Aero vehicle wing built-in hydrogen fuel cell thermal temperature control structure

Abstract

This invention relates to a thermal control structure for an integrated hydrogen fuel cell in an aircraft wing. It utilizes heat pipes for convection or phase change heat transfer, conducting waste heat from the fuel cell to heat-conducting fins and the wing skin. During cruise, forced convection cooling is achieved through airflow. The heat-conducting fins and heat pipes are arranged in a crisscross pattern, allowing the thermal system to manage both the hydrogen fuel cell and the onboard lithium battery. The fuel cell stack adopts a non-rectangular, gradually changing shape adapted to the wing box profile, wider near the front spar and narrower near the rear spar. The electrode plates are made of an aluminum-magnesium alloy substrate with conductive and corrosion-resistant layers, balancing heat dissipation, conductivity, and weight reduction. Corresponding irregular flow channel structures are designed for both forward / backward and up / down gas flow directions, balancing pressure drop and gas residence time. This invention fully utilizes the wing structure space to achieve integrated fuel cell system, heat dissipation, temperature control, and weight reduction, adapting to the complex configurations of various eVTOL and fixed-wing hydrogen aircraft.

Description

Technical Field

[0001] This invention belongs to the field of interdisciplinary technology of aircraft and hydrogen energy. The invention relates to a thermal temperature control structure for a hydrogen fuel cell built into the wing of an aircraft. Background Technology

[0002] As the global aviation industry transforms towards green and intelligent technologies, electric vertical takeoff and landing (eVTOL) aircraft, with their characteristics of low-altitude flexible operation and zero emissions, are becoming the core carriers of future urban air mobility (UAM). Meanwhile, hydrogen energy, as a clean energy source with high energy density and zero carbon emissions, combined with fuel cell technology, is seen as a key solution to address range anxiety in eVTOL or other electric flight systems and overcome the bottleneck of battery energy density. The integrated development of these two technologies has become an important trend in the aviation field.

[0003] Among various types of fuel cells, proton exchange membrane fuel cells (PEMFCs) are widely recognized as the most suitable power system for aircraft due to their advantages such as high power density, fast start-up speed, and relatively low operating temperature. However, the performance of PEMFCs is strictly limited by operating temperature; their optimal operating range is typically 60-80°C, and the maximum tolerable temperature generally does not exceed 90°C. Once this threshold is exceeded, the proton exchange membrane will dehydrate, leading to a sharp drop in proton conduction efficiency and a significant decrease in catalyst activity. In severe cases, this may cause the fuel cell stack to fail, directly threatening flight safety.

[0004] Another significant challenge lies in energy conversion efficiency: PEMFCs typically operate at only around 50% efficiency, meaning about half of the energy is released as waste heat. Compared to electric vehicles, eVTOLs have much more stringent power requirements—they need to output high power instantaneously during takeoff, hovering, and high-speed cruising, resulting in a much higher rate of waste heat generation than ground-based vehicles. In typical family hydrogen-powered passenger vehicles, high-pressure hydrogen storage tanks are usually located under the chassis or behind the rear seats; the fuel cell stack, air compressor, water and heat management module, and other core auxiliary components are centrally integrated in the front compartment. The vehicle's cooling system utilizes the front grille to draw in oncoming airflow, working in conjunction with a large radiator, cooling fan, and liquid cooling circuit to simultaneously dissipate heat and maintain a constant temperature for the fuel cell stack, auxiliary power battery, electronic control system, and air compressor. Among the aforementioned hydrogen power system components, the fuel cell stack, along with its associated cooling system, can account for about half of the total weight of the entire hydrogen power system. Therefore, in the design of hydrogen-powered aircraft, if the front-mounted layout of automotive fuel cells is directly adopted, it will not only easily cause excessive concentrated load on the nose and generate significant nose-down torque, disrupting the pitch torque balance of the entire aircraft, but also the exposed air intake grille will seriously damage the streamlined aerodynamic shape of the fuselage, greatly increasing wind resistance and flight energy consumption, making it difficult to meet the requirements of lightweight and low-drag design of aircraft. Summary of the Invention

