Direct-fired bell-type hearth furnace
The bell-type direct combustion hearth furnace addresses manufacturing and transportability issues by using a dome-shaped cap to enhance gas residence time and heat transfer, achieving efficient heating and reduced emissions.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Utility models
- Current Assignee / Owner
- ЖАРИНОВ ВЛАДИМИР ИВАНОВИЧ
- Filing Date
- 2025-12-02
- Publication Date
- 2026-06-30
AI Technical Summary
Existing household heating stoves face challenges such as difficulty in manufacturing, increased weight and size, which hinder transportation and adaptability for heating different rooms, and suboptimal heat utilization during fuel combustion, leading to inefficient heating and harmful emissions.
A bell-type direct combustion hearth furnace with a metal dome-shaped cap in the upper zone of the fuel chamber slows down hot gases, prolonging their residence time and enhancing heat transfer, while a metal cap heats the flue gas duct connected to the chimney, ensuring efficient heat conversion and reduced emissions.
The furnace achieves higher gas temperatures and improved heat transfer, increasing heating efficiency and reducing emissions, with an efficient design that is easy to transport and reinstall for various room heating applications.
Smart Images
Figure 00000002_ABST
Abstract
Description
[0001] The utility model relates to heating equipment, namely to household heating stoves that convert the energy of fuel combustion into heat, and can be used to heat various rooms, as well as individual baths and saunas.
[0002] A sauna stove is known, consisting of three dismountable parts: a firebox, a heater, and a chimney. Flames from the firebox pass through vertical slit-shaped flues around the enclosed heater, heating all six sides of its cuboidal container (Patent for Utility Model No. 68099, prior to March 22, 2006, published November 10, 2007. Bulletin No. 31).
[0003] The disadvantage of this stove is the difficulty in manufacturing and using the heater, which makes the structure heavier and does not allow for its transportation and use for heating different rooms.
[0004] Also known is a sauna stove comprising a metal body, an ash pan, a grate, a heater made in the upper part of the metal body, a smoke pipe communicating with its entrance through an opening made in the bottom of the heater, with the internal cavity of the metal body, and a door for loading fuel, characterized in that it is equipped with fire-reflecting screens made in the form of two metal plates, located with one of their corresponding opposite edges relative to each other with a gap located above the entrance to the smoke pipe, and fixed with their other edges on the corresponding sections of the internal surface of the metal body (Patent for Utility Model No. 145166, prior. from 07 / 21 / 2017, published 09 / 10 / 2014. Bulletin No. 25).
[0005] This renowned furnace expands the arsenal of technical means that ensure the most complete combustion of fuel and, as a result, the minimum possible emission of harmful impurities into the surrounding space.
[0006] The disadvantage of this stove, however, is the suboptimal use of the heat released during combustion of fuel, as well as the difficulty in manufacturing.
[0007] The closest in technical essence is a furnace containing a welded metal body of rectangular shape with a door for loading fuel, with openings for air to enter the body, with a fuel chamber inside and different zones in it, namely a lower zone for burning fuel and an upper zone where hot gases from the burning fuel rise, as well as with a smoke stack connected by an internal channel with the combustion chamber for removing exhaust gases from its upper zone into the smoke stack, and then into the atmosphere (Patent for Utility Model No. 176209, prior. 07 / 21 / 2017, published 01 / 12 / 2018, Bulletin No. 2).
[0008] This stove, which is the closest in technical essence, as its author reports, most effectively spends its thermal energy obtained from burning wood to heat the room in which it is installed, due to the placement in it of a heat-accumulating load in the form of a heater blown by the exhaust hot gases removed from the combustion chamber through an internal channel formed outside it.
[0009] The disadvantage of this stove, which is technically closest to the original, is its increased size and weight, making it difficult to transport to other rooms for heating. This is due to the use of a heavy heat-accumulating load in the form of a heater, located outside the firebox above it and blown by exhaust gases discharged from the firebox through an internal duct formed outside it, connected to the chimney. Furthermore, this stove also has the disadvantage of the fact that the hot gases, unburned in the firebox, discharged from the firebox into the heater are very fast and, without having time to transfer most of their heat to the walls of the stove and decompose, are carried away into the chimney and from there into the atmosphere.
