Today, many are wondering how and what is the best way to heat their home if there is no gas. Firewood and coal are among the most available types fuel. That's why the right decision Here it will be possible to build a heating stove, or even better, add to it the function of a cooking stove for cooking. There are a lot of design options both in form and in operating principles.
In this article I will introduce you to the features of the Kuznetsov furnace, its advantages and a step-by-step scheme for constructing such a unit yourself.
The furnaces of engineer Kuznetsov have been known not only in their homeland, but throughout the world since the 60s of the last century.
Moreover, the relevance of developments made half a century ago has not diminished at all, but on the contrary, Kuznetsov’s furnaces are becoming more and more popular.
The goal of modernizing the ancient design of a Russian stove with not so significant changes to it internal structure was the creation of a heating unit with higher efficiency while saving fuel.
Bell furnaces are one of the most common and their characteristics are in no way inferior to channel furnaces.
This stove is the latest development in the conservative field: installation and design of stoves. This stove is fundamentally distinguished new method using hot gas.
In design standard type the movement of cold and hot gas occurs due to the draft of air, which enters through the ash pan.
The principle of a bell furnace is very similar to the operation of rocket furnaces, where hot gases move not under the influence of the chimney draft, but due to the gravity of the gases themselves.
Advantages and disadvantages of the oven
Advantages:
- high efficiency factor of 75-85% (efficiency);
- fuel burns at high temperatures;
- the stove operates on all types of solid fuel - wood, hard and brown coal, briquettes, etc.;
- ease of maintenance, no need to clean long channels (low soot formation);
- durability of the furnace;
- aesthetic, original appearance;
- high efficiency, multifunctionality;
- efficiency;
- long-term heat retention;
- the shape and design of stoves may vary depending on the purpose;
with the frequency of adding fuel to the Kuznetsovka only twice a day, you can have a thermal regime in the house that compares favorably even with the regime of apartments with central heating.
An apartment in a high-rise building has more frequent temperature fluctuations than private house, heated by a Kuznetsov stove, which gives uniform heat output between the fireboxes;
- The design of the blacksmith allows the installation of low chimneys, and there is no reduction in draft. This fact is somewhat surprising to those who are getting acquainted with the design and operation of these furnaces for the first time;
Combining a Kuznetsov stove and water heating at home is not difficult and is often used in practice.
A tubular heat exchanger is installed inside the furnace and connected to the pipeline heating circuit. The main advantage is that the heating technology and heat output of the furnace remain unchanged during modernization, without the slightest decrease in efficiency;
peculiarities internal structure Kuznetsov stoves allow you to install the unit in almost any room of any size, regardless of what the room is intended for.
Both in kitchens and in common rooms, the stove looks solid and aesthetically pleasing, and fits organically into many interiors;
The most interesting and unusual feature of blacksmithing in the context of a house stove: you don’t have to close the view. This the most important detail furnace and one of the conditions for safe everyday operation - for the Kuznetsov furnace it is needed only if an emergency situation occurs.
The fact is that when the fuel combustion process comes to an end and cooling begins, the draft in the furnace channels is redistributed spontaneously, “automatically”.
It was the bell-type stoves that became the basis for the creation of many new types of household, heating and cooking stoves, which provide significantly best effect with less fuel consumption.
What can you say about the disadvantages of the stove?
Technically there are none, but there are still some things to consider.
The Kuznetsov furnace cannot have massive walls - this would negate many of its advantages. But at the same time it is subject to fairly high thermal loads.
Therefore, this unit must be carefully calculated and verified at the development stage and built just as carefully, with scrupulous compliance with all technology requirements. At the slightest deviation from the technical regulations, the “smithing” will turn out to be very short-lived.
Operating principle of the furnace
It is based on the principle of free movement of gases. To circulate air in a conventional furnace, it is necessary to use external energy, that is, to create forced draft in the pipe.
When gases are in a confined space, if there is permanent source heat, they separate under their own weight - cold ones settle down, hot ones rise up. At the same time, in the region of high temperatures, the pressure increases, and where it is cold, it drops and energy is generated.
It turns out that turbulent motion occurs automatically due to the laws of physics. This means that if convection currents are directed correctly, thermal energy will be transferred by the gas masses themselves.
With electric heat supply, no draft pipe is required. If the stove is heated with wood, then the combustion product must invariably come out.
Thanks to a clever design, it accumulates at the last stage of its journey, ending up as if under a hood. There it burns out again, completely giving up its heat, and then is released into the street in the form of useless gas, without cooling the system. Such furnaces are also called bell-type furnaces.
The fundamental feature of gas filling of cavities is that, no matter how many compartments the furnace has, they are all filled with gas evenly and the same physical processes occur in all of them. It is impossible to create something similar using traction, the countercurrent principle (widely used in Europe) or other convective methods.
That is why such stoves are an innovation in the stove heating system.
They regulate themselves and, no matter what configuration they are given, they always work according to a natural principle.
The principle of the stove design is quite simple: the lower tier and the firebox (also called the hearth) are combined into a single space - a cap, inside which the free movement of hot gases occurs.
The hottest, lighter gases move to the top of the bell, and the “heaviest” cold gases are located at the bottom. And gases having an intermediate temperature circulate between them.
The heated air is held in the furnace for a long time, transferring the heat to the walls of the hood, and the cooled air is discharged through a special passage into the chimney. The combustion temperature in the hood is very high. The efficiency of such a stove is three times higher than that of a traditional Russian one.
Types of Kuznetsov stoves
Based on the functions they perform, Kuznetsov’s brick kilns can be divided into several main groups:
Heating.
Their main task is to heat rooms.
Cooking.
They are used for cooking. This group also includes bread ovens and stoves adapted for cauldrons.
The operating principle of Kuznetsov’s sauna stoves remains unchanged - the natural movement of gases through two bells. Another thing is that there is a heater here, which needs to be heated thoroughly to obtain high-quality steam.
The developer proposed and is still using the optimal technical solution, where the stone backfill is placed in a heat-resistant steel oven. The oven is located directly above the firebox.
The thermal energy accumulated in the lower and upper hoods is used to heat water and heat not only the steam room, but also all adjacent rooms. The water coil is installed under the first hood so that it can be easily repaired or replaced.
The installation location can be determined by studying the drawings of the furnaces.
- Fireplaces.
- Grills and barbecues.
- Combined structures, complexes.
- Perhaps the most popular are Kuznetsov’s heating and cooking stoves. They will warm the house and won’t leave you hungry.
Kuznetsov also has such projects.
Before you start building, make sure that this is exactly the option that you want to see in your home.
Such stoves imply the presence of a convenient ledge with a cast-iron surface, with the possibility of partially opening the holes to increase the temperature. It is also possible to make a door for a cauldron, similar to ancient Russian stoves.
The layout of heating and cooking stoves requires its own approach and individual drawings.
Bell furnaces can be erected in almost any room. This could be an apartment, a residential building, an outbuilding or a bathhouse. For example, for a bathhouse, a bell-type stove will be an ideal replacement for an ordinary standard stove.
By building this sauna stove, you can solve several problems at once. This design is capable of heating several rooms: a sink and a steam room, as well as a relaxation room. In addition, it is very convenient to heat water on the stove, simultaneously creating steam in the required quantity.
