DE102014224637A1 - Hybrid electric propulsion system for an aircraft - Google Patents

Abstract

The invention relates to a hybrid electric propulsion system for an aircraft. The system comprises a single main engine (10), a first thruster (50) and a second thruster (55). The single main combustion engine (10) is configured to drive the first thrust unit (50) by means of a mechanical connection (60). The system further includes an electric motor (25) adapted to drive the second thrust unit (55). It is the inventive idea to further provide a generator (20) adapted to convert mechanical energy generated by the single main combustion engine (10) into electrical energy, the generator being configured to supply the electric motor (25) with electrical energy Food. According to the invention, both thrust units can be driven by the single main engine (10), which allows the use of a larger, more efficient main engine (10) during normal flight operations.

Description

The invention relates to a hybrid electric propulsion system for an aircraft. The system comprises a main engine, a first thrust unit and a second thrust unit. The main combustion engine is configured to drive the first thrust unit by means of a mechanical connection. The system further includes an electric motor configured to drive the second thrust unit.

With rising fossil fuel prices and increasing demand for reducing harmful emissions, research into "green energy" and propulsion technologies that are an alternative to burning fossil fuels has become increasingly important around the world since about the beginning of the 21st century. Electric propulsion is currently considered a promising alternative, mainly due to the excellent efficiency of electric motors. While aircraft internal combustion engines typically generate mechanical power using only about 30-60% of the total energy stored in combustion fuel, electric motors convert electrical power into efficiencies at efficiencies that exceed 95%. High efficiency means that only a small part of the electrical energy stored on board is wasted. This is a good prerequisite for greener propulsion, because even if electric power is generated in fossil-fuel electric power plants, the heavy-duty power plants tend to have significantly higher efficiency and lower emissions than internal combustion engines Vehicles are used. Furthermore, electrical energy can be generated using zero emissions renewable sources.

However, prior art electric vehicles powered exclusively by batteries have one major drawback: low endurance resulting from the significantly lower energy density of batteries compared to carbon-based combustion fuel. Therefore, battery-powered electric vehicles are only suitable for a narrow range of application, in which a high endurance is not required, for. On the other hand, most transport vehicles generally require high endurance, making battery-only energy storage an inappropriate option in most applications. Hybrid electric drive is one solution to this problem - it offers a compromise between the efficiency of the electric drive and the high energy density of carbon-based fuel.

For aircraft, two basic hybrid electric propulsion designs are known. The first construction is referred to as hybrid electric parallel string (short: parallel strand), the second as hybrid electric train series (short: series train).

Both designs enhance the conventional non-hybrid drivetrain for aircraft, which typically includes one or more thrust units, e.g. As a propeller or propeller, each mechanically driven by an internal combustion engine.

In parallel string systems, each push unit is driven by an internal combustion engine and an electric motor. An electric energy storage system drives the electric motor. Both the internal combustion engine and the electric motor are coupled to the thrust unit by the same mechanical connection, e.g. B. by a drive shaft. In such an arrangement, the torque delivered by the drive shaft is the sum of the torque output of the engine and the torque output of the electric motor. The main power source is usually the internal combustion engine, while the electric motor can provide a power boost when needed, e.g. This design reduces the variation in engine power output during operation, thus loosing its design requirements and allowing it to operate at near-optimal efficiency during most of normal aircraft operation. Examples of parallel string systems for aircraft are in the documents US 2012/0209456 A1 or US 2013/0227950 A1 disclosed.

In mass train systems, the internal combustion engines are not mechanically coupled to the thrust units, but only the electric motors deliver torque to the thrust units. The electrical power that powers the electric motors is provided by at least one internal combustion engine that drives a generator to generate electrical power. In addition, an electric energy storage system may be provided to deliver additional electrical energy to the electric motors. The series train therefore requires a generator to convert the mechanical power provided by the engine into electrical power delivered to the electric motor, which in turn generates mechanical power that is delivered to the pusher unit via a mechanical connection. These additional components usually result in a significant weight penalty. In addition, cause a generator and an electric motor a certain loss of power: z. B. both have an efficiency of 97%, amount to combined losses of hybrid series power transmission between the engine and the thrust unit to more than 6%. Therefore, the internal combustion engine must compensate for these losses by generating correspondingly more power.