[0005] The purpose of this invention is to propose a thermal control structure for hydrogen fuel cells integrated into the wings of aircraft. This invention targets eVTOL aircraft and fixed-wing aircraft with wing structures such as tiltrotor, tilt-ducted, and compound wings, proposing a fuel cell temperature control technology based on wing-integrated heat dissipation. This solves both the heat dissipation problem of proton exchange membrane fuel cells (PEMFCs) in hydrogen fuel cells and the compatibility conflict between existing fuel cell forms and wing space, belonging to the interdisciplinary field of aircraft and hydrogen energy.

[0006] This invention proposes a thermal control structure for an integrated hydrogen fuel cell in an aircraft wing, comprising a fuel cell, heat pipes, coolant, heat dissipation fins, wing skin, wing ribs, and wing spars. The wing skin includes an upper skin and a lower skin, which together form the frame structure of the aircraft wing. The heat pipes include those close to the upper wing surface and those close to the lower wing surface.

[0007] The aircraft wing has a wing box inside its frame structure, where the fuel cell is placed. The heat pipes close to the upper wing surface and the heat pipes close to the lower wing surface are connected to the upper skin and lower skin respectively through heat dissipation fins.

[0008] A fuel cell comprises several fuel cell units connected in series. Each fuel cell unit consists of a cathode plate, an air seal, a membrane electrode assembly, a hydrogen seal, and an anode plate, which are fixedly connected by connectors. The cathode plate has an air flow channel, and the anode plate has a hydrogen flow channel. One side of the fuel cell has an oxygen inlet, a hydrogen inlet, an oxygen outlet, and a hydrogen outlet. The front and rear sides of the fuel cell have a fuel cell coolant outlet and a fuel cell coolant inlet.

[0009] The fuel cell is the main waste heat generating component. One end of the heat pipe is embedded in the fuel cell. The coolant enters the fuel cell through the fuel cell coolant inlet and exits the fuel cell through the fuel cell coolant outlet. The waste heat of the fuel cell is conducted to the heat dissipation fins through the heat pipe, and then exchanges heat with the external airflow through the upper and lower skins to achieve active control of the fuel cell operating temperature.

[0010] During takeoff and landing, the strong airflow generated by the propellers directly acts on the wing skin surface, accelerating heat dissipation through forced convection. Meanwhile, the large amount of waste heat generated by the fuel cell due to its instantaneous high power output is collected by the liquid cooling circuit and conducted to the heat-conducting fins via heat pipes, then rapidly transferred to the skin, achieving efficient cooling with the help of airflow. Once in the cruise phase, the airflow generated by the high-speed flight flows smoothly along the wing surface, continuously carrying away heat from the skin through natural convection and thermal radiation. The coolant in the heat pipes, after being cooled as described above, returns to the fuel cell, forming a cycle.

[0011] In this invention, the fuel cell is a proton exchange membrane fuel cell, the heat pipe is a metal pipe containing a coolant, and the waste heat of the fuel cell is discharged and the coolant is returned to cool through convection or phase change circulation.

[0012] In this invention, the heat dissipation fins are metal heat-conducting components, fixed to the inner side of the upper and lower skins, and the heat dissipation efficiency is improved by increasing the contact area with the heat pipes; the upper and lower skins are made of metal heat-conducting materials, and the aircraft utilizes airflow to force convection heat exchange and cooling of the skins during the cruise phase.

[0013] In this invention, the heat dissipation fins and heat pipes are arranged in a crisscross pattern and are close to the inner side of the upper or lower skin. Where the upper or lower skin can be supported and reinforced, the skin thickness can be reduced, thereby reducing the weight of the aircraft structure.

[0014] In this invention, the heat dissipation system can also be used for thermal management and temperature control of the aircraft's lithium battery system when the hydrogen fuel cell is shut down and not in operation.

