Aircraft having a refuelling connection for refuelling with a cryogenic fuel

Abstract

The invention relates to an aircraft having a refuelling connection which is fluidically connected to a tank arranged in the aircraft, wherein the refuelling connection and the tank are designed to receive a cryogenic fuel, wherein the refuelling connection has a pipe section (7) specially designed for conducting a cryogenic fuel and / or a coupling (25) which is fixed to an aircraft-fixed structure, wherein, in order to fix the pipe section (7) and / or the coupling (25), a first half-shell (17) and a second half-shell (18) are provided, wherein the first half-shell (17) is fixed to the aircraft-fixed structure, and wherein the second half-shell (18) is connected to the first half-shell (17) by an elastic clamping connection so as to exert a clamping force on the pipe section (7) and / or the coupling (25), and is guided so as to be displaceable relative to the aircraft-fixed structure in a linear guide (26).

Description

[0001] Lufthansa Technik AG, 22335 Hamburg, DE

[0002] Aircraft with a refueling port for refueling with cryogenic fuel

[0003] The present invention relates to an aircraft with a refueling port for refueling with a cryogenic fuel having the features of the preamble of claim 1.

[0004] Aircraft powered by kerosene usually have their tanks located in the wings, with the refueling ports on the underside of the wings, allowing the aircraft to be refueled from below using a tanker truck and a hose.

[0005] The use of cryogenic fuels, such as liquid hydrogen, presents additional challenges. While the energy density of liquid hydrogen per unit mass is higher than that of kerosene, its energy density per unit volume is four times lower. To compensate for this lower volumetric energy density, hydrogen is stored and refueled in liquid form in aviation, where volume is a critical factor. This liquid state is achieved at a temperature of -253 °C, which corresponds to the boiling point of hydrogen.

[0006] To cool the cryogenic fuel to this low temperature in an energy-efficient manner, a spherical tank would be the ideal shape. However, a spherical tank is not practical in terms of the overall architecture of the aircraft's wings, as it would poorly utilize the available space within the wing, or necessitate a correspondingly small tank. Therefore, other tank shapes and types are required, where, for energy-efficient cooling, the ratio of the external surface area to the tank's volume should be as small as possible. For example, cylindrical tanks with a circular cross-section are suitable.

[0007] Furthermore, refueling the aircraft with cryogenic fuel, such as hydrogen, requires appropriate insulation of the refueling lines and interfaces. An LH2 coupling has proven effective for this purpose, featuring a specifically designed insulation concept with various O-rings and thus specifically designed for a pressure line carrying a cryogenic fluid. Due to the very low temperatures and the large temperature differences with the surrounding environment, the lines, the coupling itself, and the interfaces are subjected to very large differential thermal expansions. These differential expansions can consequently lead to correspondingly high material stresses if the material is not sufficiently confined to accommodate these differential expansions.

[0008] Against this background, the invention is based on the task of providing an aircraft with a refueling port that is designed for improved refueling with a cryogenic fuel.

[0009] To solve the problem, an aircraft with the features of claim 1 is proposed. Further preferred developments can be found in the dependent claims, the figures, and the accompanying description. According to the basic idea of ​​the invention, it is proposed that a first half-shell and a second half-shell are provided for fixing the line and / or the coupling, and that the first half-shell is fixed to the aircraft-mounted structure, and that the second half-shell is connected to the first half-shell by an elastic clamping connection, exerting a clamping force on the line and / or the coupling, and is guided slidably in a linear guide relative to the aircraft-mounted structure.

[0010] The first half-shell essentially forms an aircraft-tight bearing to which the pipe and / or coupling is fixed. To fix the pipe and / or coupling relative to the first half-shell, the second half-shell is provided. This second half-shell is specifically designed to compensate for thermal expansion or contraction of the pipe or coupling through its elastic clamping connection. It is specifically designed to allow elastic movement relative to the first half-shell without reducing the clamping force to zero or increasing it to such an extent that the clamping connection components or the half-shells are mechanically damaged. The elasticity of the clamping connection thus serves to create a degree of mobility similar to that of a floating bearing, while the pipe or coupling remains fixed to the first half-shell via the clamping connection.To prevent the movement of the second half-shell from being uncontrolled, a guide is provided for the second half-shell. The shape and arrangement of this guide dictate its movement relative to the aircraft-fixed structure. This is a linear guide, ensuring that the second half-shell moves linearly and in a straight line during thermal expansion or contraction. Furthermore, the guide absorbs additional transverse forces acting on the second half-shell, thus relieving the elastic clamping connection between the first and second half-shells to this extent.