Regardless of the drawbacks involved, the series strand can still be used when high operational flexibility is needed. The internal combustion engine and thrust unit are decoupled, allowing both to operate at rotational speeds that are independent of each other at all times, thus potentially improving the efficiency of both. Further, the series arrangement also allows a single internal combustion engine to drive multiple thrusters without the need for a complex and heavy drive shaft system. The document US / 20130062455 A1 discloses the construction of an aircraft that provides high operational flexibility through the use of a series train system.

In view of the above-described prior art, it is the object of the present invention to combine the advantages of both parallel-string and series-train hybrid electric drive systems and at least partially avoid the disadvantages of the prior art systems. The object is solved by the features of the independent claims. Preferred embodiments are described in the dependent claims.

According to the invention, the hybrid electric drive system comprises a single main combustion engine configured to drive a first thrust unit and a generator configured to convert mechanical energy generated by the single main combustion engine into electrical energy and to power the electric motor with electrical energy ,

First, some terms used in the context of the invention will be explained.

The term "thrust unit" includes any thrust or lift generating device such as a propeller, propeller, buoyancy rotor, buoyancy screw, etc.

Further, the term "internal combustion engine" covers any type of device that generates mechanical energy from the combustion of fuel, such as a gasoline engine, Atkinson cycle engine, diesel engine, two-stroke or six-stroke engine, spin engine (eg Wankel engine), continuous internal combustion engine (eg a gas turbine) etc.

The term "main engine" refers to an internal combustion engine that provides enough power to drive the first thruster unit through the mechanical link and to drive the generator so that, at the same time, enough power can be passed to the second thruster unit. When the main engine is configured to drive the pusher unit, it means that mechanical energy generated by the engine is at least partially used to drive the pusher unit by means of the mechanical connection.

To provide enough power to the push unit means that in normal operation the power supplied is sufficient for all normal flight situations, for aircraft emergency operations as required for certification, and / or for a flight situation requiring a high level of thrust. A "flight situation that requires a high level of thrust" is, for example, during take-off, take-off or any other situation where a comparable thrust level is required. For example, if a main engine, generator or engine is to provide a power output sufficient for flight situations requiring a high thrust level, this means that the main engine, generator or engine power output has a power that allows the pilot to communicate with to handle the flight situations adequately.

The features of the present invention provide the ability to use a first portion of the mechanical energy generated by the single main engine to drive the first thruster. A second portion of the mechanical energy generated by the main engine is used by the generator to generate electrical energy. The generator is adapted to feed the electric motor with electrical energy, which in turn is adapted to drive the second thrust unit. Accordingly, two thrust units are driven by the single main engine without the need for a complex and heavy drive shaft system.

Compared with the prior art systems, the configuration of the invention offers several advantages. First, unlike the parallel string system, the present invention allows only a single main engine to be used to drive both the first and second thrust units as described above. Accordingly, instead of using two internal combustion engines each driving a single thrust unit (as is the case with a parallel rail system), the present invention allows a single larger size main engine to be used. The usage of a single main combustion engine of larger size is more advantageous than the use of two equivalent smaller size combustion engines because internal combustion engines tend to be more efficient when designed for higher power levels. This is because frictional forces (fluid friction, mechanical friction of rotating parts, internal air pressure losses, etc.) tend to be stronger for smaller engines when placed in relation to the output of the engine.

Accordingly, the present invention enables more efficient and therefore fuel-efficient operation of an aircraft.

Compared with a series train system, the present invention offers further advantages. In a series train system, at least one internal combustion engine generates mechanical energy that is converted into electrical energy by a generator. The electrical energy is supplied to electric motors, each driving a thrust unit. Accordingly, in a series train system with two thrust units, at least one internal combustion engine, one generator, and two electric motors are needed to drive the thrusters. In contrast, the present invention proposes to mechanically drive the first thrust unit and electrically drive the second thrust unit. Accordingly, only one internal combustion engine, one generator and one electric motor are required, resulting in a weight advantage compared to the series train system. Since the first thrust unit is mechanically driven, electrical losses are further reduced.

For safety reasons, aircraft propulsion systems typically must provide certain redundancies in the event of engine failure. In an advantageous embodiment, therefore, the hybrid electric drive system comprises an electric energy storage device. The electric energy storage device may be any device configured to supply electrical energy during aircraft operation and, in particular, may include batteries, condensers or fuel cells. It is further preferred that the generator comprises a drive mode in which it is designed to drive the first thrust unit. This means that the generator is designed to be used both as a generator and as a motor (in drive mode) for driving the first thrust unit. The provision of an electric energy storage device in combination with a generator comprising a drive mode has several advantages.