The house can be equipped with two-bell heating using a stove, this installation is very functional. Before erecting such a structure, it is necessary to carefully study the project.
A system that burns raw fuel must be organized in the most in the best possible way. The oven must always be maintained correct temperature, otherwise the gases that are formed after combustion can be transformed into harmful waste soot and tar.
Do-it-yourself Kuznetsov stove
Building a blacksmith shop requires not so much skill as the availability of good diagrams and drawings, as well as extreme care. Even a non-stove maker, but a skilled house owner can master this task.
It will be easier for those who already have valuable experience brickwork, then the only thing you need to do is to quietly and peacefully lay the rows, following the pattern.
If you decide to build a stove according to one of Kuznetsov’s plans with your own hands, get ready for careful and scrupulous work.
On the diagrams that can be easily found on the Internet, you will see a graphical representation of each row, but before you start laying, you need to become familiar with the features of the technique, in particular:
- selection and pre-processing of bricks;
- purchase metal parts(plates, dampers, doors, valves);
- determining the most suitable location;
- preparation of the base and foundation;
- possibility of installing a chimney, etc.
Fireclay refractory brick (Sh-5, ShB-8) is recognized as the best material for the internal masonry of “smiths”, and ceramics (M-150) for external decoration.
To enhance brick walls use metal elements (reinforcement, wire).
In order for the stove to function with maximum heat output, experienced craftsmen hone not only their skills, but also every brick - literally. They polish every detail, which is why projects completed by professionals look flawless.
The main purpose of any furnace is heating; its location must be chosen to provide heat in the most efficient way.
Kuznetsov furnace are infrared heaters, which provide the greatest heat by direct radiation.
Thus, maximum power is achieved with the correct positioning.
Therefore, the center of the room is always the right choice. A wise decision is to place it as a divider between functional spaces, such as the kitchen and living room or living room and bedroom.
Try to avoid placing the masonry stove next to an outside wall or, even worse, placing it in a niche in an outside wall (a typical location for conventional fireplaces) if you want to keep the heat inside the room.
The choice of a stove of one type or another and its location in the house, in addition to the owner’s preferences, depends on the intended purpose of the stove, the size of the house and its level of thermal insulation, the number and size of windows.
In addition, for normal operation and repairs, access to the furnace must be free from all sides, that is, none of the sides of the furnace should simultaneously enter any of the external walls Houses.
To complete the construction process, you need to stock up on a bayonet and shovel, as well as the following materials:
- sand (3 parts), cement (1 part) and water to prepare the solution;
- reinforcing rod of medium section;
- plastic film;
- board for constructing formwork.
Construction stages:
- After making the foundation, you need to take care of preparing the mortar for laying the stove. To build a brick kiln, they use clay, not cement. And not just any one, but only one that lies at a depth of at least 2 meters. The clay is sifted and washed out, preparing a solution of the desired viscosity.
- After complete hardening concrete foundation You can start laying bricks. The Kuznetsov furnace is built correctly only if the order proposed by the inventor is followed.
- Before starting masonry, it is worth considering the location of the chimney pipe inside the room and outside on the roof, which must meet certain requirements. Let us recall that any Kuznetsov furnace has ready-made drawings, in accordance with which construction work is carried out.
- For laying the first two rows, fire-resistant fireclay bricks are used. To connect the bricks, a special masonry mortar is prepared. It is not recommended to use the mixture prepared for arranging the foundation.
- After completing the laying of the 1st row, the angles are checked, each of which must be 90 degrees. From the 2nd row, the arrangement of smoke exhaust ducts begins.
- To improve the thermal output of the device, it is recommended to install 4 cleaning channels - in the rear, in the vent and on the sides. Cleaning sizes are selected on an individual basis. At this stage, the horizontalness of all surfaces is checked using a corner.
- From the 2nd row an ash pit and a ash pit are formed. These working chambers are designed to clean ash and create the necessary draft for combustion. The brickwork is done in a checkerboard pattern with a 6 mm thick seam. To fix the bricks, a solution based on refractory clay is used.
- Next, partitions for the internal compartments are installed, and a wall is formed between the blower and the working part of the furnace.
- When laying the 5th row, a grate is installed, the thickness of which is determined by the degree of fuel loading of the chamber.
- Up to the 16th row, the laying is carried out similarly to the previous rows.
- From the 17th row, a cap is installed, after which you can begin arranging the second chamber located above the first. It will be the second cap. At this stage, the hood is overlapped, and on the 21st row, passages are arranged, which are directed along the internal walls on both sides.
- The work is carried out in accordance with the proposed order until the 26th row, after which the upper part of the cap is securely covered with brickwork.
It all starts with the construction of the foundation. It should be unconnected to the main foundation of the bathhouse. Its size is 10-15 cm larger than the expected size of the stove. The height of the foundation for the stove is selected based on the height of the foundation of the bathhouse: they must end at the same level.
Waterproofing (roofing felt, roofing felt) is laid on top of the finished base for the stove in two layers. The floor around the future furnace must have a fireproof coating. There are options: these are metal sheets, ceramic or porcelain tiles, natural or artificial stone, brick, etc.
To determine the required amount of bricks for building a kiln, we count the number of bricks in the first row of the order, multiply by 0.8 (the average fill factor of the rows) and by the number of rows.
This amount of brick is definitely enough for the stove, even taking into account broken bricks and rejection. For brick pipe you need to add 4-6 bricks per row.
When installing the grate, technological gaps of 7 mm are observed between the grate for the grate and the outer wall of the stove. The grille is installed at a slight angle relative to the door.
The firebox door is also installed here. When arranging the combustion chamber, it is additionally lined with fireclay bricks, which are laid edgewise. This provides reliable protection external walls of the furnace from exposure to high temperatures.
- 24 hours after completion of the masonry, you can test run the stove with the addition of a small amount of fuel material. This will allow you to check the finished structure for tightness and absence of gaps between the bricks.
- If even minor deficiencies are discovered, they must be corrected immediately.
- One more rule must be strictly observed - protrusions from fireclay masonry should not fit into recesses from ceramic masonry, and vice versa. Thus, we get a completely independent firebox.
The firebox is made of fireclay bricks, and the body of the stove is made of ceramic, which means that they behave differently when heated and cooled. Therefore, the firebox itself must be floating; for this purpose, a special dry seam is made around it.
This is done so that different physical characteristics fireclay and ceramic bricks did not tear during use.
“Dry joint”: between the fireclay and ceramic bricks, the masonry mortar must be removed, and mineral cardboard must be inserted into the resulting void.
Features of operating the furnace
The first is the automatic fuel combustion mode.
In a conventional stove, when lighting, it is recommended to open the blower to its maximum width in order to create greater draft in the stove. Then, as the fire in the firebox intensifies, the door is gradually closed so that the flame temperature decreases slightly and the heat is transferred to a greater extent into the room.
In bell-type furnaces, manipulating the doors and furnace valves does not make sense. The combustion intensity is regulated by the ratio of the volume of the hoods and the combustion chamber. This happens automatically, you just need to light the fire and lay required quantity firewood or other fuel.
The second thing that pleasantly surprises is the absence of the need for daily cleaning of the ash pan.
