US3678306A

US3678306A - Jet propulsion power plant

Info

Publication number: US3678306A
Application number: US106378A
Authority: US
Inventors: Michel Robert Garnier; Christian Paul Gilbert Rioux
Original assignee: SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 1970-01-15
Filing date: 1971-01-14
Publication date: 1972-07-18
Anticipated expiration: 1989-07-18
Also published as: DE2101919A1; GB1341241A; FR2085190A1; FR2085190B1; DE2101919B2; DE2101919C3

Abstract

A jet propulsion power plant comprising in succession a compressor, a supplemental heating means, an expansion gas turbine, a main heating means, and a magnetoplasmadynamic generator adapted to supply at least a part of the energy necessary for driving the compressor. The compressor is driven by an electrical motor means electrically connected to the magnetoplasmadynamic generator and to a supplemental generator rotated by the expansion gas turbine.

Description

bio-11 GR 3 @678E306 Garnier et a].

51 July 18,1972

JET PROPULSION POWER PLANT Inventors: Michel Robert Garnier, Sceaux; Christian Paul Gilbert Rioux, Antony, both of France Assignee: Societe Nationale DEtude Et de Construction de Moteurs DAviation, Paris, France Filed: Jan. 14, 1971 Appl. No.: 106,378

Foreign Application Priority Data Jan. 15, 1970 France ..7001440 U.S. Cl ..310/l1, 60/202 Int. Cl. ..l-l02n 4/02 Field of Search ..3 10/10, 1 1; 60/202; 417/50 [56] References Cited UNITED STATES PATENTS 3,527,055 9/1970 Rego ..310/11 X 3,309,546 3/1967 Boll ..310/11 3,585,398 6/1971 Harvey ....310/178 2,914,688 11/1959 Matthews..... ....3l0/178 3,508,090 4/ 1970 Crampton .310/1 1 Primary ExaminerD. X, Sliney Attomey-William J. Daniel [57] ABSTRACT A jet propulsion power plant comprising in succession a compressor, a supplemental heating means, an expansion gas turbine, a main heating means, and a magnetoplasmadynamic generator adapted to supply at least a part of the energy necessary for driving the compressor. The compressor is driven by an electrical motor means electrically connected to the magnetoplasmadynamic generator and to a supplemental genera tor rotated by the expansion gas turbine.

14 Clains, 12 Drawing Figures PAIENTED JUL 1 8 m2 SHEEI 1 BF 7 PATENTED JUL 1 8 I972 SHEET 6 0F 7 w DE PAIENIFU JUL] 81972 'SHEET S [If 7 PATENTED JUL] 8 I972 SHEET 8 [IF 7 PATENIEI] Jun 8 m2 sum 7 7 mm y JET PROPULSION POWER PLANT This invention relates to power plants, particularly for the jet propulsion of aircraft, comprising at least one mechanical compressor for compressing a flow of gas and heating means adapted to raise this flow of gas to a high temperature it has the general object of improving the performance and the efficiency of such power plants.

Power plants of this type hitherto known comprise usually at least one air compressor, one or more heating or combustion chambers, and at least one jet pipe. Usually the com pressor is mechanically connected to an expansion turbine located in the path of the hot gases between the combustion or heating zone and the jet pipe, taking from these gases the energy required to drive the compressor. Prior to discharge, the gases may be subjected to reheat or in a reheat chamber located downstream of the turbine.

The improvement of the performances of power plants of this type and which are known generally under the name of turbojet engines, is difficult for several reasons l. The turbine which supplies the whole energy for driving the compressor and which is necessarily located downstream of the heating or combustion chamber, can resist only rather limited thermal stresses. So far no technique is known which makes it possible to construct turbine blades which can resist temperatures substantially higher than l,000. In consequence, the temperature prevailing in this unit must not exceed a certain limit which thereby determines the upper value of the efficiency of the thermodynamic cycle in the power plant.

2. In the case where the gases are reheated they may be raised in the reheat chamber to an obviously higher temperature. However, the compression ratio which characterises the reheat is necessarily low and the thermodynamic efficiency is also low owing to the very considerable drop of the gas pressure across the turbine located upstream of the reheat chamber.

3. Finally, the direct mechanical connection between the turbine and the compressor imposes generally a fixed speed ratio on these elements which prevents the power supplied by the turbine to the compressor from being varied in the most desirable manner. This drawback becomes more marked as the flying speed increases. It can be reduced in its effects by various means, such as the division of the compressor and of the turbine into several stages or spools which rotate at different speeds, or the use of variable-geometry air intakes. However, these devices have only a comparatively limited efficiency, particularly in view of their secondary drawbacks.

There are also known the ramjet engines these power plants do not contain a mechanical compressor or a turbine. For this reason, the heating or combustion chamber of such a power plant may withstand very high temperatures, but it is only at substantially supersonic speeds that the dynamic compression in the air intake becomes sufficiently high for the output to be of significance. At low flying speeds, the thrust is very low and auxiliary propulsion means of substantial power must be used in conjunction with the ramjet to bridge the large speed range in which it is itself inoperative.