Some types of main engines require the supply of power to start the engine, for example, to handle inertia and / or friction within the engine. The generator can therefore also be designed to start the main combustion engine. In this case, there is no need for a separate starter motor for the main engine.

First, in the case of failure of the single main engine, the electric power storage device can provide electric power to the generator and the electric motor. The generator is used in this case to drive the first thrust unit. Therefore, both thrust units can be driven using electric power provided by the electric power storage device. It may be necessary in this case to decouple the first thrust unit from the main engine. Preferably, therefore, the hybrid electric drive system includes a decoupling device for coupling / decoupling the main combustion engine from the first thrust unit.

Second, the above features allow for the benefits of the hybrid drive system. For example, it is possible to shut off the main engine during periods of low power consumption, for example, during coasting (when the aircraft is moving on the ground) or during descent phases. Further, during flight phases where much power is needed (eg, during the flight phases: climb, takeoff, or takeoff), it is possible to use the electric power storage device to provide additional power to the electric motor for driving the second push unit. The generator may also be configured to supply electrical energy to the electric energy storage device. Therefore, the generator can be used to recharge the electric energy storage device.

However, in some situations, an electrical energy storage device may not be able to deliver a sufficient amount of power for a sufficient amount of time. This may be the case, in particular, when the propulsion system is used in aircraft which must be able to fly an evasive maneuver evasion mission after a failure of the main engine. The challenge is that dodge typically requires a large amount of stored energy, and as stated earlier, the low energy densities of known electric energy storage technologies make them unsuitable for such applications. If the main engine fails in a large aircraft, an additional reserve power source may be needed in addition to the electric power storage device

In a preferred embodiment, therefore, the hybrid electric drive system includes a backup engine. Preferably, the reserve combustion engine is configured to drive the second thrust unit by means of a mechanical connection. It is further preferred that a decoupling device for coupling / decoupling the reserve combustion engine from the second thrust unit is provided. In this case, the backup engine may be coupled to the second thrust unit, if needed, and may be decoupled from the second thrust unit if the second thrust unit is driven only by the electric motor.

In an alternative embodiment, the backup engine could be mechanically connected to an auxiliary generator to provide electrical power to the electric motor and / or the generator for driving the first and / or second thruster units. The backup engine may also be used to recharge the electric energy storage device.

In an advantageous embodiment, the electric motor comprises a generation mode in which it is designed to convert mechanical energy generated by the reserve combustion engine into electrical energy and to supply the generator with the electrical energy. According to this feature, the electric motor can be used as a generator to generate electricity for driving the first thrust unit. In addition, the electric motor may also be configured to feed the electric energy storage device with electrical energy.

It is further preferred that the backup engine be smaller and / or lighter in design than the main engine. For example, the maximum power output of the reserve combustion engine may be at a level that is insufficient for flight situations requiring a high thrust level. Preferably, the maximum power output of the reserve combustion engine may be less than 60%, preferably less than 45%, more preferably less than 30% of the maximum power output of the single main engine. The backup engine may therefore be designed to be smaller and / or lighter than the main engine, so that in the event of a main engine failure, an alternate flight may be made at lower altitudes and lower speeds than normal cruise, thereby requiring only a fraction of the thrust level required during cruising , On the other hand, some situations require much higher thrust levels, e.g. B. Start or launch situations. However, take-off and start-up are relatively short-lived and therefore do not require much stored energy, which means that the electric energy storage device can store a suitable amount of reserve energy for these situations without significant weight penalty. This stored reserve of electrical energy can be supplied to the generator and the electric motor, thus assisting the reserve engine in the event of flight situations requiring a high thrust level. Therefore, the preferred embodiment actually employs two internal combustion engines, but one of them is lighter and / or smaller in design and is mainly used as a backup device. It is therefore not necessary to provide two engines of comparable size, which allows a cost and weight savings; At the same time the efficiency reducing power division is avoided during normal operation.

In a preferred embodiment, the transfer of electrical energy between the electric energy storage device, the generator and the electric motor is controlled by a power management and distribution system. If the generator or electric motor generates electrical energy at any time during operation, such a power management and distribution system may handle the generated electrical power output by either allocating it to the electric energy storage device for recharging or to the remainder of the generator or electric motor, or by supplying a portion of the power of the electric energy storage device and the remainder of the power to the remainder of the generator or electric motor. When both the generator and the electric motor generate electric power by converting mechanical energy of each of the main engine and the spare internal combustion engine, the power management and distribution system can handle the corresponding output of electric power and supply it to the electric power storage apparatus for recharging.

