Propulsion device for hybrid aircraft

Abstract

A purpose of the present invention is to provide a compact and lightweight propulsion device for a hybrid aircraft.　This propulsion device for a hybrid aircraft is characterized by comprising an engine and a motor that output rotational force, a gearbox that transmits the rotational force, a power converter that converts power supplied to the motor, and a fuel flow path that supplies fuel to the engine, the propulsion device comprising a first refrigerant flow path that supplies refrigerant to the motor and the gearbox, a second refrigerant flow path that supplies refrigerant to the power converter, and a heat exchanger that causes heat to be exchanged between the fuel flow path and the first refrigerant flow path and also between the fuel flow path and the second refrigerant flow path.

Description

Hybrid aircraft propulsion system

[0001] The present invention relates to a hybrid aircraft propulsion system.

[0002] Hybrid propulsion technology has been developed that combines an electric motor with an aircraft propulsion device that uses an engine to rotate a propeller or fan, and uses this to assist thrust and generate electricity. For example, an aircraft generally has a fuselage, wings, and a propulsion system that provides thrust. The propulsion system is mounted on a nacelle, for example, suspended from the wing. There are several types of propulsion systems depending on the size of the aircraft, but turboprop engines are often used for small passenger aircraft that can accommodate several dozen people.

[0003] In aircraft with turboprop engines as their propulsion system, the turbine output shaft must maintain high rotational speeds to maintain engine efficiency, while the propeller shaft rotation speed must be limited so that the blade tips do not exceed the speed of sound. To optimize the rotational speeds of the turbine and propeller, many turboprop engines use a reduction gear between the turbine output shaft and the propeller shaft.

[0004] Furthermore, from the viewpoint of reducing fuel consumption of aircraft engines and reducing CO2 emissions, there is an increasing demand for hybridization in which engine output is assisted by an electric motor.

[0005] When hybridizing an aircraft engine, a motor and an inverter that drives it are newly added to the propulsion device. Each has a set operating temperature range, and to obtain the required performance and maintain reliability, the heat generated during operation must be cooled. Patent Document 1 discloses a conventional, non-hybrid configuration in which heat is exchanged between oil and aircraft fuel. Patent Document 2 discloses a configuration in which the respective coolants are cooled by a radiator in a propulsion system that uses a motor and inverter, such as a non-hybrid e-VTOL.

[0006] JP 2015-94584 A JP 2023-92951 A

[0007] However, aircraft propulsion systems must be installed in the limited space inside the nacelle, and the weight of the aircraft has a significant impact on the required power output and range, so a small, lightweight hybrid propulsion system is required.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a small, lightweight hybrid aircraft propulsion system.

[0009] The propulsion device for a hybrid aircraft of the present invention is a hybrid aircraft propulsion device comprising an engine and motor that output rotational force, a gearbox that transmits the rotational force, a power converter that converts the electricity supplied to the motor, and a fuel flow path that supplies fuel to the engine, and is characterized in that it comprises a first refrigerant flow path that supplies refrigerant to the motor and the gearbox, a second refrigerant flow path that supplies refrigerant to the power converter, and a heat exchanger in each of the first refrigerant flow path and the second refrigerant flow path that exchanges heat with the fuel flow path.

[0010] According to the present invention, it is possible to provide a small and lightweight hybrid aircraft propulsion device. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0011] FIG. 1 is a schematic top view of an aircraft equipped with a propulsion device. FIG. 2 is a schematic view showing the appearance of the propulsion device when stored in a nacelle. FIG. 3 is a schematic view showing the mechanical and electrical connection states of the propulsion device. FIG. 4 is a schematic view showing the arrangement of piping for gear oil, inverter refrigerant, and fuel in a propulsion device according to a first embodiment. FIG. 5 is a schematic view showing a heat exchanger and a valve state in its operating state. FIG. 6 is a schematic view showing a heat exchanger and a valve state in its bypass state. FIG. 7 is a schematic view showing the cooling system configuration of a propulsion device according to a second embodiment.

[0012] An embodiment of a hybrid propulsion system for an aircraft according to the present invention will be described below with reference to the drawings. In the drawings used in this specification, identical or similar reference numerals are used to designate identical or corresponding components, and repeated description of these components may be omitted.

[0013] 1 is a schematic top view of an aircraft equipped with a propulsion system. The aircraft 1 has a propulsion system 11 using propellers below the wings. The propulsion system 11 is a hybrid propulsion system that combines power from an engine 30 and power from a motor 50.

