A hybrid air heater furnace

Abstract

The utility model relates to a boiler technical field, concretely is a kind of mixed wind heating furnace, including furnace body, the inside of furnace body is provided with combustion chamber, and the one end of combustion chamber is installed with burner, and the other end of combustion chamber is provided with opening, and the inside of furnace body is close to the opening at the one end of combustion chamber and is provided with mixing cavity, and the inner wall of furnace body and the outer wall of combustion chamber are provided with annular cold air layer, and one end of cold air layer is communicated with mixing cavity.The mixed wind heating furnace, the opening diameter of the one end of combustion chamber close to mixing cavity is less than internal diameter, and the flow velocity is promoted when high-temperature airflow flows out through small mouth, and local negative pressure is formed in mixing cavity, and power is provided for cold air introduction;Annular cold air layer between furnace body and combustion chamber makes cold air evenly distribute along the outer wall of combustion chamber, forms annular airflow to wrap high-temperature airflow, avoids cold air local concentration;Cold air layer is directly communicated with mixing cavity, and cold and hot air is fully convection, diffusion in independent mixing cavity, and not preliminary contact in open channel.

Description

Technical Field

[0001] This utility model relates to the field of boiler technology, and more specifically, to a mixed-air heating furnace. Background Technology

[0002] In industrial production (such as material drying and equipment preheating) and residential heating, hot air, as a clean and efficient heat carrier, is widely used for heat transfer and ambient temperature control. To meet the diverse needs for hot air temperature and volume in different scenarios, the mixed-air heating furnace has become one of the core pieces of equipment. It mixes high-temperature gases generated by combustion with ambient-temperature cold air in a specific ratio to output hot air that meets the target parameters, combining heating efficiency with adaptability to different operating conditions.

[0003] While current mixed-air heating furnaces on the market can achieve the function of mixing hot and cold air, they still have many technical defects in practical applications. Based on the analysis of existing patented technologies, they are difficult to meet the requirements of high efficiency, stability, and energy saving:

[0004] Uneven mixing of hot and cold air: Existing equipment often uses a mixing method where cold air is directly introduced into the high-temperature airflow channel, lacking guiding and buffering structures. For example, in the "Energy-saving Hot Air Heater" published in CN 109099583 A, cold air is directly introduced into the hot air chamber to merge with the high-temperature gas without a dedicated mixing channel or guiding structure. This results in only initial contact between hot and cold air in localized areas, easily leading to localized overheating and substandard temperatures in the hot air, and large fluctuations in the output hot air temperature (usually ±5℃ or more). This problem is also reflected in the "Secondary Network Heating Temperature Control Device Based on Negative Pressure Mixing Technology" published in CN120466731 A, where the lack of flow field guidance during the mixing and adjustment process leads to similar defects in uneven heat distribution, seriously affecting the process stability in drying, heating, and other scenarios. For example, in material drying, it may cause localized charring or incomplete drying of the material.

[0005] Poor temperature control flexibility: Most heaters rely on a single valve to control the cold air intake, and the cold air has no fixed flow channel constraint. The heater in publication number CN 109099583 A uses single-path air volume control, which is prone to sudden changes in air volume during the adjustment process, making it difficult to accurately match the heat changes of high-temperature gas, resulting in the hot air temperature being difficult to stabilize at the target value quickly. Similarly, although the device in publication number CN120466731A attempts to dynamically adjust the mixing ratio, it still has a response lag problem due to the disconnect between the adjustment structure and the flow channel design. In some operating conditions, it is necessary to stop the machine for calibration, which seriously affects the continuous production efficiency. Utility Model Content

[0006] The purpose of this invention is to provide a mixed-air heating furnace to solve the problem mentioned in the background art that existing equipment mostly adopts a mixing method of directly introducing cold air into a high-temperature airflow channel, which lacks a guiding and buffering structure.

[0007] To achieve the above objectives, this utility model provides a mixed air heating furnace, including a furnace body, a combustion chamber is provided inside the furnace body, a burner is installed at one end of the combustion chamber, an opening is provided at the other end of the combustion chamber, a mixing chamber is provided at the opening of the furnace body near the combustion chamber, and an annular cold air layer is provided between the inner wall of the furnace body and the outer wall of the combustion chamber, one end of the cold air layer is connected to the mixing chamber.

