The jet stove or rocket stove appeared as a result of a deviation from the traditions of manufacturing equipment for heating a room. It is considered an economical heat generator, the design of which is elementary. Therefore, many people are thinking about building a jet furnace with their own hands.
Description, advantages and disadvantages of the rocket stove
A heat generator for heating the air in a room is called a rocket stove or jet stove, since during operation, in case of excessive air supply, it makes special sounds. This noise can be mistaken for a roar jet engine. In normal mode, the equipment operates with a barely audible rustling sound.
A rocket stove serves as a device for heating a home and cooking food. 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 top burning.
The flame from the jet furnace may burst out
The advantages of the rocket stove include:
- independence from fuel energy;
- simplicity of design, consisting of accessible parts, connected in a matter of minutes;
- the ability to provide 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 burns, because the walls of the equipment become extremely hot;
- It is inappropriate to use in a bathhouse, since it cannot be warmed up.
Kinds
A unit that emits a rocket-like hum during operation can be:
- portable (unit from metal pipes, buckets or gas cylinder);
Portable rocket stoves are mass-produced by industry
- stationary (made from fireclay bricks and metal containers);
Such a unit is more difficult to build than a metal furnace
- equipment for heating air with a stove bench.
The bench is equipped behind the back wall of the stove
Portable structures are made in large quantities, because they are used for hiking. The basis of these heat generators is a pipe made up of several sections. True, such structures, unlike units based on fireclay bricks, are not reliable. Walls made of refractory blocks increase the heat transfer of the jet furnace. If desired, you can add a bed in the form of a sofa or bed, decorated with clay or sawdust.
Parts and operation of a jet heat generator
A basic rocket furnace is a device consisting of two pipe fragments connected by a bend 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 fuel is placed in the vertical section of the apparatus, for which a rocket stove 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 operation of a jet stove is based on two actions: the unhindered passage of wood gases through the pipe and the afterburning of gases produced during fuel combustion. Wood chips and firewood are placed in the firebox of this heat generator after a highly flammable material such as paper ignites. A container with water or other contents is placed on the open section of the pipe. At the same time, between the structure and installed capacity leave a small space necessary to create traction.
The processes occurring inside a stationary reactive furnace resemble the operation of pyrolysis heating units
Calculation of parameters (tables)
The volume of the furnace should be determined wisely, because it is it that affects the power and amount of heat generated by the heating equipment. When calculating the dimensions of jet heating equipment, use the indicator of the internal diameter of the drum D, the value of which can range from 300–600 mm. You also need to know the area cross section drum To determine this indicator of the rocket stove, you should use the formula: S = 3.14 * D^2 /4.
The main dimensions of the jet furnace are presented in the table:
| Parameter | Meaning |
| Drum height H | From 1.5D to 2D |
| Height of drum insulating coating | 2/3H |
| Thickness of drum insulating coating | 1/3D |
| Cross-sectional area of the primary chimney | From 0.045S to 0.065S (optimally - from 0.05S to 0.06S). The higher the primary chimney is, the better. |
| Minimum clearance between the top edge of the primary flue and the drum cover | 70 mm. With a lower value, the aerodynamic resistance of the gap for gases passing through it will be excessively large. |
| Flame tube length and area | Length and area of the primary chimney |
| Blower cross-sectional area | Half the cross-sectional area of the primary chimney |
| Cross-sectional area of the external chimney | From 1.5S to 2S |
| The thickness of the adobe cushion under the flue with a stove bench | 50–70 mm (if there are wooden floors under the bed - from 25 to 35 mm) |
| The height of the coating above the flue with a stove bench | 150 mm. It is not recommended to reduce it, otherwise the oven will accumulate less heat. |
| External chimney height | not less than 4 m |
Particular importance is attached to the length of the flue with the stove bench. The maximum permissible values are shown in the table:
The volume of the secondary ash chamber is also an important indicator, depending on the volume of the drum and the primary chimney.
| D (diameter) | Volume | |
| 300 mm | 0.1x(Vk - Vpd) | Where Vk is the volume of the drum, Vpd - volume of the primary chimney. |
| 600 mm | 0.05x(Vk - Vpd) | |
Construction raw materials for the construction of a non-standard furnace
The production of jet heating equipment will require:
- 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 pipes made of steel 2–3 mm thick, which are needed to create a blower, combustion chamber and primary chimney;
- fireclay crushed stone and oven clay as thermal insulation materials;
- adobe, which serves as the 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 lids and doors;
- asbestos or basalt cardboard, which serves as a sealant.
The tools you will need to build a rocket furnace are: welding machine. And if you plan to make heating equipment from bricks, then you will have to take:
- Master OK;
- mortar spatula;
- hammer-pick;
- jointing;
- sharp-angled sledgehammer;
- level;
- plumb line;
- roulette
Preparation for assembling heating equipment
When choosing a location for a rocket stove, follow some rules:
- jet heating equipment is placed only in a room with an area of at least 16 m²;
- Without floorboards under the stove, installation of equipment will be easier;
- It is prohibited to place wooden beams above a structure that produces heat;
- if it is assumed 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 external contour of the house, otherwise the room will lose heated air;
- The jet device must not be placed next to walls and partitions of wooden materials.
To make it convenient to add fuel to jet heating equipment, it is wiser to place it facing the entrance. It is important to leave at least a meter of unoccupied space around the rocket stove.
