Do-it-yourself jet stove for home heating. Bubafonya and Rocket: do-it-yourself top-loading ovens. Advantages of jet furnaces and how they work

The jet stove or rocket stove came about as a result of a departure from the tradition of building space heating equipment. It is considered an economical heat generator, the design of which is elementary. Therefore, many are thinking about building a jet furnace with their own hands.

Description, advantages and disadvantages of the rocket oven

A heat generator for heating indoor air is called a rocket stove or a jet stove, because during operation it makes special sounds in case of excessive air intake. This noise can be mistaken for the roar of a jet engine. In normal mode, the equipment operates with a barely audible rustling sound.

The rocket stove serves as a home heating and cooking device. It takes about 6 hours to burn one batch of firewood in such equipment, more than in a standard metal stove. The reason for this is the creation of a heat generator based on a furnace with upper combustion.

The flame from the jet furnace can escape

The advantages of the rocket oven include:

• independence from fuel energy;
• simplicity of design, consisting of affordable parts, connected in a matter of minutes;
• the ability to produce a lot of heat, despite the quality of the loaded fuel.

The jet furnace also has some disadvantages:

• manual control, which implies constant monitoring of equipment operation;
• danger of getting burned, because the walls of the equipment become extremely hot;
• inexpediency of use in the bath, because it will not be possible to warm it up.

Kinds

A unit that emits a rocket hum during operation happens:

• portable (unit of metal pipes, buckets or gas cylinder);

  Portable rocket furnaces are mass-produced by the industry

• stationary (created from fireclay bricks and metal containers);

  Such a unit is more difficult to build than a metal furnace.

• equipment for heating air with a bench.

  The bench is equipped behind the rear wall of the oven

Portable structures are made in large batches, because they are used for hiking. The basis of these heat generators is a pipe made up of several segments. True, such structures, unlike units based on fireclay bricks, are not reliable. The walls of refractory blocks increase the heat transfer of the jet furnace. If desired, you can add a couch in the form of a sofa or bed, decorated with clay or sawdust.

Details and operation of a jet heat generator

An elementary rocket furnace is a device of two pipe fragments connected by a branch at an angle of 90 degrees. The combustion chamber in this heat generator is usually a zone in the horizontal part of the structure. But sometimes the fuel is placed in the vertical section of the apparatus, for which the rocket furnace is constructed from two pipes of different lengths, mounted vertically and connected by a common horizontal channel.

Primary and secondary air passes through the furnace

The functioning of the jet furnace is based on two actions: the unhindered passage of wood gases through the pipe and the afterburning of gases produced during the combustion of fuel. Wood chips and firewood are placed in the furnace of this heat generator after a highly flammable material like paper has ignited there. A container with water or other contents is placed on the open section of the pipe. At the same time, between the structure and the installed tank, leave small space needed to generate traction.

The processes occurring inside a stationary jet furnace resemble the operation of pyrolysis heating units.

Calculation of parameters (tables)

The volume of the furnace should be determined with skill, because it is he who affects the power and amount of heat generated by heating equipment. When calculating the dimensions of reactive heating equipment, an indicator of the internal diameter of the drum D is used, the value of which can vary within 300–600 mm. You also need to know the cross-sectional area of ​​the drum. To determine this indicator of a rocket furnace, use the formula: S = 3.14 * D ^ 2 / 4.

The main dimensions of the jet furnace are presented in the table:

Particular importance is attached to the length of the flue with a stove bench. The maximum allowable indicators are shown in the table:

The volume of the secondary ash chamber is also important indicator, depending on the volume of the drum and the primary chimney.

Building materials for the construction of a non-standard furnace

The production of jet heating equipment will require the presence of:

• barrels with a volume of 200 liters and a diameter of 0.6 meters, an empty liquefied gas cylinder or tin buckets to build a furnace drum;
• square or round steel pipes 2-3 mm thick, which are needed to create a blower, a combustion chamber and a primary chimney;
• fireclay crushed stone and furnace clay as heat-insulating materials;
• adobe, which serves as an outer coating layer;
• fireclay bricks;
• sand from the bottom of the river;
• pieces of sheets of zinc-coated steel or aluminum for the manufacture of covers and doors;
• asbestos or basalt cardboard, which performs the tasks of a sealant.

