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@eto 4l, H9„ J. E. JoHANssoN ¿www MEANS FOR UTILIZING EXHAUST STEAM Filed NOV. 17, 1953 . 5 Sheets-Sheet l f „Vgn 434/ , Q G @5am/@MM ¿a ATTORNEY @QL 4, 1938., „L E, JOHANSSON ~ ZÄSÃZHZ MEANS FOR UTILIZING EXHAUST STEAM Filed NOV. 17, 1935 Whig’ 7 5 Sheets-Shes?I 2 65 6g //2 @ffßmwi ¿à A TORNEY @ct- 49 @3%. 2,222,212 J. E. JoHANssoN MEANS FOR'UTILIZING EXHAUST STEAM Filed Nov. 17, 1935 3 Sheets-Sheet 5 2 IïVENTOR BY ¿i ATT‘oRN d 2,132,212 Patented Cet. 4, 1938 ` UNITED STATES PATENTv OFFICE 2,132,212 MEANS FOR UTLLIZING EXHAUST STEAM ‘ Johan Erik Johansson, Goteborg, Sweden, as signorv to Aktiebolaget Götaverken, Goteborg, Sweden, a corporation of `Sweden Application November 17, 1933, Serial No. 698,512 In Sweden June 5, 1928 (Cl. 60-21) 4 Claims. This application is a continuation in part re placing my copending application lSerial No. 383,132, filed August 2, 1929. The present invention relates >to means for uti lizing exhaust steam of reciprocating steam` en gines and has for its general object the provision .of means for transforming the available heat content of the exhaust steam into energy ab sorbed by the steam during expansion in the re m cipro'cating steam engine. More particularly, the invention relates to steam power plants com prising a reciprocating steam engine, the exhaust steam of which is utilized in a steam turbine driving one or more pump devices in. order to compress steam expanded in the reciprocating steam engine to a higher pressure, thus trans forming the outputof the exhaust steam turbine into heat energy absorbed by the >steam in the reciprocating engine. 20 _, ` Still more particularly, the invention aims to Figs. 4 and 5 are diagrams illustrating the mode of operation of the turbo compressors used in the steam power plant according to the invention; Fig. 6 is a modification of the steam power plant illustrated in Fig. 1; ,.5 Fig. 'l is a sectional view in an enlarged scale taken on the line VII--VIIof Fig. 6; and Figs. 8 and 9 are details of Fig. '7. Referring now to Fig. 1, reference numeral I indicates a reciprocating steam engine arranged ` for -triple expansion of steam in the cylinders 2, 3 and 4 thereof, high pressure steam being sup plied from the steam generator 5 through the conduit 9 to the main stop valve 'I and, there from, to the piston valve 8. After expansion in the high pressure cylinder 2 the steam passes through the pipe 9, which serves as a receiver, into the distributing valve »chest II) and to the piston valve II and, therefrom, into the inter mediate pressure cylinder 3. After having ex- _ provide combinations and arrangements of parts panded therein, the steam is exhausted into the in such a manner that all of the cylinders of the reciprocating steam engine can be driven by su perheated or at least drier steam than hitherto has been the case. 25 Another object of this invention is to provide receiver I2 and then enters, by means of the slide valve I3, the low pressure cylinder 4 which exhausts the steam expanded therein into the exhaust steam pipe I4 connected with the con denser I5. The pipe I4 is further connected by means for increasing the smallest 'quantity of steam conveyed by the pump device per unit of time in order to obviate a steamflow through the pump device in a direction opposite >to the in means of a pipe I6 with an exhaust steam turbine ciprocating engine I. After having expanded in the exhaust turbine I'I, the steam flows through tended one. a conduit I8 into the condenser I5. 3 . Il driven by steam ñnally expanded in the re A further object of the invention consists in the provision `of a pump device for ìthe purposes set forth above, which under the greatly varying operation conditions _can be driven with the high The steam turbine I‘I drives by means of a shaft 92, a low pressure turbo compressor vI9 ro tating at the same speed as the turbine. A gear est possible efficiency. means of a shaft 93 partly lying below the shaft 92, a reciprocating high pressure compressor 2l. The exhaust steam pipe I4 is also connected with a pipe 22 conducting steam to the suction side of , g >A still further object of the invention is to provide means for bleeding steam from the re ciprocating engine for heat exchanging purposes, said means being arranged so as to conduct, as far as possible, vall moisture from the engine to the heat exchanging apparatus. ing 2U connected with the turbine drives, by 3 the compressor I9. Stop valves 23, 24, and 25 are arranged in the pipes I4,l I6, and 22, respec tively. A container 26 located in the pipe 2.2 For a better understanding of the nature of the invention and the manner in which it is carried into eiïect, reference may be had to the accom serves to equalize the diiîerence between the panying drawings forming a part of this speci ñcation and the following description thereof. In the drawings: Fig, l is a plan