GB2040359A

GB2040359A - Turbomachine

Info

Publication number: GB2040359A
Application number: GB8000515A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-01-15
Filing date: 1980-01-08
Publication date: 1980-08-28
Also published as: JPS55117035A; FR2446384A1; GB2040359B; DE3000614A1; FR2446384B1

Abstract

The turbo-machine comprises a compressor (1-3) of the stator-less type, a turbine (5-7) of the stator-less type and a substantially cylindrical wall (4) interconnecting the compressor and turbine rotor walls, the connecting wall comprising a cylindrical wall of metal or heat-insulating material and a continuous or discontinous external reinforcement of a composite material having high mechanical properties. A combustion chamber is provided between the compressor and the turbine. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a turbo-machine The present invention relates generally to a turbomachine capable of serving as a power and/or gas generator and more particularly to a turbo-machine forming a continuous-flow thermal engine.

It is known that turbo-machines offer over the usual thermal machines which are generally piston machines the following advantages: - low weighUpower ratio, - low occupied space/power ratio, and - simple design.

It is also known that it has not hitherto been possible to build a small- or medium-power turbomachine for the following reasons: - The presently known turbo-machines are such that a reduction of their geometrical dimensions lowers their performance level.

It has been found that the sensitivity to the "scale factor" is detrimental to the specific consumption of such machines and that the maintenance of their performances leads to technological difficulties that reduce to nothing the advantage of simplicity offered by the turbo-machines.

- Such turbo-machines are unsuited to partial working conditions less than the nominal working conditions for which they have been designed.

The conventional turbo-machines, such as the conventional turbo-compressors, are constituted usually by an axial-flow or centrifugal compressor with blades secured to a rotor rotating within a stator, a stationary diffuser allowing the velocity of the air at the outlet of the compressor to be reduced by increasing its static pressure, a stationary combustion chamber, a stationary turbine distributor and a turbine constituted by an axial-flow or inwardflow rotor with blades and by a stator. The efficiency of the thermodynamic cycle of the turbo-machines is an increasing function of the following parameters: - the compression ratio : the compressor output pressure to input pressure ratio, and the temperature of the gases before the turbine increasing simultaneously, - the polytropic or isentropic efficiencies of the compressor and the turbine.

The efficiency of the turbo-machines cannot be improved unless one or several of those parameters are improved, but such improvement, as far as small-sized turbo-machines are concerned, comes up against the following difficulties: - the increase in compression ratio obtainable per stage leads to supersonic compressors with which it is not known, at present, how to obtain excellent efficiencies; - the increasing temperature before the turbine is limited by the resistance or stability of the materials and by the difficulty in developing cooling devices of small dimensions; - the increase in efficiency of the components is limited by the friction of the air on the stationary parts of the engine and by the presence of the necessary clearances, the relative importance of which increases with the reduction of the size of the machine.

There are also known high-power turbo-machines which comprise a stator-less, enclosed-rotor type compressor and a stator-less, enclosed-rotor type turbine, i.e. a compressor and a turbine whose blades are rigidly connected or solid, at their upper ends, with the inner surface of revolution of a rotor enclosing wall, the said turbo-machines also including a substantially cylindrical connecting wall interconnecting the enclosing walls of the compressor and turbine rotors and forming therewith a continuous and closed fluid-tight surface defining the volume of the gaseous flow passing through the machine.

In order that such a turbo-machine of small or medium power may be obtained, the connecting wall must be able to withstand the mechanical stresses to which it is subjected and which are due mainly to the centrifugal forces, as well as the stresses of thermal origin which are due to the fact that one of the faces of the connecting wall is internally in contact with the flow of hot gases.

Moreover, the obtention of low specific consumption requires the adoption of a high peripheral speed (the latter varying directly as the compression ratio of the cycle). This peripheral stress may be of the order of 600 m/sec. Since the mechanical stress created by the centrifugal forces varies in proportion to the square of the peripheral speed and to the density of the material in rotation, it is understood that the connecting wall must offer not only a good temperature behaviour also a high specific resistance (ratio of the mechanical resistance to the density of the material considered).

