WO2005003545A1

WO2005003545A1 - Propulsion system

Info

Publication number: WO2005003545A1
Application number: PCT/GB2003/002837
Authority: WO
Inventors: Nicholas Paul Robinson
Original assignee: Nicholas Paul Robinson
Priority date: 2003-07-02
Filing date: 2003-07-02
Publication date: 2005-01-13
Also published as: AU2003304285A1

Abstract

A universal jet propulsion device featuring a longitudinally mounted flipper-fin housed in a laminar baffle manifold with flap valves provides environmentally friendly operation when deployed as an aerospace propulsion system or a fluid pump. It is able to extend the flight envelope when deployed in an airborne system by using its ultra-low turbulence full-wave action and extensible manifold geometry to maintain inlet overpressure in thin air near sub-space. By deploying the action of manifolded fuel-air combustion against alternate sides sequentially to cause the flexing of the flipper, powerful thrusts can be achieved in water and air.

Description

PROPULSION SYSTEM

The present invention relates to a propulsion system, and in particular to a system for propelling fluid. Such a propulsion system may be used to pump fluid, or for generating thrust for moving an object to which the propulsion system is attached.

Various pumps for pumping fluid are known. Most of these are based on a rotating armature. However, for small volumes, other types of pump or motor may be used, such as a piezoelectric pump, peristaltic pump or ion motor. There are limitations with the use of such pumps. Rotating armature pumps require lubrication and are liable to cause turbulence. High power densities are also difficult to implement at a small scale. Piezoelectric pumps and ion motors may overcome some of these problems, but conversely cannot be implemented on a larger scale.

Various systems are known for moving vehicles using a propulsion system. Conventionally, propellers have been used both for marine applications and aircraft. In the marine environment, conventional propellers systems are limited to the power and speed available under load to 60% at the onset of cavitation. Flipper propulsion systems have been proposed which have been found more efficient than conventional propellers systems.

For aircraft, jet engines are known. With the jet engine, compressed gas is introduced into the engine, and the compressed gas is expanded rapidly by combustion of fuel within the compressed gas. The rapidly expanding gas is then used to drive a turbine. It is known to couple the turbine to an inlet fan to enhance the input of gas into the engine, in a turbofan arrangement. RAM jet engines are also known. Whilst each of these types of engine have advantages in certain circumstances, they also cause disadvantages in other circumstances. For example, conventional jet engines are complex, requiring many parts to be moved at high speeds whilst under high stress. This means that such engines are expensive to manufacture, and are liable to catastrophic failure. Conventional jet engines are limited to operation up to 60,000 ft. due to the turbulent nature of the thrust generation and high venturi temperatures, pressures and speeds. RAM jet engines require a very high inlet velocity in order to start, and therefore their use in a "single stage" propulsion system is limited.

According to a first aspect of the present invention, a jet engine comprising an inner manifold include an inlet portion and an outlet portion and a flipper, one end of which is pivotally mounted towards the inlet portion of the manifold, and an intermediate part of which is pivotally mounted within the manifold, the pivots lying substantially centrally with respect to the manifold, the flipper being operable in a scoop-swallow-wallop cycle to scoop and compress fluid into an inlet manifold via an inlet valve, the flipper being pivoted in the opposite direction to allow the compressed fluid from the inlet manifold though the outlet to produce a jet of fluid.

The jet engine according to this aspect of the present invention has been found to be more efficient than other known jet engines in a greater range of environmental conditions.

Advantageously, an ignition means is provided to ignite the compressed fluid in the inlet manifold, causing this to expand thermodynamically to jet the fluid from the outlet. A fuel injection means may also be provided for injecting fuel into the inlet manifold for combustion of the compressed fluid. In this case, the expansion of the compressed fluid within the inlet manifold causes the pivoting of the flipper in the opposite direction. Alternatively, steam can be injected into the compressed fluid to cause its expansion.

Advantageously, the inlet valve is biased towards a closed position, thereby opening only when the pressure of compressed fluid from the flipper reaches a predetermined level. In this case, the bias of the inlet valve is advantageously adjustable.

The engine advantageously includes an outer manifold around the inner manifold, the outer manifold being defined by outer manifold side walls. This can help enhance the ram effect to enhance the efficiency of the jet. In this case, the tail of the flipper is preferably arranged to be able to close the outer manifold.

To control the efficiency of the engine, for example at different ambient conditions, the size of the inner and/or the outer manifold is variable by movement of the inner and/or outer manifold walls. This may be achieved by providing the inner and/or the outer manifold side walls on a scissors mechanism for movement with respect to the centre of the manifold.

In an alternative example, the jet engine further comprising a means for moving the flipper between opposite positions. The means may be a motor which could be connected to one of the pivots of the flipper to move the flipper between its opposite positions. With this arrangement, no combustion of the fluid is required within the manifold. This means that the engine can operate in fluid that is not combustible, for example in water.

According to a second aspect of the present invention, a turbojet compressor for providing compressed gas to an internal combustion engine, comprises an inner manifold include an inlet portion and an outlet portion, a flipper, one end of which is pivotally mounted towards the inlet portion of the manifold, and an intermediate part of which is pivotally mounted within the manifold, the pivots lying substantially centrally with respect to the manifold, and an internal combustion engine including a piston cylinder, the flipper being operable in a scoop-swallow-wallop cycle to scoop and compress fluid into the piston cylinder via an inlet valve, the fluid being combusted within the piston cylinder to drive a crank shaft of the engine.