view, partly in section, showing sor I9 per unitof time.' The pressure side of the compressor I9 is connected, by means of a pipe 50 an embodiment of the invention; Fig. 1a is a section taken on the line Ia--Ia of Fig. 1. Fig, 2 shows an indicator diagram; Fig. 3 shows a modification of a detail of Fig. 55 1 in section. , \ quantity of steam flowing into the pipe 22 and the quantity of steam sucked in by the compres 2l, with the receiver I2 at a point .adjacent the slide valve I3. A pipe 28 connects the receiver I2 with the suction side of the compressor ZI. The pressure pipe 29 of this compressor is connected with a superheater 39 arranged in the flue pas sage 3I of the boiler 5 and, by means of pipe 32, with the receiver pipe 9 at a point adjacent the piston valve I I. A by-pass pipe 44 »havingv a 55 .2. 2,132,212 throttle valve 45 connects the pressure side of the turbocompressor with its suction side. During normal operation, the stop valve 23 is in closed position whereas the valves 24 and 25 are opened so as to allow flow of steam from the exhaust pipe I4 to the steam turbine I"I and to the compressor I9. The steam sucked in by thus provided superheated steam delivered from the compressor will tend to flow in a relatively short and direct path to the slide valve I3, where as the preheater 34, the inlet of which is adja cent the valve II, will tend to draw oiî the rela tively low quality steam discharged from the latter valve. With the arrangement illustrated, the compressor I9 is compressed to a pressure which is substantially equal to the pressure pre the natural path of flow of steam admitted to vailing in the receiver I2, whereupon this steam, which has been superheated or at least dried pressor discharge conduit 21 will tend to main 10 tain a substantially higher quality of steam into by compression, is conducted through the pipe 21 the zone adjacent to the valve I3 than in the Zone the receiver I2 from valve II and from the com to the said receiver for further expansion in the adjacent the inlet to the preheater. Consequent low pressure cylinder 4. It is obvious that the ly, the high temperature steam delivered from the compressor is substantially utilized in the 15 mixture of steam entering the low pressure cylin der will have a higher temperature or be drier succeeding cylinder of the engine and preheat than the steam exhausting from the interme ing is accomplished by steam of relatively low diate pressure cylinder. Thus, the output of the ' quality as exhausted to the receiver. low pressure cylinder will be increased materially Itis further to be noted that in view of the 20 and the low pressure cylinder will be fed with general flow of the steam through the receiver superheated or dry steam. In this manner, a from the valve II toward the valve I3, the rela portion of the output of the exhaust steam is tive positions of the inlet end of conduit 28 and rendered serviceable for the low pressure cylinder the outlet end of conduit 2ï leads to a natural in the form or" an increased quantity of steam of tendency for conduit 28 to withdraw steam of lower rather than of higher quality from the 25 a higher temperature or at least having less mois ture and a pressure suitable for utilization in this receiver. If this latter steam contains moisture, cylinder. The receivers 9 and I2 communicate in such moisture will, as far as possible, be drawn a similar manner with the high pressure com oiî by the pipe 31. In the same manner, the pressor 2l by means of’ the conduits 28, 29, and steam compressed by the high pressure compres 30 32. The steam taken out from the receiver I2 is sor 2l enters the receiver 9 at a point adjacent compressed by the reciprocating compressor 2| the piston valve II, Whereas the pipe 38 is con to a pressure which is substantially equal to the nected with the receiver 9 at a point adjacent the outlet of the high pressure cylinder 2. pressure Vprevailing in the receiver 9. 'I‘he com pressed steam which has been superheated by In order to reduce the dimensions of the com pressors and the work of compression, the pres 35 compression is still more superheated in the su perheater 3B. sure of the steam supplied to the compressors As will be seen from the drawings, the steam should, if possible, be higher than the pressure which has been compressed by the high pressure prevailing in the cylinders during the exhaust period. This may be effected if the steam of a compressor is conducted back to the reciprocat higher> pressure exhausted from the cylinders 40 ing engine at a point >situated behind the high pressure cylinder, since the compression of steam during the exhaust lead period is supplied to up to the pressure prevailing in the live steam the compressors, While the steam exhausted dur ing the exhaust period is utilizedv for further pipe would cause considerable diñ’iculties. There fore, I prefer to compress the steam to a pressure expansion