It is known for example that, considering a cylinder in rotation, the theoretically admissible maximum peripheral speeds are 450 m/sec for the light alloys and titanium, are comprised between 450 and 500 m/sec for the best steels, and are of the order of 950 m/sec for the composite materials of the resin and carbon-fibre or like type. Thus, in the case of peripheral speeds higherthan 500 m/sec, the only possibility offered is the use of a composite material of the said type (with the exception of certain very special alloys which give rise to development problems orto cracking strength problems).

However, the mechanical characteristics of such composite materials diminish very rapidly with the increase in temperature, thus making impossible their use in a turbo-machine, in which the temperature of the hot gases may be of the order of 950"C.

In order to solve this problem, there has already been proposed, in the prior art, to surround the wall interconnecting the enclosing walls of the compressor and turbine rotors of a turbo-machine with a stationary casing in which is produced a very high gas or liquid pressure in order to counterbalance the mechanical stresses acting upon the connecting wall as a result of the very high rotational speeds. Under such conditions, the connecting wall may be made of a material known at present.

However, the use of such a stationary external casing filled with gas under pressure suffers from certain drawbacks from the point of view of the occupied space, cooling problems, increase in cost price, and particularly fluid-tightness in rotation owing to the very high gas or liquid pressures within the stationary casing.

The purpose of the invention is precisely to soive all those problems in a simple, efficient and inexpensive manner, by providing a turbo-machine particularly of low or medium power, in which it is not necessary to provide a stationary external casing and a fluid counter-pressure in order to counterbalance the mechanical stresses supported by the connecting wall.

To this end, the invention provides a turbomachine comrising at least one stator-less, enclosed-rotor type centrifugal or axial4low compressor, one stator-less, enclosed-rotor type inward-flow or axial-flow turbine, and a substantially cylindrical connecting wall interconnecting the rotor enclosing wall of the compressor and the turbine and forming therewith a continuous and closed fluid-tight surface, characterized in that the connecting wall comprises a discontinuous or continuous external reinforcement constituted advantageously by a composite material with high mechanical characteristics.

According to another characterizing feature of the invention, the connecting wall is formed of a metal wall associated with the external reinforcement.

According to still other characterizing features of the invention, the connecting wall comprises also a layer of heat-insulating material provided on the internal surface of the metal wall, or a heatinsulating material provided between the metal wall and the said external reinforcement.

The said external reinforcement may be a fibrous composite material with high specific resistance such as composite graphite-epoxy resin material or a composite graphite-polyimide resin material.

The invention will be better understood and other purposes, characterizing features, details and advantages of the latter will appear more clearly as the following explanatory description proceeds with reference to the appended diagrammatic drawings given solely by way of example illustrating several forms of embodiment and wherein:: Figure 1 is a diagrammatic longitudinal sectional view of a turbo-machine according to the invention; Figures2to 6are partial longitudinal sectional views of different forms of embodiment of the connecting wall according to the invention; Figure 7is a cross-sectional view upon the line VII-VII of Figure 6; Figure 8 is an axial sectional haif-view of a turbo-machine according to the invention, with a stationary combustion chamber; Figure 9 is an axial sectional half-view of a turbo-machine according to the invention, with rotational gas-flow combustion; Figure 10 represents a fuel feeding device used in the case of rotational-flow combustion; Figure 11 is a partial sectional view upon the line Xl-Xl of Figure 10;; Figure 12 is a partial sectional half-view of the compressor or the turbine of the machine according to the invention, wherein the two constituent elements of the compressor or the turbine are represented separately; and Figure 13 is a diagrammatic longitudinal crosssectional view of a modified form of embodiment of a turbo-machine according to the invention.

