Thermal management air duct for aircraft fuel cell systems

Abstract

The present invention relates to an aircraft comprising a cooling system integrated into the fuselage and at least one propeller driven by an electric motor configured to propel the aircraft, wherein the cooling system comprises at least one cooling duct or air duct installed inside the fuselage of the aircraft and having an air inlet and an air outlet, the cooling duct designed to allow air to flow between the air inlet and the air outlet, and at least one heat exchanger disposed inside the cooling duct, the heat exchanger designed to transfer thermal energy to the air flowing through the cooling duct, wherein the air inlet is located in an excess pressure region generated by the air accelerated by the rotation of the propeller, and the air outlet is strategically located on the outer surface of the fuselage through which the airflow accelerated by the rotation of the propeller passes, thereby generating a low-pressure region that facilitates the airflow through the cooling duct, thereby enabling efficient heat dissipation through the heat exchanger.

Description

Technical Field

[0001] The present invention relates to an aircraft, particularly an aircraft propelled by an electric motor driven by a hydrogen fuel cell. The present invention is particularly applicable to electric aircraft, especially an airplane implementing the present invention.

Background Art

[0002] Current aircraft, particularly airplanes, are propelled by the energy generated by the combustion of kerosene. Commercial aviation is deeply involved in the emission of a large amount of greenhouse gases including carbon dioxide. It is essential to develop alternative solutions that emit no or only a very small amount of greenhouse gases. Electric aircraft provide a solution for reducing greenhouse gas emissions by commercial aviation. The use of a plurality of batteries is not optimal in terms of their weight. An electric propulsion solution powered by a hydrogen fuel cell provides a solution that can replace a plurality of batteries.

[0003] The thermal management of a hydrogen fuel cell is an important factor for the normal operation of the hydrogen fuel cell. One of the problems with electric propulsion by a hydrogen fuel cell lies in the cooling of the fuel cell. Certainly, the fuel cell is more efficient than an internal combustion engine, but for example, the heat generated by a PEM (Proton Exchange Membrane) type fuel cell is extremely large. 50 to 60% of the energy generated by the fuel cell is in the form of thermal energy, and thus in the form of heat to be released. Furthermore, in order to operate efficiently, an LT (Low Temperature) type fuel cell must be maintained at a low temperature in the

[0004] For these reasons, appropriately cooling the fuel cell is a decisive factor for ensuring that the fuel cell is properly used and does not shorten the life of the fuel cell.

[0005] Aircraft cooling systems are already available. A heat transfer fluid (liquid or vapor) can be provided that flows between the equipment to be cooled and a heat exchanger. The heat exchanger is installed in a cooling duct with an air inlet and an air outlet, also called a scoop. As the aircraft moves, the scoop takes in outside air, which circulates within the cooling duct and passes through the heat exchanger. The heat exchanger transfers thermal energy from the heat transfer fluid to heated air, which is then discharged through the air outlet.

[0006] These cooling systems are specifically designed to cool the electronic equipment installed in aircraft.

[0007] However, the heat exchanger must be considerably large to dissipate the thermal energy generated by the fuel cell used to drive the electric motors that propel the aircraft. In fact, the greater the amount of heat to be dissipated, the greater the airflow required to supply it. Obtaining a larger airflow generally requires a larger air inlet and correspondingly sized air duct, which negatively impacts the aerodynamic characteristics, specifically the drag and mass of the aircraft that must move.

[0008] Therefore, current solutions for dissipating large amounts of heat in aircraft, particularly from fuel cells, have significant aerodynamic drawbacks in terms of increased aircraft drag, aerodynamic characteristics, and airframe mass.

[0009] The present invention aims to solve these drawbacks at least partially. [Overview of the project]

[0010] The present invention relates to an aircraft comprising a cooling system integrated into the fuselage and at least one propeller driven by an electric motor configured to propel the aircraft, wherein the cooling system is A cooling duct (or air duct) installed inside the fuselage of an aircraft, having an air inlet and an air outlet, the cooling duct is designed to allow air to flow between the air inlet and the air outlet. A heat exchanger located within a cooling duct, the heat exchanger being designed to transfer thermal energy to the air flowing within the cooling duct, The air inlet is positioned within the excess pressure region generated by the air accelerated by the propeller's rotation, and the air outlet is strategically positioned on the outer surface of the aircraft fuselage through which the airflow accelerated by the propeller's rotation passes, thereby creating a low-pressure region that promotes the airflow through the cooling duct, and thereby enabling efficient dissipation (heat dissipation) through the heat exchanger.

