Vtol Propulsion System

Abstract

A propulsion system is described which comprises two tip-turbine driven fan units pivotally mounted in a pod. For vertical propulsion the units are respectively registered with vertically aligned inlet and discharge ports in the pod. For forward propulsion the units are swung into registration with a horizontal passageway through the pod.

Description

The present invention relates to propulsion systems and more particularly to an improved system providing vertical take-off or landing capability for aircraft.

While many proposals have been made to provide vertical propulsion for fixed wing aircraft, none had any substantial measure of commercial success. This may be attributed to various shortcomings. Where separate powerplants are employed for vertical and forward propulsion, expense and weight have been prime problems. When vectorable nozzle have been considered, complexity has been a deterrent factor. Where powerplants have been swiveled relative to the aircraft, compromises between the differing aerodynamic requirements for vertical and forward propulsion have made the overall system uneconomical.

In this last regard, it will be noted that forward propulsion is more efficient where a relatively high pressure rise is imparted to the motive fluid stream. For vertical propulsion, a high mass flow in the motive fluid stream is more important than its pressure rise or pressure ratio. Other compromises are also found in the inlet and nozzle areas where the different modes of operation dictate differing configurations.

Accordingly, one object of the invention is to provide an improved propulsion system having a relatively high mass flow for vertical propulsion and a high pressure rise for forward propulsion of winged aircraft.

Another object of the invention is to additionally provide inlets and nozzles which are specifically suited for the differing requirements of vertical and forward propulsion.

These ends are broadly attained by a propulsion system comprising two or more air pressurizing units which pressurize separate air streams for vertical propulsion and a single air stream for forward propulsion.

More specifically, these air pressurizing units are mounted in a pod having a horizontal passageway with a thin edged inlet at one end and a discharge nozzle at its other end. The units have ducts which are registered with vertically aligned inlet and discharge ports in the vertical mode. In the forward mode, these ducts are registered with the horizontal passageway of the pod. The inlet ports may be rounded for efficient vertical propulsion.

Preferably the air pressurizing units comprise fans having tip-turbines driven from remote gas generators. Special features are provided for handling the hot gas discharge from the units and also for transitioning between vertical and forward propulsion.

The above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawings and the novelty thereof pointed out in the appended claims.

In the drawings:

FIG. 1 is a fragmentary perspective view of an aircraft incorporating a propulsion system embodying the present invention and illustrating it in a vertical flight mode;

FIG. 2 is a section, on an enlarged scale, taken on line II--II in FIG. 1;

FIG. 3 is a section, on a further enlarged scale, taken on line III--III in FIG. 2;

FIG. 4 is a perspective view similar to FIG. 1 illustrating the propulsion system in its forward mode;

FIG. 5 is a section taken on line V--V in FIG. 4;

FIG. 6 is a section, on an enlarged scale, taken on line VI--VI in FIG. 5;

FIGS. 7 and 8 are sections similar to FIGS. 2 and 5 illustrating transition between vertical and horizontal propulsion modes; and

FIG. 9 is a section, on a further enlarged scale, taken generally on line IX--IX in FIG. 8.

FIG. 1 illustrates an aircraft 10 which is conventional to the extent that it comprises a fuselage 12 having wings 14 projecting from its opposite sides. Mounted on each of the wings 14 is a propulsion unit comprising a pod 16 mounted beneath the wing. Mounted within each pod are fan propulsion units 18 and 20 which are driven by a pair of gas generators 22 mounted at the forward end of the pod 16.

Each of the units 18 and 20 comprises a central frame structure 24 which is supported on a casing 26. The casing 26 has a central duct 28 and an outer spherical surface 30 which is received by a corresponding surface formed in the pod 16. Trunnions 32 mount the casings for pivotal movement on the pod 16. Actuators 34 are provided to rotate the units 18 and 20 as will later be described.

The units 18 and 20 each further comprise a rotor 36 having fan blades 38 projecting therefrom and outlet guide vanes 40 also supported from the casing 26. The hot gas stream from one of the gas generators 22 is discharged into a longitudinal passageway 42 (FIGS. 3 and 6) and passes through the trunnion 32 to a scroll 44 formed in the casing 26. Scroll 44 directs the hot gas stream to turbine blades 46 secured to the outer ends of the fan blades 38. The rotor 36 is thus rotated so that the fan blades 38 pressurize air entering through the passageway 28 and discharge the pressurized air through the outlet guide vanes 40 to provide a propulsive force. The hot gas stream, after being discharged from the turbine blades 46, is directed through outlet guide vanes 48 and then a concentric outlet passageway 50.

