- “Bubafonya” or piston PDG
- How to assemble
- A problem that doesn’t exist
- Making the most of
- “Rocket” or jet furnace (RP)
- How it works and benefits
- Stage one. Pure stream
- Stage two. “Rocket potbelly stove”
- Stage three. Vertical heat exchanger system
- Stage four. Install the injector
- Stage five. Turbocharging
- Diy pyrolysis rocket oven from cans
What are the designs of long-burning furnaces? In this article, you will learn how top-loading long-burning furnaces are fundamentally different and how to improve their efficiency. We will tell you about the secrets of their manufacture and provide step-by-step instructions.
Continuing the topic of manufacturing and improving long-burning furnaces (LPH), we will describe in detail devices with top loading. The advantages of this option:
- Compact combustion chamber.
- Using gravity at work.
- More efficient sale of fuel (firewood).
- Low discharge temperature – no need to insulate the chimney.
- Relative purity (smokelessness) of the emission – less problems with neighbors.
The fundamental difference between such stoves and stoves and their derivatives is the gradual combustion of fuel and, as a result, a smooth and even distribution of heat (in the stoves, the entire load flares up at once).
The two most popular types of PDG are Bubafonya and Raketa (rocket oven). In the first case, energy is realized from the combustion of wood under pressure with a deficiency of oxygen, in the second – a reactive process that occurs when the temperature drops.
“Bubafonya” or piston PDG
This stove received its original name from the nickname of the author, who for the first time posted the scheme in the public domain. Whether he is the inventor of this variety is unknown. Most likely, in one form or another, it has existed for a long time, since its action is based only on the laws of physics and nature..
The peculiarity of this version of the PDG is the constant pressure of the piston, the heel of which balances and maintains a constant uniform temperature, not allowing individual sections to cool or overheat..
“Bubafonya” is something like a cylinder of a piston internal combustion engine in an extremely primitive form:
- Combustion chamber (CC). An open cylindrical container (barrel, cylinder, pipe) without hatches and with a chimney at the upper border. The size of the COP can vary from 20 to 240 liters.
- Piston. Steel tube with a cross section of 75 mm with a round heel at one end. The heel has a diameter 40–50 mm less than the KS, and a hole for the pipe diameter. In the outer part, the heel has ribs for admitting air to the combustion area. Functionally, this part plays the role of an air duct and a press.
- Cap. Plain steel cover with hole for duct pipe.
The simplicity and reliability of the design, as well as the availability of material, made this stove the most popular among villagers and garage owners. “Bubafonya” holds the record for the duration of burning – a combustion chamber from a 200 l barrel with a full dense vertical load works for 20-24 hours.
How to assemble
1. Cut off the top cover of the barrel (it should not be rotten). It can then be used under the oven cover. If it is a gas cylinder, cut it off along the border of the head-to-wall adhesion. Cut a chimney hole 20-30 mm from the top edge and weld a channel from a 100-120 mm pipe.
2. Air duct (BB). For compressor stations of any size, the sufficient inner diameter of the BB pipe is 75 mm. The length of the explosive is equal to the height of the CC plus 200-300 mm.
3. Heel. Cut a sheet of 4–6 mm in the form of a circle with a diameter smaller than the combustion chamber by 30–40 mm.
4. Cut out a hole in the center of the heel equal to the inner diameter of the BB plus 2-3 mm. Along the edge, you can weld on a side from the strip for the stability of the piston with a loaded firebox.
5. We weld on the working surface of the heel corners 30×30 or 40×40 in the form of rays from the center.
6. Weld BB to the heel at an angle of exactly 90? on the back of the ribs.
7. At the free end of the explosive, weld on the M6 nut from the inside. We cut out the damper along the section of the BB and install it on the screw. A magnet with a suitable diameter can be used. This damper regulates the air supply to the combustion center.
8. On the lid, weld on a strip of 20-30 mm in a circle like a side.
Any solid combustible material can serve as fuel for a long-burning piston furnace of the Bubafonya type, but, as a rule, it is firewood. A small amount of rubber or plastic will not give a “black exhaust”, because it will completely burn out in the COP. The fuel is loaded with the piston removed, but in the course of work, you can reload the stove with small firewood through the explosive pipe. Safe ignition can also be done through explosives.
