Aircraft engine and methods for operating it

Abstract

Engine (1) for aircraft, comprising several shafts (2) and a gas turbine (3) with a compressor (4) for compressing gas and a turbine (5), wherein the compressor (4) and the turbine (5) are rotationally fixed to the at least one shaft (2), and a combustion chamber (6), further comprising at least one fuel cell (7), wherein the gas turbine (3) and the at least one fuel cell (7) are connected to each other in such a way that, in the operating state, compressed gas (15) from the gas turbine (3) can be supplied to the at least one fuel cell (7), wherein it has at least one electric motor, wherein the fuel cell (7) is arranged for its energy supply and wherein the electric motor is arranged for at least indirectly driving the shafts (2), wherein each shaft (2) can be driven at least indirectly exclusively by an electric motor. wherein the fuel cell (7) has a reformer (9) for supplying the fuel cell (7) with fuel, and wherein the engine has an afterburner which is designed separately from the combustion chamber (6) and is configured to burn unburned residual fuel (16) of the fuel cell (7) as well as a portion of a fuel not converted by the reformer (9) and to supply the exhaust gases of the afterburner to the gas turbine (3) after the combustion chamber (6).

Description

[0001] The invention relates to an engine for aircraft comprising at least one shaft and a gas turbine with a compressor for compressing gas and a turbine, wherein the compressor and the turbine are rotationally fixed to the at least one shaft, as well as a combustion chamber, further comprising at least one fuel cell, and a method for operating such an engine.

[0002] When operating aircraft engines, their efficiency is of crucial importance, as this is directly related to fuel consumption and the generation of harmful exhaust gases.

[0003] To power electrical systems on board an aircraft, it is common practice to utilize the mechanical energy of the turbine and convert a portion of it into the required electrical energy via generators. Such conversion is detrimental to the turbine's efficiency and leads to increased fuel consumption.

[0004] It is also known to use fuel cells in aircraft, for example to supply energy to the cabin while the aircraft is on the ground. These fuel cells usually have a separate tank, especially for hydrogen, which means a significant additional space requirement and extra weight. Furthermore, the efficiency of these fuel cells is low.

[0005] RU 2 511 829 C2 discloses an aircraft engine with a gas turbine comprising a compressor, a turbine, and a combustion chamber. The engine also includes a fuel cell that powers subsystems. RU 2 652 842 C1 discloses an aircraft engine with a gas turbine, in which a compressor is fluidically coupled to a fuel cell. US 2008 / 0001038 A1 discloses an engine with a gas turbine and a fuel cell.

[0006] DE 10 2006 056 354 A1 and US 2017 / 0 211 474 A1 each disclose a propulsion device for an aircraft comprising a gas turbine unit, a fuel cell system and an electric motor.

[0007] The object of the invention is to provide an aircraft engine that has increased efficiency and is simultaneously designed to be space-saving. It is also an object of the invention to propose a method for operating such an optimized engine.

[0008] The problem directed towards an engine is solved by an engine according to claim 1.

[0009] The gas turbine and the at least one fuel cell are connected in such a way that, in the operating state, compressed gas from the gas turbine can be supplied to the at least one fuel cell.

[0010] The gas turbine features an arrangement of compressor, combustion chamber, and turbine with at least one shaft, which is essentially conventional in the prior art. Alternatively, the gas turbine can have multiple shafts, compressors, combustion chambers, and / or turbines. According to the invention, the compressor and turbine are connected in pairs to a shaft in a rotationally fixed manner, such that rotation of the turbine facilitates rotation of the compressor and vice versa. If multiple shafts are provided, a compressor and a turbine are each connected to a shaft according to the invention. Compressors / turbines are understood to mean, in particular, one or more radial or axial compressor / turbine stages arranged in series. Axial stages consist of a downstream arrangement of rotating blades and stationary "stator" blades. Radial stages typically do not include stators.

[0011] The inventive supply of the fuel cell with compressed gas or compressed air from the gas turbine leads to a significant increase in the efficiency and power density of the fuel cell due to the increased oxygen supply. At the same time, the invention eliminates the need for an additional compressor arrangement, as the fuel cell is supplied with compressed air from the gas turbine. Thus, the invention enables an increase in the efficiency of the fuel cell while simultaneously reducing its space requirements.

[0012] In an embodiment of the engine according to the invention, it is provided that it has means for directing exhaust gas from the fuel cell into the gas turbine before and / or in and / or after the combustion chamber, as well as into and / or after turbine 5. The exhaust gas from the fuel cell contains thermal energy in the form of waste heat. This thermal energy is transferred to a lower fuel combustion requirement of the gas turbine, since less energy is needed to achieve a specific turbine inlet temperature. The exhaust gas is then subsequently expelled from the engine together with the gas mixture of air and combusted kerosene.

