GB2447291A

GB2447291A - A turbojet engine having a bypass flow through the engine core

Info

Publication number: GB2447291A
Application number: GB0704520A
Authority: GB
Inventors: John Edward Randell
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-03-08
Filing date: 2007-03-08
Publication date: 2008-09-10
Also published as: GB0704520D0

Abstract

A propulsion arrangement suitable for an aircraft comprises a compressor, a (first) propulsion gas flow 19, and a (second) discharge gas flow 23, the discharge gas flow being at least partially bounded by the propulsion gas flow at the gas outlet. Ideally, a turbojet comprises a first propulsive flow 19 which flows through a compressor 9 and a combustor 13 before being exhausted by the turbine 11, and a second bypass flow 21 which travels through a duct 1 at the engine core / centre and enters the centre of the jet formed by the turbine exhaust. The bypass / secondary air may be purely ram air 21, or may have passed through the compressor / fan (see fig.2) before being introduced into the jet flow. The introduction of the flow into the jet reduces the velocity differential, and therefore reduces noise. An independent claim entails diverting jet air through the duct so as to provide thrust reversal.

Description

I

I. 2447291 AIRCRAFT PROPULSiON ARRANGEMENTS The invention relates to aircraft propulsion arrangements and particularly to jet propulsion arrangements..

In a known turbojet engine, air enters through an intake at the front of the engine and is compressed by a compressor into a combustion chamber, into which fuel is injected and burned. The rise in temperature causes the gases in the combustion chamber to expand and a propulsion Jet is formed by the exhaust gases being expelled through an exhaust nozzle at the rear of the engine via a turbine which drives the aforesaid compressors.

The flow from the turbine has an annular cross section and the nozzle converts the exhaust flow into a jet of circular cross section by convergence of the annular flow.

1 5 In the formation of a jet of circular cross section in a nozzle, surfaces in the interior bounded by an annular flow from a turbine are subject to suction, with resultant drag.

Noise is generated by turbulence as a propulsion jet mixes with air in the atmosphere.

According to a first aspect of the invention, there is provided a propulsion arrangement for an aircraft, the propulsion arrangement comprising a body defining a gas inlet, at least one region for compressing gas, the or each region being arranged so that compressed gas issued by the or each region can form or contribute to forming a propulsion gas flow means to form a discharge gas flow and a gas outlet, wherein the propulsion arrangement is arranged so that the propulsion gas flow at least partially bounds the discharge gas flow at the gas outlet.

By discharging air which is moving relatively slowly into the core of a propulsion jet, the flow of the jet is slowed and less noise is produced.

Noise generation is reduced further by a confining jet while it is slowed by the entrainment of air.

According to a second aspect of the invention, there is provided a propulsion arrangement for an aircraft, the propulsion arrangement comprising a combustion region for combustion of gases, the propulsion arrangement being arranged for exhaust gas to exit the propulsion arrangement so as to provide thrust, wherein the propulsion arrangement is arranged to discharge a flow of gas through a duct so as to bypass the 1 5 aforesaid combustion region and flow into the core of the exhaust gas from the combustion region.

According to a third aspect of the invention, there is provided a jet propulsion arrangement for an aircraft, the propulsion arrangement comprising a casing and an inlet for compressed gas in the longitudinal side wall of the casing.

According to a fourth aspect of the invention, there is provided a jet propulsion arrangement comprising a first and second jet propulsion means, the first jet propulsion means comprising a jet turbine engine having a compressor and a turbine and having a duct for supplying air compressed in the jet turbine compressor to the second, separate, jet propulsion means.

According to a fifth aspect of the invention, there is provided a propulsion arrangement for an aircraft, the propulsion arrangement comprising a jet engine having a casing with an outlet in the longitudinal side wall of the casing, the outlet being arranged to supply compressed gas to a second propulsion arrangement.

According to a sixth aspect of the invention, there is provided a jet propulsion arrangement for an aircraft, wherein the propulsion arrangement comprises a discharge outlet arranged along at least part of the axial length thereof.

According to a seventh aspect of the invention, there is provided a propulsion arrangement for an aircraft, comprising a body defining a gas inlet at the front end thereof, a gas outlet at the rear end thereof, and a longitudinal duct running from the front end to the rear end of the body and means to divert or discharge a propulsion jet forwards through the longitudinal duct from the rear to the front of the engine to provide a reverse thrust.

