GB2076065A - Turbine - Google Patents

Abstract

Nozzles 15, which direct working fluid into the blades 14 of a rotor 11, are divided into a plurality of groups with the nozzles in each group communicating with a respective radial port 25 in a tubular valve seat 21. A cylindrical valve member 27 is movable axially of the valve seat 21 to open or close the ports 25 in succession, thereby achieving nozzle-governed operation of the turbine. The valve seat 21 is removably mounted between a casing cover 13 and a pressure vessel 24 and can be replaced by other valve seats having ports 25 different in shape, size, disposition and/or number, thereby enabling the operating characteristics of the turbine to be altered. <IMAGE>

Description

SPECIFICATION Turbine This invention relates to a turbine.

A turbine typically comprises a rotor, a multiplicity of nozzles through which working fluid is directed into blades of the rotor, a supply chamber and valve means controlling the flow of working fluid from the supply chamber to the nozzles. In turbines of the so-called throttle governed type, the valve means comprises a single valve which controls the flow of fluid to all of the nozzles in unison. In turbines of the socalled nozzle governed type, the valve means is composed of 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 throttle governed turbines have much lower thermodynamic efficiency under partial load operation than nozzle governed turbines. However, nozzle governed turbines 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. Therefore, 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.

It is an object of the present invention to provide 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 fluid to be accommodated in a simple manner. According to the present invention, there is provided a turbine including a rotor, a multiplicity of nozzles through which working fluid is directed into blades of the rotor, the nozzles being divided into a plurality of groups with the nozzles in each group being supplied with the working fluid 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 valve 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 carried out on site. The number of radial ports in the valve seat and their size, shape and disposition will determine the sequence in which the nozzles are brought into or out of operation as the valve means is opened or closed, the manner in which the nozzles are grouped (i.e. the nozzles which are brought into operation at any given position of the valve means), the so-called "swallowing capacity" of the turbine, and the modulation of the working fluid.

Desirably, the supply chamber is removably mounted on a casing within which the rotor is rotatably disposed, and the valve seat is removably mounted between the casing and the supply chamber co-axially with the rotor axis. In an alternative arrangement, however, the valve seat is contained within the supply chamber and the latter is disposed remotely from the rotor casing, with the radial ports in the valve member being connected to the respective nozzle groups by way of external pipes.

The capability 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 closing the open end of the body and containing the nozzles, the conduit means is formed by internal passages within the cover, and the valve seat is received in a cylindrical bore in the cover into which the passages open. In this case, the cover can be replaced by other covers having differentsized bores therein for reception of other correspondingly different-sized valve seats.

Moreover, the various covers can also have different arrangements of the said passages therein: for example, passages of different 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 is 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, hydraulic, 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.

Alternatively, the valve member can be manually operated. In one position of the valve member, it can be arranged that all of 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 stainless steel or nitrided steel.

Advantageously, the nozzles are arranged in at least one ring and are divided into a plurality of arcuate 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 arcuate row are in communication 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 Figure 1 is an axial cross-section of a first embodiment of a turbine according to the present invention; 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 in Figure 1; and Figure 4 is an axial cross-section of a second embodiment of a turbine according to the present invention, 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 10 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 1 5 received within a stepped axial bore 1 6 in the cover 13, the inserts 1 5 being retained in their respective bores 1 6 by an annular clamping ring 1 7 and being sealed against leakage by respective O-rings 1 8. Formed within the cover 13 are arcuate passages 1 9 (indicated by broken lines in Figure 3) from which the bores 1 6 lead. In the illustrated arrangement, eight such passages 1 9 are provided in equi-angularly spaced relation, and the nozzles are divided into eight arcuate rows with the nozzles in each row communicating with a respective one of the arcuate passages 19.A different number of arcuate passages can, however, be provided if desired.

A radial passage 20 extends from each arcuate passage 1 9 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 clamping 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 mounted on the cover 13. Radial 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 1 9.