in the following cylinder or in the ex haust turbine respectively. Therefore, if accord 45 not higher than the pressure prevailing in the iìrst receiver. ing to Fig. 2 which illustrates, by Way of ex If it is desired to disconnect the turbine and ample, the indicator diagram of the low pressure cylinder, p representing the pressure and o the the compressors, this may be eiîected by con ducting the steam through the exhaust pipe I4 volume of steam, the exhaust lead period begins atthe point 4I, an increased average pressure of 50 directly into the condenser I5. For this purpose, the valve 23 is opened and the valves 24 and 25 the steam supplied to the compressor may be ob tained. are closed. In Fig. 1, I have also shown means for bleeding Y , For this purpose, the stop valve 25 inthe con steam from the reciprocating steam engine, this duit 22 may be replaced by a non-return valve opening in the direction to the suction side of 55 steam being used for preheating of feed water. For this purpose, three feed water preheaters 33, the compressor. Fig. 3 shows this modified ar 34, and 35 are connected to the reciprocating rangement. As the steam quantity entering the pipe I4 during the exhaust lead period of the steam engine by means of pipes 36, 31 and 38 re loW pressure cylinder is materially greater than spectively. 'I‘he feed Water passes from the con 60 denser I5 through the pipe 39 and the preheaters the steam quantity’entering simultaneously the to the pump device 40 and, therefrom, into the steam turbine I1, the pressure in the conduit I4 will increase. The non-return valve 42 then boiler 5. 'I'he feed Water preheater 33 is con nected with the exhaust side of the valve chest opens and the greatest portion of the steam ex of the low pressure cylinder so that a portion of hausted during the exhaust lead period flows into 65 the steam finally exhausted in the reciprocating the container 26. As during the exhaust period engine is conducted to this preheater. The next the pressure decreases in the conduit I4, the preheater 34 is connected with the receiver I2. non-return valve closes and prevents the steam As the pressure side of the compressor> I9 is con of higher pressure from ilowing back to the con nected with the same receiver, I have chosen such duit I4. The steam exhausted during the ex 70 an arrangement of the pipes 21 and 31 that steam haust period will then flow to the steam tur compressed by the compressor I9 is conducted bine I1. into the receiver I2 at a point adjacent the slide On account of the great variations of the ñoW valve I3 whereas the steam to be tapped off from of steam through the cylinders of the recipro this receiver is taken out at a point adjacent the cating steam engine and the great changes in 75 piston valve II. Because of the arrangement the steam quantities conveyed to the compressors, 15 20 til() '. 70 «2,132,212 the compressors will Work A.under peculiar operat ing-conditions. I vhave found that, if the turbo By a similar calculation for a plurality of other efñciency curves the determination of curve 5D compressor is constructed in the ordinary man ner so as to normally give its maximum efliciency with the steam quantity conveyed per unit 4of has been effected; time, the efficiency obtained will actually be con siderably lower. I therefore, construct the turbo compressor so that its maximum efficiency occurs with a 'quantity'of steam exceeding the average Y10 quantity conveyed per unit of time by at least 25 per cent. The operating conditions of the turbo compressor will be described more partic ularly in connection with Figs. 4 and 5. f Referring to Fig. 5, V represents the volume V15 which, zat .a certain `crank position of the recipro 1.5 Vm, whereupon it slowly falls with greater V-values. Consequently, the compressor should .be so constructed as to have its maximum effi ciency at a volume of 1.5 Vm, it being possible, however, to permit variations of this Volume be tween the limit values 1.25 Vm and 2.5 Vm With out :the average efficiency being materially low ered. By an overdimensioning of the compressor, which may be effected, for instance, by increasing ` the width ofthe channel areas of common turbo compressors, the Iadditional advantage is obtained ’eating steam engine, flows through the com ‘pr-.essor per unit of time. The line 46 indicates the changes in volume during one crank revolu that the friction losses during the flow of steam tion and the line 41 represents the average volume through the compressor are reduced. Vm conveyed during said period. In the corre sponding diagram in Fig. 4, the abscissae of the coordinate system represent >the volume conveyed to the compressor andthe ordinates thereof rep resent the efliciency of the compressor. “Curve 48 ‘indicates the changes of the pressure efficiency n with the volume V with a compressor intended to give its maximum eiliciency at the average volume Vm, While