The hybrid electric drive system may comprise at least one further thrust unit, which is driven by at least one further electric motor, wherein the generator and / or electric motor is adapted to feed the at least one further electric motor with electrical energy. By means of this configuration, the system according to the invention can, if necessary, be extended to any number of thrust units.

The present invention further relates to an aircraft comprising an airframe and a hybrid electric propulsion system according to the present invention.

The invention further provides a method of operating an aircraft using a hybrid electric propulsion system in accordance with the present invention. The method according to the invention is characterized in that it comprises the steps of driving a first propulsion unit by means of a single main combustion engine, driving a generator by means of the main combustion engine, feeding an electric motor with electrical energy generated by the generator and driving a second thrust unit by means of the electric motor. The method according to the invention can be further extended by using one or more of the features described above in connection with the hybrid electric drive system according to the invention.

The features, objects, and advantages of the invention will become more apparent from the following exemplary description of preferred embodiments, taken in conjunction with the accompanying drawings, in which:

1 FIG. 2 is a schematic diagram of a first embodiment of a hybrid electric propulsion system according to the invention. FIG.

2 FIG. 3 is a schematic diagram of an alternative embodiment of a power management and distribution system according to the invention coupled to a plurality of electric motors and generators. FIG.

3 FIG. 2 is a schematic diagram showing a detailed view of the mechanical connection between the main engine and the first thrust unit and between the reserve engine and the second thrust unit. FIG.

4 a schematic diagram of a second embodiment of a hybrid electric drive system according to the invention with more than two thrust units, and

5 a schematic diagram of an alternative embodiment of a hybrid electric propulsion system according to the invention.

1 shows a schematic diagram of a first preferred embodiment of a hybrid electric propulsion system according to the invention. The system comprises two thrust units 50 and 55 , a single main combustion engine (MCE) 10 , a reserve combustion engine (BCE) 15 , a fuel tank 80 , Fuel line systems 90 and 95 , a generator 20 , an electric motor 25 , an electric energy storage device (EES device) 40 , a Performance Management and Distribution (PMD) system 30 and electro-conductor systems 70 . 71 and 75 , Each of the thrust units 50 and 55 is each with a mechanical connection 60 or 65 connected. The mechanical connections 60 . 65 can be a drive shaft. The mechanical connection 60 couples the generator 20 with the push unit 50 ; the mechanical connection 65 couples the electric motor 25 with the push unit 55 , The MCE 10 is the main power source during normal operation; he is with the push unit 50 over the mechanical connection 60 in parallel with the generator 20 coupled. The BCE 15 is a backup power device that provides a maximum power output of only 30% of the maximum power output of the MCE 10 and therefore is not sufficient for flight situations requiring a high level of he is with the push unit 55 over the mechanical connection 65 in parallel with the electric motor 25 coupled.

During normal operation, the MCE is 10 in use and the BCE 15 not in use. In this case, the MCE burns 10 Fuel to generate mechanical energy. A first part of the mechanical energy is sent to the first push unit 50 by means of the mechanical connection 60 transferred to the first push unit 50 drive. A second part of the mechanical energy is generated by the generator 20 converted into electrical energy, with which the electric motor 25 is fed. The electric motor in turn converts the electrical energy into mechanical energy to the second thrust unit 55 drive. The electrical energy generated by the generator may also be the EES device 40 to be recharged. The distribution of electrical energy is through the PMD system 30 controlled.

In case of failure of the MCE 10 can the BCE 15 be used. In this case, the BCE burns 15 Fuel to generate mechanical energy. A first part of the mechanical energy is transferred to the second push unit 55 by means of the mechanical connection 65 transferred to the second push unit 55 drive. A second part of the mechanical energy can be through the electric motor 25 (which in this case is used as a generator) are converted into electrical energy, with which the generator 20 is fed. The generator (which in this case is used in drive mode) converts the electrical energy into mechanical energy around the first thrust unit 50 drive. It is also possible through the BCE 15 generated mechanical energy entirely for driving the second thrust unit 55 to use. In this case it is necessary to use the generator 20 with in the EES device 40 stored electrical energy to the first thrust unit 50 drive. The EES device 40 can also use the electric motor 25 feed with electrical energy to the BCE 15 to support.