Jet propulsion arrangements, particularly jet engines, in accordance with the invention will now be described, by way of examples only, and with reference to the accompanying drawings, in which: Figure 1 is a schematic section, in a vertical plane, through a centre line (axis) of a jet engine in a first embodiment of the first and second aspects of the invention, Figure 2 is a schematic section, in a vertical plane, through a centre line ofajet engine in a second embodiment of the first and second aspects of the invention, Figure 3 is a schematic section, in a vertical plane, through a centre line ofajet engine in a third embodiment of the first and second aspects of the invention, Figure 4 is schematic section, in a vertical plane, through a centre line of a jet engine in a fourth embodiment of the first and second aspects of the invention, Figure 5 is a schematic section, in a vertical plane, through a centre line of a jet engine in a fifth embodiment of the first and second aspects of the invention, Figure 6 is a schematic section, in a vertical plane, through a centre line of a jet engine in a sixth embodiment of the first and second aspects of the invention, Figure 7 is a schematic section, in a vertical plane, through a centre line of a jet engine in a first embodiment of the third aspect of the invention, Figure 8 is a schematic section, in a vertical plane, through a centre line ofajet engine in an second embodiment of the third aspect of the invention, Figure 9 is a schematic section, in a vertical plane, through a centre line ofa jet engine in a third embodiment of the third aspect of the invention, Figure 10 is a schematic section, in a vertical plane, through a centre line ofa jet engine in a fourth embodiment of the third aspect of the invention, Figure 11 is a schematic section, in a vertical plane, through a centre line ofajet engine in a first embodiment of the fourth, fifth and sixth aspects of the invention, Figure 12a is a schematic view, from the front, of two engines coupled by a wing in a second embodiment of the fourth, fifth and sixth aspects of the invention, Figure 1 2b is a schematic view, in plan, of the two coupled engines of Figure 1 2a, Figure 13a is, in part, a schematic section, in a vertical plane, through the wing of Figure 12a, and, in part, a side view of one of the two coupled engines of Figure 12a, taken along the line XIIla in the direction of the arrows, Figure 13b is a schematic section, in a vertical plane, of the engine and wing part of Figure 1 3a, taken along the line XlllIb, Figure 14a is a front schematic view of two engines coupled by a wing in a third embodiment of the fourth, fifth and sixth aspects of the invention, Figure 14b is a schematic plan view of the two coupled engines of Figure 14a, Figure 15a is, in part, a schematic section, in a vertical plane, through the wing of Figure 14a and, in part, a side view of part of one of the two coupled engines of Figure 14a, taken along line XVa, in the direction of the arrows, Figure 1 5b is a schematic section, in a vertical plane, of the engine and wing part of Figure 1 5a, taken along line XVb, Figure lóis a schematic section, in a vertical plane, through a centre line ofajet engine in an embodiment of the first, second and sixth aspects of the invention, Figure 1 7 is a schematic section, in a vertical plane, through the centre line of the jet engine of Figure 16, Figure 18 is a schematic section through the jet engine of Figure 1 7, taken along line XVIII, in the direction of the arrows, Figure 19 is a schematic front view ofajet engine in an embodiment of the sixth aspect of the invention, Figure 20 is a schematic front view of gas discharged from ajet engine in, for example, the embodiment shown in Figures 17 to 19, Figure 21 is a schematic front view of gas discharged from a two jet engine arrangement in another embodiment of the sixth aspect of the invention, Figure 22 is a schematic front view of the two jet engine arrangement of Figure 21, showing each engine suspended from an aircraft wing by an inclined wing, Figure 23 is a schematic front view of a two jet engine arrangement, each engine suspended from the same single wing by an upwardly, and outwardly inclined wing, in another embodiment of the invention, Figure 24 is a schematic front view of a two jet engine arrangement, each engine suspended from the same single aircraft wing by an upwardly, and inwardly, inclined wing, in a further embodiment of the invention, Figure 25a is a schematic front view of a pair of engines, each engine suspended from an aircraft wing by an upwardly, and inwardly, inclined wing and an upwardly, and outwardly, inclined wing, and Figure 25b is a schematic plan view of the engine pair of Figure 25a.

Jet propulsion engines for aircraft comprise a compressor, followed by a combustion chamber, a turbine to drive the compressor and a nozzle arrangement to form a propulsion jet from the exhaust of the turbine.

Referring to Figure 1, in a jet engine a longitudinal duct I passes through the interior of the engine.

The engine shown in Figure 1 is housed in a cylindrical casing 3. The duct I has a cylindrical wall 5 concentric with the engine casing 3 and is open to the atmosphere at both ends. A rotatable sleeve 7 is mounted on the duct wall 5. The rotatable sleeve 7 drives a compressor, represented by rows of blades 9, at the front and is rotated by a turbine, represented by a row of blades 11, at the rear. A combustion chamber 1 3 is located between the compressor and the turbine. The combustion chamber 13 is provided with a fuel supply, represented figuratively by arrow 15.

The compressor 9 has an air intake 1 7 at the front of the engine. A propulsion jet 19 with an annular cross section is formed by the exhaust from the turbine I I at the rear.

1 5 An air flow shown by arrow 2 I enters the duct I at the front of the engine and passes through the duct to be discharged within the annular jet 19 from the turbine at the rear, as shown by arrow 23.

Drag on the engine is reduced because surfaces which would be subject to suction in the central area of the known jet engines are absent and replaced by duct 1.

The duct wall 5 is spaced from the engine casing 3 by inlet guide vanes 25 at the front of the engine and by turbine exhaust guide vanes 27 at the rear.

