US2078957A - Gas turbine apparatus - Google Patents

Description

lMaly-4, 1937. 7 A LYSHOLM 2,078,957

GAS TURBINE APPARATUS Filed July 22, 1933 W [lez /10 d ATTORNEY iatented May 4, 1937 UNITED sTATEs GAS TURBINE APPARATUS Alf Lysholm, Stockholm, Sweden, assignmto Aktiebolaget Milo, Stockholm, Sweden, a col'- poration of Sweden Application July 22, 1933, Serial No. 881,697 In Germany March 24, 1830 6 Claims.

'I'his application is a continuation in part replacing my application Serial No. 523,505 tiled March 18. 1931, and relates back to said application Serial No. 523,505, so far as herein con- 5 tinued for all dates and rights incident to the filing thereof and to the illing in foreign countries of applications corresponding thereto.

This invention relates to gas turbine apparatus of the type comprising a plurality of gas turbines adapted to be operated by a compressed gaseous motive uid supplied to the turbines at high temperature. Still more particularly the invention relates to such apparatus in which thev motive uid is formed by continuous combustion of fuel .l with air compressed in compressor apparatus driven by one or more of the turbines.

A general object of the invention is to improve upon prior forms of apparatus of the above general kind by the provision of apparatus in which ,0 heating and reheating of the gaseous motive iluld is effected in combustion chamber apparatus separated from the turbines and in which the hot motive uid comprising combustion gases is conducted to and expanded in each turbine in a 5 manner permitting the potential energy of the motive fluid to be utilized with high efiiciency in each of the turbines of the apparatus.

The manner in which the above general and further and more detailed objects of the invention :m are attained in accordance with the present invention may best be understood from the ensuing description taken in conjunction with the laccompanying drawing forming a part of this speciilcation, in which:

5 Fig. 1 is a more or less diagrammatic View partly in section of gas turbine apparatus embodying the invention;

Fig. 2 is a more or less diagrammatic view partly on enlarged scale, of a diiierent form of 1.0 part of the apparatus shown in Fig. 1; and

Fig. 3 is a more or less diagrammatic view of another form of gas turbine apparatus embodying the invention.

In order for gas turbine apparatus of the char- 5 acter under discussion to be suiiiciently eiiicient to be commercially practical, the initial temperature of the gaseous motive fluid must be above a certain temperature in order to secure a suiiiciently high temperature drop in the turbine sysw tem and, While this has heretofore been recognized and the fact that reheating between turbineshas also been heretofore recognized, the arrangements previously proposed have not provided practical means for the production and 5 utilization of high temperature gaseous motive fluids, as wiiluhereinafter more fully appear.

In accordance with the present invention, I provide apparatus whereby a sufiiciently high initial temperature of motive fluid may be ob- 50 tained and such motive uid may be efficiently utilized while at the same time avoiding the necessity, in order to secure the desired over-al1 turbine efficiency, of having to resort to an initial temperature or motive fluid so high that it is impractical to use the motive iiuid eiiiciently at its initial temperature. This I accomplish by the combination, with separate turbines having certain characteristics to be hereinafterv more fully explained, of separate heating and reheating devices for the motive fluid, the whole apparatus being arranged so that accurate and reliable control of the temperatures of the motive fluid at the place of admission to the different turbines may be obtained.

Turning now to the embodiment of the invention shown by way of illustration in Fig. 1, the apparatus comprises a first turbine designated generally at A and a second turbine designated generally at B. Turbine A is of the double rotation radial flow type and comprises an outer casing I0 in which are rotatably mounted the shafts I2 and I4. Shafts I2 and I4 are adapted to rotate in opposite directions and at their adjacent inner ends have overhung thereon the turbine rotors I6 and I8 respectively. Each of rotors i6 and I8 carries a plurality of rings of turbine blades 20, the rings of the blades on the two rotors being interleaved and together forming a blade system for radial flow of motive iluid from the central admission chamber 22 to the exhaust casing 24. The details of design of the blade system are not germane to the present invention but in accordance with the invention the blading is of the reaction type as distinguished from impulse blading and full admission of motive uid to the blade system is employed.

In the embodiment illustrated, shafts l2 and I4 have mounted thereon the rotor parts of electric generators indicated generally at 26 and 28.