[0015] In this invention, the low-temperature fuel cell is adapted to the upper and lower surface contours of the wing and is installed inside the wing box; the stack end plate and each fuel cell unit are non-rectangular in shape, with an overall gradient configuration that is wider near the front wing spars and narrower near the rear wing spars.

[0016] In this invention, the anode plate and cathode plate of the fuel cell unit are made of aluminum-magnesium alloy substrate, and the surface is coated with an anti-corrosion layer. The whole unit has the functions of conductivity, enhanced heat dissipation, corrosion resistance and structural weight reduction. The weight reduction requirement is achieved by appropriately sacrificing product life.

[0017] In this invention, when hydrogen or air flows in the anode and cathode plates along the front-to-back direction of the aircraft, the gas flow channel adopts a layout that is wide at the front and narrow at the back, and curved at the front and straight at the back, so that the pressure drop and gas residence time are evenly distributed in the front and back of the flow channel.

[0018] In this invention, when hydrogen or air flows in the anode plate and cathode plate along the vertical direction of the aircraft, the gas flow channel adopts a layout that is narrow at the front and wide at the back, and straight at the front and curved at the back, so that the pressure drop and gas residence time are evenly distributed before and after the flow channel.

[0019] In this invention, the cryogenic fuel cell is integrated between the wing box load-bearing structure, and the weight balance of the whole machine is achieved by the distributed arrangement. The space inside the fuselage is reserved for arranging hydrogen storage tank components whose shape is not easy to adjust.

[0020] In this invention, a thermally conductive filler material such as thermally conductive grease is placed between the heat pipe and the skin to further enhance the thermal conductivity between the heat pipe and the skin.

[0021] Finally, in order to enhance heat exchange and reduce weight, this invention proposes a process that sacrifices product lifespan by using aluminum-based or magnesium-based alloy coatings and other processes. By utilizing the low density of these materials, they can be used as the main structural materials for fuel cells, effectively improving the power-to-weight ratio of the fuel cell stack and making it more suitable for the needs of the aerospace industry.

[0022] The entire process requires no additional cooling fans or raised cooling devices, ensuring that the fuel cell operating temperature remains stable within a safe range while maintaining the aerodynamic performance of the wing, thus achieving the dual goals of weight reduction and efficient heat dissipation.

[0023] The beneficial effects of this invention are as follows: This invention proposes an integrated cooling scheme based on an airfoil structure. Utilizing the large surface area, high surface velocity, and good load-bearing capacity of the airfoil, this invention optimizes the internal flow channel design of the airfoil, allowing waste heat generated by the fuel cell to be conducted to the airfoil skin, and then efficiently dissipated by the high-speed airflow on the airfoil surface during flight. Secondly, to reduce heat transfer equipment and fully utilize the space within the airfoil, the fuel cell is placed inside the airfoil using a non-rectangular fuel cell shape to match the airfoil's cross-sectional shape. This design brings the fuel cell stack close to the aircraft's center of lift, improving aircraft stability, while eliminating the need for additional cooling fans or protruding radiators. This avoids increased wind resistance, reduces equipment weight, and increases aircraft controllability, perfectly meeting the dual requirements of aerodynamic performance and lightweight design for eVTOL aircraft, providing key technical support for the safe and efficient operation of hydrogen-powered eVTOL aircraft. Attached Figure Description

[0024] Figure 1 This is an exploded view of the system. The labels are as follows: 1 is the upper skin, 2 is the lower skin, 3 is the rib, 4 is the spars, 5 is the fuel cell, 6 is the coolant, 6-1 is the high-temperature coolant outlet after fuel cell heating, 6-2 is the coolant inlet utilizing the upper wing surface for heat dissipation, 6-3 is the coolant outlet utilizing the upper wing surface for heat dissipation, 6-4 is the coolant flow between the upper and lower wing surfaces, 6-5 is the coolant inlet utilizing the lower wing surface for heat dissipation, 6-6 is the coolant outlet utilizing the lower wing surface for heat dissipation, 6-7 is the low-temperature coolant inlet on the fuel cell side, 7 is the heat-conducting fin, 7-1 is the fin on the upper wing surface, 7-2 is the fin on the lower wing surface, 8 is the heat-conducting heat pipe, 8-1 is the heat-conducting heat pipe close to the upper wing surface, 8-2 is the heat-conducting heat pipe close to the lower wing surface. Details within circle A are shown in [the diagram]. Figure 2 It is displayed in the middle.