Of the tools for the construction of a rocket furnace, you will need a welding machine. And if you plan to do heating equipment from bricks, you have to take:

• Master OK;
• mortar blade;
• pick hammer;
• stitching;
• an acute-angled sledgehammer;
• level;
• plumb;
• roulette.

Preparing for the assembly of heating equipment

When choosing a place for a rocket furnace, they are guided by some rules:

• reactive heating equipment is placed only in a room with an area of ​​at least 16 m²;
• without floorboards under the oven, equipment installation will be easier;
• above the structure that gives heat, it is forbidden to place wooden beams;
• if it is understood that the chimney will go through the ceilings, then the heating equipment is placed in the middle of the house;
• the heat generator cannot be installed near the outer contour of the house, otherwise the room will lose heated air;
• the jet device must not be placed near the walls and partitions of their wooden materials.

To make it convenient to put fuel in jet heating equipment, it is more reasonable to put it with the front side opposite the entrance. It is important to leave at least a meter of unoccupied space around the rocket stove.

In a small house, builders are advised to allocate a place in the corner for the stove. In this case, the firebox should be directed in one direction, and the stove bench (if it is made) in the other.

The stove stands on a special platform that protects the floor from high temperatures.

Having found a suitable site for a rocket furnace, they begin to prepare it for construction work. If boards are laid on the floor in the house, then in the place where the equipment will be installed, they will need to be removed. A hole is dug under the open floor, the bottom of which must be pressed.

Before construction work, a special mortar should be mixed. It consists of sand and clay combined in a ratio of 1:1. Water will be needed so much that the building materials acquire the consistency of sour cream, that is, ¼ of the amount of dry ingredients.

Do-it-yourself step-by-step instructions for making

If it is planned to make a rocket furnace from a gas cylinder, then you can not be afraid of difficulties. The steps to create equipment from such building materials are quite simple:

1. from a cylinder with a volume of 50 liters, the upper part is cut off in order to build a kind of cap;

   The balloon is cut at the top and bottom

2. focusing on the instructions in the drawing, all parts of the product are welded to each other, that is, a gas cylinder, a pipe with a diameter of 10 cm (future chimney), a pipe with a diameter of 7 cm (internal channel) and another pipe with a diameter of 15 cm (firebox);

   Dimensions are in mm

3. the space between the two pipes is filled with a material that retains heat, for example, sand, which has been carefully calcined, that is, cleaned of organic substances;
4. legs are welded to give stability to the structure.

To build a rocket stove with a stove bench, which involves the use of bricks, you need to act differently:

1. The area for arranging the firebox is deepened by removing 10 cm of soil. The combustion chamber is formed from fireclay bricks. A formwork is created along the contour of the manufactured structure. To make the base strong, it is recommended to lay a reinforcing mesh or metal bars in it;

   The platform will harden in about two days

2. The structure is poured with liquid concrete. Then they wait for the solution to harden, and finish the job. Bricks are laid in a continuous line, creating a platform for the furnace. After that, the walls of the structure are formed, exposing several rows of brick blocks;
3. They equip the lower channel of the structure, while one line of bricks is laid across to block the combustion chamber. The blocks are placed, leaving the vertical channel and the opening of the firebox open;

   Two sectors of the furnace at this stage of construction must be open

4. They find a body from an old boiler and cut off the top and bottom covers on it. At the bottom of the resulting pipe, a flange is installed through which a horizontal heat exchanger will pass. Parts need to be connected to each other with a continuous weld;

   Work requires diligence

5. An outlet pipe is inserted into the barrel, after which they take a brush for metal and scrape rust from the walls of the container. The cleaned barrel is treated with a primer, and a little later - with paint that is resistant to high temperatures;
6. The horizontal chimney is connected by welding to the side outlet - the future ash pan. To facilitate its cleaning, a sealed flange is mounted;
7. Lay out the flame tube from refractory bricks. At the same time, a channel with a height and width of 18 cm is formed inside the structure. While doing this, they constantly use the building level, which allows you to control the verticality of the product;