Any flammable material burns completely in the oven, without any solid residue. Almost no soot is formed on the walls of the furnace: as a result of pyrolysis, carbon is oxidized to the state of carbon monoxide (and partially carbon dioxide).
A chimney damper that is not tightly closed will not lead to the furnace cooling: hot gases will remain in the dome until they give up all the thermal energy to the bricks.
In summer mode, Kuznetsov’s stove turns from a heating and cooking stove into a cooking stove. To do this, it is enough to open a special valve (it is called the summer valve), after which the flue gases will enter the chimney directly, bypassing the caps. Accordingly, only the hob will be subject to heating.
The temperature inside the cooking chamber can be regulated by a valve installed on the exhaust duct extending from it. By closing the valve and the chamber door, it can easily be turned into an oven. For ease of use, shelves for baking sheets can be fixed in the walls.
If you need to quickly warm up the room or dry out, open the door of the cooking chamber. At the same time, the temperature on the burners remains high enough for cooking.
The principle of bell-type stoves was known for a long time, but it was developed in detail and adapted for the construction of home heating devices thanks to the famous stove maker and inventor Igor Viktorovich Kuznetsov. It has become widespread not only in Russia, but also abroad.
What is this article about?
Operating principle of the furnace
Most furnace designs operate by directly heating the walls from the combustion of fuel in the combustion chamber or by heating the brickwork from furnace gases passing through a complex system of air ducts in which hot furnace gases give off heat to the brickwork.
In the first case, the heat capacity of the furnace is determined by the thickness of the walls. The thicker they are, the more heat-intensive the oven will be. Their disadvantage is the high fuel consumption for warming up. As soon as the combustion stops, the stove begins to cool down.
Furnaces with a complex air duct system allow the “body” of the heating structure to be heated more evenly, but the long passage of furnace gases through strongly curved air ducts places increased demands on the draft and height of the chimney.
Bell-type furnaces are free of these disadvantages due to their design, in which two independent heat-accumulating circuits are formed. The inner, highly heated contour of the cap is located inside the outer, less heated contour. Therefore, cooling in the absence of direct contact with outside air occurs much more slowly. The oven stays warm much longer. All heated furnace gases remain inside and are not released outside.
Types of bell furnaces
I.V. Kuznetsov developed more than one and a half hundred oven models that can be used for a variety of purposes.
Moreover, their configuration and dimensions may vary depending on the location of the caps. Usually, in in order to save space occupied oven, the hoods are positioned vertically. On top of each other. But they can be positioned horizontally. In this case, the stove turns out to be low, but long.
On it, in the public domain, there are several dozen of the most common and universal ovens for all needs. From simple heating ones to special bread ovens, surpassing in their functionality the now popular tandoors or Pompeian ovens.
The operating principle of Kuznetsov’s devices takes into account the natural properties of hot air and gases released during fuel combustion. The design of a brick stove is different in that the smoke is contained within the oven itself. For this purpose, a so-called hood is equipped - a combustion chamber, which is a closed dome, into which the hottest air rises, displacing the cooling air through the lower side outlet.
Photo 1. Diagram of the Kuznetsov bell furnace, showing the features of the movement of gas flows in the device.
The ventilation hole under the bottom of the firebox provides constant influx cold air. Due to the fact that hot air is retained in the stove for as long as possible, the heat transfer efficiency increases three times compared to other similar devices.
Designers also tried to achieve such results in the case of traditional stoves - for this purpose, models with a system of chimney ducts were developed. In them, hot air is also retained inside the device, but the chimney lengthens naturally worsens the hood, so the heating efficiency does not increase much.
In the case of Kuznetsov’s devices, the draft is not disrupted, and hot air is not retained by increasing the length of the channel. It's happening due to the natural properties of hot gases to rise and displace colder ones. The dimensions of this type of oven may vary depending on required power and the area of the room that needs to be heated. Models with one hood are usually compact and suitable for arranging a small country house.
Double bell oven
The most common option for high-quality heating of a private home is the Kuznetsov device with two hoods.
Its efficiency is much higher due to longer retention of hot air.
Heat-resistant brick hoods are located one above the other with a slight offset - the air displaced from the first hood immediately enters the second, from which it then goes into exhaust pipe.
The size of such a stove is directly dependent on the area of the house; it is even possible to build with an internal volume up to 5 cubic meters m. The firebox usually occupies the entire base area, this helps to increase the heating power of the air in the furnace.
Reference. In the design of a two-bell furnace, special valves are often installed to insulate the second bell and reduce the heat transfer of the device. This is necessary in more warm time year when no longer required high power heating
When using dampers, hot air from the first hood is directed directly into the chimney.
Heating and cooking version of the device
A feature of this design will be the changed location of the first cap - it is made protruding and a hob is installed in its arch, most often made of cast iron.
The stove must be solid, since due to the design the smoke is not drawn out of the hood, so it will inevitably enter the room through the split burners.
Sometimes a stove is installed above the second hood - it does not heat up so much and cannot be used for cooking, but it will be an excellent tool for drying vegetables, fruits, mushrooms and herbs. There is often a niche for storing logs and drying them before use.
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With bread chamber
This option is almost no different from a standard heating and cooking stove, but additionally equipped with an oven, mounted in the space of the first cap. The chamber is usually made of cast iron or especially strong steel, and the inside is lined with fireclay bricks to provide a gentler heat for baking.
In addition to the bread chamber, they often install water heating tank- The area of the second cap is also suitable for this. Depending on quantity additional functions The size of the furnace will increase and it will require higher fuel costs.
Kuznetsov stove for a bath
According to the principle of operation, the sauna stove does not differ from the options described above. But still she has several features:
- built into the bottom cap of the device pallet with stones;
- the device has access for water And steam outlets;
- has thicker walls for maximum heating of the stones and to avoid overheating of the room.
Furnace drawings
Photo 2. Drawing and arrangement of the Kuznetsov two-bell furnace. The device is presented in whole form and in section.
Photo 3. Drawing of the Kuznetsov bell furnace. The device is also equipped with a chimney duct system.
DIY construction, arrangement of the device
Before undertaking work, it is necessary to correctly calculate the design of the device, For this, the following factors are taken into account:
- Furnace power- depends on total area premises and the quality of its thermal insulation.
- Number of caps— in Kuznetsov’s furnaces they are often made three or more, which significantly increases the heating efficiency, requiring almost no extra fuel consumption. Only changes in the massiveness of the device are taken into account.
- Main function of the oven— will the device be used only for heating or will it need additional features: cooking, heating water.
Photo 4. Step-by-step order of the Kuznetsov furnace. The finished device is also shown from different angles.
A common option for construction is a two-bell stove with a hob. It is functional with fairly compact dimensions and is well suited for placement in small spaces. country houses.
Materials
A very high temperature develops inside the hood area, so only fire brick And fireclay clay with fine sand for masonry mortar. It is often recommended to replace a homemade mixture ready-made mixtures from construction stores - this reduces the risk that the cap will crack during operation and lose its seal.
For laying outer walls and upper tiers, ordinary ceramic bricks with a density of M150 And cement mortar.
When working, we must not forget that laying ordinary and fireclay bricks in one row is excluded - they have different expansion rates and the masonry will collapse during operation.
