GB2235249A

GB2235249A - Propulsion means for hypersonic flight

Info

Publication number: GB2235249A
Application number: GB9012648A
Authority: GB
Inventors: Christian Mundt
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1989-07-05
Filing date: 1990-06-06
Publication date: 1991-02-27
Also published as: FR2649446A1; DE3922018A1; DE3922018C2; GB9012648D0

Abstract

Propulsion means includes at least one ram-let engine 2 and at least one further engine, e.g. a turbo-jet engine 3, the internal flow channel of which is independent of that of the ram-jet engine. Prior to aircraft take-off the flow channel 8 of each ram-jet engine 2 is sealed at both ends (e.g. by flaps 6 and 7) and filled via filling device 11 with a liquid fuel component 10 provided for lower speed range. This fuel is completely removed (e.g. by suctioning off device 12) and used up by the engine(s) 3, operating at lower speed ranges prior to ignition of the ram-jet engines 2. When the ram-jet is operating, flap 6 may seal the turbo-jet engine intake while flap 7 helps determine the thrust trail contour 19. <IMAGE>

Description

f AJW160590 COMBINATION PROPULSION MEANS FOR HYPERSONIC FLIGHT -.. 1 - 1,

- This invention relates to a method of operating combination propulsion means for hypersonic flight said means including, for higher speed range, at least one ram-jet engine, and, for lower speed range, including takeoff phase, at least one further engine which has an internal flow channel independent from that of the ramjet engine.

The invention also covers the modified structure of combination propulsion means for performing this method.

For several years, increasing interest has been shown in hypersonic technology. Apart from military applications, increasing attention is paid, and support given, to projects for hypersonic commercial aircraft for long-haul flights, and for space transporters which spend a considerable proportion of their flight path in the atmosphere. In the case of the latter, a reduction of specific transport costs is an overriding design criterium. It is attempted to meet this criterium by reusable equipment, born in the atmosphere by aerodynamic lift forces and propelled by air-intake propulsion means. As far as technical realisation is concerned, there exist both single stage (NASP, Hotol) and two-stage suggestions (Sdnger).

AJW160590 The availability of suitable propulsion means is, of course, essential. The required thrust has to be made available by the propulsion means within a very large speed range between take-off and landing, and up to hypersonic speed at high altitudes. In practice, this requirement can only be met by combination propulsion means, comprising different types of propulsion. Accordingly, with increasing flight speed, initially turbojet engines, then ram-jet engines and finally, if the atmosphere is to be left, rocket drives are used. Propulsion means as a combination of these types, for example air-turbo-rocket (air intake turboengine with externalair-independent turbine propulsion) seems the only sensible option.

As regards fuel, all available propulsion means are preferably run with the same, or at least similar fuel, with a preference toward liquid hydrogen (H 2) A disadvantage of combination propulsion means is that, apart from short transitional phases, only one propulsion method is in use, dependent on the speed and environmental conditions (inside/outside the atmosphere). The idle propulsion means are 'dead' ballast which increases the volume and, within the atmosphere, the air resistance of the aircraft. The integration of several propulsion methods in combination AJW160590 propulsion means constitutes a general problem since the volume and the surface area of hypersonic aircraft should be as small as possible for aerodynamic, thermal and other reasons (mass, radar signature, etc.). Due to strong interacting effects of propulsion means and cell size in hypersonic flight, both the propulsion means and the cell have to be developed together and integrated.

It is an object of the present invention to provide a method of operating combination propulsion means for hypersonic flight, which, with respect to the integration of the propulsion means into the aircraft, allows for optimal space utilisation with minimum mass.

Pursuant hereto it is proposed that in combination propulsion means as specified in the first paragraph hereto the flow channel of the ram-jet engine is sealed, before take-off of the aircraft, at the mouth of its intake and at its jet side end and filled at least with a portion of a fuel component which is to be stored in liquid state, and that the fuel stored in the flow channel of the ram-jet engine is completely removed and used in the engine(s) operative at lower speed prior to ignition of the ram-jet engine(s).

To allow this method to be used, it is proposed that each ram-jet engine has on its intake side and on AJW160590 its jet side a respective fuel-proof cover for closing and opening its flow channel, and that each ram-jet engine has in its flow channel one or several devices for being filled with fuel and for having fuel removed by suction.

The advantage of the aforesaid proposal is that the ram-jet engine(s), which are only in use at higher flight speeds (super- to hypersonic) and which have a relatively large flow channel with few inserts, is/are used during the lower-speed range as fuel tanks and are emptied prior to their ignition. Thus, the ram-jet engine flow channel, which is sealable at both ends, holds at least part of the fuel component which is to be used up by the propulsion means operative in the lowerspeed range. Since these latter propulsion means are, as a rule, turbo-jet engines which use the oxygen from the air as oxidator, only liquid fuel, for example H2. is temporarily stored in the ram-jet engine(s). Apart from fuel-proof seals at both ends each ram-jet engine requires, according to the invention, at least one device for loading fuel and suctioning-off fuel.

