Alcohol-based fuel self-flowing heating stove

Abstract

The application discloses an alcohol-based fuel self-flow heating stove and belongs to the field of heating equipment. The alcohol-based fuel self-flow heating stove comprises a base, a stove cylinder and a stove surface, the stove cylinder is fixed on the base, the stove surface is installed on the top end of the stove cylinder, further comprises: a fuel tank, the base is provided with a cavity, an oil injection port is formed on the top of the base and corresponds to the outer circumferential side of the stove cylinder, the fuel tank is installed in the cavity of the base, an oil inlet port is formed on the top of the fuel tank and is communicated with the oil injection port, and an oil outlet port is formed on the bottom of the fuel tank; a combustion chamber, the combustion chamber comprises a combustion cylinder, a stove core and a ventilation assembly. The alcohol-based fuel of the new energy is adopted, energy saving and environmental protection are achieved, and through the multilayer ventilation structure of the combustion chamber, fuel overflow can be prevented, ventilation and wind gathering can be simultaneously achieved, the direction of airflow flowing into the combustion chamber can be effectively controlled, fuel can be fully combusted, and the combustion effect is enhanced.

Description

Technical Field

[0001] This invention relates to the field of heating equipment technology, and more specifically to an alcohol-based fuel self-flowing heating stove. Background Technology

[0002] Heating stoves are common heating devices, mainly including recirculating air stoves, biomass pellet stoves, and electric stoves. Among them, stoves that use solid fuels such as coal and biomass pellets are widely used because of their high heat output and wide heat coverage. However, the combustion of these fuels easily produces smoke and has a large amount of carbon emissions, which does not meet environmental protection requirements.

[0003] Among new energy fuels, alcohol-based fuels are a clean energy source. Their combustion products are mainly water and carbon dioxide, and they are characterized by being smokeless, odorless, and pollution-free, which can fundamentally improve environmental quality. Therefore, alcohol-based fuels have become the preferred fuel for heating equipment. However, existing alcohol-based fuel heating equipment generally uses oil pumps for oil supply, which is costly and prone to failure. Furthermore, it suffers from incomplete fuel combustion, low thermal efficiency, and significant waste of heat energy, affecting heating performance.

[0004] Therefore, how to design a heating stove with a simple structure and good heating effect is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention aims to provide an alcohol-based fuel self-flowing heating stove to solve the problems of complex structure, high cost and incomplete fuel combustion in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An alcohol-based fuel self-flowing heating stove includes a base, a furnace cylinder, and a furnace surface. The furnace cylinder is fixed to the base, and the furnace surface is installed at the top of the furnace cylinder. The stove also includes:

[0008] The fuel tank has a cavity inside the base, and an oil filling port is opened on the top of the base corresponding to the outer periphery of the furnace cylinder. The fuel tank is installed in the cavity of the base, and an oil inlet is opened on the top of the fuel tank that communicates with the oil filling port, and an oil outlet is opened at the bottom.

[0009] The combustion chamber includes a combustion cylinder, a furnace core, and a ventilation assembly. A first mounting hole communicating with its inner cavity is provided at the center of the top of the base. The combustion cylinder is installed in the first mounting hole, with its upper end corresponding to the inner cavity of the furnace cylinder and its lower end extending into the inner cavity of the base. The bottom of the combustion cylinder is closed, and a furnace core mounting hole is provided at the center of its bottom. The furnace core is coaxially arranged with the combustion cylinder, and its lower end is fixed in the furnace core mounting hole, forming an annular combustion chamber between the furnace core and the combustion cylinder. The ventilation assembly is fixed to the outer periphery of the combustion cylinder, and its air outlet is connected to the combustion chamber. A fuel inlet communicating with the combustion chamber is provided at the lower end of the combustion cylinder corresponding to the oil outlet below it. The oil outlet of the fuel tank is connected to the fuel inlet through an oil pipe.