To this end, compound power plants have been constructed, which combine at least one ramjet engine and one turbojet engine in the same installation. However, quite apart from the fact that the close association of these two types of engines necessarily reduces the performance of each of them separately, it limits particularly the maximum flying speed to a value which is substantially lower than that at which the ramjet alone is of particular interest this association also gives rise to great difficulties because the flying speed ranges at which the turbojet engine and the ramjet have a suitable specific thrust are fairly wide apart, so that there exists a gap for overall thrust in an intermediate region of Mach numbers, and this gap is fairly wide.

In order to remove or at least substantially reduce these drawbacks of the two main types of power plants mentioned above, and of their combinations (resulting for turbojet engines from the presence of a turbine which supplies the whole of the energy required for driving the compressor or compressors, and for ramjet engine from the absence of a mechanical compressor), the invention provides a power plant comprising at least one mechanical compressor adapted to compress a gas flow and heating or combustion means adapted to raise this flow of gas to a high temperature, wherein one part of the energy necessary for driving the compressor is taken from the hot gas, at least under certain operating conditions of the power plant, by means of a device using only fixed elements and capable of withstanding very high temperatures. To this end a power plant according to the invention comprises a magnetoplasmady dynamic generator, also called a magnetohydrodynamic generator, the converter channel of which carries the gas flow at high temperature before this flow is discharged and takes from the gas flow at least a part of the energy required for driving the said compressor.

Prior to describing in detail the means used by the invention it might be useful to describe briefly the general configuration and the operation of a magnetohydrodynamic generator, in the following referred to as Ml-ID generator or MHD channel."

Under the action of a suitably orientated magnetic field B (see FIG. 2), the electrical charges freed by partial ionisation of a gas flow limited by the walls of a so-called MHD conversion channel, in which the gas achieves a velocity V, are subjected to a force, the so-called Lorentz force, acting perpendicularly to the velocity and to the field. If two conducting electrodes are arranged to limit the conversion channel laterally, preferably parallel to the plane of the vectors B and V, an electromotive force is created between them, proportional to their spacing, to the gas velocity, and to the intensity of the field. In this, the Ml-lD generator behaves like an ordinary electrical machine whose moving armature in the magnetic field is not an assembly of solid conductors but a gaseous continuum which is rendered conducting by ionisation.

The conductivity of the gas depends substantially on its ionisation rate. he ionisation may be produced by thermal means and the gas may be raised to a high temperature of the order of 3,000 K. Under certain conditions, such'temperatures may be produced by combustion of a conventional propulsion fuel in a flow of compressed air. At such a temperature, the ionisation may be increased by the injection of chemical elements of low ionisation potential. To this end, the gas stream may be seeded, e.g., by injection, upstream of the MHD channel, with a small quantity of any salt of an alkali metal, such as potassium.

The drive of the compressor by the energy supplied by the MHD generator may be effected by electric motors of high mass power, for example by homopolar motors equipped with superconducting field coils. More particularly, it is possible to use for this purpose the arrangements described in the applicants concurrent US. Pat. application Ser. No. 106,380 filed this same date under the title: Improvements in or Relating to Gas Turbine Power Plants.

The invention also relates to other arrangements suitable for use in conjunction therewith but also capable of being used independently.

The following description given by way of example with reference to the accompanying drawings, shows how the invention may be carried into practice.

In the drawings FIG. 1 is a diagrammatic view in axial cross-section of a first embodiment of a power plant according to the invention FIGS. 2 and 3 are diagrammatic views showing, respectively, an axial cross-section and a perspective view of details of an MHD conversion channel forming part of the installation shown in FIG. 1

FIG. 4 is an axial cross-section of a compressor forming part of the installation shown in FIG. 1

FIG. 5 is a diagrammatical view in axial cross-section of a modification of a compressor forming part of the installation shown in FIG. 1

FIG. 6 is a more detailed view of the compressor of FIG. in cross-section FIGS. 7a and 7b show, in axial cross-section and in elevation, respectively an armature of an electric motor associated with one of the stages of the compressor shown in FIG. 6

FIGS. 8 and 9 show a second embodiment of the invention according to which the energy for driving the compressor is supplied by two separate electrical generators, one of which is formed by the MHD generator, and the other by one or more rotating machines driven by a turbine FIG. 8 is a partly diagrammatical cross-section of a power plant in which these two separate electrical generators are mounted in parallel FIG. 9 is a diagrammatical cross-section which shows the electric circuitry of a power plant assembly in which the said two separate electric generators supply independent circuits FIG. 10 is a more detailed axial cross-section, showing particularly a compressor body, the turbine and the main conductors of the electric circuit of the power plant shown in FIG. 9

FIG. 11 is a development showing a detail of the armature of the turbine according to FIG. 10.

The jet propulsion power plant shown diagrammatically in FIG. 1 comprises in the direction of flow, within a housing 100, a multi-stage rotary compressor 101a, 1011: and 1010, a combustion or heating chamber 102 and an MI-ID generator, the conversion channel 103 of which communicates at 104 with a jet pipe for the propulsion gases, not shown. Under normal running conditions the energy for driving the compressor is supplied by the MHD generator which supplies three electric motors of high mass power, shown diagrammatically at 105a, 105b and 1050, and driving, respectively, the stages 101a, 10lb and 101c of the compressor. These stages are mechanically independent of each other and may have a similar construction or not. A particularly advantageous em bodiment will be described further below in detail and by way of example. However, the subdivision of the compressor into three independent stages is not limitative and another advantageous embodiment of this compressor will also be described further below.

