GB2584121A - Inward flow radial turbine - Google Patents

Abstract

An inward flow radial turbine 1, rotating as per arrow 2 within a housing 5, associated with an annular vessel formed by co-axial cylinders 6 and 7, and an annular piston 11 operating on a two stroke cycle. On the outward stroke of the piston, energised fluid is admitted via a valve 15 and nozzle 16 to the vessel to form a swirl. On the inward stroke of the piston, valve 15 is closed, and the fluid swirl is displaced through an annular array of vanes 9 to the inducer 3 of the rotating turbine rotor and forced inwards between the turbine blades to exit at the exducer 4, whereby fluid kinetic energy is transferred to the turbine.

Description

Inward Flow Radial Turbine

Field of the Invention:

The invention relates to Inward Flow Radial (1 F.R.) Turbines, particularly compact turbines using gas as the working fluid, and proposes means to improve the efficiency of such turbines and enhance their suitability for decentralised electricity generation applications.

Background of the Invention:

The technology of turbines, which utilise rotating blades to convert energy from fluids into useful work, is well developed. This patent application is primarily concerned with inward flow radial (I.F.R.) turbines, also known as radial inflow turbines or centripetal turbines. In an I.F.R. turbine, the working fluid passes from the periphery of the rotating turbine rotor (the inducer) inward between the converging turbine blades to exit the turbine rotor near the rotational centreline (the exducer), giving up energy to the turbine rotor as it does so. The working fluid may be compressible, as in gases, including steam, or incompressible, as in liquids. This application addresses the particular case of an I.F.R. turbine with gas as the working fluid. However, the principle of operation of the engine described also applies to other fluids.

For high power applications the axial flow turbine, employing steam or other gases as the working fluid, is in common usage, utilising multiple discs of rotating blades in the rotor, combined with circular arrays of static blades which form the stator. Examples are found in power stations to generate electricity, the steam or hot gas being produced separately from the turbine by heat transfer from the combustion of fossil fuels or by nuclear reaction. Such axial flow turbines are efficient energy converters, but are invariably large complex machines with multi-stage rotors and stators, and are very expensive to manufacture and service. They operate at rotational speeds of the order of 3000 to 15000 r.p.m., these speeds being relatively moderate because the high energy gases do not impinge on the airfoil shaped turbine blades directly but at a shallow angle of attack.

Large I.F.R. turbines employing water as the working fluid find common application in hydro-electric power plants, an example being the Francis Turbine. However, I.F.R turbines with gases as the working fluid are less suited to centralised power generation, due to their restricted power output. Recently, interest has grown in the development of compact power units under the generic name 'microturbines', which are increasingly finding application in decentralised electricity power supplies, or in small onboard units to charge the batteries of electric vehicles. Microturbines are small turbines with power outputs in the range 25 kW to 500 kW. They are a development of the turbocharger fitted to many automotive internal combustion engines, which comprise an I.F.R. turbine and centrifugal compressor on a single shaft, the turbine being driven by exhaust gases from the vehicle engine and the compressor boosting the air supply-to the engine. The microturbine similarly comprises a small I.F.R. turbine and centrifugal compressor on a common single shaft, powering an electrical generator, generally on the same shaft. The compressor in this case pumps air into a combustion chamber, integral to the engine, which is fed with fuel from an injector, and the resulting high energy combustion gases drive the turbine. The efficiency of these engines in terms of fuel energy to electrical output is of the order of 15% in the best examples, compared to around 40% for fossil fuelled power stations employing axial flow turbines. The efficiency of microturbines can be raised to 20 -30% by means of a 'recuperator', which is basically a heat exchanger using exhaust heat from the turbine to raise the temperature of the air being transferred from the compressor to the combustion chamber. Nevertheless, a significant amount of energy in microturbines is lost via the hot exhaust, gas temperatures of 250 -300 degrees Celsius being typical for microturbines with a recuperator and higher for those without. This is less of an issue with Combined Heat and Power (C.H.P.) generators, where the exhaust heat from the engine can be used to heat buildings, raising the overall efficiency of fuel energy to electrical power plus heat energy to 80% or so.