Referring to Figure 2, in another engine, air is driven through a central duct I by a compressor 9C. This increases the thrust of the engine. Compressor blades 9C which drive air through the duct I are mounted inwards on the front end of a rotatable sleeve 7 mounted on the wall of the duct. At the front of the engine, inlet guide vanes 25 are connected rigidly to another set of inlet guide vanes 29 mounted on a static core 31 of aerodynamic shape. Guide vanes 33 downstream of the compressor blades 9C space the wall 5 of the duct I from the static core 3 1. At the rear of the engine, the wall 5 of the duct is spaced from the casing by guide vanes 27 as in the engine shown in Figure 1.

Referring to Figure 3, in another engine, blades 9 of a compressor and blades Ii of a turbine are carried by a tube 8 which is connected rigidly by blades 10, 12 to a sleeve 14 which rotates on an axle 16.

The axle 16 is spaced from an engine casing 3 at the front by guide vanes 18. At the rear, the axle 16 is spaced by guide vanes 20 fixed to turbine outlet guide vanes 27. A duct 22 of annular cross section is formed between the sleeve 14 and the tube 8.

Rotation of the tube 8 by the turbine 11 causes the blades 10 and 12 that connect the sleeve 14 to the tube 8 to drive air through the duct 22 from an intake 21 at the front of the engine. The duct 22 discharges air, as shown by arrow 23, into the space inside ajet 19 formed by exhaust from the turbine 11. This forms a propulsion jet of circular cross section in an outlet plane at the rear of the engine.

A flow of air through a longitudinal duct from the front of an engine to the rear can be heated by combustion of fuel to increase the thrust of an engine.

Forward motion of an aircraft produces a ram effect on the entry to a duct at the front of an engine and a longitudinal duct from the front to the rear that incorporates a combustion chamber can be shaped like a ramjet tube to provide thrust efficiently (at high aircraft speeds).

Referring to Figure 4, another engine has a longitudinal duct formed from a divergent section IA, a combustion chamber lB (with fuel supply represented by arrow 35) and a section 1 C which converges to a nozzle to provide a propulsion jet 23.

A wall 5 of the longitudinal duct is shaped so that a sleeve 7 of suitable form can rotate on it, the sleeve 7 being rotated by a turbine 11 to drive a compressor 9. Fuel is also supplied, as shown by arrow 1 5, to a combustion chamber 1 3 between the compressor 9 and turbine 11.

The two propulsion jets, 19 and 23, merge to form a propulsion jet of circular cross section. The propulsion jet 23 (from the longitudinal duct 1) provides a core inside propulsion jet 19 (formed by exhaust from the turbine 11).

In the engine shown in Figure 4, a casing has a cylindrical section 3C at the front and a rear section 31 which tapers to a nozzle at the rear. The wall 5 of the longitudinal duct is spaced from an engine casing by inlet guide vanes 25 at the front and turbine exhaust guide vanes 27 at the rear.

in the figures showing engines which follow) guide vanes which space a rotatable sleeve from an engine casing are omitted for clarity. Also, a rotatable sleeve which connects a compressor and a turbine is shown in a cylindrical form. A rotatable sleeve may be shaped to direct flow or for constructional reasons.

In jet engines used commercially, some of the intake air into a compressor at the front of the engine bypasses the power plant. The bypass air is discharged at the rear, with the propulsion jet formed from a turbine exhaust.

An engine in which provision is made for bypass air is shown in Figure 5. An intake 17 of air flows through blades, 9A, of a compressor. The intake air is then divided by a cylindrical wall 37. One part of the air flow is compressed further, by blades 9B of a compressor, and passes through a combustion chamber 1 3 and a turbine 11. The turbine drives a rotatable sleeve 7 upon which the compressor blades, 9A and 9B, are mounted. The remainder of the air intake passes through a duct 39 of annular cross section formed between the dividing wall 37 and an engine casing 3. The flow 41 from the annular duct 39 merges with the exhaust 1 9 from the turbine 11 to form a propulsion jet, 43, of annu]ar cross section.

When a propulsion jet is discharged through a nozzle, shearing forces cause turbulence and consequent noise generation. Noise generation is reduced if a propulsion jet is slowed by the entrainment of air.

In the engine shown in Figure 5, a flow 23 of air carried by a duct I from the front of the engine is discharged into a core zone of the propulsion jet 43. This has the effect of slowing the propulsion jet and thereby reducing noise generation.

Less noise will be generated if a propulsion jet is slowed by entrainment of air in a confined space, because less turbulence is then created.

The engine shown in Figure 5 may be modified for this reason by incorporating, as shown in Figure 6, a chamber 45 in which intake air 21 that passes through a central duct 1 from the front of the engine is entrained by a propulsion jet 19 from a turbine in a confined space within the engine casing 3. A jet 41 of bypass air is discharged around the perimeter.

An engine which relies upon ram effect to generate thrust requires separate or 1 5 additional provision for thrust at low aircraft speed. In the case of the engine shown (previously) in Figure 4, a propulsion jet is provided at low aircraft speed by a propulsion jet formed by the exhaust from a turbine. The turbine discharge can be replaced by an equivalent discharge if compressed gas is supplied to an engine. Such an arrangement is illustrated in Figure 7.