   The height of the pipe is predetermined

8. The flame tube is covered with a protective casing, and the resulting gaps are clogged with perlite. The lower area of ​​the vertical channel is sealed with wet clay, the function of which is to prevent the heat-insulating material from spilling onto the floor;
9. From the boiler, on which the top and bottom were cut off, a fuel tank is formed. A handle must be welded to it;
10. To improve the appearance, the structure is treated with adobe putty, consisting of sawdust and raw clay. The first component of the composition serves in the same way as crushed stone in concrete, that is, it prevents cracking of the furnace walls. It is recommended to apply adobe putty on top of perlite backfill;
11. They create the facade of the furnace, for which the furnace circuit is laid out of stone, bricks, adobe and sand. The wrong side of the structure is filled with crushed stone, and the front side is filled with adobe mixture, which makes the surface perfectly even;
12. A casing made of a metal barrel is placed on the previously created base. The lower branch pipe of the tank is directed towards the bench. The bottom of the structure is treated with raw clay, which will ensure its tightness;
13. A channel is brought to the combustion chamber from corrugated pipe. It will serve as a link between the firebox and the atmosphere from the outside;

    At this stage, the oven looks almost finished.

14. A test kindling of the furnace is carried out, looking at how the gases are removed from the horizontal chimney. After that, the heat exchanger pipes are connected to the lower branch pipe installed on the red brick platform;
15. The furnace is supplemented with a pipe for removing smoke. The junction of the chimney and the heat generator is sealed with refractory coating and asbestos cord;
16. Using clay and adobe, the couch is given the desired shape. Only the horizontal section of the structure is left unsealed, which will then be used during cooking.

    The furnace functions as a whole system

Design improvement

A stove bench with a flue inside is not the only option for upgrading a rocket furnace. The design can be improved with a water jacket connected to a heating system in which water circulates. It is desirable to give this part of the structure the appearance of a coil, created from a copper pipe, twisting on the chimney.

This design provides even more warmth.

Another way to improve the jet furnace is associated with the organization of the flow of heated secondary air into the flame tube. This will increase the efficiency of the heat generator, but will lead to deposits in the primary chimney a large number soot. Therefore, it is better to make sure that the drum cover can be dismantled if necessary.

The subtleties of operating an unconventional furnace

The rocket furnace is heated by analogy with the upper combustion heat generator. It turns out that the kindling of equipment called a rocket must be carried out according to certain rules:

• the main raw material for the furnace of the unit must be laid only after the structure has warmed up well, for which, first, sawdust or paper is placed and set on fire in the blowing sector;
• they necessarily react to the muffling of the rumble emanating from the furnace - they put a large batch of fuel into the combustion chamber, which will ignite on its own from the red-hot residues of sawdust;
• the process is closely monitored, that is, after laying firewood, the damper is fully opened, and after a while, when the equipment makes a hum, it is covered to produce a sound similar to rustling;
• as necessary, the damper is covered more and more, otherwise the furnace will become filled with an excess volume of air, which will disrupt the pyrolysis inside the flame tube and lead to the creation of a strong hum.

Since the reaction furnace was originally designed for use in field conditions, its design is extremely simple. This allows you to cope with the manufacture of the unit by an ordinary home master. But, despite the apparent lightness, the rocket stove is supposed to be assembled, taking into account the correct ratio of parameters. Otherwise, the equipment will be unproductive.

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 understood 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 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 released 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 is too much air, the stove roars, but don't be happy: now the excess air cools the primary gas mixture, and the sound is amplified as the steady swirl in the riser clumps into a disorderly lump. 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 mode 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 for the sake of compactness.

With a large furnace, 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:

1. Drum height H - 1.5-2D.
2. 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.
3. The thickness of the coating of the drum is 1/3D.
4. The cross-sectional area of ​​the riser is 4.5-6.5% of S; it is better to stay within 5-6% of S.
5. 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.
6. The length of the flame tube is equal to the height of the riser.
7. 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.
8. 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.
9. 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.
10. The cross-sectional area of ​​​​the external chimney is 1.5-2S.
11. 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.
12. 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.
13. The height of the external chimney is from 4 m.
14. 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 building 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

P.S. And remember, just by changing your consciousness - together we change the world! © econet

Consumption ecology. Among the variety of wood-burning stoves, such a thermal device as a home-made rocket stove deserves special attention. It is distinguished by an original design that does not require expensive materials and components in the manufacture.

Among the variety of wood-burning stoves, such a heating device as a homemade rocket stove deserves special attention. It is distinguished by an original design that does not require expensive materials and components in the manufacture.

