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Патент USA US2132212

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@eto 4l, H9„
J. E. JoHANssoN
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MEANS FOR UTILIZING EXHAUST STEAM
Filed NOV. 17, 1953
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„L E, JOHANSSON
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MEANS FOR UTILIZING EXHAUST STEAM
Filed NOV. 17, 1935
Whig’ 7
5 Sheets-Shes?I 2
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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.
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