Despite their comparatively inefficient performance, I.F.R. gas turbines do have certain advantages compared to axial flow turbines, including the benefit accruing from the greater amount of energy that can potentially be extracted from one single stage. Further, their superior ruggedness and reliability are important considerations, due to their being relatively simple and inexpensive to manufacture and service, with the single stage turbine rotor commonly being machined from a single casting. These properties render them a more cost-effective proposition for compact decentralised electric power supplies than complex multistage axial flow types.

The limitations in regard to the maximum power output attainable from I.F.R. gas turbines and their lower efficiency compared to multi-stage axial flow types are attributable to a number of factors. The single-stage design inevitably places an upper limit on the power output, compared to axial flow turbines which can accommodate multiple stages. Further, I.F.R. gas turbines operate at very high rotational speeds, due to the requirement to synchronise as closely as possible the speed of the blades at the periphery of the turbine rotor (the inducer) with the velocity of the gas flow impinging substantially directly on them. Due to this high rotational speed, the rotors of such turbines currently in production tend to he of relatively small diameter to minimise centrifugal stresses on the rotor blades. The high centrifugal forces also act against the gas flow moving radially inwards, placing limits on the effective diameter of the rotor from inducer to exducer. The fact that the rotor blades converge as they near the axis of the rotor create a further impediment to the radial gas flow near the exducer.

The object of the present invention is to mitigate some of the disadvantages of I.F.R. gas turbines by the provision of positive displacement means to force the working gas inwards within the rotor of the turbine, thus overcoming the centrifugal force and the restriction created by the reducing inter-blade clearance near the exducer. By these means, it is possible to eliminate the centrifugal compressor from compact gas turbine designs such as microturbines, and employ gas heated in a chamber ancillary to, but physically separated from, the turbine as a working gas. This opens the possibility of using a greater diversity of heating methods for the working gas rather than being restricted to the burning of hydrocarbon fuels. Further, by employing a turbine rotor of greater diameter, with blades longer than current designs, greater efficiency can be achieved in the conversion of the kinetic energy of gas flow into mechanical energy at the turbine shaft. Operating at a lower gas temperature than that of current designs is also possible, which will enhance the strength and durability of the turbine rotor and its ability to withstand high centrifugal forces. With such improvements it is believed that higher efficiencies are attainable in compact inward flow radial gas turbines, comparable to the efficiency of larger multi-stage axial flow turbines.

Statement of Invention:

According to the invention there is provided an inward flow radial (I.F.R.) turbine, the rotor of which comprises a plurality of blades attached to a rotor disc, converging inwardly from the disc periphery towards the rotational centre. The disc is fixed co-axially to a shaft, and the rotor is partially enclosed and rotatably mounted within a rotor housing. The blades are preferably straight, disposed along radial lines, as curved blades are more susceptible to centrifugal stresses. The preferred embodiment employs a gas or combination of gases as the working fluid. The turbine is associated with a vessel having a circular internal wall along a longitudinal axis which, in the preferred embodiment, is of annular construction, formed by the annular space between two co-axial cylinders. The head of the vessel is fixedly connected to the rotor housing such that the axes of the vessel and turbine rotor are co-axial.

An annular duct is located between the head of the vessel and the rotor housing at or near their rims, providing a fluid passage. Within the duct are guide vanes connected radially between two concentric rings, thus forming an annular array, the inner and outer rings attached to the inner and outer circumferential surfaces respectively of the annular duct. The vanes and rings are of sufficient mechanical strength to maintain the structural integrity of the annular vessel and rotor housing by bridging the radial gap in the annular duct. The vanes partially overlap with a channel between adjacent vanes, and are disposed to permit fluid flow in the direction of rotation of the turbine rotor. In the preferred embodiment, the annular duct occupies the entire radial space at the head of the annular vessel, with the inner and outer rings of the vane array being attached to the inner and outer walls respectively inside the vessel.