In the engine illustrated in Figure 7, compressed air is supplied, as represented by an arrow 24, to an annular chamber 26 formed by an engine casing 3X. A propulsion jet of air of annular cross section, shown by arrow I 9E, provides an equivalent of the flow through the annular jet 19 from a turbine shown in Figure 4.

The arrangement shown in Figure 7 can be modified as shown in Figure 8 to provide an improved engine.

In the engine shown in Figure 8, an air intake 30 passes through an annular duct 2X between the wall 5 of a central duct and a wall 4 of an annular chamber 26. The flow through the duct 2X mixes with a discharge of air 28 from the chamber 26 before discharge to atmosphere in a propulsion jet 32 formed around the wall 5 of the central duct. The thrust of the engine can be increased by providing a supply of fuel, represented by arrow 34, to a combustion chamber 36 to raise the temperature of the gas discharged in the propulsion jet 32.

A simpler engine is provided by omission of a separate duct through the centre of the engine, as shown in Figure 9. A duct 2 is formed by an inner wall 4 of the chamber 26.

A propulsion jet 38 from the chamber 26 merges with a flow of air through the duct 2 1 5 from an intake 40. An engine casing 3X tapers to a nozzle to form a propulsion jet 42.

The thrust may be increased by incorporating a combustion chamber 44 with a fuel supply, represented by arrow 46.

A propulsion engine with low noise generation can be provided by expanding a propulsion jet along the wall of a duct through which entrainment air can flow. Such an engine is shown in Figure 10.

A propulsion jet 48 from an annular nozzle 50 is discharged along the inside wall 6B of a circular duct 2. Upstream of the nozzle 50, the wall 6A of the duct 2 forms an inlet for an intake 40 of air. The propulsion jet 48 slows as it flows along the wall 6B and expands with the entrainment of air in the duct. The propulsion jet 42 that exits the casing 3X is formed within a confined space in the engine, providing a jet propulsion arrangement in which energy losses due to turbulence are low and so is noise generation.

The annular nozzle 50 may be divided into a ring of individual nozzles, each of circular or elongated cross section, since individual jets from a ring of nozzles coalesce to form an annular jet.

An engine of the kind shown in any of Figures 7, 8, 9 or 10 is dependent upon a supply of compressed gas. This requirement can be met by supplying compressed air from another engine.

An engine of the kind shown in Figure 6 can be adapted to supply compressed air. An adapted engine is shown in Figure 11.

Air from an intake 17 passes through a compressor 9 and is then divided into two parts by a cylindrical wall 37. One part of the flow passes through a combustion chamber 13 and a turbine II which drives the compressor 9. The turbine exhaust gases are mixed in a chamber 45 with an intake 21 of air that passes through a longitudinal duct I, the merged flow providing a propulsion jet 47 at the rear. The remainder of the air taken in and compressed enters a duct inside a wing 49 to provide a supply of compressed air 24 to another engine.

An engine of the kind shown in Figure 10 is shown coupled by a wing 49 to an engine of the kind shown in Figure 11 in a view from the front in Figure 12a and in plan in Figure 12b. Figure 13a is a section in a vertical plane perpendicular to the connecting wing 49 and Figure 13b is a section in part in a vertical plane parallel to the connecting wing 49.

The use of a second engine of the kind shown in Figure 10 with ajet propulsion engine reduces noise generation because a greater volume of air can then be entrained.

A second engine in a pair may be smaller than a first engine which contains a compressor and the second engine may be used for control purposes, such as when an aircraft is turned. Fuel can be saved by varying the thrust of a second engine to turn an aircraft instead of relying upon the action of a rudder. For steering purposes a flow of compressed gas to a second engine located outboard of a main engine, which supplies the compressed gas, may be regulated.

The performance of two engines coupled together, in which one engine supplies compressed air to the other, depends upon the transfer of compressed air with a small pressure loss. This is facilitated by providing a connecting duct of large cross sectional area and by utilising the swirl of the air in an engine casing. If the connecting duct between the engines is of aerofoil section, the duct can provide a lift force which assists in supporting the weight of the engines.

An arrangement in which engines shown individually in Figures 10 and II are connected by a wing 49W, is shown in Figure 1 4a and in Figure 1 4b. The compressor 9 of the intake engine rotates in the direction shown by arrow 51 in Figure 1 4a. Figure 15a is a section in a vertical plane perpendicular to the connecting wing 49W. Figure 1 5b is a section in part in a vertical plane parallel with the connecting wing 49W.

A wing which connects two engines can provide additional lift on take off and so reduce the length of runway required.

When air is displaced downwards between two engine casings by a wing, air is drawn in from the sides over the engine casings in stream wise vortex flows. Such vortex flows can be generated by discharging a layer of gas from an engine over the upper surface of its casing. This creates suction on the casing and the lift force that results is independent of forward movement by an aircraft. An aircraft can take off vertically if 1 5 the lift force created by Suction on the upper surfaces of engine casings is sufficiently large.

The power required for vertical take off requires the use of engines of large diameter and, during transition from vertical to horizontal flight, it is desirable for stability that Suction on the rear of an engine caused by forward movement is minimised. A free flow of air through an engine facilitates this. Also, an engine is required in which ajet can be discharged over a casing for lift or backwards for forward propulsion.

