Method for propelling an aircraft, propulsion system, and aircraft

Abstract

In the method for propelling an aircraft, to obtain electric energy, a fuel is combusted, and an electric machine is used, wherein the fuel is used to cool at least one part of the electric machine and contains natural gas. The propulsion system is configured to propel an aircraft, in particular according to the above-mentioned method. The propulsion system has an electric machine configured to obtain electric energy by combusting a fuel. The propulsion system further includes a natural gas tank configured to supply the fuel formed with natural gas, and a cooling device configured to cool at least one part of the electric machine. The aircraft has such a propulsion system.

Claims

1. A method for propelling an aircraft, the method comprising: cooling at least one part of an electric machine with a coolant, wherein the coolant is supplied to the at least one part of the electric machine at a cryogenic temperature of less than 80 K, and wherein the coolant is heated in the cooling of the at least one part of the electric machine; transferring the coolant to a heat exchanger; cooling the coolant to the cryogenic temperature using the heat exchanger via a heat exchange with a fuel, wherein at least a portion of the fuel is evaporated, and wherein the coolant is cycled via a coolant circuit back to the at least one part of the electric machine; transferring the evaporated fuel to an internal combustion engine; combusting the evaporated fuel to convert combusted energy into mechanical energy; converting, by the electric machine coupled to the internal combustion engine, the mechanical energy into electrical energy; and propelling the aircraft using the electric energy.

2. The method of claim 1, wherein the at least one part of the electric machine is cooled to a temperature less than 80 K, and/or wherein the at least one part of the electric machine is a component part of a generator, a rotor, a stator, or a combination thereof.

3. The method of claim 1, wherein the cryogenic temperature is no more than 30 K.

4. The method of claim 1, wherein the fuel comprises liquified natural gas.

5. The method of claim 1, wherein the fuel comprises liquified hydrogen.

6. A propulsion system for propelling an aircraft, the propulsion system comprising: an electric machine configured to obtain electric energy by combustion of a fuel; a fuel tank configured to supply the fuel; a cooling device in communication with the fuel tank, wherein the cooling device is configured to cool at least one part of the electric machine with a coolant supplied to the at least one part of the electric machine at a cryogenic temperature of less than 80 K, and wherein the coolant is configured to be heated in the cooling of the at least one part of the electric machine; a heat exchanger in communication with the cooling device, wherein the heat exchanger is configured to receive the coolant from the cooling device, wherein the coolant is configured to be cooled to the cryogenic temperature using the heat exchanger via a heat exchange with the fuel provided from the fuel tank, wherein at least a portion of the fuel is configured to be evaporated, and wherein the coolant is configured to be cycled via a coolant circuit back to the at least one part of the electric machine; and an internal combustion engine in communication with the heat exchanger, wherein the internal combustion engine is configured to receive the evaporated fuel and combust the evaporated fuel into mechanical energy, wherein the electric machine is mechanically coupled to the internal combustion engine, and wherein the electric machine is configured to convert the mechanical energy into electrical energy to propel the aircraft.

7. The propulsion system of claim 6, wherein the at least one part of the electric machine is configured to operate at the cryogenic temperature.

8. The propulsion system of claim 6, wherein the at least one part of the electric machine is configured for superconductive operation.

9. The propulsion system of claim 6, wherein the heat exchanger is an evaporator.

10. The propulsion system of claim 6, wherein the fuel comprises liquified natural gas.

11. The propulsion system of claim 6, wherein the fuel comprises liquified hydrogen.

12. An aircraft comprising: a propulsion system comprising: an electric machine configured to obtain electric energy by combustion of a fuel; a fuel tank configured to supply the fuel; a cooling device in communication with the fuel tank, wherein the cooling device is configured to cool at least one part of the electric machine with a coolant supplied to the at least one part of the electric machine at a cryogenic temperature of less than 80 K, and wherein the coolant is configured to be heated in the cooling of the at least one part of the electric machine; a heat exchanger in communication with the cooling device, wherein the heat exchanger is configured to receive the coolant from the cooling device, wherein the coolant is configured to be cooled to the cryogenic temperature using the heat exchanger via a heat exchange with the fuel provided from the fuel tank, wherein at least a portion of the fuel is configured to be evaporated, and wherein the coolant is configured to be cycled via a coolant circuit back to the at least one part of the electric machine; and an internal combustion engine in communication with the heat exchanger, wherein the internal combustion engine is configured to receive the evaporated fuel and combust the evaporated fuel into mechanical energy, wherein the electric machine is mechanically coupled to the internal combustion engine, and wherein the electric machine is configured to convert the mechanical energy into electrical energy to propel the aircraft.