Turbine B is similar in form to turbine A and comprises an outer casing 38 in which are rotatably mounted the oppositely rotating shafts 32 and 34 having rotors 36 and 38 overhung on the inner ends of the shafts. Rotors 36 and 38 carry a plurality of interleaved rings of turbine blades 40 forming a second radial ow blade system for flow of motive iluid from the central admission chamber 42 to the exhaust casing 44.

Shaft 34 has mounted thereon the rotor 46 of a low pressure compressor which in the embodiment illustrated comprises a plurality of axially side by side stages for centrifugal compression of air admitted to the compressor through the inlet 48. Shaft 32 carries the rotor 50 of a high pressure compressor, the form of which is in general similar to that of the low pressure compressor. Air discharged from the low pressure compressor passes through the space 52 between the outer turbine casing 38 and the exhaust casing 44 to the inlet end of the high pressure com- 'by conduit 84 to the inlet fend ol a heating device indicated'generally at C." In the embodiment .l shown, the heating device C comprises an outer easing I8 and an inner casing I8, the casing forminsacombusnonthamber n to .which fuel isradmittejd through the'nozzle 82. Air is' ad-r mitted. rmieonduit u both to the combustion chamberllandto theiacketed space 84 between the outer casing I8 and the inner casing 88. Coml bustion chamber 88 is connected to the central admission chamber 22 of ,turbine A by means of pipes 88 and 8l which are surrounded respectively by outer` pipes 18 and'12. The spaces between inner pipes 48 and 88 and outer pipes 18 and 12 `are in communication with the jacketed space 84 around the combustion chamber 88 so that motive iluid is delivered to the central admission chamber of the turbine in the form of streams o! high temperature gas surrounded by annular envelopes of a cooler gaseous medium. All oi' the gaseous medium conducted through the several pipes 88, 88, 10 and 12 is delivered to the in let of the blade system and at this point the cooler and hotter mediums are mixed. The air supply to the combustion chamber 68 is preferably unthrottled and control o1' the temperature of the motive iiuid delivered to the turbine is preferably effected whollyby regulation of the amount oi' i'uel supplied. In order to secure the beneilts of the invention, the motive fluid is supplied to turbine A for initial expansion from a temperature within a range oi' which the lower limit is pproidmately 800 C. absolute and the l upper limit is such as will permit the continuous absolute.

full admission of the motive iluid to the turbine blading without the destruction of the moving blades due to excessive temperature of motive fluid.' Ordinarily, I prefer to supply motive fluid within a temperature range of which the lower limit is approximately 800 C. absolute and the upper limit It will be noted from the figures of the drawing that pipes 88, v68, 10, 12 provide conduits of substantial length connecting the combustion chamber Sii with the admission chamber 22 of the turbine. The reasons for providing this construction will be explained later.

Fuel is supplied to nozzle 82 through the pipe 14 and the amount of fuel passing through-pipe 14 is advantageously controlled by means of a suitable valve 16 controlled by governor 18 driven from the shaft i4. Fuel may be conveniently supplied to pipes 14 by pump 88 driven from the generator shaft I4 and drawing fuel through pipe 82 `from the fuel supply reservoir indicated at 84.

Excess fuel is returned through pipe 88 to the fuel reservoir.

Motive iluid, expanded in the blade system formed by the blades 20 to a temperature and l pressure lower than the initial temperature and pressure, is conducted through the exhaust pipe 88 to a reheating device indicated generally at D. 'Ihe reheating device D comprises an outer cas- K ing 98 and an inner casing 92. A reheating combustion chamber 94 is formed within the inner casing 92 and annular space 96 is formed between the casings 9|!A and 92. Both chamber 94 and space 96 are in communication with the outlet of the exhaust pipe 88. Combustion chamber 94 is connected by means of inner pipes 98 and |98 with the admission chamber 42 of turbine B, and

pipes 98 and |00 are surrounded respectively by of which is approximately 1000 C.