For this purpose, to enable an aircraft to take off vertically, an engine of the kind shown in Figure 6 can be adapted as shown in Figure 16.

In the engine shown in Figure 16, a central duct I with an air intake 21 at the front diverges to the rear to minimise suction on the rear on slow forward movement.

Two linked changeover valves are provided, shown in Figure 16 as sliding valves 53 and 55 in the form of sleeves. These valves are shown in Figure 16 in positions in which only horizontal thrust is provided by the engine. An intake of air passes through a compressor 9A and is then divided into two parts by a cylindrical wall 37. One part of the air flow passes through a compressor 9B, a combustion chamber 13 and a turbine 11 which drives the compressors, 9A and 9B. The flow of exhaust gas from the turbine 11 is directed as shown by arrow 57 to a nozzle 59 from which a propulsion jet 19 is discharged into a chamber 45 to form a jet 47 by mixing with air intake 21. The other part of the air flow from compressor 9A passes through an annular chamber 39 to be discharged at the rear as a propulsion jet 41.

On changeover, the sliding valve 53 diverts the flow of exhaust gas from the turbine into the annular chamber 39, as shown by arrow 61 in Figure 17. The rear end of the annular chamber 39 is closed off by the sliding valve 55, as also shown in Figure 17.

The annular chamber 39 is provided with an outlet in the form of a longitudinal slot 63 along the top of the engine casing 3. Means of regulating discharge of compressed gas through the slot is also provided so that either the slot can be sealed for horizontal propulsion or the whole of the flow through the engine can be discharged through the slot 63 for vertical flight. A rotary valve 65 for regulating flow through the slot 63 is shown in Figure 18. The rotary valve is shown in the open position for discharge through the slot. The slot 63 can be sealed to flow by movement of the valve 65 in the direction shown by arrow 67.

The turbine blades 11 rotate in the direction shown by the arrow 69 to produce swirl in the annular chamber 39. The energy associated with swirl is then utilised in the discharge through the slot 63. To utilise swirl in the engine, the casing may alternatively be formed as a volute. An engine shown in Figure 19 has a casing 3V formed in part as a volute.

Gas is discharged from the longitudinal slot 63 horizontally, as shown in Figures 18 and 19 by an arrow 71, An elongated jet which flows over the surface of an engine casing is formed by the gas discharge 71.

The slot may be formed as a nozzle or a row of individual nozzles may be substituted for the slot. Jets from adjacent nozzles in a row coalesce to form an elongated jet.

When gas is discharged as an elongated jet over an engine casing 3, as shown in Figure 20, the jet is drawn downwards by suction on the surface of the casing as shown by arrow 73. The thickness of the jet increases in the process as air is entrained at the boundary with the atmosphere and the jet spreads as shown by arrows 75o, 75 and 75i in Figure 20.

It has been found by private experiment that when gas is discharged horizontally, as shown by arrow 71 in Figure 20, the expanded jet tends to separate from a cylindrical surface as the general direction of the air stream approaches the vertical direction. The pressure on the underside of a cylindrical surface is close to atmosphenc pressure because the flow is separated from the surface on the underside. A lift force exerted on the casing by suction above the horizontal centre plane is not therefore countered by suction on the underside.

When two engines like the engine shown in section in Figure 18 are arranged, as shown in Figure 21, with the casings spaced apart by a distance approximately equal to the diameter of an engine casing and with facing nozzles, the jets 71a and 71b expand in a confined space between the casings. Air entrained by the jets 71a and 71b is drawn in from above, as shown by arrow 77, and a combined flow 79 is discharged downwards between the engine casings. This arrangement for providing a vertical propulsion jet is efficient because the turbulence associated with the process of expansion as atmospheric air is entrained at the boundary of a jet is reduced by confinement between the casings. Consequently energy losses as a result of turbulence are low.

The flow in the central region of a horizontal plane through the bottom of the engine casings is predominantly vertical, as shown by arrows 79, but flows 79a and 79b outwards reduce lift by causing suction on the undersides of the engine casings.

The outward flows, 79a and 79b, can be countered by creating air flows downwards around the outer sides of the engine casings. Such flows are shown by arrows 81 a and 8lb in Figure 22 which is a view from the front of a pair of engine casings arranged as shown in Figure 21. The engines are shown suspended from a pair of aircraft wings, 83a and 83b, by inclined wings, 85a and 85b, which extend upwardly and outwardly from the engine casings. Such inclined wings, 85a and 85b, create downward flows around the outer sides of a pair of engine casings, countering the formation of vortexes about the casings. Vortexes formed about engine casings at the rear are a source of drag.

Opposing flows beneath a casing increase the pressure on the underside of the casing and thereby the lift. A discharge of gas over the surface of a casing may be inclined downwards in order to maximise lift.

1 5 Inclined wings create vortex flows, shown by arrows 87a and 87b in Figure 22, centred on the junctions of the inclined wings 85a and 85b with the aircraft wings, 83a and 83b.

These vortex flows draw air downwards into the region above the engine casings.