IN small house builders advise setting aside a place for the stove in the corner. In this case, the firebox should be directed in one direction, and the bed (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 the rocket stove, 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 exposed floor, the bottom of which is necessarily pressed.
Before construction work, a special solution should be mixed. It consists of sand and clay combined in a 1:1 ratio. You will need enough water so that the construction raw materials have the consistency of sour cream, that is, ¼ of the amount of dry ingredients.
Step-by-step instructions for making it yourself
If you plan to make a rocket stove from a gas cylinder, then you don’t have to be afraid of difficulties. The steps to create equipment from such construction raw materials are quite simple:
- the upper part is cut off from a cylinder with a volume of 50 liters in order to build a kind of cap;
The balloon is cut off at the top and bottom
- Based 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 (fuel firebox);
Dimensions in mm
- the space between the two pipes is filled with a material that retains heat, for example, sand, which has been thoroughly calcined, that is, cleared of organic substances;
- To give the structure stability, the legs are welded.
To build a rocket stove with a stove bench, which involves the use of bricks, you need to proceed differently:
- The area for arranging the firebox is deepened by removing 10 cm of soil. The combustion chamber is formed from fireclay bricks. Formwork is created along the contour of the structure being manufactured. To ensure a strong foundation, it is recommended to lay it in reinforcing mesh or metal rods;
The platform will harden in about two days
- The structure is poured liquid concrete. Then they wait for the solution to harden and finish the work. The bricks are laid in a continuous line, creating a platform for the stove. After this, the walls of the structure are formed, placing several rows of brick blocks;
- The lower channel of the structure is constructed, with one line of bricks laid across to block the combustion chamber. The blocks are placed, leaving the vertical channel and the firebox opening open;
Two sectors of the furnace at this stage of construction should be open
- Find the body from the old boiler and cut off the top and bottom covers on it. A flange is installed at the bottom of the resulting pipe through which a horizontal heat exchanger will pass. The parts must be connected to each other with a continuous weld;
Work requires accuracy
- An outlet pipe is inserted into the barrel, after which they take a metal brush and scrape off the 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;
- The horizontal chimney is connected by welding to the side outlet - the future ash pit. To facilitate its cleaning, a sealed flange is installed;
- The fire tube is laid out from refractory bricks. At the same time, a channel 18 cm high and wide is formed inside the structure. When doing this, they constantly use a building level, which allows you to control the verticality of the product;
The height of the pipe is determined in advance
- The flame tube is covered with a protective casing, and the resulting gaps are sealed with perlite. The lower area of the vertical channel is sealed with damp clay, the function of which is to prevent spillage thermal insulation material on the floor;
- From the boiler, on which the top and bottom have been cut off, a fuel tank is formed. A handle must be welded to it;
- 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 over perlite backfill;
- They create the facade of the stove, for which the stove contour is laid out from stone, bricks, adobe and sand. The back side of the structure is filled with crushed stone, and the front side with adobe mixture, making the surface perfectly flat;
- A metal barrel casing is placed on the previously created base. The lower pipe of the container is directed towards the bed. The bottom of the structure is treated with raw clay, which will ensure its tightness;
- A channel made of corrugated pipe is connected to the combustion chamber. It will serve as a link between the firebox and the outside atmosphere;
At this stage the oven looks almost finished
- A test firing of the stove is carried out, watching how the gases are removed from the horizontal chimney. After this, the heat exchanger pipes are connected to the lower pipe installed on a red brick platform;
- The stove is equipped with a smoke exhaust pipe. The junction of the chimney and the heat generator is sealed with fire-resistant coating and asbestos cord;
- Using clay and adobe, the bed is given the desired shape. Only the horizontal section of the structure is left unsealed, which will then be used during cooking.
The oven functions as a whole system
Design improvement
A bench with a gas duct inside is not the only option for upgrading a rocket stove. The design can be improved with a water jacket connected to the heating system in which water circulates. It is advisable to give this part of the structure the appearance of a coil created from copper pipe twisting on the chimney.
This design provides even more heat
Another way to improve a jet furnace is to organize the flow of heated secondary air into the flame tube. This will increase the efficiency of the heat generator, but will lead to the deposition of a large amount of soot in the primary chimney. Therefore, it is better to make sure that the drum cover can be removed if necessary.
Subtleties of operating an unconventional stove
A rocket furnace is heated in a similar way to a top 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 heating the unit must be added only after the structure has been well heated, for which purpose sawdust or paper is first placed in the blower sector and set on fire;
- they must react to the muting of the hum emanating from the stove - they put a large batch of fuel into the combustion chamber, which will ignite on its own from the hot remains of sawdust;
- the process is closely monitored, that is, after laying the firewood, the damper is fully opened, and after some time, when the equipment makes a hum, it is closed to produce a sound similar to a rustling;
- as necessary, the damper is closed more and more, otherwise the firebox will be filled with an excess volume of air, which will disrupt the pyrolysis inside the fire tube and lead to the creation of a strong hum.
Since the jet furnace was originally created for use in field conditions, its design is extremely simple. This allows an ordinary home craftsman to cope with the manufacture of the unit. But, despite its apparent lightness, the rocket stove must be assembled, taking into account the correct ratio of parameters. Otherwise, the equipment will be unproductive.
