US3258925A

US3258925A - Closed-cycle thermal machine

Info

Publication number: US3258925A
Application number: US436208A
Authority: US
Inventors: Barthelemy Pierre Jo Ferdinand
Original assignee: SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 1964-03-04
Filing date: 1965-03-01
Publication date: 1966-07-05
Anticipated expiration: 1983-07-05
Also published as: FR1395738A

Description

July 5, 1966 P. J. F. BARTHELEMY 3,258,925

CLOSEDCYCLE THERMAL MACHINE Filed March 1, 1965 nfsm /A/ VEA/TOI? LSSI LowmmLQSoU @Ennuh United States Patent O M CLOSED-CYCLE THERMAL MACHINE Pierre Joseph Ferdinand Barthlemy, Villeneuve-le-Roi, France, assigner to Societe Nationale dEtude et de Construction de Moteurs dAviation, Paris, France, a

company of France Filed Mar. 1, 1965, Ser. No. 436,208 Claims priority, application France, Mar. 4, 1964, 966,067 18 Claims. (Cl. 60-59) The present invention has for its object a thermal machine including a turbine and a compressor operating with a compressible Huid moving in a closed circuit in accordance with the Joule or Brayton cycle. The term machine as employed herein is to beinterpreted as covering installations operating as, for example, generators, motors, refrigerating machines for liquefying gases and heat pumps.

The thermal machine provided by the invention uses, as its compressible working iluid, a heterogeneous fluid composed of a gaseous phase and a solid phase, the gas being preferably helium or some other inert gas such as :argon or neon and the solid phase advantageously being graphite or other non-abrasive solid particles, which are very finely divided and are infusible at the .operating temperatures.

In the thermal machine provided by the present invention, the composition of the gas-solid mixture varies in the course of the thermodynamic cycle. More precisely, the means for treating the mixture operate to keep separate from one another, over a substantial part of the cycle, on the one hand, the solid particles which circulate in the hot zone of the thermodynamic circuit (comprising the heat source and the turbine) and, on the other hand, the solid particles which circulate in the cold zone of the thermodynamic circuit (comprising the cold source and the compressor), only gas from which the solid particles have been removed to a considerable extent being allowed to pass from one zone to the other andl advantageously undergoing suitable heat exchange steps in the course of the transfer.

In one embodiment of the present invention, the means for treating the mixture comprise two particle separators disposed respectively in the hot zone and in the cold zone of the circuit, preferably at the outlet of the turbine and at the outlet of the compressor respectively, the separated particles being reintroduced into the gas owing through the said zones, preferably at a point of the circuit located upstream of the heat source and upstream of the cold source, respectively.

The invention will now be described more fully, by way of example only, with reference to the single figure of the accompanying drawing which is a diagram of an installation constructed according to the above-mentioned embodiment of the invention.

Referring to the drawing, the installation comprises a rotary machine-set constituted by a turbine 1, a compressor 2 and a driven apparatus 3, the assembly being mounted on a common shaft 4. In the installation shown in the drawing, the driven apparatus is an electric generator, but this example is in no way restrictive. Moreover, the illustrated arrangement with a single common shaft is not restrictive, since the various elements of therotary group could be associated with different shafts, through the medium of suitable transmissions.

yThe installation illustrated in the drawing has been divided by means of vertical chain-dotted lines X-X and Y-Y into three zones A, B, C which will 'be referred to respectively hereinafter as the hot zone, the transfer zone and the cold zone. The turbine 1 is located in the hot zone A and the compressor 2 in the cold zone C, while arotaryregenerator or other 'heat exchanger 5 is dis- 3,258,925 Patented July 5, 1966 ICC posed in the transfer zone B. A heat source 6 is also provided in the hot zone A and a cold source 7 in the cold zone C, these two sources being connected to the inlets of the turbine 1 and of the compressor 2, respectively.

The compressible fluid employed in the install-ation is an essentially heterogeneous fluid, in the sense that it is composed of a gaseous phase and a solid phase, for example helium charged with tine particles of graphite.

The installation also includes ya first particle separator 8 in the hot zone A, at the outlet of the turbine 1, and a second particle separator 9 in the cold zone C, at the outlet of the compressor 2. From the first separator 8 there extends a conduit 10 for gas from which the particles may be regarded, for practical purposes, as having been completely removed, and which passes through the rotary regenerator 5 provided in the transfer zone B and enters the cold zone C to reach the inlet of the cold source 7. Conversely and in an analogous fashion, from the second separator 9 there extends a conduit 11 for gas from which the particles have also, practically speaking, been removed and which passes through the rotating regenerator 5 in the opposite direction and enters the hot zone A to reach the inlet of the heat source 6. The solid particles collected in the separator 8 are reinjected at 12, upstream of the heat source 6, under the action of the blast effect exerted by the flow through the conduit 11, of gas devoid of particles coming from the separator 9, which has passed through the rotary regenerator 5. Likewise, the solid particles collected in the separator 9 are re-injected lat 13, upstream of the cold source 7, by the blast effect exerted by the ow through the conduit 10, of gas devoid of particles coming from the separator 8, which has passed through the rotary regenerator 5.