[0025] Figure 2 for Figure 1The diagram shows the details of the middle circle A. The numbers in the diagram are: 1 is the upper skin, 6-2 is the coolant inlet for heat dissipation using the upper wing surface, 6-3 is the coolant outlet for heat dissipation using the upper wing surface, 7-1 is the heat-conducting fins of the upper wing surface, 7-1-1 is the heat-conducting reinforcing ring, 8-1 is the heat pipe close to the upper wing surface, and 9 is thermally conductive materials such as thermal grease.

[0026] Figure 3 The diagram shows the relationship between the heat pipe location and the wing position. The numbers in the diagram are as follows: 3 is the wing rib, 3-1 is the weight reduction hole, 3-2 is the heat pipe positioning hole, 4-1 is the front spar, 4-2 is the rear spar, 5-1 is the fuel cell unit, 5-2 is the fuel cell coolant outlet, 5-3 is the fuel cell coolant inlet, 5-4 is the end plate, 10-1 is the oxygen inlet, 10-2 is the oxygen outlet, 11-1 is the hydrogen inlet, and 11-2 is the hydrogen outlet.

[0027] Figure 4 This is a structural diagram of a fuel cell unit. The numbers in the diagram are as follows: 5-1-1 is the cathode plate, 5-1-2 is the air seal, 5-1-3 is the membrane electrode, 5-1-4 is the hydrogen seal, 5-1-5 is the anode plate, 5-1-6 is the coolant seal, 5-1-7 is the connector fixing the relative positions, 10 is air, 11 is hydrogen, 6 is coolant, 5-1-8 is the air flow channel (air flows on the opposite side of the cathode plate), and 5-1-9 is the hydrogen flow channel.

[0028] Figure 5 The diagram shows the flow of coolant when the system is placed on an aircraft. The numbers in the diagram are: 5 is the fuel cell, 5-2 is the coolant outlet of the fuel cell, 5-3 is the coolant inlet of the fuel cell, 6 is the fuel cell unit, 8 is the heat pipe, 12 is the hydrogen storage tank, 13 is the coolant pump, 14 is the heat pipe valve, and 15 is the connection port. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0030] Example 1:

[0031] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, 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.

[0032] like Figure 1 and Figure 2As shown, the system consists of heat exchange components such as a fuel cell 5, heat pipes 8, coolant 6, heat-conducting fins 7, and wing skin, forming a complete closed loop for waste heat conduction and dissipation. The wing skin comprises an upper skin 1 and a lower skin 2. Each component utilizes existing internal wing supports such as wing ribs 3 and wing spars 4 to fix their relative positions, reducing the system's weight. The wing spars 4 include an upper spars 4-1 and a lower spars 4-2.

[0033] Similar to the structure of a typical PEM hydrogen fuel cell, such as Figure 3 As shown, the hydrogen fuel cell stack system for aviation applications involved in this invention is also composed of end plates 5-4 at both ends and several sets of fuel cell units 5-1 connected in series in the middle, and their relative positions are fixed by connectors 5-1-7. The end plates 5-4 primarily serve to ensure the structural stability of the stack, provide a sealing function in cooperation with adjacent stack units, and also provide connectors for fluid hydrogen, air, coolant, and current matching the battery units. Considering factors such as insulation, mechanical strength, and lightweighting, the end plates 5-4 and connectors 5-1-7 are preferably made of carbon fiber reinforced polymer (CFRP).

