Aircraft powertrain

Abstract

The invention relates to a powerplant (1) for aircraft, comprising a 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 rotationally connected to the shaft (2), and a combustion chamber (6), further comprising at least one fuel cell (7). The invention aims to increase efficiency in all operating states and to provide a compact powerplant. To this end, the invention proposes that the shaft (2) can be driven at least indirectly and exclusively by at least one electric motor (8). Abstract figure: Figure 1

Description

Title of the invention: Aircraft powertrain

[0001] The present invention relates to an aircraft power unit comprising a shaft and a gas turbine with a compressor for compressing gas and a turbine, the compressor and turbine being rotationally connected to the shaft, as well as to a combustion chamber, the power unit further comprising at least one fuel cell. The present invention also relates to a method for operating such a power unit. technical field

[0002] This disclosure falls within the domain of aircraft powertrains. Previous technique

[0003] During the operation of aircraft powerplants, their efficiency or performance is of major importance as it goes hand in hand with fuel consumption and the production of harmful exhaust gases.

[0004] Because the requirements placed on powerplants vary depending on the aircraft's operating mode, it is necessary to optimize efficiency in all powerplant operating states. Thus, it is common practice in the prior art to control gas turbine powerplants according to their operating state, i.e., to slow the powerplant when the aircraft begins its descent and to fully utilize the powerplant when the aircraft begins its climb.

[0005] Furthermore, fuel cells are known to be used in aircraft to power, for example, the aircraft cabin when the aircraft is on the ground. These fuel cells usually have a separate tank, particularly for hydrogen, which results in a significant additional space requirement and weight. However, the operation of such systems involves either using the fuel cells exclusively to power onboard systems or only coupling them to the gas turbine to improve efficiency. Nevertheless, no system currently exists that specifically improves the flexibility of a powertrain's operation and efficiency in "non-nominal" operation. Summary

[0006] The present invention consequently aims to provide a powertrain for aircraft, in which efficiency is increased in all operating states and which at the same time has a configuration compact. Similarly, the present invention aims to provide a method for operating a correspondingly optimized powertrain.

[0007] The objective of a powertrain is achieved by means of a powertrain of the type mentioned in the introduction, in which the shaft can be driven at least indirectly exclusively by at least one electric motor.

[0008] In this context, the gas turbine has a generally common assembly in the prior art, consisting of a compressor, a combustion chamber, and a turbine with at least one shaft. Alternatively, the gas turbine may have several shafts, compressors, combustion chambers, and / or turbines. In this context, the compressor and the turbine are, according to the invention, connected in pairs in a rotationally fixed manner to a shaft such that a rotation of the turbine promotes a rotation of the compressor, and vice versa. If several shafts are provided, a compressor and a gas turbine are respectively connected according to the invention to a shaft.

[0009] A configuration of the invention in which the number of shafts corresponds to the number of compressors and turbines is correspondingly advantageous. Compressors or turbines are understood to mean, in particular, one or more radial or axial compressor or turbine stages arranged one after the other. These axial stages consist of a series of rotating blades and stationary blades. Radial stages, on the other hand, do not usually have any stationary blades. Furthermore, at least one electric motor is provided, by which at least one shaft can be driven. In the combustion chamber, a fuel, usually kerosene, which is ignited in the combustion chamber, is supplied to the system so that the temperature of the airflow in the combustion chamber area increases.Part of the compressed air flow from the compressor is directed to at least one fuel cell, which can react the compressed air with a greater quantity of oxygen and is therefore more efficient. The energy produced by the fuel cell powers, as needed, a wide variety of aircraft or propulsion systems.

[0010] According to the invention, the shaft can nevertheless also be driven exclusively by the electric motor. This allows for flexible operation of the powertrain, which makes it possible, as required, to drive the shaft exclusively by the combustion power of the gas turbines, exclusively by the electric motor in the event of a slowdown or complete shutdown of the gas turbine, or by a combination of the two operating modes mentioned above. Thus, it suffices, in operating conditions where only low propulsion power needs to be produced, for example during descent, to drive the shaft exclusively by the electric motor. The shaft can be driven exclusively by the electric motor, allowing compressed air to be supplied to the fuel cell via the compressor. Conversely, a combined drive from the electric motor and gas turbine, or exclusively from the gas turbine, is advantageous in operating conditions where significant propulsion power is required, such as during aircraft startup.

[0011] In one configuration of the invention, the powertrain has several shafts, or rather, one shaft that can be driven, in particular at least indirectly and exclusively, by an electric motor. If the powertrain has several shafts, these are arranged according to the invention, preferably coaxially with respect to each other, to save space within the powertrain. The plurality of shafts makes it possible to achieve, during corresponding control, significantly higher powertrain efficiencies from time to time. If, in one configuration of the invention, one shaft can be driven by one of the electric motors, the control of the shafts is made possible by the corresponding control of the electric motors.

