Aircraft, in particular aeroplane

Abstract

The invention relates to an aircraft, in particular an aeroplane, having a wing assembly, a fuselage with a longitudinal axis, a fuel system and at least two engines allocated to the fuselage, in particular arranged in the fuselage, wherein a first engine and a second engine have different maximum thrusts and at least one of the engines is configured for operation with different fuels, wherein the fuel system has a first fuel tank for supplying the drive with a liquid fossil fuel, wherein the fuel system has a second fuel tank for supplying the drive with a cryogenic fuel, wherein the second fuel tank is designed in a pressure-resistant manner for receiving the cryogenic fuel and is received in the fuselage.

Description

[0001] Aircraft, in particular an airplane

[0001] The invention relates to an aircraft, in particular an airplane, with a supporting structure, a fuselage with a longitudinal axis, a fuel system and at least two engines of a drive assigned to the fuselage, in particular arranged in the fuselage, wherein a first engine and a second engine have different maximum thrusts from one another and at least one of the engines is designed for operation with different fuels, wherein the fuel system has a first fuel tank for supplying the drive with a liquid fossil fuel.

[0002] Current aircraft, especially airplanes, are powered by liquid fossil fuels, such as kerosene or aviation gasoline. Experimental aircraft are also known that combine different fuel systems, such as auxiliary electric propulsion.

[0003] In this case, operating with sustainable fuel is often not possible within the context of continuous flight operations. Furthermore, structural challenges arise, especially in smaller aircraft such as business jets.

[0004] US 5,855,340 A discloses an aircraft with engines of different power levels, which are arranged in the rear area of ​​a fuselage.

[0005] US 2016 / 0195013 A1 describes an aircraft with cryogenic propulsion, which uses compressed natural gas (LNG). A tank for the LNG is located in the fuselage of the aircraft. It is also disclosed to produce a fuel mixture of the LNG and paraxylene to provide the possibility of operating the aircraft with LNG as an alternative to liquid fuel.

[0006] US 2005 / 0178890 A1 describes an aircraft with engines of different power levels, with the respective engines being arranged in a rear area of ​​the fuselage of the aircraft.

[0007] US 2002 / 0074453 A1 discloses a similarly constructed aircraft.

[0008] The article “Wikipedia: Hawker Siddeley Trident” describes the equipping of an aircraft with an auxiliary engine to increase takeoff thrust.

[0009] The object of the invention is to improve the state of the art.

[0010] The object is achieved by an aircraft, in particular an airplane, having a supporting structure, a fuselage with a longitudinal axis, a fuel system and at least two engines of a drive system assigned to the fuselage, in particular arranged in the fuselage, wherein a first engine and a second engine have different maximum thrusts from one another and at least one of the engines is designed for operation with different fuels, wherein the fuel system has a first fuel tank for supplying the drive with a liquid fossil fuel, wherein the fuel system has a second fuel tank for supplying the drive with a cryogenic fuel, wherein the second fuel tank is designed to be pressure-resistant for receiving the cryogenic fuel and is accommodated in the fuselage.

[0011] By means of the cryogenic fuel, which can be fed to one of the engines, for example, via the second fuel tank on the fuel system, the respective engines can be operated with different fuels. Furthermore, the fuel tank accommodated in the fuselage can, for example, be used as a structural component or be part of the fuselage structure, thus achieving an overall weight saving. The arrangement of the second fuel tank in the fuselage also offers advantages for integration into the aircraft structure, since the available space in the fuselage allows auxiliary systems necessary for operating the second fuel tank, which may be present for special requirements of a cryogenic fuel, to be accommodated within the fuselage. Furthermore, ecological operation of the aircraft is possible through the use of cryogenic fuel, for example in certain flight conditions.This can have significant advantages for the acceptance of both commercial and business aircraft.

