BACKGROUND In gas turbine engines air is taken in at the front end of the engine and compressed by a series of rings of turbine blades which rotate between rings of static blades so that air is forced into a smaller space. The compressed air is passed to a static combustion chamber where fuel is added. Thrust is generated by the exhaust gases, which also create rotary motion to drive the compressor by means of a further series of turbine blades.

Conventional gas turbine engines are very expensive to manufacture and are not suitable for powering small vehicles such as boats. A substantial part of the cost is attributable to the large number of turbine blades, which must be manufactured to withstand very high stresses. Engines with combustion chambers fed by rotary centrifugal compressors are known, but they are somewhat inefficient with a relatively low power to weight ratio. The compressor must be relatively large and must also run at a very high speed.

Furthermore, it is known that the efficiency of internal combustion engines can be improved by injecting steam into the combustion chamber.

The present invention seeks to provide a new and inventive form of engine which can be used as an efficient thrust generator capable of operating at relatively low running speeds and with a high power to weight ratio.

SUMMARY OF THE INVENTION The present invention proposes an engine having a rotary body which includes a compression section for compressing gases and a combustion chamber for receiving and burning the compressed gases and provided with at least one vectored exhaust port for producing rotary thrust, in which the compression section includes at least one helical passage having a mouth for capturing air during rotation of said body and which decreases in cross- section area towards the combustion chamber.

Compression is thus produced using a rotary ram jet principe.

The efficiency of the engine can be increased still further if combustion chamber is provided with water cooling passages which are arranged to vent water vapour into the gas flow, either directly into the combustion chamber or downstream of the combustion chamber. The water flow therefore not on cools the rotary combustion chamber but also utilises the recovered heat energy to enhance the power of the engine.

BRIEF DESCRIPTION OF THE DRAWINGS The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is a longitudinal section through an engine in accordance with the invention for use as a thrust generator; Figure 2 is an end elevation of the thrust generator, looking from the left in Fig. 1; Figure 3 shows one of the fins of the thrust generator in a planar configuration; Figure 4 shows the same fin in its normal configuration when mounted within the thrust generator; Figure 5 is an end elevation of the thrust generator as viewed from the right in Fig. 1; Figure 6 is a detail of the thrust generator on section line VI-VI of Fig. 5; and Figure 7 is a longitudinal section through a modified form of the engine.

DETAILED DESCRIPTION OF THE DRAWINGS The thrust generators described below can be used as an engine for propelling small boats for example. Propulsion can be achieved through direct thrust so that the vessel does not sufferfrom speed limitations caused by cavitation problems often associated with propellers.

Referring to Fig. 1, the thrust generator comprises a rotor 1, having a front or inlet end 2 and an opposite rear or outlet end 3. A generally cylindrical casing 4 is fixed to the rotor 1. The rotor is mounted in thrust bearings 5 and 6 at opposite ends and is conveniently formed in two parts, namely a ram jet part 7 and a combustion chamber part 8.

The ram jet part 7 contains an axial drilling 10 and includes a short cylindrical section 11 leading into a conical section 12. The external surface of the conical section 12 is formed with six helical grooves which all commence at the narrow end of the conical section, spaced at 60° circumferential intervals, and travel at the same pitch to the rear end of the conical section where they again terminate at 60° intervals. Each of the six grooves contains a helical fin 14, which can clearly be seen in the end view of Fig. 2. The width of the fins progressively decreases towards the wider end of the conical section 11, and for the purpose of clarification only, one of the fins is shown in a planar configuration in Fig. 3. The configuration which a single fin adopts when mounted on the conical section 12 is shown in Fig. 4. The outer flanks of the fins 14 are received in corresponding helical grooves formed in the inner surface of the casing 4. It will thus be appreciated that six helical passages 15 are formed between the fins 14, which progressively reduce in cross-sectional area from a mouth region at the wider end of the fins towards the narrower end of the fins.

Continuing with the discussion of Fig. 1, the combustion chamber part 8 comprises a circular head 16 which abuts the wider end of the conical section 12, followed by a longer cylindrical section 17. The part 8 is then stepped inwardly to form a shaft section 18 which leads to the thrust bearing 6. The wall of the casing 4 is stepped outwardly at 19 adjacent to the head 16 to form an annular combustion chamber 20 between the casing 4 and the cylindrical section 17. Fuel is conducted to the chamber through the drilling 10 and a series of radial passages 22 formed between the opposed faces of the two parts 7 and 8 of the rotor. The outer ends of the passages 22 may be angled rearwardly as shown to direct fuel towards the combustion chamber 20. The rear end of the combustion chamber 20 is closed by an annular thrust plate 24, shown in Fig. 5, which may be integral with or rigidly connected to the casing 4. Bolts 25 pass axially though the thrust plate 24, cylindrical section 17 and head 16, and are threaded into the conical section 12 to secure the parts of the rotor and the casing together. The thrust plate 24 contains a circumferential ring of outlet ports 26. Fig. 6 shows one of the ports sectioned axially of the rotor, from which it will be seen that the ports extend at an angle to an axial plane of the rotor.