buter pipes m and m, the latter being in wmmunication with space` 94. 'Ihese pipes provide conduits of substantial length connecting the I v vide the heated and compressed motive i'iuid for the turbines. The quantity of fuel supplied to combustion chamber 89 is regulated so that the desired temperature oi' the motive fluid is obtained with a fluid which contains a considerable amount of excess air. shown, wherein some of the air is conducted to the turbine separately from the products of combustion, this separately conducted air may comprise all or the major portion oi' the excess air. The initially heated and compressed motive fluid is expanded by passage through the blade system comprising blades 28 and is discharged to the exhaust pipe 88 at reduced pressure and temperature. Some of this motive uid at relatively low temperature is delivered to the com- I |88. This fuel is burned with the excess air contained in the motive fluid as exhausted through pipe 88 and is regulated so that the motive fluid is reheated to a temperature preferably substan tlally the same as that of the initial temperature. 'I'he reheated motive fluid, at a pressure lower than the initial pressure but at substantially the same temperature as the initial temperature, is then expanded by passage through the blade system comprising blades 48 and the energy of the reheated motive fluid employed to drive the compressors which supply the compressed vair to the initial heating device C.

'Ihe arrangement shown by way of illustrative example is that for a stationary gas turbine plant designed primarily for substantially constant load operation and shows to scale the relative sizes of the several parts oi' the plant in a plant of from 7000 to 10.000 kw. capacity. It is to be noted that both the heating device C and the reheating device D are made separate from the turbines and that the motive tluid discharged from these devices is conducted to the respective In the embodiment turbines through pipes oi' substantial length. By

making the heating and reheating devices separate from the turbines and connecting them to the turbines in the manner indicated, I am'enabled to effect a control of the temperature of the motive iluid to a degree which is not possible in constructions in which it is attempted to heat or reheat motive iiuid in combustion chambers directly associated with the turbine structure. This relatively '.lose control of temperature which I obtain should be employed if operation or apparatus of the character describedwith the desired emciency is to be obtained, since such operation involves the use oi" an initial temperature substantially as high as can be successfully employed in the type of turbine used. As herenected thereto by conduits of' substantial length.

An important reason for this construction is to insuredelivery to the admission chambers of the turbines of motive fluid having substantially homogeneous temperature characteristics. Even the minimum temperatures required at the place or places of initial expansion in the turbine or turbines of a system of this kind Where heating and reheating is employed, is such that any possibility of localized strata of gases at a much higher temperature than the designed temperature must be prevented from reaching the turbine blading if the life of the latter is to be maintained for a reasonably satisfactory length of time. Consequently, by the term substantial length as herein used, I intend to define connections, the length and character of which are such in any given installation as to provide high temperature motive fluid having substantially homogeneous temperature characteristics as admitted to the turbines.

While I prefer to employ, and have shown, jacketed combustion chambers and double pipe means for conducting motive fluid to the turbines in separated streams comprising inner streams of relatively high temperature fluid surrounded by' streams of fluid of lower temperature, this arrangement is not essential to the practice of the present invention and constitutes the subject matter of my copending application Serial No. 619,093 filed June 24, 1932.

Within the scope of the present invention the heating and reheating chambers may be connected to the inlets of the respective turbines by single pipes which conduct all of the motive fluid supplied to the turbines.

Inorder to secure high over-all thermal eiiiciency of the apparatus, it is necessary to have a relatively high over-all temperature drop of the motive fluid. In previous forms of apparatus this high temperature drop has been attempted to be secured by employing an excessively high initial temperature, but arrangements for carrying this method of heat utilization into effect have proved to be impractical because of the inability of turbine materials to sustain the stresses 4imposed thereon at the temperatures resulting from the employment of excessively high initial temperatures of motive fluid. By the arrangement according to the present invention I am'enabled to obtain high efciency with-I out employing an initial temperature of the motive fluid which exceeds that which known turbine blading can sustain without resort to water cooling or the like and this is primarily due to two principal factors in my construction.

The first of these factors is the arrangement of the apparatus so that practicable reheating of the motive fluid to substantially its initial temperature may be obtained, thus making it possible to obtain a high over-all heat drop with a maximum temperature of the motive fluid which is Within practicable limits.