Within the limits of the installation described, the solid particles have a multiple function:

(l) They considerably improve the heat exchange relationship between the sources 6 and 7 and the gas and at the same time they greatly increase the caloric capacity of the latter. In fact, the solid particles, particularly when these are of graphite, increase the exchange of heat by conduction and radiation by rendering the gas opaque and, moreover, they offer a large caloric capacity in a very small volume.

(2) These particles enable the adiabatic expansion in the turbine 1 to be effected without considera-ble reduction of the temperature of the gas, that is to say, they enable the adiabatic expansion to approach the lideal isothermal expansion; the reverser process takes place in the compressor 2, in which the adiabatic compression approaches the ideal isothermal compression. In fact, the very fine solid particles which, in the case of graphite, are of lamellar structure, constitute innumerable elementary reservoirs of thermal energy which are capable of giving up rapidly to the gas which is expanded, the heat that it needs, and also of rapidly withdrawing the heat from the gas which is compressed, so that the processes may be substantially isothermal.

Moreover, by reason of their essentially different physical nature from that of the gas in which they are in suspension, the solid particles can be withdrawn therefrom easily, to be subsequently incorporated therein afresh, these two successive operations being effected, respectively, in the separators 8 and 9 and in the

blast devices

12 and 13.

Owing to the fact that the particles are at the same temperature as the dluid, after this has been expanded in the turbine 1 (or even at a higher temperature) and that they carry in themselves -the greater part of the internal heat recoverable from the mixture (by reason of their calorific capacity, which is much higher than .that of the gas), their re-injection into the cold compressed gas which is devoid of particles at the inlet of the heat source 6, at 12, produces `regeneration of heat with an eflciency practically equal to unity. A similar observation, but obviously in converse terms, applies to the particles in the zone C, which are separated from ythe fluid after compression in the compressor 2 and Iare re-injected into the hot Igas `which is devoid of particles at the inlet of the cold source 7, at 13. The gas therefore receives cold solid particles which are totally different 'from the hot particles in the zone A and which come Ifrom the second separator 9, the effect of which, as has lbeen seen, is to improve considerably the `transfer of heat from `the fluid to the cold source 7 and to cause the adiabatic compression, in Athe compressor 2, to 'tend towards the ideal isotherm-al compression, since the solid particles constitute sources of heat of large capacity. Likewise the separator 9 ensures regeneration of the coolness carried by the mixture with an efllciency practically equal to unity.

This effective regeneration of the greatest amount of internal heat of the fluid lby simple separation of the solid and gaseous phases ymakes `it possible, if need be, `to dispense .with the rotating regenerator or with any other heat exchanger.

In brief, it -may be said that one of the ymost important characteristics of the invention results from the symmeltry of the hot and cold zones of the circuit and from the fact that the solid particles in each zone are retained within that zone, with separa-tion occurring after the oper-ation of expansion or compression, as the case may be, has been performed and with re-introduction occurring before the fliud undergoes ythe taking-up or the loss of heat, as the case may be.

In comparison with conventional installations comprising turbo-compressors operating in a closed circuit in accordance with the Joule cycle, with an external source of heat, the installation according to the present yinvention has the following advantages:

External irreversibility effects are reduced, both at the sidewhere the heat source is located and at the side where the cold source is located, in consequence of the substantial increase in the coefllcient of efficiency of the heat exchange, which increase is obtained by the addition of the conductive solid particles to the working fluid;

The thermodynamic yield of the cycle is increased by reason of .the operation of the turbine 1 and the cornpressor 2, which operations approximate to ideal isothermal expansion and compression, and also by reason of the process of regeneration by separa-tion of the phases, that is to say, without the Itransfer of heat by conduction from one yfluid to another, which process is associated, if required, with the conventional process of regeneration by transfer of heat by conduction, which is applied to the gaseous phase alone, `thus enabling a total efliciency close to unity to be attained.

The field of application of the invention is obviously very extensive `and, by way of indication, a number of applications Iwhich see-m to be the more important will be mentioned.

(l) Nuclear power stations:

The heterogeneous working `fluid referred to above, which is advantageously composed of helium charged with particles of graphite, can circulate directly in the nuclear reactor without resorting to intermediate heat exchange Imedia. The nature of the constituents of the heterogeneous fluid is such that there is no fear of ythe fluid being found to be radio-active on leaving the reactor. The reactor tanks will not have to be designed to withstand the high pressure levels which are encountered in pressurized-water reactors.