[0011] The purpose of these arrangements is to ensure sufficient cooling flow while minimizing the impact of the heat exchanger on drag by reducing the resulting pressure drop. Therefore, it is crucial that the available pressure difference is greater than the pressure drop caused by the heat exchanger and the pressure drop of the cooling duct itself. The larger this pressure difference, the smaller the impact of the heat exchanger's pressure drop on drag. The heat load is then discharged in a way that minimizes its impact on the aircraft's aerodynamic characteristics.

[0012] The term "aircraft" refers to any vehicle capable of moving through the air, and is generally understood to mean airplanes, helicopters, and similar vehicles.

[0013] The term "fuselage" is understood to mean the main structure of any type of aircraft. For example, a fuselage can consist of a monocoque structure, a semi-monocoque structure, or a structure with a frame and wing spars. Fusels can take on a variety of shapes and sizes, adapted to various types of aircraft such as passenger planes, business jets, small propeller planes, military aircraft, drones, or helicopters, but are not limited to these categories.

[0014] A cooling system is understood to mean any system that removes thermal energy through a heat exchanger.

[0015] A cooling duct, or more precisely, a cooling line, is understood to mean a duct or line that allows for the flow of fresh air from the outside. The fresh air is taken in through a scoop, also called an air inlet, and discharged through an air outlet. The cooling duct can take any shape used for cooling ducts in the aerospace field, but is not limited to existing shapes. The cooling duct can be made of metal materials such as carbon, aluminum or its alloys, or any kind of composite material (e.g., carbon fiber or glass fiber-based materials), technical plastics, polymers, or technical ceramics.

[0016] The duct may have branching sections called splitters. These are partitions within the duct that separate the flow into two or more sidestreams upstream or downstream of the heat exchanger. The branching sections can be arranged vertically, horizontally, or in any other geometric configuration.

[0017] A heat exchanger is a device that transfers heat between two or more fluids of any properties at different temperatures. These fluids may be separated by solid walls to prevent mixing or direct contact. One fluid, usually at a higher temperature, transfers heat to the other, resulting in the cooling or heating of the fluid in question.

[0018] Two-phase heat exchangers (evaporators and condensers) are also an option for heat exchangers. In this type of heat exchanger, one fluid releases latent heat through a phase change (condensation or evaporation), while the other fluid is heated or cooled.

[0019] The heat exchanger can take on various shapes, dimensions, and materials.

[0020] The heat exchanger can cool a heat transfer fluid, liquid, steam, or gas using, for example, air flowing through a duct. It can also directly capture thermal energy from the device being cooled by pure heat conduction or by using any passive device employing capillary or non-capillary pumps, such as heat pipes or vapor chambers. The heat exchanger can transfer thermal energy to the air in the duct by any means, particularly by fins, pins, cones, intermittent fins, funnels, etc., and by any cross-sectional shape, such as triangular, cylindrical, or rectangular.

[0021] Transferring energy to the air is understood to mean that heat is transferred to the air through contact with the heat exchanger.

[0022] A thruster, propeller, fan, or ducted fan adapted for propelling an aircraft is understood to mean a propeller for moving the aircraft forward. This may be a thrust propeller or propulsion propeller. The propeller has blades, also called wing plates. This thruster can be operated by an electric motor.

[0023] An electric motor is understood to refer to any type of device that converts electrical energy into rotational mechanical energy. In this context, this electric motor is adapted for aircraft propulsion.

[0024] An operating thruster is understood to mean that the propeller is generating enough force to affect the aircraft's movement.

[0025] If the thruster is a propeller, the pressure region is distributed as follows: Negative pressure region in front of the propeller: When the propeller rotates, it creates a region of low pressure or negative pressure in front of it. This negative pressure draws air towards the propeller. Excess pressure region behind the propeller: When air is pushed backward by the propeller, its pressure rises. This creates a region of high or excess pressure behind the propeller. The discharge of this high-pressure air generates a thrust force that propels the aircraft forward.

[0026] When the thruster is an electric ducted fan, the pressure regions are distributed as follows: Negative pressure region at the inlet: When the air is sucked into the nacelle fairing, a region of low or negative pressure is formed at the inlet of the duct. This negative pressure draws air into the system. Excess pressure region inside the duct: When the air is accelerated by the fan blades, its pressure rises. This creates a region of high or excess pressure inside the duct. Negative pressure region behind the fan: Another negative pressure region is formed immediately behind the fan blades. This is because the acceleration of the air by the fan "pulls" the air behind the fan. Excess pressure region at the outlet: The high-pressure air inside the duct is finally discharged behind the EDF (electric ducted fan), forming another excess pressure region.

[0027] The air inlet is understood to mean any type of air inlet used in the cooling system of the aviation field, but is not limited to these types. For example, the air inlet may be composed of a plurality of openings leading to the cooling duct.