[0010] The purpose of creating a bell-type direct combustion hearth furnace is to form a furnace with a simple and reliable design, which is easy to reinstall and deliver to different rooms for heating, and which effectively converts the energy of the fuel burned in it into heat for heating the room in which it is installed.
[0011] The technical result of the proposed utility model is an increase in the temperature of hot gases both in the upper zone of the furnace's fuel chamber and those exiting its fuel chamber into a heated flue gas duct connected to a chimney, due to the placement in the upper zone of its fuel chamber of a metal dome-shaped cap, which, with its inner surface, slows down the movement of hot gases in it, thereby increasing the time they remain in it and heating them to a higher temperature, and with its outer surface, heats a flue gas duct connected to a chimney outside the firebox, formed between its outer dome-shaped surface and the walls of the furnace body.
[0012] The specified technical result is achieved in that a bell-type direct combustion hearth furnace, containing a welded metal body of rectangular shape with a door for loading fuel, with openings for air to enter the body, with a fuel chamber inside and different zones in it, namely a lower zone for burning fuel and an upper zone where hot gases rise, leaving from the burning fuel, as well as with a smoke pipe connected by an internal gas duct with the fuel chamber for removing exhaust gases from its upper zone into the atmosphere, is equipped with a metal cap located in the upper zone of the fuel chamber, facing its inner surface to the furnace hearth, dome-shaped in cross-section, slowing down the movement of hot gases and formed by its opposing arcuate sidewalls with an opening in the center for placing the end of the smoke pipe in it, wherein one opposing sidewall of the cap,is made with an opening on its side surface for installing the other free end of the smoke pipe in it and with a shelf along the length, welded to the front wall of the furnace, ensuring the exit of exhaust gases from the flue channel into the smoke pipe, and the other side of the cap is freely placed at an acute angle ∠α to the rear wall of the body, forming with it a horizontally extended gap for the discharge through it of hot gas exhausted in the upper zone of the fuel chamber into a flue channel connected to the smoke pipe, formed between the outer dome-shaped surface of the metal cap heated in the firebox and the walls of the furnace body, while the cap is welded with the dome-shaped ends of its sides to the side walls of the furnace body, and an angular pipe is used as a smoke pipe.
[0013] The claimed bell-type direct combustion hearth furnace is shown in the drawings:
[0014] Fig. 1 - bell-type hearth furnace with direct combustion without one sidewall, in a ¾ side view;
[0015] Fig. 2 - front view;
[0016] Fig. 3 - A-A in Fig. 1;
[0017] Fig. 4 - metal cap in a ¾ front view;
[0018] Fig. 5 - side view of Fig. 4;
[0019] Fig. 6 - B-B in Fig. 5.
[0020] A direct combustion bell-type hearth furnace comprises a welded metal body of rectangular shape 1 (Fig. 1 and 2) with a door 2 for loading fuel with openings 3 for air intake, with a fuel chamber inside 4 and different zones in it, namely a lower zone for fuel combustion 5 (Fig. 3) and an upper zone 6, where hot gases leaving from the burning fuel rise, as well as an angular smoke pipe 7, connected by an internal gas duct 8 with the upper zone 6 of the combustion chamber 4 for removing hot gases exhausted in it into the atmosphere.
[0021] In the body 1, namely in the upper zone 6 of the fuel chamber 4, a metal cap 9 of a dome-shaped form in cross-section with an opening 10 (Fig. 4, 5 and 6) at the top for the smoke pipe 7 and with arcuate sidewalls 11 and 12, one of which 11 with an opening 13 for the end of the welded angular smoke pipe 7 and with a shelf 14 along the length (Fig. 2, Fig. 3), welded to the front wall 15 of the furnace, providing an outlet of exhaust gases from the flue channel 8 into the smoke pipe 7, and the other counter arcuate sidewall 12 of the cap 9 is freely placed at an acute angle ∠α to the rear wall 16 of the body 1 of the furnace, forming with it a horizontally extended gap 17 for suction and discharge of gas exhausted in the upper zone 6 fuel chamber 4 into an internal gas duct 8 heated by a metal cap, connected to a smoke pipe 7 and formed between the outer dome-shaped surface of the cap 9 and the walls of the housing: front 15, rear 16 and upper 18.