13. The aircraft of claim 12, wherein the heat exchanger is an evaporator.

14. The aircraft of claim 12, wherein the fuel comprises liquified natural gas.

15. The aircraft of claim 12, wherein the fuel comprises liquified hydrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is explained in more detail below with the aid of an exemplary embodiment illustrated in the drawings.

(2) FIG. 1 depicts a first exemplary embodiment of a propulsion system of an aircraft for executing a method for propelling the aircraft in a schematic diagram.

(3) FIG. 2 depicts a second, likewise implemented exemplary embodiment of a propulsion system of an aircraft for executing a further likewise implemented method for propelling the aircraft in a schematic diagram.

(4) FIG. 3 depicts an example of an aircraft with a propulsion system according to FIGS. 1 and 2.

DETAILED DESCRIPTION

(5) The propulsion system 10 illustrated in FIG. 1 is a serial hybrid propulsion system of an electric aircraft 20 (see also FIG. 3).

(6) The propulsion system 10 has an electric machine 30, which, to realize as low a power-to-weight ratio as possible, has a cryogenic part, in the illustrated exemplary embodiment one with a rotor 40 formed with a superconductive material. The superconductive rotor 40 is designed to operate below the transition temperature of the superconductive material, in this case to operate at 20 K.

(7) The propulsion system has a cooling system 50 to cool the rotor 40 of the propulsion system 10. The cooling system 50 includes a cold head 60, which abuts against the rotor 40 and transmits heat from the rotor 40 as a result of the thermal contact between the cold head 60 and the rotor 40.

(8) A propulsion capacity 65 of the propulsion system 10 is used to operate a refrigeration machine 70 of the cooling system. The refrigeration machine 70 uses the propulsion capacity 65 of the propulsion system 10 and pumps heat from the cold head 60 as waste heat 80 into a heat bath. The heat bath is formed by a liquid natural gas 90, which represents a fuel of the propulsion system 10 and is held in a fuel tank in the form of a natural gas tank 100. The refrigeration machine 70 therefore pumps heat into the natural gas tank 100 and heats the natural gas 90 located in the natural gas tank 100.

(9) The natural gas (not illustrated explicitly) evaporated as result of the heating of the natural gas tank 100 is conducted by a fuel line 110 to an internal combustion engine 120 of the propulsion system 10 of the aircraft 20. The internal combustion engine 120 is designed to combust the evaporated natural gas and to convert the released combustion energy into mechanical energy. The evaporated natural gas therefore forms the fuel of the internal combustion engine 120. The internal combustion engine 120 is mechanically coupled by a shaft 130 to the electric machine 30, which is designed and arranged to convert the mechanical energy into electric energy. To supply electric consumers, for instance a propeller 140 and an on-board power supply system of the aircraft 20, the electric machine 30 is electrically connected thereto via electric lines 150.

(10) As illustrated in FIG. 2, the liquid natural gas 90 of the natural gas tank 100 is moreover used to cool a stator 160 of the electric machine 30.

(11) To this end, the electric machine 30 has a coolant circuit 170, which is designed for a coolant to flow along the stator 160 and to be cooled as a result of the thermal contact. To this end, the coolant circuit 170, in a manner known per se, has a pump 180 which is designed and arranged to pump the coolant, here a cooling fluid, through the coolant circuit 170. The coolant is heated by the stator 160 during the operation of the propulsion system 10 and subsequently conducted via a coolant line 185 to a heat exchanger in the form of an evaporator 190. By the evaporator 190, the heat of the coolant which is absorbed at the stator 160 may be transferred to a portion of the liquid natural gas 90, which is guided to the evaporator 190 via a natural gas delivery line 195. The liquid natural gas may consequently evaporate and therefore extract heat from the coolant. The evaporated natural gas may additionally be overheated at the evaporator 190 so that, owing to the overheating of the evaporated natural gas, additional refrigerating capacity is additionally introduced into the coolant circuit 170.

(12) In the aircraft 20, both exemplary embodiments of the propulsion system 10 which are illustrated in FIGS. 1 and 2 are likewise implemented. Alternatively, in further exemplary embodiments of the aircraft 20, which moreover correspond to the illustrated exemplary embodiments, it is possible for only one of the two exemplary embodiments of the propulsion system 10 which are illustrated in FIGS. 1 and 2 to be implemented in each case.

(13) The method for propelling the aircraft 20 is carried out as described above, e.g., the above-described propulsion system 10 of the aircraft 20 is used as designated.

(14) The evaporated natural gas is subsequently supplied to the internal combustion engine 120 as fuel (not shown explicitly in FIG. 3).