the form of a coil, but it must always be at a distance of about 100 mm from the edges of the formwork and the wall. During the laying process, the pipe is pressed into the adobe layer laid under it. Having laid the pipe along its entire length, its second end is fixed on a clay solution in the outlet chimney.

After that, the entire "hog" is plastered with adobe mortar, which must be well compacted, especially between the bends of the pipe, so that no voids form in it. After the adobe mass fills the space flush with the top of the corrugated pipe, a more liquid solution of adobe is poured into the formwork, and at the end the surface is smoothed out by a rule that is carried out along the walls of the formwork, which act as beacons ..

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Cover installation

After that, the covers of the cleaning chamber and the drum are fixed with bolts. They need to be tightened tightly so that they press the gaskets installed inside.

Furnace drum coating

Further, the oven drum is coated with adobe by ⅔ from the bottom of the body. The upper part of the drum is left free from the adobe layer. Thermal insulation is applied with a thickness of at least 100 ÷ 120 mm, and the configuration of the coating is chosen by the master himself.

Furnace finish

After two or two and a half weeks, the adobe layer should dry out and the installed formwork can be removed. Then, if necessary, the right corners of the structure are rounded. In addition, the drum is covered with heat-resistant enamel that can withstand temperatures up to 450÷750 degrees. The adobe surface of the couch is covered with acrylic varnish in two layers, each of which should dry well. The varnish will hold the surface material together, preventing it from dusting, protect the adobe from moisture and give the glazed clay the aesthetics.

If desired, a wooden flooring made of thin boards can be laid on the surface of the couch - it is quite often made removable. The side parts of the couch are sometimes trimmed with drywall or lined with stone. Decorative finishing is carried out to the taste of the owner of the house.

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Carrying out a furnace test

A dry oven must be tested. To do this, it is necessary to warm up the structure by laying light fuel in the form of paper in the blower and replenishing it during the combustion process. When heat is felt on the surface of the bed, you can put the main fuel into the combustion chamber. When the stove starts to hum, the blower closes until the sound changes to a “whisper”.

In conclusion, it must be said that the rocket stove can also be made of brick or stone - it all depends on the financial capabilities and creative abilities of the master. The main thing that can attract in this design Save so as not to lose!

In order for the jet furnace to work efficiently, the following rules must be observed during the installation of the structure:

The chimney must be at least twice as long as the horizontal or sloped section.
The fuel compartment must be the same length as the horizontal section. Usually the firebox is installed at an angle of 45 °, although there are designs with an angle of 90 °. But they are less convenient in terms of fuel loading.
The cross section of the chimney should not be smaller than the fuel compartment itself.

Device

Robinson factory camping stoves are made from a profile pipe with a cross section of 150 × 100 mm. Homemade designs are made the same size. In this case, the bunker is made of a profile pipe, and the chimney is made of a round one. In order for there to be normal draft, the chimney pipe must have a diameter not less than the cross section of the firebox.

For such a fuel compartment, a chimney no longer than 90 cm is allowed. But such dimensions make the unit inconvenient for transportation, so it is better to limit yourself to a minimum of 60 cm.

For the legs, a steel bar is taken. They are threaded, making the supports easy to install and remove. However, after repeated use of the jet stove, it is pretty smoky, so the process of screwing the legs is not very pleasant. However, other options are also common, where a steel sheet is used to make the stand or non-removable legs are installed. But this makes the design more overall and inconvenient during transportation.

Robinson factory ovens there is no air supply to the combustion zone, and they do not have an adjustable cover that changes the air supply. This point can be corrected in homemade ovens. A plate is welded inside the fuel hopper, at the bottom of which there is a grate. Fuel is placed on the flat element. Air enters the combustion zone through the grate, and a damper can be installed at the top of the firebox, with which the air supply will be regulated. It is made somewhat smaller than the firebox and should not completely block the hole, otherwise the air will stop flowing into the compartment and the fire will die out.

This design of the reactive furnace provides a number of advantages:

a small amount of solid fuel allows you to bring water to a boil in a short time, heat up food or cook simple dishes;
Robinson is not afraid of the wind, because the fire does not die out;
the jet furnace is easy to install;
the device does not smoke or smoke;
factory models are made of high-quality metal and covered with heat-resistant paint that can withstand high temperatures;
fuel does not burn out too quickly;
the device allows you to dry firewood;
the design is stable and easy to use;
the rocket oven heats up pretty quickly;
the maximum surface temperature reaches 900 °C;
thick steel (3.5 mm) ensures the durability of the device.

The price of the factory model is approximately 5 thousand rubles. But you can save money by making such a unit with your own hands. This task is feasible if you have certain skills.

Making a Robinson oven

The simple design of the device allows you to make a rocket stove at home. The whole procedure will take only a few hours. Materials for work are easy to find, besides, they need a little. The do-it-yourself unit is compact in size and easy to use.

The camping rocket stove is equipped with an important detail that greatly facilitates the maintenance of the unit. it metal plate with grating located at the bottom of the firebox. As a rule, it is made retractable, which allows you to remove the grate, put firewood on it and install it back. A similar plate also serves as a stand for long chips. In addition, with the grate removed, it is easier to clean the fuel compartment.

To make a jet furnace with your own hands, you must use the following materials :

two square pipes 150 × 150 × 3 mm: one is 45 cm long, the second is 30 cm;
4 steel strips 300×50×3 mm;
2 steel strips 140×50×3 mm;
metal grate 300 × 140 mm (it can be made from a rod of the same material with a diameter of 3-5 mm and a length of 2.5 m).

The manufacturing technology of the Robinson camp stove includes the following operations:

Do-it-yourself Robinson factory model

Making a rocket furnace similar to the one produced in factories is not a difficult task. There are not so many structural elements in this model:

As for the dish rack, its configuration is not of fundamental importance for the operation of the device. Therefore, this element can be done in a different way. At the same time, it is important to observe the rule according to which the stand should not block the chimney opening, so as not to disturb the draft.

In the model under consideration, 3 rings are cut in half and welded to a metal rod.

A similar design is more complicated than the previous one in that the duct is rectangular in cross section, and the chimney is round. Therefore, it is important to correctly perform operations to connect two parts into one device. Generally production technology is as follows:

It all starts with the manufacture of a plate with a grate that will divide the bunker into two parts. To do this, pieces of reinforcement are welded to a flat element in increments of 10 mm.
The resulting part must be welded to the rear and side walls of the hopper. The distance from the lower edge to the grating plate should be 30-35 mm. The part must be attached with a welding machine parallel to the bottom edge.
Then you need to carefully weld the joints of the walls together.
The bottom is attached to the resulting structure, and nuts are attached to it.
The top plate is welded to the back and side walls.
A cut is marked on the pipe at an angle of 30 °. The unnecessary part is cut off.
The end, which has acquired the shape of an oval, must be attached to the upper section of the bunker. In this case, the pipe is placed in the lowest part of the upper plate and equidistant from the side walls. This element is circled with a marker, a hole is cut out according to the markup. To do this, you can use a welding machine or a device for cutting metal.
Then a pipe must be attached to the resulting hole. A stand is installed on top of it, and the legs are screwed into the nuts. Now the rocket oven can be tested. After that, it is covered with heat-resistant paint.