[0028] The air inlet is arranged at a location where the air pressure increases when the aircraft moves forward, such as near the fuselage of the aircraft, or on the side, bottom, top of the fuselage, and further on the main wing, wing root, base of the vertical tail, or pylon supporting the nacelle, etc.

[0029] The air inlet can be positioned in a region located downstream of the thruster, thereby directing a portion of the air accelerated by the thruster into the cooling duct, or more generally, to gain a gain from the overpressure region. This air inlet can be positioned directly in the airflow, across the overpressure region, or to divert a portion of the airflow with a dedicated device. In other words, the propeller allows air to be blown into the duct, thereby accelerating the airflow within the duct.

[0030] If the thruster is a ducted fan, the air inlet can be positioned downstream of the propeller within the nacelle.

[0031] In aeronautics, the term "air outlet" is understood to mean, but is not limited to, any type of air outlet used in a cooling system. For example, an air outlet may consist of multiple openings from the cooling duct. Furthermore, multiple air outlets may be provided, each corresponding to a branch of the cooling duct. The duct may have one or more air outlets, and therefore multiple ducts may have one common outlet.

[0032] The air outlet can be positioned in any of the following locations: the low-pressure region generated by the thruster, the upstream section (where air is drawn in), the downstream section (immediately behind the fan blades, where the fan "draws in" the air behind it following the acceleration of the air by the thruster), or the region on the fuselage or nacelle surface where a suction venturi effect occurs, where the flow velocity increases due to the action of the thruster. In other words, it allows the propeller to draw in the air contained within the duct and accelerate the flow.

[0033] Placing the air outlet in the negative pressure region of the fuselage or nacelle increases the available pressure difference.

[0034] Placing the air inlet in the excess pressure region of the fuselage or nacelle increases the available pressure difference.

[0035] Increasing the available pressure difference makes it possible to overcome, for example, potentially larger pressure drops. This pressure drop may be due to the duct geometry or a heat exchanger with a larger contact area with the air. As a result, the dissipation of thermal energy can be improved, increasing the efficiency of the cooling system.

[0036] As the amount of heat dissipated increases, the airflow required to dissipate it also increases, leading to a greater pressure drop across the heat exchanger. This situation significantly reduces the difference between the available pressure jump and the introduced pressure drop, resulting in aerodynamic drag that is detrimental to the aircraft.

[0037] The air inlet is located in a place where the air pressure is relatively higher than that of the air outlet when the aircraft is moving forward, for example, in the forward part of the aircraft.

[0038] The air outlet is located in a place where the air pressure is relatively lower than that of the air inlet when the aircraft is moving forward, for example, in the rear part of the aircraft.

[0039] The air inlet may include a movable part that moves in response to the airflow requirements for cooling the heat exchanger. For example, the air inlet may include a valve that increases or decreases the opening in accordance with the required airflow, an adjustable flap, or one or more deflection plates.

[0040] The air outlet may include a movable part that moves in response to the airflow requirements for cooling the heat exchanger. For example, the air outlet may include a valve that increases or decreases its opening in accordance with the required airflow, an adjustable flap, or one or more deflection plates.

[0041] The forward or upstream of the propeller is understood to mean forward of the plane on which the propeller operates, as it is connected to the aircraft's reference coordinate system. The forward of this plane is understood to mean the side on which the airflow passing through the propeller arrives when the propeller is operating. In the context of an airplane, the forward of the propeller means located to the side of the plane that is located on the nose side of the aircraft.

[0042] The rear or downstream of the propeller is understood to mean forward of the plane on which the propeller moves, as it is connected to the aircraft's reference coordinate system. The rear of this plane is understood to mean the side on which the airflow passing through the propeller is accelerated when the propeller is operating. In the context of an airplane, the rear of the propeller means being located laterally to the plane on the tail cone side of the aircraft.

[0043] The circle surrounding the propeller is understood to mean a circle formed by a series of small exits located on the inner wall of the aforementioned nacelle, corresponding to the tips of the blades, in a reference coordinate system fixed to the aircraft. This circle also passes through all the tips of the propeller and has the center of the propeller as its center.

[0044] To say that the air exiting the air outlet is positioned in a region in front of the propeller such that it passes at least partially through a circle surrounding the propeller, or in a plane parallel to this circle upstream of the propeller when the propeller is operating, is understood to mean that the outlet is positioned within a region where the propeller generates negative pressure when the propeller is operating. Therefore, when the propeller is operating, the airflow exiting the cooling duct enters a negative pressure region generated by the propeller, generating negative pressure at the outlet of the cooling duct. In other words, the region is defined as a region where the air pressure is lower when the propeller is operating.