The internal combustion engine may be a twin-cylinder engine.

Advantageously, the crank shaft of the internal combustion engine is coupled to move the flipper between opposed positions. This provided the force for movement of the flipper. The crank shaft may be connected to at least one of the pivots.

The fluid is advantageously supplied to the piston cylinder via an inlet manifold, the inlet manifold being in the form of a funnel to compress the fluid as this is supplied to the piston cylinder. The inlet manifold may be angled with respect to the centre line of the compressor to assist with the collection of fluid when moving through the fluid.

Advantageously, at least one of the pivots, preferably the leading pivot, is a floating head pivot. This assists the movement of the leading section of the flipper between its extreme positions.

The flipper may be formed of a resilient material, such as spring steel, or a nicromat alloy. Alternatively, the flipper may be formed in a number of segments which are connected together with a resilient means to give the required flexibility of the flipper. In this case, the resilience of the resilient means is preferably adjustable depending upon the application of the engine, the fluid in which this is being used and other similar factors.

The flipper may include an anti-oxide coating.

Cooling means are preferably provided to cool the flipper in use. The cooling means may comprise channels for cooling fluid which can be formed on or in the flipper, and which may carry a cooling fluid such as liquid sodium or water.

According to a third aspect of the present invention, an engine comprises a manifold, a flipper pivotally mounted for movement between a first position and a second position within the manifold to jet fluid out of the manifold, and a means for moving the flipper between the first and the second position, in which the side walls of the manifold include at least one one-way valve for allowing fluid to enter the manifold through the at least one valve, whilst preventing the flow of fluid from the manifold through the manifold side wall.

Advantageously, a plurality of valves are provided on each side wall of the manifold to assist with the inlet of fluid into the manifold. The or each valve may be flap valves.

According to a fourth aspect of the present invention, a pump comprises a channel along which fluid is to be pumped, and a flipper mounted within the channel, the flipper including a fixed end and a free tail extending downstream within the channel, and a means to move the tail of the flipper between a first position substantially adjacent one side of the channel and a second position substantially adjacent the other side of the channel to pump fluid along the channel. Advantageously, the flipper is arranged to ripple along its length, thereby propelling fluid along the channel.

The device can be assembled from three Si wafers bonded together in a vertical planar, wafer-bonded sandwich using known techniques. The flipper is made by etching from the central component using standard methods used in MEMs technology, coated by either a magnetic or piezoelectric layer on either or both sides.

The flipper preferably includes at least two layers of different material or differently doped material, such that the application of a current across the flipper causes the flipper to move between the first and second positions. For example, the flipper may be formed with a n-type core and p-type layers on either side of the core, or with a p-type core and n-type layers on either side of the core.

The flipper may be moved or rippled using a piezoelectric effect, magnetism or in other ways.

According to a fifth aspect of the present invention, a gated charge pump provides for switched flow in two alternate directions. The flipper has a ripple flex action which pumps fluid through the device in metered quantities by counting the number of ripple flexions. The ripple-flex action is induced by piezoelectric flipper actuation as described, but at a frequency above its natural resonance in the propelled fluid, i.e. above its "S" point, creating an eel-like motion or ripple action. This rippling action is reinforced by electromagnetic fields acting on the collector wire and tail wafers produced by the embedded printed circuit coil "stator" in the manifold walls. When the device switches to the alternative gate for selective pumping, the electromagnetic field is reverse-biased, i.e. a DC offset component added or subtracted to the AC current causing the assisted ripple flexing. This causes the tail to vector its thrust and point it towards the alternative gate.

By providing a magnetic field around the tail end of the flipper, for example using at least one electromagnet arranged near the tail end of the flipper to generate the magnetic field, the movement of the flipper can be controlled.

Various features associated with different aspects of this invention may usefully be combined.

The present invention will be described with respect to the accompanying drawings, in which:

Figure 1 shows a sectional view through a jet engine according to a first aspect of the invention;

Figure 2 shows a sectional view of an alternative example of a jet engine according to the present invention;

Figures 3a and 3b show alternative manifold positions;

Figure 3c shows an arrangement of multiple engines;

Figure 4 shows a sectional view of a turbojet compressor;

Figure 5 shows a sectional view of a turbojet compressor; Figures 6a-c shows a perspective view of a pump;

Figures 7a and 7b show sectional views of a flipper;

Figure 8 shows a gated charge pump;

Figure 9 shows a sectional view of a flipper pump;

Figure 10 shows a sectional view through an aqua-jet motor; and

Figure 11 shows a sectional view of a pump for arrangement in a blood vessel.

The present invention relies on the flexing of a flipper member to propel fluid along an opening or manifold in which the flipper member is provided. The flexing of the flipper member is achieved by various stimuli, dependent upon the application of the propulsion device.

A first example of a propulsion system according to the present invention will be described with respect to a jet engine as shown in Figures 1 to 3. In this case, the flexing of the flipper is achieved by the rapid expansion of compressed gas when this is combusted in a combustion chamber, assisting the jetting of gas from the rear of the device. This jet of gas produces thrust.