The second of the factors is the utilization of the motive fluid in turbine blading of the reaction type with full admission of the motive fluid to blading in each turbine which is so constructed that the motive fluid, considered in the direction of ow through the turbine, has a component of flow in radially outward direction of substantial value. With such construction of the blading, the first `row or rows of blades inl jected to relatively small mechanical stresses. The radial flow type of turbine is an excellent example of the turbine in which 4full admission to initial blade rows of Arelatively small `diameter may be effected and I have chosen this type of turbine for illustration in the present application. The invention, however, is not necessarily limited in its application to radial flow turbines but may also be employed in conjunction with axial flow turbines having the characteristics 'of full` admission of motive fluid to initial blade rows of substantially smaller mean diameter than that of the rows at the exhaust end of the blade system, and, as herein employed, the term central admission is to be considered as applicable both to radial 110W turbines and axial flow turbines in which admission of motive fluid is to initial blade rows of small diameter as compared with subsequent blade rows. A suitable form of axial flow turbine for use with high temperature gaseous motive fluid is disclosed and claimed in my German application Serial No. 46 f. A. 51/30 led March 24, 1930.

By employing the motive fluid with full central admission in each of the turbines, the high efficiency of reaction blading can be taken advantage of. Also, full admission of motive fluid at an initial temperature which is relatively high as compared with the temperature possible with the usual form of axial flow turbine where the I fluid is'admitted to a turbine stage of comparatively large diameter, may be safely employed because of the relatively small mechanical stresses imposed on the blades which must sustain the high initial temperatures.

The present invention is not restricted in its scope of application to gas turbine apparatus of the type shown in Fig. l, in which fuel in the initial heating device is burned in lan excess of air so as to provide oxygen for further combustion in the gases exhausted from the rst turbine. It is equally well applicable to systems wherein reheating is accomplished by adding to the exhaust gases from one turbine additional air for combustion as well as fuel.

In Fig. 2 I have shown more or less diagrammatically an arrangement for reheating which contemplates the addition of air as well as fuel to the combustion gases in the reheating combustion chamber.

In the arrangement illustrated, the reheating device comprises an outer shell 9B and an inner shell 92 and the space 96 between these shells is placed in communication with a supply of fresh air at suitable pressure by means of pipe Illl. In the present instance pipe H0 is placed in communication with the discharge side of the low pressure compressor from which compressor air is delivered at a pressure slightly above the pressure to which the motive fluid is'exhausted from the turbine A. Obviously, the necessary supply of air can be obtained from a zone of higher pressure such, for example, as the conduit 54, in which case it is suitably throttled to the desired pressure approximately corresponding to the pressure of the motive fluid as exhausted from turbine A. Generally speaking, however, arrangements nvolving throttling of the air, with its accompanying losses, should be avoided.V

The inner shell 92 carries, by means of suitable Webs or the like H2, a tube H4 preferably of Venturi form through which the nozzle |06 discharges fuel. Around tube I I4 there is provided the annular channel H6 which is in com- Gir Cil

is supplied by means o! webs ||2, which may,l

as shown. be hollow.

It will be evident that arrangements diflering in details of construction from that more or less diagrammatically illustrated may be employed,

and it will also be evident that, if desired, the

space 88 can be utilized to conduct gases exhausted from the turbine in the manner of the apparatus shown in Fig. 1. In this case air from the pipe would be conveyed only to the 'part of the apparatus supplying air to support combustion oi' fuel introduced through nozzie |88.

With apparatus of the kind just described, the quantity4 oi fuel admitted to the heating device C is regulated so as to provide comparatively little, if any, excess air in the combustion gases. When regulation is accomplished so as to pro vide comparatively little excess air, the temperature of the combustion gases produced will be comparatively high and under such conditions it may be desirable to inject water into thel combustion chamber for the purpose of reducing the temperature level of the motive iiuid as delivered to the turbines. Such injection of water is known per se and need not be described herein for purposes of understanding of the present invention.

In case, however, water injection is employed, the volume of the combustion chambers and piping will be considerably greater than in the type of apparatus indicated in Fig. 1, since with water injection the water is converted into steam and the volume of motive iluid obtained through the combustion of given amounts of air and fuel will be greater than when water injection is not resorted to.