(2) Power generators, -in particular for space applications:

The installation described makes it possible to dispense with intermediate heat exchange media and to utilize a working fluid which is both lighter and capable of operating at lower pressure levels, the temperature at the outlet from .the reactor and at the inlet to the radiator (which would be at 6 and 7, respectively) being higher. The result is saving in weight, simplification of the -technological problems, improved efficiency and a higher power per unit mass of the installation.

(3) Machines for liquefying gases:

In this case the gas to be liquefied will constitute the heat source 6, the working fluid lbeing one having a very low point of liquefaction, such as helium.

(4) Propulsion plants, Iin particular for nuclear propulsion submarines:

The heat source 6 rnay be a conventional combustion furnace or a nuclear pile, the driven device 3 being a driving wheel or a propeller, according to the nature of the vehicle to be propelled.

What is claimed is:

l. A method of driving a turbine, using a compressible heterogeneous fluid comprising a gaseous phase and a solid phase consisting of particles in suspension in said gaseous phase, said method comprising causing said fluid to flow in a circuit comprising relatively cold and relatively hot zones and an intermediate Zone and, in a continuous cycle, cooling and compressing said fluid in said cold zone, heating said fluid and feeding it to said turbine in said hot zone, to drive said turbine, and changing the relative proportions of said gaseous and solid phases in said fluid during flow in said circuit, whereby the density of said particles flowing in said intermediate zone, between said relatively lhot and relatively cold zones, is lower than the density of said particles in fluid flowing within said respective hot and cold zones.

2. A method of driving a turbine, using a compressible heterogeneous fluid comprising a gaseous phase and a solid phase consisting of particles in suspension in said gaseous phase, said method comprising causing said fluid to flow in a circuit comprising relatively cold and relatively hot zones and an intermediate zone and, in a continuous cycle, cooling and compressing said fluid in said cold zone, heating said fluid and feeding it to said turbine in said hot zone, to drive said turbine, separating particles from said fluid flowing in said cold zone before said fluid flows from said cold zone to said hot zone and from said fluid flowing in said hot zone before said fluid flows from said hot zone to said cold zone and injecting particles into fluid flowing from said intermediate zone to said respective hot and cold zones.

3. A method according to claim 2, wherein substantially all said particles are separated from said gaseous phase before said fluid flows from said hot zone to said cold zone and vice versa.

4. A thermal machine including a turbine adapted to be driven by a compressible heterogeneous fluid comprising a gaseous phase and a solid phase consisting of particles in suspension in said gaseous phase, said machine including a circuit for flow of fluid, a compressor, a source of heat and a cold source, said circuit including a relatively hot zone in which fluid flowing in said circuit is fed to said heat source and to said turbine and a relatively cold Zone in which fluid flowing in said circuit is fed to said cold source and to said compressor and said machine further including means for changing the relative proportions of said gaseous and solid phases in said fluid during flow in said circuit, whereby the density of said particles in fluid flowing in said circuit intermediate between said relatively hot and relatively cold zonel is lower than the density of particles in fluid flowing within said respective hot and cold zones.

5. A thermal machine including a turbine adapted to be driven by a compressible heterogeneous fluid comprising a gaseous phase and a solid phase consisting of particles in suspension in said gaseous phase, said machine including a circuit for flow of fluid, a compressor, a source of heat and a cold source, said circuit including a relatively hot zone in which uid flowing in said circuit is fed to said heat source and to said turbine, a relatively cold zone in which fluid owing in said circuit is fed to said cold source and to said compressor and an intermediate zone in which uid ilows from said hot zone to said cold zone and vice versa, said hot and cold zones each including means for separating particles from lluid flowing from said respective hot and cold zones into said intermediate zone and means for injecting particles into fluid flowing Ifrom said intermediate zone to said respective cold and hot zones.V

6. A machine according to claim 5, including means for feeding particles from said particle separating means to said particle injection means in each of said hot and cold zones, for re-injection into said fluid.

7. A machine according to claim 5, wherein said heat source has an inlet for supply of liuid thereto from said intermediate zone and an outlet for flow of heated fluid therefrom to said turbine, wherein said cold source has an inlet for supply of fluid thereto from said intermediate zone and an outlet for flow of cooled fluid therefrom to said compressor, and wherein said particle injection means are arranged to feed particles into said fluid at said inlets to said heat source and said cold source.

8. A machine according to claim 5, wherein said separating means are effective to separate substantially all of said particles from fluid flowing from said respective hot and cold zones into said intermediate zone, whereby uid flowing in said intermediate zone consists substantially wholly of said gaseous phase.

9. A machine according to claim 5, wherein said intermediate zone includes a heat exchanger for exchange of heat between fluid flowing from said hot zone to said cold zone and from said cold zone to said hot zone.