Production of a modernized Robinson furnace

The model described in the previous section can be improved with a door that is installed on the fuel tank. But if you make a hinged sash, it will simply lean up, which will not allow you to adjust the traction. Such a part can only be in the “closed” or “open” position. It will be much more efficient to use a damper that moves vertically or horizontally. To install it, small corners of 10 × 10 mm or 15 × 15 mm must be welded on the bunker.

In addition, the following options for upgrading the furnace are noted:

the fuel bunker can be made of thicker steel, for example 5 mm;
replace the round chimney with a square one;
use a different design for the stand: as an option, take corners, balls or other elements that are at hand;
change the stand for a camping stove-rocket, for which a metal plate and a piece of reinforcement for making a leg can be used.

To make an upgraded oven, you will need the following materials:

Square pipe with a section of 160 × 160 mm and a length of 400 mm. A firebox will be made from it.
Square pipe with a section of 120 × 120 mm and a length of 600 mm. It is needed to make a chimney.
A five-millimeter sheet of steel and a piece of reinforcement with a diameter of 7-8 mm. Of these, an element will be made that separates the fuel compartment and the blower channel. The size of the part should be 300 × 155 mm.
Steel sheet 350×180 mm. Such material is necessary for the manufacture of the oven stand.
Steel sheet 160×100 mm in size.

The production technology of this model of a camping stove does not fundamentally differ from the creation of similar structures:

A metal plate with a grate must be welded to the walls of the bunker.
Then the back of the tank is attached, and the chimney is on top.
When the whole structure is ready, a metal stand is welded to it from below, and an additional support is made from a piece of reinforcement. For it, you can also use the part of the vertical pipe that remains after cutting.
Pieces of corners are welded on top of the vertical pipe, which will form a stand for dishes. Its height should be 40-50 mm.
The opening in the fuel tank must be closed with a hinged door or a damper inserted into the corners.
The finished product can be tested. If everything went well, the welds are cleaned, and the jet furnace is covered with heat-resistant paint. This will not only give the product a more attractive appearance, but also protect the metal from corrosion.

Outcome

It can be concluded that any of the proposed models is quite easy to make at home. Finding the necessary materials is not difficult. The work itself is not very difficult for someone who has used a welding machine more than once and has some experience working with metal. It will take only a few hours to make a rocket furnace. And the resulting product will be a useful item for lovers of outdoor activities outside the city.

In addition, such a rocket stove will allow you to heat a small summer cottage and will be a good alternative to a full-fledged heating system. The principle of operation of the Robinson jet furnace allows you to significantly save on fuel.

Let's say right away: a rocket stove is a simple and convenient wood-fueled heating and cooking device with good, but not exceptional parameters. Its popularity is explained not only by the catchy name, but more so by the fact that it can be made with your own hands and not by a stove-maker or even a bricklayer; if necessary - literally in 15-20 minutes.

And also by the fact that, with a little more work, you can get an excellent stove bench in the house without resorting to the construction of a complex, expensive and cumbersome Russian or bell-type stove. Moreover, the very principle of the device of the furnace-rocket gives great freedom to design and the manifestation of creative abilities.

Rocket stove - wood-fired device

But perhaps more remarkable is the "jet furnace" by the huge number of associated, at times completely absurd inventions. Here, for example, are a few pearls snatched at random:

"The operating principle of the furnace is the same as that of the MIG-25 ramjet engine." Yes, the MIG-25 and its descendant MIG-31 did not sit down near the ramjet engine (ramjet), as they say, and did not sit down in the bushes. On the 25th and 31st there are bypass turbojet engines (turbojet engines), four of which then pulled the Tu-144 and still pull other cars. And any furnace with any jet engine (RD) is technical antipodes, see below.
"Reverse jet furnace". Is this a tail-first stove, or what?
“But how will she blow such a pipe?” A naturally aspirated stove does not blow into the chimney. On the contrary, the chimney pulls out of it, on natural draft. The higher the pipe, the better it pulls.
“The rocket stove is a combination of a Dutch bell-type stove (sic!) with a Russian stove bench.” Firstly, there is a contradiction in the definition: a Dutch oven is a channel oven, and any bell-type oven is anything but a Dutch oven. Secondly, the couch of the Russian stove warms up in a completely different way than the rocket stove.

Note: in fact, the rocket stove was nicknamed so because in the wrong firing mode (more on that later), it emits a loud whistling rumble. A properly tuned rocket stove whispers or rustles.

These and similar inconsistencies, of course, are confusing and prevent us from making a rocket furnace properly. So let's figure out what is true about the rocket stove, and how to use this truth correctly so that this really good stove shows all its advantages.

Furnace or rocket?

For complete clarity, we still need to figure out why a stove cannot be a rocket, and a rocket cannot be a stove. Any RD is the same internal combustion engine, only the outflowing gases themselves act as pistons, connecting rods with a crank and transmission. In a piston internal combustion engine, already at the moment of combustion, the high temperature of the working fluid creates a large pressure that pushes the piston, and it already moves the entire mechanics. The movement of the piston is active, the working fluid pushes it to where it tends to expand itself.

When fuel is burned in the RD combustion chamber, the thermal potential energy of the working fluid is immediately converted into kinetic energy, like that of a load falling from a height: since the exit to the nozzle is open to the hot gases, they rush there. In RD, pressure plays a subordinate role and nowhere exceeds a few tens of atmospheres, this, for any conceivable nozzle cross section, is not enough to disperse a flashlight to 2.5M or put a satellite into orbit. According to the law of conservation of momentum (momentum), the aircraft with RD at the same time receives a push in the opposite direction (recoil momentum), this is jet thrust, i.e. thrust from recoil, reactions. In a turbofan engine, the second circuit creates an invisible air shell around the jet. As a result, the recoil momentum is, as it were, contracted in the direction of the thrust vector, so the turbofan is much more economical than a simple turbofan.

In the furnace, there is no conversion of types of energy into each other, therefore it is not an engine. The stove simply distributes potential thermal energy properly in space and time. From the point of view of the furnace, the ideal RD has an efficiency of 0%, because it just runs on fuel. From the point of view of a jet engine, the furnace has an efficiency = 0%, it only dissipates heat and does not pull at all. On the contrary, if the pressure in the chimney rises to or above atmospheric (and without this, where will the jet thrust or active force come from?), The stove will at least smoke, or even poison the residents or start a fire. Draft in the chimney without pressurization, i.e. without the expenditure of energy from the side, it is provided due to the temperature difference along its height. Potential energy here, again, is not converted into any other.