[0011] It is further proposed that the linear guidance of the second half-shell and the direction of elasticity of the elastic clamping connection be aligned. This proposed development ensures that the mobility of the second half-shell relative to the first half-shell, intentionally created by the elastic clamping connection, is not restricted or inhibited by the guidance.

[0012] It is further proposed that the second half-shell be connected to the first half-shell via the elastic clamping connection in a manner that allows for movement perpendicular to the direction of elasticity. This additional sliding connection between the second half-shell and the first half-shell allows the second half-shell to perform minor movements perpendicular to the clamping connection, thus compensating for thermal expansion in this direction as well.

[0013] It is further proposed that the elastic clamping connection be achieved using expansion bolts. Expansion bolts have the advantage of a particularly large elastic range due to their long central expansion section, allowing them to accommodate elastic expansion movements without themselves undergoing plastic deformation.

[0014] It is further proposed that the expansion bolts be supported on the first and / or second half-shell via spring elements. These spring elements create a two-spring system acting in series, whose spring characteristic allows for additional spring movements of the second half-shell relative to the first, without requiring the elastic clamping device in the form of the expansion bolts to perform any spring movements.

[0015] It is particularly preferred that the spring elements are formed by disc springs. Disc springs are characterized by a very compact design combined with a very high load-bearing capacity, so that very large force fluctuations can be compensated before the elastic clamping device itself is elastically deformed.

[0016] The invention is explained below with reference to preferred embodiments and the accompanying figures.

[0017] Fig. 1 shows a cross-section of a section of the hull with a refueling port, and

[0018] Fig. 2A-C shows an oblique view, a rear view and a side view of the refueling port, and

[0019] Fig. 3A-E shows an elastic clamping device in various enlarged views and two enlarged sectional views of the clamping device.

[0020] Figure 1 shows a section of the fuselage 1 of an aircraft. The fuselage 1 is the central, usually tubular, middle section of the aircraft, which is oriented in the direction of flight and serves to accommodate passenger seats, luggage, cargo, the cockpit unit, and / or the aircraft's central technical systems in general, and therefore has a correspondingly large cavity whose shape is adapted to its function. The wings of the aircraft, or in the case of a single-wing aircraft, the wing itself, are attached to the fuselage 1. These wings serve to generate lift for the aircraft and are therefore aerodynamically shaped.

[0021] In the hull 1, a tank (not shown) is provided, which is cylindrical with a circular cross-section for the purpose of energy-optimized cooling with the largest possible volume and serves to hold liquid hydrogen, i.e., a cryogenic fuel, at a temperature of less than minus 253 °C.

[0022] A refueling port is provided on the underside of the fuselage 1. This port is formed by a connecting part 3 with a centrally arranged connection 5 in the form of an externally inserted coupling 25, as shown in Figure 2B, formed by an LH2 coupling piece. The connecting part 3 is attached to the inside of the fuselage 1 in the region of an edge of a cutout 16 in the fuselage 1 by a first edge section 10, e.g., via a weld or rivet connection. Furthermore, a retaining plate 2 is provided, which is also attached to the opposite edge of the cutout 16 on the inside of the fuselage 1 by a first edge section 11, likewise via a weld or rivet connection. The cutout 16 in the fuselage 1 is rectangular, and the connecting part 3 and the retaining plate 2 are attached to two opposite edges of the cutout 16.

[0023] The connecting part 3 and the retaining plate 2 are connected to each other at an angle C of 90 degrees, i.e., at right angles, via their second edge sections 12 and 13, which are arranged at opposite ends of the connecting part 3 and the retaining plate 2 with respect to the first edge sections 10 and 11. The connecting part 3 is attached to the edge of the cutout with its first edge section 10 such that the connecting part 3 is oriented at an angle A to an imaginary extension of the fuselage 1 within the cutout. The retaining plate 2 is attached to the edge of the cutout with its first edge section 11 such that the retaining plate 2 is oriented at an angle B to an imaginary extension of the fuselage 1 within the cutout.

[0024] The angle A between the connecting part 3 and the imaginary extension of the fuselage 1 in the cutout 16 is larger than the opposite angle B between the retaining plate 2 and the imaginary extension of the fuselage 1 in the cutout 16. Furthermore, the retaining plate 2, from the first edge section 11 to the second edge section 13, has a greater length than the connecting part 3, from the first edge section 10 to the second edge section 12.