[0008] This design incorporates a core flow system within the furnace body: a combustion chamber, a mixing chamber, and an annular cold air layer. The burner generates high-temperature airflow within the combustion chamber, which flows through an opening at the end of the combustion chamber into the mixing chamber. The annular cold air layer surrounds the outer wall of the combustion chamber, forming a closed annular airflow channel that directly connects to the mixing chamber, providing a fixed flow path for the cold air. This annular cold air layer ensures even distribution of cold air along the outer wall of the combustion chamber, preventing localized concentration. When the high-temperature airflow enters the mixing chamber, it forms an "enveloping" convection with the cold air flowing from the cold air layer—the cold air surrounds the high-temperature airflow, fully diffusing and exchanging heat within the independent mixing chamber, rather than engaging in unconstrained direct collisions.

[0009] Preferably, a hot air outlet is provided at one end of the furnace body near the mixing chamber, and a cold air inlet is provided on the side wall of the furnace body away from the hot air outlet.

[0010] This design places the hot air outlet at the end of the mixing chamber, forming a "mix and discharge" path with the mixing chamber. The mixed hot air can be discharged without flowing a long distance, reducing temperature loss along the way. The cold air outlet is located on the side wall of the furnace body away from the hot air outlet and is connected to the far end of the annular cold air layer, so that the cold air can flow evenly along the entire length of the cold air layer, gradually filling the annular channel and avoiding local accumulation of cold air.

[0011] Preferably, the end of the cold air layer away from the mixing chamber is provided with several adjustable air vents, and the adjustable air vents are equipped with switch valves.

[0012] This setting allows for adjustable air vents located at the end of the cold air layer furthest from the mixing chamber. The cold air volume of a single vent is controlled by opening and closing the valve, achieving a "front-end adjustment, back-end mixing" temperature control logic. Before entering the cold air layer, the cold air is first regulated by the vent and then flows along the annular channel to the mixing chamber, avoiding direct interference of the adjustment action with the mixing process. Multiple adjustable vents can be controlled independently, and the cold air volume can be adjusted in a stepwise manner by "partially opening and partially closing" or "different vents at different opening degrees," rather than the crude "fully open / fully closed" control of a single valve.

[0013] Preferably, the adjustable air vents are arranged in a ring with equal spacing.

[0014] This setting allows for the adjustment of the vents to be arranged at equal intervals in a ring, which is compatible with the structure of the ring-shaped cold air layer. This allows cold air to enter the cold air layer from multiple evenly distributed points along the circumference of the furnace body, avoiding excessive cold air in one direction and insufficient cold air in another. The equal interval design ensures that the airflow pressure is consistent in all areas within the cold air layer, and there are no "dead zones" when the cold air flows along the outer wall of the combustion chamber, forming a stable ring-shaped airflow field.

[0015] Preferably, the diameter of the opening at the end of the combustion chamber near the mixing chamber is smaller than the internal diameter of the combustion chamber.

[0016] This design features a combustion chamber end opening diameter smaller than the internal diameter, forming a "constriction structure." After the high-temperature airflow is fully combusted inside the combustion chamber, its cross-sectional area decreases as it flows out through the constriction, significantly increasing the flow velocity according to fluid mechanics principles. The high-speed, high-temperature airflow creates a local negative pressure within the mixing chamber, generating a "suction effect" that actively draws cold air from the annular cold air layer into the mixing chamber, enhancing the convective mixing of hot and cold air, rather than passively drawing in cold air due to its own pressure.

[0017] Preferably, the inner wall of the furnace body is provided with a heat insulation layer near the mixing chamber.

[0018] The mixing chamber is the core area for mixing hot and cold air, and the temperature is relatively high. An insulation layer is installed on the inner wall of the furnace near the mixing chamber to directly block the high temperature of the mixing chamber from being transferred to the furnace wall. The insulation layer forms a "thermal barrier" to prevent the furnace surface temperature from becoming too high due to absorbing heat from the mixing chamber, while also reducing the loss of heat to the external environment of the furnace.

[0019] Preferably, the heat insulation layer is made of aluminum silicate fiberboard, and the inner surface of the heat insulation layer is coated with a high-temperature resistant ceramic coating with a thickness of 0.8-1.5 mm.