Note: in a rocket propellant rocket engine, fuel and oxidizer are fed into the combustion chamber from tanks, or they are immediately filled into it if the rocket engine is on solid fuel. In a turbojet engine (TRD), the oxidizing agent - atmospheric air - is injected into the combustion chamber by a compressor driven by a turbine in the exhaust gas flow, the rotation of which consumes a certain fraction of the energy of the jet stream. In a turboprop engine (TVD), the turbine is designed so that it takes 80-90% of the power of the jet, which is transmitted to the propeller and compressor. In a ramjet engine (ramjet), air is supplied to the combustion chamber by hypersonic velocity pressure. A lot of experiments were carried out in the ramjet, but there were no production aircraft with it, there is not and is not expected, the ramjet is painfully capricious and unreliable.

Can or not can?

Among the myths about the rocket stove, there are not entirely absurd, and even somewhat justified. One of these misconceptions is the identification of the "racquet" with the Chinese kan.

As a child, the author had a chance to visit the Amur region, in the region of Blagoveshchensk, in winter. There were a lot of Chinese there in the villages even then, who were scrambled in all directions from the cultural revolution of the Great Chairman Mao and his completely frostbitten hungweibins.

Winter in those parts is not Moscow, frost at -40 is a common thing. And what struck and aroused interest in stoves in general was how Chinese fanzes were heated by kans. In Russian villages, firewood is transported by carts, smoke is a pillar from the chimneys. And all the same, in the log hut, not in a children's girth, by morning the corners were frosted over from the inside. And the fanza is built like a country house (see the figure), the windows are covered with a fish bladder or even rice paper, bunches of chips or twigs are placed in the kan, but the room is always warm.

However, there are no subtle heat engineering tricks in the canal. This is an ordinary, only small, stove with a lower exit to the chimney, and most of the chimney itself is a long horizontal channel, a hog, on which a stove bench is arranged. The chimney, for the sake of fire safety, is outside the building.

The effectiveness of the kan is determined primarily by the thermal curtain it creates: the couch goes around, if not the entire perimeter from the inside, except for the door, then 3 walls for sure. Which once again confirms: the design and parameters of the furnace must be linked to those of the heated room.

Note: The Korean ondol oven operates on the principle of a warm floor - a very low stove bench occupies almost the entire area of the room.

Secondly, in the very cold, the Kans were drowned with argal - dried droppings of ruminants, domestic and wild. Its calorific value is quite high, but argal burns slowly. In fact, an argal fire is already a long-burning stove.

It is not in the Russian custom to stick twigs into the oven every now and then, and our peasants abhorred cooking on animal feces. But travelers of the past highly valued argal as a fuel, collected it along the way and carried a supply with them, diligently protecting it from getting wet. N. M. Przhevalsky, in one of his letters, argued that without the argal, he could not have carried out his expeditions in Central Asia without loss. And for the British, who were disdainful of the argal, 1/3-1/4 of the personnel of the detachments returned to the base. True, he was recruited from sepoys, Indian soldiers in the English service, and pandits - spies recruited from the local population. One way or another, but the highlight of the rocket stove is not at all in the couch on the hog. To get to it, you will have to learn to think in an American way: all the primary sources on the rocket furnace are from there, and utter speculation is generated only and only by misunderstanding.

How to deal with rockets?

In our view of things, the original technical documentation of rocket furnaces should be studied with caution, but not at all because of inches-millimeters, liters-gallons and the subtleties of American technical jargon. Although they also mean a lot.

Note: A textbook example is "Naked conductor runs under the carriage". Literary translation - a naked conductor runs under the car. And in the original article from Petroleum Engineer, it meant "Bare wire runs under the crane trolley."

The rocket stove was invented by members of survival societies - people with a peculiar way of thinking, even by American standards. In addition, they were not bound by any standards and norms, but, like all Americans, they always automatically converted everything into money, taking into account their own benefit; a person with a different worldview in America simply does not get along. And instinctive self-interest inevitably gives rise to egocentrism. He by no means excludes good deeds, but not out of a spiritual outburst, but out of the calculation of dividends. Not in this life, but in that one.

Note: How much the average inhabitant of the greatest empire in history is afraid of everything can only be understood by talking with them long enough. And sociopsychologists go out of their way there, convincing that living, languishing in fear, is normal and even cool. The rationale is clear: intimidated biomass is easily predictable and manageable.

Without heating and cooking, of course, you will not survive. What is an oven for? For the time being, for the time being, the survivors were content with camping stoves. But then, according to the Americans themselves, in 1985-86. they were greatly impressed by two films that were released with a short interval and triumphantly went around all the screens of the world: the Soviet science fiction parody of the entire human race "Kin-dza-dza" and Hollywood's "The Day After", about the global nuclear war.

The survivors realized that after the nuclear winter there would be no extreme romance, but there would be the planet Plyuk in the Kin-dza-dza galaxy. It will be necessary to be content with the newly appeared plukans "ka-tse" in small quantities, bad, expensive and difficult to access. Yes, all of a sudden someone hasn’t watched “Kin-dza-dza” - like a match in Plukansky, a measure of wealth, prestige and power. It was necessary to invent your own furnace, none of the existing ones is designed for a post-nuclear spit.

Americans are very often endowed with a sharp mind, but a deep one is found as the rarest exception. A completely normal and with an IQ above the average, a US citizen may sincerely not understand how it doesn’t reach another that he himself has already “caught up” and how someone else may not like what suits him.

If an American has already grasped the essence of an idea, then he brings the product to its possible perfection - what if there is a buyer, you can’t sell raw iron. But the technical documentation, which looks beautiful and neat, can be drawn up in fact extremely carelessly, or even deliberately distorted. And what is it, this is my know-how. Maybe I'll sell it to someone. Whether there will be a plus, or not, but for now the know-how is worth the money. In America, such an attitude to business is considered quite honest and worthy, but there a clinical alcoholic at work will never miss a stopper and will not drag a couple of bolts home to the household. On that, in general, the whole of America stands.

And the Russian breadth of the soul is also a double-edged sword. Most often, our master simply understands from a sketch how this thing works, but in the details it turns out to be careless and overly trusting in the source code: how is it for a crafty bro to deceive his own. If you don't have something, then you don't need it. It seems clear how everything is spinning there - already my hands itch. And there, perhaps, until it comes to a hammer, chisel and related literature, still count and count. Moreover, important points can be omitted, veiled or deliberately wrong.