[0014] 2 is a schematic diagram showing the appearance of the propulsion device stored in the nacelle 12. The propulsion device has a propeller 20 and an air intake 13.

[0015] 3 is a schematic diagram showing the mechanical and electrical connections of the propulsion device. The propulsion device 11 includes a propeller 20, an engine 30 (ENG), a gearbox 40 (GB), a motor 50 (MOT), an inverter 60 (INV), and a battery 70 (BAT). The engine 30 is configured as a gas turbine engine, and the rotational force generated by the engine 30 and the motor 50, which is an electric motor, is mechanically connected to the rotating shaft of the propeller 20 via the gearbox 40. The inverter 60, which is a power converter that converts the power supplied to the motor 50, is electrically connected to the motor 50 and the battery 70. The inverter 60 converts the power supplied from the battery 70 and supplies it to the motor 50.

[0016] Next, the propulsion device 11 of the first embodiment will be described with reference to FIGS. 4 to 6. FIG.

[0017] 4 is a schematic diagram showing the arrangement of the piping for gear oil, inverter refrigerant, and fuel in the propulsion device according to the first embodiment. That is, it is a schematic diagram showing the cooling system configuration of the propulsion device. Note that, in FIG. 4, several components are omitted for the sake of simplicity.

[0018] The cooling system of the propulsion device 11 shown in Figure 4 is configured as a piping system through which three types of fluid flow: a fuel piping 101 which is a fuel flow path, a gear oil piping 111 which is a first refrigerant flow path that supplies refrigerant to the motor 50 and the gear box 40, and an inverter refrigerant piping 121 which is a second refrigerant flow path that supplies refrigerant to the power converter (inverter 60).

[0019] Of these, the gear oil piping 111 system is equipped with a gear oil pump 112, a gear oil tank 113, a gear box 40, a motor 50, etc., and the gear oil flowing through the gear oil piping 111 is used to lubricate and cool the gears in the gear box 40, cool the motor 50, and lubricate and cool other parts such as bearings. The first heat exchanger 91 exchanges heat with the fuel in the fuel piping 101 to lower the increased temperature. Other gear oil cooling mechanisms are not described here.

[0020] Here, the gear oil pipe 111, which is the first refrigerant flow path, is a circulation system, and the arrangement of the devices in the system is referred to as upstream and downstream in the refrigerant flow direction, with the gear oil pump 112 as the reference. That is, in the first refrigerant flow path, the gear oil pump 112, motor 50, gear box 40, first heat exchanger 91, and gear oil tank 113 are arranged in this order from upstream to downstream. In the first refrigerant flow path, the motor 50 is arranged upstream of the gear box 40, so that the motor 50 can be cooled first, improving the cooling effect of the motor 50. In addition, the gear box 40 is arranged between the motor 50 and the first heat exchanger 91.

[0021] An inverter refrigerant pump 122, the inverter 60, and the like are connected to an inverter refrigerant pipe 121, which is a second refrigerant flow path, and the inverter refrigerant flowing through the inverter refrigerant pipe 121 is used to cool the inverter 60, and the increased temperature is reduced by exchanging heat with the fuel in the fuel pipe 101 through a second heat exchanger 92 and a third heat exchanger 93. Other cooling mechanisms for the inverter refrigerant are not described here.

[0022] Here, the inverter refrigerant piping 121, which is the second refrigerant flow path, is a circulation system, and the arrangement of the devices in the system is referred to as upstream and downstream in the refrigerant flow direction, with the inverter refrigerant pump 122 as the reference. That is, in the second refrigerant flow path, the inverter refrigerant pump 122, the third heat exchanger 93, the inverter 60, and the second heat exchanger 92 are arranged in this order from upstream to downstream. In the second refrigerant flow path, the third heat exchanger 93 is arranged upstream of the inverter 60, and the second heat exchanger 92 is arranged downstream of the inverter 60. The refrigerant from the third heat exchanger 93 cools the inverter 60, thereby lowering the temperature increased in the second heat exchanger 92. In addition, the inverter 60 is arranged between the second heat exchanger 92 and the third heat exchanger 93 in the second refrigerant flow path.

[0023] The fuel pipe 101, which is a fuel flow path, is used to send fuel from a fuel tank 103 to the engine 30. Arranged in this order from the upstream side are a fuel pump 102, a second heat exchanger 92, a first heat exchanger 91, and a third heat exchanger 93. That is, in the fuel flow path, the second heat exchanger 92 is arranged upstream of the first heat exchanger 91, and the third heat exchanger 93 is arranged downstream of the first heat exchanger 91.