Diagrammatically represented in Figure 1 is a longitudinal sectional view of a turbo-machine constituting an engine, according to the principles underlying the invention. The compression set is constituted by a stator-less, enclosed-rotor type compressor comprising a rotor 1, radial blades 2 and a rotor enclosing wall 3 coaxial with the rotor 1, these elements being rigidly interconnected so as to rotate jointly. The turbine of this engine is an inward-flow turbine comprising a rotor 7, radial blades 6 and a rotor-enclosing wall 5. It will be noted that, according to the invention, either the compressor or the turbine may be of the centrifugal or axial-flow type.

A connecting wall 4 sealingly and continuously interconnects the compressor rotor enclosing wall 3 and the turbine rotor enclosing wall 5. The space 8 defined longitudinally by the rear of the compressor and the front of the turbine, and radially by the connecting wall 4, is provided for gas combustion, which may take place either in a stationary chamber, as illustrated in Figure 8, or under rotational-flow conditions as represented in Figure 9. The gaseous flow passing through the engine is thus limited radially in the compressor by the enclosing wall 3, in the combustion chamber by the connecting wall 4 and in the turbine by the enclosing wall 5.

As has been indicated briefly above, one of the main difficulties in this type of engine arises from the design of the connecting wall 4 which is internally in contact with the hot gasses and which must be able to withstand the centrifugal forces.

Advantageously, a turbo-machine according to the invention is so dimensioned that the hot gaseous flow passing through the turbo-machine has a low relative velocity with respect to the surface of the connecting wall.

The circumferential component of the relative velocity of the flow of hot gases with respect to the surface of the connecting wall is zero, since the velocity of the flow is not reduced. The relative velocity of the flow of hot gases with respect to the surface of the connecting wall is due only to the velocity of the axial movement of the gases, which can be selected of low value, e.g. of the order of 20 m/sec, by increasing the frontal section offered to the gas flow at the outlet of the compressor and at the inlet of the turbine. Under such conditions and in view of the high circumferential speed of the engine, which is for example of the order of 600 m/sec, the heat exchange coefficient on the cold side is much higher than on the hot side. The relative flow of the ambient air, which is relatively cold, outside the connecting wall has considerable velocity and therefore allows the connecting surface to be cooled intensively. For this reason, use can be made, for the connecting wall, of reinforcing materials which have not necessarily very good resistance to heat.

In Figures 2 to 6 are shown partial longitudinal sectional views of various forms of embodiment of a connecting wall according to the invention, the design of which is based upon the afore-mentioned considerations.

The connecting wall 4 represented in Figure 2 comprises a metal wall 4A which is directly in internal contact with the flow of hot gases and the mechanical resistance of which to the centrifugal forces is ensured by external reinforcing rings 4C of composite material, rings 4B of heat-insulating material being provided between the external face of the metal wall 4A and reinforcing rings 4C.

The metal wall 4A may be for example a thin sheet (e.g. of a thickness of the order of 0.6 mm) of aluminim or titanium alloy, the rings 4B of insulating material may be made of glass ceramic and have a thickness of the order of 0.2 mm, and the reinforcing rings 4C may be made of a composite material of carbon fibres and polyimide or epoxy resin, which are spaced a few millimetres apart and the thickness of which is for example of the order of 6 to 7 mm.

Under such conditions, the metal wall 4A, in contact with the ambient air by its external surface, is strongly cooled and is used at a temperature at which its mechanical characteristics are preserved, particularly in the case of titanium alloys, by the discontinuous external reinforcement constituted by the reinforcing rings 4C, and on the other hand, it transmits only an extremely small thermal flow to the composite material forming the reinforcing.rings 4C owing to the presence of the insulating rings 4B, According to two other forms of embodiment of the invention which are represented in Figures 3 and 4, the connecting wall 4 comprises successively a layer of heat-insulating material, a metal wall and a continuous or discontinuous external reinforcement of the afore-mentioned composite material.

In Figure 3, the connecting wall 4 comprises an internal layer 4D of the afore-mentioned heatinsulating material, the afore-mentioned metal wall 4A, and a continuous external reinforcement 4E constituted by a layer of the afore-mentioned composite material.

In the form of embodiment of Figure 4, the connecting wall 4 also comprises the internal layer 4D of heat-insulating material, the afore-mentioned metal wall 4A and a discontinuous external reinforcement 4F of the afore-mentioned composite material, constituted by spaced reinforcing rings.