Today, many types of furnaces have been invented various designs. For most of them, the rule applies: the higher the characteristics of the unit, the more skill and experience is required from the craftsman making it. But, as we know, there are no rules without exceptions. In this case, the destroyer of stereotypes is the rocket stove - a very well-thought-out, economical heat generator with a simple design that does not require any special skills from the performer. The latter circumstance explains the popularity of the “rocket”. Our article will help the reader understand what the highlight of this miracle of technology is and teach how to make it with your own hands from scrap materials.
What is a rocket stove and why is it good?
The rocket stove or jet stove received its impressive names only for the characteristic sound that it makes when the operating mode is violated (excessive air supply to the firebox): it resembles the roar of a jet engine. That's all, it has nothing more in common with rockets. It works, if you don’t go into details, the same way as all its sisters: wood burns in the firebox, smoke is thrown out into the chimney. Normally, the oven makes a quiet rustling sound.
Reaction furnace arrangement option
Where do these mysterious sounds come from? Let's talk about everything in order. Here's what you should know about the rocket stove:
Design advantages
The operating principle of the rocket stove provides the user with a certain freedom in choosing its design. In addition, the unit can be constructed in such a way that only a small part of it will remain visible and, in terms of aesthetics, minimal damage will be caused to the interior of the room.
As you can see, the jet stove has something to brag about. But first of all, stove lovers are attracted by the combination of simplicity of design and good, although not the highest, characteristics when working on waste fuel. These very characteristics are the highlight of the “rocket”. Let's try to understand how we managed to achieve such indicators.
The efficiency of a solid fuel heat generator depends on many factors, but perhaps the most determining factor is the degree of afterburning of pyrolysis gases. They appear due to the thermal decomposition of organic fuel. When heated, it seems to evaporate - large hydrocarbon molecules break up into small ones, forming flammable gaseous substances: hydrogen, methane, nitrogen, etc. This mixture is often called wood gas.
Small rocket stove
Liquid fuel, for example, waste oil, breaks down into wood gas almost immediately and it burns right there - in the firebox. But with wood fuel the situation is different. Decay solids the transition to a volatile product suitable for combustion - wood gas - occurs in several stages, and the intermediate stages also have a gaseous form. That is, we have the following picture: first, a certain intermediate gas is released from the wood, and in order for it to turn into wood gas, that is, to disintegrate even more, it is necessary to prolong its exposure to high temperature.
And the more humid the fuel is, the more “prolonged” the process of complete disintegration becomes. But gases tend to evaporate: in a conventional furnace, the intermediate phase is mostly sucked out by draft into the chimney, where it cools down without having time to turn into wood gas. As a result, instead of high efficiency, we get soot from heavy hydrocarbon radicals.
In a rocket furnace, on the contrary, all conditions are created for the final disintegration and afterburning of the released intermediate gases. In essence, a very simple technique was used: immediately behind the firebox there is a horizontal channel with good thermal insulation. Gases do not move as fast in it as in vertical pipe, and a thick, heat-insulating coat prevents them from cooling down. Thanks to this, the process of decomposition and afterburning is carried out more fully.
At first glance, this solution may seem primitive. But this simplicity is deceptive. Engineers and researchers had to tinker a lot with calculations in order to link the required thrust force with the optimal combustion mode and many other factors. Thus, a rocket stove is a very finely tuned thermal system, when reproducing it it is very important to maintain the correct ratio of the main parameters.
If the manufacture and adjustment of the unit were carried out correctly, the gases will move as expected, while emitting a slight rustling sound; if the regime is violated or the furnace is assembled incorrectly, instead of a stable gas vortex in the gas duct, an unstable one is formed, with numerous local vortices, as a result of which a roaring rocket sound will be heard.
Flaws
One more circumstance should be taken into account. It cannot be considered a disadvantage of the stove; rather, it is an important feature. The fact is that the “rocket” was invented in the USA. And the citizens of this country, where any idea can bring good earnings, are not as willing to share their work as was customary, for example, in the Soviet Union. Most drawings and diagrams that have become widespread do not show or are distorted vital information. In addition, we simply do not have access to some of the materials used in it.
As a result, home craftsmen, especially those who do not know the intricacies of stove making and heating engineering, often end up with a device that absorbs fuel in huge volumes and is constantly overgrown with soot instead of a full-fledged jet stove. Thus, complete information about the rocket stove has not yet become public property and overseas pictures should be treated with great caution.
Here, for example, is our popular jet furnace design, which many are trying to use as a model.
Drawing: how the oven works
Drawing of a mobile rocket oven
At first glance, everything seems clear, but in fact, much remains “behind the scenes.”
For example, fire-clay simply designated by the term Fire Clay - without specifying the variety. The mass ratio of perlite and vermiculite in the mixture from which the body of the furnace (in the diagram - Core) and the lining of the element called Riser is not indicated. Also, the diagram does not specify that the lining should consist of two parts with different function- heat insulator and heat accumulator. Without knowing this, many users make the lining homogeneous, which is why the performance of the furnace drops significantly.
Types of jet furnaces
Today there are only two types of furnaces of this type:
Design of a small rocket stove
As already mentioned, a jet stove is easy to manufacture, so we will consider a full-fledged option.
Design and principle of operation
The stove we will try to make is shown in the picture.