vcurve 49 indicates the changes of the ef’riciency of a `compressor which gives its maxi mum -eiiiciency at a volume of 1.5 Vm. Ina com pressor loperating .with the changes of volume in dicated by curve 46 and having an eiñciency curve according to 48, `an average eñiciency is obtained which'corresponds to the distance 5I indicated in In Fig. 4 also a curve 53 has been shown, which indicates the pressure-increasing ability of the turbo-compressor at different values of the steam volume conveyed. It will be seenfrom the dia gram that the pressures are remarkably low at small steam volumes, that is to say for the extent îit Ikof lthe `diagram denoted by 54-55. This cir cumstance is explained by the fact that av per-i odic flow of steam `takes place through the com .pressor in a direction opposite to the intended one for said portion of the diagram. As the .energy .transferred by the compressor to the steam is lsubstantially constant, the main portion of the energy is under such circumstances transformed into an increase `in temperature of the steam. An increase «in pressure as far vas >possible would '185 the diag-ram, whereas the average efliciency of a compressor with an efficiency curve according to 49 «reaches a considerably higher value repre .of energy is easier to transform, by means >of the sented by the distance 52. reciprocating steam engine, into mechanical work. The upper ends of these two distances 5I and 52 are situated on a curve 5l) on which a plurality of points may be be, however, more `desi=rable„since this latter form To ensure -such >an increase of the pressure, the .turbo compressor t9 -is ‘by-passed Lby pipe -44 in calculated for compressors with other efficiency which is inserted a throttle valve 45. curves. «of pipe 44 a portion of steam .which has already :been compressed is returned to the suction side of After such Va curve 5l] has been plotted it will .be possible to determine the average efli c‘iency 11m under the conditions indicated for a compressor which is dimensioned so as to have its maximum efficiency at the volume correspond 'ing vto ‘the point of the curve where the average efficiency is read off. `The curves 48 land 43,'and corresponding curves ‘for other volumes, have ybeen obtained by tests with turbo compressors, and for the determina .tionof curve .50 the following equation has been Iused.: _ EVí'v] By means vthe compressor, in order thus to prevent the en trance :of too .small -steam Volumes conveyed by , ¿the compressor per unit of time. In Fig. 5, the vdiagram 'designated `by 46 shows the variations of the Ivolume Aconveyed >by the compressor per vunit of time if :there is no return of steam from the pressure side to the `suction side thereof, and the combination with curve 53 on Fig. 4 makes it icl‘ear that the pressures corresponding .to the smallest volumes will fall >on the portion of the pressure curve >53 extending between the points 54and :55. _Vmzf’ ‘ , ~ In consequence of the steam »quantity which where ‘t represents the time during which .the vreturns through the `by-pass pipe 44 to the suction volume V iiows through the compressor. i If 2t side of the compressor, :a steam quantity corre represents the time of one revolution of the re sponding to curve 56 indicated -in Fig. 5 Aby chain dotted «lines will then flow through the com pressor, so that all volumes ycorresponding to the »portion 54-55 willfbe avoided. With the ar rangement .-set forth, the compression in the com vpressor'may thus 'be caused to develop exclusively ciprocating steam engine, this expression can be replaced by 360°, t being measured in degrees on the `diagram in Fig. 5. For the calculation of 11m for a compressor having an efñciency curve according :to curve 48, for example, the volume V 65 is measured for a certain small angular displace ment t" v.on the diagram in Fig. 5. With .the value ofV'thus obtained the value of the correspond ing n is `measured Von the curve 48. After the wholediagrarn'liß has been vmeasured in this man 70 ner and ‘multiplied by the corresponding q-values, EVîqcan -be obtained and thus also __ 73 , It will .appear from the form of this curve that it has its lowest value at small volumes, and that it reaches a'maximum value at a Volume of about ' EV?‘r] _Vm 36o îllherehyapointshas been .deter-mined .on curve 50. according 4to the portionon the »right of point 55 of the pressure ‘curve .53 shown in Fig. 4, the best »economical result being thus obtained, in that the `energy supplied by the compressor is trans formed as far as possible into an increase of the _pressure of the steam. l» 170 In the modification shown »in Figs. `6 to ~9, the live Asteam enters `the distributing valve chest 51 zand, .after .having 'expanded ‘in the high» _pressure cylinder ‘2, enters the vreceiver :58. The steam .then `ñovvs through ‘the intermediate and .low 75 4 2,132,212 pressure cylinders 3 and 4, respectively, into the exhaust steam pipe I4, as described in connection with Fig. 1. The piston valve II of the inter mediate pressure cylinder and the slide valve I3 of the low pressure cylinder are connected by means of a pipe 59 which serves as a part of the low pressure receiver I2. The exhaust steam turbine I1 drives two turbo compressors I9 and 60, respectively. 