[0034] Figure 4 This is a schematic diagram of a fuel cell unit. High-pressure air from the compressor enters the fuel cell through the air inlet 10-1, flows through the space formed by the cathode plate 5-1-1, the airflow channel seal 5-1-2, and the membrane electrode assembly 5-1-3, and flows along the air guide channel 5-1-8. During this flow, it combines with protons passing through the membrane electrode assembly and finally exits the fuel cell through the air outlet 10-2. Because the entire fuel cell is wider at the front and narrower at the rear, a design with a wider front flow channel and a narrower rear flow channel is preferred to ensure consistent pressure drop. For the stamped cathode plate 5-1-1, flow channels appear on either the side facing or away from the air. Figure 4 The cathode plate 5-1-1 shown is the side facing away from the air, and the flow channel is narrow at the front and wide at the back.

[0035] Similar to the hydrogen flow channel 5-1-8, the air flow channel 5-1-9 is also a set of roughly parallel channels. Using completely parallel and equally wide channels would result in significantly greater resistance along the layer at the leading edge than at the trailing edge, ultimately leading to different flow rates and reduced efficiency. Therefore, a design that is wider at the front and narrower at the back, and straighter at the front and curved at the back, was adopted to ensure that the airflow and oxygen concentration per unit area of ​​the membrane electrode are similar across the front and rear channels.

[0036] The cathode plates 5-1-1 and anode plates 5-1-5 of two adjacent units are connected to each other, forming a series connection of electric propulsion units, i.e., a bipolar plate. The flow channels of the cathode plate 5-1-1 and anode plate 5-1-5 are perpendicular to each other, which helps to enhance the structural rigidity of the bipolar plate. For the purpose of weight reduction, both the cathode plate 5-1-1 and the anode plate 5-1-5 are preferably made of aluminum-magnesium alloy. Secondly, in order to increase the corrosion resistance and surface conductivity of the alloy, the surface is preferably treated with electroplating of corrosion-resistant metal, or anodizing combined with conductive filling and other surface treatment processes.

[0037] When the volume of the irregularly shaped PEM hydrogen fuel cell involved in this invention is small, the relative surface area is large, and the requirements for cost and weight are high, it can also be replaced with gas cooling, that is, using the flowing hydrogen and air for cooling, thereby eliminating the need for forced convection coolant and related components.

[0038] Figure 5 It is a compound-wing eVTOL aircraft. Considering that the shape and size of the hydrogen cylinder 11 are not easily changed, to reduce the frontal area, it is preferably placed at the rear of the fuselage, while the hydrogen fuel cell is placed at the wing root to reduce the distance between the hydrogen cylinder 11 and the fuel cell stack 5. Figure 1 As shown, coolant pump 12 pumps low-temperature coolant 6 into fuel cell 5 in the direction of the arrow. After fuel cell 5 generates electricity and produces waste heat, the waste heat is carried away by the coolant from fuel cell outlet 5-2. Fuel cell outlet 5-2 is connected to heat pipe 8 via valve 13; when valve 13 is open, the waste heat will enter heat pipe 8 along with the coolant. Figure 1 As shown, the heat pipe 8, heat-conducting fins 7, and upper skin 1 or lower skin 12 are arranged in a sequence. Heat is conducted to the wing surface and carried away by the external airflow. The coolant 6 inside the heat pipe 8 reverts to a cryogenic coolant and returns to the fuel cell via the inlet 5-3 of the fuel cell coolant through the heat pipe 8, forming a cycle. Here, the heat pipe 8 and the fuel cell coolant inlet 5-3 are connected by a connector 14.

[0039] To enhance heat conduction between the heat pipe 8, heat fins 7, and upper or lower skin 1, reinforcing ribs 7-1-1 can be fabricated at the heat pipe crossing points during the processing of the heat fins 7 using stamping, sheet metal, or other processes. This enhances both heat conduction and the rigidity of the heat fins 7, thereby reducing the thickness of the skin. Another method to enhance heat transfer is to fill the connection points between the heat pipe 8, heat fins 7, and upper or lower skin 1 with thermal grease 9 or similar materials.