In addition to masonry materials, you will need to purchase additional elements — metal corners, doors and hinges, valves, hob. All this is available for purchase in specialized stores. You will need reinforced wire to bind the masonry.
Tools
For all types of work you need to prepare a set of tools in advance:
- a container for preparing the solution and a shovel for mixing it;
- stove hammer-pick for breaking bricks;
- Bulgarian with cutting disc on stone;
- pliers and metal scissors for cutting wire;
- trowel for applying mortar;
- leveling rule;
- protective gloves and glasses.
To check the correctness of the masonry you will also need various measuring instruments : roulette, building level, plumb lines, cords, etc.
Preparing the site
The construction of a brick kiln always begins with the foundation equipment. Under Kuznetsovka foundation will do standard type— depth half a meter and with sides extending beyond the perimeter of the future masonry on 10 cm. Operating procedure:
- The pit is being prepared, the bottom is 15-20 cm covers the drainage - a layer of sand and broken gravel.
- Place on well-compacted drainage wooden formwork, protruding above the surface by 20 cm.
- The foundation is poured with concrete mixture and left to harden.
- After laying the foundation correctly, a flat platform is obtained that protrudes above the floor surface by 10-15 cm(depending on shrinkage).
Base surface closes layer of waterproofing(roofing felt works well), then lay reflective layer metal industrial foil. In the case of building a blacksmith shop, the heat from the furnace will be stronger than from conventional appliances, especially in the lower tier, so the foundation is protected from overheating.
The walls adjacent to the future location of the device are closed thermal insulation material, it is recommended to place a metal sheet on the floor in front of the firebox to avoid the risk of fire from falling coals. The location of the chimney is calculated in advance - it is not recommended to place it near the ridge of the roof.
Carrying out masonry
After the foundation has been prepared, Work begins on the construction of the device itself:
- Mix the solution in the prepared container- before starting work, the clay is soaked for two days. In addition to a shovel, using a construction mixer will be effective for mixing.
- When performing masonry, it is recommended Each row must first be placed on a dry surface to precise definition brick cutting sizes. The first row of the base is made solid.
- Starting from the second row the ash pan is laid out, and then the area of the first hood. Hinges for the combustion door are installed as necessary. Every third row The masonry is tied together with wire, the cut pieces of which are placed in the solution.
- Interior fireboxes laid out with fireclay bricks, external- ordinary ceramic. There is no binding solution between these layers, leaving a small gap. Bricks from two rows should also not protrude or intersect with the adjacent layer.
- Inside the arch of the first cap, on supports made of fireclay bricks, a cast iron cooking surface, which is hermetically fixed with a solution.
- After completing the arch first cap, laying out the base for the second begins with a slight offset ( to the width of the hob).
- Gives his best second cap, chimney column, valves are installed to isolate the second level in the summer.
After laying out the top and installing the chimney pipe, the finished stove is left to dry, which takes at least a month. First two weeks the device is dried with the windows and doors open, starting from the third week They carry out gradual heating, increasing the volume of fuel until it reaches a full load.
Possible difficulties
The masonry of the blacksmith is somewhat specific, therefore In the absence of experience, mistakes are often made:
- There is no gap left between the firebox walls and the outer walls— fireclay brick expands when heated, so it can destroy the masonry.
- No wire is used to bind the masonry- due to the greater degree of heating, the walls of the furnace may crack.
- No gap left when installing metal parts- also leads to expansion of the metal under strong heating and the appearance of cracks.
- Incorrect warm-up will disrupt the drying process of the masonry and lead to deformations and cracks.
- Proper thermal insulation is not carried out walls and ceilings (at the location where the chimney is installed) - due to the high heating temperature, the risk of fires when using a blacksmith is higher than with a simple stove.
Thanks very much high temperatures inside the combustion chamber, most of the ash and soot burns out, allowing the frequency of cleaning to be reduced.
One of the advantages of blacksmithing is the ability to choose any available on at the moment solid fuel: firewood, dry pieces of peat, sawdust.
With minor design changes, it is possible to install a heating system with gas or electricity. It is possible to connect the stove to a water circuit, which will allow high-quality heating of remote rooms. An undoubted advantage would be the relatively low cost of materials, the ability to complete all stages of work independently.
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For more than 50 years, Kuznetsov furnaces have held high positions among heating structures for the home, and this is not surprising, since stoves have many advantages and are strikingly different from duct stoves not only in appearance, but also in their characteristics. Kuznetsov was the first person who dared to test the most practical and convenient stove system.
In all ovens, hot air moves through channels, and as it passes through them, the walls of the oven heat up, but the air itself quickly cools down. Such air movement can only occur if there is optimal draft, that is, forced, but in this case the furnace body heats up unevenly, which leads to cracking of bricks and the appearance of unwanted cracks. Thanks to Kuznetsov, an independent principle of air movement in the furnace arose. The stoves have a second name - dome, which they acquired due to their unique design.
The hoods of this furnace must certainly communicate with each other using a dry seam - a space of 2-3 cm that is not filled with a solution and a heat insulator through which gases pass from one hood to another. If we talk in simple language, then the operating principle of Kuznetsov furnaces is as follows: gases circulate and pass through the pipe thanks to own strength gravity, and not forcefully, as happens when moving along a chimney.
In channel furnaces, the smoke is pulled through a pipe, but in a bell-type stove it is pushed out. In this case, the cap can serve as a container for heating water or serve as a place for cooking. Even the simplest dome stove can perform double duty.
The figure below shows in detail the principle of gas movement in a Kuznetsov bell furnace.
Red arrows clearly show how hot air moves, and blue arrows indicate the movement of cold air that enters the oven from the outside through the ash pan. Due to the fact that the weight of cold air is greater than that of hot air, it will not be able to rise up and will go down without affecting the overall temperature regime in a cap. In turn, hot air collects under the hood, gradually cooling there, and then it will be displaced by gusts of hotter air that rise upward.
Advantages, disadvantages and differences
The advantages include the following characteristics:
- Possibility to fire the stove with different fuels
- Uniform heating of the walls
- Good heat dissipation
- When burning, no smoke or soot is released
- The need for cleaning the oven is minimal
- The stove does not crack
- Keeps warm well
- Shape and design can be completely different
- Saving on fuel
- Possibility to light the stove even with raw wood
One of the main distinguishing qualities of Kuznetsov furnaces is their increased efficiency. In an ordinary Russian stove it is 30%-40%, and in these stoves it is almost 95%. This is what distinguishes these stoves from ordinary Russian ones. The internal concept is thought out in detail and competently, due to which the heated air is retained in the stove for more long term, and the cold one, on the contrary, quickly exits into the chimney due to a special recess. It is also worth noting that Kuznetsov stoves can be heated with various types of fuel, even such low-grade fuel as sawdust, on which equipment that provides hot water supply can be installed.
Kuznetsov was the first in the world to use automatic distribution of thrust across channels, which eliminates waste even with an open view. This system distinguishes Kuznetsov furnaces in that it is unique and simple. In stoves of this design, heat is not wasted, but immediately begins to work to heat the room or hot water supply, since the released gases do not swirl into a vortex, as in duct structures, but give up their energy to impregnate the stove.