[0025] This geometry results in a insertion direction for the coupling piece at connection 5 in the X-direction, in this case orthogonal to the plate-shaped connection part 3, which is arranged at an angle D between 0 degrees and 90 degrees to a horizontal plane H of the aircraft when the aircraft is on the ground. This allows the coupling piece of the LH2 coupling to be inserted obliquely from above into the refueling port located on the underside of the fuselage 1, thus reducing the probability of embrittlement of the O-rings in the LH2 coupling piece and the associated probability of failure. Figure 2A shows the same refueling port on the fuselage 1 from the perspective of the aircraft's interior.

[0026] The connecting part 3 is additionally stiffened in its connection by two stiffening ribs 8 and 9 and connected to the holding part 2.

[0027] The connection 5 of the connecting part 3 is designed in the direction of the interior of the aircraft in the form of a short cylindrical extension of a coupling 25, on which a pipe section 7 of a tank not shown, located in the interior, is attached, as can be seen in Fig. 2B.

[0028] Connection part 3 is specifically designed here as a refueling connection for a coupling piece of an LH2 coupling for cryogenically cooled liquid hydrogen via connection 5 in the form of coupling 25. If refueling with a different cryogenic propellant is intended, connection 5 can also be specially designed for this purpose. Furthermore, connection part 3 can also be provided with other service connections for power supply, water drainage, and / or water supply, and the like.

[0029] The refueling port is located in the lower half of the fuselage 1, whereby the provided connection part 3 and the orientation of the port 5 nevertheless allow the coupling piece to be inserted from above. The orientation of the coupling piece's feed direction can be individually configured by the orientation of connection part 3 and port 5, whereby the feed direction is decoupled from the orientation of the fuselage 1 and the local fuselage shape. This inventive solution enables the aircraft to be refueled in a direction optimized for service and handling.

[0030] Furthermore, the right-angled connection of the retaining plate 2 and the connecting part 3 at angle C does not restrict the operating range for supplying the coupling piece and contacting the coupling piece with the connection 5, and the enlargement of the cutout 16 in the body 1 can be limited to a minimum. An angle C greater than 90 degrees would not increase the operating range but would only increase the cutout 16 in the body 1, whereas an angle C less than 90 degrees would reduce the cutout 16 but would also reduce the operating range for accessing the coupling piece. Therefore, the proposed angle C of 90 degrees at the connection of the second edge sections 12 and 13 of the connecting part 3 and the retaining plate 2 is the optimum with regard to fulfilling the criteria.

[0031] An elastic clamping device 6 is provided for connecting the pipe section 7 and the coupling 25, which is shown enlarged in Figures 3A-3C. The elastic clamping device 6 comprises a first semi-ring-shaped half-shell 17 and a second semi-ring-shaped half-shell 18, which clamp and connect the pipe section 7 and the coupling 25, respectively, with an axially directed semi-ring-shaped section. The first half-shell 17 also has a semi-ring-shaped, radially projecting, disc-shaped collar 28, by means of which the first half-shell 17 is fastened to the connecting part 3 of the fuselage 1 by several fastening screws 19, so that the first half-shell 17 forms an aircraft-resistant abutment. The second half-shell 18 is identical in its basic structure to the first half-shell 17 and also has a radially projecting, disc-shaped collar 28.

[0032] The first half-shell 17 and the second half-shell 18 each have a laterally projecting axial flange, via which the two half-shells 17 and 18 are clamped together by means of two expansion bolts 14, 15, 20, 21 on the projecting flanges. The tensile forces acting in the expansion bolts 14, 15, 20, 21 are the cause of the clamping force applied to the coupling 25 and the pipe section 7.

[0033] A longitudinal web 22 is also attached to the connecting part 3, on which the second half-shell 18 is guided slidably relative to the connecting part 3 and thus relative to the fuselage 1 of the aircraft as such via a dovetail guide 23 (shown enlarged in Fig. 3D). The dovetail guide 23 is aligned in the same direction as the longitudinal direction of the expansion bolts 14, 15, 20, 21. Furthermore, spring elements 24 in the form of disc springs are provided between the expansion bolts 14, 15, 20, 21 or their nuts and the flanges 27, so that the expansion bolts 14, 15, 20, 21, in addition to their own elastic properties, are supported on the flanges in a series arrangement via the disc springs.Furthermore, the holes in the flanges 27 can be designed as elongated openings, which are oriented such that the longer longitudinal axes are orthogonal to the longitudinal axes of the expansion bolts 14, 15, 20, 21 and orthogonal to a central axis of the pipe section 7 or the coupling 25.

