Engine for a VTOL aircraft and VTOL aircraft

Abstract

The present application relates to an engine (10) for a VTOL aircraft and a VTOL aircraft having such an engine (10). The engine (10) according to the invention has a tubular housing (11) which is designed to be mounted on the aircraft so as to be rotatable about a rotation axis (12), and a drive designed to accelerate an air mass flow (20) through the housing (11) from an inlet (11a) to an outlet nozzle (11b) of the housing (11). Furthermore, the engine according to the invention has at least one flap (13) which is rotatably mounted on the engine (10), in particular on the housing (11), by means of at least one joint (14), and which has an outlet nozzle diameter (D AD ) of the outlet nozzle (11b). According to the invention, a spring element (15) is further provided, which is connected to the at least one flap (13) and is prestressed and arranged such that the outlet nozzle diameter (D AD) of the outlet nozzle (11b) is minimal in the inactive state of the engine (10).

Description

[0001] This application relates to a tiltable engine for a VTOL aircraft and a VTOL aircraft with such an engine. VTOL aircraft are aircraft (not helicopters) capable of vertical takeoff and landing. VTOL aircraft also include STOL aircraft, which, due to the vertical thrust generated by their engines, only require short runways (short takeoff and landing).

[0002] For hovering, i.e., operating conditions in which the vehicle's longitudinal speed is insufficient to generate the aircraft's corresponding lift, these VTOL aircraft have either fixed thrust and lift engines capable of generating the corresponding vertical thrust, or pivoting engines capable of being rotated by at least 90 degrees around a horizontal axis. This allows the same engine to generate both vertical thrust and horizontal thrust. The present invention relates to the second type of engine described.

[0003] An engine is defined as any type of thrust-generating element with a substantially tubular housing, regardless of its thrust-generating function. Thus, the term encompasses, for example, a ducted propeller as well as a jet engine or its subtypes. An engine is therefore simply an element through which a mass flow is directed by means of a drive. The term "drive" is to be understood independently of the technology; it simply refers to an element capable of generating such a mass flow (air mass flow) through the engine.

[0004] Such pivoting or tilting engines must therefore operate efficiently in different operating modes depending on their use, i.e., both in hover and in horizontal cruise flight, which is the operating mode of conventional commercial aircraft. However, different operating modes require different geometric specifications for the engine casing. For the purposes of the application, the casing is understood to be the element of the engine whose interior defines a flow channel through which an air mass flow passes as it flows through the engine from an inlet to an outlet.

[0005] Various engine designs are known from the prior art. Document EP 2 336 022 A2 discloses a ducted propeller of a VTOL having cross-section change means at the inlet and / or outlet, wherein the cross-section change means comprise at least one cross-section change element and an actuator for actively adjusting the cross-section change element.

[0006] Document EP 3 176 078 B1 describes a ducted propeller of a VTOL having a plurality of circumferentially distributed flap-like cross-section changing elements at the outlet, wherein the cross-section changing elements are actively adjustable by an actuator.

[0007] Document EP 3 909 851 A1 also describes an adjustable duct propeller, wherein the duct propeller can be adjusted between two different positions by means of an actuator and an adjustment kinematics and the outlet cross-section can be adjusted.

[0008] From document KR 102549149 B1, a ducted propeller with adjustable inlet cross-section is known, wherein the inlet cross-section is actively adjustable by an actuator.

[0009] Document EP 3 722 210 B1 also describes a ducted propeller of a VTOL in which an outlet cross-section can be changed by cross-section changing elements that are actively adjustable by an actuator.

[0010] Against the background of the described prior art, the object of the present invention is to provide an engine for a VTOL aircraft that can be operated energy-efficiently and easily in various operating modes. Likewise, the object of the present invention is to provide a corresponding aircraft with an engine according to the invention.

[0011] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are contained in the subclaims.

