DE102019216905A1 - Aircraft engine and method of operation - Google Patents

Abstract

To an engine (1) for aircraft, having at least one shaft (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 non-rotatably connected to the at least one shaft (2), as well as a combustion chamber (6), further comprising at least one fuel cell (7), in which the efficiency is increased and which is designed to save space at the same time, it is proposed that the gas turbine (3) and the at least one fuel cell (7) are connected to one another in such a way that, in the operating state, compressed gas (15) from the gas turbine (3) can be fed to the at least one fuel cell (7).

Description

The invention relates to an engine for aircraft having at least one shaft and a gas turbine with a compressor for compressing gas and a turbine, the compressor and the turbine being non-rotatably connected to the at least one shaft, as well as a combustion chamber, furthermore having at least one fuel cell, and a method of operating such an engine.

In the operation of aircraft engines, their efficiency or their degree of effectiveness is of decisive importance, since this goes hand in hand with the consumption of fuel and the generation of harmful exhaust gases.

In order to supply electrical systems on board an aircraft, it is known to use the mechanical energy of the turbine and to convert part of it into the required electrical energy via generators. Such a conversion is detrimental to the efficiency of the turbine and leads to increased fuel consumption.

It is also known to use fuel cells in aircraft in order, for example, to supply the aircraft cabin with energy when the aircraft is on the ground. These fuel cells mostly have a separate tank, in particular for hydrogen, which means a high additional space requirement and additional load. Furthermore, the efficiency of these fuel cells is low.

The object of the invention is therefore to specify an engine for aircraft in which the efficiency is increased and which is designed to save space at the same time. It is also the object of the invention to propose a method for operating a correspondingly optimized engine.

The object directed to an engine is achieved by an engine of the type mentioned at the outset, in which the gas turbine and the at least one fuel cell are connected to one another in such a way that compressed gas from the gas turbine can be fed to the at least one fuel cell in the operating state.

The gas turbine has an arrangement of compressor, combustion chamber and turbine with at least one shaft that is essentially customary in the prior art. Alternatively, the gas turbine can have several shafts, compressors, combustion chambers and / or turbines. According to the invention, the compressor and the turbine are non-rotatably connected in pairs to a shaft, so that a rotation of the turbine favors rotation of the compressor and vice versa. If several shafts are provided, a compressor and a turbine are each connected to a shaft according to the invention. Compressors / turbines are to be understood in particular as one or more radial or axial compressor / turbine stages arranged one behind the other. Axial stages consist of a series of rotating blades and stationary “stator” blades. Radial steps usually occur without stators.

The supply of the fuel cell according to the invention with compressed gas or compressed air from the gas turbine leads, via the increased oxygen supply, to a considerable increase in the efficiency and the power density of the fuel cell. At the same time, according to the invention, an additional compressor arrangement is dispensed with in that the fuel cell is supplied with compressed air from the gas turbine. The invention thus enables an increase in the efficiency of the fuel cell with simultaneously reduced space requirements.

In an embodiment of the engine according to the invention, it is provided that it has means for guiding an exhaust gas from the fuel cell upstream and / or into and / or downstream of the combustion chamber into the gas turbine, as well as into and / or downstream of the turbine 5 . The exhaust gas from the fuel cell has 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 required to achieve a specific turbine inlet temperature. A subsequent elimination of the exhaust gas from the engine then takes place together with the gas mixture of air and burned kerosene.

In a further development of the invention it is provided that the fuel cell has a reformer for supplying the fuel cell with fuel, in particular with hydrogen. To operate the fuel cell, hydrogen is required, which in this exemplary embodiment can be obtained from kerosene, for example, by a reformer. This has the advantage that other hydrogen-containing substances do not have to be carried separately and only kerosene, which is required for the gas turbine in any case, can be used as fuel.

In an embodiment of the invention it is provided that it has an afterburner for burning unburned residual fuel of the fuel cell and / or that it has means for guiding the residual fuel into the combustion chamber. In this way, the chemical energy contained in the residual fuel is converted through the combustion. An afterburner is particularly advantageous if the exhaust gas from the fuel cell is fed to the gas turbine after the combustion chamber, before, in or after the turbine, and thus the residual fuel is not burned in the combustion chamber itself. In addition, feeding the residual fuels into the combustion chamber of the gas turbine can lead to unpredictability or dangers, since kerosene has a different combustion temperature than hydrogen and a mixture of the two substances leads to different combustion parameters in the combustion chamber. A portion of a supplied fuel that is not converted in the reformer can also be burned in the afterburner.