[0010] The beneficial effects that this invention can achieve are: the fuel tank is installed inside the base, which facilitates fuel storage and supply; the fuel flows into the combustion chamber through the oil pipe under the action of gravity and burns; the ventilation component can not only prevent fuel overflow, but also ventilate and concentrate the airflow in the base into the combustion chamber, thereby enhancing the combustion effect and ensuring complete combustion of the fuel.

[0011] Preferably, the fuel tank is an annular fuel tank with an annular storage chamber inside. The bottom end of the combustion cylinder extends through the inner ring of the annular fuel tank to the bottom of the annular fuel tank, and the fuel inlet is lower than the fuel outlet of the annular fuel tank. This maximizes the fuel tank's storage capacity while ensuring a small base volume.

[0012] Preferably, a mounting flange is fixed to the outer wall of the upper end of the combustion chamber, and the mounting flange is fixed to the top of the base by multiple bolts. The combustion chamber is easy to disassemble and assemble, facilitating maintenance and cleaning.

[0013] Preferably, the base has multiple first ventilation holes on its side wall. These holes are used to connect to outside air so as to introduce oxygen into the combustion chamber.

[0014] Preferably, the upper end of the combustion cylinder has multiple second ventilation holes to allow air to enter the combustion chamber.

[0015] Preferably, the furnace core has a top-closed cylindrical structure with multiple third ventilation holes on its upper side wall. Air is introduced into the combustion chamber to ensure complete combustion of the fuel and enhance the combustion effect.

[0016] Preferably, the ventilation assembly includes multiple ventilation bends, and multiple air inlets are circumferentially spaced at the lower end of the combustion chamber sidewall. Each ventilation bend corresponds to one of the multiple air inlets, and the air outlet at the bottom of each ventilation bend is fixed at the air inlet. The air inlet at the top extends towards the inner top wall of the base, and there is a gap between the top air inlet and the inner top wall of the base. The fuel inlet is located on the sidewall of the combustion chamber below the corresponding air inlet. This design prevents fuel overflow and allows air to be introduced into the fuel within the combustion chamber through the ventilation bends, enhancing combustion efficiency.

[0017] Preferably, the ventilation assembly includes an outer casing with an open top and a closed bottom. A combustion chamber mounting hole is located at the center of the bottom of the outer casing. The combustion chamber is fitted inside the inner cavity of the outer casing, and its bottom end is fixedly connected to the inner wall of the combustion chamber mounting hole. An annular ventilation cavity is formed between the combustion chamber and the outer casing. An air supply hole communicating with the annular ventilation cavity is located at the upper end of the outer casing. The fuel inlet is located on the outer periphery of the bottom of the combustion chamber corresponding to the furnace core mounting hole. This design prevents fuel overflow and allows air to be supplied to the fuel within the combustion cavity through the air supply hole, enhancing combustion efficiency.

[0018] Preferably, a flame-drawing tube is also provided, which is coaxially arranged with the combustion tube and its bottom end is spaced and fitted onto the outer periphery of the upper end of the combustion tube. The hot airflow flows upward along the flame-drawing tube, causing the flame to burn upward along the inner cavity of the flame-drawing tube, thereby enhancing the combustion effect.

[0019] Preferably, the oven also includes a baking tray. Multiple connecting plates are circumferentially fixed to the inner wall of the oven cylinder corresponding to the top of the fire-starting tube. The baking tray is fixed to the multiple connecting plates by bolts, and a ventilation hole communicating with the inner cavity of the fire-starting tube is opened in the middle of the baking tray corresponding to the top of the fire-starting tube. The baking tray can be used for baking food, etc.

[0020] As can be seen from the above technical solution, compared with the prior art, the present invention discloses an alcohol-based fuel self-flowing heating stove, which has the following beneficial effects:

[0021] 1. It uses alcohol-based fuels, a new energy source, which is energy-saving and environmentally friendly.