Note: an American acquaintance once asked the author of this article - how did we, the really stupid ones, elect the very smart Reagan as president? And you, really smart, tolerate a slobbering senile with dyed eyebrows in the Kremlin? True, then in America no one in a bad dream would have dreamed that in the next century a black citizen with a Muslim name would settle in the Oval Office, and his first lady would dig a garden near the White House and begin to grow turnips there. Times is changing, as Bob Dylan once sang for a completely different reason ...

Sources of misunderstanding

There is such a thing in technology - the square-cube law. Simply put, when something changes in size, its surface area changes squarely, and its volume changes cubed. Most often, this means that changing the overall dimensions of the product according to the principle of geometric similarity, i.e. You can't just keep the proportions. With regard to solid fuel stoves, the square-cube law is doubly valid, because fuel is also subject to it: it releases heat from the surface, and its reserve is contained in the volume.

Note: a consequence of the square-cube law - any specific design of the furnace has a certain allowable fork of its size and power, within which the specified parameters are provided.

Why, for example, is it impossible to make a potbelly stove the size of a refrigerator and with a power of about 50-60 kilowatts that way? Because the potbelly stove, in order for it to somehow warm, must itself be heated inside to at least 400-450 degrees. And in order to warm up the volume of the refrigerator to such a temperature at a given heat transfer, firewood or coal needs as much as it does not fit in it. There will also be no sense from a mini-potbelly stove: the heat will leave through the outer surface of the furnace, which has grown relative to its volume, and the fuel will not give it away more than it can.

The square-cube law acts triple on the rocket furnace, because she is "licked" in an American professional way. With our kondachka, it is better to stay away from her. Here, for example, here in Fig. American development, which, judging by its demand, many of our craftsmen take as a prototype.

The original blueprint for the mobile rocket oven

With the fact that the exact grade of refractory clay (fire clay) is not indicated here, ours will sort it out. But, to be honest, who noticed that, judging by the absence of an external chimney and the presence of transportation holes (carrying pipe), this stove is mobile with an open firebox? And most importantly, the fact that a 20-gallon keg with a diameter of 17 inches (431 mm with change) went to her drum?

Judging by the structures from Runet, no one at all. They take this thing and adjust it according to the principle of geometric similarity to a domestic 200-liter barrel with a diameter of 590 mm on the outside. Many guess to arrange a blower, but the bunker is left open. Are the exact proportions of vermiculite with perlite for lining the riser and forming the furnace body (core) not indicated? We make the lining homogeneous, although it will be clear from what follows that it should consist of insulating and accumulating parts. As a result, the furnace roars, the fuel eats only dry, and a lot, and even before the end of the season, it overgrows with burning inside.

How was the rocket oven born?

So, already without fiction with futurology, the survivors needed a stove to heat the house, operating with high efficiency on low-quality random wood fuel: wet wood chips, twigs, bark. Which, moreover, will need to be reloaded without stopping the furnace. And most likely it will not be possible to dry in a firewood shed. Heat dissipation after heating needs at least 6 hours to get enough sleep; getting pissed off in a dream on Pluka is no better than in America. Additional conditions: the design of the furnace should not contain complex metal products, non-metallic materials and components that are required for the manufacture of production equipment, and the furnace itself must be available for construction by an unskilled worker without the use of power tools and complex technologies. Of course, no supercharging, electronics and other energy dependencies.

They immediately took a couch from the kan, but what about the fuel? For a bell-type furnace, it requires high quality. Long-burning furnaces work even on sawdust, but only dry, and do not allow shutdown with additional loading. Nevertheless, they were taken as a basis, they were very attracted by the high efficiency achieved by simple methods. But in an attempt to make the "long stoves" work on bad fuel, another circumstance became clear.

What is wood gas?

The high efficiency of long-burning furnaces is achieved largely due to the afterburning of pyrolysis gases. Pyrolysis is the thermal decomposition of solid fuel into volatile combustible substances. As it turned out (and the survivors have their own research centers with highly qualified specialists), the pyrolysis of wood fuel, especially wet fuel, continues for a long time in the gas phase, i.e. The pyrolysis gases that have just been released from the wood still require quite a lot of heat to form a mixture that can burn out completely. This mixture was called wood gas, woodgas.

Note: in Runet, woodgas has created more confusion, because in American vernacular, gas can mean any fuel, cf. e.g. gas station - gas station, gas station. When translating primary sources without knowing the American technical, it turned out that woodgas is just wood fuel.

Before that, no one saw wood gas: in conventional furnaces, it is formed immediately in the furnace, due to the excess energy of fiery combustion. The designers of long-burning stoves came to the conclusion that the primary air must be heated, and the exhaust gases should be retained in a significant volume over a large mass of fuel, simply by trial and error, so they overlooked the wood gas.

It turned out not so when firing with bundles of twigs: here the primary pyrolysis gases were immediately dragged into the chimney. Wood gas could have formed in it at some distance from the furnace, but the primary mixture had cooled by that time, pyrolysis stopped, and heavy radicals from the gas settled on the walls of the chimney like soot. Which quickly tightened the channel completely; amateurs building rocket furnaces at random are well familiar with this phenomenon. But the survivors eventually figured out what was going on and made the right oven anyway.

Who are you, the Rocket Stove?

There is an unspoken rule in technology: if it seems that it is impossible to create a device according to the given requirements, then read, smart guy, school textbooks. That is, go to the basics. In this case, to the basics of thermodynamics. Survivors do not suffer from sick pride, they turned to the basics. And they found the main principle of operation of their furnace, which has no analogues in others: slow adiabatic afterburning of pyrolysis gases in a weak flow. In long-burning furnaces, afterburning is equilibrium isothermal, requiring a large buffer volume, subject to the square-cube law, and the energy reserve in it. In pyrolysis gases in the afterburner expand almost adiabatically, but practically into free volume. And now - learn to think in an American way.

How does a rocket oven work?

The scheme of the final fruit of the labors of the survivors is presented on the left side of fig. Fuel is loaded vertically into the bunker (Fuel Magazine) and burns, gradually settling down. Air enters the combustion zone through the blower (Air Intake). The blower must provide an excess of air so that it is enough for afterburning. But not excessive, so that the cold air does not cool the primary mixture. With vertical loading of fuel and a blind cover of the bunker, the flame itself acts as a regulator, however, not very effective: when it flares up too much, it pushes the air out.

The device of rocket furnaces

Further things already non-trivial begin. We need to warm up, and with good efficiency, a large oven. The law of the square-cube does not allow: the meager heat will immediately dissipate so much that the pyrolysis will not reach the end, and the thermal gradient from the inside to the outside will not be enough to transfer heat into the room; everything will whistle through the trumpet. This law is harmful, you can't break it in the forehead. Okay, let's see in the basics, if there is anything there that is not subject to him.