Within the annular vessel is positive displacement means comprising an annular piston reciprocating slideably in the annular space along the longitudinal axis of the vessel, the piston conventionally fitted with seals on its inner and outer circumferential surfaces to minimise gas leakage between the piston and the vessel internal walls. The annular piston operates on a two-stroke cycle, and on the outward stroke thereof, away from the head of the vessel, a partial vacuum is created within the annular vessel. Due to the disposition of the vanes in the annular duct, the gas flow into the rotor housing is substantially unidirectional such that any tendency to flow in the reverse direction from rotor housing to vessel and disrupt the partial vacuum during the outward stroke of the piston is minimised, as long as the rotor is rotating at or near its optimum speed. At this point in the cycle, energised gas, which is the product of combustion or has been heated indirectly, is delivered via a valve or valves which control the timing and quantity of the delivery, to a nozzle or nozzles positioned around the exterior periphery of the vessel. The nozzle(s) are designed in accordance with known principles to efficiently convert the pressure energy of the gas into the kinetic energy of a directed gas jet, which is injected into the vessel in a direction substantially tangential to the outer of the two internal walls of the vessel. A swirl of gas possessing high rotational kinetic energy is thus formed, which is constrained by the outer internal wall. During the subsequent inward stroke of the piston the gas flow from the nozzle or nozzles into the vessel is shut off by the valve or valves, and the swirl of gas is displaced to the head of the vessel. From there it passes through the array of vanes in the annular duct to the turbine housing.

The swirl of gas passing through the annular duct is composed of two velocity vectors: a high rotational velocity which corresponds with that of the blades at the outer circumference of the rotating turbine rotor, and a lower translational velocity in the direction of the rotor axis due to the action of the piston. The angle of the vanes in the array is set to approximately align with the resultant of these two velocity vectors, such that the swirl of gas passes through the channels between the vanes efficiently.

The gas swirl is thus forced by the inward stroke of the annular piston radially inwards from the inducer of the turbine rotor between the blades thereof towards the axis of the turbine rotor, to exit at the exducer, whereby the energy of the gas is transferred to the turbine rotor shaft. The shaft may he connected to an electricity generator, and the electricity generated may be stored in batteries.

The passage of the swirl of gas from the vessel to the turbine rotor is assisted by the contour of the turbine rotor housing and the contour of the rotor disc at their peripheries, initially diverting the swirl from an axial direction relative to the rotor disc to an inward radial direction. In common with other examples of I.F.R. turbines and prior art, the gas flow at the exducer reverts to an axial direction by the contour of the rotor disc and rotor housing, and the blades at this point are curved back against the direction of rotation to ensure that maximum kinetic energy is transferred to the rotor.

The energy transferred to the shaft of the turbine rotor has a magnitude theoretically equalling the sum of the kinetic energy given up by the gas within the rotating turbine rotor plus the energy expended by the piston in moving the gas radially inward against centrifugal force. This latter action is analogous to a revolving ice skater pulling his arms inwards, the work done in countering the centrifugal force contributing to an increase in the skater's rotational kinetic energy.

In regard to the operation of the piston, the technology of reciprocating pistons within cylinders is well developed and is not described here. The source of the power to operate the piston is the engine as a whole, preferably via a mechanism powered by electricity generated by the engine and stored in a battery, such as an electric linear motor. This energy is recouped in being transferred to the shaft of the turbine during the inward stroke of the piston. In essence, the engine powers the piston, indirectly in the case of electric actuation, and the action of the piston contributes to the power output of the engine. Thus, the net contribution of the piston and its power supply to the output of the engine is theoretically zero, and will actually be a minus figure due to friction and other losses. However, it is not anticipated that such losses will be significant with careful design of these ancillary parts. It follows that the net output of the engine as a whole is solely the kinetic energy given up by the working gas within the turbine rotor, again with due allowance made for frictional and other losses.

The two-stroke cycle described is repeated as required for continuous operation. The turbine described in this application operates of necessity in a fairly narrow band of high rotational velocity, linked to the velocity of gas injected at the nozzle or nozzles. Preferably there is electronic processor means of synchronizing the rotational speed of the turbine rotor with the velocity of fluid injected to the vessel, such that the swirl of gas impinges on the blades at the inducer of the rotating rotor with minimal shock. Such means would comprise sensors to measure these two quantities, and be electronically linked to the valve or valves to adjust the timing and mass of fluid injected to the vessel via the nozzle or nozzles. This would compensate for any deviation in rotational speed of the turbine rotor caused by variations in load, and thereby stabilise the rotational speed and power output of the turbine. It may also be advantageous to equip the turbine rotor shaft with a flywheel to damp any variations in rotor speed caused by the operation of the two-stroke cycle described, although the high angular momentum of the rotating turbine and any electrical generator fitted to the common shaft may render this unnecessary.