'I'he suction side of the low 10 pressure compressor is connected to pipe 22 and its pressure side is connected, by means of pipe 21, with the low pressure receiver 59, I2. By means ol the pipe 28, the high pressure corn pressor 50 sucks in steam from the receiver 59, 15 and the co-mpressed steam is conducted through pipe 29, superheater 30, and pipe 32 into the re ceiver 58 at a point adjacent the piston valve II of the intermediate pressure cylinder 3. The pipe 31 for bleeding steam from the low pressure 20 receiver is connected to pipe 59 at a point adja cent the steam outlet chamber 6I of the inter mediate pressure cylinder, while the pipe >38 through which steam of higher pressure is bled, is connected with the outlet chamber 62 of the 25 high pressure cylinder. Y Allof the parts indicated in Figs. 6 and '7 by the same reference numerals as in Figs. 1 and 3 serve the same purpose and operate in the same manner as the corresponding parts of Figs. 1 30 and 3. While the low pressure compressor I9 is by passed by a pipe 44 with a throttle valve 45 in the same manner and for the same purpose as in Fig. l the high pressure compressor 69 is by passed by a pipe 63 connecting the receiver 58 with the receiver 59. The connecting pipe 63 is provided with a stop valve 64 and with a control ling device 65 which is shown on a larger scale in Fig. 9. The controlling device 65 comprises a 40 cylinder 66 and a double piston 61 rigidly con nected with the piston valve I I. The upper part 2) before the beginning of the exhaust lead period representedat 4|, whereby steam of a higher pressure is supplied to the suction conduit of the compressor. In this case, the pressure curve will sink somewhat as indicated in Fig. 2 f by dash lines. To effect this mode of operation, the cylinder covers 1I and 12 of the low pressure cylinder are provided with valves 13 and 14, respectively, con nected with pipes 15 and 16, respectively, which supply the steam drawn off from the cylinder to the container 26 and the compressor I9. The pipes 15 and 16 may be connected by a pipe 94. Under the influence of springs 11 and 18, the valves 13 and 14 are normally kept in closed posi :15 tion. .The valve 13 is actuated by means of a lever 19 which is connected with a rod 80 guided by a bracket BI. The lower end of the rod 88 is provided with a roll 82 cooperating with a cam wheel 88. A spring 84 prevents disengagement of 22g) the roll 82 and the cam wheel 83. The cam wheel is keyed on the crank shaft 85 and has an out wardly projecting cam 86 and, o-n the opposite side, a recess 81. When the cam wheel is turned from the posi-- .-25 tion shown in Fig. 8 in a counter-clockwise direc tion, the cam 86 will cause an upward movement of the rod 80 and a movement of the lever 19 about its iulcrum 88 in a clockwise direction, whereby the valve 13 is opened against the resist ance of the spring 11. The cam 86 has such a position relatively to the crank 89 of the low pres sure cylinder that the valve 13 begins to open at a point of the steam process corresponding to the point 43 in Fig. 2. The valve 14 on the other cylinder cover is actuated in a similar manner by means of the lever 90 likewise connected with the rod 88. When the recess 81 of the cam wheel is in a position below the roll 82, the rod 80 will be moved downwardly and the lever 90 turned in a counter-clockwise direction, thus opening the valve 15 against the resistance of the spring 18. of piston 61 and the cylinder 66 are provided with apertures 68 and 69, respectively, these apertures controlling the ilow of steam from the receiver 58 45 through the pipe- 63 to the receiver 59, depending on the position of the double piston 61 during each revolution of the reciprocating engine; The two parts of the double piston and the apertures fined my consideration to a. steam power plant are situated relatively to each other in such a 50 manner that a flow of steam through pipe 63 is two compressors, it will be understood that the By means of a hand lever 9|, the cam wheel 83 is movable to a position indicated by 92, the valves 13 and 14 then being out of operation. While in the foregoing description I have con comprising a triple expansion steam engine and possible only during those periods in the engine cycle when the steam quantity conveyed by the invention is not confined tof this specific arrange ment but may equally well be embodied in steam turbo compressor 60 tends to fall below the value power plants in which two or more cylinders are indicated by the point 55 in the diagram of 55 Fig. 4. During such periods the