But how, there is. That same adiabatic process, i.e. thermodynamic without heat exchange with the environment. There is no heat exchange - the squares are resting, and the cubes can be reduced even to a thimble, even to a skyscraper.

Imagine a completely isolated volume of gas. Let's say it releases energy. Then the temperature and pressure will begin to rise until the energy release stops, and will freeze at a new level. Great, we burned the fuel completely, hot flue gases can be released into a heat exchanger or heat accumulator. But how to do it without technical difficulties? And most importantly - how, without violating the adiabat, to supply air for afterburning?

And we will make the adiabatic process non-equilibrium. How? Let the primary gases immediately from the combustion source go into a pipe covered with high-quality insulation with a low intrinsic heat capacity (Insulation). Let's call this pipe for ourselves a flame or a burning tunnel (Burn Tunnel), but we will not sign it (know-how! You can’t catch up - give money for consulting drawings! Without theory, of course. Who sells the fixed capital at retail.) On the diagram, so that not accused of "opacity", denoted by the flame.

Along the length of the flame tube, the adiabatic index changes (this is a non-equilibrium process): the temperature will first drop slightly (wood gas is formed), then it will increase sharply, the gas will burn out. It is possible to release it into the accumulator, but we forgot - what will pull gases through the flame tube? Supercharging means energy dependence, and there will be no exact adiabat, but something mixed with an isobar, i.e. the efficiency drops.

Then we will lengthen the pipe by half, keeping the insulation so that the heat does not go in vain. We bend the “idle” half up, making the insulation weaker on it; how to keep the heat seeping through it, we will think a little later. In a vertical pipe, a temperature difference will appear along the height, which means thrust. And good: the thrust force depends on the temperature difference, and with an average in the flame tube of about 1000 degrees, it is not difficult to achieve a difference of 100 at a height of about 1 m. So, while we have made a small economical potbelly stove, now we need to think about how to use it warmly.

Yes, it does not interfere with additional encryption. If we call the vertical part of the flame tube the primary or internal chimney (Primary or Internal Vent), then they will guess the main idea, we are not the smartest in the world. Well... let's call the primary chimney the most common technical term for vertical pipes with upward current - the riser (riser). Purely American: correct and incomprehensible.

Now let's recall the heat transfer after heating. Those. we need a cheap, always available and very capacious heat storage. There is nothing to invent here, the adobe (Thermal Mass) was invented by the primitives. But it is not fire resistant, it does not hold more than 250 degrees, and we have about 900 at the mouth of the riser.

It is not difficult to convert high-potential heat into medium-potential heat without loss: you need to give the gas the opportunity to expand in an isolated volume. But, if the expansion is left adiabatic, then the volume will need to be too large. And that means - material and labor intensive.

I had to bow to the basics again: immediately after leaving the riser, let the gases expand at constant pressure, isobarically. This requires heat to be removed to the outside, about 5-10% of the heat output, but it will not disappear and will even be useful for quickly warming up the room during the morning fire. And further along the course of gases - isochoric cooling (in a constant volume); Thus, almost all the heat will go into the battery.

How to do it technically? We cover the riser with a thin-walled iron drum (Steel Drum), which will also stop heat loss from the riser. The “drum” turns out to be a bit high (the riser sticks out a lot), but it doesn’t matter: we will cover it with the same adobe for 2/3 of the height. We attach a stove bench with an airtight chimney (Airtight Duct), an external chimney (Exhaust Vent), and the stove is almost ready.

Note: the riser and the drum that covers it look like a furnace hood over an elongated hail. But the thermodynamics here, as we see, is quite different. It is useless to try to improve the bell-type stove by building on a high loft - only the extra material and work will go away, and the stove will not get any better.

It remains to solve the problem of cleaning the channel in the couch. For this, the Chinese have to break the kan from time to time and remake it, but we are not in the 1st century. BC. we live when kan was invented. We will arrange a secondary ash pan (Secondary Airtight Ash Pit) with a sealed cleaning door immediately after the drum. Due to the sharp expansion and cooling of flue gases in it, everything in them that did not burn out immediately condenses and settles. The cleanliness of the external chimney is guaranteed by this for years.

Note: the secondary cleaning will have to be opened once or twice a year, so you don’t have to fool around with the latches. We will simply make a cover from a metal sheet on screws with a mineral cardboard gasket.

small rocket

The next task of the designers was to create on the same principle a small continuous combustion oven for cooking in the warm season. In the heating season, the drum cover (Optional Cooking Surface) of a large oven is suitable for cooking, it heats up to about 400 degrees. The small rocket stove was supposed to be portable, but it was permissible to make it with an open firebox, because. when warm, you can cook outdoors or under a canopy.

Here the designers took revenge on the square-cube law, forcing it to work for themselves: they combined the fuel tank with the blower, see Fig. at the beginning of the section on the right. It is impossible to do this in a large furnace, fine adjustment of the furnace mode as the fuel settles (see below) will be impossible.

Here, the volume of incoming primary air (Primary Air) turns out to be small relative to the heat release area, and the air can no longer cool the primary mixture until pyrolysis stops. Its supply is regulated by a slot in the cover of the hopper (Cover Lid). The 45-degree hopper optimizes the oven's auto-adjustment for standard cooking routines, but it's harder to make.

Secondary air for afterburning wood gas in a small oven enters through additional holes in the mouth of the riser or simply flows under the burner if there is a cooking vessel on it. If a small furnace is close to the limit size (about 450 mm in diameter), then an optional secondary woodgas frame may be needed for complete afterburning.

Note: It is not possible to supply secondary air to the mouth of the riser of a large furnace through the holes in the drum (which would increase the efficiency of the furnace). Although the pressure in the entire gas-smoke path is lower than atmospheric pressure, as it should be in the furnace, flue gases will be emitted into the room due to strong turbulence. Here their kinetic energy, harmful to the furnace, affects; this, perhaps, is the only thing that makes a rocket stove related to a jet engine.

The small rocket stove has revolutionized the class of camping stoves, especially camping stoves. A wood chip stove (a Bond stove in the West) will help to cook a stew or wait out a snowstorm in a one-two-man tent, but it will not save a group caught on a spring campaign by a belated bad weather. A small rocket furnace is only a little larger, it can be quickly made from nowhere, but is capable of developing power up to 7-8 kW. However, we will talk about furnace-rockets from anything we will talk further.

Also, the small rocket oven has spawned many improvements. For example, Gabriel Apostol provided it with a separate blower and a wide bunker. The result was a stove suitable for the device of a compact and rather powerful water heater, see the video below. The large rocket furnace was also modified, we will talk about this a little at the end, but for now let's dwell on more significant things.

Video: a water heater based on a rocket stove designed by Gabriel Apostol

How to fire a rocket?

