Note: Descriptions are shown in the official language in which they were submitted.
TITLE: TURBIN~
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This invention relates to a turbine.
A ~urbine typically comprises a rotor, a multiplicity
of nozzles through which working fluid is directed into
blades of the rotor, a supply chamber and valve mean~
controlling the flow of working fluid from the supply
chamber to the nozzles. In turbines of the so-called
throttle governecl type, the valve means comprises a
single valve whlch controls the flow o fluld to all
oE the noz~les in unlson. In turbines of the so-called
nozæle governed type, the valve means ls composed o~ a
plurality of separate valves which are operated sequentially
to control flow of the working fluid to separate groups
of nozzles. It is generally accepted that throrrtle
governed turbines have much lower thermodynamic efficiency
under partial load operation than nozzle governed
turbines. ~owever, nozzle governed turblnes are more
complex and expensive.
An inherent problem of conventional nozzle governed turbines
is that the supply chamber has a specific number of control
valves of fixed geometry and dimension. Therfore, changes
in the mass flow and condition of the working fluid necessitate
the use of supply chambers of different pressure/temperature
capability, size and control valve configuration. Unless
the supply chamber is thus replaced, such conventional
turbines are somewhat inflexible in their operational
capabilities.
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It is an object of the present invention to provlde a turbine
of the nozzle governed type which is comparatively simple
in construction, relatively inexpensive to produce, and
which enables changes in the mass flow and condition
of the working fluld to be acc:ommodated ln a simple manner.
According to the present invention, there is provided a
turbine lncluding a rotor, a multlplicity of nozæles
through whlch working fluld is directed into blade~ of
the rotor, the nozzles being clivided lnto a plurality of
groups with the noz~les in each group being ~upplied with
the working fluld from a supply chamber through respective
conduit means, and valve means controlling the flow of
the working fluid from the supply chamber to the conduit
means, the valve means comprising a tubular valve seat
having a plurality of radial ports which communicate with
the conduit means respectively and a valve member received
within the valve seat and movable relative thereto to
open and close the radial ports selectively, the val.ve
seat being removably mounted in the turbine and being
replaceable by other valve seats having radial ports
different in shape, size, disposition and/or number.
In this way, the turbine performance can be modified
simply by replacing one comparatively small component,
namely the valve seat. Moreover, such replacement can be
readily carrisd out on site. The number of radial ~orts
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in the valve seat and their size, shape and dlsposltion
will deterimine the sequence ln which the nozzle~ are
brought into or out of operation as the valve means is
opened or closed, the manner in whlch the nozzles are
grouped (i.e. the nozzles which are brought into
operatlon at any given posltion of the valve means), the
so-called "swallowing capacity" of the turbine, and the
modulation of the working fluid.
Deslrably, the supply chamber ls removably mounted on a
casing withln which the rotor is rotatably dlsposed, and
the valve seat is removably mounted between the casing and
the supply chamber co-axially with the rotor axis. In
an alternative arrangeme~t, however, the valve seat is
contained wlthin the supply chamber and the latter is
disposed remotely from the rotar casing, with the radial
ports in the valve member being connected to the respective
nozzle groups by way of external pipes.
The capabillty of the turbine can be modified still
further, with particular reference to the mass flow of
the working fluid, by employing a construction wherein the
casing comprises an open-ended body part within which
the rotor is rotatably mounted and a cover removably
closi~l~ the open end of the body part and containing the
nozzles, the conduit means is formed by internal passages
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withln the cover, and the valve seat ls received in a
cyllndrical bore in the cover into which the passages
open. In this case, the cover can be replaced by other
covers having different-sized bores therein for reception
of other correspondingly different-si~ed valve seats.
Moreover, the various covers can also have different
arrangem~nts of the said passages thereln : for example,
passages of dif~erent mean diameter, size and number.
Conveniently, the radial ports are spaced apart axially
of the valve seat, and the valve member is movable axially
of the latter. In this case the valve member can comprise
a hollow tubular body whose peripheral wall covers the radial
ports successively as the valve member ls moved axially
of the valve seat, the valve member being open at both
axial ends thereof. This latter measure ensures that
the valve member is pressure balanced.