Rocket stove: frontal section
As you can see, its combustion chamber (Fuel Magazine) is vertical and is equipped with a tightly closing lid (prevents the leakage of excess air), as in a top-burning stove (the ash pit is designated the Primary Ash Pit). It was this unit that was taken as the basis. But a traditional top-burning heat generator operates only on dry fuel, and the creators of the “rocket” wanted to teach it to successfully digest wet fuel. To do this, the following was done:
Note. Some readers familiar with the design of pyrolysis furnaces may think that it would be a good idea to supply secondary air to the base of the primary chimney. Indeed, the combustion of wood gas would be more complete, and the efficiency of the stove would be higher. But with this solution, vortices are formed in the gas flow, as a result of which toxic combustion products partially penetrate into the room.
A capacious heat accumulator capable of withstanding such temperatures is fireclay brick (withstands up to 1600 degrees), but the stove, as the reader remembers, was intended for field conditions, so a more accessible and inexpensive material was needed. The leader in this regard is adobe (denoted in the diagram by the term Thermal Mass), but its temperature limit is 250 degrees. To cool the gases, a thin-walled steel drum (Steel Drum) was installed around the primary chimney, in which they expand. You can cook food on the cover of this drum (Optional Cooking Surface) - its temperature is about 400 degrees.
To absorb even more heat, a horizontal chimney with a bed (Airtight Duct) and only then - external chimney(Exhaust Vent). The latter was equipped with a view that closes after heating: it will not allow the heat from the gas duct of the stove to evaporate into the street.
So that the pipe inside the stove could be cleaned from time to time, a secondary ash chamber (Secondary Airtight Ash Pit) with a hermetically sealed cleaning door was installed immediately behind the drum. The main part of the carbon deposits, due to the sharp expansion and cooling of gases, settles in it, so cleaning the external chimney has to be done extremely rarely.
Since the secondary ash chamber has to be opened no more than twice a year, instead of a door, you can use more simple design- screw-on lid with asbestos or basalt cardboard gasket.
Furnace calculation
Before talking about the dimensions of the oven, we draw the reader’s attention to important point. The square-cube law applies to all solid fuel heat generators. Its essence can be explained with a simple example.
Imagine a cube with a side of 1 m. Its volume is m 3 and its surface area is 6 m 2. The ratio of volume to surface area is 1:6.
Let's increase the volume of the body by 8 times. The result is a cube with a side of 2 m, the surface area of which is 24 m 2.
Thus, the surface area has only increased 4 times and now the volume to surface ratio is 1:3. In furnaces, the amount of heat released and its power depend on the volume, and heat transfer depends on the surface area. These parameters are interconnected, so you cannot thoughtlessly scale this or that furnace design, adjusting it to the dimensions you need - the heat generator may turn out to be inoperable altogether.
When calculating a rocket furnace, the internal diameter of the drum D is specified, which, as mentioned above, can vary from 300 mm (15 kW furnace) to 600 mm (25 kW furnace). This “fork” is precisely due to the square-cube law. We will also use a derived value - the cross-sectional area of the drum S: S = 3.14 * D^2 /4.
Table: main parameters
Table: maximum permissible length of the flue with a stove bench
Table: volume of the secondary ash chamber
We calculate intermediate values proportionally (interpolate).
Materials and tools
The furnace drum can be made from a standard barrel with a volume of 200 liters and a diameter of 600 mm. The square-cube law allows you to reduce the drum diameter by up to 50%, so for a small oven this element can be made from a household gas cylinder or tin buckets.
The blower, firebox and primary chimney are made of round or profile steel pipes. Significant wall thickness is not required - you can get by with a couple of millimeters - combustion in the furnace is weak. The chimney in a stove bench, through which gases flow in a completely cooled form, can generally be made from metal corrugation.
For thermal insulation (lining) of the furnace section, you will need broken fireclay bricks (fireclay crushed stone) and oven clay.
The outer coating layer (heat accumulator) will be made of adobe.
This is what freshly prepared adobe looks like
Thermal insulation of the primary chimney is made of light fireclay bricks (ShL grade) or river sand rich in alumina.
Parts such as lids and doors can be made from galvanized steel or aluminum. Asbestos or basalt cardboard is used as a sealant.
Preparatory work
Within preparatory work it is necessary to cut all available rolled products into blanks required sizes. If you decide to use a gas cylinder as a blank for the cap, you need to cut off the welded upper part from it.
Preparing a gas cylinder for use as a hood
Note! If there is gas left in the cylinder, it may detonate during cutting. For safety reasons, such containers are cut only after filling with water.
Note that in most cases, a rocket stove is made from a cylinder. Such a unit is capable of heating a room up to 50 m2. A “rocket” from a barrel only has to be used at full power in very rare cases.
From the barrel, if the stove is made from it, it is also necessary to cut off the top part. Next, two openings located opposite each other are cut out in the barrel or in the cylinder, through one of which the fire pipe will be inserted into the primary chimney, and the gas duct with a stove bench will be connected to the second.
Step-by-step instruction
Here is an approximate procedure that should be followed when making this stove:
Making a firebox
The firebox is welded using steel pipe or sheets. The firebox lid must close tightly. It should be made from steel sheet, around the perimeter of which a strip of basalt cardboard is fixed with screws or rivets. For a tighter closure, the lid can be equipped with a screw clamping mechanism.