[0022] 2. The fuel tank is installed inside the base, which facilitates fuel storage and supply. Moreover, the fuel can flow into the combustion chamber through the oil pipe under the action of gravity for combustion. The structure is simple, the cost is low, and it is easy to maintain.

[0023] 3. The combustion chamber adopts a multi-layer ventilation structure, which can prevent fuel overflow in the combustion chamber, and at the same time play the role of ventilation and air gathering, effectively controlling the direction of airflow into the combustion chamber, thereby enabling the fuel to burn completely and enhancing the combustion effect. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a three-dimensional structural diagram of an alcohol-based fuel self-flowing heating stove provided by the present invention.

[0026] Figure 2 This is a top view schematic diagram of an alcohol-based fuel self-flowing heating stove provided by the present invention.

[0027] Figure 3 This is a schematic cross-sectional view of an alcohol-based fuel self-flowing heating stove provided in Example 1.

[0028] Figure 4 for Figure 3 Enlarged structural diagram of section A.

[0029] Figure 5 This is a schematic diagram of the three-dimensional structure of the combustion chamber provided in Example 1.

[0030] Figure 6 This is a three-dimensional structural diagram of an alcohol-based fuel self-flowing heating stove provided in Example 1.

[0031] Figure 7 This is a schematic cross-sectional view of an alcohol-based fuel self-flowing heating stove provided in Example 2.

[0032] Figure 8 for Figure 7 Enlarged structural diagram of section B.

[0033] Figure 9 This is a schematic diagram of the three-dimensional structure of the combustion chamber provided in Example 2.

[0034] Figure 10 This is a three-dimensional structural diagram of an alcohol-based fuel self-flowing heating stove provided in Example 2.

[0035] In the diagram: 1. Base; 11. Oil inlet; 12. First ventilation hole; 13. Adjustment hole.

[0036] 2. Furnace cylinder; 21. Connecting plate; 22. Heat dissipation holes; 23. Ear plate;

[0037] 3. Furnace surface; 31. First vent hole; 32. Snap ring; 33. First screw.

[0038] 4. Fuel tank; 41. Oil pipe; 42. Check valve;

[0039] 5. Combustion chamber; 51. Combustion cylinder; 511. Combustion chamber; 512. Fuel inlet; 513. Second ventilation hole; 52. Furnace core; 521. Third ventilation hole; 53. Mounting flange; 54. Ventilation bend; 55. Outer cover; 551. Make-up air hole; 552. Annular ventilation chamber.

[0040] 6. Pull out the fire tube;

[0041] 7. Baking tray;

[0042] 8. Fuel tank fixing assembly; 81. Fixing plate; 82. Second screw; 83. Second locking nut; 84. Third locking nut. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] Example 1:

[0047] Please see Figures 1-6 This invention discloses an alcohol-based fuel self-flowing heating stove, comprising a base 1, a furnace cylinder 2, and a furnace surface 3. The furnace cylinder 2 is fixed to the base 1, and the furnace surface 3 is installed on the top of the furnace cylinder 2. The stove also includes:

[0048] The fuel tank 4 has a cavity inside the base 1, and the top of the base 1 is provided with an oil inlet 11 corresponding to the outer periphery of the furnace cylinder 2. The fuel tank 4 is installed in the cavity of the base 1, and the top of the fuel tank 4 is provided with an oil inlet that communicates with the oil inlet 11, and the bottom is provided with an oil outlet.

