GB2143280A - Propulsion device - Google Patents

Abstract

The device is formed by a chamber 11 having an open mouth 12. A fluid curtain is formed across the open mouth and causes increased pressure within the chamber 11, thus driving the chamber by reaction away from the direction of the open mouth. <IMAGE>

Description

SPECIFICATION Propulsion device This invention relates to a propulsion device which can be used, for example, to propel a vehicle in space or in the atmosphere, and to propel vehicles along the ground or lift them off the ground.

The present invention uses a fluid curtain either to propel the vehicle or to lift it. This is in contrast to an air cushion vehicle (ACV) which uses a curtain of fluid such as air to trap a cushion of higher pressure air which lifts the vehicle to a limited height above ground.

According to the present invention there is provided a propulsion device comprising a chamber having an open mouth and means for forming a fluid curtain across said mouth. When the fluid curtain is formed across the mouth, the pressure inside the chamber will be increased and so fluid within the chamber will tend to flow out of the open mouth the chamber and so by reaction the chamber will be forced in the direction away from the open mouth, thus propelling the vehicle.

In order to avoid reactions on the chamber in the direction across the mouth, the curtain can be formed by directing fluid towards a line extending across the centre of the mouth, or towards the central point in the mouth, or tangentially around a central point in said mouth, for example.

The fluid curtain may be formed from apertures directed across the open mouth, the apertures being formed in a second chamber surrounding the first-mentioned chamber at least adjacent said open mouth.

Examples of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a section through a simplified propulsion device, Figures 2A and 2B are diagrams useful in explaining the mode of operation of the apparatus of Fig. 1, Figure 3 is an under plan view and Figure 4 is a central section of another propulsion device, Figures 5 and 6 are central sections through multi-stage propulsion devices, and Figure 7 illustrates another propulsion device.

The simplified propulsion device illustrated in Fig. 1 comprises a chamber 11 having an open mouth 1 2 at its lower end. A second chamber 1 3 surrounds the chamber 11 on all sides except the open mouth 1 2 and is formed with a series of jet slots 14 directed across the open mouth 1 2. Fluid such as air is supplied under pressure to the second chamber 1 3 and emerges from the jet slots 14 to form an air curtain across the open mouth 1 2. The jets forming the air curtain will tend to flow away from the chamber 11, downwards in the figure, and the reaction on the device will drive the device upwards in the figure, away from the open mouth 1 2.

It may be helpful to consider Figs. 2A and 2B to understand the principle of the device and its relationship to the hovercraft device. Fig. 2A shows a wall 21 bounding the ground space 22 and a plenum chamber 23 of half a hovercraft. The plenum chamber 23 has a fluid outlet 24 directed downwards across the open periphery of the ground space 22. When fluid, under pressure, is supplied to the plenum chamber 23, it will flow out of the outlet 24 and since it cannot escape round the wall 21 or the ground space 22, it will tend to flow, by deflection, to the right along the ground 25. Such a machine would not only experience lift but also a force moving it to the left due to the pressure difference between the internal and external faces of wall 21.

In a simple ACV, the plenum chamber 23 and space 22 extend not only to the right of the central wall 21, but also to the left and the central wall 21 may not be present. The outlets 24 create a curtain around the periphery of the vehicle which traps a cushion of higher pressure air, thus lifting the vehicle upwards in the figure, that is in the opposite direction to the flow of air from the outlets 24 and at right angles to the open mouth of the chamber 22. The simple hovercraft extending on both sides of the wall 21 will not be driven sideways because the sideways reaction will be balanced by an equal pressure on the left side of the vehicle.

If one now takes the apparatus of Fig. 2A and provides a symmetrical apparatus below the lower boundary of Fig. 2A as shown in Fig. 2B, one arrives at the apparatus of Fig. 1, turned on its side. In this case there is no further apparatus to the left of the wall 21. In the arrangement of Fig. 2B, the reactions on the device due to the pressure acting on the chamber 22 will cancel out in the vertical direction, but there will be a net reaction on the device forcing it the left in Fig. 2B.

The fluid curtain should be formed across the open mouth 1 2 of the chamber 11, but it need not be directed from one side towards the other. Instead, the air curtain could be directed in a generally circular motion, that is tangentially, as shown in Fig. 3 from a series of jets 31 formed in radial arms 32 extending across the open mouth. The arms 32 can extend in the plane of the mouth, or can extend into the chamber, as shown in Fig. 4. The effect of the fluid curtain so formed is the same as described above, causing increased pressure within the chamber 11 so that fluid will flow from the chamber and the device will be propelled upwards by reaction.

Fig. 5 shows the apparatus of Fig. 1 with a further stage added below it, so that two fluid curtains are formed across the extended chamber, one at its lower end and one at its centre.

The effects of the two fluid curtains are additive and provide increased thrust to the device without increasing its cross section.

Fig. 6 shows an assymmetric arrangement of two air curtains, each formed by jets on one side only of the chamber, the jets of one curtain being directed in the opposite direction to the jets of the other curtain, so that the sideways reactions from the two curtains tend to cancel and the net reaction is an upward thrust.