[0012] The following terminology is explained:

[0013] An “aircraft” describes a vehicle that enables movement through the air, for example through lift in the ambient air. In particular, this can refer to an “airplane,” i.e. an aircraft with fixed wings. This aircraft has a “supporting structure,” which forms the essential structure of the aircraft and thus refers, for example, to the wings and fuselage. The “fuselage” refers to an essential, usually elongated structural part of the aircraft, which can accommodate personnel and passengers in particular. The fuselage has a “longitudinal axis,” which essentially describes the direction of flight of the aircraft. The longitudinal axis can deviate from an axis of movement, for example, by the amount of a so-called angle of attack.

[0014] A "fuel system" describes the essential components of an aircraft that serve to supply and deliver fuel to an engine. Such a fuel system can include tanks, lines, pumps, or even valves.

[0015] An "engine," which in the context of the present invention is particularly equipped as a jet engine, is typically a heat engine that provides propulsion, i.e., thrust, for the aircraft. The engines, together with other components such as propeller blades or the like, form the "drive" of the aircraft. In particular, so-called turboprop engines are mentioned in this context.

[0016] A first engine and a second engine have different "maximum thrusts," i.e., different maximum thrusts technically achievable by the engine within its operating limits. For this purpose, one of the engines can be configured for operation with different fuels, with jet engines in particular being relatively tolerant of different fuels.

[0017] The first fuel tank is designed to supply the propulsion with a “liquid fossil fuel”, such as kerosene or a comparable fuel.

[0018] A "cryogenic propellant" refers to a propellant that is cooled, in particular, below its liquefaction point or liquefaction temperature, and is usually gaseous at room temperature. When stored in a corresponding propellant tank, such a cryogenic propellant typically develops a pressure caused by the partial evaporation of components of the cryogenic propellant, so that the second propellant tank is designed to be "pressure-resistant," i.e., capable of absorbing the corresponding forces.

[0019] To ensure the cryogenic fuel is available within the aircraft in a compact and ready-to-use form, the second fuel tank is equipped with a cooling device for cooling the cryogenic fuel. In particular, the cooling device cools the fuel below a liquefaction point, thus preventing or reducing evaporation losses.

[0020] A "cooling device" is, for example, a technical device for generating low temperatures in the second fuel tank. Such a cooling device may include, in particular, pumps and valves. Furthermore, such a cooling device could also be provided in the form of, for example, a stored cold reservoir in the form of a cooled mass arranged on the second fuel, if this is appropriate.

[0021] In one embodiment, the second fuel tank has a substantially spherical shape. Such a spherical shape can best accommodate the corresponding internal pressures of a cryogenic fuel, and it also allows for easy integration of the second fuel tank, for example, into a round fuselage cross-section.

[0022] To ensure safe operation of the aircraft, even if cryogenic fuel evaporates within the second fuel tank or otherwise develops excess pressure, the second fuel tank is assigned a pressure relief valve. If a permissible maximum pressure in the second fuel tank is exceeded, the pressure relief valve allows the exceeded maximum pressure to escape. The exceeded maximum pressure can be diverted into the environment and / or into the first engine and / or the second engine to increase the respective engine power. For example, excess cryogenic fuel escaping due to exceeding the maximum pressure can be used to generate thrust.A pressure relief valve, which can be provided as needed, ensures that evaporation of the cryogenic fuel does not lead to overloads or structural damage, for example, if the tank structure is to be designed to be sufficiently lightweight. As mentioned above, a pressure relief valve can either discharge an exceeded maximum pressure into the environment or direct it to the respective engine.

[0023] A “pressure relief valve” is in particular a valve which, when a certain limit pressure or safety pressure defined as overpressure is reached or exceeded, causes and carries out the opening of the valve so that, for example, a technically permissible maximum pressure in the second fuel tank cannot be exceeded.

[0024] In this case, appropriate cryogenic fuel can be introduced at maximum pressure both into the environment and into one of the respective engines, so that, for example, fuel vapor resulting from the evaporation of cryogenic fuel can continue to be used to increase the respective engine power and thus to enhance the efficiency of the aircraft. In particular, appropriate vaporized cryogenic fuel can be used to increase the respective engine power, for example, within a combustion chamber and / or within an afterburner.