In the forms of embodiment of Figures 3 and 4, the heat-insulating material 4D does not fulfill a force transmitting function as in the case of Figure 2 and may be of an insulating material without particular mechanical characteristics.

In the form of embodiment represented in Figure 5, the connecting wall 4 is constituted by the afore-mentioned metal wall 4A and by the continuous external reinforcement 4E of Figure 3, the metal wall 4A provided externally with metal points 4G passing at least partially through the composite material constituting the external reinforcement 4E.

This arrangement allows the thermal conductibility and therefore the cooling of the connecting wall to be increased without reducing its mechanical resist ante which is ensured by the external reinforcement 4E, the characteristics of which are not affected by the presence of the points 4G.

According to still another form of embodiment of the invention, the connecting wall may consist of a substantially cylindrical wall of heat-insulating material and of a continuous or discontinuous external reinforcement of a composite material having high specific resistance.

According to still another form of embodiment of the connecting wall 4; a screen substantially coaxial with the connecting wall may be arranged interiorly of the latter and bear thereon through the medium of longitudinally extending spacers. The said screen serves to reducathe heat exchange through radiation and convection with the internal portion of the connecting wall. The longitudinal arrangement of the spacers allow spacers to be provided therebetween for the circulation of part of the air taken at the outlet of the compressor for cooling the screen and the connecting wall.

This form of embodiment is illustrated in Figures 6 and 7. In this case, the connecting wall 4 comprises an internal metal layer 4H fulfilling the function of a thermal screen, an intermediate layer 41 of heatinsulating material and an external, continuous or discontinuous reinforcement 45 of the aforementioned composite material.Longitudinal passages 4K are provided in the heat-insulating material 41 to allow the circulation of the cooling air taken at the outlet of the compressor and are separated from one another by lower ribs 4L of heat-insulating material which fulfill the function of spacers to transmit the centrifugal forces from the metal layer 4H to the mechanically resistant porton 4J of the connectingwall Moreover, orifices 4M may be provided in the metal layer 4H to allow air to diffuse from the passasges 4K towards the interior of the engine, thus increasing the thermal protection of the metal layer 4H by means of a superficial air film.

According to a modified form of embodiment, the said passages may be provided in the insulating material, e.g. the glass ceramic material, in which case the metal layer 4H can be dispensed with.

Of course, the means of mechanical reinforcement and thermal protection of the connecting wall, which have been described in connection with Figures 2 to 7, may be interrupted locally in accordance with machining or mounting requirements.

There will now be described in more detail, with reference to Figure 8, a turbo-machine according to the invention comprising a stationary combustion chamber.

It is known that in a turbo-machine according to the invention the absence of a diffuser has the disadvantage of reducing the static pressure of the combustion air and therefore of reducing the efficiency of the thermo-dynamic cycle. However, this disadvantage is largely compensated for by the following advantages: - the increase in efficiency of the compressor and the turbine, as already explained; - the possibility offered by the turbo-machine according to the invention to rotate at much greater speeds than the conventional machines and therefore to increase the compression ratios; - the possibility of increasing the temperature of the gases before the turbine owing to the possibilities of intensive cooling of the engine.

It is possible, however, in order to improve the quality of the thermodynamic cycle, to effect the combustion after recompressing the flow emerging from the compressor, this recompression taking place without producing shock waves. It is indeed known that the losses resulting from shock waves increase at the same time as the Mach number of the flow. This Mach number may be reduced when the flow velocity is constant by increasing the temperature of the gases (M = V/#mrt).A device according to the invention, illustrated in Figure 8, allows this circumstance to be used and therefore the combustion to be effected under static pressure without however producing shock waves during the gas recompression.