This is what the firebox and ash pan look like in a simple rocket stove
The ash chamber (indicated in the diagram as Primary Ash Pit) is separated from the main part of the firebox by a grate welded from a rod with a diameter of 8–10 mm. The grille should be installed on corner shelves that are welded to the inner walls.
The door of the ash chamber must also be airtight. It is made from a steel sheet, to which a steel strip is welded in two rows along the entire perimeter. An asbestos cord or basalt cardboard is placed in the groove between these strips.
All that remains is to weld the fire tube to the firebox.
Primary chimney
Chimney installation
We weld the horizontal part of the chimney to the outlet of the secondary ash pan, on which the stove bench will subsequently be installed. If the flue is supposed to be made of metal corrugation, then first you need to weld a short pipe to the ash pan, and then attach the corrugation to it using a clamp.
On final stage An external chimney is attached to the horizontal flue.
Furnace lining
The metal part of the stove is ready; now it needs to be properly plastered with heat-insulating and heat-accumulating compounds.
The lining of the combustion part (up to the primary chimney) should be done with a mixture of stove clay and broken fireclay bricks, taken in a 1:1 ratio.
Primary chimney lining
Materials used for lining the primary chimney - light fireclay bricks or river sand- are porous, therefore open state they will quickly become saturated with soot and lose thermal insulation properties. To prevent this, the lining on the primary chimney is protected with a thin-walled steel casing, and the ends are coated with oven clay.
In accordance with the square-cube law, the ratio of the volume and surface area of the drum depends on its diameter, therefore the lining of the primary chimney is made differently depending on the size of the furnace. Three options are shown in the figure.
Primary chimney lining options
If the lining is made with fireclay bricks, the cavities between its fragments must be filled construction sand. If river sand rich in alumina is used, you have to resort to more complex technology:
The last step is to coat all parts of the stove with adobe. It is prepared from the following ingredients:
The straw to clay ratio shown is approximate. In some types of clay, more straw can be added, in others, on the contrary, its amount must be reduced.
Ways to improve the jet furnace
Instead of a couch on a gas duct, you can build a water jacket that will be connected to a water heating system. This part can also be made in the form of a coil of copper pipe wound around the chimney.
Scheme of a rocket furnace with a water circuit
Another method of improvement is to organize the supply of heated secondary air to the flame tube.
Drawing of a rocket stove from a cylinder with a secondary air supply
With this design, the efficiency of the stove will be higher, but soot will be more intensively deposited in the primary chimney. To make it easy to remove, the drum cover must be made removable. Naturally, it must be equipped with a seal.
An improved version of the rocket stove from a cylinder
How to fire a rocket stove
A rocket stove, like top-burning heat generators, operates at high performance only if its chimney is hot enough. Therefore, before loading the main fuel into the firebox, the unit must be warmed up well (unless, of course, there has been a long downtime and the stove has had time to cool down). To do this, use any “fast” fuel, for example, sawdust, paper, straw, etc., which is placed in the ash pit.
The subsidence of the hum or a change in its tone indicates that the stove is sufficiently warmed up and the main fuel can be added to the firebox. There is no need to set it on fire - it will flare up from the coals remaining after the burning of the “fast” fuel.
Melt the rocket stove through the firebox
Tune in external conditions and fuel quality, like, for example, Bullerjan, a jet stove cannot. The adjustment must be made by the user. After adding the main fuel, the ash flap must be fully opened, and as soon as the unit begins to hum, close it until a rustling sound appears.
In the future, as the fuel burns, the damper has to be closed more and more, still achieving a quiet rustle. If you miss the right moment, an excess amount of air will begin to enter the firebox and pyrolysis in the flame tube will begin due to the cooling of the intermediate gas mixture will stop. At the same time, the stove will remind you of itself with a “rocket” hum.
Video: how to make a long-burning jet stove with your own hands
They tried to create a jet or rocket stove that was extremely simple and would only benefit the home craftsman. However, as can be seen from our article, it is under no circumstances possible to make this heat generator at random - instead of a rocket, the master will receive an ordinary potbelly stove, very voracious and constantly overgrown with soot. It is important to observe all the given parameter ratios and then you will get a productive rocket stove with quite decent characteristics.
Brick rocket stove long burning, despite the simplicity of the design, can solve a number of problems for owners of summer houses and private houses. These include not only heating and cooking functions, but also the creation of an original interior and comfort in the room.
Collapse
Principle of operation
During the thermal decomposition of solid organic fuel, gaseous substances are released, which also decompose and transform into wood gas during combustion, which has high level heat transfer.
In conventional solid fuel stoves, wood gas goes into the pipe along with the gas, where it cools and settles on the walls in the form of soot. In a rocket-type furnace, due to the horizontal channel, gases move more slowly, do not have time to cool, but burn out, releasing a large number of heat.
In jet models heating devices complex design heated air and gas pass through a series of internal channels. Then they move to the upper part of the body, under hob, where it burns completely. For such a rocket there is no need for additional boost. The draft in them is created by the chimney, and the longer its length, the more intense the upward flow.