The combustion or heating chamber 102 is provided with heating means including burners 106 and flame holders 107 which mayhave a comparatively conventional construction. The burners 106 are connected by conventional means, not shown, to a fuel tank. he fuel may be, as mentioned above, a conventional propellant such as used in jet propulsion engines. In order to ensure that the combustion temperature is the highest possible, the fuel delivery is such that the combustion is substantially stoichiometric. Nozzles, not shown, which may be associated with the burners 106, make it possible to prime the flow of gas by injection with a powder of an alkali metal salt, such as for example potassium carbonate. As already mentioned above, this method will result in a substantial increase of the conductivity of the hot gases.

The MI-ID generator, shown generally at 103, comprises an annular channel defined by an inner wall 108 and an outer wall 109 which form the electrodes. It will be described in greater detail further below.

The annular construction of the MHD channel shown at 103 has the advantage of being comparatively well adapted, on one hand, to obtaining a moderate electromotive force which is desirable for the type of electric motors (described further below) which it supplies, and on the other hand to the overall geometric layout which is generally used in power plants. However, it should be noted that other configurations can also be used for example, the MI-ID generator may comprise a conversion channel with rectangular cross-section in which the electrodes are arranged along two opposite faces of the channel.

The motors 105a, 1051; and 1056 are connected on one hand in series by means of conductors 110a and 110b, and on the other hand to

electrodes

108 and 109 of the MHD generator by

conductors

111 and 112 indicated in dotted lines. The conductor 111 may be formed by a solid cylinder which is electrically insulated from the housing 100, and firmly mounted thereon, for example by radial arms, not shown, thereby contributing to the rigidity of the assembly. The conductors a and 110b as well as the upstream part of the conductor 112 may be formed by sections of a hollow cylinder fitted on to the center cylinder 111, and electrically insulated against the same, for example by a layer of alumina. A ring of fixed vanes 113 of the last element 101c of the compressor may be used as the cross conductor of the flow of gas. Finally, the part of the conductor 1 12 which connects the ring of fixed vanes 113 to the outer electrode 109 of the MHD generator may be formed by the housing 100 itself.

FIG. 2 shows in greater detail the arrangement of the MHD generator in FIG. 1, and particularly the orientation of the electrical currents and of the magnetic field.

The

cylindrical electrodes

108 and 109 are arranged coaxially and define the annular channel 103. They may be made from a refractory material which is a hot conductor, and based on zirconium, or any other means whereby high current densities in contact with the flow of gas can be obtained and supported. A magnetic field B the direction of which at all points of the channel 103 is substantially perpendicular to the axis and parallel to the walls, is generated by windings shown diagrammatically at 114 and carrying an inducing current I,,,,,, whose overall path is contained in axial planes. The direction of arrows j is that of the vector which represents the current density in the ionized gas flow, corresponding to the directions indicated for the current I flowing across the field windings 114 and for the gas flow.

FIG. 3 shows diagrammatically the configuration of the field windings 114 in FIG. 2. These windings comprise two panels or sheets of conductors 1150, 115b in parallel arrangement and extending substantially axially, distributed uniformly outside the gas flow in close proximity to each of the electrodes. In each of these two sheets, the conductors are connected to each other in pairs so as to form a plurality of frames of rectangular configuration the axial ends of each frame 115a are each connected by a conductor 116 to a corresponding end of a frame of the other sheet 115b. This arrangement makes it possible to produce the equivalent of a torus-shaped winding, whilst permitting the conductors 116 to be grouped within the comparatively few radial arms 117 without producing a heterogeneity of the field which might impair the good functioning of the MHD generator.

In order to reduce the dimensions of the MHD channel and thus also its weight and the magnitude of losses by heat radiation from its walls, it is desirable to employ very strong magnetic fields. To this end, it is possible to use superconducting field windings which, in spite of the cryogenic arrangements which are necessary, are much lighter than conventional electromagnets which have metal pole shoes and are cooled by a liquid under high pressure in addition, there is also the advantage of an almost negligible consumption of electric power. These windings may be formed, for example, from an alloy of niobium and titanium and are located in cryogenic sleeves which contain circulating liquid helium, wherein these sleeves may possibly be cooled themselves by circulating liquid nitrogen.

FIG. 4 represents in axial cross-section one of the stages of the compressor which forms part of the installation shown in FIG. 1. This element comprises, as known in the prior art, a series of fixed vane rings, such as 118, mounted on the housing 100 and alternating with a series of rotating blade rings such as 119 which are mounted on a drum which rotates in

bearings

121 and 122.

The drum is rotatively driven by a homopolar electric motor comprising an assembly of elements in the form of alternating fixed discs 123, and rotating discs 124, and a field coil 125 held by a ring 126 made in one piece with a rim 131 ofa fixed ring of vanes 118.

The assembly or stack of rotating discs 124 forms the actual armature of the homopolar motor these discs are mounted at their outer edges on the drum 120, but are electrically insulated against the same. The fixed discs 123, located between the rotating discs 124, make electrical contact between the outer circular edge, forming the electric terminal of a rotating disc, and the inner circular edge forming also an electric terminal of the adjacent disc through rotating contacts such as 127 which may preferably be formed by a ring of liquid metal this arrangement has been described in the above-mentioned patent application. Finally, the outermost discs 123a and 124a make contact, respectively, with

cylindrical conductors

128 and 129, between which is mounted a cylindrical insulating sleeve 130 on which are mounted the fixed discs other than 123a.