If in channel furnaces the remaining fuel masses simply “fly out” into the chimney, then the Kuznetsov bell furnace is designed differently. When there are few fuel masses left and they begin to burn out, the hoods act as a storage device, trapping heated air masses under their arches and transferring all the energy to the walls of the stove.
Among the shortcomings, of which there are not so many, are the following:
- It is necessary to carefully follow the order so that the design turns out to be of high quality.
- During production it is necessary to use only high-quality materials.
Types of furnaces
All Kuznetsov models are bell-type, but they also have various classifications. Today, several types are known:
- Bell furnace - has one bell.
- Double hood - two hoods.
- Dome - in this type of stove there can be several hoods. Dome stoves are used more often than others, since they can be designed to suit any room and be supplemented with any devices.
- With a water heating boiler - it is possible to install additional equipment for such stoves.
- With a stove bench - this is a stove on which there is a place for lying.
- OVIC heating and cooking stoves - such stoves not only heat the house, but also make it possible to cook on a specially designed stove.
- The oven-oven not only heats, but is also equipped with an oven in which you can bake.
- A fireplace stove is an ideal option for warming up your home and spending the evening near the fire.
- Two-story stoves are stoves that can perform several functions at once. For example, to heat a room, serve as a hob, have a bed and an oven. The only disadvantage that Kuznetsov’s two-story bell-type stove has is its bulky dimensions. Such a stove will ideal options for large rooms.
- Russian RTIK stoves - in addition to heating and hob, the stove is equipped with an additional one on which you can dry firewood or shoes.
- Outdoor ovens are more like outdoor units, as they include a grill and barbecue for outdoor cooking.
The models listed above are not the entire list of furnaces for various purposes, which were developed according to Kuznetsov’s designs. There are also many drawings with which you can make mixed versions with different functions. In addition to stoves, fireplaces and stoves for saunas are also made using Kuznetsov’s designs. These structures have increased heat transfer, which allows you to quickly heat the room.
How to do it yourself
Most often, heating and cooking stoves OVIK 5 are used in homes; we’ll look at just such a stove as an example.
To make a Kuznetsov stove with your own hands, you will need the following:
Material
- Two types of bricks: solid red (M150) and heat-resistant fireclay (ShB-8)
- Sand and cement (3:1), but you can also take a ready-made factory mixture
- Furnace components: cast iron doors, ash chamber, doors for cleaning holes, valves, grate and views
- Wire with a diameter of 3 mm and a length of 10 m. Bricks will be tied with it
- Steel corners (2 pcs.)
- Reinforcing mesh for the foundation
Tools
- Trowel
- Hammer
- Trowel
- Joining
- Basin or bathtub to mix the solution
- Roulette
- Plumb
- Level
- Drill with mixer attachment
- Bulgarian
Foundation
Before building a stove, it is necessary to prepare the foundation. With him bookmark You should be careful and do everything exactly according to the instructions, otherwise the foundation will settle under the weight of the stove, and the stove may crack, which will subsequently lead to collapse.
The foundation should be 15-20 cm larger than the oven parameters. Only in this case will it meet all regulatory requirements.
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To make a foundation for a Kuznetsov stove with your own hands, you will need to do the following:
- First of all, we dig a pit at least 1 m deep; it is at this depth that the soil freezes in winter. The edges and walls of the pit must be made as smooth as possible, which will allow you to spend less cement mortar.
- Next, we make a so-called “pillow” of sand. It is advisable to add sifted sand so that it compacts more tightly. The height of the pillow should be about 20 cm. Then we leave the pillow for a couple of days to shrink.
- Next you need to make the formwork. The best option There will be boards for the formwork, although other material can be used. The upper part of the formwork must coincide with the floor level in the house.
- Next we move on to the installation of fittings. A mesh with cells from 50 mm and a rod thickness from 6 mm is suitable as reinforcement. The mesh must be positioned so that it is either in the middle of the foundation or before the concrete emerges from the soil. The last option is the most optimal.
- The final stage of the foundation is pouring concrete. In addition to concrete, you can add heavy mineral impurities or gravel to the composition, and the best addition would be a water repellent, which will not allow moisture to be absorbed into the foundation and will extend its service life. After the concrete is poured, its surface must be leveled with a spatula and all defects on the surface must be immediately removed.
After completing the above work, the foundation should be left to dry for some time. Ideally, for at least 30 days, depending on weather conditions, but it hardens within a week, so you can begin further construction of the furnace.
Let's move on to construction. Since the bell furnace is considered the most common design, this is what we will do. Before laying, you need to pay attention to important points:
- Before the first laying, a waterproofing layer must be laid on the foundation, which can be roofing felt or foil-coated isothermal film. If foil is placed, it should be placed with the shiny side up so that it reflects thermal energy.
- You should not make changes in the order, as this may affect the operation of the stove and its service life. An exception can be made only in rows of continuous flooring and their appearance can be changed.
- To make the front side look solid, you need to take bricks good quality, smooth and without cracks.
- If you need to cut a brick, you need to do it with a grinder; the edges and planes must have an even shape.
- The first two levels need to be laid with fireclay bricks using oven bonding mortar. The refractory layer will not allow thermal energy to escape into the foundation. From the second row you need to start preparing the ash pan and the blower. Bricks must be laid in a checkerboard pattern and only on clay mortar. It is also necessary to observe the thickness of the seam, which must be at least 5 mm.
- In the third row we begin preparing the trajectory of the smoke channels.
- To make the stove easy to service, you need to make four standard size cleaning doors in the chimneys.
- The grate for the grate must be placed on the fifth level; also at this level the partitions between the blower, hood and firebox are laid.
- From the 5th to the 14th rows the combustion chamber is laid out from fireclay bricks. It is important not to forget about very important factor: there must be a compensation gap between the fireclay and red bricks of the masonry. It is needed so that the furnace is not damaged by thermal expansion of the material.
- The doors of the firebox and vent must be installed using an asbestos seal.
- In the 17th and 18th rows, the hood overlap has a continuous plane, without holes for the chimney.
- As you can see in the order, in row 21 there are two passages left, which are located along the inner walls.
- In rows 28, 29 and 30, you can make slight deviations from the order if you want to change the shape of the oven. In the case of low ceiling fireproof cuts should be made.
- As you lay out, you should line the inner surface of the brickwork. It is necessary to smooth the joints with a solution, adding heat-resistant material to it.
- The overlap must be carried out with 2 cast iron supporting corners, the length of the arm of which must be at least 45 mm, however, the exact size should be selected taking into account the load.
When constructing Kuznetsov furnaces, significantly less building material will be required than for channel furnaces, since dome structures contain more empty space inside. For this reason, the stove can be considered as an economical option, and the shape of the structure can be completely different, including angular.
Before making a Kuznetsov stove with your own hands, you should carefully study the procedures and not deviate even a centimeter from them, otherwise the correctness of the design may be violated. Also, do not forget that you should choose high-quality and reliable material, which will meet all safety standards.
Do-it-yourself Kuznetsov sauna stove
The 1st row must be laid so that its surface is level, which can be easily checked with a level, and the shape must be in the form of a rectangle.
As already mentioned, in the 2nd row the first cap and air vent will begin. To do this, you need to take a brick, divide it in half and place each part so that they are pushed out slightly, as shown in the figure. There is no need to use a solution. After finishing the masonry, these halves are pulled out.