It should be noted that the gas flow from the head of the vessel to the turbine housing is only unidirectional so long as the turbine rotor is rotating at its design operational speed. In the case of a stationary rotor, some of the working gas would flow from the turbine housing through the channels between the vanes to the head of the vessel during the outward stroke of the piston, disrupting the partial vacuum in the vessel and adversely affecting the injection of gas from the nozzle or nozzles and the formation of a gas swirl. To obviate this, the turbine may be brought up to operating speed by a separate starter motor, or by operating the electricity generator connected to the turbine shaft in reverse as a motor. This is a common procedure in many gas turbine power units.

The exhausted gas from the turbine may be discharged to the atmosphere in the case of a combination of gases which is the product of combustion. Alternatively, a working gas may be heated indirectly and re-circulated in a closed-cycle. Steam, from the heating and boiling of liquid water, is one such example, and a separate condenser would be required in this instance to convert the exhausted steam back to water.

Alternatively, the turbine could find application in a process using liquefied atmospheric gases as an energy storage medium. A common gas such as nitrogen is employed in some units currently in production, such a gas being readily available commercially in liquid form and stored in pressurised containers. The process entails heating liquefied gas to ambient or greater temperature by air-source or ground-source means, or by waste exhaust heat from another engine, with the resulting gas utilised to power an engine, thereafter being discharged back to the atmosphere from whence it originated. Such a process is described in a number of patents and patent applications. It is suggested that the inward flow radial turbine described in this patent application would be a more efficient means of such energy conversion.

An inert gas such as argon, which is also a commonly available component of the atmosphere, would provide certain advantages as a working gas. Being monatomic, heat transferred to the gas is converted entirely to translational kinetic energy of its atoms, contributing to greater efficiency in the conversion of heat to mechanical energy in the turbine. The argon gas could be heated and re-circulated in a closed cycle, or employed in commercially produced liquid form and discharged back into the atmosphere as in the previously described cryogenic nitrogen process.

Taking the example of argon gas as a working fluid, heated to 200°C (473K) within a chamber as part of a closed cycle, the velocity of the gas jet from a typical convergent/divergent (CD) nozzle into a vacuum in an ideal adiabatic isentropic expansion is of the order of 700 m/sec. A swirl of gas with this circumferential velocity impinging on the outer blades of a rotor disc of radius 10cm would equate to a rotational speed at the turbine rotor shaft of approximately 67,000 r.p.m. As an alternative to roller bearings, high speed bearings, such as air bearings or foil hearings, could advantageously he employed to support the shaft to cope with such high rotational speeds.

Irrespective of the source or composition of the energised gas used to power the gas turbine, it is suggested that the greater efficiency possible with the engine which is the subject of this application renders it a more viable proposition in applications such as decentralised electricity generation and electric vehicle battery charging.

Alternative Embodiments: Other arrangements are theoretically possible in regard to the design of the vessel and positive displacement means. For example, the latter could take the form of a flexible diaphragm within the circular space of a vessel. Another possible configuration for the vessel is a circular bellows design made of resilient material. However, it is proposed that the most efficient form of vessel is that of a cylinder, with the positive displacement means comprising a piston, as the technology of reciprocating pistons within cylinders is well developed and described by prior art. The preferred embodiment is an annular piston reciprocating within an annular vessel, as this arrangement offers more effective containment of the fluid swirl. The annular piston also produces a greater axial pressure on the fluid swirl than a full width piston in a single cylinder, due to the smaller surface area of the annular piston head. A further advantage of the annular vessel is that of creating a void within the inner of the two cylinders to accommodate a housing for the bearings of the turbine rotor.

In the preferred embodiment, the vessel and rotor housing internal wall diameters are essentially equal, with the axes of the vessel and rotor being co-axial. It is feasible to have a vessel of smaller diameter, with its axis displaced outwards from the axis of the rotor and its housing. The outer part of this vessel at its head would then abut the outer part of the rotor housing, with a duct between these two outer parts. This clearly limits the size of the duct, reducing its effectiveness in regard to fluid transfer from vessel to rotor housing. The co-axial positioning of the vessel and rotor axes permits a more efficient annular duct arrangement in regard to fluid transfer.