[0013] According to the invention, the fuel cell includes a reformer for supplying the fuel cell with fuel, in particular hydrogen. Hydrogen is required to operate the fuel cell, and in this embodiment, it can be obtained from kerosene, for example, by means of a reformer. This has the advantage that other hydrogen-containing substances do not need to be carried separately, and only kerosene, which is required for the gas turbine anyway, can be used as fuel.

[0014] According to the invention, the engine is provided with an afterburner for combusting unburned residual fuel from the fuel cell. It may also include means for directing the residual fuel into the combustion chamber. In this way, the chemical energy contained in the residual fuel is converted through combustion. An afterburner is particularly advantageous when the exhaust gas from the fuel cell is fed to the gas turbine after the combustion chamber, before, in, or after the turbine, thus preventing the residual fuel from being burned in the combustion chamber itself. Furthermore, feeding residual fuel into the combustion chamber of the gas turbine can potentially lead to unpredictable or dangerous situations, since kerosene has a different combustion temperature than hydrogen, and a mixture of the two substances can result in differing combustion parameters in the combustion chamber.It is also possible for a portion of the supplied fuel that is not converted in the reformer to be burned in the afterburner.

[0015] In one embodiment of the invention, the fuel cell is designed to at least partially supply subsystems with energy generated within the fuel cell. Subsystems can be understood to include, for example, the aircraft's onboard electronics or, more generally, all electrical consumers in aircraft. This eliminates the need for a generator that converts the turbine's mechanical energy to produce the electrical energy required by the subsystems. Such a conversion is detrimental to the turbine's efficiency. The fuel cell combination according to the invention, however, utilizes only the chemical energy already present in the fuel to operate the engine, as well as the compressed air from the gas turbine directly, thus eliminating an efficiency-reducing intermediate step in the conversion to electrical energy.

[0016] In an embodiment of the engine according to the invention, it is provided that it has at least one electric motor, wherein the fuel cell (7) is arranged, in particular, for its energy supply and / or wherein the electric motor is arranged for at least indirect driving of the shaft (2). This enables a combined drive of the turbine by electric motor and gas turbine, which increases the flexibility of the engine. In particular, a combined drive of electric motor and gas turbine is advantageous in operating conditions in which high thrust is required, for example, during climb. Furthermore, the combination of fuel cell and electric motor increases the efficiency of the overall system and avoids idle times in which the energy of the fuel cell is only needed for other systems of the aircraft.According to the invention, an intermediate energy storage device is also required, in which the energy from the fuel cell can be temporarily stored as needed and from which energy can be drawn into electric motors or other systems of the aircraft as needed.

[0017] It is further planned that each shaft can be driven, at least indirectly, exclusively by an electric motor. This allows for particularly flexible operation of the engine, whereby, depending on requirements, the shaft can be driven either exclusively by the combustion power of the gas turbines, exclusively by the electric motor when the gas turbine is throttled or completely switched off, or by a combination of both of the aforementioned operating modes. Thus, in operating conditions where only low thrust is required, for example during descent, it is sufficient for the shaft to be driven exclusively by the electric motor, so that compressed air can still be supplied to the fuel cell.In contrast, a combined drive system using an electric motor and gas turbine, or exclusively by the gas turbine, is advantageous in operating conditions where high thrust is required, for example during climb.

[0018] In a further development of the invention, the engine is provided to have a fan blade connected to the shaft in a rotationally fixed manner and is designed in particular as a ducted jet engine or turboprop. With such an engine design, the mechanical energy in the shafts can be utilized for thrust both by the fan blade and by the warm, accelerated air from the turbine. Overall, this increases the efficiency of the entire system.

[0019] To solve the process problem, a method for operating a propulsion system with the features of the independent process claim is provided. Subsystems can be supplied with energy generated by the fuel cell. Supplying electrical subsystems with electrical energy generated in the fuel cell is significantly more efficient with regard to the turbine's efficiency compared to the otherwise necessary generator. Furthermore, no additional, wear-prone decoupling of a portion of the mechanical energy of the gas turbine or shaft is required. This increases the overall efficiency and operational reliability of the turbine.

[0020] With reference to the following figure, the invention is described by way of example in a preferred embodiment. The figure shows: Fig. 1: Schematic view of a preferred embodiment of a drive unit according to the invention.

[0021] Fig.Figure 1 schematically shows a view of an engine 1 according to the invention. In the illustrated embodiment, the engine 1 has a shaft 2 and a gas turbine 3, the gas turbine 3 being formed from a compressor 4 and a turbine 5, which are rotationally fixed to the shaft 2, and a combustion chamber 6, into which fuel 11, in particular kerosene, is introduced and burned during operation of the engine. An airflow is drawn into the engine 1 at one end opposite the turbine 5 and directed into the system. The airflow is compressed by the compressor 4. Gas 15 compressed in this way is directed into the combustion chamber 6, where it is mixed with a fuel, which is preferably atomized into the combustion chamber 6, and ignited together. The heated gas is then passed through the turbine 5, where the gas drives the turbine.The mixture exiting the turbine end of engine 1 generates thrust, which propels the vehicle or aircraft equipped with it. For additional thrust, a fan blade 10 can be provided, located at the end of engine 1 opposite turbine 5 and non-rotatably connected to shaft 2. The fan blade 10 is driven by turbine 5 through the non-rotatable connection of turbine 5 and compressor 4 to shaft 2. The fan blade 10 is designed such that its rotation results in further thrust for engine 1.