[0040] Similarly, in order to enhance heat dissipation, such as Figure 1As shown, the coolant leaving the high-temperature section of fuel cell 5 can preferably be cooled by the upper wing surface, while the low-temperature coolant flowing back can preferably be cooled by the lower wing surface, because under high-altitude solar radiation, the temperature of the upper wing skin 1 will be higher than the temperature of the lower wing skin 2.

[0041] Of course, the aforementioned heat-conducting fins 7 can be designed with a uniform height as shown in Figure 2, or with a non-uniform height structure or even an intermittent structure design; such equivalent solutions obtained through simple structural deformation should all fall within the protection scope of this patent.

[0042] Currently, mainstream 4-5 seat eVTOL aircraft, such as the Airbus CityAirBus NextGen and the Peakfly V2000, generally have a takeoff weight between 2-3 tons, a wingspan between 12-20 meters, a wing area between 20-30 square meters, a maximum motor power between 500-800 kW, a cruising speed range of 200-300 km / h, and a lift-to-drag ratio roughly in the range of 8-12. When using a lithium-ion battery-hydrogen hybrid system, the instantaneous power of the lithium-ion battery is needed during takeoff and landing, while the hydrogen fuel cell is mainly relied upon during cruise. Below, we take an average figure: a takeoff weight of 2500 kg, a wing area of ​​25 square meters, and a cruising speed of... (about Based on a maximum power of 650kW, a lift-to-drag ratio of 8, and 100% power redundancy, a simple calculation yields a maximum cruising power of 160kW. Furthermore, considering the wing area, wingspan, and mean chord length... This is to demonstrate the practicality of the present invention.

[0043] Currently, the efficiency of hydrogen fuel cells is generally around 50%, which translates to a power generation of 160kW, and the corresponding heat generation is also... In addition, the solar emissivity at an altitude of 1000 meters generally does not exceed 1300 W / m². 2 Based on a 20% absorption rate for white coating, the actual absorption rate does not exceed 260W / m². 2 Meanwhile, the infrared emissivity of the same white paint can be as high as 85%. According to Boltzmann's law of radiation, when the surface temperature of the wing is 0 degrees Celsius, or 273K, Infrared radiation heat dissipation is roughly equal to solar radiation heat absorption. If the wing surface temperature rises, the blackbody radiation from the wing surface itself can help dissipate heat. Of course, in such a low-temperature environment, the heat dissipation difficulties described below will not arise.

[0044] The typical operating temperature of a PEM hydrogen fuel cell is 50-80℃. When the temperature exceeds 90℃, the moisture inside the membrane evaporates rapidly, causing the membrane to dry out and shrink, resulting in a sharp increase in proton conduction resistance and a significant decrease in battery output power. On the other hand, in most regions, ambient temperatures above 40℃ in summer are rare, and the temperature drops by approximately 6.5℃ for every 1000 meters of altitude increase. Therefore, the ambient temperature can be set at 35℃. This refers to the temperature T of the coolant when it flows out of the fuel cell (6-1). max The temperature is 80℃, while the temperature T flowing back to the fuel cell (6-7) is... min The temperature is not higher than 50°C, which corresponds to an average wing surface temperature of less than 65°C.

[0045] Using the air viscosity at an ambient temperature of 35℃, the Reynolds number was calculated as follows: The number is much greater than the critical Reynolds number, indicating turbulence. The corresponding formula for calculating the Nusselt number within this range... The Prandtl number of air at 35°C ,therefore The thermal conductivity of air and wing chord Substituting into the formula for heat transfer on a flat plate with parallel airflow, i.e., the heat transfer coefficient:

[0046] .

[0047] Since convective heat transfer occurs on both the upper and lower surfaces of the wing, and is dominated by convection, gravity-induced convection need not be considered. Excluding control surfaces such as flaps and ailerons, and parts that cannot be connected to heat pipes, and assuming an effective heat transfer area of ​​80%, corresponding to a total heat transfer area of ​​40 square meters for both the upper and lower wings, the total convective heat transfer is: The heat output is approximately 160kW. .

