Self-generating temperature difference heater and control method thereof

Abstract

The invention discloses a self-power-generation temperature difference heater, and belongs to the technical field of vehicle fuel heaters. Comprising a fuel heater body, an independently-arranged thermoelectric power generation module, a backflow pipeline, an adjustable flow guide valve, a static mixer and a controller. The thermoelectric power generation module is connected to the downstream of an exhaust pipe of the heater body in series, the hot end of the thermoelectric power generation module adopts variable cross-section twisted tooth spiral turbulent flow fins to enhance heat exchange, the cold end is forcibly cooled by a warm air fan, and generated preheated air controls the backflow proportion through an adjustable flow guide valve, is mixed with fresh air through a static mixer and then enters an air inlet of the heater. And an electric-thermal positive feedback closed loop is formed. The controller adjusts the backflow proportion in real time according to the exhaust temperature, the environment temperature and power generation output, low-temperature quick starting and high-load overheating prevention are achieved, and the overall fuel utilization rate is increased by 8%-15% compared with a traditional scheme. The device is independent in structure, easy to refit and suitable for self-sustaining power supply and energy-saving optimization of the vehicle-mounted fuel heater.

Description

Technical Field

[0001] This invention belongs to the technical field of automotive fuel heaters, and more specifically, relates to a self-generating thermoelectric heater and its control method. Background Technology

[0002] Fuel heaters are widely used in outdoor camping, vehicle heating, and other applications. They typically consist of an ignition device, fuel pump, fuel injection system, combustion fan, combustion chamber, radiator, and heater fan. Their working principle is as follows: Under the action of the combustion fan, outside air enters the combustion chamber through the air inlet, mixes with fuel injected by the fuel injection system, and is ignited and burned by the ignition device. The hot air generated by combustion flows through the radiator's internal fins and is then discharged from the exhaust port. The hot air flowing through the radiator's internal fins transfers heat to the radiator. Under the action of the heater fan, cold air enters the fuel heater through the air inlet, is heated after flowing through the radiator's external fins, and then flows out from the air outlet.

[0003] Existing fuel oil heaters require an external power source to operate (fuel pumps, combustion fans, heaters, ignition devices, etc. all require power), causing significant inconvenience to customers. Furthermore, the exhaust temperature of fuel oil heaters is relatively high, and this hot air is directly discharged into the atmosphere, resulting in substantial heat waste.

[0004] Chinese patent CN110641251A discloses a semiconductor thermoelectric generator fuel-fired heater, including a casing, a combustion chamber inside the casing, a burner inside the combustion chamber, an inlet at the front end of the burner, and several flue gas outlets at the rear end of the burner, which are connected to the space inside the combustion chamber; a flue gas passage is formed between the outer wall of the burner and the combustion chamber; a flue gas outlet is provided at one end of the combustion chamber, and the flue gas passage is connected to the chimney through the flue gas outlet; a thermoelectric generator module is installed on the outer wall of the combustion chamber, and a torsion-tooth spiral fin radiator is installed on the thermoelectric generator module. This device can generate electricity for its own electrical devices while providing heating to users. This thermoelectric generator parking heater can achieve full utilization of energy and is widely used for heating in long-distance trucks, buses, etc.

[0005] The above technical solution has the following drawbacks:

[0006] However, this method results in the radiator's outer fins not being an integral structure with the radiator, making the structure relatively complex. More importantly, the heat from the radiator needs to be conducted to the outer fins through the semiconductor thermoelectric generator, which greatly reduces the heat exchange efficiency. Another solution attempts to recirculate the cold-end air of the power generation module to preheat the intake air, but it lacks dynamic control and is prone to problems such as difficulty in low-temperature start-up or unstable combustion and flame extinction under high-temperature conditions. In the existing technology, there is no complete solution that simultaneously adopts an independent power generation module, a specific geometric turbulence enhancement structure, and an adjustable closed-loop recirculation control. There is still considerable room for improvement in adaptability and energy-saving effect. Summary of the Invention

[0007] To address the above deficiencies, the present invention provides a self-generating thermoelectric heater, comprising a fuel-fired heater and a thermoelectric power generation module;

[0008] The fuel-fired heater includes a housing, inside which a heater and a combustion fan connected to the fan inlet are installed, and inside the housing is a radiator connected to the fan outlet.