The invention is now described in more detail, with reference to the accompanying schematic drawing, in which:

ZI AJW160590 - 5 - Fig.1 is a longitudinal section through two engines of combination propulsion means in accordance with the invention when in turbojet operation; and Fig.2 is the same longitudinal section as in Fig.1, but now shown when in ram-jet operation.

The combination propulsion means 1 illustrated in Figs. 1 and 2 includes a ram-jet engine 2 for the upper speed range, i.e. for super- and hypersonic flight, and a turbo-jet engine 3 for the lower speed range, i. e. for the take-off and, if appropriate, the landing phase as well as for speeds up to supersonic.

In the illustrated example, the ram-jet engine 2 is located above the turbo-jet engine 3, i.e. between the latter and the aircraft. However, the engines can also be arranged alongside each other or transversely offset laterally and/or in height.

The combination propulsion means in accordance with the invention can consist of two or more propulsion means, in which respect an arrangement in pairs of ramjet and turbo-jet engines is preferred. Space transporters which leave the atmosphere additionally AJW160590 6 - require at least one external-air-independent propulsion means, usually a rocket engine.

The propulsion means for the lower speed range do not necessarily have to be turbo-jet engines. Rocket engines, for example, can also be used, with solid, liquid and/or gaseous fuels. For many reasons (air oxygen as oxidator, degree of efficiency, etc) it is, however, more practical to use turbo-jet engines.

According to the arrangement in Figs. 1 and 2, the ram-jet engine 2 and the turbo-jet engine 3 are arranged so as to have a common intake area 4 and a common jet area.

In Fig. 1, only the turbo-jet engine 3 is in operation of which the compressor 14, the combustion chamber 15 including injection device 16, the turbine 17 and the afterburner 18 are schematically shown. The flow channel 9 is arranged upstream of the core engine as a diffusor, downstream as a Laval nozzle which can also be adjustable. The flame symbols at the injection device 16 and the afterburner 18 indicate operation at maximum thrust. The illustration has been kept as simple as possible for ease of viewing and does not give information about the exact type of turbo-jet engine which may be a single- or multi-shaft engine including 1 AJW160590 one or several flow circuits. The inflowing environmental air is illustrated by means of a white arrow, outflowing hot gas by means of a black-white arrow, and the outer contour of the thrust flow 20 is only vaguely indicated.

The turbo-jet engine 3 uses exclusively air oxygen as oxidator. Consquently, the only further propulsion component to be stored is fuel, at least for the lower speed range. Cryogenic fuel in liquid state is preferred in view of its manifold cooling functions and also for optimal utilisation of the storage volume, and liquid hydrogen (H 2) 'St in this respect, particularly suitable. At least part of this fuel is stored in the ram-jet engine(s), thus allowing a reduction in the volume of the conventional tank which results in an overall mass and space reduction. Estimated calculations with the "Sanger" aircraft indicate that the volume of the ram-jet engine which is usable as a tank represents approximately 5 to 10% of the entire tank volume, i.e. the conventional tank can be reduced by the aforesaid percentage figures. This proportion can be much higher for fuels of higher density as the entire tank volume reduces whilst the volume of the flow channel (8) remains steady. Furthermore, within the scope of this invention, in addition to H2 as fuel for the main flight period, an alternative, for example less 1 AJW160590 cryogenic fuel can be carried, exclusively stored in the ram-jet engines, during the take-off and initial flight phase. Since at the beginning of the flight mission, components to be cooled do not deliver significant heat quantities, easier evaporation (and heating, if required), and thus better combustion in the turbo-jet engines can be achieved with such less cryogenic fuel. If appropriate, kerosine may be used as such an additional non-cryogenic liquid fuel for the initial flight phase with sufficient cooling.

The simplest manner of fuel supply subsists in aircraft which do not leave the atmosphere and which can consequently be equipped exclusively with air-intake engines, in which case all the engines operate on the same fuel. In this case, only one fuel component is carried in the aircraft, namely liquid fuel. Depending on the requirements of the aircraft with respect to cooling efficiency, that fuel can be either cryogenic or non-cryogenic.

In Fig. 1, the flow channel 8 of the ram-jet engine 2 is shown as still extensively filled with fuel 10. The ram-jet engine 2 is closed towards the intake area 4 by means of a tiltable flap 6, and towards the jet area 5 by means of a further tiltable flap 7.