[0045] In the region behind the propeller, the air entering the air inlet when the propeller is operating is positioned to pass at least partially through the circle surrounding the propeller. This is understood to mean that the inlet is positioned within a region where the propeller generates excess pressure when the propeller is operating. Therefore, when the propeller is operating, the airflow enters the cooling duct from the excess pressure region generated by the propeller, generating excess pressure at the inlet of the cooling duct. In other words, the region is defined as the region where the air pressure is higher when the propeller is operating.

[0046] An electric fan is understood to mean any form of mechanical device that is electrically powered and designed to move air.

[0047] The fan is powered by the aircraft's power generation system, which assists in cooling. This means that a portion of the electrical energy generated by the system is used to operate the fan. However, this energy consumption is compensated for by increased efficiency of the cooling system, which allows for the maintenance of a safe and effective operating temperature for the entire aircraft's propulsion system.

[0048] A fan in a duct is understood to mean a mechanical device integrated inside the cooling duct. This fan may consist of a propeller or multiple fins and is specifically designed to accelerate the movement of air passing through the duct. Its primary role is to facilitate heat exchange by increasing the airflow through the heat exchanger, thereby optimizing the efficiency of the cooling system.

[0049] The fan can be positioned at various points along the duct. For example, it can be positioned upstream of the heat exchanger, i.e., before the heat exchanger in the direction of the airflow. This pushes the air through the heat exchanger, thereby increasing the amount of thermal energy that can be transferred from the heat exchanger to the air.

[0050] Alternatively, the fan may be positioned downstream of the heat exchanger or behind the heat exchanger in the direction of the airflow. In this case, the fan draws air through the heat exchanger and may be particularly useful in maintaining the airflow when the air pressure at the outlet of the duct is low.

[0051] If the system comprises multiple heat exchangers, one or more fans may be installed between these heat exchangers. This configuration optimizes the pressure jump through each heat exchanger and improves the overall efficiency of the cooling system. This type of fan configuration is defined as “series”.

[0052] Multiple smaller fans may be installed adjacent to each other to better ensure that the appropriate airflow described above passes through the heat exchanger. This type of fan configuration is defined as “parallel”.

[0053] The fan may include movable parts that function as necessary for the airflow required to cool the heat exchanger. For example, the rotational speed of the fan can be adjusted according to the required airflow, or the fan blades can be oriented to optimize the fan's performance as needed. A combination of these two methods is also possible.

[0054] Regarding placement, the fan can be mounted axially, i.e., aligned with the airflow through the duct, or radially, i.e., perpendicular to the airflow. Each of these configurations offers specific advantages. For example, axial mounting (axial inlet, axial outlet) results in a larger airflow and a more uniform distribution of the airflow, promoting uniform heat exchange throughout the heat exchanger. This type of fan is used to facilitate the flow in relation to the pressure jump when the supplied airflow is high and the pressure jump is small. Conversely, if the supplied pressure jump is larger than the required airflow, radial mounting (axial inlet, radial outlet) is useful.

[0055] The dimensions and shape of the fan can also be varied according to the specific characteristics of the cooling duct and the heat exchanger. For example, in a small-diameter duct, a fan with short, angled blades may be preferred to maximize the airflow. Conversely, in a wider duct, a fan with long, straight blades may be used to generate a stronger airflow.

[0056] Finally, the fan may be equipped with adjustment and control devices that allow its operation to be adjusted in real time according to the flight conditions, the performance capabilities of the electric thrusters, and the cooling requirements. These devices may include temperature and pressure sensors, rotational speed control devices, and blade control systems. This technological sophistication helps optimize the performance of the cooling system while minimizing its impact on the aircraft's energy efficiency and aerodynamic characteristics.

[0057] According to one embodiment, the cooling system is used to cool a fuel cell.

[0058] Low-temperature (LT) fuel cells generate a large amount of heat and need to be maintained at a controlled temperature. Therefore, such cooling systems are more suitable for cooling hydrogen fuel cells.

[0059] According to one embodiment, the cooling duct is located in the fuselage of the aircraft.

[0060] This improves the aerodynamic characteristics of the aircraft.

[0061] According to one embodiment, the aircraft further comprises a fairing (nacelle) on which the propeller and the air outlet are arranged.

[0062] The nacelle fairing for the electric ducted fan improves the efficiency of the propeller and ensures that the air outlet is positioned within the negative pressure region in an overall and stable manner. In fact, the nacelle fairing ensures the stability of the negative pressure region located in front of the propeller, and by providing the air outlet within the nacelle fairing in front of the propeller, it is ensured that the air outlet is always positioned within the negative pressure region.