[0012] The improved version of the invention provides that the fuel cell is arranged to supply power to at least one electric motor. This improves the overall system efficiency and avoids downtime, during which the fuel cell's energy is only required for other aircraft systems. An energy storage unit connected in an intercalated manner is provided for this purpose according to the invention, in which energy from the fuel cell can be temporarily stored if needed, and energy can then be released, if necessary, to electric motors or other aircraft systems.

[0013] In one configuration of the invention, the fuel cell is designed to supply at least some subsystems with energy produced within the fuel cell. In particular, in operating states where the gas turbine is driven exclusively by fuel combustion, energy from the fuel cell, which is not required for the electric motors, can power subsystems.

[0014] An improvement to the invention provides that the gas turbine and the fuel cell are connected in such a way that compressed gas in its operating state from the gas turbine can be supplied to the fuel cell. Supplying compressed gas, in particular compressed air, from the gas turbine to the fuel cell significantly increases the efficiency of the fuel cell due to the greater quantity of oxygen supplied. Furthermore, a separate compressor for the fuel cell or oxygen enrichment means can be used to further increase efficiency. are not necessarily required.

[0015] The powertrain configuration according to the invention is provided for means of conveying exhaust gas from the fuel cell before and / or into and / or after the combustion chamber in the gas turbine. It is also possible to return the exhaust gas into and / or after the turbine. The exhaust gas from the fuel cell increases the efficiency of the gas turbine due to the higher temperature, as it contributes to the temperature increase of the gas turbine airflow that is otherwise achieved by fuel combustion in the combustion chamber.

[0016] An improvement to the invention provides that the fuel cell has a reformer for supplying the fuel cell with fuel, in particular hydrogen. Hydrogen is required to operate the fuel cell, which in this embodiment can be obtained from kerosene, for example, by a reformer. This has the advantage that other possible hydrogen-containing substances do not need to be transported separately and that only kerosene, which is typically required for the gas turbine, can be used as fuel.

[0017] The powertrain configuration according to the invention is provided for by an afterburner for burning unburned residual fuel from the fuel cell. Such an afterburner is particularly advantageous when the exhaust gas from the fuel cell is fed to the gas turbine after the combustion chamber, thus preventing the residual fuel from being burned in the combustion chamber itself. Furthermore, feeding residual fuel into the gas turbine combustion chamber presents certain unforeseen risks or uncertainties under certain circumstances, 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.

[0018] An improvement to the invention provides that the powertrain has a blade wheel fixedly connected for rotation to the shaft and is configured in particular as a spooled-beam or turboprop powertrain. In such a powertrain configuration, the mechanical energy in the shafts can be used both by the blade wheel and by the accelerated hot air from the turbine for propulsion power. Overall, the efficiency of the entire system is thus improved.

[0019] The problem related to a method for operating a powertrain of the aforementioned type is solved in that the shaft is driven at least indirectly exclusively by at least one electric motor. This makes possible a function Flexible operation of the powertrain. The shaft can be driven as needed exclusively by the combustion power of the gas turbines, exclusively by the electric motor during deceleration or a complete stop in the gas turbine, or by a combination of the two aforementioned operating modes. In operating states such as descent, it is therefore advantageous when the shaft is driven exclusively by the electric motor so that compressed air from the compressor can be supplied to the fuel cell. Conversely, driving the shaft is advantageous, for example, during the start-up procedure or during ascent with a combination of the electric motor and the gas turbine, or exclusively by the gas turbine in operational states, since the gas turbine must be driven in any way to provide the required propulsion power. Brief description of the drawings

[0020] The present invention is described by way of example in a preferred embodiment with reference to the following figure, in which one can see: Fig. 1

[0021] [Fig.1] a schematic view of a powertrain 1 according to the invention. Description of the implementation methods

[0022] Figure 1 illustrates a schematic view of a power unit 1 according to the invention. In the illustrated embodiment, the power unit 1 comprises a shaft 2 and a gas turbine 3. The gas turbine 3 is formed from a compressor 4 and a turbine 5, which are rotationally connected to the shaft 2, and from a combustion chamber 6, into which fuel, in particular kerosene, is introduced and burned. An airflow is received into the power unit 1 at one end facing the turbine 5 and is routed through the system. The airflow is compressed by the compressor 4. The compressed gas is routed into the combustion chamber 6, where it is mixed with a fuel, which is preferably atomized in the combustion chamber 6, and is ignited simultaneously. The heated gas is then guided through turbine 5, in which gas drives the turbine.The gas exiting at the turbine end of the propulsion unit 1 thus provides propulsion, by which the propulsion unit 1 propels the aircraft equipped with it.