The BCE 15 not only in case of failure of MCE 10 can also be used simultaneously with the MCE 10 Provide performance, especially in flight situations where immediate access to a high thrust level is required when the MCE 10 failed, z. B. during the launch or start-up. The simultaneous use of BCE 15 and MCE 10 can also increase aircraft take-off performance, which may be useful for STOL (Short Take-Off and Landing) or VTOL (Vertical Take-Off and Landing) applications.

The MCE 10 and the BCE 15 be through the fuel in the fuel tank system 80 powered and convert the energy stored in the fuel into mechanical energy. The EES device 40 can through the PMD system 30 both the generator 20 as well as the electric motor 25 provide electrical power, which then convert this into mechanical power, that of the corresponding thrust unit 50 . 55 through the appropriate mechanical connection 60 . 65 is supplied.

MCE 10 and BCE 15 use fuel as a source of energy and generate mechanical power as a delivery. Examples of internal combustion engine technologies include: piston engines such as a gasoline engine, Atkinson cycle engine, diesel engine, two-stroke or six-stroke engine; Rotary motors, z. B. a Wankel engine; continuously operating internal combustion engines, eg. B. a gas turbine. For the invention, it is not necessary that MCE 10 and BCE 15 of the same type of technology. However, it is preferred that MCE 10 and BCE 15 use the same type of fuel. MCE 10 is the main source of power during normal aircraft operation and is preferably designed for optimal fuel efficiency. BCE 15 has a maximum power output that is insufficient for flight situations that require a high thrust level, and is mainly used as a reserve power source if the MCE 10 fails during normal operation, or used as an additional power source during flight situations requiring a high thrust level; as such, it is preferably designed for minimum weight and not efficiency.

In the preferred embodiment, both the MCE 10 as well as the BCE 15 a gas turbine. In alternative embodiments, both the MCE 10 as well as the BCE 15 use any combustion engine technology.

The one from MCE 10 and BCE 15 used fuel is in the fuel tank system 80 saved. The fuel tank system 80 may include a single tank or multiple fuel storage tanks. The fuel tank system 80 stored fuel can MCE 10 and BCE 15 each via the fuel line system 90 and 95 be supplied.

In normal operation, the generator uses 20 a mechanical power consumption to provide an electric power output while the electric motor 25 used an electrical power consumption to produce a mechanical power output. However, it is normally possible for an electric motor and a generator to switch between a drive mode and a generation mode, so that the generator 20 could generate mechanical power by consuming electrical energy, and the electric motor 25 electrical energy could be generated by mechanical power is supplied to it. The preferred embodiment utilizes this functionality to increase the operational flexibility of the hybrid string. The generator 20 and the electric motor 25 may be the same in performance level or design principle, but this is not mandatory.

The generator 20 and the electric motor 25 are with the PMD system 30 through the electric wire systems 70 and 75 connected. In the preferred embodiment, the generator 20 and the electric motor 25 identical in size and construction principle.

In an alternative embodiment, a system may be provided by a plurality of generators and electric motors. As in 2 As shown, the system can be made up of a variety of generators 20-1 . 20-2 , ... 20 m and from a variety of electric motors 25-1 . 25-2 , ... 25-n where m and n are positive integers. Every generator and electric motor is compatible with the PMD system 30 coupled via an electric cable. For example, the generator 20-1 with the PMD system via the electric wire 70-1 coupled, the generator 20-2 over the electric wire 70-2 and so on.

The EES device 40 can store electrical energy and provide electrical power to the generators and electric motors or to any electrically powered aircraft system when needed. The EES device 40 can include any EES technology, e.g. Primary or secondary batteries, fuel cells, capacitors, etc. There may also be additional sources of electricity generation in the design of the EES device 40 be included, for. As solar panels, wind turbines, etc. These could be used either for the filling of electrical energy during operation or for the direct feeding of electric motors.

In the preferred embodiment, the EES system exists 40 from a single battery part comprising secondary battery cells, which Motors and electrical systems of the aircraft supplied with electrical power, for example in the flight phases: taxiing, descent, climb and take-off.

In alternative embodiments, however, there is no limitation on the number of said EES devices or the type of EES technology. The EES device may include various components. Each of these components could comprise a different EES technology type.

An example of the EES device in an alternative embodiment: the EES device 40 can consist of two components, wherein the first component is a battery part consisting of secondary cells of high specific energy, which increases the aircraft performance during take-off and climb and, if necessary, on take-off and the electrical systems of the aircraft feeds, while the second component, a battery part consisting of secondary battery cells is of high specific power that boosts the generator or electric motor with additional power simultaneously with the first component, but only during the startup process and when takeoff is required. All components of the EES device 40 are preferably with the PMD system through an electrical line 71 coupled.