The left fan unit 20 is similarly powered by the discharge of the other gas generator 22 which is directed through a longitudinal passageway 52 to the hollow trunnion of that unit. The construction of the units may be identical and like reference characters are employed to identify like components. It will also be pointed out that the tip-turbine driven fans are well known per se so that further description of these air pressurization devices is not required.

In the vertical mode of propulsion, the units 18 and 20 are positioned with their axes vertically disposed and with their ducts 28, respectively, in registration with inlet ports 54 in the top of the pod 16 and also in registration with discharge ports 56 in the bottom of the pod 16. Cover 58 for the inlet ports 54 is opened in the vertical flight mode by actuators 55 through a mechanical connection 57. Covers 60 for the discharge ports 56 are swung to open positions for the vertical mode by actuators 59 through a mechanical connection 61. It will also be seen that struts 63 support the covers 60.

Referencing next FIGS. 4 - 7, it will be seen that the pod 16 has a central passageway 62 with which the ducts 28 of the units 18 and 20 may be brought into registration by being rotated through a 90.degree. angle of travel. The pressurized air is then discharged from a nozzle 64 formed at the discharge end of the passageway 62. In the forward mode, air pressurized by the fan blades 38 of the unit 18 enters the second unit 20 and is further pressurized. This further pressurized air, along with the hot stream from the outlet 50 of the second unit 20, is discharged from the nozzle 64 to provide the forward propulsive force. The hot stream discharge of the unit 18, through the concentric passageway 50, is directed through a passageway 66 in the pod 16 so that it is angled outwardly along the outer downstream surface of the pod 16. Passageway 66 extends circumferentially around the pod a limited angular distance to prevent discharge of hot gases toward the wing 14.

FIGS. 7 - 9 illustrate transition of the propulsion system from vertical to horizontal operation. The first step is to progressively swing the lower covers 60, which function as vanes or flaps, rearwardly so that a horizontal forward thrust component is produced as illustrated in FIG. 7. Next, the fan unit 18 is pivoted to a horizontal position as illustrated in FIG. 8. The pressurized air from this unit then bypasses the unit 20 by being discharged through passageways 68 formed on the sides of the pod 16. In forward propulsion, flaps 72 are respectively aligned with the flowpath of the pod and the outer surface of the pod. During transition, these flaps are swung open about their upstream pivot points by actuators 74 through a mechanical linkage 76 which is diagrammatically illustrated. Aerodynamic forces could, in some cases, obviate the need of actuators to swing the flaps 70, 72. The passageways 68 function as nozzles so that the air discharged therefrom contributes to the forward thrust of the system.

After the aircraft has gained sufficient forward speed for the wings 14 to provide necessary lift, fan 20 is rapidly rotated into its horizontal posture and then the covers 58 and 60 for the fan unit 20 are closed as are the flaps 70, 72, returning the propulsion system to the position illustrated in FIGS. 4 - 6.

It will be apparent that the described propulsion system provides a high mass flow with a relatively low pressure ratio during vertical propulsion and a higher pressure ratio and lower mass flow for efficient forward propulsion. Further, the inlet and discharge ports 54 and 56 for vertical propulsion are independent of the inlet and nozzle for forward propulsion. This enables the use of bellmouth inlets for better vertical performance and a sharp edge, high speed inlet for better forward performance. Likewise, the discharge ports or nozzles 56 can have the proper area for vertical propulsion while the nozzle 64 has the proper area for forward propulsion. Also, by conforming the covers 58 and 60 to the cylindrical shape of the pod, more efficient forward propulsion is obtained.

While a preferred embodiment has been disclosed, variations thereof within the broader aspects of the invention will occur to those skilled in the art. For example, the fan or air pressurizing units could have self-contained gas generators, as for example, after the nature of a turbofan engine, or in certain aspects a turbojet engine. Dependent on the aircraft configuration, there could be one or a number of propulsion systems and the pod could have other than a cylindrical shape. The pod could contain any number of propulsion units similarly arranged.