[0022] In this case, the cap 9 (Fig. 3) is also welded with the dome-shaped ends of its sidewalls 11 and 12 to the side walls 19 and 20 of the furnace body 1 (Fig. 4), heating them during furnace operation and ensuring the tightness of the gas duct 8 (Fig. 3), as well as the strength and reliability of the furnace structure as a whole.
[0023] The direct combustion bell-type hearth furnace operates as follows.
[0024] To light the stove, firewood is placed in the fuel chamber 4 (Fig. 2), specifically in its lower combustion zone 5, without overfilling it to ensure uniform combustion, and then lit. Air entering the fuel chamber 4 through the open door 2 of the housing 1 is directed through the flue duct 8 into the chimney 7, providing draft in the housing 1 and intensive ignition of the fuel. A stable flame is maintained during combustion.
[0025] After the fuel has completely ignited, door 2 of the fuel chamber 4 is closed and combustion of the fuel is maintained by air supplied through openings 3 in door 2 of the housing 1. When the fuel (wood) burns, heat is released and the hot gases rising upward into zone 6 of the fuel chamber 4 abruptly collide with the inner dome-shaped surface of the cap 9, are slowed down by it and are repelled by its arcuate sides, intensively mixing with each other and sharply reducing the speed of their movement, thereby prolonging the time they stay in this upper zone 6 of the fuel chamber 4, heating up to a higher temperature and heating both the cap itself, and the fuel chamber, and the walls of the furnace housing, thereby accelerating the heating of the room in which the furnace is installed. At the same time, the duration of the stay of hot gases in this zone of the fuel chamber with a high temperature also contributes to their most complete combustion, i.e.oxidation of carbon monoxide CO to carbon dioxide CO2, increasing the purity of flue gas emissions through the chimney into the atmosphere.
[0026] Then, with the help of the draft force, the hot gases exhausted in the upper zone 6 of the fuel chamber 4 move through the gap 17 into the internal channel of variable cross-section 8 formed between the hot outer dome-shaped surface of the cap 9 and the walls of the housing 1. Moving along the channel 8 around the hot outer surface of the cap, the hot gases are heated by it and give off their heat to the walls of the furnace, and then rush into the chimney 7.
[0027] Example of the implementation of the claimed utility model
[0028] A sample of a bell-type direct-fired hearth furnace was made by the author of the utility model and installed by him in his brick uninsulated garage, with an area of 7 m x 7 m = 49 m, and a height of 3 m - photos 1 and 2. This sample was made with a niche for cleaning the chimney from accumulated soot in its corner bend, tightly closed by its own flap (in the application for the utility model, this niche for cleaning the chimney is absent).
[0029] Dimensions of the manufactured sample of direct-fired bell-type hearth furnace:
[0030] - Oven area: (width) 30 cm × (depth) 40 cm = 1200 cm 2 = 0.12 m 2 ,
[0031] - oven height - 60 cm
[0032] - oven volume - Voven = 1200 cm × 60 cm = 72000 cm 3 = 0.072 m 3
[0033] - the firebox volume was obtained by calculation.
[0034] CALCULATION OF THE FURNACE FIREPLACE VOLUME:
[0035] The furnace firebox volume corresponds to the difference: Vfirebox = Vstove - Vunder the hood
[0036] Vpod hood - the volume of the furnace under the hood (for ease of calculation, we take this volume as the volume of a triangular prism).
[0037] Vunder the hood = S main × h,
[0038] where Sosn is the area of the triangular base of the prism,
[0039] H - the height of the prism (the distance between its triangular bases corresponds to the length of the cap, fixed with its ends to the side walls of the firebox), H=30 cm.
[0040] The area of the triangular base of a prism can be found using the formula:
[0041] Sbas=1 / 2⋅b⋅h,
[0042] where b is the distance between the ends of the arcs of the cap b=40-3=37 cm,
[0043] h - cap height, h=20 cm.
[0044] Thus, the area of the triangular base:
[0045] Sосн=1 / 2⋅b⋅h=1 / 2⋅37⋅20=370 cm 2 .