The PMD system 30 manages the exchange of electrical power between the elements 20 . 25 and 40 as required for an aircraft control input (not shown in the figures). The aircraft control input may be manual or part of an automated control system. The PMD system 30 may be configured to convert an electrical power output of specific voltage and specific type into another voltage or other type required by the input of the other component. For example, it may be designed to provide a DC electric power output of an EES device at a voltage of 5,000 volts to an AC type at a voltage of 1,500 volts required by the generator or electric motor or any other electric current input. which may be required to transform.

The thrust units 50 . 55 use the mechanical power output of the power generating units MCE 10 , BCE 15 , Generator 20 and electric motor 25 caused by the mechanical connections 60 and 65 is supplied to generate thrust. In flight mechanics, thrust is generally a force in the direction of travel of the aircraft relative to the ambient air. Examples of applicable thrust producing devices are propellers and jacketed propellers. The construction of the thrust units 50 . 55 However, it should not be limited to the examples given.

In the preferred embodiment, the thrusters are 50 and 55 Variable pitch propellers of identical size and construction attached to the sides of a rigid wing of an aircraft. In alternative embodiments, the thrust units are 50 and 55 but not necessarily of identical size, thrust capacity or design principle.

In alternative embodiments, the thrusters may also be used to provide lift during flight, for quick take-off and landing, or vertical take-off and landing. Examples of such embodiments may be rotary-wing, swivel-rotor or tilt-wing concepts with at least two thrust units.

The thrusters may be mounted at any location on the airframe of an aircraft (not shown in the figures). For example, the thrust unit 50 in one embodiment, be a variable pitch propeller designed for maximum static thrust of 50 kN and attached to the nose of the aircraft while the propulsion unit 55 is a ducted propeller designed for a maximum static thrust of 55 kN and attached to the rear of the aircraft. In a further alternative embodiment, the pushing unit 50 a variable pitch propeller designed for a maximum static thrust of 55 kN while the thrust unit 55 is a variable pitch propeller designed for a maximum static thrust of 50 kN. The push unit 50 can be mounted on the left side of the aircraft wing, while the thrust unit (TU) 55 can be mounted on the right side of the aircraft wing. The push unit 50 can be more internal than the push unit 55 be attached so that the total yaw moment at maximum thrust is zero.

The mechanical connection 60 transfers mechanical power between MCE 10 , Generator 20 and push unit 50 , The mechanical connection 65 transfers mechanical power between BCE 15 , Electric motor 25 and push unit 55 , Normally, each of the components 10 . 15 . 20 . 25 . 50 and 55 be a service provider as well as a consumer. The thrust units 50 and 55 usually consume mechanical power to generate thrust, but can also generate mechanical power by propulsion through wind. The generator 20 and electric motor 25 can be used to provide both mechanical power as a motor and to consume mechanical power as a generator. MCE 10 and BCE 15 usually provide power, but when turned off, they can need a power input to get started. The construction of mechanical connections 60 and 65 may include direct mechanical connections, such as mechanical shafts or drive belts, drive speed and shaft torque varying mechanical devices, such as transmissions, and devices for coupling and decoupling mechanical connections, such as clutches or one-way bearings or position changing devices, such as linear motors.

3 shows a schematic diagram showing a detailed view of preferred mechanical connections between the MCE 10 and the first push unit 50 as well as between the reserve combustion engine 15 and the second push unit 55 illustrated. In the in 3 embodiment shown includes the mechanical connection 60 a gearbox 60-1 , a clutch 60-2 and mechanical waves 60-3 . 60-4 and 60-5 , The mechanical wave 60-5 connects the push unit 50 with the gearbox 60-1 , The mechanical wave 60-3 connects MCE 10 with the clutch 60-2 while the mechanical shaft 60-4 the coupling 60-2 , the generator 20 and the gearbox 60-1 coupled. The gear 60-1 can mechanical power between the mechanical shaft 60-4 and the mechanical shaft 60-5 while allowing for different rotational speeds on each of the two shafts. With this construction are the mechanical shaft 60-3 and the mechanical shaft 60-4 for the rotational speeds of MCE 10 and generator 20 designed while the mechanical shaft 60-5 for the rotational speeds of the thrust unit 50 is designed. The coupling 60-2 can the mechanical shaft 60-3 with the mechanical shaft 60-4 couple or, if necessary, decouple them. When the clutch 60-2 the mechanical shaft 60-3 with the mechanical shaft 60-4 coupled, mechanical performance can be between MCE 10 , Generator 20 and push unit 50 be transmitted. When the clutch 60-2 the mechanical shaft 60-3 from the mechanical shaft 60-4 decoupled, mechanical power can only be between generator 20 and push unit 50 be transmitted, which is the operation of the thrust unit 50 only by the generator 20 allows.