Other unidirectional elements are possible within the annular duct between vessel and rotor housing. One option is an annular plate free to slide axially within the duct. to abut on an annular stationary plate, the sliding plate closing automatically under the influence of the partial vacuum in the vessel and opening under fluid pressure from the vessel. Similarly, an annular valve of resilient material within the duct could act as closure means. There are disadvantages of these approaches, one being the greater resistance to the transit of the fluid swirl, in both the rotational and axial directions. Further, such annular means are not readily conducive to the fitting of radial supports within the duct to maintain the structural integrity of the vessel and rotor housing. The guide vane arrangement within the duct addresses these problems and is incorporated in the preferred embodiment.

In the preferred embodiment the outer diameter of the annular space of the vessel corresponds to that of the turbine rotor housing, although the possibility exists for these dimensions to differ, with the annular duct connection between vessel and rotor housing modified accordingly. However, the preferred arrangement where the vessel and rotor housing internal wall diameters are essentially equal and flush with each other provides the shortest fluid path and a greater efficiency of fluid transfer.

The initial claim of this application is deliberately generalised in seeking to include these alternative means regarding the vessel, positive displacement means, the duct and unidirectional means therein.

Introduction to the drawings:

One particular embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings. Note that any reference to upper and lower, upward and downward, head and base, relates to the orientation of the drawings and does not imply that the engine itself should necessarily he oriented thus to operate. Details regarding joints and fastenings have been omitted for clarity, and most components are shown in simplified form.

Figure 1 is a cutaway upper view of the engine.

Figure 2 is a cutaway lower view of the engine.

Figure 3 is a cutaway upper view of the engine during the outward (downward) stroke of the annular piston.

Figure 4 is a cutaway upper view of the engine during the inward (upward) stroke of the annular piston.

Figure 5 is an exploded view of the engine.

Detailed Description of the Drawings:

The invention will now be described in more detail, limited to the specific embodiment shown in the drawings, on the understanding that other arrangements are possible within the scope of the operating principle of the invention.

Figure 1 shows an inward flow radial gas turbine comprising a turbine rotor 1, which rotates as shown by arrow 2, the rotor disc having radial blades converging from the rotor periphery, the inducer 3, towards the vicinity of the rotor centre, the exducer 4. The turbine rotor is partially enclosed in a housing 5, connected to an annular vessel formed by two coaxial cylinders, an outer cylinder 6 and inner cylinder 7, both co-axial with the turbine rotor. For simplicity, the turbine housing 5 and outer cylinder 6 are shown connected as a single entity in the drawings (cutaway in figures 1 to 4). The outer and inner cylinders are fixed in position relative to each other by means of a circular ventilated end plate 8 at the base of the vessel and a co-axial annular array of vanes 9 positioned between two concentric rings 10 at the head of the vessel (outer ring in cutaway in figures 1, 2, 3, 4), this foaming an annular duct between the vessel and the turbine housing. The vanes 9 partially overlap with a channel between adjacent vanes, and are disposed as shown at a shallow angle to correspond with the direction of rotation of the turbine rotor. The two concentric rings 10 are attached to the inner and outer cylinder walls at the head of the annular vessel. Only the outer ring is visible in Figure 1. An annular piston 11, fitted with inner and outer circumferential seals, is slideably moveable within the annular space between the two co-axial cylinders, further guided in this particular embodiment by means of four rods 12. The rods are slideably movable within bushes in the end plate 8, and terminate in a cross piece 13 connecting them to the main piston rod 14. The mechanism by which the main piston rod moves is not shown in the drawing, all such methods being well described by prior art. A nozzle 16, supplied with gas controlled by a valve 15, is affixed to the outer cylinder to inject energised gas into the vessel as a directed jet. The nozzle shown is a convergent/divergent (CD) representation, but other designs are possible within the scope of the invention. Only one nozzle is shown in the drawings, but a number of nozzles and associated valves could be positioned around the periphery of the vessel.

Figure 2 is a view of the base of the invention showing the inside of the inner cylinder 7 of the annular vessel, the space enclosed by this inner cylinder containing the housing 17 for the turbine bearings, which is supported by the circular partition 18. This partition forms the head of the inner cylinder and the base of the turbine rotor housing. Both inner and outer concentric rings 10 are visible in this view, the outer ring in cutaway. Also shown is the circular ventilated end plate 8 with bushes in which the four rods 12 slideably move, and the cross piece 13 connecting the rods to the main piston rod 14.