[0020] This design incorporates aluminum silicate fiberboard, which has a low thermal conductivity, serving as a basic insulation layer to block conductive heat. Its inner high-temperature resistant ceramic coating not only withstands the high temperatures of the mixing chamber but also reflects high-temperature radiant heat, forming a dual insulation system of "conductive blocking + radiative reflection." The ceramic coating thickness is controlled between 0.8-1.5mm, ensuring effective reflection without increasing furnace weight or affecting the internal flow field of the mixing chamber due to excessive thickness. Simultaneously, the ceramic coating protects the aluminum silicate fiberboard from direct erosion by high-temperature airflow, preventing damage.

[0021] Preferably, the bottom of the furnace body is equipped with support legs, and the top of the furnace body is equipped with lifting lugs.

[0022] The furnace body features a rigid support structure at the bottom, allowing direct contact with the ground for stable, flat installation. The top lifting lugs are designed for load-bearing and can be used with lifting equipment for high-altitude suspension installation. The two installation methods are independent and do not conflict with each other. Both the support legs and lifting lugs are integrated into the furnace body, eliminating the need for additional welding or accessories and ensuring the structural integrity of the furnace.

[0023] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0024] In this mixed-air heating furnace, the opening diameter of the combustion chamber near the mixing chamber is smaller than its internal diameter. When the high-temperature airflow exits through this smaller opening, its velocity increases, creating a localized negative pressure within the mixing chamber, which powers the introduction of cold air. An annular cold air layer between the furnace body and the combustion chamber ensures that the cold air is evenly distributed along the outer wall of the combustion chamber, forming an annular airflow that envelops the high-temperature airflow and prevents localized cold air concentration. The cold air layer is directly connected to the mixing chamber, allowing for thorough convection and diffusion of hot and cold air within independent mixing chambers, rather than initial contact in an open channel. This design significantly reduces the temperature fluctuation range of the output hot air, completely resolving the issues of localized coking during material drying and fluctuating heating temperatures, thus meeting the process requirements of high-precision heating scenarios.

[0025] An adjustable air vents arranged in a ring at equal intervals are set at the end of the cold air layer away from the mixing chamber. Each air vent is equipped with an independent on / off valve. The cold air volume can be controlled in a step-like and linear manner by adjusting one or more air vents in a coordinated manner, avoiding sudden changes in air volume caused by adjusting a single valve. The ring-shaped distribution of air vents ensures uniform airflow pressure within the cold air layer and stable cold air velocity during adjustment. It can quickly match the heat changes of high-temperature gas in the combustion chamber, significantly accelerating the response speed of hot air temperature adjustment. No shutdown calibration is required, ensuring the continuity of industrial production. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0027] Figure 2 This is a side view of the structure of this utility model;

[0028] Figure 3 This is a top view of the structure of this utility model;

[0029] The meanings of the labels in the diagram are as follows:

[0030] 1. Furnace body; 11. Hot air outlet; 12. Cold air inlet; 13. Adjustable air inlet; 14. Insulation layer; 15. Support legs; 16. Lifting lugs; 2. Combustion chamber; 3. Burner; 4. Mixing chamber; 5. Cold air layer. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0032] This utility model provides a mixed air heating furnace, such as Figure 1 , Figure 2 , Figure 3 As shown, the furnace includes a furnace body 1, a combustion chamber 2 is provided inside the furnace body 1, a burner 3 is installed at one end of the combustion chamber 2, and an opening is provided at the other end of the combustion chamber 2. A mixing chamber 4 is provided inside the furnace body 1 near the opening of the combustion chamber 2. An annular cold air layer 5 is provided between the inner wall of the furnace body 1 and the outer wall of the combustion chamber 2, and one end of the cold air layer 5 is connected to the mixing chamber 4.

[0033] The furnace body 1 is internally constructed with a core flow channel system consisting of "combustion chamber 2 - mixing chamber 4 - annular cold air layer 5". The burner 3 generates high-temperature airflow within the combustion chamber 2, which flows through the end opening of the combustion chamber to the mixing chamber 4. The annular cold air layer 5 surrounds the outer wall of the combustion chamber 2, forming a closed annular airflow channel that is directly connected to the mixing chamber 4, providing a fixed flow path for the cold air. The annular cold air layer 5 ensures that the cold air is evenly distributed along the outer wall of the combustion chamber 2, preventing localized concentration. When the high-temperature airflow enters the mixing chamber 4, it forms an "enveloping" convection with the cold air flowing from the cold air layer 5—the cold air surrounds the high-temperature airflow, fully diffusing and exchanging heat within the independent mixing chamber, rather than engaging in unconstrained direct collisions.