The 2nd row will require 14 bricks, and after the bricks are laid, you need to install the blower door, which needs to be supported with several bricks. We wrap the frame with cord, as stated in the recommendations. It must be fixed with wire, which must be placed in the seams. Wire is also used to reinforce the walls of the furnace, which must be laid in every even row.
We lay out the third row, in which the bricks included in it should secure the blower door well.
The blower door in the 4th row should be covered with hewn ceramic bricks, which should look outwards, and hewn fireclay bricks, which should look inwards. There should be a thermal gap of 5 mm between them. To create a gap, you will need a spacer made of corrugated cardboard packaging. Such a gap must be made in all places where two types of brick intersect.
In the fifth row, the fireclay bricks that form the side walls of the firebox must be slightly moved so that the bricks of the bottom row form a shelf, the width of which must be at least 15 mm. This is needed for the grate. In the same row we begin to form a vertical channel that connects both caps. After the row is completely laid out, we install the grate and fill the gaps between it and the brick with sand.
When laying the sixth row, the firebox door is also installed. An asbestos cord is laid between the door frame and the brick, and it is secured at the bottom with wire, and at the top with an iron strip.
When laying the seventh row, a gap of 30 mm is left in the assembly from the brick forming the rear wall of the firebox - this is the beginning of a dry seam.
Following the diagram, lay out the eighth row.
In the ninth row, a channel is formed that connects the firebox with the lower hood. On the diagram lilac color those bricks in the side walls of the firebox are highlighted, the upper edges of which should be 10 mm below the plane of the row.
When laying the tenth row, do not forget that ceramic bricks are laid without mortar on the asbestos lining that covers the fireclay brick. You need to make a cutout for the hob in the ceramic bricks surrounding the firebox. The size of the cutout should be such that there is a gap of 5 mm around the slab. At the point of contact between the fireclay brick and the panel, a gap of 10 mm should be left. Such bricks, cut at an angle, are located on the right and front, and are indicated in yellow in the drawing.
The walls of the cooking chamber begin in the eleventh row, and the door for the chamber is installed in it. Don’t forget to wrap the frame with asbestos cord and secure it tightly with wire.
From rows 12 to 14 we lay the bricks according to the order.
After the laying of bricks in the 15th row is completed, the cooking chamber is covered with a sheet of steel, the thickness of which should be 3 mm, and the size 60X55 cm, with a cutout for the exhaust duct. To strengthen the sheet, we use 4 pieces from the corner and a steel strip.
The 17th row is done in order, and in the eighteenth we begin to form the upper cap.
From rows 19 to 27 we place the oven in accordance with the order. In the 28th row we begin installing the main chimney damper. Here, too, you will need to leave a gap of 6 mm around the valve, and the depth under it should be 11 mm.
After the masonry is completely completed, the stove must be left to dry for some time, and the heating must begin with a small amount of firewood.
The bell-type sauna stove has also gained considerable popularity, as it heats all the main sauna rooms and has good heat transfer with minimal fuel consumption. Kuznetsovsky two-tier sauna stoves simple and effective. The problem of heating water in the shower is easily solved by using a register built into the stove.
If you decide to make a Kuznetsov stove with your own hands, then it is worth exploring several options for procedures that will help you make it correctly and in accordance with safety measures.
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Kuznetsov's stoves are well known not only to stove makers - they heat many homes in Russia and abroad. I.V. Kuznetsov has been working on improving furnaces since 1962 and has gathered around him a strong team of like-minded people. The team has more than one and a half hundred developments to its credit, covering almost the entire range of household stoves, see fig.
Many would like to build one of Kuznetsov’s stoves with their own hands, and this article will help them. But we are not going to reveal some hidden secrets of the “blacksmiths” - they simply do not exist. On Igor Viktorovich’s website stove.ru, those interested will find a huge array of stove information for free: from information on the design and construction of stoves to detailed drawings and recommendations for installing a stove in a house and constructing a blind area around a building with stove heating. We also do not intend to criticize or correct anything in this home-stove encyclopedia: we are, to put it mildly, far from I.V. Kuznetsov in the oven business.
The purpose of this article is to provide a kind of introduction to Kuznetsov’s body of information, allowing one to more freely navigate the source material. Let us explain with an example why this is necessary.
Let's say I'm a generalist auto mechanic with extensive experience and want to pass it on to others who are interested. A car is a complicated thing. If I begin to get distracted along the way, explaining in detail that how running and caster (let’s assume that readers are not exactly dummies, now everyone drives) affect the handling and directional stability of the car, and the valve timing diagram affects fuel consumption depending on road conditions. conditions, and so on in the same spirit, I will eventually become confused to the point that I myself will no longer understand how the car I drive works. Willy-nilly, I will have to present the material, albeit “on the fingers,” but in a professional, fluent manner.
However, it will be a little difficult to read even for specialists like me, but for an amateur it will make his head spin. Therefore, I will need someone to help me, who can be called a “half-teapot”. In fact, he is not a kettle at all; he can adjust the suspension and set the valve lifters himself. But in this case, his task is to describe how the entire filling of the car is assembled into one whole, controlled according to the principle: “steer with the steering wheel, gas with the gas, brake with the brake.”
In the automotive industry of the USSR, a similar situation arose in the late 50s and early 60s, when the industry began producing cars for wide sale to the public. Then the super bestseller of that time, “How a Car Works,” was published. Edited by none other than the most important designer of the legendary “Victory”, A. A. Lipgart.
Information “from the recipient” will not yet allow you to start working: it does not provide deep knowledge that will allow you to at least intuitively estimate the required values of numerical parameters along the way. But it is essentially fundamental: mastering it, a professional text can be read with understanding and faster. And, if somewhere in it something is still unclear, it no longer causes loss and wandering, but simply a mark in the mind: this is what you need to find out in more detail.
The government has not yet adopted any landmark resolutions on stoves and stove heating. But their role in household heat and power engineering in times of energy shortage is undeniable: already a heating stove with an efficiency of 70%, when used on a large scale, will provide fuel savings on a national scale, because The designs of new heating plants include heat losses in the mains of 35%, and it is not yet possible to reduce them. So, with the popularization of stove knowledge, you have to get out of it yourself, without being either Lipgart or Kuznetsov. Well, let's try.
Why blacksmiths?
But is it worth focusing specifically on Kuznetsov’s stoves? Worth it because they are worth it. From the very beginning, Igor Viktorovich considered it not as a protected relic of the past or an expensive luxury item, but as an indispensable attribute of the economical energy of the future, which is now the present. The rest realized, as they say, when the roast rooster pecked.
As a result - a 4 kW Kuznetsovka heats a house of 100 square meters. m. just like the branded 12 kW firebox from there. Which, by the way, does not speak about the invention of a perpetual motion machine, but about the fact that branded advertisers are creating their prospectuses, perhaps, sniffing out the “path of happiness.” In any case, it is a fact that Kuznetsov constantly receives orders from the USA, Canada, Sweden, Finland, which themselves are not trailing behind the furnaces. Specifically, the advantages of blacksmiths are as follows:
- High efficiency - 80% is not surprising for Kuznetsov furnaces.
- High temperature of fuel combustion without the use of technologies and materials requiring industrial production.