The mechanical connection 65 consists of a gearbox 65-1 , a clutch 65-2 and mechanical waves 65-3 . 65-4 and 65-5 , The functionality of these elements is analogous to the elements of the mechanical connection 60 ,

The mechanical connections in alternative embodiments may utilize any combination of direct mechanical connections, such as mechanical shafts or drive belts, drive speed modifying mechanical devices such as transmissions, and devices for coupling and decoupling mechanical connections such as clutches or one-way bearings. Symmetry between the two mechanical connections is not a requirement.

Alternative embodiments of the invention may use more than two thrust units. When adding thrust units to the drive train of the invention, there are several options for each additional thrust unit to be supplied with mechanical power: it can mechanically with the mechanical connection 60 be coupled, which would allow it, mechanical performance of the MCE 10 and generator 20 to use; It can be mechanical with the mechanical connection 65 coupled, which would allow it mechanical performance of BCE 15 and electric motor 25 to use; It can come with one or more additional through the PMD system 30 controlled electric motors are mechanically coupled; or a combination of the options mentioned.

An example of the drive system of the invention in an alternative embodiment having more than two thrust units is shown in FIG 4 shown. While the basic powertrain construction of 1 is maintained, there are two additional thrust units 51 and 56 and an additional electric motor 21 , The push unit 51 is with the electric motor 21 via a mechanical connection 61 coupled. The electric motor 21 is through a PMD system 30 controlled, with which he over an electric wire system 72 connected is. The push unit 56 is with the mechanical connection 65 through another mechanical connection 66 coupled. Therefore, mechanical power can be between BCE 15 , Electric motor 25 , Push unit 55 and push unit 56 be transmitted. In normal operation, the MCE performs 10 the push unit 50 and the generator 20 via a mechanical connection 60 mechanical power too. The push unit 50 uses part of it through the MCE 10 supplied mechanical power by generating thrust. The generator 20 also uses part of the MCE 10 supplied mechanical power, thereby generating electrical power. The PMD system 30 distributed by generator 20 generated electric power to electric motor 21 and electric motor 25 , electric motor 21 converts a part of the generator 20 generated electrical power into mechanical power, then through the mechanical connection 61 to the push unit 51 is transmitted and by the thrust unit 51 is converted into thrust. electric motor 25 converts a part of the generator 20 generated electrical power into mechanical power, then through the mechanical connection 65 and the mechanical connection 66 to the push unit 55 and push unit 56 is transmitted and by the thrust unit 55 and push unit 56 is converted into thrust. Therefore, the MCE 10 In this example, supply power to all four thrust units. Similarly, BCE 15 and EES device 40 also supply power to all four thrust units.

In alternative embodiments, a mechanical coupling between the mechanical connections 60 . 65 be provided. In some cases, this feature could be advantageous as there is a direct transfer of mechanical performance from MCE 10 to both thrust units 50 and 55 would allow. For such a structure is appropriate, the mechanical coupling between the mechanical connection 60 and the mechanical connection 65 however, be equipped with a coupling / decoupling device to allow for operational flexibility. Such embodiments may be particularly advantageous when the thrust units 50 and 55 are arranged close to each other, z. B. at the rear of the aircraft, so that the mechanical coupling between the mechanical connection 60 and the mechanical connection 65 not too long and heavy.

In the preferred embodiment of the invention, the BCE 15 the push unit 55 directly perform mechanical power and can also be the thrust unit 55 drive by using the hybrid series approach using the electric motor 25 used in a generation mode to the generator 20 to supply electrical power.

5 shows an alternative embodiment of a hybrid electric drive system according to the invention. With this embodiment, a further improvement of the flexibility of the component integration in the airframe is achieved. This is the BCE 15 with the mechanical connection 65 not mechanically connected, instead is the BCE 15 via a mechanical connection with an electric generator 27 coupled. The electric generator 27 turn is with the PMD system 30 via an electric cable 77 coupled. With such a construction is the BCE 15 capable of powering all thrusters using the Hybrid Series approach. As already mentioned, the hybrid series approach increases flexibility at the expense of increased weight and reduced efficiency. Since the BCE 15 is primarily a backup power source, the overall performance penalty for the embodiments employing the latter design may not be as significant as the gain in flexibility.