A rocket furnace with long-burning furnaces has a common property: they need to be launched only on a warm pipe. For a small one, this is not essential, but a large one on a cold chimney will only burn fuel in vain. Therefore, a large rocket furnace, before loading regular fuel into the bunker after a long break in the furnace and kindling, must be accelerated - fired with paper, straw, dry shavings, etc., they are placed in an open blower. The end of acceleration is judged by a change in the tone of the hum of the furnace or its subsidence. Then you can load fuel into the bunker, and its ignition will occur by itself from the accelerating fuel.

The rocket furnace, unfortunately, does not apply to furnaces that are completely self-adjusting to the quality of the fuel and external conditions. At the beginning of regular fuel combustion, the blower door or the bunker cover in the small furnace is fully opened. When the stove hums strongly, cover it "to a whisper." Further, in the process of burning, it is necessary to gradually cover the access of air, guided by the sound of the furnace. Suddenly, the air damper slammed shut for 3-5 minutes - it's okay, if you open it, the stove will flare up again.

Why such difficulties? In the process of burning the fuel, the flow of air into the combustion zone increases. When there's too much air, the furnace roars, but don't get excited: the excess air now cools the primary gas mixture, and the sound is amplified as the steady swirl in the riser clumps into a clump. Pyrolysis in the gas phase is interrupted, no wood gases are formed, the furnace consumes too much fuel, and carbon deposits from the soot cemented by bituminous particles are deposited in the riser. This, firstly, is a fire hazard, but most likely it will not come to a fire, the riser channel will quickly overgrow with soot completely. And how to clean it if you have a non-removable drum cover?

In a large furnace, a spontaneous change of regime occurs abruptly, when the top of the sticks drops to the bottom edge of the bunker, and in a small furnace, gradually, as the fuel mass settles. Since an experienced housewife does not leave her for a long time when cooking on the stove, the designers considered it possible, for the sake of compactness, to combine a bunker with a blower in it.

With a large oven, this trick will not work: a high riser pulls very strongly, and the air gap is needed so thin (and it also needs to be regulated) that it is impossible to achieve a stable furnace mode. It’s easier with a separate blower: the mass of fuel, rounded in section, is easier for air to flow around from the sides, a too-flamed flame pushes it there. The stove turns out to some extent self-regulating; however, within very small limits, so you still have to manipulate the blower door from time to time.

Note: for the sake of simplicity, it is impossible to make a bunker of a large furnace without a tight lid, as is often done. Due to the unregulated additional air flow through the fuel mass, it is unlikely that it will be possible to achieve a stable operation of the furnace.

Materials, dimensions and proportions, lining

Now let's see what a home-made rocket stove should be from the materials available to us. Here, too, we need to look back: not everything that is at hand in America is also with us, and vice versa.

Of what?

For a large stove with a bench, more or less reliable experimental data is available for products with a drum from a 55-gallon drum with a diameter of 24 inches. 55 gallons is 208-plus liters, and 24 inches is almost exactly 607mm, so our 200-litre is fine without additional conversion. Keeping the parameters of the furnace, the diameter of the drum can be halved, up to 300 mm, which makes it possible to make it from 400-450 mm tin buckets or a household gas cylinder.

Pipes of different sizes will go to the blower, bunker, firebox and riser, see below, round or shaped. So it will be possible to make an insulating lining of the furnace part from a mixture of equal parts of furnace clay and fireclay crushed stone, without resorting to brickwork; we will talk about the riser lining in more detail below. Combustion in the rocket furnace is weak, therefore the thermochemistry of gases is gentle and the thickness of the steel of all metal parts, except for the gas pipeline in the stove bench, is from 2 mm; the latter can be made from thin-walled metal corrugated, here the flue gases have already completely exhausted both in terms of chemistry and temperature.

For external coating, the best heat accumulator is adobe. Subject to the dimensions indicated below, the heat transfer of a rocket furnace in adobe after combustion can reach 12 hours or more. Other parts (doors, covers) are made of galvanized metal, aluminum, etc., with sealing gaskets made of mineral cardboard. Conventional oven fittings are not suitable enough, it is difficult to ensure their tightness, and a slotted rocket oven will not work properly.

Note: it is desirable to equip the rocket stove with a view in the external chimney. Although the gas view in the high riser seals the common smoke path tightly, strong winds outside can prematurely draw heat out of the couch.

Dimensions and proportions

The basic calculated values to which the rest are tied are the drum diameter D and its cross-sectional area along the inside S. Everything else, based on the size of the available iron, is determined as follows:

Drum height H - 1.5-2D.
Drum coating height - 2/3H; for the sake of design, the edge of the coating of the design can be made oblique curvilinear, then 2/3H must be maintained on average.
The thickness of the coating of the drum is 1/3D.
The cross-sectional area of the riser is 4.5-6.5% of S; it is better to stay within 5-6% of S.
The height of the riser - the larger the better, but the gap between its edge and the drum tire must be at least 70 mm; its minimum value is determined by the viscosity of the flue gases.
The length of the flame tube is equal to the height of the riser.
The cross-sectional area of the flame tube (fire pipe) is equal to that of the riser. It is better to make a fire pipe from a square corrugated pipe, so the furnace mode will be more stable.
The cross-sectional area of the blower is 0.5 from its own firebox and riser. A more stable furnace mode and its smooth adjustment will be provided by a rectangular corrugated pipe with sides 2: 1, laid flat.
The volume of the secondary ash pan is from 5% of the initial volume of the drum (excluding the volume of the riser) for a furnace from a barrel to 10% of it for a furnace from a cylinder. Interpolation for intermediate drum sizes is linear.
The cross-sectional area of the external chimney is 1.5-2S.
The thickness of the adobe cushion under the external chimney is 50-70 mm; if the channel is round, it is considered from its lower point. If the bench is on wooden floors, the pillow under the chimney can be halved.
The height of the bed coating above the external chimney is from 0.25D for a 600 mm drum to 0.5D for a 300 mm drum. It can be less, but then the heat transfer after heating will be shorter.
The height of the external chimney is from 4 m.
Permissible length of the flue in the couch - see next. sec.

The maximum thermal power of a barrel rocket furnace is approximately 25 kW, and a gas cylinder furnace is about 15 kW. Power adjustment - only by the size of the fuel load. By supplying air, the oven is put into operation, and nothing more!

Note: In the original survivalist ovens, the riser cross-section was taken as 10-15% S, based on very wet fuel. Then, in the same place, in America, rocket stoves with a stove bench for a bungalow appeared, designed for air-dry fuel and more economical. In them, the riser section is reduced to the recommended ones and here 5-6% S.