[0009] The thermoelectric power generation module includes a housing 1 and a housing 2, which are fixedly connected. The housing 1 has several fin groups installed inside, and each fin group includes a cold end fin and a hot end fin, as well as a power generation piece for connecting the two. The side of the housing 1 away from the fuel-fired heater is the cold end air inlet, and the housing 2 is connected to the fan air inlet through the cold end air outlet.

[0010] The exhaust port of the fan at the bottom of the radiator is connected to the hot end air inlet at one point of the housing through an exhaust pipe. The bottom of the housing is also provided with a combustion air inlet and an oil inlet. A hot end exhaust port is provided on the side of the housing opposite to the hot end air inlet.

[0011] The interior of the cold end air outlet is also equipped with an adjustable flow guide valve for adjusting the recirculation ratio, and the combustion air inlet is equipped with a static mixer for uniformly mixing the recirculated preheated air and fresh air, as well as several sensors for collecting data.

[0012] It also includes a controller for dynamically adjusting the opening of the adjustable guide valve based on exhaust temperature, ambient temperature, and generator output signal.

[0013] Furthermore, the radiator includes a combustion chamber, an ignition device is installed on the side of the combustion chamber near the combustion fan, and an inner radiator fin and an outer radiator fin are provided through the top of the combustion chamber.

[0014] Furthermore, the number of fin groups is three, and both the cold-end fins and the hot-end fins are fins adapted to thermoelectric generators. Both the cold-end fins and the hot-end fins are conventional rectangular fins. The three fin groups are stacked correspondingly, and the cold-end fins and hot-end fins of adjacent fin groups are in contact.

[0015] Furthermore, the number of fin groups is three, and both the cold end fins and the hot end fins are fins adapted to thermoelectric generators. Both the cold end fins and the hot end fins are rectangular fins with variable cross-section twisted tooth spiral shape.

[0016] The fin root width is 6-12mm, the top width is 12-22mm, the root twist angle is 30°-45°, the top twist angle is 40°-55°, the three fin groups are stacked correspondingly, and the cold end fins and hot end fins of adjacent fin groups are in contact with each other and arranged densely in front and sparsely in back along the airflow direction, with a tooth opening rate of 20%-40%.

[0017] Furthermore, the fin assembly is reinforced at the cold end air inlet by a plug-in support frame.

[0018] The present invention also discloses a control method for the above-mentioned self-generating thermoelectric heater, comprising the following steps:

[0019] S1. During the system startup phase, the adjustable guide valve is controlled to be at a high backflow opening.

[0020] S2. Real-time data collection of exhaust temperature, ambient temperature, and power generation output via several sensors;

[0021] S3. Dynamically adjust the reflux ratio based on the acquired signal to enhance preheating in low-temperature conditions and prevent overheating in high-temperature conditions.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The thermoelectric power generation module is set up independently and is connected in series with the exhaust pipe in the downstream exhaust path of the radiator of the fuel-fired heater. It does not change the original heat exchange structure and airflow organization of the combustion chamber, the inner fins and the outer fins of the radiator. Therefore, it does not affect the heat exchange performance of the radiator. The original warm air outlet temperature, heating rate and heating effect remain basically unchanged (the change range is usually less than 3-5℃, and the thermal response time is extended by no more than 5%).

[0024] 2. The hot-end fins adopt a variable cross-section twisted tooth spiral design, which significantly enhances the convective heat transfer on the exhaust side, increases the temperature difference between the hot and cold ends, and improves the power generation density by 40% to 80% compared with ordinary fins (the module output power can reach 30 to 60W under typical operating conditions).

[0025] 3. The cold-end air recirculation ratio is dynamically adjusted by an adjustable guide valve, and combined with a static mixer to evenly mix the recirculated preheated air and fresh combustion air, forming a heat-electric positive feedback closed loop: during the low-temperature start-up phase, a high recirculation ratio (80%~100%) rapidly preheats the intake air and shortens the start-up time (more than 30% shorter at -20℃); under high-temperature or high-load conditions, the recirculation ratio is automatically reduced to prevent overheating, and the power output fluctuation is controlled within ±15%.