A problem that doesn’t exist
A meticulous craftsman will try to fit the explosive under the lid, and the lid under the COP as tightly as possible and even provide for seals. Empirically, it has been found that such “improvements” turn into the inability of the furnace to work productively. The secret lies in the secondary air, which is pumped through the gaps in the top and provides traction. In this case, the slots act as injectors, which we talked about in the previous article..
Making the most of
Convector.To remove heat from the combustion chamber (furnace) there is a simple and effective solution based on air convection.
Convection is a type of heat transfer in which heat energy is transferred by streams or jets.
For the device of a primitive convector, we need a profiled galvanized sheet with a medium wave, which you just need to wrap around the combustion chamber. The profile waves will serve as channels through which air will flow. Heated from the oven, it will rush upward, and its place will be taken by cold air coming from the bottom of the channel. If there is no profiled sheet, you can fix the trimming of the CD or UD profile around the firebox and chimney.
Shroud.Another type of convector can be a primitive coaxial system..
Coaxial – from Latin with– joint and axis– axis, that is, having a common axis.
To do this, we weld brackets 40-50 mm long onto the combustion chamber, retreating 50 mm from the top and bottom. We fix a sheet of metal on them. The thickness is not decisive here, since air acts as a coolant, and the casing itself will not heat up. Thin zinc plating is suitable, which can be made removable.
Long straight chimney.If it is possible to easily increase the length of the chimney inside the room, this will allow to remove the remaining temperature of the exhaust gases.
Fan,directed to the PDG, effectively mixes the air, which will give a quick and uniform heating of the room.
The described version of the furnace has one, but significant drawback, which can be considered as a tribute to the simplicity of the design. Ash pan cleaning is a dusty job. The bottom part of the compressor station serves as the ash pan itself and the removal of ash through the side is inconvenient, but necessary.
Council. We recommend keeping 80-100 mm of ash on the bottom at all times – this will prevent the bottom from burning out prematurely.
One more nuance can only be called “production cost”. When using a barrel, the walls of the furnace burn out relatively quickly. With intensive operation (at high temperatures), the combustion chamber will have to be replaced after 3-4 seasons. But here, too, simplicity ensures success – it is enough to find the same barrel. In this case, the gas cylinder will serve for decades..
“Rocket” or jet furnace (RP)
Another type of energy efficient stove is known as the Rocket or Rocket Stove. She received a sonorous name because of the reactive process based on heat exchange with a significant temperature difference (and the resulting thrust), which is also implemented in rocket jet engines. This natural phenomenon is inscribed in the basic laws of physics due to its trouble-free operation..
RP always has a “knee” of no more than 90 ° in one form or another. That is, the chimney is located at a right or acute angle to the bottom of the furnace. An air duct (BB) is required, which is often located adjacent (through the wall) to the firebox.
How it works and benefits
The main difference between the RP and the furnaces described earlier is that the temperature is not concentrated in the furnace, but in the air stream, which is in constant dynamics. Continuous draft arising at the place of heating (knee) brings oxygen with the flow of combustion air into the furnace through the explosive, in the furnace the air receives heat energy from the combustion of fuel and gives it away at the place of temperature drop (knee and “neighborhood”), due to which supported.
In constant RP mode, air supply adjustment is not required – the natural tendency to balance the processes provides the thrust of exactly the same force that is required to realize the temperature in the furnace. The exhaust gases exit also naturally – by the pressure of the heated air (therefore, the RP does not require a high chimney pipe).
We will implement the effect of heat flux reactivity in stages, making the design more and more complex..
Stage one. Pure stream
As we have already found out, the main element and condition for the existence of the flow is the bend of the channel. Welding at an angle of 90 ° two pipes with a diameter of 150 mm, correlated as 1/2, we get a finished “rocket” firebox with a chimney pipe. The short section is horizontal, the long section is vertical. If you build a fire horizontally, the flame will come out along a vertical pipe..
A primitive version of the secondary air supply can be organized by installing a sheet of metal inside the firebox on the brackets – the hearth will be separated from the air duct. In this case, the air passing through it will fall into the corner of the knee, which makes it possible to call it secondary. Such a device can be welded on the legs and put a grid for a frying pan on the upper channel..