In an embodiment of the invention it is provided that the fuel cell is designed to at least partially supply subsystems with energy generated in the fuel cell. In this context, subsystems are to be understood as meaning, for example, the aircraft's on-board electronics or, more generally, all electrical consumers in aircraft. This eliminates the need for a generator that converts the mechanical energy of the turbine to generate the electrical energy required for the sub-systems. A corresponding conversion is disadvantageous for the efficiency of the turbine. The fuel cell combination according to the invention, on the other hand, uses only the chemical energy already present in the fuel to operate the engine and the compressed air of the gas turbine directly, eliminating an intermediate step in the conversion into electrical energy that is detrimental to efficiency.

In an embodiment of the engine according to the invention, it is provided that it has at least one electric motor, the fuel cell ( 7th ) is arranged in particular for its energy supply and / or wherein the electric motor for at least indirectly driving the shaft ( 2 ) is arranged. This enables a combined drive of the turbine from the electric motor and gas turbine, which increases the flexibility of the engine. In particular, a combined drive consisting of an electric motor and a gas turbine is advantageous in operating conditions in which a high propulsive power is required, for example when climbing. 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 required for other systems of the aircraft. For this purpose, an energy store connected in between is also according to the invention, in which the energy from the fuel cell can be temporarily stored if required and from this energy can be discharged into electric motors or other systems of the aircraft if required.

It is further provided that in each case one shaft can be driven, at least indirectly, exclusively by an electric motor. This enables particularly flexible operation of the engine, with the shaft being driven exclusively by the combustion power of the gas turbines, exclusively by the electric motor with a throttled or completely switched off gas turbine, or by a combination of the two aforementioned operating modes, as required. In operating states in which only a low propulsive power has to be generated, for example when descending, it is sufficient if the shaft is driven exclusively by the electric motor so that air compressed by the compressor can continue to be supplied to the fuel cell. In contrast, a combined drive from the electric motor and gas turbine or exclusively by the gas turbine is advantageous in operating states in which a high propulsive power is required, for example when climbing.

In a further development of the invention, it is provided that the engine has a blade wheel connected to the shaft in a rotationally fixed manner and is designed in particular as a ducted jet engine or turboprop. With such a configuration of the engine, the mechanical energy in the shafts can be used for propulsive power both through the blade wheel and through the warm, accelerated air from the turbine. Overall, this increases the efficiency of the overall system.

To solve the method problem, the invention proposes, when operating an engine according to claim 1, that subsystems are supplied with energy generated by the fuel cell. The supply of electrical subsystems with electrical energy generated in the fuel cell is significantly more efficient with regard to a generator that would otherwise be necessary with regard to the efficiency of the turbine. There is also no need for an additional, wear-prone decoupling of part of the mechanical energy of the gas turbine or shaft. This increases the overall efficiency and operational reliability of the turbine.

• 1: schematische Ansicht einer bevorzugten Ausführungsform eines erfindungsgemäßen Triebwerks.

With reference to the following figure, the invention is described by way of example in a preferred embodiment. It shows:

• 1 : schematic view of a preferred embodiment of an engine according to the invention.

1 shows schematically a view of an engine according to the invention 1 . The engine 1 has a shaft in the illustrated embodiment 2 and a gas turbine 3 on, with the gas turbine 3 is formed from a compressor 4th and a turbine 5 , which rotatably with the shaft 2 are connected, as well as a combustion chamber 6th , in which in the operating state of the engine fuel 11 , especially kerosene, is imported and burned. An air flow is created in the engine 1 on one of the turbine 5 opposite end and fed into the system. The air flow is through the compressor 4th condensed. Such compressed gas 15th is in the combustion chamber 6th directed where it is with a fuel, which in the combustion chamber 6th is preferably dusted, mixed and ignited together. The heated gas continues through the turbine 5 in which the gas drives the turbine. This is created by the at the turbine end of the engine 1 exiting mixture a feed through which the engine 1 drives the vehicle or aircraft provided with it. A paddle wheel can be used for additional feed 10 be provided, which is located on the turbine 5 opposite end of the engine 1 and rotatably with the shaft 2 connected is. Due to the non-rotatable connection of the turbine 5 and the compressor 4th with the wave 2 becomes the paddle wheel 10 through the turbine 5 driven. The paddle wheel 10 is designed in such a way that a rotary movement results in a further advance of the engine 1 results.