[0026] 4. The overall energy utilization rate is 8% to 15% higher than that of traditional pure electric drive or non-recirculation preheating solutions, making it particularly suitable for extremely cold environments and long-term low-power parking heating conditions.

[0027] 5. The thermoelectric generator module has an independent structure and simple interface. It only needs to be connected to the exhaust pipe and return path, which makes it easy to retrofit and upgrade existing commercially available fuel-fired heaters. It is convenient to maintain and has low modification costs. Attached Figure Description

[0028] Figure 1 This is a cross-sectional schematic diagram of the fuel-fired heater in this invention.

[0029] Figure 2 This is a perspective view of the fuel-fired heater of the present invention.

[0030] Figure 3 This is a perspective view of the thermoelectric power generation module in this invention.

[0031] Figure 4 This is a schematic diagram showing the position of the support frame in this invention.

[0032] Figure 5 This is a schematic diagram of the three groups (conventional rectangular) of fins in this invention.

[0033] Figure 6 This is a distribution diagram of the variable cross-section torsion toothed spiral rectangular fins in this invention.

[0034] Figure 7 This is a schematic diagram of the variable cross-section torsion toothed spiral rectangular fin in this invention.

[0035] In the diagram: 1. Fuel-fired heater; 2. Thermoelectric generator module; 3. Exhaust pipe; 4. Fan inlet; 5. Fan outlet; 6. Combustion air inlet; 7. Fan exhaust outlet; 8. Oil inlet; 9. Heater; 10. Combustion fan; 11. Ignition device; 12. Combustion chamber; 13. Radiator; 14. Hot end air inlet; 15. Hot end exhaust outlet; 16. Cold end air inlet; 17. Cold end air outlet; 18. Support frame; 20. Hot end fins; 21. Cold end fins; 19. Generator plate; 131. Inner fins of the radiator; 132. Outer fins of the radiator. Detailed Implementation

[0036] 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.

[0037] Example 1

[0038] like Figures 1 to 5 As shown, this embodiment provides a self-generating thermoelectric heater, including a fuel-fired heater 1 and a thermoelectric power generation module 2;

[0039] The fuel-fired heater 1 includes an outer casing, inside which a heater fan 9 and a combustion fan 10 are installed. The air inlet side of the heater fan 9 is connected to the air inlet 4, and its air outlet side is connected to the air outlet 5. A radiator 13 is also installed inside the outer casing, and the radiator 13 is connected to the air outlet 5. The radiator 13 is connected to the air outlet of the heater fan 9 and is used to transfer the heat generated by combustion to the circulating air.

[0040] The radiator 13 includes a combustion chamber 12. An ignition device 11 is installed on the side of the combustion chamber 12 near the combustion fan 10. The top of the combustion chamber 12 is provided with an inner radiator fin 131 (located on the combustion flue gas side) and an outer radiator fin 132 (located on the warm air side). The inner radiator fin 131 and the outer radiator fin 132 together form a heat exchange structure to achieve efficient heat exchange between the waste heat of the flue gas and the intake air.

[0041] Thermoelectric module 2 includes housing 1 and housing 2, which are fixedly connected to form an integral module. Housing 1 has three sets of fins installed inside, each set of fins including cold end fins 21 and hot end fins 20, as well as a power generation plate 19 for connecting the two (the thermocouple material is usually BiTe-based or PbTe-based). The cold end fins 21 and hot end fins 20 are respectively attached to the two sides of the power generation plate 19 to achieve efficient heat conduction. The side of housing 1 away from the fuel-fired heater 1 is the cold end air inlet 16. In addition, the fins are reinforced at the cold end air inlet 16 by a plug-in support frame 18 to prevent the fins from shifting due to vibration or airflow impact.

[0042] The three fin groups are stacked in the direction of airflow. The cold end fins 21 and hot end fins 20 of adjacent fin groups are in contact with each other or closely attached to each other to increase the overall heat exchange area and reduce the contact thermal resistance. In this embodiment, both the cold end fins 21 and the hot end fins 20 are conventional rectangular fins.