[0063] The nacelle of a ducted fan refers to the part that surrounds the propeller and improves its efficiency. The fairing is a component of the nacelle (also called the "duct"). The propeller is mounted on the nacelle, and the propeller's motor is located inside the nacelle. The air outlet is located on the inner wall of the fairing.

[0064] According to one embodiment, the air outlet has a plurality of openings distributed over the entire inner circumference of the nacelle.

[0065] According to one embodiment, the air outlet can also be positioned behind the nacelle, within a negative pressure region generated by the acceleration of the air. This configuration minimizes the impact on the aircraft's drag while utilizing this negative pressure to promote the discharge of hot air from the cooling system.

[0066] This prevents periodic imbalances in the mechanical load on the propeller and avoids areas where excessive force is applied to the propeller. Such distortions reduce the efficiency of the motor.

[0067] The openings distributed across the entire inner circumference of the nacelle mean that the openings are arranged substantially symmetrically with respect to the center of the propeller, i.e., according to axial symmetry with respect to the central axis of the propeller. For example, these openings may be arranged substantially continuously along the inner circumference of the fairing. Not all openings have the same diameter, depending on the balance of airflow at each opening.

[0068] According to one embodiment, the cooling duct is provided with a second air outlet, the aircraft further comprises a second propeller located within a second fairing, and the second air outlet is located in front of the second propeller within the second fairing.

[0069] Therefore, two air outlets are provided to discharge the air entering the cooling duct. Both of these air outlets are located in the negative pressure regions generated by the propeller and the second propeller, respectively. Consequently, the air contained in the duct is drawn in by the two propellers, which further accelerates the airflow within the cooling duct.

[0070] According to one embodiment, the reaction products from the fuel cell are injected under pressure into the cooling duct upstream of the heat exchanger and toward the air outlet.

[0071] This accelerates the expulsion of air contained within the duct and improves the efficiency of heat energy discharged by the heat exchanger.

[0072] Reaction products refer to the elements produced by oxidation reactions when a fuel cell generates electricity. In the case of hydrogen combustion batteries, the main product of the power generation reaction is water vapor.

[0073] According to one embodiment, an adjustable flap system can be provided at the air inlet to adjust the amount of incoming air in response to cooling requirements. By opening and closing these flaps, the airflow into the cooling duct can be controlled, optimizing the cooling efficiency and the resulting air drag according to flight conditions and the system's thermal load.

[0074] In yet another embodiment, the air inlet may include an internal duct system configured to optimally direct the air toward the heat exchanger. These ducts may be designed to minimize pressure drop and maximize heat exchange efficiency.

[0075] According to one embodiment, the air inlet may be configured to collect air not only from the front but also from the sides using an auxiliary duct. This configuration allows for greater flexibility in the placement of the air inlet on the aircraft while increasing the airflow available for cooling.

[0076] According to one embodiment, an adjustable flap system can be provided at the air outlet to adjust the amount of incoming air in response to cooling requirements. These flaps allow control of the airflow exiting the cooling duct, thereby optimizing cooling efficiency and aerodynamic drag according to flight conditions and the system's thermal load.

[0077] According to one embodiment, the air outlet may comprise a plurality of strategically placed openings along the airframe to optimize air distribution and minimize turbulence in the airflow around the aircraft.

[0078] According to one embodiment, the air outlet may be designed to direct the outgoing air in a manner that minimizes its impact on the aircraft's aerodynamic characteristics. For example, the air may be directed to optimally mix with the airflow around the aircraft, thereby minimizing drag.

[0079] In one embodiment, the air outlet may be designed to direct the airflow to assist the aircraft's propulsion. While this effect may be minimal, it could still contribute to the aircraft's overall efficiency.

[0080] In one embodiment, the fan in the duct is associated with an electric or mechanical transmission. This transmission allows for precise adjustment of the fan's rotational speed in response to cooling requirements, thereby minimizing power consumption while providing adequate cooling of the system.

[0081] According to one embodiment, the fan in the duct may be equipped with variable-pitch blades. This makes it possible to mechanically adjust the blade angle according to flight conditions and cooling requirements. Therefore, this fan can provide optimal airflow regardless of flight conditions.

[0082] According to one embodiment, the fan in the duct may be configured to operate in a reversible mode. In other words, it is possible to reverse the direction of its airflow, which is useful for rapidly dissipating heat accumulated in the duct during overheating events or for reducing energy consumption under low heat load conditions.

[0083] According to one embodiment, multiple fans can be arranged along a cooling duct. This series or parallel configuration allows for more precise control of the airflow through the heat exchanger and enables a more uniform temperature distribution within the duct.