[0025] In one embodiment, a cross-section of the second fuel tank aligned substantially orthogonally to the longitudinal axis fills at least 80%, at least 85%, at least 90% and / or at least 95% of the fuselage cross-section, wherein in particular a tank structure of the second fuel tank at least partially forms a fuselage structure of the fuselage.

[0026] Such a "cross-section oriented orthogonally to the longitudinal axis" describes, in particular, the cross-section of the fuel tank, which is oriented perpendicular to the longitudinal axis of the aircraft, with the longitudinal axis of the aircraft then forming the normal of the cross-section. If, for example, 95% of the fuselage cross-section is filled by the cross-section of the fuel tank, the remaining 5% of the fuselage cross-section, which, for example, surrounds the fuel tank from a fuselage skin, can be used for fastening elements so that, for example, the fuel tank can be fitted and enclosed as a structural component in the fuselage cross-section. The same applies in this context to other of the above-mentioned percentages or intermediate values.

[0027] In particular, the “tank structure”, i.e. a force-absorbing structure of the tank, forms at least partially a hull structure of the hull, so that, for example, the second fuel tank is fitted into the hull structure as a “load-bearing component”.

[0028] In particular, the first engine and / or the first engine and the second engine are arranged in a rear section of the fuselage, wherein the second fuel tank is arranged in particular in the rear section of the fuselage and along the longitudinal axis in front of at least one of the engines.

[0029] In this way, noise emissions from the respective engines can be optimally kept away from the passenger cabin and cockpit, with the second fuel tank, for example, providing additional acoustic insulation. This allows for a particularly comfortable layout and additional noise insulation relative to the engines. For example, the second fuel tank can separate an engine section of the fuselage in a rear area from a passenger compartment located in the middle of the fuselage.

[0030] In a further embodiment, the first fuel tank is accommodated in the wing structure, in particular one wing or multiple wings of the aircraft. The first fuel tank, which is intended for the liquid fossil fuel, can be accommodated in particular on one wing or multiple wings of the aircraft. Liquid fossil fuel can be accommodated as a free-flowing fuel, for example, in wing tanks, as in previous aircraft.

[0031] In a further embodiment, the engine with the higher maximum thrust can be operated, at least temporarily, in particular switchably, with the cryogenic fuel.

[0032] This means that the engine with the higher maximum thrust can be operated, for example, in continuous operation with cryogenic fuel, whereby the engine with the higher maximum thrust has, in particular, sufficient maximum thrust to ensure, for example, a safe go-around or safe take-off of the aircraft on an existing runway length, even without the thrust of the engine with the lower maximum thrust.

[0033] In a further embodiment, the fuel system is assigned a switching device for switching a fuel supply for at least one of the engines between the liquid fossil fuel and the cryogenic fuel, or the fuel system has such a switching device.

[0034] With such a switching device, for example, the respective engine can be temporarily operated with cryogenic fuel if, for example, the flight situation or a corresponding flight phase allows this.

[0035] In a further embodiment, the cryogenic propellant comprises hydrogen or hydrogen with a purity of at least 99%.

[0036] Such a cryogenic fuel, which consists largely or predominantly of hydrogen, enables particularly low-emission aircraft operation. The use of hydrogen, particularly in a second fuel tank according to one or more of the above embodiments of the invention, ensures completely climate-neutral aircraft operation during some flight phases or during an entire flight.