In Fig. 3 I have illustrated more or less diagrammatically another form of part ofthe apparatus of a gas turbine plant. In the apparatus illustrated the generator |22 is housed in a casing |24 which supports the bearings for the rotor shaft |28. Shaft |28, or parts rigidly secured thereto, project past the bearings |28 and |80 and pass through suitable stumng boxes or packings |32 and |84. The projecting ends of the shaft extend respectively into turbine casings |88 and |88. The portion of the shaft extending into casing |88 is provided with a disclike rotor |40 carrying a plurality of rings of turbine blades |42 which cooperate with a plurality of interleaved rings of stationary turbine blades |44 carried by the stationary portion of casing |38 to form a radial now blade system of the single rotation type through which motive fluid iiows from the central admission chamber |48 to the exhaust space |48.

Similarly, the end of the shaft |28 projecting into the casing |88 carries a rotor disc |50 having ringsv of turbine blades |52 cooperating with rings of stationary turbine blades |54 to form a radial dow blade system of the single rotation type for flow of motive uid from the central admission chamber |58 to the exhaust space |58. The rotor |84 oi' this turbine also carries a row of radially extending turbine blades |80 through which the motive fluid discharged into space |58 and guided by the stationary guide |82 ilows in axial direction to the exhaust passage |84 of the turbine.

Air for combustion purposes is supplied through conduit |86 from any suitable source to the heat- 'ing device E which provides a combustion chamtral admission chamber |58 of the second turbine. 1 The mode of operation of this turbine will be readily understood from a description of the apparatus shown in Fig. 1. The present embodiment illustrates the psibility of utilizing types of turbines other than those shown in Fig. 1 and further illustrates the use of single conduit means for conveying the products of combustion .forming the motive fluid from the combustion chamber to the turbines. It will be observed that in this apparatus as well as that shown in Fig. 1 the admission of motive fluid to the turbines is central and full admission is employed. While the axial flow blades |80 are, in the apparatus shown, at a relatively great radius, and not suitable for initial admission of motive fluid, they may be employed in the manner indicated since the motive iluid entering these blades from space |58 is at relatively low temperature due to expansion through the blade system provided by blades |52 and |54.

' While for purposes of clarity I have illustrated the present invention as applied to gas turbine plants of substantially the most simple arrangement possible with the minimum number of turbines, it is to be understood that the number and arrangement of turbines both for driving compressors and generators or the like for producing net useful power may be varied widely within the scope oi' the invention, and for plants adapted to operate at relatively high pressures and employing a relatively large number of turbines, the reheating as hereinbefore described may be employed between a plurality of expansion stages of the motive fluid.

Also, in the interests of simplicity and clarityv of the disclosure, I have not shown the means employed for starting operation'of the plant, since various means, such as suitably valved reservoirs for compressed air or auxiliary starting motors for starting the compressor turbine or turbines of the plant from an independent source of power, are well known in the art and a description of such apparatus is not deemed to be necessary for an understanding of the present invention.

ILikewise, the invention has been illustrated and described only with reference to the normal operating conditions which the system is designed and expected to meet, and it will be understood that the invention does not exclude the employ- I ment oi' emergency or like control apparatus, for protecting the system against damage or destruction owing to abnormal operating conditions, the 'operation of which emergency appa'- ratus may interrupt or otherwise affect the .continuous free flow of fluids characteristic of the normal operation of the system.

lThe specic manner ci' producing the combi'istion `gases atthe desired temperature, that is, for example, by use of large quantities of excess air to maintain the temperature at a value sumciently low to` enable the gases to be expanded of the invention, and it will be apparent to one skilled in the art that many modifications and variations in the fuel control system may be employed without departing from the invention.

'Ihe number and arrangement of the turbines with respect to flow of motive ,fluid in a given plant and the specific manner of producing and controlling the motive fluid will be dictated largely by the character. of the load for which the plant is intended, and the present invention is therefore not to be considered as limited in its application to any specific plant arrangement but is to be considered as including all forms of gas turbine apparatus falling within the scope of the appended claims when construed as broadly as is-consistent with the state of theA prior art.

The hereinbefore described gas turbine system falls within the scope of the broad subject matter claimed in, my copending application Serial No. 715,267, iiled March 13, 1934, and the disposition of the separate compressor and useful power turbines in the system, with reference to the flow of compressed air and motive uid through the system, shown in Fig. 1 hereof but not herein claimed, is included in the subject matter claimed in my copending application Serial No. 51,230, filed November 23, 1935.