[0023] To produce additional propulsion, a blade wheel 10 may be provided, which is located at the end, facing the turbine 5, of the power unit 1 and is fixedly connected in rotation to the shaft 2. The fixed connection in rotation of the turbine 5 and the compressor 4 to the shaft 2 allows the blade wheel 10 to be driven by the airflow indirectly through the compressor 4 and the turbine 5.

[0024] The paddle wheel 10 is in this context made in such a way that a rotational movement of the latter results in another propulsion of the powertrain 1.

[0025] Furthermore, a fuel cell 7 is provided in the powertrain 1, which is housed in the gas turbine 3 or is at least actively connected to it. The fuel cell 7 is supplied with hydrogen, which may come from a separately driven hydrogen tank, a reformer 9, or another source.

[0026] A reformer 9 is particularly advantageous in this context because it can transform, for example, kerosene, which is used in all manner in an aircraft, into hydrogen and residual products. In this context, the residual products can be separated while the hydrogen is fed into the fuel cell 7 and reacts therein.

[0027] To operate the fuel cell 7, a portion of the airflow compressed by the compressor 4 is introduced into the fuel cell 7.

[0028] The exhaust gases from the fuel cell 7 are then returned to the system and are mixed with the airflow or gas mixture before, in or after the combustion chamber 6 or in or after the turbine 5 and are discharged.

[0029] The energy produced by the fuel cell 7 can be used to power subsystems such as onboard electronics or to power an electric motor 8. Alternatively, an energy storage unit is also possible, in which the energy produced is temporarily stored and can be drawn from the latter as needed. In this configuration, the electric motor 8 is connected to the shaft 2 or the compressor 4 in such a way that it drives it, at least indirectly. Direct drive of the turbine 5 by the electric motor 8 is also possible. The electric motor 8 is thus designed so that it can operate the shaft 2 independently, and therefore, in particular, without the addition of kerosene, even when the gas turbine 3 is stopped.This is particularly advantageous in operating conditions, such as when the aircraft is descending, where no or only low propulsion power from the power unit 1 is desired; however, efficient operation of the fuel cell 7 depends on a flow of compressed air. If the compressor 4 continues to be driven by the electric motor 8, the latter can continue to compress the supplied airflow and supply the fuel cell 7 without particularly high propulsion being produced by the gas turbine 3. List of reference signs

[0030] 1 Powertrain 2 Tree 3 Gas Turbine 4 Compressor 5 Turbine 6 Combustion chamber 7 Fuel Cell 8 Electric motor 9 Reformer 10 Paddle wheel.

Claims

Claims

1. Power unit (1) for aircraft, having a 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 connected to the shaft (2) in a rotationally fixed manner, and with a combustion chamber (6), further having at least one fuel cell (7), characterized in that the shaft (2) can be driven at least indirectly exclusively by at least one electric motor (8) and in that the power unit (1) has several shafts (2), and in that each shaft (2) can be driven at least indirectly exclusively by one electric motor (8), and so that the control of the shafts is made possible by the corresponding control of the electric motors.

2. Powertrain (1) according to claim 1, characterized in that it has means for conveying an exhaust gas from the fuel cell (7) in front of and / or into and / or after the combustion chamber (6) in the gas turbine (3).

3. Powertrain (1) according to claim 2, characterized in that it has an afterburner for burning unburned residual fuel from the fuel cell (7).

4. Powertrain (1) according to any one of the preceding claims, characterized in that the fuel cell (7) is arranged to supply the at least one electric motor (8) with energy.

5. Powertrain (1) according to claim 4, characterized in that the fuel cell (7) is designed to at least partially supply subsystems with energy produced in the fuel cell (7).

6. Powertrain (1) according to any one of the preceding claims, characterized in that the gas turbine (3) and the fuel cell (7) are connected to each other in such a way that compressed gas in the operating state from the gas turbine (3) can be supplied to the fuel cell (7).

7. Powertrain (1) according to any one of the preceding claims, characterized in that the fuel cell (7) has a reformer (9) for supplying the fuel cell (7) with fuel, in particular hydrogen.

8. Powertrain (1) according to any one of the claims

9. previous, characterized in that the power unit (1) has an impeller (10) connected in a rotationally fixed manner to the shaft (2) and is configured in particular as a casing beam power unit or turboprop. Method for operating a powertrain (1) according to any one of the preceding claims, characterized in that the shaft (2) is driven at least indirectly exclusively by the at least one electric motor (8).

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