The engine comprises an outer manifold side wall 1 defining an outer manifold 2 having a central axis 3, and an inner manifold side wall 4 defining an inner manifold 5. Inner manifold throat baffles 6 are provided within the inner manifold 5. The arrangement of the manifolds is generally symmetrical along the central axis 3. The opposite sides of the axis 3 will be referred to the left side (below the axis as shown in Figure 1) and the right side (above the axis as shown in Figure 1). However, this notation should not be construed as limiting the orientation of the device. First valve members 7, in the example shown in the form of a flap valve, are mounted towards the leading edge of the left and right sides of the inner manifold side wall 4, and are biased to close against the respective inner manifold throat baffle 6 by biasing means 9 such as a spring. The spring bias may be adjustable. However, the valve will typically close when the pressure within the combustion chamber is equal to or greater than that in the inner manifold inlet. Each inner manifold side wall 4, and respective first valve member 7 and inner manifold throat baffle 6 define a respective combustion chamber 10 to be described below. A fuel injector 11 and ignition means 12 are directed into the combustion chamber 10. An optional second valve member 8, in the example shown a second flap valve, is mounted on the trailing end of the inner manifold throat baffle 6.

The system also includes a flipper 20, for example formed of a material such as nicromat alloy. The alloy may be precision cast, and may include an aluminium anti-oxide coating. To allow cooling of the flipper, this may include cooling tubes which are preferably internally cast. The cooling tubes may contain a cooling medium such as liquid sodium or water. The flipper 20 is pivotally mounted within the system by a pivot 21 provided on the central axis 3 of the inner and outer manifolds, the pivot 21 lying generally perpendicular to the central axis 3. The leading edge of the flipper 9 is also pivotally mounted on the central axis 3 with a floating head pivot 22 perpendicular to, and able to move along, the central axis 3. Where the second valve member 8 is omitted, a sealing member 23 is provided on the flipper 20 to seal the flipper 20 against the inner surface of the inner manifold throat baffle 6 as described below. The sealing member may be included where the second valve member 8 is retained. In use, as shown in dotted lines in Figure 1, the trailing end of the flipper 20 closes the rear of the left combustion chamber 10 between the left inner manifold throat baffle 6 and the left inner manifold side wall 4. The trailing end of the flipper 20 also engages the left outer manifold side wall 1 , thereby sealing the left outer manifold 2. At the same time, the left first flap valve 7 is closed by the combination of the biasing means 9 and a higher pressure within the left combustion chamber 10 than in the inlet left inner manifold 5. The gas within the combustion chamber 10 is thereby compressed. Fuel is then injected into the left combustion chamber 10 though the fuel inlet 11 , and the resulting mixture of fuel and gas is ignited within the combustion chamber 10, causing the rapid expansion of this gas. This is illustrated in dotted lines in Figure 1 which shows the progressive expansion of the gas as this is exhausted from the manifold 5. The exhaust gas may be at temperatures in excess of 1000°C, typically of around 1200°C. The increase in pressure of the gas within the combustion chamber 10 as this is forced though the trailing end of the combustion chamber 10, causes flexing the trailing end of the flipper 20 away from the rear end of the left combustion chamber 10. A seal 23, which is shown in the form of a barb, between the flipper 20 and the inner surface of the left inner manifold throat baffle 6 prevents the expanded gas passing between the flipper 20 and an inner surface of the left inner manifold throat baffle 6, and accordingly all of the gas is forced out of the rear of the manifold, creating forward thrust. Where a second valve member 8 is provided, the may close against the flipper to create a seal. The force applied to the trailing end of the flipper 20 by the rapid expansion of the gas in the combustion chamber 10 causes the trailing end of the flipper 20 to whip across the inner manifold 5 about the pivot 21 , closing the rear of the right combustion chamber 10 on the opposite side of the central axis 3 and compressing the gas within the right combustion chamber 10 to repeat the process. During the flipping of the trailing end of the flipper 20 from the left side to the right side, the leading end of the flipper 20 flexes about the pivots 21 and 22 in the opposite direction. Particularly, the leading end of the flipper 20 moves from the right side to the left side, and in doing so straightens initially, causing the floating head pivot 22 to move forward. As the leading end of the flipper 20 passes the central axis 3, this bends, causing the floating head pivot 22 to move rearwards. By limiting the sliding movement of the floating head pivot 22, the degree of flexing of the flipper 20 can be regulated. This movement causes a reduction in the pressure in the right inlet manifold in the region of the right first flap valve 7 of the right combustion chamber 10 which, in combination with the action of the biasing means 9 causes the right first flap valve 7 to close, enabling the compression of the gas in the right combustion chamber 10.

At the same time, the pressure in the inner manifold 5 around the left first flap valve 7 of the left combustion chamber 10 is increased, causing the left first flap valve 7 to open against the bias of the biasing means 9. This assists with the exhaust of gas from the left combustion chamber 10. Also, the leading portion of the flipper 20 scoops gas and forces this into the left combustion chamber 10 so that this gas can be compressed by the action of the trailing end of the flipper 20 when the movement of the flipper 20 is reversed.

Further, the flow of gas through the left inner manifold will help cool this, reducing thermal stress.