[0046]
[0047] Vunder the cap (the volume under the cap, taken as the volume of the triangular prism)
[0048] Vfurnace = Vstove - Vunder the hood = 0.072 m 3 - 0.0111 m3 =0.061 m 3
[0049] - thickness of steel walls of the furnace body - 3 mm,
[0050] - cap metal thickness - 3 mm,
[0051] - the corner chimney is made of two connected steel bends with a thickness of 1 mm and located at an angle of ∠90° to each other: one vertical bend is 3 m long and has a diameter of 80 mm, and the other bend has a rotating sharply curved part with a diameter of 89 mm.
[0052] - a separate vertical branch of the chimney, placed on top of the vertical branch of the corner chimney and protruding beyond the roof of the garage, is made at least 2 meters long so that the total length of the vertical branch of the chimney is at least 5 meters (regulatory requirement).
[0053] To measure the temperature of the flue gases at the outlet of the vertical branch of the chimney, a thermometer with a bimetallic sensor attached to a metal bracket was used, installed outside above the vertical branch of the chimney and not extending beyond the garage.
[0054] The temperature in the garage was measured with a conventional thermometer, located at a height of 1.5 m and at a distance of about 3 meters from the stove.
[0055] The bell-type hearth furnace was manufactured as follows.
[0056] First, a rectangular blank for the hood 9 and all rectangular walls of the stove body 1 were cut out of 3 mm thick steel sheets: front 15; back 16; top 18; side walls 19, 20 and a lower shelf for laying firewood on it.
[0057] Then, on the front wall 15, an opening was cut for installing the door 2 with pre-made holes 3 in it for air intake, and on the top wall 18, an opening 10 was cut for the smoke pipe 7.
[0058] After this, they began forming the hood from its rectangular blank. To do this, they first cut holes in the blank to accommodate the ends of the angular flue pipe 7: one hole 10 in the center of the hood blank, and the other hole 13 on one of the elongated ends of the blank, spaced from its transverse edge by the width of the shelf 14, intended for welding to the front wall of the furnace. Next, this hood was secured to a mandrel and tapped into a dome-shaped form, with hole 10 at its apex and arced sides 11 and 12.
[0059] Then, they began to assemble the blank of the body 1, for this, they welded together all the walls of the body, except for the back 16 and the bottom, intended for laying firewood, and after that, they inserted the manufactured cap 9 into this assembled blank of the body 1 and welded its ends to the opposite sides of the stove 19 and 20, and its shelf 14 to the front wall 15 of the stove.
[0060] Next, a smoke pipe 7 was installed in the assembled body blank, placing its branches in different openings of the cap: a vertical branch, made 3 m long, was passed through the central opening 10 of the cap 9, and the other branch was placed in opening 13.
[0061] After this, the rear wall of the furnace 16 was welded to the assembled body blank, forming, with the freely positioned arc-shaped sidewall 12 of the cap 9, a horizontally extended gap 17 for sucking in and removing gas exhausted in the upper zone 6 of the fuel chamber 4 into the internal gas duct 8, connected to the smoke pipe 7 and formed between the outer dome-shaped surface of the cap 9 and the walls of the body: front 15, rear 16 and upper 18.
[0062] At the end of the stove assembly, a lower shelf was welded to the assembled blank of its body for placing firewood on it.
[0063] Then they manually moved the assembled stove onto a metal sheet in the corner of the brick garage, and then attached a metal bracket to the ceiling of the garage, holding the bimetallic thermometer sensor in the pipe in such a way that the temperature of the flue gases was measured as accurately as possible.
[0064] The direct combustion bell-type hearth furnace is ready for operation.
[0065] The stove in the garage was fired up in February 2026.
[0066] Split birch and pine logs were used as firewood (their moisture content was not measured).
[0067] Initial temperature in the garage: - 5°C (February).
[0068] The first load of firewood in the stove was small, about 4-5 kilograms, it was intended to warm up the stove and create sufficient draft for burning firewood and burned out in about 45 minutes.
[0069] Then we made the first main load of firewood in the amount of 7-8 kilograms, which burned in 50 minutes, while the temperature in the garage rose to +2°C.