In transitioning, the rear fan unit could be in a horizontal position while the forward unit is in a vertical position. In this case, the forward unit would be aerodynamically bypassed by opening passageways in the pod to introduce air to the second unit.

Claims

Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:

1. A propulsion system comprising:

a pod having a horizontal passageway therethrough with an air inlet at one end, a nozzle at the other end, and first and second pairs of vertically aligned inlet and discharge ports opening to and from said horizontal passageway, said pairs of ports being spaced apart intermediate the inlet and nozzle, the inlet ports being formed on relatively large radii after the nature of a bellmouth, and the inlet to said pod passageway being relatively sharp for efficient entry of air at high speed forward propulsion,

first and second air pressurizing units, each having a duct through which air flows as it is pressurized, and

means for selectively registering the ducts of the first and second units respectively with the first and second pairs of ports for vertical propulsion and registering the ducts of both units with the horizontal passageway for forward propulsion.

2. A propulsion system as in claim 1 wherein:

the means for selectively registering said ducts includes means for pivotally mounting said units on said pod and means for pivoting said units on their pivots between vertical and horizontal positions.

3. A propulsion system as in claim 2 further comprising:

vane means in the discharge port which are pivotally mounted about axes perpendicular to the direction of forward thrust,

means for pivoting the vanes from a generally vertical position when the pressurizing units are in a vertical position to an angled position in transitioning from vertical propulsion to horizontal propulsion;

means for pivoting one of said units to its horizontal position during such transition while the other unit remains in a vertical position blocking said horizontal passageway, and

means for aerodynamically bypassing the horizontal unit past the vertical unit during such transition.

4. A propulsion system as in claim 3 wherein:

said one unit is the upstream pressurizing unit moved to a horizontal position during transition, and

the bypassing means comprise passageways extending at a low angle through said pod to its exterior intermediate said units, flap means normally closing the bypass passageways and means for swinging said flap means outwardly to provide said bypass function.

5. A propulsion system as in claim 2 wherein each of said units comprise a casing and

the means for pivotally mounting said units includes trunnion means having axes disposed at the intersection of the axes of said pod passageway and said ports, and

further including

means for sealing said unit ducts from said ports when they are registered with said pod passageway and sealing said ducts from said pod passageway when they are registered with said ports.

6. A propulsion system as in claim 5 wherein:

the pod, its passageway, the ducts and ports are circular in cross section; and

the sealing means are spherical.

7. A propulsion system as in claim 2 wherein:

each of said units comprises a casing, a gas generator mounted remotely therefrom, a fan rotor having a tip-turbine, means for ducting hot gases from the gas generator to the tip-turbine and an annular discharge from the tip-turbine for the hot gases,

and further including

passageway means in said pod with which the annular discharge of the upstream unit is registered in the horizontal position of the unit, thereby discharging the hot gases thereof to the exterior of the pod, and

the annular discharge of the downstream unit is registered with the pod passageway in the horizontal position of that unit.

8. A propulsion system as in claim 7 wherein:

the pod, its passageways, the ducts and the ports are circular in cross section,

the inlet ports are formed on a relatively large radii after the nature of the bellmouth,

the inlet to said pod passageway is relatively sharp for efficient entry of air at high speed forward propulsion,

the means for pivotally mounting said units includes trunnion means having axes disposed at the intersection of the axes of the pod passageway and said ports, and

further including

spherical means for sealing said unit ducts from said ports when they are registered from said pod passageway and sealing said ducts from said pod passageway when they are registered with said ports,

covers for said ports which conform to the outer surface of said pod,

means for pivoting inlet port covers to open positions when the units are in their vertical positions, means for pivoting the discharge port covers about axes perpendicular to the direction of forward thrust when the units are in their vertical positions,

means for pivoting the discharge port covers in a rearward position toward a closed position so that they function as vectoring flaps in transitioning between vertical and horizontal propulsion,

means for pivoting the upstream unit to a horizontal position during such transition while the other unit remains in a vertical position blocking said pod passageway,

bypass passageways extending at a low angle through said pod to its exterior intermediate said units to direct the fan discharge from the upstream unit to the exterior of the pod during transition,

flap means normally closing the bypass passageways and

means for swinging said flap means outwardly to provide said bypass function.