[0037] A core concept of the invention is that, particularly in aircraft with engines arranged on or within the fuselage, a fuel tank for a cryogenic fuel is provided on or within the fuselage. The arrangement of the fuel tank for the cryogenic fuel on or, in particular, within the fuselage has several advantages. Firstly, the fuel tank, which is designed to be pressure-resistant for the cryogenic fuel, and a resulting corresponding weight can simultaneously be used as a static element within the fuselage. Secondly, a corresponding cryogenic fuel tank is usually provided with a pressure-adapted geometry, which can be arranged in a space-saving manner, in particular within the fuselage of an aircraft, in particular an airplane. Furthermore, the fuselage shape can be adapted to such a fuel tank with fewer aerodynamic restrictions than would be the case, for example, in the wings.

[0038] In particular, the second propellant tank, which is provided for the cryogenic propellant, has a cooling device for cooling the cryogenic propellant. Likewise, the second propellant tank can have a substantially spherical shape.

[0039]

[0040]

[0041] The invention will be explained in more detail below using exemplary embodiments. Figure 1 shows a partially sectioned side view of a business aircraft, and Figure 2 shows the business aircraft of Figure 1 in a schematic plan view.

[0042] A business aircraft 101 has a fuselage structure 103. The fuselage structure 103 serves as part of the wing structure of the business aircraft 101 and has windows 105, shown as examples, which serve as cockpit windows and define a passenger compartment 106 in the central region of the fuselage 103. The business aircraft 101 is designed as a low-wing aircraft with a conventional tail unit in a typical configuration with a vertical stabilizer 111, a horizontal stabilizer 113, and a wing 115. The vertical stabilizer 111 and the horizontal stabilizer 113 are arranged at a tail 107; a tail configuration in a so-called canard arrangement can also be used in the area of ​​a nose 109.

[0043] The wing 115 has lift aids 117, such as landing flaps, to increase lift in certain flight situations. A tank volume 116 for accommodating kerosene as fuel for the business aircraft 101 is arranged within the wings 115. Furthermore, the business aircraft 101 has a main landing gear 121 and a nose landing gear 123, each of which is retractable.

[0044] Two engines are arranged in the tail 107: an engine 151 with an air inlet 153 and a nozzle 155, and an engine 161 with an air inlet 163 and a nozzle 165. Engines 151 and 161 are turbofan engines that operate according to the principle of a gas turbine with an additional turbofan (not shown in detail). To do so, the engines draw in air through the corresponding air inlets 153 and 163, increase the energy contained in the air through combustion in a respective combustion chamber (not shown), and expel correspondingly hot and accelerated gases together with the accelerated air masses of the respective turbofan through the respective nozzles 155 and 165, thus generating thrust for the business aircraft 101 and enabling it to accelerate. Engine 151 has a lower maximum thrust, whereas engine 161 has a comparatively higher maximum thrust.Thus, engines 151 and 161 are designed with different maximum power outputs. Engine 161 is designed for operation with multiple fuels, in particular kerosene and hydrogen. Thus, either engine 151, with its lower maximum thrust, can be used to operate the business aircraft 101 efficiently and safely with kerosene, particularly during cruise flight, even if, for example, engine 161 is subject to a malfunction. Engine 161, with its higher thrust compared to engine 151, is used to provide sufficient performance of the business aircraft 101, for example, in hot-and-high conditions and / or for particularly short takeoff and landing distances. Likewise, engine 161 can ensure a sustainable flight condition when operated with hydrogen as fuel.

[0045] The maximum thrust of engine 151 is selected so that the power required for the total weight of the aircraft is available in accordance with certification to ensure that takeoff abort is no longer possible after a so-called decision speed in order to ensure a safe climb of the business aircraft 101.

[0046] A spherical tank 171 is installed in the tail 107 of the business aircraft 101, in front of the engines 151 and 161. The spherical tank 171 has a wall 173, which mechanically supports the fuselage 103 in a support section 175 and a support section 177. The spherical tank 171 is designed to be pressure-resistant and contains hydrogen as fuel in its tank volume 179. For this purpose, the spherical tank 171 has a cooling system (not shown). A switching unit 141 controls the fuel (kerosene) taken from the tank volume 116 on a wing 115 as well as the hydrogen taken from the spherical tank 171 and supplies the corresponding fuel quantities to the engines 151 and 161 (not shown in detail). Furthermore, a vent 143 is connected to the switching unit 141, which directs evaporating hydrogen from the tank volume 179 to the outside.Likewise, the vent 143 can be relocated towards the engines 151 and 161 so that corresponding evaporating hydrogen can be used to generate additional thrust.