What I claim is:

1. In a gas turbine system of the continuous combustion type, a plurality of gas turbines including a power turbine producing power for external use, each' of said plurality of turbines having a blade system including a plurality of stages of high efficiency reaction blading providing a path for fiow'of motive fluid therethrough with a substantial component of flow in radiv ally outward direction from an inlet of relatively said power turbine with respect to speed of operation, a heating device providing a combustion chamber for heating said compressed medium to produce motive fluid comprising products of combustion, said heating device being located externally of the casings of said turbines, conduit means of substantial length for' delivering said motive lluid to at least one of said turbines. for expansion therein, a reheating device providing a combustion chamber for reheating motive fluid exhausted from at least one of said turbines, said reheating device being located externally of the casings of said turbines, conduit means of substantial length for delivering reheated motive fluid to at least one of said turbines not receiving motive fluid from said heating device, both of said conduit means being arranged for continuous free ow of motive fluid therethrough, and means for controlling .the temperature of the heated motive fluid delivered from said heating device to provide for initial expansion thereof from a temperature within a range of which the lower limit is approximately 800 C. absolute `and the upper limit permits continuous full admission of the motive iiuid to the turbine blading without destruction of the moving blading thereof due to excessive temperature.

2. In a gas turbine system of the continuous cluding a power turbine producing power for external use, each of said plurality of turbines having a blade system including a plurality of stages of high efficiency reaction blading providing a path for now of motive fluid therethrough with a substantial component of flow in radially outward direction from an inlet of relatively small diameter to an outlet of relatively large diameter and having full admission of motive uld to the inlet, means for supplying heated gaseous motive fluid to said turbines including compressor means for compressing a gaseous combustion supporting medium driven by at least one of said turbines operating independently of said power turbine with respect to speed of operation, a heating device providing a combustion chamber for heating said compressed medium to produce motive fluid comprising products of combustion, said heating device being located externally of the casings of said turbines, conduit means of substantial length for delivering said motive fluid to at least one of said turbines for expansion therein, a reheating device providing a combustion chamber for reheating motive fluid exhausted from at least one of said turbines, said lreheating device being located externally of the casings of said turbines, conduit means of substantial length for delivering reheated motive' fluid to at least one of said turbines not receiving motive fluid from said heating device, both of said conduit means being arranged for. continuous free flow of motive fluid therethrough, and means for controlling the temperature of the heated motive fluid delivered from said heating device to provide for initial expansion thereof from a temperature within a range of which the lower limit is approximately 800 C. absolute and the upper limit is approximately 1000o C. absolute.

3. In a gas turbine system of the continuous combustion type, a plurality of gas turbines including a power turbine producing power for external use, each of said plurality of turbines having a blade system including a plurality of stages of high eiciency reaction blading providing a path for ilow of motive iiuid therethrough with a substantial component of now in radially outward direction from an inlet of relatively small diameter to an outlet of relatively large diameter and having full admission of motive fluid to the inlet, means for supplying heated gaseous motive fluid to said turbines including compressor means for compressing a gaseous combustion supporting medium driven by at least one of said turbines operating independently of said power turbine with respect to speed of operation, a heating device providing a combustion chamber for heating said compressed medium to produce motive fluid comprising products of combustion, said heating device being located externally of the casings of said turbines, conduit means of substantial length for delivering said motive fluid to at least one of said turbines for expansion therein, a reheating device providing a combustion chamber for reheating motive fluid exJ hausted from at least one of said turbines,'said reheating device being located externally of the casings of said turbines, conduit means of substantial length for delivering reheated motive fluid to at least one of said turbines not receiving motive fluid from said heating device, both of said conduit means being arranged for continuous free flow of motive fluid therethrough,

vwhich the lower limit is approximately 800 C.

absolute and the upper limit permits continuous full. admission of the motive fluid to the turbine blading without destruction of the moving blad- 'ing thereof due to excessive temperature and to provide for initial expansion of the reheated motive nuid .from an initial temperature approximating the initial temperatureof said heated motive fluid.