10. A machine according to claim 5, wherein said intermediate zone includes a rotary regenerator for exchange of heat between fluid flowing from said hot zone to said cold zone and from said cold zone to said hot zone.

11. A thermal machine including a turbine adapted to be driven by a compressible heterogeneous uid comprising a gaseous phase and a solid phase consisting of particles in suspension in said gaseous phase, said machine including a circuit for ow of fluid, a compressor, a source of heat and a cold source, said circuit including a relatively hot zone in which fluid flowing in said circuit is fed to said heat source and to said turbine, a relatively cold zone in which fluid flowing in said circuit is fed to said cold source land to said compressor and an intermediate zone in which uid ows from said hot zone to said cold zone and vice versa, said hot and cold zones each including means for separating particles from iiuid flowing from said respective hot and cold zones into said intermediate zone, two Venturi tubes arranged for the passage therethrough of fluid flowing from said intermediate zone to said respective hot and cold zones and means for feeding particles from each of said particle separating means to an associated one of said venturi tubes, whereby said particles are re-injected into said uid by blast effect in said respective venturi tubes.

12. A thermal machine including Ia turbine and a circuit having therein a compressible heterogeneous iiuid :to drive said turbine, said liu-id comprising, as a gaseous phase, an inert Igas and, las .la solid phase, non-abrasive iirrely divided solid particles which are infusible at the temperature at which said machine is adapted to operate, said machine including a circuit for ilofw of fluid, a compressor, .a source of heat an-d =a cold source, said circuit including a Vrelatively hot zone in which duid ilowing in said circuit is fed to said heat source and to said turbine ,and a relatively cold zone in which fluid flowing in said circuit is fed to said cold source and `to said compressor land said machine fumther including means for changing the relative proportions of :said gaseous and solid phases in said iiuid during flow in said circuit, whereby the den-sity of -said particles in fluid flowing in said circuit intermediate between said relatively hot and relatively cold zones is lower lthau Ithe density of said particles in duid owing within said Irespect-ive hot and cold zones.

13. A machine according .to claim 12, wherein said inert gas is selected from the group comprising the rare gases.

14. A machine .according to claim 12, wherein said inert gas is helium.

15. A machine according to claim 12, wherein said particles ,are particles of lgraphite.

16. An installation comprising a turbine, adapted to be driven by a compressible heterogeneous fluid comprising a gaseous phase ,and .a solid phase consisting of particles in .suspension in said gaseous phase, ,a driven machine .operatively coupled .to said turbine .to be driven by the latter, fa circuit for flow yof iuid, a compressor, 'a source of heat and a cold source, said circuit including la relatively hot zone in which fluid flowing in said circuit .is fed to said heat source and to said turbine and .a relatively cold zone in which fluid flowing in said circuit is fed to said cold source and `to said compressor and said machine further including means for changing .the relative proportions of said gaseous and solid phases in said uid during ow in said circuit, whereby the density lof said particles in fluid flowing in said ci-rcuit intermediate between said relatively hot and relatively cold zones is lower than the density of particles in iiuid cwin-g Iwithin said respect-ive hot and cold zones.

17. An installation according to claim 16, wherein said turbine and said compressor :are mounted on a common shaft which serves fto drive said driven machine.

1'8. An installati-on according Ito claim- 16, wherein said driven machine `is an electric generator.

References Cited by the Examiner UNITED STATES PATENTS 2,882,687 4/ 1959 Stivender 60--59 FOREIGN PATENTS `636,859 5/ 1950 Great Bri-tain.

i EDGAR w. GEOGHEGAN, Primary Examiner.

Claims

1. A METHOD OF DRIVING A TURBINE, USING A COMPRESSIBLE HETEROGENEOUS FLUID COMPRISING A GASEOUS PHASE AND A SOLID PHASE CONSISTING OF PARTICLES IN SUSPENSION IN SAID GASEOUS PHASE, SAID METHOD COMPRISING CAUSING SAID FLUID TO FLOW IN A CIRCUIT COMPRISING RELATIVELY COLD AND RELATIVELY HOT ZONES AND INTERMEDIATE ZONE AND, IN A CONTINUOUS CYCLE, COOLING AND COMPRESSING SAID FLUID IN SAID COLD ZONE, HEATING SAID FLUID AND FEEDING IT TO SAID TURBINE IN SAID HOT ZONE, TO DRIVE SAID TURBINE, AND CHANGING THE RELATIVE PRPORTIONS OF SAID GASEOUS AND SOLID PHASES IN SAID FLUID DURING FLOW IN SAID CIRCUIT, WHEREBY THE DENSITY OF SAID PARTICLES FLOWING IN SAID INTERMEDIATE ZONE, BETWEEN SAID RELATIVELY HOT AND RELATIVELY COLD ZONES, IS LOWER THAN RESPECTIVE HOT AND COLD ZONES.