[0034] This technology solves the problem of uneven mixing caused by the direct convergence of hot and cold air in existing technologies, enabling more thorough mixing of hot and cold air and laying a structural foundation for outputting hot air at a stable temperature. The closed flow channel design of the annular cold air layer 5 avoids cold air leakage or turbulence, improves airflow utilization, and reduces energy waste.

[0035] In this embodiment, as Figure 1 , Figure 2 , Figure 3 As shown, a hot air outlet 11 is provided at one end of the furnace body 1 near the mixing chamber 4, and a cold air outlet 12 is provided on the side wall of the furnace body 1 away from the hot air outlet 11.

[0036] Hot air outlet 11 is located at the end of mixing chamber 4, forming a "mix and discharge" path with mixing chamber 4. The mixed hot air can be discharged without long-distance flow, reducing temperature loss along the way. Cold air outlet 12 is located on the side wall of furnace body 1 away from hot air outlet, and is connected to the far end of annular cold air layer 5, so that cold air can flow evenly along the entire length of cold air layer 5, gradually filling the annular channel and avoiding local accumulation of cold air.

[0037] Optimize the airflow path to avoid localized overheating caused by hot air stagnation in the furnace, while ensuring a stable supply of cold air and improving overall airflow efficiency; stagger the inlet and outlet layout, with the hot air outlet in front and the cold air outlet behind, to avoid "short-circuiting" between hot and cold air, and ensure that the unmixed cold air is discharged directly from the hot air outlet, ensuring that every part of the cold air participates in heat exchange.

[0038] Specifically, such as Figure 2 As shown, the end of the cold air layer 5 away from the mixing chamber 4 is provided with several adjustable air vents 13, and the adjustable air vents 13 are equipped with switch valves.

[0039] Adjustable air vents 13 are located at the end of the cold air layer 5 away from the mixing chamber 4. The cold air volume of a single air vent is controlled by the opening and closing of the valve, realizing the temperature control logic of "front-end adjustment and back-end mixing" - the cold air is adjusted by the air vent before entering the cold air layer, and then flows to the mixing chamber along the annular channel, avoiding the adjustment action from directly interfering with the mixing process; multiple adjustable air vents are controlled independently, and the cold air volume can be adjusted in a step-by-step manner by "partially opening and partially closing" or "different openings of different air vents", rather than the crude control of "fully open / fully closed" of a single valve.

[0040] It solves the problems of lagging temperature regulation and sudden changes in air volume in existing technologies, and achieves precise control of cold air volume, thereby quickly matching the heat changes of high-temperature airflow and stabilizing the hot air temperature; the air outlet can be adjusted by valve without stopping the machine, ensuring continuous operation of the equipment and adapting to scenarios such as industrial production lines that require uninterrupted heating.

[0041] Furthermore, the adjustable air vents 13 are arranged in a ring with equal spacing.

[0042] The adjustable air vents 13 are arranged in a ring with equal spacing, which is adapted to the structure of the ring-shaped cold air layer 5. This allows cold air to enter the cold air layer from multiple evenly distributed points in the circumference of the furnace body, avoiding the situation of excessive cold air in one direction and insufficient cold air in another direction. The equal spacing design ensures that the airflow pressure in each area of ​​the cold air layer 5 is consistent, and there are no "dead corners" when the cold air flows along the outer wall of the combustion chamber 2, forming a stable ring-shaped airflow field.

[0043] Further improve the uniformity of cold air distribution, avoid uneven mixing of cold and hot air caused by local concentration of cold air, and reduce the range of hot air temperature fluctuations; a stable airflow field reduces turbulence loss in the cold air layer, improves cold air flow efficiency, and reduces the energy consumption of auxiliary equipment such as fans.

[0044] Furthermore, such as Figure 1 As shown, the diameter of the opening at the end of the combustion chamber 2 near the mixing chamber 4 is smaller than the internal diameter of the combustion chamber 2.

[0045] The diameter of the opening at the end of the combustion chamber 2 is smaller than the internal diameter, forming a "constriction structure". After the high-temperature airflow is fully burned inside the combustion chamber, the cross-sectional area decreases when it flows out through the constriction. According to the principle of fluid mechanics, the flow velocity is significantly increased. The high-speed flowing high-temperature airflow forms a local negative pressure in the mixing chamber 4, producing a "suction effect", which actively draws the cold air in the annular cold air layer 5 into the mixing chamber, enhancing the convective mixing of hot and cold air, rather than passively flowing in due to the pressure of the cold air itself.