Riser lining

The efficiency of the rocket furnace largely depends on the thermal insulation of the riser. But American lining materials, alas, are not available to us. In terms of stocks of high-quality refractories, the United States has no equal, where they are considered strategic raw materials and are sold with caution even to proven allies.

Of our available materials for heat engineering, they can be replaced with light fireclay bricks of the ShL brand and ordinary self-digged river sand with a large admixture of alumina, correctly laid, see below. However, these materials are porous, in the oven they are quickly saturated with soot. Then the stove will roar with any air supply, with all the consequences. Therefore, we need to surround the riser lining with a metal shell, and be sure to cover the end of the lining with furnace clay.

Lining schemes for 3 types of furnaces are shown in fig. The bottom line here is that with a decrease in the size of the drum, the proportion of its direct heat transfer through the bottom and the unlined part increases according to the square-cube law. Therefore, while maintaining the desired thermal gradient in the riser, the lining capacity can be reduced. This makes it possible to correspondingly increase the relative cross section of the annular descent of the flue gases in the drum.

Riser lining schemes in rocket furnaces

What for? Firstly, the requirements for an external chimney are reduced, since the outer traction pulls better now. And since it pulls better, then the permissible length of the hog in the stove bench falls more slowly than the dimensions of the furnace. As a result, if a stove from a barrel warms up a bench with a pine forest up to 6 m long, then half the size from a cylinder is 4 m.

How to line with sand?

If the riser lining is fireclay, then the remaining cavities are simply covered with construction sand. River self-digging for lining entirely of sand does not need to be carefully prepared, it is enough to select large debris. But they pour it in layers, in 5-7 layers. Each layer is compacted and sprayed until a crust forms. Then the whole backfill is dried for a week, the upper edge is covered with clay, as already mentioned, and the construction of the furnace is continued.

balloon rocket

From the foregoing, it is clear that it is more profitable to make a rocket stove from a gas cylinder: less work, fewer unsightly parts in sight, and the stove heats up almost the same. A thermal curtain or underfloor heating in Siberian frost will heat a room of 50 square meters with a power of 10-12 kW. m or more, so here, too, a balloon rocket turns out to be more profitable, it is rarely necessary to launch a large barrel at full power with maximum efficiency.

Craftsmen, apparently, also understood this; at least some. For example, here in Fig. - drawings of a balloon furnace-rocket. On the right is the original; the author, it seems, was wisely versed in the initial developments and, in general, everything turned out right for him. On the left - the necessary improvements, taking into account the use of air-dry fuel and warming up the couch.

Drawings of a rocket stove from a gas cylinder

A fruitful idea is a separate supply of heated secondary air. The furnace will be more economical and the flame tube can be made shorter. The cross-sectional area of its air duct is about 10% of the riser cross-section. The furnace always works with the secondary fully open. First, the mode is set with a primary valve; finely adjust the hopper cover. At the end of the furnace, the furnace will roar, but here it is not so scary; the author of the design provides for a removable drum cover to clean the riser. She, of course, should be with a seal.

Rockets from anything

Canned

Scheme of a rocket furnace from cans

Tourists, hunters, and fishermen (many of them members of survival societies) soon converted the small rocket stove into a camping stove made from empty tins. It was possible to reduce the influence of the square-cube to a minimum by applying a horizontal fuel supply, see the diagram on the right. True, at the cost of some inconvenience: the sticks need to be pushed inward as they burn out. But the furnace mode began to hold iron. How? Due to the automatic redistribution of air flows through the blower and over / through the fuel. The power of a jar rocket furnace is in the range of 0.5-5 kW, depending on the size of the furnace, and is regulated by approximately three times the amount of fuel loading. The basic proportions are also simple:

The diameter of the combustion chamber (combustion chamber) is 60-120 mm.
The height of the combustion chamber is 3-5 of its diameters.
The cross section of the blower is 0.5 from its own combustion chamber.
The thickness of the thermal insulation layer is not less than the diameter of the combustion chamber.

These proportions are very approximate: changing them by half does not prevent the stove from working, and the efficiency in the campaign is not so important. If the insulation is made of wetted sandy loam, as described above, the joints of the parts can simply be smeared with clay (left pos. in the figure below). Then the stove, after 1-2 fires, will acquire strength, allowing it to be transported without any special precautions. But in general, any of the improvised non-combustible materials will do the insulation, next. two pos. A burner of any design must provide a free flow of air, 3rd pos. A rocket stove welded from a steel sheet (right pos.) with sand insulation is twice as light and more economical than a potbelly stove of the same power.

Compact Rocket Furnaces

brick

Brick rocket stove

We will not expand on large stationary rocket furnaces: in them all the initial thermodynamics goes to pieces, and they are deprived of one of the main advantages of the original furnace - ease of construction. We will talk a little about rocket stoves made of bricks, clay or stone fragments, which can be made in 5-20 minutes when there are no tins at hand.

Here, for example (see the video below), is a completely thermodynamically complete rocket stove of 16 bricks laid dry. The voice acting is English, but everything is clear without words. A similar one can be folded from fragments of bricks (see Fig.), Cobblestones, fashioned from clay. For 1 time, a stove made of greasy earth is enough. The profitability of all of them is not so hot, the height of the combustion chamber is small, but it’s enough for pilaf or urgently to warm up.

Video: 16 brick rocket oven (eng)

new material

Scheme of the Shirokov-Khramtsov furnace

Of domestic developments, the Shirokov-Khramtsov rocket furnace deserves attention (see the figure on the right). The authors, not caring about survival in a plus, used a modern material - heat-resistant concrete, adjusting all thermodynamics to it. The components of refractory concrete are not cheap; a concrete mixer is needed for mixing. But its thermal conductivity is much lower than that of most other refractories. The new rocket furnace became more stable, and it became possible to release some of the heat outside in the form of infrared radiation through heat-resistant glass. It turned out a rocket stove - a fireplace.

Do rockets fly in the bath?

Isn't a rocket stove suitable for a bath? It seems to be possible to arrange a heater on the drum cover. Or flowing instead of a couch.

Unfortunately, the rocket oven is not suitable for a bath. To get light steam, the sauna stove must immediately warm up the walls with thermal (IR) radiation, and immediately, or a little later, the air, by convection. To do this, the oven must be a compact IR source and a convection center. The convection from the rocket furnace is distributed, and it gives little IR at all, the very principle of its design eliminates significant radiation losses.

In conclusion: rocket stove-makers

In successful designs of rocket furnaces, there is still more intuition than precise calculation. And therefore - good luck to you too! - a rocket oven is a fertile field for craftsmen with a creative streak.published

Topics dedicated to boilers, home-made stoves and heating equipment are always popular on FORUMHOUSE. This is not surprising. Indeed, due to the constant rise in energy prices, the difficulties and high cost of connecting to the main gas, many are thinking about finding an alternative to "blue fuel".