Principle of operation
This diagram shows the operating principle of a rocket stove with a stove bench
Advantages and disadvantages
Rocket stoves long combustion have the following advantages:
- high efficiency - at least 85%;
- high speed of heating the room - 50 m² will become warm in less than 1 hour;
- absence of soot - the exhaust during fuel combustion does not form soot, but is formed in the form of steam and carbon;
- possibility of functioning on solid fuel any kind;
- low consumption - the fuel consumption of a rocket stove is 4 - 5 times less than that of a conventional stove under equal conditions: combustion time and heating temperature;
- the possibility of installing a warm bed;
- Duration of heat retention in a well-heated structure without adding fuel - up to 12 hours.
This stove has many advantages, but there are also disadvantages
The disadvantages include:
- manual method of controlling a heating device - fuel burns out quickly and requires regular reporting;
- the high heating temperature of some structural elements threatens owners with burns in case of accidental contact;
- the heating speed does not allow the use of a rocket stove for baths;
- the aesthetic component of such a device is not for everyone and is not suitable for every interior;
- danger of carbon monoxide entering living rooms.
Materials
Do-it-yourself building materials for the construction of a long-burning rocket stove are selected depending on the calorific value of the fuel. For laying the main part of the building, simple red stove bricks are usually used. The firebox and combustion bunker are lined with fireclay bricks.
If you plan to use high-calorie fuel (for example, coal), then refractory bricks are used for the construction of almost all parts of the structure. The masonry elements are fastened with an aqueous solution of a mixture of sand and clay.
Regardless of the type of design for a long-burning rocket stove, you will need to buy stove accessories:
- blower;
- grates;
- firebox doors;
- intermediate cap;
- chimney pipe.
Tools
To build a rocket-type furnace with your own hands, you need to prepare in advance a set of tools for work, which should consist of:
- trowels for scooping and distributing the solution. It is more convenient to work with a tool with the handle moved slightly to the side;
- picks or hammers - picks for trimming individual parts of brick;
- grinders with a diamond blade for sawing whole blocks into quarters and halves;
- mallets with a rubber tip for leveling bricks in masonry;
- twisted cord - moorings;
- building level;
- square and tape measure;
- shovels.
You also need to stock up on two containers for preparing mortar, concrete and metal mesh for sifting ingredients.
How to do it yourself?
Before you make a rocket stove, you need to decide on the location of its installation, the dimensions of the future design, and develop a diagram. The masonry technology itself is quite simple; any novice builder can master it.
The simplest design of a rocket stove can be built from 20 bricks at a summer cottage and used to heat food brought from home.
Selecting a location
Before starting construction, the first thing is to choose a location. Brick kilns rocket type is recommended to be placed closer to front door. In this case, after cleaning, the ash will not need to be carried across the entire room, which will have a positive effect on the overall dustiness of the room.
It is also desirable that at the point where the pipe exits there are no rafters located closer to the chimney than 40 cm. And yet, the stove should not be adjacent to the external wall of the house, so that expensive heat is not lost to heating the street.
Preparation of the solution
Cement mortar will quickly crack under the influence of high temperatures, so for laying heating devices made of bricks, only a mortar consisting of clay and sand is used.
Their proportions are determined experimentally, depending on the quality of the clay. Most often in a ratio of 1:2 or 1:3, and the higher the fat content of the clay, the less it is added to the solution.
First, the clay must be soaked, strained, and then sand must be added. The resulting solution should have a consistency similar to thick sour cream. You can check its viscosity level in the following way:
- place a wooden stick or trowel handle into the mixture;
- remove the tool and shake well;
- check the thickness of the adhering layer: if less than 2 mm add clay, more than 3 mm add sand.
The preparation of the mortar must be approached with all responsibility, since only a plastic mixture of the required thickness can fill all the unevenness of the bricks and ensure their strong adhesion.
Laying a rocket furnace of 20 bricks
Ordering a rocket stove for 20 bricks
Example of a brick rocket stove
Laying a rocket stove with a stove bench
A brick rocket stove, even equipped with a stove bench, has small sizes. The order shown in the figures (below) allows you to assemble the structure without using metal products. Only the doors will be made of iron. Subsequently, the body can be coated with clay to give it a more rounded shape.
| Row No. | Number of bricks, pcs. | Description of the masonry | Drawing |
| 1 | 62 | Forming the base of the furnace |
(click to enlarge) |
| 2 | 44 | Formation of the base of channels for heating the bed along the entire structure. Fastening mortgages for mounting a cast iron door | |
| 3 | 44 | Repeating the outline of the second row | |
| 4 | 59 | Complete channel blocking. Beginning of the formation of a vertical smoke channel and firebox | |
| 5 | 60 | Construction of a bed |
(click to enlarge) |
| 6 | 17 | Continuation of the laying of the smoke channel | |
| 7 | 18 | ||
| 8 | 14 | ||
| 9; 10 | 14 | Formation of a smoke channel |
(click to enlarge) |
| 11 | 13 | ||
| 12 | 11 | Beginning of laying the chimney pipe. This is where the channel begins, through which air from hob will go down to move to the bed | |
| 13 | 10 | Completion of the formation of the surface for the hob. Laying an asbestos pad, which is covered with sheet steel. |
(click to enlarge) |
| 14; 15 | 5 | Closing the chimney channel and forming a low wall between the stove bench and the hob. |
After completing the masonry work, the homemade rocket stove must be dried, carefully, heating at low intensity. First, no more than 20% of the required amount of firewood is placed in the firebox, and the device is heated twice a day for 30 - 40 minutes.