The field coil, shown generally at 125, is formed by a superconducting winding surrounded by a cryogenic sleeve this winding is formed by coaxial turns. The arrow B represents the direction of the lines of the magnetic field generated by the coil 125. In the region occupied by the discs 124, the field B is substantially homogeneous and axial. The arrows I represent the path of the electrical current across the armature it may be seen that the current passes through each of the discs 124 in the same direction. It follows therefrom that the Laplace forces caused by the field B and current I generate in each of the discs 124 electrodynamic moments in the same direction.

The construction of the other elements of the compressor shown in FIG. 1 may in all respects be similar to that shown in FIG. 4 just described. The annular conductor 129 (FIG. 4) of the first element 101a FIG. 1) is thus formed from a single piece with the annular conductor 128 (FIG. 4) of the second element 10112 (FIG. 1), and their assembly forms the conductor shown diagrammatically at 110a in FIG. 1. The conductor shown diagrammatically at 11011 in FIG. 1 may be built in a like manner. Finally, the annular conductor 128 (FIG. 4), corresponding to the first element 101a, rests directly on the end of the center cylinder 111 and forms thereby an electrical contact which closes the electric circuit in which the armatures of the motors are connected in series to the electrodes 108 and 109 (FIG. 1) of the MHD generator, in the manner indicated in FIG. 1.

The arrangement shown diagrammatically in FIG. 5 shows another embodiment of a compressor adapted to form part of the installation in accordance with the invention. As in the first case, this compressor is rotatively driven by electric motors 205 of high power, connected in series by conductors 210, whilst

conductors

211 and 212 connect the assembly of these electric motors to the electrodes of the MHD generator (not shown). However, the compressor shown in FIG. 5 has independent counter rotating discs and the motors 205 each drive a single ring of blades, wherein the rings 219a rotate in one direction and the adjacent rings 21% rotate in the opposite direction. The direction of the flow of gas is indicated by an arrow F.

FIG. 6 shows an embodiment of the compressor shown diagrammatically in FIG. 5. This compressor may comprise eight rings of counter rotating blades 219 which are rotatively mounted, by means further described below, on the hollow cylinder 211 which is fixed and serves as electrical conductor and as housing for the compressor assembly. The cylinder 211 may be mounted, for example, by means of radial arms (not shown) on the housing (not shown) which defines the gas flow to the periphery of the blades, as known in the art.

Each stage of the compressor comprises a ring of fixed vanes 219 mounted on a rim 231 forming part of a disc 224 which forms the armature of the homopolar motor with which it cooperates. On either side of each armature 224 and coaxial relative thereto are arrange superconducting field windings 225, surrounded by a cryogenic shell 225a which contains circulating liquid helium and is supported by fixed elements such as discs, indicated by

reference numerals

223, 223a, 223b, forming mechanically part of the cylindrical support 211 and electrically insulated therefrom by a layer of alumina, not shown.

The electrical windings 225 carry currents in the same direction and form an axial magnetic field, the lines of which are indicated by arrows B.

The inner circular edge of the armatures 224 (with the exception of the first ring of blades in the upstream direction) forms a first electric terminal which rests on one of the lateral ends of a cylindrical arrangement 228 of fixed discs 223a by means of a rotating contact 227a of liquid metal. The armatures 224 have on their periphery a circular shoulder 224a which forms a second electric terminal resting through another rotating contact 227b of liquid metal on a conducting ring 229, which is made in one piece with the fixed discs 223b which alternate in the axial direction with the fixed discs 2230.

In the upper part of the zone located between two consecutive field windings 225, the field B- has a substantial radial component. The orientation of the armatures 224 evolves therefore and presents an inclined part 2241; in the corresponding zone. It may also be noted that the outline of the surfaces which define the

rotating contacts

227a and 227b is substantially parallel to the lines of the field B in their vicinity. In this manner, it may be avoided that parasitic currents may arise within the liquid metal during rotation, which would lead to considerable losses.

It may also be seen in FIG. 6 that the general arrangement of the armatures is such that the assembly formed by two consecutive armatures is generally symmetrical relative to the median plane of the fixed disc 223a or 223b, mounted between these armatures. It may also be noted that the arrangement of the first and of the last stage of the compressor differs from that of the intermediate stages in that the rotating contact 227'a of the first stage is made directly with the center cylinder 211, and the cylindrical stack portions 228' of the last fixed disc 223a is formed by an extension of an annular conductor 212 which surrounds the conductor 211. The

conductors

211 and 212 are connected to the MHD generator, for example in the manner shown in FIG. 1, in which their equivalents are the

conductors

111 and 112, respectively.

The arrows I in FIG. 6 indicate diagrammatically the path of the feed current of the armatures 224. It may be seen that the elements 228 and 229 act as the conductors, shown diagrammatically at 210 in FIG. 5, which connect the assembly of armatures electrically in series, and that any two consecutive armatures carry currents in opposite directions and an overall axial magnetic field in the same direction. It follows therefrom that the Laplace force moments acting on each of them have opposite signs, as well as the direction of the rotation of consecutive rings of

blades

219a and 219b, as indicated above.