[0049] Combustion chamber 5 includes a combustion cylinder 51, a furnace core 52, and a ventilation assembly. A first mounting hole communicating with its inner cavity is opened at the center of the top of the base 1. The combustion cylinder 51 is installed in the first mounting hole, with its upper end corresponding to the inner cavity of the furnace cylinder 2 and its lower end extending into the inner cavity of the base 1. The bottom of the combustion cylinder 51 is closed and a furnace core mounting hole is opened at the center of its bottom. The furnace core 52 is coaxially arranged with the combustion cylinder 51 and its lower end is fixed in the furnace core mounting hole. An annular combustion chamber 511 is formed between the furnace core 52 and the combustion cylinder 51. The ventilation assembly is fixed on the outer periphery of the combustion cylinder 51 and its air outlet is connected to the combustion chamber 511. A fuel inlet 512 communicating with the combustion chamber 511 is opened below the oil outlet at the lower end of the combustion cylinder 51. The oil outlet of the fuel tank 4 is connected to the fuel inlet 512 through an oil pipe 41.

[0050] The fuel tank 4 of the present invention is installed inside the base 1, which facilitates fuel storage and supply. Under the action of gravity, the fuel flows into the combustion chamber 511 through the oil pipe 41 for combustion. The ventilation component plays the role of ventilation and air gathering, preventing large airflows from being dispersed into the combustion chamber 511, thereby enhancing the combustion effect and ensuring complete combustion of the fuel.

[0051] In this embodiment, a first fire hole 31 is provided in the center of the furnace surface 3, and a retaining ring 32 is fixed on the lower end of the furnace surface 3 corresponding to the outer periphery of the first fire hole 31. The top end of the furnace cylinder 2 is locked in the retaining ring 32.

[0052] In this embodiment, a plurality of first screws 33 are provided on the lower plate of the furnace surface 3, and a plurality of ear plates 23 are evenly distributed around the upper outer wall of the furnace cylinder 2. The plurality of first screws 33 correspond one-to-one with the plurality of ear plates 23, and the bottom end of the first screw 33 passes through the ear plate 23 and is connected to a first locking nut.

[0053] In this embodiment, multiple heat dissipation holes 22 are provided on the side wall of the furnace cylinder 2, which can allow air to pass into the interior and at the same time play a role in heat dissipation, thereby enhancing the heating effect.

[0054] In this embodiment, the fuel tank 4 is an annular fuel tank with an annular storage chamber inside. The bottom end of the combustion cylinder 51 extends through the inner ring side of the annular fuel tank to the bottom of the annular fuel tank. While ensuring the maximum fuel storage capacity of the fuel tank 4, the internal structure of the base 1 is made compact, thereby reducing the volume of the base 1.

[0055] In this embodiment, the annular fuel tank has a square ring structure, formed by welding four square tubes together. In some other embodiments, the annular fuel tank may also be a rectangular, circular, or other ring-shaped structure. Methanol can be used as the fuel, which is low-cost and energy-efficient.

[0056] In this embodiment, see Figure 4 It also includes multiple sets of fuel tank fixing components 8 for fixing the annular fuel tank. Each set of fuel tank fixing components 8 includes a fixing plate 81, multiple second screws 82, multiple second locking nuts 83 and a third locking nut 84. The fixing plate 81 abuts against the bottom of the annular fuel tank. The second screws 82 correspond to the inner ring side of the annular fuel tank. Their top ends pass through the top wall of the base 1 and are threaded to the second locking nuts 83. Their bottom ends pass through the fixing plate 81 and are threaded to the third locking nuts 84.

[0057] In this embodiment, a stop valve 42 is installed on the oil pipe 41 near the oil outlet of the annular fuel tank. An adjustment hole 13 is provided on the side wall of the base 1 corresponding to the stop valve 42. The stop valve 42 can be manually opened and closed, and the oil supply can be adjusted by the valve. After the valve is opened, the oil pipe 41 automatically flows into the combustion chamber 511 under the action of gravity, and can be ignited by a spark for heating.

[0058] In this embodiment, a mounting flange 53 is fixed to the outer wall of the upper end of the combustion chamber 51, and the mounting flange 53 is fixed to the top of the base 1 by multiple bolts. The combustion chamber 5 is easy to disassemble and assemble, and convenient for maintenance and cleaning.