[0084] According to one embodiment, a fan in a duct may be designed to operate in conjunction with a heat recovery system. By recovering some of the heat released by the electrical system, the overall energy efficiency of the aircraft can be improved by reusing the heat for purposes such as humidifying the cabin or defrosting the wings.

[0085] According to one embodiment, the air outlet is located in a low-pressure region generated by the propeller, while the air inlet is located in a region of high natural pressure within the aircraft body, without being directly affected by the propeller.

[0086] According to one embodiment, the air outlet is located in the natural low-pressure region of the aircraft fuselage, which is not directly affected by the propeller, while the air inlet is positioned in the excess-pressure region generated by the propeller.

[0087] According to one embodiment, there is no fan inside the cooling duct.

[0088] According to one embodiment, the air inlet is equipped with an air filter to prevent foreign matter from entering. [Brief explanation of the drawing]

[0089] [Figure 1] Figure 1 is an explanatory diagram showing an aircraft according to a prior art embodiment. [Figure 2] This figure shows a cooling system according to an embodiment of the present invention. [Figure 3] This diagram shows the operation of the cooling system according to an embodiment of the present invention. [Figure 4] A three-dimensional diagram of a cooling duct according to an embodiment of the present invention is shown. [Figure 5] This figure shows multiple types of air outlets within a nacelle according to embodiments of the present invention. [Figure 6] This figure shows multiple types of ducts according to embodiments of the present invention. [Figure 7] This figure shows the configuration of a cooling duct and its internal elements, taking into account an upstream fan of a heat exchanger according to an embodiment of the present invention. [Figure 8] This figure shows the configuration of a cooling duct and its internal components, taking into account multiple fans installed in parallel according to an embodiment of the present invention. [Modes for carrying out the invention]

[0090] Figure 1 shows airplane 1.

[0091] The aircraft comprises a fuselage 2 and wings 3. The aircraft is propelled by an electric motor 4, which is operated via a cable 11 using electricity generated by a hydrogen fuel cell 5, which is powered by hydrogen stored in a tank 6.

[0092] The fuel cell 6 is cooled by a cooling system comprising a fuel cell cooling circuit 7, a cooling unit (heat exchanger) 8, and two pipes 9 and 10 for transporting heat conduction fluid between the cooling unit 8 and the fuel cell cooling circuit 7. Thus, the first pipe 9 allows the heat conduction fluid to be transported from the fuel cell cooling circuit 7 to the cooling unit 8. On the other hand, the second pipe 10 allows the heat conduction fluid to be transported from the cooling unit 8 to the fuel cell cooling circuit 7.

[0093] The fuel cell cooling circuit 7 is not specifically described. However, any fuel cell cooling circuit can be used. For example, the equipment can be constructed so that a heat conduction fluid flows within the bipolar plate of the fuel cell. Contact between the heat conduction fluid and the fuel cell transfers the thermal energy generated in the fuel cell of the hydrogen fuel cell 5.

[0094] The cooling unit 8 comprises a heat exchanger and a cooling duct. These elements are explained in more detail in the following diagram.

[0095] Figure 2 shows a cooling system according to an embodiment of the present invention.

[0096] The cooling unit 8 includes a gas-liquid heat exchanger 12 located within a cooling duct 13. The cooling duct 13 has an air inlet 14 and an air outlet 15.

[0097] The air inlet 14 is positioned to allow outside air into the duct 13. Therefore, when the aircraft is moving forward, the air inlet 14 is located in high-pressure areas, such as in the vicinity of the nose of the aircraft or on one side of the fuselage, the lower upper or upper upper, or even on the wings, or on the pylons supporting the nacelles. In the embodiments shown in Figures 1 and 2, the air inlet 14 is located on the upper fuselage at the base of the fins and in the excess pressure region generated by the propeller 16.

[0098] The air inlet 14 is located in the excess pressure region created by the propeller 16.

[0099] The air outlet 15 is positioned to expel the air present in the duct 13. Therefore, the air outlet 15 is positioned in a location where the pressure is low when the aircraft is moving forward, particularly in a location where the pressure is significantly lower than that of the air inlet 14. For example, the air outlet 15 can be located at the rear of the aircraft. In the embodiments shown in Figures 1 and 2, the air outlet 15 is positioned in the airflow generated by the propeller 16 to obtain the effect of a Venturi-type suction effect. More specifically, the air outlet 15 is positioned on the surface of the fuselage that is in contact with the airflow generated by the propeller 16.

[0100] Figure 5 further illustrates the position of the air outlet 15 when it is located near the nacelle 20. The nacelle 20 is an embodiment of the present invention, but is not essential.