The radial and axial stresses of each rotating compressor stage are taken up by two different means. The radial stresses are absorbed by rotating contacts of liquid metal which fulfil the function of fluid centering bearings. In view of the provision of the compensation of axial stresses and in accordance with the electrodynamic process described in the above-mentioned patent application, the armatures 224 shown in FIG. 6 comprise, as indicated in FIGS. 7a and 7b, inclined slots 2240 which are uniformly distributed over their circumference in a region where the field B has a substantial radial component B The inclination of these s lots makes it possible to give to the current density vector J a tangential component .I to which the generated electrodynamic force is proportional. The direction of the inclination of the slots 2246 is that which corresponds to the compensation of the axially directed aerodynamic stresses, the direction of the current I flowing through the armature, and that of the magnetic field being considered to be the same, as shown in FIG. 6 (ring 219a).

For an observer located on the same side as the blading of the compressor shown in FIG. 6, the direction of the inclination of the slots 2240 is the same for the armatures of the blade rings 219a rotating in one direction, and 2191) rotating in the other direction.

FIGS. 4 and 6 do not show the means for obtaining the current necessary to feed the superconducting field windings of the homopolar motors. These means must supply at weak power a comparatively high intensity they may consist, as well as those which supply the field windings of the MI-ID generator, of a static electrical converter controlled by semiconductor elements of the type known as thyristors. By

separately controlling the intensity passing through each of the field windings, it is possible to adjust the rotational speed of each element (or stage, as the case may be) of the compressor, which makes it possible to produce for each an optimum efficiency under all running conditions, and particularly a very high compression rate. During take-off and at low flying speeds, the use of conventional fuels does not generally make it possible to obtain in the conversion channel 303 a sufficiently high temperature to enable the MHD generator to extract from the hot flow the necessary power to drive the compressor. In order to increase this temperature, it is possible to preheat the gas flow by heat transfer by means of heat exchanger means, such as a recuperator from the gas flow leaving the conversion channel towards the still cold gas flow. When the flying speed is sufficiently high this preheating is en-- sured by the dynamic compression of the air in the intake upstream of the compressor.

In the absence of such a heat exchanger means, the jet propulsion power plant according to the invention is comparable to a conventional ramjet in that its operation requires that a sufficiently high flying speed is reached. However, the fact that it has mechanical compression means gives it a fairly high thrust within a flying speed range which is much wider than that ofa ramjet, particularly in the lower region ofthis range.

FIGS. 8 and 9 show each the general layout ofa power plant the operation of which comprises two distinct sources of energy, namely the MHD generator and a supplementary source of energy, wherein each of them makes under all flying conditions, and more particularly during the take-off and at low flying speeds, a contribution the magnitude of which depends particularly on the flying speed. Preferably, the supplemental source of energy may comprise a gas turbine jet which is mounted, in the two embodiments, in series with the MHD generator.

The installation shown diagrammatically in FIG. 8 comprises, in the direction of flow, within a housing 300, a compressor of which only one element 301, is shown, a supplemental combustion or heating chamber 402, a turbine 401, a main combustion or heating chamber 302, and an MHD conversion channel 303 connected at 304 to ajet pipe, not shown.

The drive of the compressor is ensured by electric motors, such as 305, connected on one hand to

electrodes

309 and 309 of the MHD generator, and on the other hand to the terminals of an electric generator 405 rotated by the turbine and supplying the power necessary to provide the compression during the subsonic and transsonic phases of the flight.

The arrangement of the compressor is identical to that shown in FIG. 4 the rotor blades are driven by a drum provided with bearings 322 and forming part of the armature 305 of a homopolar motor, comprising staged discs similar to the

discs

123, 124, described above with reference to FIG. 4. 325 and 327 show respectively diagrammatically a superconducting field winding and rotating contacts of liquid metal.

Instead of a compressor comprising one or several elements of the type shown in FIG. 4, it is also possible to use, for example, a contrarotating compressor of the type shown in FIGS. 5 and 6, wherein the conductors 211 and 212 (FIG. 6) are connected to their equivalents 311 and 312 (FIG. 8) immediately downstream of the last stage of the compressor.

The supplemental combustion or heating chamber 402 is provided with additional heating means including fuel injectors 406. Its configuration is otherwise conventional and the air which takes part in the combustion only represents a small part of theair passing through the compressor. The fuel burnt in the chamber 402 is preferably of the same kind as the fuel supplied to the main combustion chamber 302.

The turbine 401 comprises a rotating stage with blades 419 and the usual fixed blade rings. The inlet guide ring 413 may have a variable pitch. The rotating ring 419 forms part of the armature 405 of a homopolar generator, the construction of which is very similar to that of the motor 305. This machine is provided with a superconducting field winding, shown diagrammatically at 425, and with rotating contacts of which only those are shown which form the actual electric terminals 427a and 427b of the machine, which machine supplies in series the motors such as 305. The number and/or diameter of the rotating discs (see FIG. 4) which form the armature of the homopolar generator are usually larger than those of the motors, so that the electromotive force at the terminals 427a and 427 b has a suitable value.

The main combustion chamber 302 and the MHD conversion channel 303 do not differ substantially from those shown diagrammatically in FIG. 1 if the geometry of the gas flow is disregarded, which is adapted in this case to the use of an MHD generator with rectangular cross-section in which the

electrodes

308 and 309 occupy two opposite surfaces. In the zone of these surfaces, a magnetic field is generated perpendicularly to the axis of the power plant, and parallel to the electrodes by field windings which are preferably superconducting.