[0048] For most fixed-wing aircraft, the take-off / extension speed is typically around 50% of cruise speed, requiring 1.2-1.8 times the thrust at cruise speed. In other words, when the speed reaches more than 50% of cruise speed, the aerodynamic lift of the wings can overcome gravity. Again, assuming 100% power redundancy, the required power and waste heat generated... The range is between 190-290kW. Taking the aforementioned model as an example, the Reynolds number corresponding to the wheel lifting / lowering speed is... It also belongs to turbulence and can be expressed by the formula. Calculation. At this time... Using the flat plate heat transfer equation, the heat transfer coefficient during takeoff and landing is obtained. That is, the total heat transfer of the wing about It is also greater than the heat generated. .

[0049] Calculated under the above conditions, even in a high-temperature day with a ground temperature of 40°C, minimum lift-to-drag ratio, 100% redundant power, and ignoring radiative heat dissipation from the wing, the maximum convective heat dissipation from the wing during the cruise phase is calculated. Approximately the total heat production 3.8 times. The above calculations assume the wings are completely parallel and there is no angle of attack. In reality, due to airfoil shape, angle of attack, propeller interference, etc., the boundary layer will be thinned, resulting in separation and disturbance. Heat transfer can be significantly improved on this basis, demonstrating that wing-based heat dissipation is entirely feasible. However, during the wheel-raising / lowering phase of fixed-wing aircraft with lower speeds and higher thrust requirements, the heat dissipation is close to the heat generation. If necessary, lithium batteries can be used, or redundancy can be increased by optimizing the aircraft's aerodynamic characteristics, or propeller airflow can be used for heat dissipation to meet safety requirements.

[0050] Although eVTOLs generally do not have a taxiing phase before or after wheel deployment, they still face heat dissipation issues during takeoff and landing. For tiltrotor eVTOLs, the wing and ducted engine positions are relatively fixed. Although airspeeds are low during takeoff and landing, the airflow generated by the ducted engine can cool the wing. However, for hydrogen-powered tiltrotor aircraft and compound-wing eVTOLs, the airflow generated by the propeller cannot simultaneously cover the entire upper and lower wing surfaces, and lift cannot be generated by the wing. Therefore, the hydrogen fuel cell cannot operate at the cruise power level during takeoff and landing, requiring additional support from lithium batteries or other power sources. In this case, the system can also be extended for thermal management of lithium batteries.

[0051] Finally, excessively low temperatures in the hydrogen fuel cell 5 can also lead to low stack conversion efficiency. Therefore, in addition to the coolant pump 12 changing the heat transfer rate by controlling the flow rate, other methods can be used... Figure 5 As shown, multiple parallel heat pipes are set up, and the flow rate and operating conditions of each heat pipe are controlled by valve switch 13. In low temperature environment, heat loss is reduced by reducing the flow rate.