The action of the leading end of the flipper 20 in flexing to force fluid toward the combustion chamber is referred to as the "scoop" phase. This is followed by a "swallow" phase preceding the combustion of gas in the opposed chamber, during which fluid flows through the inner and outer manifolds. The phase when the gas is combusted, causing the tail of the flipper to whip to the opposite side of the manifold is referred to as the "wallop" or "stroke" phase. Accordingly, the complete action of the flipper is referred to as "scoop- swallow-wallop" cycle.

It will be appreciated that the gas is alternately compressed and combusted in the opposite sides of the inner manifold 5, giving a reciprocating action.

With this arrangement, the outer manifold 2 functions to increase the thrust generated by the engine by increasing inlet ram airflow collection, exhaust gas compression and inlet-to-outlet gas flow with bypass mixing and cooling. As described above, the flipper 20 partially closes the trailing edge of the outer manifold 2 during the "swallow" phase, as the exhaust gases are exhausted from the inner manifold. This optimises rearward thrust generation. It also acts to maximise the pressure differential between the combustion chamber and the inlet inner manifold around the first valve 7, and thereby assists with the efficient opening and closing of the valve member. This is especially important at high inlet airspeed to maximise inlet air collection in thin air and to keep drag low.

An alternative arrangement is shown in Figure 2, in which like parts are given the same reference as in Figure 1. In this example, the outer manifold side walls 1 are adjustable, for example including a variable geometry scissors mechanism 30, adjustable by an actuator 32. By adjustment of the position of the outer manifold side walls 1 , the thrust may be controlled dependent upon the environmental conditions. For example, where the engine is used for an aircraft, this can provide low speed thrust for takeoff and landing, and maintain thrust in thin air by expansion of the outer manifold 5 by outward movement of the outer manifold side walls to a position 1¹ as shown in Figure 2. The position of the inner manifold side walls may similarly be adjusted. The engine according to this aspect of the invention is able to operate at a lower manifold pressure compared to a conventional jet engine turbine, but with a larger aperture. This results in lower venturi speeds and lower operating temperatures. In turn, this leads to a reduction in stress on the components, and thereby a reduction in cost.

The scissors geometry manifold is shown in more detail in Figures 3a and 3b. In Figure 3a, the manifold is open to its maximum extent, causing the maximum amount of air to be collected into the manifold. This helps maintain the required overpressure and hence thrust in thin air. With this arrangement, a large displacement of the flipper is required as this moves from one side to the other. In this case, variable geometry wings 40 of an aircraft are shown extended for high altitude flying to maintain lift in thin air. Figure 3b shows the manifold in a narrow condition. This is suited to low altitude applications, including aircraft takeoff and landing, or when operating at high velocity, for example on re-entry to the atmosphere. In this example, the wings 40 are shown non-extended.

It is important that the engine components are sufficiently cooled. This may be achieved by airflow cooling of the inner manifold side walls by airflow passing through the outer manifold. The flipper may be cooled by internal tubes or coils within the flipper containing a cooling medium, or by cooling fluid extending along the flipper, for example from the main pivot.

Figure 3c shows an end view of an arrangement of multiple propulsion devices arranged in a stacked configuration. The multiple devices may be operated with different phase cycles. This produces a more continuous level of thrust. Also, the cycle time, and in particular the "swallow" phase, can be increased, thereby aiding cooling. Components may be shared with this arrangement, for example each of the flippers may share a commonly geared central pivot and manifold footprint. Rather than injecting fuel into the combustion chamber and igniting the resulting mixture, steam can be injected into the compressed fluid causing the expansion of this.

To operate at maximum output, which is limited by the full wave resonant frequency of the flipper-manifold system, the resonant frequency should not be exceeded, otherwise the flipper will exceed its "S" point and will resonate at harmonics. This can be overcome by including adjustable stiffeners in the flipper as shown in Figure 10.

In another example, generally similar to that shown in Figures 1 to 3, the flipper is driven between its two positions by an engine, for example a twin cylinder opposed four-stroke reciprocating piston engine. The engine can be mounted to share its crank axle with the main pivot axle of the flipper. In this arrangement, the combustion features may be omitted. As no combustion of compressed fluid is required, this arrangement is suited to use with non- combustible fluids, such as water. In this case, the flipper is preferably formed of a spring steel sandwich composite, preferably with incorporated cooling means, such as cooling coils. Many of the features of the first embodiment may be used with this example, including the floating head pivot and features of the flipper and adjustable manifolds.

As the engine causes the flipper to move from one extreme position to the other extreme position, the leading end of the flipper will flex about the two pivots from its concave position to its convex position, "scooping" fluid and forcing this into an inlet manifold. By variation of the diameter of the manifold between inlet and exhaust, suitable compression and jetting can be achieved. The inlet manifold is connected to an exhaust manifold on the opposite side, which is closed by the tail of the flipper. Accordingly, fluid will be introduced into and compressed within the manifold. When the tail of the flipper is moved by the engine, the compressed fluid will be propelled from the exhaust manifold. In typical conditions, the fluid may be at a temperature of around 600°C. At the same time, the tail of the flipper will seal the opposite exhaust manifold, whilst the movement of the leading end of the flipper will scoop fluid into the opposed inlet manifold. During the "swallow" phase of the movement of the flipper, namely the phase between movement of the flipper between the two extreme positions, substantially uncompressed fluid will flow around the exhaust manifold, assisting in the cooling of the flipper and manifold. This helps reduce heat stress. This example acting as a compressor provides enhanced aspiration for the coupled IC piston engine for providing improved mechanical shaft output and/or thrust generation.