Next is in the engine 1 a fuel cell 7th provided, which in particular in the gas turbine 3 recorded or at least effectively connected with this. The fuel cell 7th comes with a fuel, especially hydrogen 17th supplied, which either from a separately carried hydrogen tank, a reformer 9 or from another source. A reformer 9 is particularly beneficial as this is the fuel 11 , for example kerosene, which is typically carried on an airplane, in hydrogen 17th and can convert residual products. The residual products can be excreted, while the hydrogen 17th the fuel cell 7th is supplied as fuel and is converted in this.

For operating the fuel cell 7th becomes part of the through the compressor 4th compressed gas 15th as bleed air 18th into the fuel cell 7th introduced. As a result of the compression, an increased amount of oxygen is achieved in a smaller volume, so that the total amount of oxygen in the fuel cell 7th is increased compared to operation with a non-compressed air flow. The exhaust gases and especially the waste heat they contain 13th the fuel cell 7th are then fed back into the system and, in the embodiment shown, with the air flow in front of the combustion chamber 6th mixed. Residual fuel 16 from fuel cell 7th or reformer 9 is in the form of hydrogen 17th or fuel 11 into the combustion chamber 6th directed and burned there. Electrical power 12th made by the fuel cell 7th is generated, is used in particular to supply subsystems 8th , such as the on-board electronics, used, which other, less efficient conversions of mechanical energy 14th the wave 2 and the gas turbine 3 in electrical energy, such as by a generator, are omitted.

List of reference symbols

1

Engine

2

wave

3

Gas turbine

4th

compressor

5

turbine

6th

Combustion chamber

7th

Fuel cell

8th

Subsystem

9

reformer

10

Paddle wheel

11

fuel

12th

electrical power

13th

Waste heat

14th

mechanical energy

15th

compressed gas

16

Residual fuel

17th

hydrogen

18th

Bleed air

Claims (9)

Engine (1) for aircraft, having at least one shaft (2) and a gas turbine (3) with a compressor (4) for compressing gas and a turbine (5), the compressor (4) and the turbine (5) being non-rotatable are connected to the at least one shaft (2), as well as a combustion chamber (6), further comprising at least one fuel cell (7), characterized in that the gas turbine (3) and the at least one fuel cell (7) are connected to one another in such a way that in the operating state, compressed gas (15) from the gas turbine (3) can be fed to the at least one fuel cell (7). Engine (1) according to Claim 1 , characterized in that it has means for guiding an exhaust gas from the fuel cell (3) upstream and / or in and / or downstream of the combustion chamber (6) and in and / or downstream of the turbine (5) into the gas turbine (3) . Engine (1) according to Claim 1 or 2 , characterized in that the fuel cell (7) has a reformer (9) for supplying the fuel cell (7) with fuel, in particular with hydrogen (17). Engine (1) according to Claim 1 , 2 or 3 , characterized in that it has an afterburner for burning unburned residual fuel (16) of the fuel cell (7) and / or that it has means for guiding the residual fuel (16) into the combustion chamber (6). Engine (1) according to one of the preceding claims, characterized in that the fuel cell (7) is designed to at least partially supply subsystems (8) with the energy generated in the fuel cell (7). Engine (1) according to one of the preceding claims, characterized in 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 to at least indirectly drive the shaft (2). Engine (1) according to Claim 6 , characterized in that in each case one shaft (2) can be driven at least indirectly exclusively by an electric motor. The engine (1) according to any one of the preceding claims, characterized in that the engine (1) has an impeller (10) connected to the shaft (2) in a rotationally fixed manner and is designed in particular as a ducted jet engine or turboprop. Method for operating an engine (1) according to Claim 1 , characterized in that subsystems (8) are supplied with energy generated by the fuel cell (7).

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