Figure 3 is a view of the invention showing the annular piston 11 on the outward (downward) stroke indicated by arrow 19. The valve 15 is open and gas is admitted to the vessel via the nozzle 16, forming a swirl of gas indicated by the arrows 20. With the turbine rotor 1 rotating at high speed, gas leakage from the turbine housing during the outward stroke of the annular piston is minimised due to the orientation and partial overlap of the static vanes in the annular array of vanes 9 at the head of the vessel.

Figure 4 is a view of the invention showing the annular piston 11 on the inward (upward) stroke, indicated by arrow 19. The valve 15 is now closed and no gas is being admitted via nozzle 16 to the vessel. The swirl of gas indicated by arrows 20 is displaced to the head of the vessel and thence through the annular array of vanes 9 into the turbine rotor housing 5 and inducer 3 of the turbine rotor 1. The profile of the rotor housing and the profile of the rotor disc at this point are so contoured as to assist the smooth transition of the swirl of gas from an axial direction to a radial direction inward between the blades of the rotor. The fluid swirl moves towards the centre of the rotor, giving up its rotational kinetic energy as it does so, and its direction reverts to an axial direction by the profile of the rotor disc and rotor housing to exit at the exducer 4. The blades of the rotor at the exducer are curved hack against the direction of rotation to maximise energy transfer from gas to rotor in accordance with prior art.

Figure 5 is an exploded view of the invention showing the bearings 21 attached to the shaft of the turbine rotor 1, which have been withdrawn from the bearing housing 17 on the reverse side of the circular partition 18. It also shows the co-axial annular array of vanes 9 between the concentric rings 10 detached from the inner cylinder 7 and outer cylinder 6. The turbine housing 5 and outer cylinder 6 are shown connected as a single entity in the drawings. The annular piston 11 has been withdrawn from the annular vessel and both inner and outer piston rings are shown. The ventilated end plate 8 has also been disconnected from the inner cylinder 7 and outer cylinder 6.

Claims (13)