[0043] The second housing is connected to the air inlet 4 of the fuel-fired heater 1 via the cold end air outlet 17, forming a cold end air return path; the air outlet 7 at the bottom of the radiator 13 is connected to the hot end air inlet 14 of the first housing via the exhaust pipe 3; a hot end exhaust outlet 15 is provided on the side of the first housing opposite to the hot end air inlet 14, for discharging cooled flue gas.

[0044] The bottom of the casing is also provided with a combustion air inlet 6 and an oil inlet 8;

[0045] An adjustable guide valve is installed inside the cold end air outlet 17 (or at the beginning of the return path) to adjust the proportion of cold end air returning to the fan inlet 4 in real time; a static mixer is installed at the combustion air inlet 6 to uniformly mix the return preheated air with the ambient fresh air before it enters the combustion air fan 10; several sensors (including but not limited to exhaust temperature sensor, ambient temperature sensor, and generator output voltage / current sensor) are also installed near the combustion air inlet 6 and at key measuring points to collect operating status data.

[0046] It also includes a controller, which is electrically connected to the adjustable guide valve and various sensors. Based on the collected exhaust temperature, ambient temperature and power generation output signal, the controller dynamically adjusts the opening of the guide valve using a preset algorithm (such as PID control or fuzzy control) to achieve closed-loop regulation of the return flow ratio.

[0047] Using the structure of this embodiment, the system can achieve stable self-generating operation at normal ambient temperatures (above 0°C), with a power generation range of 15 to 35W. The cold end recirculation preheating has a certain temperature-raising effect on the combustion air, which helps to improve combustion efficiency and the overall energy utilization rate of the system.

[0048] It should be noted that the blue arrows indicate the entry and exit paths of the warm air, while the red arrows indicate the entry and exit paths of the combustion air.

[0049] Example 2

[0050] The difference from Embodiment 1 is that both the cold-end fin 21 and the hot-end fin 20 are rectangular fins with variable cross-section twisted tooth spirals, such as... Figure 6-7 As shown;

[0051] The specific structural parameters are as follows: the fin root width is 6-12 mm, the top width is 12-22 mm; the root twist angle is 30°-45°, and the top twist angle is 40°-55°; the three fin groups are stacked in the direction of airflow, and the cold end fin 21 and the hot end fin 20 of the adjacent fin groups are in contact with each other; the fins are arranged in a dense front and sparse rear pattern along the direction of flue gas / air flow (the pitch is smaller and the tooth density is higher in the front section, and the pitch is increased and the tooth density is reduced in the rear section), and the tooth opening rate is controlled at 20%-40%.

[0052] After adopting the above-mentioned variable cross-section torsion tooth spiral turbulence fins, the local convective heat transfer coefficient on the exhaust side is significantly improved compared with the straight fins of Example 1 (the improvement is about 40% to 80%). The hot end fin 20 can more efficiently transfer the exhaust waste heat to the thermoelectric generator 19. At the same time, the spiral torsion tooth structure and variable cross-section design enhance the boundary layer disturbance and secondary flow effect, effectively suppressing carbon deposition and local overheating. The forced convection heat transfer on the cold end fin 21 side is also enhanced, so that the temperature difference between the hot end and the cold end can be increased by 20 to 50°C under the same exhaust conditions. Under typical operating conditions, the output power of the thermoelectric generator module 2 can be increased to 30 to 60W, which is a significant improvement compared with Example 1.

[0053] Example 3

[0054] This embodiment is based on the control method of the self-generating thermoelectric heater in Embodiments 1-2, and specifically includes the following steps:

[0055] S1. During the system startup phase, the controller controls the adjustable guide valve to be at a high recirculation opening (preferably 80% to 100%), so that as much cold-end preheated air as possible is recirculated to the combustion air inlet 6, which quickly increases the temperature of the combustion air entering the combustion chamber 12 and shortens the time from ignition to stable combustion.

[0056] S2. During system operation, the controller collects the exhaust temperature T_exhaust, the ambient temperature T_ambient, and the output power P (or voltage / current) of the thermoelectric generator module 2 in real time.