[0022] Furthermore, the engine 1 incorporates a fuel cell 7, which is integrated into the gas turbine 3 or at least effectively connected to it. The fuel cell 7 is supplied with a fuel, in particular hydrogen 17, which can be obtained either from a separate hydrogen tank, a reformer 9, or another source. A reformer 9 is particularly advantageous because it can convert the propellant 11, for example, kerosene, which is typically carried in an aircraft, into hydrogen 17 and byproducts. The byproducts can then be removed, while the hydrogen 17 is supplied to the fuel cell 7 as fuel and reacted within it.

[0023] To operate the fuel cell 7, a portion of the gas 15 compressed by the compressor 4 is introduced into the fuel cell 7 as bleed air 18. The compression increases the amount of oxygen in a smaller volume, resulting in a higher overall oxygen quantity in the fuel cell 7 compared to operation with an uncompressed airflow. The exhaust gases, and in particular the waste heat 13 contained therein, from the fuel cell 7 are then returned to the system and, in the illustrated configuration, mixed with the airflow before entering the combustion chamber 6. Residual fuel 16 from the fuel cell 7 or reformer 9, in the form of hydrogen 17 or propellant 11, is fed into the combustion chamber 6 and combusted there.Electrical energy 12 generated by the fuel cell 7 is used in particular to supply subsystems, such as the on-board electronics, thus eliminating other, less efficient conversions of the mechanical energy 14 of the shaft 2 and the gas turbine 3 into electrical energy, such as by a generator. REFERENCE MARK 1 engine 2nd wave 3 Gas turbine 4 compressors 5 Turbine 6 Combustion chamber 7 Fuel cell 8 Subsystem 9 Reformers 10 paddle wheel 11 Fuel 12 electrical energy 13 Waste heat 14 mechanical energy 15 compressed gas 16 Residual fuel 17 Hydrogen 18 bleed air

Claims

[1] Engine (1) for aircraft, comprising several shafts (2) and a gas turbine (3) with a compressor (4) for compressing gas and a turbine (5), wherein the compressor (4) and the turbine (5) are rotationally fixed to the at least one shaft (2), and a combustion chamber (6), further comprising at least one fuel cell (7), wherein the gas turbine (3) and the at least one fuel cell (7) are connected to each other in such a way that, in the operating state, compressed gas (15) from the gas turbine (3) can be supplied to the at least one fuel cell (7), wherein it comprises at least one electric motor, wherein the fuel cell (7) is arranged for the energy supply of the fuel cell, and wherein the electric motor is arranged for at least indirectly driving the shafts (2), wherein each shaft (2) can be driven at least indirectly exclusively by an electric motor. wherein the fuel cell (7) has a reformer (9) for supplying the fuel cell (7) with fuel, and wherein the engine has an afterburner which is designed separately from the combustion chamber (6) and is configured to burn unburned residual fuel (16) of the fuel cell (7) as well as a portion of a fuel not converted by the reformer (9) and to supply the exhaust gases of the afterburner to the gas turbine (3) after the combustion chamber (6). [2] Engine (1) according to claim 1, characterized by , that it has means for directing an exhaust gas from the fuel cell (3) before and / or in and / or after the combustion chamber (6), as well as in and / or after the turbine (5) into the gas turbine (3). [3] Engine (1) according to claim 1 or 2, characterized by , that the fuel is formed by hydrogen (17). [4] Engine (1) according to any one of the preceding claims, characterized bythat the fuel cell (7) is designed to supply at least part of subsystems with the energy generated in the fuel cell (7). [5] Engine (1) according to any one of the preceding claims, characterized by , that the engine (1) has a rotor blade (10) which is non-rotatably connected to the shaft (2) and is in particular designed as a ducted jet engine or turboprop. [6] Method for operating a drive unit (1) according to claim 1, characterized by , that - the fuel cell (7) is supplied with fuel by a reformer (9), and - unburned residual fuel (16) of the fuel cell (7) and a portion of a fuel not converted by the reformer (9) are burned in an afterburner which is designed separately from the combustion chamber (6), and - Exhaust gases from the afterburner of the gas turbine (3) are fed to the combustion chamber (6). [7] Method according to claim 6, wherein subsystems are supplied with energy generated by the fuel cell (7).

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