A further example of the use of the present invention, as shown in Figures 4 and 5, is as a turbo-jet compressor. Such a compressor may be used to enhance gas flow, such as air, into an internal combustion engine, and for thermodynamically expanding the exhaust gas of the engine through opposite cylinders with this arrangement, the flipper is driven between its extreme positions. Advantageously, part of the internal combustion engine's crank motive power is used to drive the compressor. Features of the previous examples including the floating head pivot, features of the flipper, and the adjustable manifolds may also be used in this example. With this arrangement, the combustion occurs within a cylinder as opposed to being within the manifold. This improves cooling and the generation of shaft power, and increases the inlet air compression ratio and combustion efficiency, whilst reducing the heat stress on the flipper.

A twin cylinder implementation is described with alternate flipper air cooling cycles. As shown in Figure 4, there is provided an inlet manifold 204 for an internal combustion engine. A flipper is provided that may move from a first extreme position shown in solid lines with reference 202 to a second extreme position shown in dotted lines with reference 209. Scooped ram air 201 or other fluid is compressed by the leading end of the flipper as this is flexed from a concave to a convex orientation with respect to the left hand side of the system. The compressed air is accelerated through the inlet manifold 204 which has a reducing diameter 205, and into the cylinder cavity 206 of the internal combustion engine, passing through an inlet valve 210. The compressed air is thought to remain at a constant pressure as this is forced through the manifold. As the flipper is moved in the opposite direction, air is compressed and accelerated into the opposite inlet manifold.

The air within the cylinder is compressed further within the cylinder by the piston in its compression stroke, during which the inlet valve 210 is closed.

As shown best in Figure 5, the compressed air within the cylinder is ignited, causing its rapid expansion, which drives the piston in the internal combustion engine 225, rotating a crank shaft 230 connected to the piston in the normal manner. In the example shown in Figure 5, the crank shaft is used to drive the flipper between its two extreme positions, thereby scooping and compressing air into the piston chambers of the internal combustion engine.

Exhaust gas from the piston chamber is exhausted through an outlet valve, though an outlet manifold 224 and out of the rear of the system as exhaust gas 229. This exhaust of gas is aided by the flow of gas over the flipper.

In this example, the inlet manifolds are angled rearwards to ensure that the maximum amount of air is scooped into the manifolds. The position and angle of the manifolds may depend upon the velocity of the air flow into the inlet manifold of the system.

The "scoop-swallow-wallop" cycles of the flipper cap to a four-stroke compression-power-exhaust-induction cycle of the internal combustion engine as set out below:

It will be appreciated that rather than using the drive from the crank shaft, the exhaust gas from the system may be used as a jet of fluid for the propulsion of a device.

Another example of the present invention is shown in Figures 6 and 7.

In this example, a flipper 119 is mounted in a channel 112. The leading end 116 of the flipper 119 is fixed, whilst the trailing end or tail of the flipper 119 is free. In use, the tail of the flipper 119 is flexed to propel fluid along the channel 112.

The pump or motor according to this aspect of the present invention is especially suited to miniaturisation. In this case, as shown in Figure 6, the device may be formed from a semiconductor wafer 111 into which a flow channel 112 is formed, for example by etching. The tapered flipper 119 is formed within the channel 112. In a preferred example, the flipper 119 is formed from the semiconductor wafer during the etching of the channel 112, with the tail of the flipper 119 being undercut from the wafer by burning, lasering, etching or other means. The flipper 119 is tapered from the fixed leading end 116 to the tail 119. However, the flipper 119 may be formed from three layers bonded together using standard wafer bonding technique. The flipper may be coated with piezoelectric or magnetic layers.

The flipper 119 has a p-type doped core 113 sandwiched by outer n-type doped skins 114, 115 acting as cathodic outer skins, as shown in the cross- section of Figure 7b. The doping of the core 113 and the skins 114, 115 may be reversed. An anode 118 is provided at the tail end of the flipper 119, connected to a collector wire 121. Rather than the p-n-p or n-p-n structure, a simple p-n structure formed from two rather than three layers may be used.

As shown in Figure 7a, due to the piezoelectric effect caused by the different doping of the core 113 and skins 114, 115, when the flipper 119 is flexed, it is believed electrons (-) and/or holes (+) will migrate along the rippling surface wave to the end of the flipper 119 where they are collected by the anode 118. The application of a lateral alternating current to the outer surface skins 114, 115 of the flipper 119, for example being applied to the outer skins of the flipper 119 at the fixed leading end 116 will cause the flipper 119 to flex. This flexing of the flipper 119 acts to pump fluid in the channel 112.

The propulsion of fluid may be controlled. The piezoelectric effect may be enhanced, or the propagation of holes and electrons controlled, by the application of a magnetic field across the channel 112. As shown in Figure 6, an electromagnetic field may be applied across the channel 112 by the use of coils on the side walls of the channel 112, for example through printed circuit coils. The advancing wave front of the flipper 119 (as shown by the arrow 101 in Figure 7) is thought to react against the electrostatic field, propelling electron concentrations and/or holes rearwards (in accordance with Fleming's Hand Rule).