controlling de vice 65 is opened by movement of the piston valve boiler pressure to exhaust pressure and only one compressor is provided for the compression of I I so that, during these periods, a steam quantity according to the curves 10 in Fig. 5 will flow through the compressor 60 in order to prevent 60 the- entrance of too small volumes conveyed by the compressor per unit of time. The arrange ment of the controlling device is somewhat more complicated than the single throttling valve 45, but offers, on the other hand, the advantage that an increase of the steam volume conveyed by the compressor takes place only during two short periods of each revolution of the reciprocating steam engine, thus decreasing the necessary amount of work required by the compressor. In the modification according to Figs. 6 to 8, 70 I have also shown an arrangement adapted to draw off steam from the low pressure cylinder 4 to the low pressure compressor I9 during the expansion in the cylinder, an exhausting means being controlled so as to open at a point 43 (Fig. employed for expanding the steam down Afrom steam. what 1 Claim isz- f .5.5 ‘ ' l. In a steam power plant, a reciprocating steam engine having a plurality of cylinders for multiple stage expansion of steam in the engine, said cylinders being double acting and the op posed ends of the same cylinder operating to ex pand steam through the same pressure range, means for admitting steam to and exhausting 65. steam from each of said cylinders, a compressor, a turbine for driving said compressor, a conduit for conducting steam exhausted from one of said cylinders to the suction side of said compressor and a second conduit for conducting compressed steam from said compressor back to said engine for reexpansion therein, said compressor being constructed to operate with maximum efliciency when steam is supplied thereto at a rate equal to at least one and one-quarter times but not exceed 2,132,212 ing two and one-half times the average rate at which steam is delivered by the engine. 2. In a steam power plant, a reciprocating engine having a plurality of cylinders for multi ple stage expansion of steam in the engine, said cylinders being double acting and the opposed ends of the same cylinder operating to expand steam through the same pressure range, means for admitting steam to and exhausting steam from 10 each of said cylinders, an exhaust steam turbine for expanding exhaust steam from said engine to a pressure lower than that to Which the steam canl be expanded in the engine, a compressor driven by said turbine, a conduit for conducting steam ex 15 hausted from one of said cylinders to the suction -side of said compressor and a second conduit for conducting compressed steam from said compres sor back to said engine for reexpansion therein, said compressor being constructed to operate with 20 maximum eñiciency when ste-am is supplied there to at a rate equal to at least one and one-quarter times but not exceeding two and one-half times the average rate at Which steam is delivered by the engine. 3. In a steam power plant, a reciprocating ' engine having a plurality of cylinders for serial expansion of steam therein, means for admitting steam to and exhausting steam from each of said cylinders, steam pumping means, a conduit for conducting steam exhausted from one of said cylinders other than the high pressure cylinder with the suction side of said pumping means, a 5 second conduit connecting said one of said cylinders with the suction side of said pumping means, valve means for controlling iiow of steam through said second'conduit, said valve means being opened and closed in accordance with the position of the crank shaft of said engine to per mit steam to flow through said second conduit during a predetermined period of the engine cycle, and a third conduit for returning the steam de livered from said pumping means to said engine .for further expansion therein. 4. In a steam power plant, a reciprocating engine having, a plurality of cylinders for serial expansion of steam therein, means for admitting steam to and exhausting steam from each of said 15 cylinders, a steam turbine, a conduit for conduct ing exhaust steam from said engine to said tur bine, pumping means driven by said turbine, a second conduit for' conducting exhaust steam from said engine to the suction side of said pump 20 ing means, a third conduit connecting the low pressure cylinder of said engine with the suction side of said pumping means, valve means for controlling flow of steam through said third con duit, said valve means being opened and closed 25 in accordance with the position of the crank shaft of said engine to permit steam to fioW through said third conduit during a predetermined period of the engine cycle, and a fourth conduit for re turning steam delivered by said pumping means to 30 said engine for further expansion therein. JOHAN ERIK JOI-IANSSON.