AJW160590 9 - In place of flaps, other closing means, such as linear slides, rotary slides, flap grids, etc. can of course also be used. Moreover, it is possible to provide anejectable or destructable closing means on the jet side. For example, a lid can be firmly installed which is separated from the nozzle by means of a fuse and ejected just before ignition of the ram- jet engine. The additional weight load of the two sealing members is minimal by comparison with arrangements which do not use the ram-jet engines as fuel store, as the engines have to be provided with a seal at the intake side in any case in order to guarantee satisfactory pressure recovery in the intake of turbo-jet engines in the lower speed range. This means, a member like the flap 6 has to be provided in any case. Thus, only the jet side sealing means remains as an additional mass. An arrangement such as a flap 7 improves jet geometry in respect of the ram- jet engine, so easily compensates for its slight mass increase by way of thrust increase.

In accordance with this invention, the flaps 6 must be fuel-tight which is otherwsie not necessary.

The ram-jet engine 2 can be filled via the indicated separate filling device 11 or by way of available pipes terminating in the flow channel 8. After filling, the filling device 11 can be used to 7 AJW160590 pressurise the fuel 10. Withdrawal of fuel 10 is via the suction device 12 which is preferably integrated into the flame holder arrangement 13 or constituted by the fuel injection system of the flame holder 13.

According to the illustration in Fig.1, fuel 10 is supplied to the injection device 16 and to the afterburner 18 of the turbo-jet engine 3. On the way thereto, the fuel flows through pumps, valves, heat exchangers etc. which are not illustrated for ease of viewing. The inventive utilisation of the ram-jet engine as a tank is further encouraged in that there are only a few fixed inserts, such as the flame holder arrangement with injection system and, if appropriate, vortex generators, which, practically do not restrict the flow-channel volume.

For the same reason, it is of no significance whether the propulsion means work by subsonic combustion (ram jets) or supersonic combustion (scram jets), and the term ram-jet used herein is intended to encompass both.

Fig. 2 illustrates-the conditions in the higher speed range. The turbojet engine 3 is sealed on the intake side by the flap 6 and is stationary (nonoperational). The ram-jet engine 2 is operative, as i AJW160590 - 1 1 - indicated by the flame symbols at the flame-holder arrangement 13. The flap 7 is part of the flow contour of the thrust jet and thus advantageously influences the contour of the thrust trail 19.

To summarise, it can be said that the invention permits particularly effective use of hypersonic combination propulsion means, whereby the payload thereof can be significantly increased.

AJW160590

Claims

12 - 1. A method of operating combination propulsion means for hypersonic flight, said means including, for higher speed-range, at least one ramjet engine, and, -for lower speed range, including take-off phase, at least one further engine which has an internal flow channel independent from that of the ram-jet engine, characterised in that the flow channel of the ram-jet engine is sealed, before take-off of the aircraft, at the mouth of its intake and at its jet side end and filled at least with a portion of a fuel component which is to be stored in liquid state and which is provided for the lower speed range, and that the fuel stored in the flow channel of the ram-jet engine is completely removed and used in the engine(s) operative at lower speed prior to ignition of the ram-jet engine(s).

2. Combination propulsion means, for performing the method claimed in claim 1, including at least one ramjet engine for higher speed range, and at least one further engine for lower speed ranges, which is arranged in parallel thereto as regards its flow channel, characterised in that each ram-jet engine has on its intake side and on its jet side a respective fuel-proof cover for closing and opening its flow channel, and that each ram-jet engine has in its flow channel one or t 1 AJW160590 13 several devices for being filled with fuel and for having fuel removed by suction.

3. Combination propulsion means as claimed in claim 2, wherein the intake side cover of each ram-jet engine is a tiltable flap or a slide, and the jet side cover is a tiltable flap, a slide or an ejectable cover.

4. Combination propulsion means as claimed in claim 2 or 3, wherein the device for suctioning-off the fuel is integrated into a flame holder arrangement of the ram-jet engine, in which respect at least a part of the pipe system for fuel injection during ram-jet operation is usable for suctioning-off'.

5. Combination propulsion means as claimed in claim 2,3 or 4 wherein each ram-jet engine and its respective associated further engine(s) for lower speed ranges have common intake areas and common jet areas.

6. Combination propulsion means as claimed in any of claims 2 to 5 wherein the further engine for lower speed ranges is a turbo-jet engine.

7. Combination propulsion means for hypersonic flight substantially as hereinbefore described with reference to and as illustrated by the accompanying drawing.

published 1991 at The Patent Office. State House. 66/71 HjgbHolborn. LAmdonWC I R4TP. Further copies may be obtained from - - n-a Ycn Nevmort. NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray, Kent.

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