Preferably, the flipper 119 is made to ripple along its length, rather than merely flap. This is achieved by a short wavelength deformation of the flipper 119.

As shown in Figure 8, the device may be used in a gated charge pump. In this case, there are provided two outlet paths, 131 and 132. The flipper 119 is able to be moved by an alternating power 137 applied to the skins 114, 115 of the flipper 119, with an anode voltage offset provided by a battery 138. In this case, as the tail end of the flipper 119 contacts the walls 135, 136 of the outlet, charge is collected from the exposed anode 118 on the tail of the flipper 119.

Other mechanism for movement of the flipper may include use of the Hall effect, or remote magnetic actuation by a stator containing field coils 130, 140 which enhance piezoelectric charge cluster propagation along the flexing flipper.

Ideally, the flipper of this pump is provided with a leading end that is moved opposite to the tail, as described with the earlier aspects of the invention. This provides the "ripple-flexing" action to improve the propulsion of fluid. The switch 131 , 132 provides a DC offset to the stator coil 130 to move the ripple- flexing flipper to alternating gates 131 , 132. Flap valve 135 pivot to guide fluid flow, and can snap shut to prevent flow reversal.

Small pumps of this type have many applications, including medical applications.

As shown in the sectional view of Figure 6b, three wafers are stacked above a chip substrate. The flipper is etched out of the middle section using MEMs techniques, leaving a channel. In this figure, the dotted line shows the direction of flipper flexion. Figure 6c shows a plan view of the planar bonded water assembly.

A semiconductor wafer actuated by a piezoelectric force causes ripple flexing when placed in a fluid and operated above its resonant frequency which is believed to cause charge migration along its rippling surface to be collected at its tail.

Another embodiment of the present invention is for a "short engine" comprising a valve-manifolded flipper that operates a "swallow-wallop" cycle. The short engine comprises a middle section "throat" with a short inlet manifold and a rear end in which a pivoting flipper operates a swallow-wallop cycle.

The short engine lends itself to macro-scale marine applications, where the fluid to be propelled is not required to be highly pressurised or is not compressible.

As shown in Figure 9, an outlet 501 with flap valves in its delta side walls 505 that open 504 on retreating sweep strokes of the flipper 503 and close on advancing strokes of said flipper 502, creates reactive manifold thrust 506 whilst presenting a low-drag surface to passing water 507 on alternate sides of it main axis X-X. The pivot of the flipper 508 is placed ahead of the throat or neck of the manifold 509 at or about its apex. As the flipper advances to one side, it forms a valve with the throat and manifold wall 510, compressing fluid rearward to create thrust 506. As the flipper retreats, the throat valve and the manifold wall valves open to allow fluid to fill the opening cavity 511. This is the swallow stroke. The wallop stroke is performed on opposite sides of the flipper in sequence to provide thrust. The wallop stroke is the counterpart of the swallow stroke, occurring simultaneously on opposite sides of the flipper. As the water speed increases, the ram effect against the sides of the outlet manifold 512 forces more water through at overpressure to increase efficiency and reduce drag 507.

The motor contains a middle section with a main powered flipper pivot and a short inlet manifold 509 (the throat) through a small quantity of rapidly-moving ram-inlet water 513 flows along alternate sides along the flipper. The flipper may be powered by any suitable source. Figure 10 shows the motor in a marine twin-hulled "aqua-jet" application with a remote IC engine and gearbox 551 , a reciprocating main pivot gearhead 554, fixed and/or variable manifold wall geometry 552, manifold wall-pivoting adjustment mechanisms 555 and an adjustable flipper spring stiffener mechanism 553. As inlet water speed increases 556, the manifold wall displacement and flipper displacement can be fixed or vary with flipper frequency.

A final example of the present invention is described with respect to Figure 11 which shows a pump for pumping blood. In this example, propulsion system acting as a blood pump are mounted at various locations within the patients circulatory system to aid circulation and prevent blood pressure anomalies causing plaque detachment, clots, arterial collapse and blood pooling. In addition, it can be used outside the patient's body to act as a blood pump for open heart surgery to replace the function of the "ro-ro" peristaltic pump, a portable dialysis machine or for patient controlled drug administration. The unit derives its power from opposing muscle groups inside the body squeezing the manifold and flipper against its valves, expansion of the upper torso during breathing and/or from joint flexing. It can be worn around a limb or the torso or located deep inside the brain by remote insertion through the carotid arteries (like an angioplasty for example) to provide protection from stroke caused by blood pressure anomalies.

For implantation to treat pre-stroke victims, the unit is based on the "short engine" example as described for the marine application. The flipper is powered remotely by actuator coils implanted in the patient's head via keyhole surgery. By remote actuation (through the walls of the blood vessel), the requirement to cut through vulnerable blood vessels deep inside the brain is avoided. The unit "flaps" in normal blood flow and this is detected by the "normally-off" field coils. When blood flow ceases, the coils are energised. The flipper is analogous to a "moving-magnet" armature in brushless electric motor with field coils acting as the "stator". Control circuitry is not shown but it is of the existing type associated with brushless motors. Having no rotating parts eliminates the requirement for lubricants and joint wear.