The valve member can be moved by mechanical, hydraullc, pneumatic
or electrical means, for example. Where this is performed
mechanically, a linkage preferably connects the valve
member to a crank which is mounted on a rotatable shaft
for rotation therewith, the crank and the linkage being
contained within the supply chamber with the shaft extending
rotatably and sealingly through a side wall thereof.
This particular arrangement eliminates pressure differential
out-of-balance.
Operation of the valve member can be achieved automatically
by means of a control mechanism, which can be governor-
operated for example. ~lternatively, the valve member can
be manually operated. In one position of the valve member,
it can be arranged that all o~ the radial ports are closed
off, so that the valve member can be used to effect
emergency shut-down of the turbine, for example.
The valve member and preferably also the valve seat can be
made of stalnless steel or nitrided steel.
Advantageously, the nozzles are arranged in at least one ring
and are divided into a plurality of ~rcuate rows each
extending part-way around the rotor axis, and each radial
port in the valve seat communicates with the nozzles in
a respective one of the arcuate rows. Desirably, the
nozzles in each arcuateroware in communlcation with a
respective arcuate passage with which the respective
radial port in the valve seat also communicates.
An embodiment of the present invention will now be described,
by way of example, with reference to the accompanying
drawings, in which:-
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Flgure 1 is an axial cross-section of a first embodiment
of a turbine according to the present inventlon;
Figure 2 is an enlarged view of a valve which forms part
of the turbine shown in Figure 1;
Figure 3 is an end view of a casing cover assembly which
also forms part of the turbine shown ln Figure 1; and
Figure 4 is an axial cross-section of a second embodiment
of a turblne according to the present inventlon,
illustrating in particular a control mechanism therefor.
The turbine illustrated in Figures 1 to 3 comprises a
casing having an open-ended body part 10 within which a rotor
11 is mounted for rotation about an axis 12. The open end of
the body part 1~ is closed by a cover 13 having a
plurality of equi-angularly spaced nozzles therein which
confront blades 14 (only one shown) on the periphery of
the rotor 11. In operation of the turbines, working
fluid is expanded through the nozzles and directed into
the blades 14 to rotate the rotor 11 in a known manner.
Each nozzle comprises an insert 15 received within a stepped
axial bore 16 in the cover 13, the inserts 15 being retained
in their respective bores 16 by an annular clamping ring
17 and being sealed against leakage by respective 0-
rings 18. Formed within the cover 13 are arcuate
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passages 19 ~lndicated by broken llnes in Eigure 3) from
which the bores 16 lead. In the illustrated arranyement,
eight such passages 19 are prov:Lded in equi-angularly
spaced relation, and the nozzles are divided into eight
arcuate rows with ~he nozzles in each row communicating
with a resp~ctive one of the arcuate passages 19. A
different number o~ arcuate passages can, however, be
provided if desired.
A radial pas~age 20 extends from each arcuate pas~age
19 and opens onto a central axial bore 20a in the
cover 13. Disposed within the bore 20a is a tubular valve
seat 21 which is co-axial with the rotation axis 12 of the
rotor. The valve seat 21 is retained axially by a clamplng
flange 22 on a hollow spigot 23 of a pressure vessel
or supply chamber 24 to which pressurised working fluid is
supplied in use, the supply chamber 24 being removably
mou~ted on the cover 13. . Radlal ports 25 are formed
in the valve seat 21 in axially and angularly spaced relation.
Each port 25 opens into a respective part-annular groove
26 in the radially outer surface of the valve seat 21,
each groove 26 communicating with the radial passages 20
and respective arcuate passages 19.
The flow of working fluid between the supply chamber 24
and the nozzles is controlled by a valve member 27 which
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is axially movable within the valve seat 21. Both the
valve member and the valve seat are made of stalnless
steel or nitrlded steel. The valve member 27 is in the
general form of a hollow cylindrical piston, and is
operatlvely connected to a crank 2~ on a rotatable control shaf t
29 by way of a link 30. The crank 28 and the link 30
are disposed withln the chamber 24, whereas the control
shaft 29 extends ro~atably and sealingly through a side wall
of the chamber 24 and ls connected to a governor-operated
control mechanism (not shown).