Part 8 of the rotor contains an axial drilling 28 which can supply liquid to a number of cooling passages 29 within the cylindrical section 17. The cooling passages discharge into the combustion chamber through injector ports 29'. To start the rotor spinning compressed air or other fluid can be fed through the drilling 28 into the combustion chamber 20. The air exiting from the angled ports 26 produces a vectored thrust which causes the rotor 1 to start spinning. As the rotor turns, air is captured at the inlet end of the passages 15 in the manner of a ram jet and flows towards the combustion chamber 20, being compressed in the process due to the reducing cross- section area of the passages 15. Fuel is mixed with the compressed air in the chamber 20, and when a suitable level of compression has been reached the mixture is ignited by a spark gap or other known means (not shown). The combustion gases will then pass through the outlet ports 26 creating a thrust with a vectored axial and rotary component, thereby maintaining rotation of the rotor and compression of the air for combustion.

Clearly, once combustion has taken place no further supply of fluid via the drillings 28 and passages 29 is required, and the supply can then be replace by water which is fed to the drilling 28 by a centrifugal pump or similar means. As the engine operates the combustion chamber is cooled by the water flowing through the passages 29 causing the water to become superheated. Upon entering the combustion chamber, which is now operating at a high temperature, the already heated water instantaneously evaporates and rapidly expands to increase the thrust of the gases exiting through the angled ports 26.

It will be appreciated that the number of helical fins can vary, and the means by which fuel is supplie to the combustion chamber is also relatively unimportant. Furthermore, any convenient means can be utilise to start the rotor spinning and initiate compression prior to combustion.

The position, area and the angle of the outlet ports may be varied to alter the relative sizes of the radial and axial thrust components. By placing the angled outlet ports in the cylindrical wall of the chamber 20 the engine may be used to produce pure rotary drive to power vehicles, machinery, electricity generators etc..

Since the fins are supported on both flanks they can be manufactured at considerably less cost than turbine blades.

In the modified form of the engine shown in Fig. 7 which is intended for marine use the compressor section is essentially as described above but the casing is extended to accommodate an exhaust chamber 31 surrounding the shaft section 18, which now has generally conical section 32 so that the area of the exhaust chamber increases away from the outlet ports 26.

Again, the rotor 1 contains an axial passage 28 which supplies radial and axial cooling passages 29 for cooling the combustion chamber 20. However the passages lead to radial drillings 33 in the thrust plate 24 which in turn supply axial drillings 34 in the casing 4. These lead via non-return pressure-relief valves 35 to rearwardly-directed injector ports 36 so that cooling water which has become superheated in the cooling passages 29 immediately evaporates in the exhaust chamber and rapidly expands in the heat of the exhaust gases causing greatly increased thrust. There is no risk of salts being deposited in the combustion chamber.

The forms of engine described above have very high power to weight and power to size ratios and avoids the need for expensive turbine blades. The compressor stage is compact and the engine can run at a relatively low speed. Propulsive power can be obtained from the torque which is generated by the rotor and/or by direct thrust.

It will be appreciated that the features disclosed herein may be present in any feasible combination. Whilst the above description lays emphasis on those areas which, in combination, are believed to be new, protection is claimed for any inventive combination of the features disclosed herein.

CLAIMS 1. An engine having a rotary body (1,4) which includes a compression section for compressing gases and a combustion chamber (2) for receiving and burning the compressed gases and provided with at least one vectored exhaust port (26) for producing rotary thrust, in which the compression section includes at least one helical passage (15) having an inlet for capturing air during rotation of said body and which decreases in cross-sectional area towards the combustion chamber.

2. An engine according to Claim 1, in which the compression section comprises a plurality of such helical passages (15) disposed at circumferential intervals around the rotation axis of the body.

3. An engine according to Claim 2, which said passages are formed by a plurality of fins (14) disposed between inner and outer walls (12,4) which mutually converge towards the combustion chamber.

4. An engine according to Claim 1, in which the combustion chamber is provided with water cooling passages (29) which are arranged to vent water vapour into the gas flow.

5. An engine according to Claim 4, in which the water vapour is vented into the exhaust gases after leaving the exhaust ports (26). 6. An engine according to Claim 5, in which the water vapour is vented into an exhaust chamber (31) together with the exhaust gases.

7. An engine according to Claim 4, in which the water vapour is vented into the combustion chamber (2).

AMENDED CLAIMS [received by the International Bureau on 30 March 2001 (30.03.01); original claims 1-7 replaced by new claims 1-5 (1 page)] 1. An engine having a rotary body (1,4) which provides a compression section (7) for compressing gases and a combustion chamber (20) for receiving and burning the compressed gases and provided with at least one vectored exhaust port (26) for producing rotary thrust, in which the compression section includes at least one helical passage (15) having an inlet for capturing air during rotation of said body, characterised in that said passages (15) are formed by a plurality of fins (14) disposed between inner and outer walls (12,4) which mutually converge such that each passage decreases in cross-sectional area in the direction of air flow towards the combustion chamber.

2. An engine according to Claim 1, in which the combustion chamber is provided with water cooling passages (29) which are arranged to vent water vapour into the gas flow.

3. An engine according to Claim 2, in which the water vapour is vented into the exhaust gases after leaving the exhaust ports (26).

4. An engine according to Claim 3, in which the water vapour is vented into an exhaust chamber (31) together with the exhaust gases.

5. An engine according to Claim 2, in which the water vapour is vented into the combustion chamber (2).