For use outside of and/or attached to the body, the units outlet manifold walls containing flap valves are made flexible to deform with changing limb or torso curvature and circumference. Increasing circumference forces the nearest manifold against the central flipper closing its valves and pumping blood as described. Releasing internal pressure causes the manifold walls to spring back open, inducing fresh blood into the opening cavities through opening flap valves.

Figure 11 shows the blood bags pumping on an expanding body belt. The action of a single blood pump 101 is described first. Like a concertina bellows, the bag contains an outlet manifold which can be pressed from the inside by the wearer to fold its sprung bellows towards the body belt, which acts as the stationary flipper in a pivoting manifold 104. Blood is pumped through this squeezing action caused by the inhalation of the wearer for example 105. The inlet pressure builds up forcing the valves on the far side 107 to open into the expanding cavity 108 and vice versa on contraction caused for example by the exhalation of the wearer. The output of the first bag 110 is coupled to the inlet of the next blood pump bag 111 and so on in cascade.

Blood is induced from natural blood pressure through inlet valve 111. Blood emerges pumped from valve 112 to be returned to the body. Filtering and other blood treatments can be carried out en route through the body belt. As an implant, one or more blood bag pumps can be inserted between opposing muscle groups in the limbs which on contraction and/or relaxation and/or co-contraction can administer a patient controlled drug intravenously (PCD).

Claims

1. A jet engine comprising an inner manifold include an inlet portion and an outlet portion and a flipper, one end of which is pivotally mounted towards the inlet portion of the manifold, and an intermediate part of which is pivotally mounted within the manifold, the pivots lying substantially centrally with respect to the manifold, the flipper being operable in a scoop-swallow-wallop cycle to scoop and compress fluid into an inlet manifold via an inlet valve, the flipper being pivoted in the opposite direction to allow the compressed fluid from the inlet manifold though the outlet to produce a jet of fluid.

2. A jet engine according to Claim 1 , in which an ignition means is provided to ignite the compressed fluid in the inlet manifold, causing this to thermodynamically expand to jet the fluid from the outlet.

3. A jet engine according to Claim 2, including a fuel injection means for injecting fuel into the inlet manifold for combustion of the compressed fluid.

4. A jet engine according to Claim 2 or Claim 3, in which the expansion of the compressed fluid within the inlet manifold causes the pivoting of the flipper in the opposite direction.

5. A jet engine according to any one of the preceding claims, in which the inlet manifold is defined by an inner manifold side wall and an inner throat baffle, and the inlet valve, and is closed by the tail end of the flipper.

6. A jet engine according to Claim 5, further comprising an outlet valve.

7. A jet engine according to any one of the preceding claims, in which the inlet valve is biased towards a closed position.

8. A jet engine according to Claim 7, in which the bias of the inlet valve is adjustable.

9. A jet engine according to any one of the preceding claims, in which the inlet and/or the outlet valve is a flap valve.

10. A jet engine according to Claim 5 or any claim dependent thereon, in which the tail of the flipper includes a seal for sealing against the inner throat baffle.

11. A jet engine according to any one of the preceding claims, further comprising an outer manifold around the inner manifold, the outer manifold being defined by outer manifold side walls.

12. A jet engine according to Claim 11 , in which the tail of the flipper is arranged to be able to close the outer manifold.

13. A jet engine according to any one of the preceding claims, in which the size of the inner and/or the outer manifold is variable by movement of the inner and/or outer manifold walls.

14. A jet engine according to Claim 13, in which the inner and/or the outer manifold side walls are mounted on a scissors mechanism for movement with respect to the centre of the manifold.

15. A jet engine according to Claim 1 , further comprising a means for moving the flipper between opposite positions.

16. A jet engine according to Claim 15, in which a motor is connected to one of the pivots of the flipper to move the flipper between its opposite positions.

17. A jet engine according to Claim 15 or Claim 16, in which the fluid is a liquid, such as water.

18. A jet engine according to any one of the preceding claims, in which at least one of the pivots is a floating head pivot.

19. A jet engine according to Claim 18, in which the pivot mounting the end of the flipper towards the inlet of manifold is a floating head pivot.

20. A jet engine according to any one of the preceding claims, in which the flipper is formed of a resilient material, such as spring steel, or a nicromat alloy.

21. A jet engine according to any one of the preceding claims, in which the flipper includes an anti-oxide coating.

22. A jet engine according to any one of the preceding claims, in which the flipper is a cast flipper.

23. A jet engine according to any one of the preceding claims, in which the flipper includes cooling means to cool the flipper in use.

24. A jet engine according to Claim 23, in which the cooling means comprises channels for cooling fluid.

25. A jet engine according to Claim 24, in which the channels are formed within the flipper.

26. A jet engine according to Claim 24, in which the channels are formed on the surface of the flipper.

27. A jet engine according to any one of Claims 24 to 26, in which the cooling fluid is liquid sodium or water.

28. A turbojet compressor for providing compressed gas to an internal combustion engine, comprising: an inner manifold include an inlet portion and an outlet portion;a flipper, one end of which is pivotally mounted towards the inlet portion of the manifold, and an intermediate part of which is pivotally mounted within the manifold, the pivots lying substantially centrally with respect to the manifold; and, an internal combustion engine including a piston cylinder, the flipper being operable in a scoop-swallow-wallop cycle to scoop and compress fluid into the piston cylinder via an inlet valve, the fluid being combusted within the piston cylinder to drive a crank shaft of the engine.