Stage two. “Rocket potbelly stove”
We take the structure described above as a basis and add one more element – a horizontal section (channel). The rectangular section of the channels will be easier to use than pipes.
Rocket potbelly stove: 1 – plate; 2 – area of heating and heat transfer; 3 – air flow
In this case, the air duct can be located arbitrarily – the main thing is that air passes through it. These can be “cheeks” parallel to the side walls of the loading hatch, or a plate on the ribs along the bottom wall.
Next, we attach a chimney from a steel pipe to the knee (it is also a residual heat exchanger) and arrange a cover. It is difficult to accurately describe the structure, since most often it is made from scrap materials. It is important to understand and implement the very principle of flow formation.
Stage three. Vertical heat exchanger system
The idea is to construct a steel heat exchanger with thick walls in the path of the hot flow.
The structure is an element from the second stage, increased in size, on which an empty container for dry heat exchange (ideally an empty gas cylinder) will be located instead of a vertical pipe. In this case, the flue duct must be aligned with the horizontal element..
The horizontal element itself (firebox) can be executed in different forms – stove body, pipe or box. It can serve as a pre-heat exchanger (if large enough). For prolonged (up to 4 hours) continuous combustion, you need to increase the fuel compartment. It can be up to 600 mm high and take the logs vertically. Burning will occur at the bottom of them, and under their own weight they will burn out gradually.
Rocket furnace with heat exchanger: 1 – ash pan; 2 – cold air; 3 – fuel compartment; 4 – cover; 5 – firewood; 6 – flame border; 7 – burning area; 8 – heat exchange; 9 – chimney; 10 – balloon
The primary air will be supplied through a door in the area of the firebox, which will serve as an inspection hatch for cleaning. Secondary – through a hole or channel in the elbow, or through a channel in the fuel compartment.
Stage four. Install the injector
Above, the prototypes of the secondary air supply channels were mentioned. At this stage, we will install a separate channel for a complete supply of oxygen to the flame during the afterburning phase..
This will require a steel pipe with a diameter of 12-15 mm, bent in the form of a channel, which is obtained from the elements of the system. On the one hand, it must be plugged and drilled into the wall 6–8 holes 5–6 mm in a section of 100 mm. Then the tube should be installed in such a way that it passes through the entire system, and its “blind” end with holes is in the place where the flame reaches. The open end should exit at the “cold” part of the system and allow air to enter. The heated tube metal will create draft, and fresh air will be supplied for afterburning.
Injector installation options: 1 – ash pan; 2 – cold air; 3 – firebox; 4 – fuel compartment; 5 – injector; 6 – flame border; 7 – heat exchanger
Stage five. Turbocharging
An air pump (possibly an old vacuum cleaner) is connected to the injector. The injector itself must have a higher throughput than with natural supply. When the pump is turned on, the fresh air flow creates an excess additional pressure, and the thrust increases in proportion to the supplied power. This increases the temperature of the heat exchanger..
This method has been known to craftsmen since ancient times – the function of an air pump was performed by blacksmith bellows..
When taking measures for the development of a rocket furnace, remember that the system must be harmonious – all elements must be balanced, otherwise overheating and burning out of the metal.
Diy pyrolysis rocket oven from cans
A camping chip burner will always come in handy, especially since it does not require special materials and skills. Even a teenager can make it. However, for someone who first tackled the issue of heating with “rocket” stoves, this will be a good practice, since the principle of operation is identical:
- We take two cans of different diameters and heights (the difference is 20-25 mm).
- Cut a hole equal to the diameter of the smaller can in the bottom of the larger can.
- Making a network of holes in the bottom of the smaller can.
- We make a belt of holes on the wall of the smaller can at 1/5 of its height from the open edge.
- We make a belt of holes on the wall of the larger jar in 1/7 of its open edge height.
- We insert the smaller jar into the bottom of the larger one so that the bottom of the smaller one fits the open edge of the larger one. Burner ready.
You probably already guessed that, in principle, this is a coaxial gas pipeline system. By adding various devices to such a burner, you can increase the volume of the fuel compartment or boil water.
If you cut a hole for the duct in the wall of a larger capacity and install a fan, you get nothing more than a turbocharged RP.
Using this “pocket” version, you can carry out experiments and comparative measurements – how the material burns by itself and how with the use of secondary air.