Despite the large selection of ready-made factory products, our enthusiasts create their own designs of heating systems. Of particular interest is a solid fuel boiler built by the user of our portal with the nickname Perelesnik. He attracted increased attention, because. its work is based on the principle of operation of a rocket furnace. In this material we will talk about the main stages of the development of the boiler, preceding its construction.

How it all started

Before moving on to the technical features of the boiler, it is worth focusing on the background of its construction.

Perelesnik FOUMHOUSE User

Gas is brought into my house, but from time to time I thought about switching to solid fuel. The only thing that stopped us was that gas heating was profitable, and the transition to firewood turned out to be unprofitable. I heated the house with an electrode boiler with a power of 7 kW, working in conjunction with an air conditioner, which was operated “for heating”. In severe frosts, the house was additionally heated by a gas-fired boiler. And the price of gas has gone up...

It was the increase in the price of gas that became the event that led to the development of the rocket boiler.

Before you go and immediately buy "something" called "solid fuel boiler", Perelesnik began to study the subject. He got acquainted with the list of equipment offered in stores, looked at how the neighbors' boilers work, understood what the most common problems arise, and studied reviews on the Internet.

After brainstorming, a list of requirements appeared that the device must meet - in terms of Perelesnik:

Possibility of stable operation at power from 2 to 20 kW. This is due to the peculiarities of the climate in the region where the forum member lives. In winter, the temperature can stay around 0°C for a month, and then drop sharply for a week to -25…30°C. In the autumn-spring period the temperature is within +5…+10°C. Because the house also needs to be heated in the off-season, but the maximum power is not required from the boiler, a “flexibly” configurable device is needed.
The boiler must be "omnivorous", i.e. everything that can burn - firewood, fuel briquettes, coal, waste, etc., including wet fuel, should burn in the furnace.
The design of the boiler should provide for laying logs with a diameter of up to 20 cm. This will reduce the need for chopping firewood.
Must work from night to morning on one bookmark of fuel. In severe frost, the number of full bookmarks of fuel should not exceed three.
Complete energy independence. The device must work without the need to connect it to the mains. In the event of a wire break or a power outage, the operation of the circulation pump (it must pump the coolant) is provided by a backup power system.

The heating system is selected, depending on the climatic conditions of residence, heat loss at home, the availability of a particular type of fuel, energy prices in your area.

Also among the main requirements for the boiler were listed:

high efficiency, simple and inexpensive chimney design;
small formation of soot and deposits (which means that there is no need for frequent cleaning of the boiler and its efficiency increases);
safe operation of the boiler under any operating conditions, heat resistance of the units;
the possibility of additional loading of firewood during the operating mode;
ease of operation of the boiler when installed in a residential area;
small weight and dimensions.

The most interesting thing is that it was planned to “put” all these requirements into the budget, not exceeding 500 dollars except for labor costs.

It is enough just to get acquainted with the requirements superficially in order to understand that finding a solid fuel boiler that meets all the items on the list is not an easy task. That's why Perelesnik decided to go two ways:

Try to find a finished factory product.
In case of failure, copy the design of the finished boiler and make it yourself.

During the search and further study of information, both options have disappeared. Due to technical features: the “capriciousness” of working on “wet” wood, the impossibility of working at low power, etc. long-burning pyrolysis boilers did not fit. Also, they were not satisfied with the “home-made products” found on the expanses of the “World Wide Web”. The third option remained - based on their knowledge and experience gained, develop the design of a solid fuel boiler “for themselves”.

Rocket boiler - theory

During your search Perelesnik stumbled upon a rocket furnace, and this design “hooked” him.

Perelesnik

The rocket stove attracted me because it does not require any special chimney for its operation, we can say that it is not needed at all. The rocket stove has excellent traction, and without the use of any fans. Its design provides high-temperature afterburning of furnace gases. It is not demanding on the quality of fuel, it works effectively at different capacities.

The matter remained small - to make a boiler out of the stove. Looking ahead, let's say that almost a year has passed from the idea to the implementation of the furnace "into metal". This included several months in search of the optimal design, calculations, experiments. It took three months to make the boiler itself, but the result was worth it.

We managed to make a device that met almost all the requirements of the list (with the exception of the fact that it is possible to add fuel only when the previous batch burns down to the state of coal). Moreover, it was possible meet the planned budget, although "stainless steel" was used for the construction of the internal parts and parts of the boiler and home-made heat-resistant ceramics were used.

Perelesnik developed a diagram that clearly shows the principle of operation of his boiler.

To understand why the rocket furnace was chosen as the basis for the boiler, it is worth focusing on the theoretical part.

Rocket furnaces are well known. They are built by enthusiasts and do-it-yourselfers around the world. The simplicity of their design, the ability to do without the use of expensive materials, and the great variability of such furnaces are captivating. A rocket stove can be as small as a camp stove (food is cooked on them), made from pieces of metal pipes and cans.

And also a large, heating one, with a massive heat accumulator and a built-in stove bench. Such a "rocket" fits perfectly into the design of a modern cottage.

According to Perelesnik, a great help in the development of his boiler was provided by the book of American authors "Rocket Furnaces". It clearly, and most importantly - simply and intelligibly - explains the basic principles of self-construction of rocket furnaces. From this book, the main dimensions and proportions of the "heart" of the rocket boiler were also borrowed - the so-called. "J-pipes".

Perelesnik

The "rocket" creates excellent conditions for combustion. Fuel and furnace gases burn out completely. The resulting heat is not "taken away" until all reactions are completed, and only then it is used.

The advantages and pluses of the "rocket" are derived from the features of its design. At the rocket stove, at the expense of long vertical and additionally insulated channel, the length of the path that the furnace gases pass through increases.

Gases, while passing through an elongated channel, are mixed with already heated air and acquire a temperature that best promotes all combustion processes. It also burns carbon, which, if underburned, is deposited in the form of soot.

The high efficiency of the "rocket" is ensured due to the fact that wood is burned out, which is released during the thermal decomposition of solid fuel (the so-called pyrolysis).

Due to the large temperature difference that occurs at the inlet and outlet of the vertical pipe channel, a powerful natural draft arises. Accordingly, there will be no need to build a high chimney, which provides draft in conventional furnaces.

It should be noted that the gases entering the smoke channel have a high temperature. So that the energy generated by the furnace does not fly out “into the pipe”, you need to take away part of this heat. To do this, a bench is attached to the rocket furnace, where flue gases are launched through horizontally laid out brick channels. It turns out a heat accumulator. The second option - the oven is complemented by a shirt. From here it is already within easy reach of a solid fuel boiler.

Pushing off from this base, Perelesnik decided - it is necessary to make a boiler that works on the principle of a rocket furnace.