According to this scheme, the stove is heated until its outer surface is cleared of damp stains. Depending on the size of the device, drying may take from three to eight days. During this time, the room should be well ventilated, especially in summer.
Accelerating drying can lead to cracking of the masonry, that is, the device will become unsuitable for further heating.
Finished look
You need to launch a brick rocket stove only when the chimney is warm. For a small device, this property is not so significant, and a larger stove on a cold pipe only wastes firewood.
Therefore, to bake a rocket before loading the fuel quota after a long break in operation, you need to heat it with paper, dry shavings, straw, etc., placing them in a ash pit with the door open. When the hum in the stove decreases in pitch or subsides, then you can load all the fuel into the firebox; it should ignite by itself from the existing fire.
A rocket stove with a stove bench is not a completely self-regulating device for external conditions and fuel energy efficiency. Therefore, at the beginning of the fire with the normal amount of fuel, the ash door is left in the open position. After the stove begins to hum strongly, it is covered until the sound emitted is barely audible.
Only dry firewood can be used to heat the stove; wet wood will not allow the stove to warm up to desired temperature, which can lead to backdraft.
Conclusion
Brick jet kiln is becoming increasingly popular heating device For small buildings both temporary and permanent residence. This is explained by the simplicity of execution, low cost of material, long battery life and high heat transfer of this design.
←Previous article Next article →According to its design, the rocket stove is divided into two main types: portable and stationary. The portable model is used on hikes and while relaxing in nature. Its industrial model called “Robinson” is widespread. It gets its name because it looks like a rocket. The similarity of the image is added by the fact that a flame bursts out of the short chimney during combustion, and a hum is emitted with an unlimited supply of air. Used for cooking, heating a kettle in camping conditions.
Let's consider the principle of operation, based on the above model.
Description of work
- Steel with a thickness of 2-3 mm is used for the structure.
- Has a shape matchbox, without box. A lid and bottom are welded to its side. On the other side there will be a firebox into which firewood is directly loaded.
- At the top, closer to the bottom, a pipe is welded to the box at an angle of 45 degrees. A structure is welded to the top to act as a stand for dishes and a flame divider.
- To prevent the flame from burning the bottom of the pan while cooking. For manufacturing, you will need a piece of pipe, which is cut into three rings, each ring is cut in half, a total of six half rings come out, we weld them with a uniform indentation in the center, the product is welded to the top of the chimney.
- Legs are welded to the bottom of the box to ensure the stability of the structure.
The finished sample with dimensions is shown below in the illustration and diagram.
Principle of operation
- The good thing about this option is that there is no need to build a structure over the fire to hang a cauldron or kettle.
- Cooking kulesh or fish soup will be more comfortable, as in kitchen stove at home. The installation should be oriented towards the wind, it should blow into the firebox.
- The firewood burns out quickly, the heat generated is enough to cook food, but most of it evaporates.
- In the stationary model, these shortcomings are eliminated by improving basic design. Namely, the furnace room is equipped with a door, under which there is a ash vent, which limits the air supply, thereby slowing down the combustion process of wood.
- Air supply is also organized to the area above the combustion, where the gases go, but do not burn there, this makes it possible to start the pyrolysis process, thereby ensuring the afterburning of the pyrolysis gases.
- The fuel combustion chamber should also be wrapped in a casing, which increases thermal insulation. A manufactured thermal insulator is put on it, this additionally traps heat inside, shown below.
Materials
The rocket furnace will require the manufacture of the following Supplies: two gas cylinders and everything that is indicated in the table below.
Let's get started
We cut a piece of 20 cm from the profile, cut the rest into three parts.
From a piece measuring 315 mm, a “lounger” base is made, from a second piece, measuring 300 mm, a place for loading firewood is made and welded at an angle. To do this, we make a cut on the bias.
We cut the third blank, 280 mm in size, across, you get two channels, the one with a width of 35 mm is welded from below, thereby making a ash pan.
On the upper surface of the base we cut out a rectangular hole across the entire width, the length for the hopper with an ash pit, and on the side of the joint we make a cutout for it. The distance from the beginning to the workpiece is 100 mm.
Safety precautions should be observed when cutting; first you need to fill it with water, this will remove the remaining gas condensate.
Blower manufacturing process
At the bottom of the base, opposite the hole, we weld five rods, 16 cm long, from reinforcement. We make slits between the welded grates. Next, we weld another part of the channel (the remainder from the third workpiece) below the grate. We weld on back wall, on which, for the convenience of further installation, there is a bevel and its plug. After you have welded the “working” workpiece to the base, you should weld the bottom with a plug.
Next, we proceed to the manufacture of the casing, which will act as a conductor. We will fill the space between them with mineral filler perlite. At the bottom of it, we make a cutout for a “lounger”, the width is 120, and the height of the cutout will be 160 mm, i.e. We weld a strip from below using a cut piece 40 mm long.
This insulates the bottom at the joint with perlite. We hide it in the casing and weld a round lid to its bottom.
The required volume of perlite
For the upcoming purchase, you should find out experimentally; to do this, you should fill this space with water. The desired volume is obtained. Perlite is sold in gardening stores and is measured in liters. A channel is welded to the hopper; draft will be provided through it and the loading hopper will be mounted on the base. We organize an air supply inside the “working room”. To do this, we cut into it through the casing and weld a workpiece in the form of a ring to the slot. We use a piece of profile pipe to make a branch for the air duct. There is a door on it for adjustment.