[0101] Therefore, cold outside air enters through the air inlet 14, passes through the upstream section 17 of the duct 13, and then passes through the heat exchanger 12. The cold air in contact with the heat exchanger 12 stores thermal energy; that is, the air warms up. The hot air then passes through the downstream section 18 of the duct 13 to finally be discharged from the air outlet 15. The operating propeller 16 creates excess pressure at the air inlet 14, so that air enters the duct 13 more quickly, thereby accelerating the airflow within the duct 13. The operating propeller 16 also creates negative pressure around the air outlet 15. Therefore, the air exiting the air outlet 15 is drawn in by the air accelerated by the propeller 16, so that the air is discharged more quickly outside the duct 13, thereby accelerating the airflow within the duct 13.

[0102] The reaction products derived from the fuel cell can be injected under pressure into the downstream section 18 of the duct 13. The products are then transferred by pipe 5 to an injection device 19 located in the downstream section 18 of the duct 13. The combustion products are injected in the direction of airflow within the cooling duct 13, i.e., from the air inlet 14 to the air outlet 15.

[0103] The cooling systems shown in Figures 1 and 2 are based on a heat transfer fluid that does not undergo phase change. The cooling system can also rely on a phase-change fluid, in which case the cooling system includes an evaporator located near the fuel cell to transfer thermal energy from the fuel cell to the heat transfer fluid. The fluid in vapor state then passes through a condenser installed in duct 13 instead of a gas-liquid heat exchanger 12. The cooling system may also include an expansion valve to expand the fluid, or a turbine to extract mechanical power, or a pump to enable the flow of the heat transfer fluid. The expanded gas then proceeds back to the evaporator.

[0104] Figure 3 shows a diagram corresponding to the cooling system.

[0105] In step S21, the heat transfer fluid passes through the fuel cell cooling circuit 7. The temperature of the liquid rises, and the liquid thus stores the thermal energy generated by the cells of the fuel cell 5.

[0106] In step S22, the high-temperature heat transfer fluid is transported via pipe 9 to the heat exchanger 12 included in the cooling unit 8.

[0107] In step S23, the high-temperature heat transfer fluid is cooled in the heat exchanger 12 by the effect of the air flowing through the duct.

[0108] In step S24, the low-temperature heat transfer fluid is transported to the fuel cell cooling circuit 7 via pipe 10.

[0109] Then, steps S21 through S24 are repeated in a loop.

[0110] Figure 4 shows a three-dimensional view of an embodiment of the cooling unit 8.

[0111] Figure 2 shows a duct 13 with the same components as those shown in Figure 2, namely an air inlet 14 and an air outlet 15. The heat exchanger 12 is located inside the duct 13. The air outlet 15 is formed by the inner surface of the nacelle 20 located upstream of the propeller 16.

[0112] The airflow passing through the cooling duct 13 is indicated by the white line. The airflow enters the duct 13 via the air inlet 14 and then passes through the upstream section 17 of the duct 13. Next, the airflow passes through the heat exchanger 12, where it releases the heat from the heat exchanger as thermal energy. After that, the hot airflow passes through the downstream section 18 of the duct 13 and exits through the air outlet 15, which opens into the nacelle 20 in front of the propeller.

[0113] Figure 5 shows multiple types of air outlets within the nacelle 20 according to the present invention.

[0114] Figure 5 shows, more specifically, the air outlet 15 on the inner surface of the nacelle 20, which can have multiple shapes and dimensions, as well as multiple openings. The explanation of the figures described above also applies in this case.

[0115] In these three figures, the nacelle 20, more specifically the fairing of the nacelle 20, surrounds the propeller 16. The region located in front of the propeller 16 within the nacelle 20 represents a negative pressure region when the propeller 16 is operating. In the three examples, the openings 21, 22.1, 22.2, and 23 of each air outlet 15 (15, 15.1, 15.2, 15.3) are located within this negative pressure region.

[0116] In the left-hand diagram of the nacelle in Figure 5, the air outlet 15 takes the form of a single opening 21 on the inner surface of the nacelle 20. While this design is simpler, it has the disadvantage of causing the propeller 16 to operate in an asymmetrical manner and thus applying stress to the propeller's axis of rotation.

[0117] In the illustration of the nacelle in the center of Figure 5, the air outlet 15 takes the form of two openings 22.1 and 22.2 positioned symmetrically with respect to the axis of the propeller 16. This has the advantage of balancing the pressure experienced by the propeller 16 and therefore reducing the stress on the propeller's axis of rotation compared to the left-hand case. However, although the pressure is balanced with respect to the axis of rotation of the propeller 16, the propeller 16 experiences fluctuating pressure at positions equidistant from the center of the propeller 16. This causes load strain on the propeller 16.

[0118] In the depiction of the nacelle on the right side of Figure 5, the air outlet 15 takes the form of a ring 23 located on the inner wall of the nacelle 20. This reduces the strain on the load applied to the propeller 16.