- As the first consequence of the previous one - omnivorousness. In blacksmiths, any fuel burns to ash, and soot deposition is minimal.
- The second consequence is easy care: because. Soot also burns, Kuznetsov stoves may not be cleaned for years.
- Lower material consumption combined with uniform heat transfer between fireboxes: in a city apartment with central heating, the temperature fluctuates more during the day than in a house heated by a blacksmith with 2 fireboxes per day.
- Wide possibilities for integrating a water heating circuit without compromising the technical parameters of the furnace.
- Good draft with a short chimney, which reduces the cost and simplifies construction and installation work during its construction.
- The plasticity of the design and appearance as a consequence of the two-bell design (see below): without deteriorating the stove, it can be designed to suit almost any room and design requirements.
- Automatic redistribution of thrust among the channels during the transition from heating to cooling, which guarantees against waste: the view almost never needs to be closed; it is intended more for emergency operating modes.
Note: The method of thrust redistribution invented by I.V. Kuznetsov is fundamentally different from the well-known gas view. Through it, the flow created by the draft is passed past the heated parts of the furnace body by special downstream channels, and when the flame burns in the firebox, convection from it pulls the air flow towards itself. As a result, it is not required separate system room ventilation. In addition, the gas view can be blown out reverse thrust when blowing into the pipe, or, conversely, pull out when strong wind, and in a blacksmith’s shop any air flow will pass by everything that it could cool out.
Basics
Most of the advantages of Kuznetsov furnaces come from the principle of free passage of gases. Let us explain again with an example.
Let's imagine a stove with a complex system of smoke ducts: a four- or five-turn exhaust duct. In this cramped labyrinth, strong turbulence will inevitably arise. Have you heard the furnace humming? This is only a minor manifestation of the vortex energy raging within it. And there’s nowhere to get it from except from the fuel stash. If the channels are long and narrow enough, then at first glance there is nothing terrible here: the vortices, by the time they reach the pipe, will dissipate, cooling down, and will still give their energy to the body of the furnace, and it to the room. But in reality, nuances appear, which will be discussed later in the text. Because of them, the efficiency of a channel furnace over 60% is an exceptional rarity.
In a channel stove, while it is being heated, a huge flow of energy rushes about, and only a small part of it can be used for heating or heating water without disturbing its operation. Such a furnace is somewhat similar to a nuclear reactor. Don’t be alarmed, just because of the synergy, i.e. along the paths of energy circulation in it. A nuclear reactor has to be loaded with tens of times more fuel than is necessary to ensure the design energy output. Otherwise, the neutrons will simply fly out without having time to meet the uranium atoms ready to receive them. In a channel furnace, hot vortices, without having time to cool, will fly out into the chimney or, conversely, will cool down immediately, producing smoke and soot.
But the Kuznetsovkas (details below) are closer in synergy to the thermonuclear reactors of the future. “Thermonylus” sounds scary, but this is only due to association with hydrogen bomb. In fact, fusion reactors are quite safe.
Why? Because they generate exactly as much energy as the consumer needs, and the technological power reserve required for rarefied plasma is scanty. If suddenly the chamber of a tokamak or stellarator suddenly completely collapses, the plasma will be completely emitted (there are no heavy atoms in it) and cool down before it reaches the walls of the room. The repairmen will curse - maybe the duty department is sharpening their laces - but after 5 minutes. will be able to blunt to elimination without protective equipment.
So what do Kuznetsov furnaces have in common with thermonuclear reactors? The fact that the energy of the flue gases, thanks to the principle of free passage, does not scroll many times in the flow until it is pushed into the body of the furnace, but saturates it immediately. And now she has nowhere to go from there except into the room and/or the water heating register.
First: cap on cap
The principle of constructing a furnace, which makes it possible to realize the advantages of free movement of gases, has been known for a long time. This is a two-bell furnace, the diagram of which is shown in Fig. Let's start the analysis with his left pose.
The outside air enters through the ash vent 1 into the firebox 2. The firebox can be equipped with a tapering nozzle - a heil - in which a gas view is formed in a single-bell furnace: the light heated gases under the hood with their pressure do not allow the heavy outside cold air to “blow through”, like water into an overturned cup. But in double-bell furnaces, the gas coil often turns out to be unstable due to the draft from the second bell. Therefore, two-bell furnaces were rarely built before Kuznetsov.
Immediately after kindling, when the lightest and most energetic fractions of the fuel burn, combustion occurs in a mode close to the most efficient pyrolysis. In Kuznetsov furnaces - in pyrolysis mode, they are specially designed that way. Pyrolysis gases burn out under the roof 4 of the first bell 3. The under-roof space of the first bell is similar to the afterburner cleanly.
Pyrolysis combustion under the hood it turns out to be self-regulating: if the fuel is very hot, the “cushion” of burning gases expands downwards; the vault of the cap does not allow it to go up. Because of this, the outflow of flue gases is difficult, because it goes down. Accordingly, the thrust weakens and the combustion subsides a little. If the combustion weakens, the opposite happens.
When the combustion transitions to a low-activity mode or the coals are smoldering, both hoods simply work as heat sinks for channel furnaces, collecting residual heat from the fuel. But in the Dutch, it mostly “whistles” into the pipe: according to the well-known hydrodynamic law of Bernoulli, in a narrow channel the flow speed will be greater. And under the hoods, the residual gases will slowly stir until their heat goes into the brick.
Note: in channel furnaces, when there is a strong wind outside, you often have to remove still smoldering coals from the firebox and close the viewer, otherwise all the heat will “whistle” until the fuel burns down to ash. In bell-type stoves, this harmful effect does not exist - the sharp expansion from the chimney into the bell does not allow the wind to clear up in the stove, and you can calmly wait until the fuel gives up its energy reserve to the last calorie.
The ideal two-bell stove is round in plan. Then her body 5 is also the second cap. It also has an invisible thermochemical reaction zone 6 under the vault. It neutralizes carbon monoxide residues ( carbon monoxide) and nitrogen oxides formed in the furnace due to a significantly higher combustion temperature than in a combustion furnace. Chimney 7 only goes carbon dioxide and water vapor.
Although a round one of the usual type can be folded, if it is a two-bell one, it is difficult to install cleaning doors in it, and it is difficult to clean it (one day, yes, you will have to). Therefore, in practice, two-bell stoves are made, if we draw an analogy with electronics, not according to a parallel, but according to a cascade sequential scheme: the second hood is placed on the first and the hoods are connected to each other by chimneys (or one continuous wide gap) from the rear of the stove, right pos. in Fig. In this case, the efficiency of a brick kiln drops by only 1-2 percentage points.
Note: In order for the gas view in a round two-hood to be stable, except for hurricane winds, the annular gap L2 between the first and second hoods must be wider than the same L1 between the firebox and the first hood.
In both cases, a hot water register of any type can be built into the second hood without any fear. The main heat to the furnace body is transferred under the arch of the first hood. This, by the way, is also one of the reasons why two-caps were not used before: with cheap fuel, a small increase in efficiency did not pay for the complexity of the work, and washing in the kitchen in a trough was then commonplace.
And at the same time, the gases fit under the second cap, on the one hand, sufficiently cooled and reacted so that the heat exchanger can be made of ordinary structural materials without fear of its burning out and soot deposition on it. On the other hand, the temperature in the second bell with a furnace efficiency of 80% will be in the range of 200-400 degrees, which provides just enough temperature gradient for efficient heat transfer to water.