Angular movement of the shaft 29 causes the valve member
27 to move axially of the vaLve seat 21. In the position
shown in the drawin~s, all of the radial por~s 25 are
uncovered by the valve memb~r, and therefore pressurised
working fluid can pass from the supply chamber 24 through the
valve to all of the nozzles so that the turbine oper~tes
at full power, i.e. under fuLl load. I the load on
the turbine should lessen, the resultant increase in
speed of the rotor will be detec~ed by the control
mechanism, as a result of which tne control shaft 29 is
rotated to move the valve mem~er 27 so as to reduce
fluid flow through one or more of the radial ports 25 the
turbine power is consequentl~- reduced in correspondence
to the reduction in load. If the load on the turbine
then increases, the rotor will momentaril~ slow down
and the control mechanism will move the valve me...ber
in the reverse direction ~o increase the flow of working
fluid through the increased area of the radial ports 25 once
aqain.
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If the valve member is ~oved to the extreme left as
viewed in Figure 2, it will shut off all of the radial ports
25. Henc~, pressurised working fluid will be unable to flow
to any of the nozeles, resulting in a shut-down of the
.urbine. This action can be performed under emergency
conditions, for example.
As an alternative to a governor-operated control
mechanism, the control shaft 2g can be connected to
a ~imple hand crank or hand wheel so that the above-
described power ad~ustment3 can be performed manually.
The number, size, shape and disposition of the rad~al ports
25 and the corresponding~rooves 26 in the valve seat
21 determine the amount of working fluid which can flow
to each arcuate row of nozzles and the seque~tial mode
in which these rows are placed into and out of
communication with the supply chambér 24. These factsrs
can be altered to suit the partlcular application of
the turbine merely by replacing the valve seat 21 with
another having suitable charac~eristics. Moreover, further
alteration of the turbine characteristics can be achieved
by replacing the supply chamber 24 and the casing cover 13.
In the former case, various supply chambers can be provided
of different sizes, wall thickness and material according
to the mass flow and pressure/temperature condltion of the
working fluid. In the latter case, various covers 13 can
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be provided having a different number of passages 19 and
20, and wherein the mean diameter of arcuate passayes 19 may
be varied. In additlon, covers having different-sized central
ax$al bores 20a can be provided for accommodating correspondlngly
dlfferent-slzed valve seats 21.
It will therefore be apparent that the configuration and
size of the cover 13, the valve seat 21, the valve member
27 and supply chamber 24 are all varlable to a large degree
in order to cater for various operational requirements of
the turbine. Moreover, the radial passages 20 provide
unrestxicted communication between the arcuate passages 19 and
radial ports 25 in the valve seat 21 in all cases.
Since thP valve member 27 is open at both of its axial
ends, it is completely pressure balanced and lts cut-off
action can be modulated to minimise resistlve fluid
flow forces. Positive positioning of the valve member can
thus be achieved with minimal torque requirement on
the control shaft 29, thereby eliminating the need for complex
and expensive servo-systems which are normally associated
with nozzle governed turbines.
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The turbine illustrated in Figure 4 lS generally similar
to that described above with reference to Figures 1 to 3,
and therefore similar parts have been accor~ed the sa~e
reference numerals with 100 added. Reference numerals
t40 ar.d 141 denote respectively an ir.let and an outlet
for the passage of workir.g ~luid through the turbine.
In Fiqure 4, the governor-operated control mechanism
.~hich controls movement of the valve .-.e~ber 127 is sho~n
in detaLl, and cor.;pris~s generally a ~echanieal go~;ers.or
142 ~which ls rotated with the turbine ro~cr I 11 D'~ ~,Jay
of qearing 143. An axially movable me~ber 144 of th~
governor 142 is connected ~ way of a link 1~; ta a further
cran~ 146 on the control shaft 129, the cran~ 146 bei~g
disposed externally of the fluid supply cha~ber 124.
As will be appreciated from this Pigure, an increase
in speed of the turbine rotor 111 will cause the member
144 to move to the right as viewed, thereby ~oving the
valve member 127 to the left.