Any person can make such a stove, at least a little bit versed in the drawings and able to work with his hands. Our article should come to the aid of such home craftsmen, where we will talk about the design and principle of operation of the rocket stove. Here, recommendations will be given on its manufacture from various materials.

OPERATING PRINCIPLES OF THE ROCKET FURNACE

Although the rocket stove device is quite simple, it successfully uses two whole principles of operation borrowed from other types of solid fuel heaters:
- the principle of afterburning wood gases released during combustion (pyrolysis);
- the principle of free flow of gases through the channels (without prompting from the natural draft of the chimney).

Note. In the simplest rocket stoves for cooking, including those of a portable type, only the second principle operates, since favorable conditions are not created for the pyrolysis process to proceed.

First, we will analyze the design of direct-burning rocket stoves, designed only for cooking food. Here, a short horizontal section of the pipe serves as a firebox, which then turns upward. The design is simple to disgrace

Fuel is put into the pipe and ignited, resulting in an upward flow of hot gases, which tends to rise along the vertical section and go outside. Here, at the cut of the pipe, a container for food or water is installed. Of course, a gap is provided between the pan and the pipe for the exit of combustion products. This is achieved through various metal supports.

For reference. The above rocket furnace device is one of the first. It is because of the nozzle turned up with a flame escaping from it that the device was called a rocket.

Since it is impossible to heat the premises with such a unit, the design of the heating rocket furnace was supplemented with a heat exchanger and channels for removing flue gases. To keep a high temperature on the vertical section of the pipe, it is insulated with any refractory material. Further, for intensive heat extraction, the nozzle is covered from above with a cap, for example, a conventional metal barrel. A separate channel for supplying secondary air is made in the lower part of the horizontal fire tube.

Now the principle of operation of the rocket furnace looks a little different. Firstly, at the end of the horizontal fire channel, pyrolysis gases are afterburned due to the inflow of secondary air. Secondly, the products of combustion, which have a high temperature, accumulate under the top of the cap (barrel), creating some excess pressure. As heat is transferred to the outside through the metal walls, these gases cool down and rush down.

Since the cooling gases are supported from below by a new hot stream, they cannot descend in the same way, but pass through the space between the walls of the pipe and the barrel, safely exiting into the chimney channel. The flow of processes is well reflected in the scheme of the rocket furnace

So, thanks to pyrolysis, the efficiency of wood combustion increases, and the use of free flow of gases creates a self-regulating system that limits the flow of fresh air into the firebox. The air mixture is supplied as the combustion products under the hood cool down, making room for it. new portion. The excess pressure of hot gases "pushes" the cooled part out, so the operation of the furnace depends little on the presence of draft in the chimney.

HEAT REMOVAL EFFECT

The gases entering the chimney are still at a high temperature. Just throwing them out is impractical, everyone will understand that the efficiency of such an installation will be too low. Taking advantage of the fact that the rocket stove literally pushes the combustion products out, the craftsmen invented 2 ways of heat extraction:
- passing gases through the channels arranged under the bench;
- installing a water circuit on the stove.

A rocket furnace with a water circuit is made without a hood, the force of the upward flow of combustion products is used in a multi-pass heat exchanger made of metal. It is not recommended to introduce a coil with water into the gas flow, it will not last long due to too high a temperature. It would be more correct to make a water jacket with metal fins inside the flue

Another way is to lay out horizontal chimney channels from bricks directly on the floor surface and arrange a chic heated adobe bed on top by connecting a rocket-type stove to it. Here, the correct selection of the length of the channels is important so that there is enough excess pressure to overcome them, otherwise you still have to take care of the organization of natural draft.

ADVANTAGES AND DISADVANTAGES

Homemade long-burning rocket stoves have many admirers, and here are the reasons:

Simplicity and low cost of installation: in order to build such a thermal device, you do not need to incur high costs for the purchase of expensive materials, fixtures and fittings. Experience in the furnace business is also required minimal;

Self-regulation and undemanding to the natural draft of the chimney;

The efficiency of the furnace - rocket is a variable value and largely depends on the design, the main thing is to maximize the removal of thermal energy from flue gases;

Fuel can be added "on the go".

Despite the attractiveness and simplicity of the unit, heating with a rocket stove has its negative points. It is a mistake to think that you can shove firewood of any quality into the firebox. Wet wood will not required temperature in the chamber, the pyrolysis process will not proceed. In the worst case, the smoke from the stove can pour into the room. Also, the “rocket” needs constant supervision, especially in terms of fire safety.