The feed wires 311 and 312 of the compressor are connected to the

electrodes

308 and 309 of the MHD generator, and to the terminals 427a and 427b of the homopolar generator. The center wire 311 is integral with the housing 300. for example by means of radial arms such as 311a. It is in electrical contact with one terminal 427a of the armature 405 it is also connected to the electrode 308 through arms 311a and one or more conductors such as 311b. The tubular conductor 312 which is insulated against the conductor 311 by a layer or coating or alumina (not shown) is in contact with the second terminal 427b of the armature 405 it is also connected to the electrode 309 by means of a conical conductor 312a, a lead making use of, e.g., the fixed blade ring 413, and one or several conductors such as 31212. The two electric generators namely the MHD generator 303 and the homopolar machine 405 connected to the turbine are therefore mounted in parallel to the assembly of motors such as 305, which are themselves mounted in series.

Control of the respective contributions of each of these two generators to the total electric power transmitted to the motors driving the compressor may be effected by controlling the respective intensities of the inducing currents in the field coils of the homopolar machine 405, and of the MHD generator, respectively. he same may be achieved also by varying the pitch of the turbine blades.

An arrangement indicated generally at 432 has the object of controlling the delivery of fuel and its distribution amongst the

injectors

306 and 406 as a function of an operation parameter of the power plant, such as the flying conditions. The advantage of its use may be seen by considering how the power plant works.

At low flying speeds, the use of conventional fuels does not generally make it possible to obtain in the channel 303 a sufficiently high temperature for the MHD generator to extract the power necessary for driving the compressor. Therefore, the major part of this power is supplied by the turbine through the electrical generator 405 and the flow rate of fuel burnt in the chamber 402 is fairly high. The energy released by the combustion in the chamber 302 is utilized directly for the propulsion, although with a fairly low efficiency, the cause of which has been explained above.

The progressive increase in the flying speed and the subsequent appearance of a substantial dynamic compression in the air intake of the compressor give rise to an increase in the MHD conversion rate, owing to the rise in the temperature. This defines a phase of intermediary operation in which the temperature in the MHD channel is sufficiently high to permit the extraction of a certain fraction of the drive energy for the compressor. The increase in the total efficiency of the power plant is now fairly rapid. In fact, the extraction of energy from the conversion channel 303 makes it possible to reduce the gas expansion rate across the turbine, that is to say to raise the gas expansion rate between its admission into the main combustion chamber 302 and its discharge into the atmosphere.

At high flying speeds, the electric power extracted by MHD conversion supplies the major part or the whole of the drive energy for the compressor, and the turbine may, instead of extracting energy from the gas flow, supply additional energy and become an additional compression element. This effect may be controlled by controlling the intensities flowing through the field coils of the generating elements, as outlined above, and also possibly by adjusting the pitch of the blades of the turbine. Moreover, the device 432 for controlling and distributing the supply of fuel to the

injectors

306 and 406 may be controlled by a device adapted, for example, to maintain the temperature of the turbine blades at a value which is relatively independent from the flying speed, and which is near the tolerable maximum, which is favorable to the performance of the assembly.

It may be seen that the operation of the power unit described above comprises two very different functions, in accordance with whether the flying speed is low or high, but the transfer from one to the other in the course of the intermediate phase is extremely progressive.

The utilization of a rotating generator and an MHD generator, connected in parallel, implies, in principle, that the two generators have electromotive forces which are fairly near each other. However, it is possible, as shown in FIGS. 9 and 10, to overcome this limitation by using an independent working circuit for each of these two electric generators. Apart from that, the general arrangement of the power unit according to FIGS. 9 and 10 is similar to the power unit shown in FIG. 8. It should, however, be noted that it comprises an MHD channel of annular shape, of a configuration shown diagrammatically in FIGS. 2 and 3.

Referring now to FIG. 9, the three

elements

501a, 501b and 5010 of the compressor are rotatively driven by homopolar electric motors shown generally at 505 and described further below. The supplemental combustion chamber 602, the turbine 601, the main combustion chamber 502, and the MHD channel 503 act in a manner identical to that of the installa tion described with reference to FIG. 8. Each homopolar motor 505 comprises two armatures 505a and 505b which are electrically independent from each other. The armatures 505a are connected by conductors 510a and 51012, and this assembly is connected by

conductors

511 and 512, respectively, to

electrodes

508 and 509 of the MHD generator, wherein the conductor 512 passes through the flow of gas, for example, by means of the ring of fixed blades 613. The armatures 50512 are all connected in parallel to the terminals of the armature 605 of the homopolar generator, driven rotatively by the turbine 601, by the

conductors

611 and 612, the latter of which is connected to each armature 505b by conductors 612a, 61212 and 612C, which pass through the gas flow using radial arms or fixed vane rings, such as 513a, 51317 and 513c respectively.

The connection of the electric motors with independent armatures described hereinbefore illustrates obviously only one of a great many possibilities, of which one or the other may be preferable in any particular case. For example, it is possible to connect in series the armatures 505b to the homopolar generator 605 in the same manner in which the armatures 505a are connected to the MHD generator.