A pair of engines may be suspended, as shown in Figure 23, from an underside 83U of an aircraft wing. The engines are shown suspended byinclined wings, 85a and 85b, located at the rear of the engine casings, 3a and 3b, behind discharge slots for vertical propulsion.

At the front, a pair of engine casings may be suspended from an aircraft wing by inclined wings which extend upwardly and inwardly from the engine casings, 3a and 3b, as shown in Figure 24. The inclined wings, 89a and 89b, then displace air inwards, as shown by arrows 91a and 91b, towards the space between the engine casings, 3a, 3b.

On forward motion of an aircraft, this reinforces a flow downwards between the engine casings induced by jets directed over the surfaces of the casings. The flow of air downwards between the engine casings can be further increased on forward motion, to provide additional lift, by the use of a horizontal wing 93 to space the two engine casings 3a and 3b. The displacement of air downwards 95 by such a horizontal wing to provide additional lift at the front of the aircraft may be maximised by the use of a flap.

A pair of engines suspended from the underside 83U of an aircraft wing by inwardly inclined wings at the front, as shown schematically in Figure 24, and outwardly inclined wings at the rear, as shown schematically in Figure 23, is shown in a front view in Figure 25a and in plan in Figure 25b. The engine casings 3a and 3b are spaced by a horizontal connecting wing 93 with a flap 99.

The engines rotate in the directions shown by arrows 97a and 97b. Swirl induced by an engine air intake then contributes to a downwards flow between the casings to provide lift.

Reverse thrust can be provided by diverting a propulsion jet forwards through a longitudinal duct to the front of an engine.

Claims

1. A propulsion arrangement for an. aircraft, the propulsion arrangement comprising a body defining a gas inlet, at least one region for compressed air, the or each region being arranged so that compressed gas issued by the or each region can form or contribute to forming a propulsion gas flow, means to form a discharge gas flow, and a gas outlet, wherein the propulsion arrangement is arranged so that the propulsion gas flow at least partially bounds the discharge gas flow at the gas outlet.

2. A propulsion arrangement according to Claim 1, wherein the propulsion arrangement is arranged so that the propulsion gas flow comprises a discharge of gas in ajet of annular cross section.

3. A propulsion arrangement according to Claim 1, wherein the propulsion arrangement is arranged so that the propulsion gas flow comprises a discharge of gas in a ring of circular section jets.

4. A propulsion arrangement according to Claim 2 or 3, wherein the propulsion arrangement is arranged so that the propulsion gas flow is formed by the exhaust from a turbine of a turbojet engine.

5. A propulsion arrangement according to Claim 4, wherein the propulsion arrangement is arranged so that the discharge gas flow mixes with the propulsion gas flow downstream of the turbine.

6. A propulsion arrangement according to claim 2, wherein the propulsion arrangement is arranged so that the discharge gas flow flows within the annular propulsion gas flow.

7. A propulsion arrangement according to any preceding claim, wherein the propulsion arrangement is arranged so that the discharge gas flow is provided through a duct.

8. A propulsion arrangement according to Claim 7, wherein the duct is a longitudinal duct.

9. A propulsion arrangement according to Claim 7 or 8, wherein the propulsion arrangement has a casing and the duct is approximately concentric with the casing.

10. A propulsion arrangement according to Claim 7, 8 or 9, wherein the propulsion arrangement is arranged so that the duct is open to atmosphere at a front end of the propulsion arrangement.

II. A propulsion arrangement according to any of Claims 7 to 10, wherein the propulsion arrangement is arranged so that the duct is open to atmosphere at a rear end of the propulsion arrangement.

12. A propulsion arrangement according to any of Claims 7 to 11, wherein the propulsion arrangement comprises a plurality of inlets to the duct.

13. A propulsion arrangement according to Claim 12, wherein the propulsion arrangement comprises at least one guide vane which separates an air flow duct into a plurality of air flow duct parts.

14. A propulsion arrangement according to any of Claims 7 to 13, wherein the propulsion arrangement comprises a compressor arranged to direct air into the duct.

15. A propulsion arrangement according to any of Claims 7 to 14, wherein the duct is of annular cross section.

1 6. A propulsion arrangement according to any of Claims 7 to 1 5, wherein the duct is of circular cross section.

17. A propulsion arrangement according to any of Claims 7 to I 6, wherein the duct comprises a static core.

18. A propulsion arrangement according to Claim 17, wherein the static core is aerodynamically shaped.

19. A propulsion arrangement according to any of Claims 7 to 1 8, wherein the duct comprises a combustion chamber to allow the discharge gas flow flowing therethrough to be heated by the combustion of fuel.

20. A propulsion arrangement according to Claim 19, wherein the heated discharge gas flow from the duct is arranged to mix with the propulsion gas flow.

21. A propulsion arrangement according to Claim 19 or 20, wherein the heated discharge gas flow from the duct and the propulsion gas flow combine to form a jet of circular cross section.

22. A propulsion arrangement according to any of Claims 8 to 21, wherein the longitudinal duct comprises a divergent section and/or a convergent section which forms a nozzle.