Thus, according to the form of embodiment illustrated in Figure 8, the combustion chamber is stationary, substantially in the shape of a body of revolution, and is provided on its external portion with one or several air intakes immersed in the gaseous flow emerging from the compressor, each air intake being so arranged as to pick up a portion of the gaseous flow and introduce it into the combustion chamber, which, on the other hand, is provided with at least one combustion gas reintroducing orifice upstream of the air intake or intakes. The increase in temperature of the gaseous flow incident upon the air intakes allows the Mach number of the flow in this region to be reduced.

The turbo-machine represented in Figure 8 comprises the essential elements already described, namely, those of the compressor, i.e. the rotor 1, the blades 2, the rotor enclosing wall 3, those of the turbine, i.e. the rotor 7, the blades 6, the rotor enclosing wall 5, and the connecting wall 4 between the compressor and turbine rotor enclosing walls.

The stationary combustion chamber 8 is interiorly defined by a cylindrical wall 14, exteriorly by a wall 9, and longitudinally by transverse walls interconnecting the walls 9 and 14. Air intakes 10 in the form of scoops, bails, piggins or the like are provided on the external face of the wall 9 to pick up a portion of the gaseous flow emerging from the compressor and introduce it into a tranquilization chamber 11 formed within the wall 9. The tranquilization chamber 11 communicates through orifices 12 with the combustion chamber proper 8. Orifices 13 are provided in the external wall 9, upstream of the air intakes 10, for reinjecting the combustion gases emerging from the chamber 8 into the gaseous flow emerging from the compressor.

Also shown in Figure 8 is a method of fastening of the connecting wall 4, by screwing at 15 and 16, on the compressor and turbine rotor enclosing walls 3 and 5, reinforcements 17 and 18 being provided exteriorly in the region of the fastening means 15 and 16. Moreover, thisturbo-machine, the rotational speeds of which may reach particularly high values, is supported by self-feeding gas bearings 19 and 20 or by magnetic bearings. The axial thrust supporting means are not represented in the drawing.

According to another form of embodiment of a turbo-machine according to the invention, the com bustion can take place without the velocity of the flow at the outlet of the compressor being reduced (rotational flow).

This form of embodiment is diagrammatically illustrated in Figure 9. In this case, an engine of very compact design can be obtained by rigidly interconnecting the compressor and turbine rotors, the combustion then taking place in the space remaining between the compressor and the turbine.

The combustion chamber 8 is thus defined radially by the internal surface of the connecting wall 4 and by a metal part 21 rigidly interconnecting the compressor and turbine rotors 1 and 7. The fuel may be introduced into the engine in gaseous form through the compressor inlet and mix up with the air sucked by the compressor In this case, the engine has no axial passage for fuel supply or for the ignition system, thus avoiding the weakening of the rotating parts. Ignition can be obtained by means of spiral located in a magnetic field and intended to feed an electric arc, or by external electric contacts, or by a piezo-electric system.The compressor rotor 1, the connecting part 21 and the turbine rotor 7 can be machined from a single solid piece so as to lower the operating temperature of the connecting part 21 and the turbine rotor 7, by cooling the connecting part 21 atthe compressor rotor 1 by heat exchange through convection with the suction air and/or the ambient air.

In the case of rotational flow combustion as described with reference to Figure 9, and when the fuel is admitted in gaseous form at the suction side of the compressor, it may be found advantageous to separate the flow of fuel and of air necessary for its combustion from the flow of sucked air excess, so as to introduce separately the two flows in the region of the combustion chamber, the excess airflow being introduced at the periphery of the combustion chamber and the air/fuel mixture flow being introduced in a lower region towards the interior of the engine, so as to preserve a sufficient richness of the air/fuel mixture and to thermally protect the external wall with the excess airflow. This excess airflow may advantageously be introduced for example in the region of the inlet of the passages 4K of the connecting wall represented in Figures 6 and 7.

Figures 10 and 11 show such a device according to the invention, wherein the compressor rotor 1 is provided with substantially radical passages 29 which are closed at their top by a thin sheet 22 sealingly secured on the rotor 1,so that the air/fuel mixture is introduced at the passages 29 and the excess air is normally sucked into the space provided for this purpose between the blades 2 and the compressor rotor enclosing wall 3. The passages 29 open radially in a region below the compressor outlet so that the combustion does not take place -against the wall and the richness of the mixture is sufficient.