[0057] S3. Dynamically adjust the return current ratio based on the acquired signal, specifically including:

[0058] S3-1. When T-row is greater than or equal to the set high temperature threshold (e.g., 450-550℃, depending on the specific model) or T-ring is high, reduce the recirculation ratio (or even shut down part of the recirculation) to avoid excessively high cold end temperature, which could lead to reduced efficiency or overheating damage to the generator cell 19.

[0059] S3-2. When the T loop is low (e.g., below -20℃) or the temperature difference ΔT between the hot and cold ends is small at the initial stage of startup, increase the recirculation ratio to enhance the preheating effect of the air intake and accelerate the establishment of an effective temperature difference.

[0060] S3-3. Through the above closed-loop regulation, the temperature difference between the hot end and the cold end of the thermoelectric power generation module 2 is kept stable in the range of 180℃ to 280℃ for a long time, which not only ensures the power generation efficiency, but also prevents the system from overheating or efficiency collapse.

[0061] Using this control method, the low-temperature start-up time can be shortened by 25% to 40% compared to schemes without reflux or with fixed reflux, and the power generation fluctuation range under high load conditions can be controlled within ±15%, significantly enhancing the overall system adaptability.

[0062] It should be noted that the structure described in this invention can be implemented in many different forms and is not limited to the embodiments described. Any equivalent transformations made by those skilled in the art based on the description and drawings of this invention, or direct or indirect applications in other related technical fields, such as the loading and unloading of other items, are included within the protection scope of this invention.

Claims

1. A self-generating temperature difference heater, characterized in that, Includes fuel-fired heaters and thermoelectric generator modules; The fuel-fired heater includes a housing, inside which a heater and a combustion fan connected to the fan inlet are installed, and inside the housing is a radiator connected to the fan outlet. The thermoelectric power generation module includes a housing 1 and a housing 2, which are fixedly connected. The housing 1 has several fin groups installed inside, and each fin group includes a cold end fin and a hot end fin, as well as a power generation piece for connecting the two. The side of the housing 1 away from the fuel-fired heater is the cold end air inlet, and the housing 2 is connected to the fan air inlet through the cold end air outlet. The number of fin groups is three, and both the cold end fins and the hot end fins are fins adapted to thermoelectric generators. Both the cold end fins and the hot end fins are rectangular fins with variable cross-section twisted tooth spiral shape. The fin root width is 6-12mm, the top width is 12-22mm, the root twist angle is 30°-45°, the top twist angle is 40°-55°, the three fin groups are stacked correspondingly, and the cold end fins and hot end fins of adjacent fin groups are in contact. The exhaust port of the fan at the bottom of the radiator is connected to the hot end air inlet at one point of the housing through an exhaust pipe. The bottom of the housing is also provided with a combustion air inlet and an oil inlet. A hot end exhaust port is provided on the side of the housing opposite to the hot end air inlet. The interior of the cold end air outlet is also equipped with an adjustable flow guide valve for adjusting the recirculation ratio, and the combustion air inlet is equipped with a static mixer for uniformly mixing the recirculated preheated air and fresh air, as well as several sensors for collecting data. It also includes a controller for dynamically adjusting the opening of the adjustable guide valve based on exhaust temperature, ambient temperature, and generator output signal.

2. The self-generating temperature difference heater as described in claim 1, characterized in that: The radiator includes a combustion chamber, an ignition device is installed on the side of the combustion chamber near the combustion fan, and an inner radiator fin and an outer radiator fin are provided through the top of the combustion chamber.

3. The self-generating thermoelectric heater as described in claim 2, characterized in that: The number of fin groups is three, and both the cold end fins and the hot end fins are fins adapted to thermoelectric generators. Both the cold end fins and the hot end fins are conventional rectangular fins. The three fin groups are stacked correspondingly, and the cold end fins and hot end fins of adjacent fin groups are in contact.

4. A self-generating thermoelectric heater as described in claim 3, characterized in that: The fin assembly is reinforced at the cold end air inlet by an inserted support frame.

5. A method for controlling a self-generating thermoelectric heater according to any one of claims 1-4, characterized in that: Includes the following steps: S1. During the system startup phase, the adjustable guide valve is controlled to be at a high backflow opening. S2. Real-time data collection of exhaust temperature, ambient temperature, and power generation output via several sensors; S3. Dynamically adjust the return current ratio based on the acquired signal.

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