[0059] In this embodiment, a plurality of first ventilation holes 12 are provided on the side wall of the base 1. These holes are used to connect to outside air so as to introduce oxygen into the combustion chamber 5.

[0060] In this embodiment, the upper end of the combustion cylinder 51 is provided with multiple second ventilation holes 513 to allow air to be introduced into the combustion chamber 511.

[0061] In this embodiment, the furnace core 52 has a top-closed cylindrical structure, with multiple third ventilation holes 521 on its upper side wall. Air is introduced into the combustion chamber 511 to ensure complete combustion of fuel and enhance combustion efficiency.

[0062] In this embodiment, the ventilation assembly includes multiple ventilation bends 54. Multiple air inlets are circumferentially spaced at the lower end of the side wall of the combustion chamber 51. Each ventilation bend 54 corresponds to one of the multiple air inlets, and its bottom outlet end is fixed at the air inlet. The top air inlet end extends towards the inner top wall of the base 1, and there is a gap between the top air inlet end and the inner top wall of the base 1. A fuel inlet 512 is located on the side wall below the corresponding air inlet of the combustion chamber 51. This prevents fuel overflow and allows air to be introduced into the fuel within the combustion chamber 511 through the ventilation bends 54, enhancing the combustion effect.

[0063] In this embodiment, a flame-drawing tube 6 is also provided. The flame-drawing tube 6 is coaxially arranged with the combustion tube 51, and its bottom end is sleeved on the outer periphery of the upper end of the combustion tube 51, forming a gap between the flame-drawing tube 6 and the combustion tube 51 to allow air to flow through the second ventilation hole 513. The flame-drawing tube 6 is a conical tube with a smaller inner diameter at the top and a larger inner diameter at the bottom, used to concentrate the flame, enhance the flame-drawing effect, and promote complete combustion of fuel.

[0064] In this embodiment, as Figure 2 It also includes a baking tray 7. Multiple connecting plates 21 are fixed at intervals on the inner wall of the oven cylinder 2 corresponding to the top of the fire-operated tube 6. The baking tray 7 is mounted on the connecting plates 21 by multiple bolts, and a fire-venting hole is provided at the location of the baking tray 7 corresponding to the fire-operated tube 6. The baking tray 7 can be used to roast foods such as sweet potatoes, with high baking efficiency.

[0065] Example 2:

[0066] See Figures 1-2 and Figures 6-9 The other structures in this embodiment are the same as in Embodiment 1. In this embodiment, the ventilation assembly includes an outer casing 55, which is open at the top and closed at the bottom. A combustion chamber mounting hole is provided at the center of the bottom of the outer casing 55. The combustion chamber 51 is fitted into the inner cavity of the outer casing 55, and its bottom end is fixedly connected to the inner wall of the combustion chamber mounting hole. An annular ventilation cavity 552 is formed between the combustion chamber 51 and the outer casing 55. An air supply hole 551 communicating with the annular ventilation cavity 552 is provided at the upper end of the outer casing 55. A fuel inlet 512 is located on the outer periphery of the bottom of the combustion chamber 51 corresponding to the furnace core mounting hole. This prevents fuel overflow and allows air to be supplied to the fuel in the combustion cavity 511 through the air supply hole 551, enhancing the combustion effect.