[0012] The engine according to the invention comprises a tubular housing, which is designed to be mounted on the aircraft so as to be rotatable about a rotation axis, and a drive designed to accelerate an air mass flow through the housing from an inlet to an outlet nozzle of the housing. A tubular housing is defined as a housing with a round cross-section, wherein the cross-section can vary along a longitudinal direction of the tubular housing. A flow channel defined by the housing, through which the mass flow is guided, can also have different cross-sections.

[0013] Furthermore, the engine according to the invention has at least one flap, which is rotatably attached to the engine, in particular to the housing, by means of at least one joint, and which defines an outlet nozzle diameter of the outlet nozzle. Consequently, the outlet nozzle diameter can be influenced by the position of the at least one flap, which is to be understood as meaning that the cross-sectional area in the longitudinal direction at the level of the outlet nozzle is subsequently influenced by the position of the flap. According to the invention, a spring element is also provided, which is connected to the at least one flap and is prestressed and arranged such that the outlet nozzle diameter of the outlet nozzle is minimal when the engine is inactive.The inactive state describes the operating state of the engine in which there is no mass flow through the casing from inlet to exhaust nozzle and the engine drive is therefore switched off and the aircraft is on the ground.

[0014] The inventive design of the engine enables variable adjustment of the flap position and thus of the exhaust nozzle diameter during operation of an aircraft, without the need to add additional energy, for example via an actuator that adjusts the flap position. This can achieve advantages in terms of control, weight and complexity and thus costs of the overall system. If the mass flow is increased, it is dammed upstream of the at least one flap and thus the exhaust nozzle. The resulting dynamic pressure presses against the flap with a force directed in such a way that the exhaust nozzle diameter is increased and the dynamic pressure can escape more easily from the housing. The mass flow thus induces a force on the at least one flap, which acts counter to the force exerted on the flap by the preloaded spring element.If the force exerted by the mass flow on the flap exceeds the force exerted by the spring element, the flap moves in such a way that the outlet nozzle diameter is increased until a static equilibrium is established between the force exerted by the spring element and the force exerted by the mass flow on the flap.

[0015] In other words: if the mass flow conveyed through the casing by the engine increases, the exhaust nozzle diameter also increases and with it the cross-section of the casing at the level of the exhaust nozzle in the longitudinal direction of the engine. The thrust requirements are very different between hover operating modes, i.e. when thrust is at least partially in the vertical direction, and cruise operating modes, i.e. when thrust is in the direction of the longitudinal axis of the aircraft (horizontal direction). Hover operating mode, in which there is no horizontal movement of the aircraft, is the most demanding and therefore the mass flow is the greatest. In operating modes that only have horizontal thrust, greater efficiency can be achieved by reducing the exhaust nozzle diameter.If the force exerted by the mass flow on the at least one flap decreases to such an extent that the force exerted by the spring element on the at least one flap is greater, the outlet nozzle diameter decreases again and a new static equilibrium is established due to the mass flow.

[0016] The spring element is preferably designed as a spiral spring. This represents a simple way of forming a spring element, which offers particular advantages in terms of manufacturing and design effort, as well as costs. An element designed as a spiral spring can also be manufactured from materials that are particularly heat- and corrosion-resistant and have a wide operating temperature range. The spring element is particularly preferably made of a metal alloy. However, other types of spring elements are conceivable, such as a spiral spring, which is preferably arranged at a pivot point of the at least one flap.

[0017] In a further advantageous embodiment of the invention of the engine according to the invention, the spring stiffness and / or the operating range of the at least one spring element is designed such that the exhaust nozzle has a defined cruising diameter optimized with regard to energy consumption in a defined cruise operating state of the engine and / or a defined hovering diameter optimized with regard to the engine's energy consumption in a defined hovering state. The invention can thus be designed for the two most frequently used operating points. A particularly suitable defined cruising state for this purpose is the operating state which, in conventional aircraft without pivoting engines, is also defined as the optimized operating state during cruise flight.The operating state that results in a purely vertical movement of the aircraft is particularly suitable as a defined hovering state.