[0046] Enhanced hybrid power of hot and cold air solves the problem of insufficient mixing caused by "passive contact" of hot and cold air in traditional equipment, reducing the phenomenon of local overheating or substandard temperature in the mixing chamber; no additional fans or other air diversion equipment are needed, active mixing is achieved through structural design, reducing the overall energy consumption and complexity of the equipment.

[0047] Furthermore, such as Figure 1 As shown, a heat insulation layer 14 is provided on the inner wall of the furnace body 1 near the mixing chamber 4.

[0048] The mixing chamber 4 is the core area for mixing hot and cold air. The temperature is relatively high and close to that of the high-temperature airflow. A heat insulation layer 14 is installed on the inner wall of the furnace body 1 near the mixing chamber 4, which can directly block the high temperature of the mixing chamber from being transferred to the furnace body wall. The heat insulation layer 14 forms a "thermal barrier" to prevent the surface temperature of the furnace body 1 from becoming too high due to absorbing heat from the mixing chamber, while reducing the loss of heat to the external environment of the furnace body.

[0049] This addresses the heat loss problem caused by the single insulation method in existing equipment, reducing energy waste; it also lowers the surface temperature of the furnace body, eliminating the safety hazard of burns to operators and preventing thermal interference from high temperatures to surrounding electrical equipment and pipelines.

[0050] Furthermore, the heat insulation layer 14 is made of aluminum silicate fiberboard, and the inner surface of the heat insulation layer 14 is coated with a high-temperature resistant ceramic coating with a thickness of 0.8-1.5mm.

[0051] Alumina silicate fiberboard has a low thermal conductivity, which can block conductive heat as a basic insulation layer. Its inner high-temperature resistant ceramic coating can not only withstand the high temperature of the mixing chamber, but also reflect high-temperature radiant heat, forming a dual insulation system of "conductive blocking + radiative reflection". The thickness of the ceramic coating is controlled at 0.8-1.5mm, which can ensure the reflection effect without increasing the weight of the furnace body or affecting the internal flow field of the mixing chamber due to excessive thickness. At the same time, the ceramic coating can protect the alumina silicate fiberboard and prevent the high-temperature airflow from directly scouring and damaging the fiberboard.

[0052] Compared to traditional single insulation materials, composite insulation structures significantly improve insulation efficiency, further reduce heat loss, and lower equipment operating costs; extend the service life of the insulation layer, reduce the frequency of insulation material replacement, and lower maintenance costs; the high-temperature resistance of the ceramic coating is suitable for the high-temperature operating conditions of the mixing chamber, improving the overall durability of the equipment.

[0053] Furthermore, such as Figure 1 As shown, the bottom of the furnace body 1 is equipped with support legs 15, and the top of the furnace body 1 is equipped with lifting lugs 16.

[0054] The support legs 15 at the bottom of the furnace body 1 adopt a rigid support structure, which can directly contact the ground and achieve stable flat installation; the lifting lugs 16 at the top adopt a load-bearing design, which can be used with lifting equipment such as cranes and hoists to achieve high-altitude suspension installation. The two installation methods are independent of each other and do not conflict; the support legs 15 and the lifting lugs 16 are both integrated into the furnace body, without the need for additional welding or accessories, ensuring the integrity of the furnace body structure.

[0055] It solves the problem of the limited installation methods of existing equipment, and can be adapted to different scenarios such as ample ground space and no ground installation location, such as workshop floors and next to high-altitude drying production lines; it eliminates the need to customize special installation structures for specific scenarios, reduces the equipment adaptation cost for users, and broadens the application scope of the equipment.

[0056] When the mixed air heating furnace of this utility model is in use, after the equipment is powered on or fuel is supplied, the burner 3 is started, and the fuel is ignited and continuously burned in the combustion chamber 2. The enclosed space of the combustion chamber 2 allows the heat generated by combustion to accumulate continuously, and the air is heated to form a high-temperature airflow. The temperature can be adjusted according to the fuel type and combustion load. After the high-temperature airflow has fully exchanged heat in the combustion chamber 2, it gradually flows towards the end opening.