Claims

1. A thermal control structure for an integrated hydrogen fuel cell in an aircraft wing, comprising a fuel cell stack, heat pipes, coolant, heat dissipation fins, wing skin, wing ribs, and wing spars. The wing skin includes an upper skin and a lower skin, which together form the frame structure of the aircraft wing. The heat pipes include heat pipes close to the upper wing surface and heat pipes close to the lower wing surface. The structure is characterized by: The aircraft wing frame structure contains a wing box, in which the fuel cell stack is placed. The heat pipes close to the upper wing surface and the heat pipes close to the lower wing surface are connected to the upper skin and the lower skin respectively through heat dissipation fins. The fuel cell stack includes several sets of fuel cell units connected in series. Each fuel cell unit consists of a cathode plate, an air seal, a membrane electrode assembly, a hydrogen seal, and an anode plate, which are fixedly connected by connectors. The cathode plate has an air flow channel, and the anode plate has a hydrogen flow channel. One side of the fuel cell stack has an oxygen inlet, a hydrogen inlet, an oxygen outlet, and a hydrogen outlet. The front and rear sides of the fuel cell stack have fuel cell coolant outlet holes and fuel cell coolant inlet holes. The fuel cell stack is the main waste heat generating component. One end of the heat pipe is embedded in the fuel cell stack. The coolant enters the fuel cell stack through the fuel cell coolant inlet and exits the fuel cell stack through the fuel cell coolant outlet. The waste heat of the fuel cell stack is conducted to the heat dissipation fins through the heat pipe, and then exchanges heat with the external airflow through the upper and lower skins, so as to achieve active control of the operating temperature of the fuel cell stack. During takeoff and landing, the strong airflow generated by the propellers directly acts on the wing skin surface, accelerating heat dissipation through forced convection. Meanwhile, the large amount of waste heat generated by the fuel cell due to its instantaneous high power output is collected by the liquid cooling circuit and conducted to the heat-conducting fins via heat pipes, then rapidly transferred to the skin, achieving efficient cooling with the help of airflow. Once in the cruise phase, the airflow generated by the high-speed flight flows smoothly along the wing surface, continuously carrying away heat from the skin through natural convection and thermal radiation. The coolant in the heat pipes, after being cooled as described above, returns to the fuel cell stack, forming a cycle.

2. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: The fuel cell stack is a proton exchange membrane fuel cell, and the heat pipe is a metal pipe containing a coolant. Waste heat from the fuel cell is discharged through convection or phase change circulation, and the coolant is returned for cooling.

3. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: The heat dissipation fins are metal heat-conducting components, fixed to the inner side of the upper and lower skins, and improve heat conduction and heat dissipation efficiency by increasing the contact area with the heat pipes. The upper and lower skins are made of metal heat-conducting materials, and the aircraft uses airflow to force convection heat exchange and cooling of the skins during the cruise phase.

4. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: The heat dissipation fins and heat pipes are arranged in a crisscross pattern and are close to the inner side of the upper or lower skin. Where the upper or lower skin can be supported and reinforced, the skin thickness can be reduced to achieve weight reduction of the aircraft structure.

5. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: The aforementioned heat dissipation system can also be used for thermal management and temperature control of the aircraft's lithium battery system when the hydrogen fuel cell is shut down and not in operation.

6. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: The cryogenic fuel cell is adapted to the upper and lower surface contours of the wing and installed inside the wing box; the stack end plate and each fuel cell unit are non-rectangular shapes that are close to the contour near the maximum thickness of the airfoil, with an overall gradient configuration that is wider near the front wing spars and narrower near the rear wing spars.

7. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: The anode and cathode plates of the fuel cell unit are made of aluminum or magnesium alloy substrates with an anti-corrosion layer on the surface, which also serves to conduct electricity, enhance heat dissipation, and reduce structural weight.

8. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: When hydrogen or air flows in the anode and cathode plates along the front and rear direction of the aircraft, the gas flow channel adopts a layout that is wide at the front and narrow at the back, and curved at the front and straight at the back, so that the pressure drop and gas residence time are evenly distributed in the front and rear of the flow channel. When hydrogen or air flows in the anode and cathode plates along the vertical direction of the aircraft, the gas flow channel adopts a layout that is narrow at the front and wide at the back, and straight at the front and curved at the back, so that the pressure drop and gas residence time are evenly distributed before and after the flow channel.

9. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: The cryogenic fuel cell is integrated between the wing box load-bearing structure. The weight balance of the whole machine is achieved through a distributed arrangement. The internal space of the fuselage is reserved for the arrangement of hydrogen storage tank components whose shape is not easy to adjust.

10. The thermal temperature control structure for an aircraft wing-embedded hydrogen fuel cell according to claim 1, characterized in that: Thermal grease or other thermally conductive filler materials are placed between the heat pipe and the skin to further improve the thermal conductivity between them.

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