FIG. 10 shows some details of the embodiment shown in FIG. 9, referring particularly to the configuration of the armatures of the motors and of the generators 605, driven by the turbine, and to the arrangement of the feed conductors,

The arrangement of each of the three elements of the compressor is identical, only the last one 5010 being shown in the drawing. It is rotatively driven by a homopolar motor 505 with a field winding 525 and two separate armatures 505a and 505b which are both located in the magnetic field generated thereby. I

The armature 505a has exactly the same task as the armature of the motor 1050 in FIG. 1, one embodiment of which has been described hereinbefore with reference to FIG. 4, and may comprise the same arrangement.

The armature 505b whose counter-electromotive force may be much lower, has a similar construction to that of the armature 505a with the exception that it has a single rotating disc.

The inner edge and the outer edge of this disc are in electrical contact through rotating contacts with

annular conductors

611 and 612, respectively, which connect them respectively to rotating contacts 627a and 62% which define the annature 624 of the homopolar generator 605 driven in rotation by the ring 619 of rotating blades of the turbine 601 with which this armature is integral.

The armature 624 has a center section 624a in the shape of a cylinder and a peripheral section 624b in the shape of a disc. It is located between two superconducting field windings 625a and 6251; which carry currents in the same sense, and form in the zone 624b a substantially axially directedmagnetic field. Another superconducting field winding 6256 of smaller diameter carries current in the opposite direction to that flowing across the windings 625 a and 625b, and forms, in conjunction with the winding 625a, in the zOne 624a, a magnetic field whose lines extend substantially in the radial direction.

The blade ring 619 rests directly on rotating contacts of

liquid metal

627a and 627b, which take up radial stresses. The taking up of axial stresses is effected by a system of electrodynamic compensation similar to that used in the compressor described above with reference to FIG. 6. To this end, the cylindrical part 624a is formed with slots which are regularly spaced around its circumference, and the arrangement of which is shown in FIG. 11, which is a development of the armature 624. When the direction of the magnetic field formed by the windings 625a, 6251; and that of the intensity of the current flowing through the armature 624 correspond, respectively, to the arrows B and i, the direction of the slots must be as indicated in FIG. 11.

Referring to FIGS. 9 and 10, it may be seen that the transmission of electrical energy between the generators and the motors is effected, over the major part, by three or four coaxial conductors. The first two, 511 and 512, form the feed circuit of the armatures 505a by the MHD generator. The current path in this circuit is represented by arrows I. This circuit does not differ substantially from that shown in FIGS. 1 and 4 described above if one disregards the addition of connections 533 (FIG. 10) which comprise radial conducting elements ensuring the continuity of the circuit of the motors 505a, and axial conducting elements which pass through the preceding elements, electrically insulated against the same, and ensure the electrical continuity of the conductor 611 which supplies the armatures 505b. The two

other conductors

611 and 612 form the feed circuit of the armatures by the homopolar generator 605. The current flow in this circuit is indicated by the arrows i.

It is obvious that the embodiments hereinbefore described are merely examples and that it is possible to modify them in various ways without thereby departing from the principle of the invention a defined by the appended claims.

We claim:

1. A jet propulsion power plant comprising, in combination:

mechanical compressor means for compressing a flow of gas passing through said plant; electrical motor means for driving said compressor means; main and supplemental heating means for heating the compressed gas flow to a high temperature; an expansion gas turbine for expanding said gas flow, said gas turbine being located upstream of said main heating means but downstream of said supplemental heating means;

first electrical generator means comprising a magnetoplasmadynamic (MHD) generator adapted, at least under certain operating conditions of the power plant, to extract from the high-temperature gas flow at least a part of the energy necessary for driving the compressor means, said magnetoplasmadynamic (MI-ID) generator including a converter channel located downstream of said main heating means;

second electrical generator means comprising an electrical machine adapted to operate, at least under certain operating conditions of the power plant, as a generator,

said electrical machine having a rotor mechanically connected to the expansion gas turbine;

first electrical conductor means for electrically connecting said first generator means to said electrical motor means; and

second electrical conductor means for electrically connecting said second generator means to said electrical motor means.

2. A jet propulsion power plant according to claim 1 wherein said electrical motor means comprise at least one homopolar machine.

3. A jet propulsion power plant according to claim 1 wherein said second electrical generator means comprise at least one homopolar machine.

4. A jet propulsion power plant according to claim 1 wherein said electrical motor means comprise at least a first and a second electrical motor the rotors of which are rotatively joined to said mechanical compressor means, and wherein said first electrical conductor means connect said first generator means to said first electrical motor and said second electrical conductor means connect said second electrical generator means to said second electrical motor.

5. A jet propulsion power plant according to claim 4, comprising a common field winding means for said first and second electrical motors.

6. A jet propulsion power plant according to claim 1 wherein said expansion gas turbine includes at least one ring of variable pitch blades.

7. A jet propulsion power plant according to claim 1, includin g means for controlling said main and said supplemental heating means as a function of a parameter of the power plant.

8 A jet propulsion power plant according to claim 1 wherein said first and said second electrical generator means each include a field winding means, and means for controlling the respective intensities of current flowing through said field winding means, as a function of a parameter of the power plant.

9. A jet propulsion power plant according to claim 1, further comprising heat exchanger means for preheating the flow of gas by heat exchange with the gas flow which leaves the convertor channel of the magnetoplasmadynamic generator.