[0024] The gear oil pipe 111 is connected by a first heat exchanger 91, and the inverter refrigerant pipe 121 is connected by a second heat exchanger 92 and a third heat exchanger 93. Each heat exchanger is used to cool the gear oil and inverter refrigerant, and to preheat the fuel. The fuel tank 103 is often mounted on the wing of an aircraft, and is at a relatively low temperature in the air at high altitudes where the outside air temperature is low. This is used to cool the gear oil in conventional propulsion systems. In this embodiment, the gear oil is used to cool the motor 50, and heat exchange with the fuel can be used to cool the refrigerant for the inverter 60.

[0025] The above-described configuration realizes cooling of the motor 50 and inverter 60, which are major components added to the hybrid propulsion device from a conventional engine-based propulsion device.

[0026] The first heat exchanger 91, the second heat exchanger 92, and the third heat exchanger 93 are electrically connected to the control device 80, and the operation of each heat exchanger is controlled by commands from the control device 80 (CONT).

[0027] Fig. 5 is a schematic diagram showing a heat exchanger and the valve state in its operating state. Fig. 6 is a schematic diagram showing a heat exchanger and the valve state in its bypass state. The heat exchanger 200 is configured so that heat exchange occurs between a pipe 201 for a first fluid and a pipe 202 for a second fluid. A bypass pipe 203 for the second fluid is connected to the pipe 202 for the second fluid, and the flow path can be switched by opening and closing a first valve 211, a second valve 212, and a third valve 213.

[0028] As shown in FIG. 5, heat is exchanged between the two fluids by opening the first valve 211 and the third valve 213 and closing the second valve 212 .

[0029] Also, as shown in FIG. 6 , when the first valve 211 and the third valve 213 are closed and the second valve 212 is open, the second fluid flows through the bypass pipe 203, and heat exchange between the two fluids does not occur.

[0030] The control device 80 references the temperature of each fluid using a temperature sensor or the like (not shown) and controls the valve operation of the first heat exchanger 91, the second heat exchanger 92, and the third heat exchanger 93. In other words, each heat exchanger has a switchable heat exchange flow path and a bypass flow path, and the control device 80 controls the switching between the heat exchange flow path and the bypass flow path based on one or more temperatures of the refrigerant in the first refrigerant flow path, the refrigerant in the second refrigerant flow path, and the fuel in the fuel flow path.

[0031] For example, if the temperature of the gear oil in the gear oil pipe 111 is lower than a certain threshold value, the load on the gear oil pump 112 can be kept low by controlling the first heat exchanger 91 to be bypassed.

[0032] Antifreeze liquids such as ethylene glycol aqueous solution are often used as inverter coolants, but in high-altitude environments, the drop in outside temperature can cause the liquid to freeze or its viscosity to increase, potentially resulting in a decrease in cooling capacity.

[0033] In addition, motors and inverters may temporarily stop working depending on the flight conditions, and the coolant temperature drops in the air, which can cause freezing. On the other hand, the engine and gearbox are operating for most of the flight, so the gear oil temperature remains above a certain level.

[0034] When the refrigerant temperature in the inverter refrigerant pipe 121 is low and there is a risk of freezing, the second heat exchanger 92 is bypassed and the first heat exchanger 91 and the third heat exchanger 93 are operated, thereby making it possible to warm the inverter refrigerant by exchanging heat with the fuel downstream of the first heat exchanger 91, where the fuel is at a relatively high temperature. This is expected to have the effect of preventing the inverter refrigerant from freezing.

[0035] According to this embodiment, a small and lightweight hybrid aircraft propulsion system can be provided. In addition, the hybridization can be achieved without increasing the size of the aircraft propulsion system, thereby reducing energy consumption and CO2 emissions.

[0036] Next, a propulsion device according to a second embodiment will be described with reference to Fig. 7. Fig. 7 is a schematic diagram showing the cooling system configuration of the propulsion device according to the second embodiment. The diagram shows the connections and arrangement of the pipes for gear oil, inverter refrigerant, and fuel. In Fig. 7, several components are omitted for simplicity of explanation.

[0037] Compared to Figure 4, the cooling system for the propulsion device of this embodiment does not have the third heat exchanger 93 between the fuel pipe 101 and the inverter refrigerant pipe 121, and a fourth heat exchanger 94 is added between the gear oil pipe 111 and the inverter refrigerant pipe 121, but the rest of the configuration is the same as the cooling system for the propulsion device of Figure 4 of Example 1.