About multi-caps
In principle, it is possible to make a round bell-type furnace as a multi-stage one; each cascade - 2 caps, with a hole in the roof and a blank top, as shown in Fig. With three cascades (6 bells), the design, which can be conventionally called a furnace with free flow of gases (left position in the figure), can be made self-adjusting for any fuel, from fuel oil to dung, with an efficiency of up to 97-98% in any combustion mode . However, it cannot be accurately calculated analytically, and computer modeling requires a fairly powerful hardware and software platform.
A furnace with even (with a hole in the roof) caps brought to its hearth (right position in the figure) is, in principle, capable of showing an efficiency of 85-90%, depending on the combustion mode and type of fuel. But both of them, firstly, are very difficult to clean. Secondly, the first cap turns out to be very small, and the temperature under it will be quite pyrolysis, about 1500 degrees. No metal can withstand it, except platinum. Tungsten will burn out like a light bulb with a broken bulb. No one has yet determined experimentally whether the lining for pyrolysis furnaces will hold up in weight.
Note: The black dotted lines in the pictures are not metal structures. These are generatrices (parabolas and straight lines) of the corresponding sizes: the diameters of the smoke holes and the distances of the lower edges of the caps from the hearth.
Video: example of a project for a two-bell heating and cooking stove
Second: thermal load
Nothing works on bare principles. In order for a theoretically absolutely correct stove to heat, dry and cook well, it must also be made correctly in the material. In relation to bell-type furnaces (and especially double-bell furnaces), this means that the thermal load on the material must be high. Making a bell furnace massive, with thick walls, is like lighting a fire in a cave. To feel the warmth, you need to sit next to the fire, and there will be soot...
Take a look at fig. On it are drawings and orders of some Kuznetsov stoves: a double-circuit hot water boiler and an improved Russian one with a stove bench. Not being an experienced stove maker, it is clear that the material per unit of output power (500 W * sq. m of outer surface) in the Kuznetsov stove uses one and a half to two times less than in traditional ones. In general, any bell-type oven is “emptier” inside than a channel oven of equal power.
On the one hand, this is good, bricks are worth the money. But on the other hand, it requires careful development and adherence to construction technology (see below). Thermal load that would not make a pile of cobblestones move, thin brick wall will destroy it already during the accelerating fire.
Structural mechanics are also important for Kuznetsov furnaces. The strength of the wall with clay mortar decreases much faster when its thickness decreases than with cement-sand mortar. Therefore, the foundation for these furnaces must be done especially carefully in strict accordance with the author’s recommendations. They must be strictly followed during construction.
Note: I.V. Kuznetsov allows freely copying his materials for himself, for construction, but objects to republications. However, the pictures in Fig. small. An amateur cannot build anything using them, but a master knows where to get full-fledged drawings. Therefore, we hope that Igor Viktorovich will forgive us this small borrowing for the benefit of the cause.
Third: step right, step left...
High loads on the material in Kuznetsov furnaces require not only careful design development, but also compliance with some fundamental design principles. The main one is a floating firebox made of fireclay grade ShB-8 or Sh-5. The body of the furnace is made of ceramic brick of a grade not lower than M150.
What does a floating firebox mean? Firstly, there must be a dry seam around it entirely, or in places precisely calculated by the author. Making it is not so easy: after laying out the last row of fireclay (unless otherwise specified in the specification for the stove), the clay mortar from the seams between the fireclay and ordinary bricks is picked out, and instead of it, gaskets made of mineral cardboard - basalt, kaolin, etc. - are inserted. .
Secondly, it is necessary to strictly observe the principle of incoherence of modules. What it is is shown in Fig. No protrusions of fireclay should fit into the grooves of ordinary bricks, and vice versa, even with damping joints. TKR and heat capacity of fireclay differ significantly from “brick” ones, and the firebox connected to the body of the furnace will tear the masonry during kindling. The “blacksmith’s” firebox should be a compact module installed in a nest made of ordinary brick. The author explains in detail how to arrange its exit into the chimney on the website.
You must also strictly follow his recommendations regarding the selection and preparation of materials. “Kuznetsovkas”, although made of brick, are high-tech, and tolerate replacement with ersatz and negligence no more than a rocket or submarine tolerates replacement of titanium and composites with tin. The consequences, however, will not be so catastrophic, but you will also have to see them at home, and not read them in the news. And pay out of your own pocket.
In general, in terms of technology: a Kuznetsov stove can be built by a diligent, attentive and careful beginner. But a truly experienced stove maker, half-drunk but thoughtlessly laying out a really very good stove or Dutch oven, will definitely misfire on Kuznetsov’s stove.
About followers
However, “blacksmithing” is not some kind of unspeakable miracle. There have already been many amateurs and professional craftsmen who not only repeat Igor Viktorovich’s original designs, but also create their own. In Fig. on the right is a drawing, and in Fig. in the section - the order of one of them.
She has two features. The first is kindling moves on the 21st row. They are quite similar to Kuznetsov’s idle air passages, but they are included in the work during kindling, speeding up and facilitating it. On a flame or smoldering, their throughput does not allow for the escape of gases, and these channels are drowned out by gas plugs.
The second is sawn along, and even at an angle, bricks in the 17th, 28th and some other rows. In fact, both stove makers and simple builders know that bricks are not sawed lengthwise. But this belief arose at a time when the concept of “angle drill”, aka grinder, did not exist. People only heard about diamond tools back then, saying that they were used somewhere in the secret workshops of military factories.
But it’s still impossible to saw a brick lengthwise with a grinder while it’s in weight; its strength will drop below the minimum limit due to the beating of the tool in your hands. There are two options, the first: install the tool in a frame with a walking vertical plane lever to make it work cutting machine. You can make this yourself, there are ready-made ones for sale.
Another method is suitable if the farm has a circular machine with at least 1500 rpm, and better - 2500-3000. Then diamond wheel the stone is tucked into it instead of the standard toothed saw. This option is preferable: support board with an angle stop provide a much cleaner and more accurate cut. And if necessary, you can finish it on the other side without the risk of getting a high step on the cut.
Video: the process of laying a 3 x 3.5 brick oven
More about round ones
Round stoves theoretically have a lot of advantages, but they are not very convenient in the house. However, there is also a significant demand for compact mobile ovens, and here the extremely high efficiency of round multi-caps can be a decisive factor, because when the size of the oven decreases, its efficiency drops sharply due to the square-cube law.
Such stoves, of course, would have to be made. This solves the problem of cleaning; the stove can be made collapsible. But the choice of metals suitable for the ratio of heat capacity and thermal conductivity is extremely limited. The only inexpensive ones are cast iron, but it is heavy and fragile.
However, there is a lighter and stronger metal material with similar properties. These are products of powder metallurgy. In relation to scissor knives, “powdered crap” is quite justified, but for a stove in which nothing works for shear, powdered parts can be a godsend.
The second problem, which has already been mentioned, is the heat-resistant lining on the arch of the first cap. If it can be solved, then perhaps the works and efforts of Igor Viktorovich Kuznetsov will bear fruit that is more extensive and significant than it now seems.