[0070] One and a half hours after the stove was lit and the second load of wood had burned through, the temperature in the garage rose to +10°C. The measured flue gas temperature was 180°C.
[0071] To stay comfortably in the garage all day in winter, you usually need to make 2-3 main loads of firewood.
[0072] The stove cooled down within 30 minutes after combustion ceased. The calculated efficiency of the stove indicates the efficient conversion of the energy burned in the stove into heat transferred to the room in which it is installed.
[0073] Approximate calculation of the efficiency of the declared bell-type furnace based on the temperature of the gases leaving the furnace (made using a simplified formula for wood-burning stoves using data tables and calculation formulas set out in the book by M. B. Ravich “Simplified Methodology of Heat Engineering Calculations”, Moscow, Nauka Publishing House, 1966).
[0074] 1. Calculation formula: Efficiency≈100-(Tout / 15+2+3+2)=100-(Tout / 15+7),
[0075] where Tout is the temperature of the flue gases at the outlet of the chimney. Tout=180°C;
[0076] 2. Proportionality coefficient indicating a reduction in flue gas losses by 1% with a temperature decrease of every 15°C: Tout / 15
[0077] 3. Standard flue gas losses:
[0078] 2% - chemical losses;
[0079] 3% - mechanical losses;
[0080] 2% - other losses.
[0081] 4. Efficiency≈100-(Tout / 15+2+3+2)=100-(Tout / 15+7)%=100-(180 / 15+7)=81%.
[0082] Thus, by equipping a direct-fired metal hearth furnace with a metal dome-shaped cap installed in the upper zone of its fuel chamber and slowing down the movement of hot gases in it with its inner dome-shaped surface, which, pushing off from its arcuate sidewalls, collide with each other and intensively mix, sharply reducing the speed of their movement and thereby prolonging the time of their stay in this zone of the fuel chamber, heating up in it to a higher temperature, heating both the cap itself and the walls of the furnace body in contact with them, thereby accelerating the heating of the room in which the furnace is installed, and with its outer surface heating outside the firebox connected to the chimney, formed between its outer dome-shaped surface and the walls of the furnace body, it was possible to create a simple and reliable bell-shaped design of a direct-fired hearth furnace,effectively converting the energy of the fuel burned in it into heat for heating the room in which it is installed,
[0083] Application:
[0084] 1. Photo of a sample of a bell-type direct-fired hearth furnace with a flap covering the niche for cleaning the chimney from ash (the claimed utility model does not contain a niche for cleaning the chimney from ash) - 1 copy.
[0085] 2. Photo of a sample of a bell-type direct-fired hearth furnace with open niches: the upper one is for cleaning the chimney from ash and the lower one is for laying firewood - 1 copy.
Claims
A bell-type direct combustion hearth furnace comprising a welded metal body of rectangular shape with a door for loading fuel, with openings for air to enter the body, with a fuel chamber inside and various zones in it, namely a lower zone for burning fuel and an upper zone where hot gases leaving from the burning fuel rise, as well as with a smoke stack connected by an internal flue channel with the fuel chamber for removing exhaust gases from its upper zone into the atmosphere, characterized in that it is equipped with a metal cap located in the upper zone of the fuel chamber, facing the furnace hearth with its inner surface, dome-shaped in cross-section, slowing the movement of hot gases and formed by its opposing arcuate sidewalls with an opening in the center for placing the end of the smoke stack in it,wherein one counter sidewall of the cap is made with an opening on its side surface for installing the other free end of the smoke pipe in it and with a shelf along the length, welded to the front wall of the furnace, ensuring the exit of exhaust gases from the flue channel into the smoke pipe, and the other sidewall of the cap is freely placed at an acute angle ∠α to the rear wall of the housing, forming with it a horizontally extended gap for the discharge through it of hot gas exhausted in the upper zone of the fuel chamber into a flue channel connected to the smoke pipe, formed between the outer dome-shaped surface of the metal cap heated in the firebox and the walls of the furnace housing, wherein the cap is welded with the dome-shaped ends of its sides to the side walls of the furnace housing, and an angular pipe is used as a smoke pipe.