[0038] The cooling system for the propulsion device of this embodiment is configured with an emphasis on preventing the inverter coolant from freezing. Similar to the first embodiment, the temperatures of the gear oil and inverter coolant are lowered using fuel during normal operation, but when the inverter coolant becomes cold, the fourth heat exchanger 94 exchanges heat with the gear oil to raise the temperature of the inverter coolant and prevent it from freezing.

[0039] Compared to the configuration of the first embodiment, the temperature of the inverter refrigerant can be increased more efficiently by exchanging heat between the gear oil, which is expected to be hotter than the fuel, and the inverter refrigerant. When the temperature of the inverter refrigerant exceeds a certain threshold, the control device 80 controls the valve of the fourth heat exchanger 94 to bypass it, thereby preventing unnecessary temperature increases in the inverter refrigerant. Note that multiple fourth heat exchangers 94 may be provided.

[0040] According to this embodiment, a small and lightweight hybrid aircraft propulsion system can be provided. In addition, the hybridization can be achieved without increasing the size of the aircraft propulsion system, thereby reducing energy consumption and CO2 emissions.

[0041] The above has described in detail an embodiment of the cooling system for a hybrid propulsion device according to the present disclosure using the drawings, but the specific configuration is not limited to this embodiment, and even if there are design changes, etc., within the scope that does not deviate from the gist of the present disclosure, they are included in the present disclosure.

[0042] 1...aircraft, 11...propulsion device, 12...nacelle, 13...air intake, 20...propeller, 30...engine, 40...gearbox, 50...motor, 60...inverter, 70...battery, 80...controller, 91...first heat exchanger, 92...second heat exchanger, 93...third heat exchanger, 94...fourth heat exchanger, 101...fuel piping, 102...fuel pump, 103...fuel tank, 111...gear oil piping, 112...gear oil pump, 113...gear oil tank, 121...inverter refrigerant piping, 122...inverter refrigerant pump, 200...heat exchanger, 201...first fluid piping, 202...second fluid piping, 203...second fluid bypass piping, 211...first valve, 212...second valve, 213...third valve

Claims

1. A propulsion device for a hybrid aircraft comprising: an engine and motor that output rotational force; a gearbox that transmits the rotational force; a power converter that converts the power supplied to the motor; and a fuel flow path that supplies fuel to the engine, characterized in that the propulsion device for a hybrid aircraft comprises: a first refrigerant flow path that supplies refrigerant to the motor and gearbox; a second refrigerant flow path that supplies refrigerant to the power converter; and a heat exchanger in each of the first refrigerant flow path and the second refrigerant flow path that exchanges heat with the fuel flow path.

2. A hybrid aircraft propulsion device according to claim 1, characterized in that the motor is disposed upstream of the gearbox in the first coolant flow path.

3. A hybrid aircraft propulsion device as described in claim 1, characterized in that two heat exchangers are provided between the second refrigerant flow path and the fuel flow path, one of the two heat exchangers is arranged upstream of the power converter in the second refrigerant flow path, and the other of the two heat exchangers is arranged downstream of the power converter in the second refrigerant flow path.

4. A hybrid aircraft propulsion device as described in claim 3, wherein the two heat exchangers between the second refrigerant flow path and the fuel flow path are arranged such that one is located upstream and the other is located downstream of the heat exchanger located in the fuel flow path between the fuel flow path and the first refrigerant flow path.

5. A hybrid aircraft propulsion system according to claim 1, characterized in that it comprises one or more heat exchangers between the first refrigerant flow path and the second refrigerant flow path.

6. A hybrid aircraft propulsion device as described in claim 5, characterized in that the heat exchanger between the first refrigerant flow path and the second refrigerant flow path is located downstream of the motor in the first refrigerant flow path and upstream of the heat exchanger between the first refrigerant flow path and the fuel flow path.

7. A hybrid aircraft propulsion device according to any one of claims 1 to 5, characterized in that the heat exchanger has a switchable heat exchange flow path and a bypass flow path.

8. A hybrid aircraft propulsion device according to any one of claims 1 to 5, wherein the heat exchanger is provided with a switchable heat exchange flow path and a bypass flow path, and the propulsion device is provided with a control device that controls the switching between the heat exchange flow path and the bypass flow path based on one or more temperatures of the refrigerant in the first refrigerant flow path, the refrigerant in the second refrigerant flow path, and the fuel in the fuel flow path.

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