Do-it-yourself rocket stoves are of little use for a bath, because they give off relatively little heat in the infrared range, which is very important for a steam room. The surfaces of the stove that radiate heat are too small and it will not be possible to heat the bath properly.
For reference. A factory-made Robinson metal rocket furnace is often used as a portable heat source. The craftsmen were not at a loss here either and quickly modernized this product, having done the same, only with a grate.

FURNACE FROM A CYLINDER

This is one of the simplest options, you can use the drawing below to implement it. A propane tank with a diameter of 300 mm will serve as an excellent cap, and a steel pipe with a size of 150 mm will play the role of a firebox and a hopper. The internal vertical channel is made of a pipe with a diameter of 70 mm, and a chimney - 100 mm

The design is completely welded, the pipes are cut to the required length, and the cylinder is cut off top part. Then the parts are welded according to the drawings, only the opening between vertical pipes with a diameter of 70 and 150 mm is filled with loose heat-insulating material. Perlite or vermiculite can act as such, in extreme cases - ordinary sand.
If there is an opportunity and desire to make a more powerful rocket furnace, then a standard 200-liter barrel is used as a cap, then the dimensions of all parts also increase. The working inner pipe is accepted with a diameter of 129 mm (or profile 120 x 120 mm), and the outer one - with a size of 450 mm. It is difficult to pick up a pipe of this diameter, so they usually find another barrel of a smaller capacity and cut off its bottom

The entire rocket furnace from a gas cylinder assembly is not very heavy, so it is not necessary to arrange a massive foundation for it. When the unit is placed on the floor, legs are welded to it, and if a stove bench is subsequently planned, then the structure will have to be coated with a refractory compound, and then the outer lining should be made. Then basalt cardboard and a sheet of roofing iron are laid on the floor from below.

BRICK OVEN

In terms of its design, a brick rocket furnace is not much different from a metal one, but it requires a lot of labor. The difference is that all fire channels of the unit are made of fireclay bricks, and the cap is made from the same barrel.

The entire structure, except for the protruding cap, is recommended to be lowered below the floor level, for which a shallow hole is dug. Its bottom is compacted, and then a small concrete foundation 100 mm thick is poured along the formwork. After it hardens, laying begins, using a solution of refractory clay. After the laying is completed and the mortar has hardened, the pit is filled up, and an iron barrel without a bottom is put on top of the fire channel, the cavity between it and the brick is covered with insulation.
For all its advantages, a do-it-yourself rocket stove cannot serve as a full-fledged source of heat for heating the whole house. It makes sense to start such construction when it is necessary to organize the heating of a small cottage or other similar building, especially since the "rocket" is not afraid of periodic work. published

Jet stoves have become popular not so long ago. In addition, not everyone knows about the advantages of such a heating system. It is worth noting that they are classified as energy efficient stoves. Their name is heating systems obtained thanks to reactive processes based precisely on heat transfer at significant temperature differences. At the same time, thrust arises in the jet furnace. Similar phenomenon described in the basic physics course. And this is thanks to the work without failures.

The design of the furnace "Rocket"

The jet furnace is always equipped with a knee, the angle of which is not more than ninety degrees. This is the main feature of this model. In other words, the chimney in relation to the bottom of the firebox is located at an acute or right angle. In this case, the oven must be equipped with an air duct. It is usually placed through the wall with the firebox.

Advantages of jet furnaces and how they work

Before a do-it-yourself jet furnace is built, it is worth understanding the principle of its operation and evaluating its merits. The main difference of such a design is that the concentration of temperature occurs precisely in the air stream, which is constantly in motion, and not in the furnace. In this case, continuous thrust occurs in the knee - in the place of heating. Air with oxygen for combustion is supplied through the duct, and in the furnace it receives a sufficient amount of thermal energy. In this case, ordinary wood can be used as fuel. In places where there is a temperature difference, it is given. Thus, traction is constantly maintained.

A jet furnace in continuous operation does not require special adjustment of the air supply. After all, the natural balance of all processes provides the necessary traction. In other words, the one that is required to maintain the desired temperature in the furnace. As for the exit of all exhaust gases, this process also proceeds naturally, using the pressure of already heated air. It is for this reason that the jet furnace is built with a low chimney.