23. A propulsion arrangement according to any of Claims 7 to 22, wherein the propulsion gas flow is arranged to pass through a nozzle.

24. A propulsion arrangement according to any of Claims 7 to 23, wherein the propulsion gas flow is arranged to include exhaust gas from a turbine merged with air that bypasses the turbine.

25. A propulsion arrangement according to Claim 22, wherein the propulsion arrangement is arranged so that the bypass air radially surrounds the exhaust gas.

26. A propulsion arrangement according to any of Claims 8 to 25, wherein the propulsion arrangement is arranged so that an air flow through the longitudinal duct can be mixed with exhaust gas from a turbine longitudinally inbound from the gas outlet of the propulsion arrangement.

27. A propulsion arrangement according to any preceding claim, wherein the propulsion arrangement comprises a turbine and a compressor, and the turbine is arranged to drive the compressor via a rotatable tubular part.

28. A propulsion arrangement according to Claim 27, when dependent on any of 1 5 Claims 7 to 27, wherein the rotatable tubular part is arranged like a sleeve on an outer wall of the duct.

29. A propulsion arrangement according to Claim 28, wherein the compressor comprises blades which are inwardly directed so that the free ends of the blades arc at a radially inner part of the compressor.

30. A propulsion arrangement according to Claim 28 or 29, wherein the rotatable tubular part is coupled to a tube, which tube may be mounted on an axle.

31. A propulsion arrangement according to Claim 30, wherein the sleeve is coupled to the tube by blades.

32. A propulsion arrangement according to Claim 30 or 31, wherein the tube is concentrically mounted within the sleeve.

33. A propulsion arrangement according to Claim 31, wherein the blades are arranged to drive air through the duct.

34. A propulsion arrangement according to Claim 27, wherein a cavity is defined by an inner part of the compressor.

35. A propulsion arrangement according to Claim 27, wherein a cavity is defined by an inner part of the turbine.

36. A propulsion arrangement for an aircraft, the propulsion arrangement comprising a combustion region for combustion of gases, the propulsion arrangement being arranged for exhaust gas to exit the propulsion arrangement so as to provide thrust, wherein the propulsion arrangement is arranged to discharge a flow of gas through a duct so as to bypass the aforesaid combustion region and flow into the core of the exhaust gas from the combustion region.

37. A propulsion arrangement according to any preceding claim, wherein the propulsion arrangement comprises a casing and an inlet for compressed gas in the longitudinal side wall of the casing.

38. A jet propulsion arrangement for an aircraft, the propulsion arrangement comprising a casing and an inlet for compressed gas in the longitudinal side wall of the casing.

39. A propulsion arrangement according to Claim 37 or 38, wherein the propulsion arrangement is arranged so compressed gas can flow through the inlet to form a propulsion jet or jets.

40. A propulsion arrangement according to Claim 37, 38 or 39, wherein the propulsion arrangement comprises an annular shaped region for compressed gas.

41. A propulsion arrangement according to Claim 40, wherein the annular shaped region comprises an outlet for a compressed gas propulsion jet.

42. A propulsion arrangement according to Claim 40, wherein the propulsion arrangement comprises a plurality of outlets for a plurality of compressed gas propulsion jets.

43. A propulsion arrangement according to Claim 41 or 42, wherein the or each outlet is on inside surface of the annular shaped region.

44. A propulsion arrangement according to Claim 43, wherein the or each outlet is at least partially defined by a wall which is approximately parallel with the longitudinal axis of the propulsion arrangement.

45. A propulsion arrangement according to Claim 44, wherein the or each outlet is at least partially defined by a second wall which forms a nozzle-like exit to the propulsion arrangement.

46. A propulsion arrangement according to any of Claims 37 to 45, wherein the propulsion arrangement compnses an air intake arranged to allow a second air flow between a compressed gas propulsion jet or jets and a first air flow through the duct.

47. A propulsion arrangement according to any of Claims 37 to 46, wherein the inlet is in gas flow communication with a second propulsion arrangement.

48. A propulsion arrangement according to any of Claims 37 to 47, wherein a propulsion jet is discharged through an annular nozzle, or ring of nozzles.

49. A propulsion arrangement according to any of Claims 37 to 48, wherein the propulsion arrangement is in the form of a jet engine which has an outlet arranged to supply compressed air to a second jet propulsion means.

50. A propulsion arrangement according to any of Claims 37 to 49, wherein the second jet propulsion means is smaller than the jet engine propulsion arrangement.

51. A propulsion arrangement according to any of Claims 37 to 50, wherein the two propulsion arrangements are coupled by a duct which defines the inlet.

52. A jet propulsion arrangement comprising first and second jet propulsion means, the first jet propulsion means comprising a jet turbine engine having a compressor and a turbine and having a duct for supplying air compressed in the jet turbine compressor to the second, separate jet propulsion means.

53. A propulsion arrangement according to Claim 51 or 52, wherein the duct has an aerofoil section.

54. A propulsion arrangement according to Claim 51, 52 or 53, wherein the duct is straight.

55. A propulsion arrangement according to Claim 54, wherein the duct extends along a line drawn between centres of the two propulsion arrangements.