Fig. 7 shows a section through a series of concentric chambers, each provided with a fluid curtain extending across the open mouth thereof, although in this case the barriers between the chambers are extended below the levels of the fluid curtains. As the arrangement is symmetrical transversely, the transverse reactions cancel out and the net thrust is upwards. Such a propulsion arrangement can be fitted in the under side of an aeroplane wing to provide lift. The fluid for the curtains in this embodiment can be supplied from the wing cavity. The fluid can be pressurised by ram pressure at an appropriate air speed from an opening near the leading edge of the wing to pressurise the interior to supply the curtains. An air pump could alternatively be used.

The fluid used in most applications of the device is conveniently air, since it is readily available, but in spacecraft or submarine applications for example, other fluids may be used.

The chamber 11 does not have to be cylindrical, and its shape can be adjusted to suit its application. In most cases, the shape will be polygonal. Another possible chamber is formed by two opposing walls forming a channel section, with pointed, square or rounded ends.

Referring again to Figs. 2A and 2B, the thrust AT from a section of channel of length AS is equal to the rate of change of momentum of the jets (vertically in the figures) and also to the differential pressure force.

t m' = = 2pVt.S V i.e., #T = 2Q V2 tDS ana: bX = (P - P0) 2r.S #P = Pc - Po Po = #V (t/r), where p is the density and V the velocity of the fluid at the jets, t is the width of the jets, r is the distance from the inner chamber wall to the centre line, Pc is the pressure within the chamber 11 and P0 is the ambient pressure. The power required to maintain this thrust is given by the rate of dissipation of kinetic energy of the jets.

Thus: = Om V = 2 l Vt #S V = e V t#S Then the ratio of power to thrust is given by:

If V is in ft/sec. then P/T2V H.P./TON.

In the device of Figs. 3 and 4, the net thrust is given by: Thrust=T1et +pressure where Tå et = Ghrust due to jets - = zero if injection at 900 I! = momentum thrust relate to pressure pressure = tSm- V maintaining the definition of r (i.e the internal radius in this case), the thrust becomes g = N.k.. t V2 t r where N = number of radial arms kr = length of each jet slot 31.

= = mean jet slot width.

The mean pressure acting on the internal chamber ceiling will be: A P = 2 ('i r2) A p = no\ Q V (t/r) Due to differences of geometry between this device and that in Fig. 1 it is only possible to compare thrust effeciency between specific designs.

The fluid curtain which is directed across the mouth of the chamber is of course directed at an angle to the chamber walls and this angle is usually a right angle when the jets forming the curtain have a component at right angles to the mouth of the chamber, the total propulsion pressure will be the sum of the pressure difference between the interior and exterior of the chamber and the pressure due to this component of the jets. The fluid curtain creates a cushion of higher pressure within the chamber which is contained by the chamber walls.

In contrast to the ACV, the present device may operate at any height and does not require the proximity of the ground, a water surface or any other impermeable surface for successful operation. The propulsion of the device is created by the reaction of the volume of increased pressure on the walls of the chamber and not by reaction with the surrounding atmosphere, so that the device may operate where no atmosphere is present, such as in space.

Since the fluid curtain is across the mouth of the chamber, it is not disturbed by the presence of topographical features and only depends on the pressure of the fluid at the jets and variations in ambient pressure which may be caused by gusts, change of height, for example. As has been illustrated with reference to Fig. 7, the propulsion device may be made in a variety of shapes and sizes and with any number of component sub-chambers. The section of Fig. 7 is equally applicable to a series of parallel channels rather than concentric chambers.

In the steady state, the mass of fluid within the chamber is constant. For a short time immediately after starting, the mass of fluid increases as the chamber pressure is built up. The difference between the chamber pressure and ambient pressure causes the fluid curtain to bend away from the interior of the chamber.

Claims (1)

1. A propulsion device comprising a chamber having an open mouth and means for forming a fluid curtain across said mouth.

2. A device as claimed in claim 1 wherein said means forms said curtain by directing fluid towards a line extending across the mouth.

3. A device as claimed in claim 1 wherein the means forms said curtain by directing fluid towards a central point in said mouth.

4. A device as claimed in claim 1 wherein said means forms the curtain by directing fluid tangentially around a central point in said mouth.

5. A device as claimed in any one of claims 1 to 4 wherein said means comprises a second chamber enclosing the first-mentioned chamber except at the open mouth, the second chamber having apertures directed across the open mouth.

6. A device as claimed in any one of the preceding claims comprising means for forming a further fluid curtain across the interior of said chamber.

7. A propulsion device substantially as hereinbefore described with reference to and as illustrated in Fig. 1 or Figs. 3 and 4 or Fig. 5 or Fig. 6 or Fig. 7 of the accompanying drawings.

CLAIMS (9 Mar 1984)

1. A propulsion device comprising a chamber which is closed except for an open mouth and means for forming a fluid curtain across said mouth.

7. A device as claimed in any one of the preceding claims wherein the means for forming the fluid curtain comprises an air pump.

9. An aircraft comprising a wing and a propulsion device as claimed in any one of claims 1 to 6 and 8, said means for forming the fluid curtain being connected to an opening near the leading edge of the wing to receive air under ram pressure.

10. A device as claimed in claim 2 or any claim dependant thereon wherein said means forms said curtain by directing fluid towards said line from both sides thereof.