[0057] External cold air enters the annular cold air layer 5 through the cold air inlet 12 on the far side wall of the furnace body 1, and evenly fills the annular channel along the outer wall of the combustion chamber 2. According to the target hot air temperature requirement, the operator adjusts the valve of the adjustable air inlet 13 at the far end of the cold air layer 5: if it is necessary to increase the hot air temperature, reduce the opening degree of one or more air inlet valves to reduce the cold air volume; if it is necessary to decrease the hot air temperature, increase the valve opening degree to increase the cold air volume. The annular equidistant layout ensures that the airflow pressure in the cold air layer 5 is uniform, without local accumulation or gaps.

[0058] The high-temperature airflow in combustion chamber 2 flows out through the end constriction structure. Due to the reduced cross-sectional area, the flow velocity is significantly increased, forming a local negative pressure in mixing chamber 4. The "suction effect" generated by the negative pressure draws the regulated cold air in cold air layer 5 into mixing chamber 4. The cold air surrounds and envelops the high-temperature airflow, allowing for full convection, diffusion, and heat exchange in mixing chamber 4. The high-temperature airflow transfers heat to the cold air, which absorbs the heat and its temperature rises, ultimately forming a uniformly heated mixed airflow. During this stage, the composite insulation layer 14 blocks the transfer of high temperature from mixing chamber 4 to furnace body 1, preventing heat loss.

[0059] The mixed hot air, under the action of airflow pressure, is directly discharged from the hot air outlet 11 at the end of the furnace body 1 via a "mix and discharge" path, reducing temperature loss along the way and delivering it to end-user demand scenarios such as drying equipment and heating pipes. During continuous operation, the hot air temperature can be monitored in real time. For example, by installing a temperature sensor, the valve opening of the adjustable air outlet 13 can be dynamically adjusted to ensure that the hot air temperature remains stable within the target range. At the same time, the heat insulation layer 14 continues to play its role, maintaining the surface temperature of the furnace body 1 within a safe range and preventing burns to operators.

[0060] When hot air output is no longer required, first turn off the fuel supply to burner 3. After the remaining fuel in combustion chamber 2 is burned out and the high-temperature airflow gradually cools down, stop the cold air supply. If the equipment needs to be moved or disassembled, it can be moved smoothly using the bottom support legs 15, or transferred with the top lifting lugs 16 in conjunction with lifting equipment, to meet the storage or replacement needs of different sites.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A mixed-air heating furnace, comprising a furnace body (1), characterized in that: The furnace body (1) is provided with a combustion chamber (2) inside. A burner (3) is installed at one end of the combustion chamber (2). An opening is provided at the other end of the combustion chamber (2). A mixing chamber (4) is provided at the opening of the furnace body (1) near the combustion chamber (2). An annular cold air layer (5) is provided between the inner wall of the furnace body (1) and the outer wall of the combustion chamber (2). One end of the cold air layer (5) is connected to the mixing chamber (4).

2. The mixed-air heating furnace according to claim 1, characterized in that: A hot air outlet (11) is provided at one end of the furnace body (1) near the mixing chamber (4), and a cold air inlet (12) is provided on the side wall of the furnace body (1) away from the hot air outlet (11).

3. The mixed-air heating furnace according to claim 1, characterized in that: The cold air layer (5) is provided with several adjustable air vents (13) at the end away from the mixing chamber (4), and the adjustable air vents (13) are equipped with switch valves.

4. The mixed-air heating furnace according to claim 3, characterized in that: The adjustable air vents (13) are arranged in a ring with equal spacing.

5. The mixed-air heating furnace according to claim 1, characterized in that: The diameter of the opening at the end of the combustion chamber (2) near the mixing chamber (4) is smaller than the internal diameter of the combustion chamber (2).

6. The mixed-air heating furnace according to claim 1, characterized in that: The inner wall of the furnace body (1) is provided with a heat insulation layer (14) near the mixing chamber (4).

7. The mixed-air heating furnace according to claim 6, characterized in that: The heat insulation layer (14) is made of aluminum silicate fiberboard, and the inner surface of the heat insulation layer (14) is coated with a high-temperature resistant ceramic coating with a thickness of 0.8-1.5 mm.

8. The mixed-air heating furnace according to claim 1, characterized in that: The bottom of the furnace body (1) is equipped with support legs (15), and the top of the furnace body (1) is equipped with lifting lugs (16).

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