[0067] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0068] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An alcohol-based fuel self-flowing heating stove, comprising a base (1), a furnace cylinder (2), and a furnace surface (3), wherein the furnace cylinder (2) is fixed on the base (1), and the furnace surface (3) is installed on the top of the furnace cylinder (2), characterized in that, Also includes: The fuel tank (4) has a cavity inside the base (1), and the top of the base (1) is provided with an oil inlet (11) corresponding to the outer periphery of the furnace cylinder (2). The fuel tank (4) is installed in the cavity of the base (1), and the top of the fuel tank (4) is provided with an oil inlet that communicates with the oil inlet (11), and the bottom is provided with an oil outlet. Combustion chamber (5), comprising combustion cylinder (51), furnace core (52) and ventilation assembly, wherein the base (1) has a first mounting hole at the center of its top, communicating with its inner cavity, the combustion cylinder (51) is installed in the first mounting hole, its upper end corresponding to the inner cavity of the furnace cylinder (2), and its lower end extending into the inner cavity of the base (1); the bottom of the combustion cylinder (51) is closed and a furnace core mounting hole is opened at the center of its bottom, the furnace core (52) is coaxially arranged with the combustion cylinder (51) and Its bottom end is fixed in the furnace core mounting hole, and the furnace core (52) and the combustion cylinder (51) form an annular combustion chamber (511); the ventilation assembly is fixed on the outer periphery of the combustion cylinder (51) and its air outlet is connected to the combustion chamber (511); the lower end of the combustion cylinder (51) is provided with a fuel inlet (512) connected to the combustion chamber (511) below the oil outlet, and the oil outlet of the fuel tank (4) is connected to the fuel inlet (512) through an oil pipe (41). The base (1) has multiple first ventilation holes (12) on its side wall. The upper end of the combustion cylinder (51) is provided with a plurality of second ventilation holes (513); The furnace core (52) has a top-closed cylindrical structure, and its upper side wall has multiple third ventilation holes (521). The ventilation assembly includes multiple ventilation bends (54), and multiple air inlets are circumferentially spaced at the lower end of the side wall of the combustion cylinder (51). Each ventilation bend (54) corresponds to one of the multiple air inlets, and the air outlet at the bottom of each ventilation bend (54) is fixed at the air inlet. The air inlet at the top extends towards the inner top wall of the base (1), and there is a gap between the air inlet at the top and the inner top wall of the base (1). The fuel inlet (512) is located on the side wall of the combustion cylinder (51) below the corresponding air inlet. The ventilation assembly includes an outer cover (55), which is open at the top and closed at the bottom. A combustion chamber mounting hole is provided at the center of the bottom of the outer cover (55). The combustion chamber (51) is fitted inside the outer cover (55) and its bottom end is fixedly connected to the inner wall of the combustion chamber mounting hole. An annular ventilation cavity (552) is formed between the combustion chamber (51) and the outer cover (55). An air supply hole (551) communicating with the annular ventilation cavity (552) is provided at the upper end of the outer cover (55). The fuel inlet (512) is opened on the outer periphery of the bottom of the combustion chamber (51) corresponding to the furnace core mounting hole.

2. The alcohol-based fuel self-flowing heating stove according to claim 1, characterized in that, The fuel tank (4) is an annular fuel tank with an annular storage chamber inside. The bottom end of the combustion cylinder (51) extends through the inner ring side of the annular fuel tank to the bottom of the annular fuel tank, and the fuel inlet (512) is lower than the fuel outlet of the annular fuel tank.

3. The alcohol-based fuel self-flowing heating stove according to claim 2, characterized in that, The upper outer wall of the combustion cylinder (51) is fixed with a mounting flange (53), which is fixed to the top of the base (1) by multiple bolts.

4. A self-flowing alcohol-based fuel heating stove according to any one of claims 1-3, characterized in that, It is also provided with a fire-drawing tube (6), which is coaxially arranged with the combustion tube (51) and its bottom end is spaced and sleeved on the outer periphery of the upper end of the combustion tube (51).

5. The alcohol-based fuel self-flowing heating stove according to claim 4, characterized in that, It also includes a baking tray (7), and multiple connecting plates (21) are fixed circumferentially at intervals on the inner wall of the furnace cylinder (2) corresponding to the top of the fire tube (6). The baking tray (7) is fixed to the multiple connecting plates (21) by bolts, and a fire hole is opened in the middle of the baking tray (7) corresponding to the top of the fire tube (6) to communicate with the inner cavity of the fire tube (6).

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