[0034] The elastic clamping device 6 is thus based on the following basic elements. The first half-shell 17 is fixed to the aircraft and forms the stationary abutment for the mounting of the pipe section 7 and the coupling 25. The expansion bolts

[0035] Parts 14, 15, 20, and 21 serve to apply the required clamping force to the pipe section 7 and / or the coupling 25 for fixation. This is due to the design of the screws as expansion bolts.

[0036] 14, 15, 20, 21 are deliberately designed to allow expansion movements, i.e., elongation, within certain limits, in which the distance between the two half-shells 17 and 18 is increased without themselves being destroyed or plastically deformed. In this way, the expansion screws exert

[0037] 14, 15, 20, 21, even when elongated, the required clamping force continues to be exerted on the pipe section 7 and the coupling 25 to fix them in place, whereby the pipe section 7 and the coupling 25 can simultaneously expand or contract with temperature changes. Thus, the elastic clamping device 6 is specifically designed to enable a reliable hold on the pipe section 7 and the coupling 25 within a defined range of holding force, even under large temperature changes during the refueling of the aircraft with liquid hydrogen.

[0038] Furthermore, the spring elements 24 provide an additional spring option arranged in series with the expansion bolts 14, 15, 20, 21, with a different spring characteristic than the expansion bolts 14, 15, 20, 21. This allows, for example, small spring movements of the second half-shell 18 below those required for the elastic spring movement of the expansion bolts 14, 15, 20, 21, in order to permit smaller expansions at lower temperature changes. Additionally, the elongated holes in the flanges 27 allow the first half-shell 17 and the second half-shell 18 to perform slight relative movements towards their radial outer surfaces, thus also accommodating temperature-induced deformations in this direction.In general, the inventive idea is based on enabling a secure hold by means of a deliberately spring-elastic fastening of the pipe section 7 and the coupling 25, while simultaneously applying a permanently applied clamping force. This fastening is also designed to move with thermal expansion and contraction, so that stresses in the interacting parts can at least be reduced during thermal expansion. The aircraft-resistant abutment created by the first half-shell 17 is of particular importance, as it forms a deliberately fixed reference point even during thermal expansion and contraction.

[0039] 1 Hull

[0040] 2 Mounting plate

[0041] 3 Connection part

[0042] 4 cavities

[0043] 5 connection

[0044] 6 clamping element

[0045] 7 pipe sections

[0046] 8 stiffening rib

[0047] 9 stiffening rib

[0048] 10 First marginal section

[0049] 11 First marginal section

[0050] 12 Second marginal section

[0051] 13 Second marginal section

[0052] 14 expansion bolts

[0053] 15 expansion bolts

[0054] 16 Excerpt

[0055] 17 First half-shell

[0056] 18 Second half-shell

[0057] 19 fastening screws

[0058] 20 expansion bolts

[0059] 21 expansion bolts

[0060] 22 Longitudinal web

[0061] 23 Dovetail guide

[0062] 24 spring element

[0063] 25 Clutch

[0064] 26 Mother

[0065] 27 flange

[0066] 28 collars

[0067] Angles A, B, C, D

[0068] H Horizontal plane

[0069] X Connection direction

Claims

Claims:

1. Aircraft with a refueling port which is in a fluid-technical connection with a tank arranged in the aircraft, wherein -the refueling port and the tank are configured to receive a cryogenic fuel, wherein -the refueling port has a pipe section (7) and / or a coupling (25) specially designed for conveying a cryogenic fuel, which is fixed to an aircraft-mounted structure, characterized in that -for fixing the pipe section (7) and / or the coupling (25) a first half-shell (17) and a second half-shell (18) are provided, and -the first half-shell (17) is fixed to the aircraft-mounted structure, and -the second half-shell (18) is connected to the first half-shell (17) by an elastic clamping connection by exerting a clamping force on the tube section (7) and / or the coupling (25) and is in a linear guide (26) is guided in a slidable manner relative to the aircraft-fixed structure.

2. Aircraft with a refueling port according to claim 1, characterized in that -the linear guidance (26) of the second half-shell (18) and the direction of elasticity of the elastic clamping connection are aligned.

3. Aircraft according to one of claims 1 or 2, characterized in that -the second half-shell (18) with the first half-shell (17) is connected via the elastic clamping connection so that it is slidable perpendicular to the direction of elasticity.

4. Aircraft according to one of claims 1 to 3, characterized in that -the elastic clamping connection is realized by expansion bolts (14,15,20,21).

5. Aircraft according to claim 4, characterized in that the expansion bolts (14, 15, 20, 21) are connected via spring elements (24) support on the first and / or the second half-shell (17,18).

6. Aircraft according to claim 5, characterized in that the spring elements (24) are formed by disc springs.

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