Also represented in Figure 10 is an ignition system comprising spirals or coils 25 of electrically conductive material mounted for example on the external surface of the compressor rotor enclosing wall 3, which are intended to pass in a magnetic field represented in the drawing by a magnet 26. The spirals 25 are connected by conductors 27 to two electrodes 28 placed in the combustion chamber 8 slightly beyond the outlet of the passages 29. The ignition of the fuel mixture is obtained by means of an electric arc between the electrodes 28 when the spirals 25 cut the magnetic field.

In Figure 12 is illustrated a particularly simple form of embodiment allowing easy manufacture of the compressor and/or the turbine of the turbo-machine according to the invention. In this case, the compressor rotor or turbine rotor 1 or 7 consists of a solid disc in which are milled radial slots, and comprises a portion of substantially conical shape 23 in which is made a bore 27, the other portion of the compressor or the turbine being constituted by a corresponding male portion intended to be fitted into and rigidly secured in this female portion, the male portion being constituted by-the compressor or the turbine rotor enclosing wall, the blades 2 or 6 and a central hub adapted to be fitted respectively into the portions 23 and 24.This structure allows, on the one hand, these parts to be of simple design, and on the other hand, the mechanical stresses exerted thereon to be separated and therefore the said parts to be made of different materials, the rotor enclosing wall 3 being the most loaded part mechanically owing to its large central bore, but capable of being cooled quite well, and the part 1 being less loaded mechanically but on the other hand much more heated (in the region of the turbine).

Lastly, there is diagrammatically shown in Figure 13 a complementary characterizing feature of the invention, according to which the-compressor rotor and the turbine rotor enclosing walls 3 and 5 and the connecting wall 4 are coaxially surrounded with a stationary externs casing 30 which is open at its longitudinal ends 31 and 32.

The casing 30 serves to limit the renewal of the air surrounding the turbo-machine, so that the air contained in the casing 30 may be entrained in rotation when the turbo-machine is operating, and thus be imparted a peripheral velocity which is equal to about half the peripheral speed of the turbo machine. Thus, the relative speed between the external walls of the turbo-machine and the sur rounding air is reduced by half and so is the moment of friction between these external walls of the turbo-machine and the surrounding air. The power consumption due to the friction between the sur rounding air and the external walls of the turbo machine is thus considerably reduced.

Furthermore and surprisingly, the efficiency of the cooling of the connecting wall 4 is at least preserved and even improved. Indeed, the cooling depends upon two main factors: the thermal exchange coeffi cient and the difference in temperature between the wall and the surrounding air. The thermal exchange coefficienty varies substantially as the relative speed and it is therefore reduced by half when the sur rounding air is entrained at a velocity equal to half the peripheral speed of the walls. On the other hand, the temperature of the surrounding air varies as the square of the relative Mach number. It is of the order of 50"C when the air is entrained and it is of the order of 1 500C when the air is stationary.The admissible maximum wall temperature being of the order of 250"C, the possible difference in temperature with respect to the surrounding air is therefore 200"C in the first case and 1 000C in the second case. Consequently, the thermal exchange cofficient loss is largely compensated for by the gain in different in temperature and the cooling efficiency is thus increased.

According to the invention, compressor blades 33 may also be provided between the compressor rotor enclosing wall 3 and the external casing 30, these blades being mounted on the compressor rotor enclosing wall 3, and turbine blades 34 may be provided between the turbine rotor enclosing wall 5 and the external casing 30, these blades being mounted on the enclosing wall 5. The radial height of the blades may be so selected as to obtain precisely the desired relative speed between the casing and the air flow.The flow produced by the blades rotating within the casing 30 may be recovered at the outlet of the casing 30 to produce energy, e.g. for increasing the output power of the turbo-machine. This arrangement therefore allows the recovery of a very large portion of the energy lost by the turbo-machine as a result of friction between its external walls and the surrounding air.