29. A turbojet compressor according to Claim 28, in which the internal combustion engine is a multi-cylinder engine, for example a twin-cylinder engine.

30. A turbojet compressor according to Claim 28 or Claim 29, in which the crank shaft of the internal combustion engine is coupled to at least one of the pivots to move the flipper between opposed positions.

31. A turbojet compressor according to any one of Claims 28 to 30, in which the fluid is supplied to the piston cylinder via an inlet manifold, the inlet manifold being in the form of a funnel to compress the fluid as this is supplied to the piston cylinder.

32. A turbojet compressor according to any one of Claims 28 to 31 , in which the fluid is supplied to the piston cylinder via an inlet manifold that is angled with respect to the centre line of the compressor.

33. A turbojet compressor according to any one of Claims 28 to 32, in which at least one of the pivots is a floating head pivot.

34. A turbojet compressor according to Claim 33, in which the pivot mounting the end of the flipper towards the inlet of manifold is a floating head pivot.

35. A turbojet compressor according to any one of Claims 28 to 34, in which the flipper is formed of a resilient material, such as spring steel, or a nicromat alloy.

36. A turbojet compressor according to any one of Claims 28 to 35, in which the flipper includes an anti-oxide coating.

37. A turbojet compressor according to any one of Claims 28 to 36, in which the flipper is a cast flipper.

38. A turbojet compressor according to any one of Claims 28 to 37, in which the flipper includes cooling means to cool the flipper in use.

39. A turbojet compressor according to Claim 38, in which the cooling means comprises channels for cooling fluid.

40. A turbojet compressor according to Claim 38, in which the channels are formed within the flipper.

41. A turbojet compressor according to Claim 38, in which the channels are formed on the surface of the flipper.

42. A turbojet compressor according to any one of Claims 38 to 41 , in which the cooling fluid is liquid sodium or water.

43. An engine comprising a manifold, a flipper pivotally mounted for movement between a first position and a second position within the manifold to jet fluid out of the manifold, and a means for moving the flipper between the first and the second position, in which the side walls of the manifold include at least one one-way valve for allowing fluid to enter the manifold through the at least one valve, whilst preventing the flow of fluid from the manifold through the manifold side wall.

44. An engine according to Claim 43, in which a plurality of valves are provided on each side wall of the manifold.

45. An engine according to Claim 43 or Claim 44, in which the or each valve are flap valves.

46. An engine according to any one of Claims 43 to 45, arranged to propel a boat.

47. An engine according to any one of Claims 43 to 45, arranged to operate in a blood vessel to pump blood along the vessel.

48. A pump comprising a channel along which fluid is to be pumped, and a flipper mounted within the channel, the flipper including a fixed end and a free tail extending downstream within the channel, and a means to move the tail of the flipper between a first position substantially adjacent one side of the channel and a second position substantially adjacent the other side of the channel to pump fluid along the channel.

49. A pump according to Claim 48, in which the channel is formed in a substrate, for example by burning, micromachining, etching or lasering.

50. A pump according to Claim 49, in which the flipper is formed from a sandwich of three wafers bonded above the substrate, for example by burning, micromachining, etching or lasering.

51. A pump according to Claim 49 or Claim 50, in which substrate is a semi-conductor wafer.

52. A pump according to any one of Claims 48 to 51, in which the flipper includes at least two layers of different material or differently doped material, such that the application of a current across the flipper causes the flipper to move between the first and second positions.

53. A pump according to Claim 52, in which the flipper is formed with a n- type core and p-type layers on either side of the core.

54. A pump according to Claim 52, in which the flipper is formed with a p- type core and n-type layers on either side of the core.

55. A pump according to any one of Claims 48 to 54, further comprising an electrode to act as an anode or cathode charge collector at the tail end of the flipper.

56. A pump according to any one of Claims 48 to 55, further comprising a generally vertical or horizontal modulated magnetic field around the tail end of the flipper.

57. A pump according to Claim 56, including at least one electromagnet arranged near the tail end of the flipper to generate the magnetic field.

58. A pump according to Claim 57, in which the electromagnet comprises one or more coils provided in or adjacent the sides of the channel.

59. A pump according to any one of Claims 48 to 58, in which the flipper is mounted on a chip in a vertical planar bonded assembly of three wafers.

60. A gated charge pump including a pump according to any one of Claims 48 to 59.

61. A jet engine comprising a centrally-pivoted flipper located within an air or water inlet and outlet manifold whereby the front end of the flipper is also pivoted with a floating head, both pivots lie in the same axial line within the engine, the flipper operates a scoop swallow wallop cycle in which air or water is initially scooped towards the middle section of the engine by the front end of the flipper, the air or water passes through a valve operated by the pressure of the air or water, the flipper then pivoting in the opposite direction forces the air or water rearwards towards the outlet by the action of the rear end of the flipper moving towards the air of water which is trapped by the closure of the valve.

62. A jet engine according to Claim 1 or Claim 60, in which steam is injected into the inner manifold to create power.

63. A jet engine according to any one of Claims 1 to 27, or a turbocompressor according to any one of Claims 28 to 42, or an engine according to any one of Claims 43 to 47, in which a the flipper includes a variable stiffener to vary the resonant frequency.