In the preferred embodiment, the BCE serves 15 mainly as a reserve power source. It enables safe aircraft operation if the MCE 10 fails. In some applications, reserve power may not be a necessary feature for a convenient application. Alternative embodiments of the invention designed for such applications may include the BCE 15 as a component of the powertrain. In such embodiments, the EES device may 40 used to increase the safety of the aircraft, if the MCE 10 fails.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2012/0209456 A1 [0006]
• US 2013/0227950 A1 [0006]
• US 20130062455 A1 [0008]

Claims (14)

A hybrid electric propulsion system for an aircraft, comprising: a single main engine ( 10 ); a first push unit ( 50 ) and a second thrust unit ( 55 ), the main combustion engine ( 10 ) is adapted to the first thrust unit ( 50 ) by means of a mechanical connection ( 60 ) to drive; an electric motor ( 25 ), which is adapted to the second thrust unit ( 55 ) to drive; characterized in that the hybrid electric propulsion system further comprises a generator ( 20 ), which is adapted to be driven by the main engine ( 10 ) converted mechanical energy into electrical energy and the electric motor ( 25 ) to feed with electrical energy. Hybrid electric drive system according to claim 1, characterized in that the hybrid electric drive system further comprises an electric energy storage device ( 40 ). Hybrid electric drive system according to claim 2, characterized in that the generator is further adapted to the electric energy storage device ( 40 ) to feed with electrical energy. Hybrid electric drive system according to one of claims 1 to 3, characterized in that the generator ( 20 ) further comprises a drive mode in which the generator ( 20 ) is adapted to the first thrust unit ( 50 ) to drive. Hybrid electric drive system according to one of claims 1 to 4, characterized in that the system further comprises a decoupling device ( 60-2 ) for coupling / decoupling the main combustion engine ( 10 ) from the first push unit ( 50 ). Hybrid electric propulsion system according to one of claims 1 to 5, characterized in that the hybrid electric propulsion system further comprises a reserve combustion engine ( 15 ), wherein the reserve combustion engine preferably has a maximum power output of less than 60%, preferably less than 45%, more preferably less than 30% of the maximum power output of the main engine. Hybrid electric drive system according to claim 6, characterized in that the reserve combustion engine ( 15 ) is adapted to the second thrust unit ( 55 ) by means of a mechanical connection ( 65 ) to drive. Hybrid electric drive system according to claim 7, characterized in that the system comprises a decoupling device ( 65-2 ) for coupling / decoupling the reserve combustion engine ( 15 ) from the second push unit ( 55 ). Hybrid electric drive system according to one of claims 6 to 8, characterized in that the electric motor ( 25 ) comprises a generation mode in which it is adapted to be operated by the reserve internal combustion engine ( 15 ) converted mechanical energy into electrical energy and the generator ( 20 ) to feed with the electrical energy. Hybrid electric drive system according to claim 9, wherein the electric motor ( 25 ) is adapted to the electrical energy storage device ( 40 ) to feed with electrical energy. Hybrid electric drive system according to one of claims 2 to 10, characterized in that the transmission of electrical energy between the electric energy storage device ( 40 ), the generator ( 20 ) and the electric motor ( 25 ) through a service management and distribution system ( 30 ) is controlled. Hybrid electric drive system according to one of claims 1 to 11, characterized in that the system at least one further thrust unit ( 51 ) by at least one further electric motor ( 21 ), the generator ( 20 ) and / or the electric motor ( 25 ) is adapted to the at least one further electric motor ( 21 ) to feed with electrical energy. An aircraft comprising an airframe and a hybrid electric propulsion system according to any one of claims 1 to 12. A method of operating an aircraft using a hybrid electric propulsion system according to any one of claims 1 to 12, characterized in that it comprises the following steps: a. Driving a first push unit ( 50 ) by means of a single main combustion engine ( 10 b. Driving a generator ( 20 ) by means of the main combustion engine ( 10 c. Food of an electric motor ( 25 ) with the generator ( 20 ) generated electrical energy, d. Driving a second thrust unit ( 55 ) by means of the electric motor ( 25 ).

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