The first stage of construction: flows only in their pure form

The jet furnace, the scheme of which is not so complicated, consists of several important elements. One of them is the knee. For its manufacture, two pipes can be welded at a right angle. In diameter, these parts must be at least fifteen centimeters. In this case, a ratio of 1 to 2 must be observed. As a result, a ready-made firebox with a chimney pipe should be obtained. The short part of the knee should be horizontal, and the long part vertical. If you make a fire in the pipe, then the heat will go up.

To organize the supply of secondary air, you can use one of the primitive options. To do this, a metal sheet should be installed on the brackets inside the furnace. This will move the hearth away from the duct. But the air that will pass through it will always end up in the corner of the knee. This is what makes it possible to call it secondary. To make the do-it-yourself reactive oven more functional, you can weld the legs to the finished device, and install a grate for the pan on the upper channel.

The second stage of construction: potbelly stove "rocket"

The basis is the design built at the first stage. One more important element needs to be added to it - a horizontal section. Rectangular section channels are much more convenient in terms of operation than pipes. A jet furnace, the drawings of which allow you to more accurately imagine the entire structure, may have a different structure. In this case, the duct can be positioned arbitrarily. However, it is worth observing one of the rules. In any case, air must pass through the duct. To do this, you can use plates on the ribs along the bottom wall, parallel side walls of the loading hatch or "brushes".

After that, the steel chimney is attached to the knee. Then you can install the roof. It is very difficult to describe exactly this structure. After all, for its manufacture usually use all sorts of improvised materials. Often a jet furnace is made from a gas cylinder. The main thing is to implement the principle of flow formation.

Third stage of construction: design with vertical heat exchanger

This idea is to create a heat exchanger made of steel with sufficiently thick walls precisely in the path of heat flows. The element built in the second stage must be increased in size. To do this, instead of a vertical pipe, an empty container must be installed, which will be used for dry heat exchange. In this case, a gas cylinder is ideal.

The jet furnace must be built in such a way that the horizontal element is aligned with the chimney channel. This moment is very important. In this case, the firebox - a horizontal element - can be made in several versions. It can be a box, a pipe or a stove body. If this part has sufficient dimensions, then it can be used as a pre-heat exchanger.

In order for the jet furnace, the scheme of which is presented above, to burn continuously for up to 4 hours, it is the fuel compartment that should be increased in size. In height, this element can be up to 60 centimeters. In this case, the loading of logs must be vertical. In such a situation, the combustion of raw materials will occur in the lower part. The logs will gradually burn and sink under their own weight.

The reactive furnace "Shirokov" is quite simple in design. Primary air is usually supplied through a door located in the area of ​​​​the firebox, and secondary air is supplied through a channel or an opening on the knee.

The fourth stage of construction: installation of the injector

At this stage, it is necessary to equip the product with a separate channel, through which oxygen will flow at the stage of fuel burnout. This requires a pipe with a diameter of 1.2-1.5 centimeters, preferably curved in the shape of the channel itself, resulting from individual structural elements. On one side, a plug should be installed and up to eight holes with a diameter of six millimeters should be made in one of the walls. The area with holes made in length should be no more than 100 millimeters. The finished pipe must be installed in such a way that it passes through the entire system. In this case, the edge with the plug should reach the place where the flame still reaches. As for the open side, it should be in the cold part of the structure and have an influx of fresh air. The metal, when heated, will create the necessary traction.

Fifth stage of construction: installation of a turbocharger

The jet furnace is not yet completed at this stage. Connect an air pump to the injector. For these purposes, you can use an ordinary old vacuum cleaner. In this case, the injector must have sufficient throughput. After the pump is turned on, not only will the flow of fresh air increase, but an additional one will also be created. At the same time, thrust will increase in proportion to the supplied power. This process will be provided by increasing the temperature in the heat exchanger.

It is worth noting that this method has been known for a long time. It was used by masters. At the same time, the functions of the air pump were performed by a special blacksmith fur.

Instead of a conclusion

If you are interested in a jet stove, and you decide to install it in your house, remember a few basic rules. First of all, every detail in the system must be harmonious. Each piece of the structure must be balanced. Otherwise, overheating will occur, which will eventually lead to burn-out of metal parts. It is worth noting that it is necessary to install a jet furnace not near the wall, but at some distance from it. So it will heat the room more efficiently.