[0018] A further preferred embodiment of the invention is one in which the at least one spring element is arranged between the at least one flap and the housing, and in particular is clamped between these components and supported between the flap and the housing. Thus, the spring element can be designed as a compression spring element.

[0019] Another advantageous embodiment of the invention is one in which the engine has several flaps, which are arranged on the housing, particularly evenly distributed in the circumferential direction, and each is preloaded identically by a spring element. This embodiment offers advantages in terms of structural design and is also easy to manufacture, which has a particularly positive effect on the cost of the engine.

[0020] Another advantageous embodiment of the invention is one in which the at least one flap is formed from different interlocking flap parts. Analogously, a configuration having a plurality of flaps that interlock is also preferable. Interlocking flaps or flap parts are to be understood as flaps or flap parts that are operatively connected to one another in some form, for example mechanically, so that a movement of the flap parts or flaps can only be achieved when all flap parts or flaps are moved. Such configurations have the advantage that the movement of the flap parts or flaps takes place synchronously. It is also conceivable that only one spring element is provided for the pretension of one flap part or one flap.However, when designing the spring element, the resistance of all flap parts against the mass flow must be taken into account.

[0021] In a preferred embodiment of the invention, a system comprising multiple spring elements is provided for positioning just one flap. This allows, if required, different spring hardnesses and operating ranges of the system to be enabled for different operating modes. This is particularly advantageous in that non-linear curves between the different positions of the flaps and thus the different outlet nozzle diameters can be taken into account. If, for example, during the transition from a hover operating mode to a cruise operating mode, the outlet nozzle diameter is to initially increase slowly and then a larger change in diameter is to take place with only a small increase in the mass flow and thus in the force caused by the mass flow, this can be achieved, for example, using a system comprising multiple spring elements with different characteristics.

[0022] The aircraft according to the invention has an engine according to the invention.

[0023] Advantageous aspects and embodiments of the invention are explained in more detail with the aid of the accompanying figures. They show: Fig. 1a shows a schematic illustration of an embodiment of an engine 10 according to the invention in a hovering flight phase in a side view Fig. 1b shows the embodiment of Fig. 1a in a rear view in the longitudinal direction of the engine 10 Fig. 2a shows a schematic illustration of the embodiment according to Fig. 1a and Fig. 1b in a cruise flight operation phase in a side view Fig. 2b shows the embodiment of Fig. 2b in a rear view in the longitudinal direction of the engine 10

[0024] The Fig. 1a, Fig. 1b, Fig. 2a and Fig. 2b all show schematic illustrations of an engine 10 according to the invention in the same embodiment. To avoid duplicate descriptions, the embodiment will therefore be described only with reference to Fig. 1a is explained in full. Regarding the remaining figures, only the existing differences between the views presented will be discussed.

[0025] Fig. 1a shows a schematic illustration of the engine 10 in a side view, wherein the engine 10 is cut open along its longitudinal axis. The longitudinal axis is defined by the direction in which the engine 10 can exert thrust. The engine 10 is defined by a housing 11, which is aligned along the longitudinal direction and has a tubular basic shape, wherein the cross-section along the longitudinal axis of a channel defined by the housing 11 has a varying diameter. In the channel, which guides a mass flow 20 from an inlet 11a to an outlet nozzle 11b, which is arranged on a side of the channel and thus of the housing 11 opposite the inlet 11a, a drive (not shown) is provided, which generates the mass flow 20.Various technologies known in the prior art can be used as propulsion, which need not be discussed further with regard to the invention. The engine 10 is mounted on an aircraft (not shown) so that it can rotate about a horizontal axis of rotation 12.

[0026] Furthermore, at the level of the outlet nozzle 11b, several flaps 13 are arranged in the circumferential direction of the outlet nozzle 11b, which have an outlet nozzle diameter D AD The outlet nozzle diameter D ADis defined by the flaps 13. These are pivotally connected to the housing 11 via several joints 14. Spring elements 15, which are exemplified by spiral springs, are arranged between the flaps 13 and the housing 11. The spring elements 15 are arranged between the housing 11 and the flaps 13 and are preloaded in such a way that they rotate the flaps 13 around the joints 14, thus positioning the flaps 13 as a resistance in the mass flow 20.