10. A jet propulsion power plant according to claim 1, wherein the converter channel of said magnetoplasmadynamic generator is bounded by two coaxial walls, and a field winding means forming part of said magnetoplasmadynamic generator comprises a plurality of conductors which extend substantially in the axial direction of said converter channel and are distributed generally in the form of two sheets respecframe in one of said sheets being connected to the corresponding axial end of a corresponding frame in the other sheet.

11. A jet propulsion power plant according to claim 1 wherein at least one of said electrical motor means and said second electrical generator means comprises at least one homopolar machine the armature of which includes at least one rotating element having a part in the shape of a disc, inclined slots being provided in said disc-shaped part so as to impart a tangential component 12. A jet propulsion power plant according to claim 1 wherein at least one of said mechanical compressor means and said expansion gas turbine comprises a plurality of bladed rotors carried respectively by individual axially spaced apart rotating rings, each of which rotating rings includes a part in the shape of a disc forming the armature of a homopolar machine, which homopolar machine has field winding means which include two windings mounted on either side of'said rotating ring and coaxially thereto.

13. A jet propulsion power plant according to claim 1 wherein at least one of said mechanical compressor means and said expansion gas turbine comprises a plurality of bladed rotors carried respectively by individual axially spaced apart rotating rings, each of which rotating rings includes, defined by two circular electrical terminals of different diameters and coaxial relative to said rotating rings, a part in the shape of a disc forming the armature of a homopolar machine; and wherein each of said rotating rings is separated from the following rotating ring by a field winding coaxial to the rotating rings and supported by a fixed element which is integral with a fixed ring coaxial with said rotating rings and connecting electrically through sliding contacts one circular terminal of one of the rotating rings with the corresponding circular terminal of the rotating ring located on the other side of said fixed element.

14. A jet propulsion power plant according to claim 1 wherein at least one of said mechanical compressor means and said expansion gas turbine comprises a rotor which is rotatively joined to the armature of a homopolar machine, which armature comprises a stack of rotating coaxial elements which are integral with each other and axially spaced apart, each of said elements having a part in the shape of a disc defined by two circular electrical terminals of different diameters and coaxial relative to the stack, said disc-shaped parts being electrically interconnected in series by intermediate fixed elements and sliding contacts, so that the smaller diameter terminal of one disc is connected to the larger diameter terminal of the next disc in the stack; and wherein said homopolar machine includes field winding means comprising a field coil mounted coaxially to the outer periphery of said stack and the axial length of which is substantially equal to the length of the stack.

IHIHAQ (nor Patent No. 7 ,306 Dated y 1972 Michel Robert GARNIER et al Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 12, Claim 11, line 9, after "component", insert to the density vector of the electrical current to said disc.

Signed and sealed this 17th day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM Po 1050 (10-69) USCOMNPDC wands & U.5. GOVERNMENT PRINTING OFFICE 1969 0-386334

Claims

1. A jet propulsion power plant comprising, in combination: mechanical compressor means for compressing a flow of gas passing through said plant; electrical motor means for driving said compressor means; main and supplemental heating means for heating the compressed gas flow to a high temperature; an expansion gas turbine for expanding said gas flow, said gas turbine being located upstream of said main heating means but downstream of said supplemental heating means; first electrical generator means comprising a magnetoplasmadynamic (MHD) generator adapted, at least under certain operating conditions of the power plant, to extract from the high-temperature gas flow at least a part of the energy necessary for driving the compressor means, said magnetoplasmadynamic (MHD) generator including a converter channel located downstream of said main heating means; second electrical generator means comprising an electrical machine adaptEd to operate, at least under certain operating conditions of the power plant, as a generator, said electrical machine having a rotor mechanically connected to the expansion gas turbine; first electrical conductor means for electrically connecting said first generator means to said electrical motor means; and second electrical conductor means for electrically connecting said second generator means to said electrical motor means.

7. A jet propulsion power plant according to claim 1, including means for controlling said main and said supplemental heating means as a function of a parameter of the power plant.

8. A jet propulsion power plant according to claim 1 wherein said first and said second electrical generator means each include a field winding means, and means for controlling the respective intensities of current flowing through said field winding means, as a function of a parameter of the power plant.

10. A jet propulsion power plant according to claim 1, wherein the converter channel of said magnetoplasmadynamic generator is bounded by two coaxial walls, and a field winding means forming part of said magnetoplasmadynamic generator comprises a plurality of conductors which extend substantially in the axial direction of said converter channel and are distributed generally in the form of two sheets respectively located near the outside of said walls, said conductors being connected with each other in pairs so as to form in each sheet a plurality of rectangular frames, each axial end of each frame in one of said sheets being connected to the corresponding axial end of a corresponding frame in the other sheet.

11. A jet propulsion power plant according to claim 1 wherein at least one of said electrical motor means and said second electrical generator means comprises at least one homopolar machine the armature of which includes at least one rotating element having a part in the shape of a disc, inclined slots being provided in said disc-shaped part so as to impart a tangential component

12. A jet propulsion power plant according to claim 1 wherein at least one of said mechanical compressor means and said expansion gas turbine comprises a plurality of bladed rotors carried respectively by individual axially spaced apart rotating rings, each of which rotating rings includes a part in the shape of a disc forming the armature of a homopolar machine, which homopolar machine has field winding means which include two windings mounted on either side of said rotating ring and coaxially thereto.