[0002] List of reference symbols 101 Business aircraft 103 Fuselage structure 105 Window 106 Passenger compartment 107 Tail 109 Nose 111 Vertical stabilizer 113 Horizontal stabilizer 115 Wing 116 Tank volume 117 Lift aids 121 Main landing gear 123 Nose landing gear 141 Switch unit 143 Ventilation 151 Engine 153 Air inlet 155 Nozzle 161 Engine 163 Air inlet 165 Nozzle 171 Spherical tank 173 Wall 175 Support section 177 Support section 179 Tank volume 183 Wingspan 191 Longitudinal axis 192 Center

Claims

Patent claims:

1. Aircraft (101), in particular an airplane (101), with a supporting structure (115), a fuselage (103) with a longitudinal axis (191), a fuel system (116, 141, 171) and at least two engines (151, 161) of a drive (151, 161) assigned to the fuselage (103), in particular arranged in the fuselage (103), wherein a first engine (151) and a second engine (161) have different maximum thrusts from one another and at least one of the engines (151, 161) is designed for operation with different fuels, wherein the fuel system (116, 141, 171) has a first fuel tank (116) for supplying the drive (151, 161) with a liquid fossil fuel, characterized in that the fuel system (116, 141, 171) has a second fuel tank (171) for supplying the drive (151, 161) with a cryogenic fuel,wherein the second fuel tank (171) is designed to be pressure-resistant for holding the cryogenic fuel and is accommodated in the fuselage (103).

2. Aircraft according to claim 1, characterized in that a cooling device for cooling the cryogenic fuel is assigned to the second fuel tank (171).

3. Aircraft according to claim 1 or 2, characterized in that the second fuel tank (171) has a substantially spherical shape.

4. Aircraft according to one of the preceding claims, characterized in that a pressure relief valve (141) is assigned to the second fuel tank (171), wherein the pressure relief valve (141) is activated when a permissible, Maximum pressure in the second fuel tank (171) allows the exceeded maximum pressure to escape, wherein the exceeded maximum pressure is released into the environment and / or into the first engine (151) and / or into the second engine (161) to increase a respective engine power.

5. Aircraft according to one of the preceding claims, characterized in that a cross-section of the second fuel tank (171) oriented substantially orthogonally to the longitudinal axis (191) fills at least 80%, at least 85%, at least 90%, and / or at least 95% of the fuselage cross-section, wherein in particular a tank structure (173) of the second fuel tank (171) at least partially forms a fuselage structure (175, 177) of the fuselage (103).Aircraft according to one of the preceding claims, characterized in that the first engine (151) and / or the second engine (161) are arranged in a rear section (107) of the fuselage (103), wherein the second fuel tank (171) is arranged in particular in the rear section (107) of the fuselage and along the longitudinal axis (191) in front of at least one of the engines (151, 161).

7. Aircraft according to one of the preceding claims, characterized in that the first fuel tank (116) is accommodated in the supporting structure (115), in particular in one wing (115) or in several wings (115) of the aircraft.

8. Aircraft according to one of the preceding claims, characterized in that the engine (161) with the higher maximum thrust can be operated with the cryogenic fuel, at least temporarily, in particular switchably.

9. Aircraft according to one of the preceding claims, characterized in that the fuel system (116, 141, 171) comprises a switching device (141) for switching a fuel supply for at least one of the engines (151, 161) between the liquid fossil fuel and the cryogenic fuel.

10. Aircraft according to one of the preceding claims, characterized in that the cryogenic fuel comprises hydrogen or is hydrogen with a purity of at least 99%.

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