[0027] Fig. 1b shows the exact same embodiment in the same operating phase (operating state), whereby the thrust by the engine 10 in the illustrated operating phase runs in a vertical direction. Fig. 1b, which shows the engine 10 from below, the thrust thus acts from the plane of the drawing into Fig. 1b out towards the viewer.

[0028] The mass flow 20 is due to the hovering operating condition shown, especially in comparison to the Fig. 2a and Fig. 2b. As a result, the flaps 13 are pushed radially outward against the forces acting on the flaps 13 by the spring elements 15. This results in an outlet nozzle diameter D AD to a comparatively large hover diameter D S The position of the flaps 13 results from a static equilibrium between a force acting on the flaps 13 due to the mass flow 20 and a force acting on the flaps 13 due to the spring elements 15. Thus, at a static mass flow 20, the position of the flaps 13 does not change.

[0029] Fig. 2a and Fig. 2b, however, show the engine 10 according to the invention in a cruise phase / cruise operating state. This is characterized by the engine 10 being rotated 90 degrees around the rotation axis 12, and thus the thrust is generated in a horizontal direction. The mass flow 20 is significantly lower in the cruise phase than in the hover phase (see FIG. Fig. 1a, Fig. 1b), as indicated by the smaller arrow in Fig. 2a is illustrated.

[0030] This creates a new static equilibrium of the forces acting on the flaps 13 caused by the mass flow 20 and the forces of the spring elements 15. In this equilibrium, the outlet nozzle diameter D AD significantly reduced and results in a cruising diameter D R , which is correspondingly smaller than the hover diameter D S , as in particular Fig. 2b. This determines the outlet nozzle diameter DAD automatically adapted to the corresponding operating phase, i.e. hovering or cruising flight, without the use of an actuator. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] EP 2 336 022 A2

[0005] EP 3 176 078 B1

[0006] EP 3 909 851 A1

[0007] KR 102549149 B1

[0008] EP 3 722 210 B1

[0009]

Claims

[1] Engine (10) for a VTOL aircraft comprising a tubular housing (11) which is designed to be rotatably mounted on the aircraft about a rotation axis (12), a drive designed to accelerate an air mass flow (20) through the housing (11) from an inlet (11a) to an outlet nozzle (11b), at least one flap (13) which is rotatably attached to the housing (11) by means of at least one joint (14) and which has an outlet nozzle diameter (D AD ) of the outlet nozzle (11b), at least one spring element (15) which is connected to the at least one flap (13) and is prestressed and arranged such that the outlet nozzle diameter (D AD ) of the outlet nozzle (11b) is minimal in the inactive state of the engine (10). [2] Engine (10) according to the preceding claim, wherein the spring element (15) is designed as a spiral spring. [3] Engine (10) according to one of the preceding claims, wherein the spring hardness and / or the working range of the at least one spring element (15) are designed such that the outlet nozzle (11b) in a defined cruise operating state of the engine (10) has a defined cruise diameter (D R ) and / or in a defined hovering state, a defined hovering diameter (D S ). [4] Engine (10) according to one of the preceding claims, wherein the at least one spring element (15) is arranged between the at least one flap (13) and the housing (11). [5] Engine (10) according to one of the preceding claims, wherein the engine (10) has a plurality of flaps (13) which are arranged on the housing (11) in particular in a uniformly distributed manner in the circumferential direction and are each prestressed identically by a spring element (15). [6] Engine (10) according to one of the preceding claims, wherein the at least one flap (13) is formed from different interlocking flap parts. [7] Engine (10) according to one of the preceding claims, wherein a system of several spring elements (13) is provided for positioning only one flap (13). [8] Aircraft comprising at least one engine (10) according to one of the preceding claims.

Images