Doors are manufactured and attached to the firebox with an ash pit and to the loading chamber with a draft chamber. The doors on the loading room must be used regularly, but on the firebox - only when igniting or when choosing ash, so it is better to construct them structurally as shown below, it will be more practical.
The perlite is filled in and the hole on top is sealed with a ring-shaped plug. In this case, 5 and a half liters of insulation were used.
Measurements are taken and a hole is cut in order to cover the lower section of the insulation. Since an air suction was attached to the side of the stove, the cutout is not of the correct rectangular shape.
We also produce two balloon rings.
The rings are put on at the junction between, one on the outside, the other on the inside.
Between them, a packing is placed, which is a non-flammable sealing cord, 150 mm long and 10 mm thick. These manipulations will allow you to securely fasten the upper section of the cap, placing it in the grooves of the resulting so-called “saddle”, while it remains removable in order to ensure the possibility of cleaning from waste in the future.
Rocket stove video
To make installation of the lower part easier, the oven can be turned upside down. We center it by welding spacers between the cap and the casing. After this, we weld the insert above the “lounger” into the place of the cutout. We weld rings, the width of which is 30 mm with an outlet at the top of 20 mm, one inside the lower cap, the other on the outside.
We calculate the distance between the top of the “working” pipe and the upper surface of the cap. The cross-sectional area must be less than the lateral area of the imaginary cylinder. In this case, its diameter is 120 mm. The cross-sectional area is 11304 mm². The experimentally calculated figure for the required distance is 50 mm.
Summary: the top will heat up, and the heat will spread over the entire surface area - this will be a stove with excellent efficiency, since the heat will remain in the device and will not fly out into the chimney.
The cap is fastened as follows: corners with 10mm holes are welded along the contour from the bottom and top and screwed together with bolts 8x8 cm long in four places.
The last stage is the chimney outlet at the bottom. To do this, a hole is cut for it.
The stationary rocket furnace in this article was discussed using the example of video material, which can be viewed by following the links below.
Despite such a loud name, a rocket stove, of course, has nothing in common with rocket and space technology. And it doesn’t run on jet fuel at all. The stove received this name for the stream of flame escaping from the top pipe of the camping structures and the sound reminiscent of the roar of an engine.
Let us immediately clarify that the stove will produce a strong sound only if the operating rules are violated - the roar of the engine occurs when excess air enters the firebox. Normally, the rocket stove will make a quiet rustling sound. It runs on wood and other fuels and is highly efficient.
The rocket stove came to us from the USA and is still little known even to professional stove makers, although it definitely deserves attention.
Operating principle of a rocket stove:
- Direct combustion. Fuel gases flow freely through the furnace channels without being stimulated by the draft created by the chimney.
- Flue gases, which are always released when burning wood, are burned. This is called pyrolysis.
The simplest jet furnace will consist of two pipes, one of which goes horizontally and the other goes up. You can use one curved pipe if you have such an opportunity, otherwise welding work is required.
The fuel in the rocket stove is placed directly into the pipe. In this case, the hot gases will tend to escape upward along the vertical section. At the end of the pipe you can place a container that will be used for cooking or boiling water. There must be a gap between the container and the pipe so that combustion products can freely come out.
What else you need to know about the jet stove:
- It is both cooking and heating.
- It is quite possible to equip the “Rocket” with a stove bench, approximately like in a Russian stove, but such a design will be much less cumbersome.
- The operating time on one fuel fill in a rocket stove is approximately six hours, and it retains heat for up to 12 hours if the metal structure is finished with adobe plaster.
- Initially, the rocket stove was intended for use outdoors, in field conditions. Portable metal structures still occupy first place in popularity, but stationary stoves have also appeared that work on the same principle, made of brick or clay.
Pros of the rocket stove:
- The design itself is simple, you can do it yourself, the materials are available.
- Ability to use different kinds fuel. In such a stove, even low-quality fuel, damp thin branches, and so on will burn.
- Energy independence.
- High operating efficiency, lower fuel consumption.
Cons of a jet stove:
- It will have to be controlled manually. It is necessary to constantly monitor and regulate the combustion process.
- Some elements of the rocket stove can become very hot, especially the simplest ones. metal structures. That is, there is a great danger of burns when touched; you should be especially careful and keep children away from the rocket stove.
- It will not work to use a stove of this design in a bathhouse, since it is simply not able to quickly heat the room to the required temperature.
Now you can find the simplest diagrams of how to build a rocket stove out of 20 bricks with your own hands without mortar in literally three minutes anywhere. The first row will be solid, with a horizontal protrusion, the second will have a hole above the protrusion for loading fuel, the remaining three rows will be a pipe. It will be warm; you can simply place a cauldron or pan on top.
However, in more complex and efficient options, flue gases are passed under the stove bench, for example, through special channels. The second option is to install a water circuit on a simple rocket stove.
These are examples of biodesign of stoves that work on the “rocket” principle, but are much more complex and modernized, with stove beds. The construction of such clay ovens is carried out by German company Lehm und Feuer.
Let us state that a rocket stove has many advantages, including ease of installation, the ability to be used in the field or in the summer in the yard for cooking various dishes over a live fire. You just need to understand the operating principles and design features.