4. In a gas turbine system of the continuous combustion type, a irst gas turbine constituting a power turbine producing power for external use, a second gas turbine operating independently of said power turbine with respect to speed of operation. each of said turbines having a blade system including a plurality of stages of high efiiciency reaction blading providing a path for flow of motive iiuid therethrough with a substantial component of flow in radially outward directionfrom an inlet of relatively small diameter to an outlet of relatively large diameter and having full admission of motive fluid to the inlet, means for supplying heated gaseous motive iiuid to said turbines including compressor means driven by said second turbine for compressing a gaseous combustion supporting medium, a heating device providing a combustion chamber for heating said. compressed medium to produce motive fluid comprising .products of combustion, said heating device being located externally of the casings of said turbines, conduit means of substantial length for delivering motive iluid from said heating device tov one of said turbines for expansion therein, a reheating device providing a combustion chamber for reheating motive fluid exhausted from said one of said turbines, said reheating device being located externally of the casings of said turbines, conduit means of substantial length for delivering reheated motive fluid from said reheating device' to the other of said turbines, both of said conduit means being arranged for continuous free flow of motive fluid therethrough, and means for controlling'the temperature of the heated motive fluid delivered from said heating device to provide for initial expansion thereof from a temperature within a range of which the lower limit is approximately 800 C. absolute and the upper limit permits continuous full admission of the motive fluid to the turbine blading without destruction of the moving blading thereof due to excessive temperatures.

5. In a gas turbine system of the continuous combustion type, a rst gas turbine constitutingV a power turbine producing power for external use. a second gas turbine operating independently of said powerturbine with respect to speed of operationfe h of said turbines having ablade system incl ding a plurality of stages of motive fluid therethrough with a substantial component turbine for compressing a gaseous combustion supporting medium, a heating device providing a combustion chamber for heating said compressed medium to produce motive fluid comprising products of combustion, said heating device being located externally of the casings of said turbines, conduit means of substantial length for delivering motive iluid from said heating device to said nrst turbine for expansion therein, a reheating device providing a combustion chamber for reheating motive fluid exhausted from said first turbine, said reheating device being located externally. of the casings of said turbines, conduit meansof substantial length for delivering reheated motive uid from said reheating device to said second turbine, both of said conduit means being arranged for continuous free flow of motive iiuid therethrough, and means for controlling the temperatures of the heated motive fluid and of the reheated motive fluid delivered respectively from said heating device and from said reheating device to provide for initial expansion of the heated motive iiuid from a temperature within a range of which the lower limit is approximately 800 C. absolute and the upper limit permits continuous full admission of the motive iiuid to the turbine blading without destruction of the moving blading thereof due to excessive temperature and to provide for initial expansion of the reheated motive fluid from an initial temperature approximating the initial temperature of said heated motive fluid.

6. In a gas turbine system of the continuous combustion type, a rst gas turbine constituting a power turbine producing power for external use,

a second gas turbine operating independently of said power turbine with respect to speed of operation, each of said turbines having a blade system including a plurality of stages of high eiliciency reaction blading providing a path for flow of motive fluid therethrough with a substantial component of flow in radially outward direction from an inlet of relatively small diameter to an outlet of relatively large diameter and having full admission of motive fluid to the inlet, means for supplying heated gaseous motive fluid to said turbines including compressor means driven by said second turbine for compressing a gaseous combustion supporting medium, a heating device providing a combustion chamber for heating said compressed medium to produce motive fluid comprising products of combustion, said heating device being located externally of the casings of said turbines, conduit means of substantial length for delivering motive fluid from said heating device to said flrst turbine for expansion therein, a reheating device providing a combustion chamber for reheating motive uid exhausted from said flrst turbine, said reheating device being located externally of the casings of said turbines, conduit means of sub- -stantial length for delivering reheated motive iuid from said reheating device to said second turbine, both of said conduit means being arranged for continuous free flow of motive fluid therethrough, and means for controlling the temperatures of theheated'motive fluid delivered from said heatingdevice and of the reheated motive fluid delivered from'said reheating device to provide for initial expansion thereof in the respective turbines from temperatures within a range of which the lower limit is approximately 800 C. absolute 'and the upper limit is approximately 1000 C. absolute.

ALF LYSHOLM.

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