1. Claims 1. An engine for converting the energy of a fluid to mechanical energy, comprising: an inward flow radial turbine, the rotor of which comprises a plurality of blades attached to a rotor disc, (he disc fixed co-axially to a shaft, the blades converging inwardly from the rotor periphery towards the rotor centre, said rotor partially enclosed and rotatahly mounted within a rotor housing; said turbine in a co-operative relationship with a vessel having a circular internal wall along a longitudinal axis, with the head of the vessel fixedly connected to the aforesaid rotor housing; and a duct is located between the head of the vessel and the rotor housing, said duct incorporating elements to enable the unidirectional flow of fluid from the vessel to the rotor housing; and the aforesaid turbine rotor is caused to rotate about its axis by a starting mechanism; and said vessel incorporates positive displacement means operating in the direction of the longitudinal axis of the vessel on a two-stroke cycle whereby, on the outward stroke thereof, away from the head of the vessel, a partial vacuum is created within the vessel, when fluid possessing kinetic energy is injected into the vessel from at least one nozzle positioned around the exterior periphery of the vessel, in a direction substantially tangential to the internal wall thereof, thus forming a swirl of fluid possessing rotational kinetic energy, which is constrained by said internal wall; and during the subsequent inward stroke of said positive displacement means, the swirl of fluid is displaced to the head of the vessel and thence through the aforesaid duct into the rotor housing to impinge on the rotor blades at the periphery of the rotating turbine rotor, and is forced by the action of the positive displacement means radially inwards between the rotor blades towards the rotor centre, thereabouts to exit the rotor and rotor housing, whereby the energy of the fluid is transferred to the rotating turbine rotor and shaft thereof; and the aforesaid two-stroke cycle is repeated as required for continuous operation, and, during each outward stroke of the said positive displacement means, fluid is injected to said vessel with sufficient mass and velocity to maintain turbine rotor rotation and the power output of said engine.
2. 2. An engine according to claim 1 in which the aforesaid vessel is of annular construction, formed by the annular space between two co-axial cylinders, and the head of the annular vessel is fixedly connected to said rotor housing such that the annular vessel and turbine rotor axes are substantially co-axial; and the aforesaid duct is of annular construction, located between the head of the annular vessel and the rotor housing at or near their peripheries, the axis of said annular duct being substantially co-axial with the vessel and turbine rotor axes, and incorporating elements as aforesaid to enable the unidirectional flow of fluid from the annular vessel to the rotor housing; and the aforesaid positive displacement means comprise an annular piston reciprocating slideably within said annular space in the direction of the longitudinal axis of the vessel and operating on the previously described two-stroke cycle, the annular piston fitted with seals on its inner and outer circumferential surfaces to minimise fluid leakage between the piston and the vessel internal walls.
3. 3. An engine according to claim 2 in which the aforesaid elements within the annular duct between the head of the aforesaid vessel and rotor housing comprise vanes connected radially between two concentric rings to form an annular array, the inner and outer rings attached within the annular duct, said vanes and rings being of sufficient mechanical strength to maintain the structural integrity of the vessel and rotor housing by bridging the radial gap in the annular duct; and the vanes partially overlap with a channel between adjacent vanes, disposed to permit fluid flow in the direction of rotation of the turbine rotor, and thereby minimise fluid leakage in the reverse direction from the rotor housing to the vessel during the outward stroke of said positive displacement means while the turbine rotor is rotating; and on the inward stroke of said positive displacement means, the aforesaid swirl of fluid, possessing a rotational velocity component and lesser axial velocity component, passes between said vanes, which are so oriented to approximately align with the resultant of the said two velocity components.
4. 4. An engine according to any preceding claim in which the at least one nozzle is constructed in accordance with known principles to convert the pressure energy of the working fluid substantially to translational kinetic energy, and is associated with a valve or valves to control the timing and quantity of fluid injected into the vessel during the outward stroke of the aforesaid positive displacement means, and to shut off the flow of fluid to the at least one nozzle during the subsequent inward stroke of the positive displacement means.
5. 5. An engine according to claim 4 in which there is electronic processor means of synchronizing the rotational speed of the said turbine rotor with the velocity of fluid injected to the aforesaid vessel from the at least one nozzle, such means comprising sensors to measure these two quantities; and the sensors are electronically linked to the aforesaid valve or valves to adjust the timing and mass of fluid injected to the vessel, such as to compensate for any deviation in rotational speed of the turbine rotor caused by variations in load, and thereby stabilise the rotational speed and power output of the turbine.
6. 6. An engine according to any preceding claim in which the profile of the interior of the turbine rotor housing and that of the turbine rotor disc at the peripheries thereof are so contoured as to guide the transition of the swirl of fluid entering the turbine rotor housing, from a direction co-axial with the turbine rotor to a radial direction inward through the blades of the turbine rotor; and thereafter, guided by the contours of the rotor disc and rotor housing near the rotational centre of the rotor, cause the swirl of fluid to revert to an axial direction and thereabouts exit said turbine rotor and turbine rotor housing.
7. 7. An engine according to any preceding claim in which the blades of the turbine rotor near the rotational centre thereof are curved back opposite the direction of rotation of the rotor, in accordance with prior art and standard practice relating to inward flow radial turbines, to maximise energy transfer from the swirl of fluid as it exits the rotor in an axial direction.
8. 8. An engine according to any preceding claim in which the aforesaid fluid is a gas or combination of gases.
9. 9. An engine according to claim 8 in which the gas or combination of gases is the product of the combustion of a fuel reacting with air in a combustion chamber ancillary to the aforesaid engine, thereby releasing heat energy, the gaseous products of combustion giving up a proportion of their energy in the engine before passing into the atmosphere via an exhaust system.
10. 10. An engine according to claim 8 in which the gas or combination of gases circulates in a closed cycle, being heated in a chamber ancillary to the aforesaid engine by an external source of energy, thereafter giving up a proportion of its energy within said engine, being exhausted from the engine, and pumped around the closed system to return to said chamber by the action of the aforesaid positive displacement means, in conjunction with any other pumping means within the said closed cycle.
11. 11. An engine according to claim 10 in which the gas or combination of gases substantially comprises the inert monatomic gas argon, whereby heat energy applied to the gas in the aforesaid chamber is substantially converted to translational kinetic energy of argon atoms, contributing to greater efficiency in the energy conversion process within the engine.
12. 12. An engine according to claim 8 in which the gas or combination of gases results from heating a liquefied atmospheric gas or combination of gases to an ambient or greater temperature in a chamber ancillary to the aforesaid engine by means of an external heat source, thereby increasing its pressure, the gas or combination of gases giving up a proportion of its energy within said engine, thereafter being discharged into the atmosphere from whence it was originally sourced.
13. 13. An engine according to any preceding claim in which the aforesaid positive displacement means is operated by a mechanism powered by electricity.