It will also be noted that there may be provided in the rotational flow combustion chamber of the type described in Figure 9 flame stabilizing means which may comprise for example a substantially annular element 35 of incombustible cellular material with open cells, which material may be an exploded foam or carbonized or graphitized polyurethane, coated with an-anti-oxidant- material (carbide or metalliz- ing), allowing the combustion to take place in a localized area sheltered from turbulence.

Of course the invention is by no means limited to the forms of embodiment described and illustrated which have been given by way of example only. In particular, it comprises all means consistuting technical equivalents to the means described as well as their combinations, should the latter be carried out according to its gist and used within the scope of the following claims.

Claims

1. A turbo-machine comprising at least one centrifugal or axial-flow compressor of the stator-less enclosed-rotor type, one inward-flow or axial-flow turbine of the stator-less enclosed-rotor type, and a substantially cylindrical connecting wall interconnecting the compressor and turbine rotor enclosing walls and forming therewith a continuous and closed fluid-tight surface, characterized in that the said connecting wall comprises a discontinuous or continuous external reinforcement constituted advantageously by a composite material displaying high mechanical characteristics.

2. A turbo-machine according to claim 1, characterized in that the connecting wall is constituted by a metal wall associated with the said external reinforcement.

3. Aturbo-machine according to claim 2, char acterized in that the connecting wall comprises moreover a layer of heat-insulating material provided on the internal surface of the metal wall.

4. Aturbo-machine according to claim 2, characterized in that the connecting wall comprises moreover a heat-insulating material provided between the metal wall and the said external reinforcement.

5. A turbo-machine according to one of claims 2 to 4, characterized in that the metal wall comprises external metal points penetrating into at least a portion of the thickness of the external reinforcement.

6. Aturbo-machine according to claim 1, characterized in that the connecting wall is constituted by a substantially cylindrical wall of heat-insuiating material and of the aforesaid external reinforcement which is continuous and substantially cylindrical in shape.

7. Aturbo-machine according to claim 1, characterized in that the connecting wall comprises an internal protecting screen rigidly assembied to the connecting wall and defining therewith passages for the circulation of air taken at the outlet of the compressor.

8. A-turbo-machine according to claim 7, characterized in that the said screen is provided with holes for the diffusion of cooling air.

9. Aturbo-machine according to one of the foregoing claims, characterizied in that the combustion chamber is of the rotational flow type and is defined radially by the said connecting wall and by a connecting part or element rotating jointly with the compressor and turbine rotors, and axially by the compressor and turbine rotors.

10. Aturbo-machine according to claim 9, characterized in that the compressor rotor comprises passages for the supply of fuel mixture into the combustion chamber.

11. Aturbo-machine according to one of claims 9 and 10, characterised in that the fuel is introduced in the form of gas or mist at the suction side of the compressor.

12. A turbo-machine according to one of claims 9 toll, characterized in that the combustion chamber comprises a flame-stabilizing device constituted for example by an element of incombustible cellular material with open cells.

13. Aturbo-machine according to one of claims 1 to 8, characterized in that the combustion chamber is fixed in rotation and is located in the space defined axially by the turbine and compressor rotors and radially by the connecting wall, the said chamber being substantially cylindrical in shape and provided on its external wall with one or several air-intakes located within the gaseous flow furnished by the compressor, and with at least one orifice upstream of the air-intakes for the reintroduction of the combustion gases into the gaseous flow.

14. Aturbo-machine according to one of the foregoing claims, characterized in that the ignition of the fuel mixture is effected by a piezo-electric or electromagnetic system.

15. Aturbo-machine according to one of the foregoing claims, characterized in that it comprises moreover a stationary external casing coaxially surrounding the compressor and turbine rotor enclosing walls and the said connecting wall, and which is open at its longitudinal ends.

16. Aturbo-machine according to claim 15, characterized in that compressor blades and turbine blades are provided between the compressor and turbine rotor enclosing walls respectively, on the one hand, and the said stationary external casing on the other hand.

17. A turbo-machine substantially as described herein with reference to and as shown in the accompanying drawings.