[0119] The present invention is not limited to these three types of air outlets 15.

[0120] Figure 6 shows two types of ducts with different shapes from the duct shown in Figure 2.

[0121] The duct shown in Figure 6 has one air inlet 14 as described above. This air inlet 14 can take any shape. The air inlet 14 is connected to the upstream part of the duct 17. However, the duct has two air outlets 15.1 and 15.2 formed by two overlapping branches of the duct.

[0122] More specifically, a single heat exchanger 12 is provided in the duct shown on the left side of Figure 6. The air exiting the heat exchanger 12 is distributed to two downstream sections 18.1 and 18.2 of the duct. Each of these branches has its own air outlets 15.1 and 15.2.

[0123] In the duct shown on the right side of Figure 6, two independent heat exchangers 12.1 and 12.2 are provided, with one heat exchanger in each downstream section 18.1 or 18.2 of the duct. At the outlet of heat exchanger 12.1, air moves into the downstream section 18.1. At the outlet of heat exchanger 12.2, air moves into the downstream section 18.2.

[0124] If the duct has two air outlets 12.1 and 12.2, then, as shown in Figure 6, in the case of an aircraft with two or more motors, each outlet can be located in a different nacelle.

[0125] Figure 7 shows a diagram corresponding to the configuration of the cooling duct for supplying a heat exchanger equipped with a fan.

[0126] In step S25, fresh air enters the cooling duct from the outside through the air inlet.

[0127] In step S26, the fresh air flows into the air duct.

[0128] In step S27, the fan pushes the air into the heat exchanger.

[0129] In step S28, the air passes through the heat exchanger and is heated by exchanging heat with the heat transfer fluid.

[0130] In step S29, the hot air flows through the cooling duct toward the air outlet.

[0131] In step S30, the air is discharged outside the aircraft through the air outlet.

[0132] Steps S25 through S30 occur via an open path.

[0133] Figure 8 shows a diagram corresponding to the configuration of the cooling duct used to supply heat to the heat exchanger using two fans installed in parallel.

[0134] In step S31, the air drawn in by the fans S33 and S34 enters the cooling duct through the air inlet.

[0135] In step S32, the air passes through the cooling duct.

[0136] In steps S33 and S34, the air is pushed by the fan.

[0137] In step S35, the air passes through the heat exchanger and is heated by heat exchange with the heat transfer fluid.

[0138] In step S36, the hot air flows through the cooling duct toward the outlet.

[0139] In step S337, the air is discharged outside the aircraft through the air outlet.

[0140] Steps S231 to S37 occur via an open path.

Claims

1. An aircraft comprising a cooling system integrated into the fuselage and at least one propeller driven by an electric motor configured to propel the aircraft, wherein the cooling system is A cooling duct or air duct installed inside the fuselage of the aircraft, having an air inlet and an air outlet, the cooling duct being designed to allow air to flow between the air inlet and the air outlet, The cooling duct comprises at least one heat exchanger located inside the cooling duct, the heat exchanger being designed to transfer thermal energy to the air flowing within the cooling duct, An aircraft in which the air inlet is located within an excess pressure region generated by the air accelerated by the rotation of the propeller, and the air outlet is strategically located on the outer surface of the fuselage through which the airflow accelerated by the rotation of the propeller passes, thereby creating a low-pressure region that facilitates the airflow through the cooling duct, thereby enabling efficient heat dissipation through the heat exchanger.

2. The aircraft according to claim 1, wherein the cooling system is used to cool a fuel cell system.

3. The aircraft according to claim 1 or 2, wherein at least one fan is installed inside the cooling duct to facilitate the airflow.

4. The aircraft according to any one of claims 1 to 3, wherein the cooling system comprises a plurality of heat exchangers arranged at different positions on the cooling duct.

5. The aircraft according to any one of claims 1 to 4, wherein the air outlet is located in the natural low-pressure region of the fuselage of the aircraft during flight and is not directly affected by the propeller.

6. The aircraft according to any one of claims 1 to 5, wherein the air inlet is not directly affected by the propeller and is located in the natural high-pressure region of the fuselage of the aircraft.

7. The aircraft according to any one of claims 1 to 6, further comprising a nacelle fairing on which the propeller and the air inlet are arranged, wherein the air inlet is located within the nacelle fairing in an excess pressure region generated by the propeller.

8. The aircraft according to claim 1, wherein at least one of the cooling ducts has a plurality of air inlets or a plurality of air outlets.

9. The aircraft according to any one of claims 1 to 8, wherein the air inlet and the air outlet are controlled to control the flow of air within the duct.

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