56. A propulsion arrangement according to Claim 54, wherein the duct is in a straight line tangential to the first and/or the second propulsion arrangement.

57. A propulsion arrangement according to Claim 56, wherein the compressor is arranged to rotate in a direction so that gas flows in a direction along the tangential duct.

58. A propulsion arrangement for an aircraft, the propulsion arrangement comprising a j* engine having a casing with an outlet in the longitudinal side wall of the casing, the outlet being arranged to supply compressed gas to a second propulsion arrangement.

59. A propulsion arrangement according to Claim 58, wherein the propulsion arrangement comprises an outlet arranged to discharge gas in an elongated jet over an upper portion of its casing.

60. A jet propulsion arrangement for an aircraft, wherein the propulsion arrangement comprises a discharge outlet arranged along at least part of the axial length of the arrangement.

61. A propulsion arrangement according to Claims 59 or 60, wherein the propulsion arrangement is arranged so that compressed air is directed out of the discharge outlet.

62. A propulsion arrangement according to Claim 60 or 61, wherein the discharge outlet is arranged to direct compressed gas over at least part of the upper surface of the propulsion arrangement.

63. A propulsion arrangement according to any of Claims 59 to 62, wherein the propulsion arrangement comprises a first valve which is movable from a first position in which gas can flow axially to provide axial thrust, into a second position in which gas can be directed over at least part of an upper surface of the propulsion arrangement.

64. A propulsion arrangement according to any of Claims 59 to 63, wherein the outlet comprises a series of nozzles or longitudinal slot(s) along upper surface of propulsion arrangement.

65. A propulsion arrangement according to Claim 63 or 64, wherein the propulsion arrangement comprises a second valve which is movable from a first position in which gas can flow axially to provide axial thrust, into a second position in which gas can be directed into an annular chamber and over at least part of an upper surface of the propulsion arrangement.

66. A propulsion arrangement according to Claim 65, wherein the nozzles or slot(s) is/are arranged so that gas is discharged approximately tangentially to the casing of the propulsion arrangement.

67. A propulsion arrangement according to any of Claims 59 to 66, wherein the propulsion arrangement comprises an inclined wing arranged to create an air flow in another direction about the propulsion arrangement to the flow from the outlet.

68. A propulsion arrangement according to any of Claims 59 to 67, wherein the propulsion arrangement comprises a casing which is formed at least in part as a volute.

69. A propulsion arrangement according to any of Claims 59 to 68, wherein the propulsion arrangement is arranged as a pair with a second propulsion arrangement in accordance with any one of Claims 59 to 68, and the engines are spaced apart with facing discharge outlets arranged to form convergent streams which entrain atmospheric air to provide ajet for vertical propulsion.

70. A propulsion arrangement according to Claim 69, wherein the propulsion arrangements are spaced by at least half the diameter of one of the propulsion arrangements but less than twice the diameter of the propulsion arrangements.

71. A propulsion arrangement according to Claim 69 or 70, wherein each of the propulsion arrangements is suspended from a different one of two wings of an aircraft.

72. A propulsion arrangement according to Claim 71, wherein propulsion arrangements are suspended from aircraft wings by connecting wing parts which are inclined upwardly and outwardly from the propulsion arrangement casings.

73. A propulsion arrangement according to Claim 71 or 72, wherein the propulsion arrangements are suspended from wing parts of an aircraft by connecting wing parts which are inclined upwardly and inwardly from the propulsion arrangement casings.

74. A propulsion arrangement according to Claim 71, wherein the propulsion arrangements are suspended from wings of an aircraft by connecting wing parts which are inclined upwardly and outwardly at the rear and by connecting wing parts which extend upwardly and inwardly at the front.

75. A propulsion arrangement according to Claim 74, wherein the propulsion arrangement casings are spaced by a horizontal wing part.

76. A propulsion arrangement according to Claim 75, wherein the horizontal wing part is arranged longitudinally in front of outlets.

77. A propulsion arrangement according to Claim 75 or 76, wherein the horizontal wing part has a flap.

78. A propulsion arrangement according to Claim 70, wherein the engine casings are spaced apart by a distance which is substantially equal to the diameter of an engine casing.

79. A propulsion arrangement according to any of Claims 59 to 78, wherein the outlet is a slot along the propulsion arrangement casing.

80. A propulsion arrangement according to any of Claims 59 to 78, wherein the outlet is a linear nozzle along the propulsion arrangement casing.

81. A propulsion arrangement according to any of Claims 59 to 80, wherein the outlet comprises a row of individual nozzles along the propulsion arrangement casing.

82. A propulsion arrangement for an aircraft comprising a body defining a gas inlet at the front end thereof, a gas outlet at the rear end thereof, and a longitudinal duct running from the front end to the rear end of the body and means to divert or discharge a propulsion jet forwards through the longitudinal duct from the rear to the front of the engine to provide a reverse thrust.

83. A propulsion arrangement substantially as described herein and with reference to one or more of the drawings.

84. An aircraft compnsing a propulsion arrangement or propulsion arrangements in accordance with one or more of Claims I to 83.