The flow of working fluid between the supply chamber 24 and the nozzles is controlled by a valve member 27 which is axially movable within the valve seat 21. Both the valve member and the valve seat are made of stainless steel or nitrided steel. The valve member 27 is in the general form of a hollow cylindrical piston, and is operatively connected to a crank 28 on a rotatable control shaft 29 by way of a link 30. The crank 28 and the link 30 are disposed within the chamber 24, whereas the control shaft 29 extends rotatably and sealingly through a side wall of the chamber 24 and is 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 drawings, all of the radial ports 25 are uncovered by the valve member, and therefore pressurised working fluid can pass from the supply chamber 24 through the valve to all of the nozzles so that the turbine operates at full power, i.e. under full load. if the load on the turbine should lessen, the resultant increase in speed of the rotor will be detected by the control mechanism, as a result of which the control shaft 29 is rotated to move the valve member 27 so as to reduce fluid flow through one or more of the radial ports 25 the turbine power is consequently reduced in correspondence to the reduction in ioad.If the load on the turbine then increases, the rotor will momentarily slow down and the control mechanism will move the valve member in the reverse direction to increase the flow of working fluid through the increased area of the radial ports 25 once again.

If the valve member is moved to the extreme left as viewed in Figure 2, it will shut off all of the radial ports 25. Hence, pressurised working fluid will be unable to flow to any of the nozzles, resulting in a shut-down of the turbine. This action can be performed under emergency conditions, for example.

As an alternative to a governor-operated control mechanism, the control shaft 29 can be connected to a simple hand crank or hand wheel so that the above-described power adjustments can be performed manually.

The number, size, shape and disposition of the radial ports 25 and the corresponding grooves 26 in the valve seat 21 determine the amount of working fluid which can flow to each arcuate row of nozzles and the sequential mode in which these rows are placed into and out of communication with the supply chamber 24. These factors can be altered to suit the particular application of the turbine merely by replacing the valve seat 21 with another having suitable characteristics. Moreover, further alteration of the turbine characteristics can be achieved by replacing the supply chamber 24 and the casing cover 1 3. 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 condition of the working fluid.In the latter case, various covers 13 can be provided having a different number of passages 19 and 20, and wherein the mean diameter of arcuate passages 1 9 may be varied. In addition, covers having different-sized central axial bores 20a can be provided for accommodating correspondingly different-sized 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 variable to a large degree in order to cater for various operational requirements of the turbine. Moreover, the radial passages 20 provide unrestricted communication between the arcuate passages 1 9 and radial ports 25 in the valve seat 21 in all cases.

Since the valve member 27 is open at both of its axial ends, it is completely pressure balanced and its cut-off action can be modulated to minimise resistive 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.

The turbine illustrated in Figure 4 is generally similar to that described above with reference to Figures 1 to 3, and therefore similar parts have been accorded the same reference numerals with 100 added. Reference numerals 140 and 141 denote respectively an inlet and an outlet for the passage of working fluid through the turbine. In Figure 4, the governor-operated control mechanism which controls movement of the valve member 127 is shown in detail, and comprises generally a mechanical governor 142 which is rotated with the turbine rotor 111 by way of gearing 143. An axially movable member 144 of the governor 142 is connected by way of a link 145 to a further crank 146 on the control shaft 129, the crank 146 being disposed externally of the fluid supply chamber 124. As will be appreciated from this Figure, an increase in speed of the turbine rotor 111 will cause the member 1 44 to move to the right as viewed, thereby moving the valve member 127 to the left.

Claims (9)

1. A turbine including a rotor, a multiplicity of nozzles through which working fluid is directed into blades of the rotor, the nozzles being divided into a plurality of groups with the nozzles in each group being supplied with the working fluid 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 valve seat being removably mounted in the turbine and being replaceable by other valve seats having radial ports different in shape, size and disposition and/or number.

2. A turbine as claimed in claim 1, wherein the supply chamber is removably mounted on a casing within which the rotor is rotatably disposed, and the valve seat is removably mounted between the casing and the supply chamber co-axially with the rotor axis.

3. A turbine as claimed in claim 2, wherein the casing comprises an open-ended body part within which the rotor is rotatably mounted and a cover removably closing the open end of the body part and containing the nozzles, the conduit means is formed by internal passages within the cover, and the valve seat is received in a cylindrical bore in the cover into which the passages open, the cover being replaceable by other covers having differentsized bores therein for the reception of other correspondingly different-sized valve seats.

4. A turbine as claimed in claim 1, 2 or 3, wherein the radial ports are spaced apart axially of the valve seat, and the valve member is movable axially of the latter.

5. A turbine as claimed in claim 4, wherein the valve member comprises a hollow tubular body whose peripheral wall covers the radial ports successively as the valve member is moved axially of the valve seat, the valve member being open at both axial ends thereof.

6. A turbine as claimed in claim 4 or 5, wherein the valve member is moved relative to the valve seat by means of a rotatable shaft, a crank mounted on the shaft for rotation therewith and a linkage connecting the crank to the valve member, the crank and the linkage being contained within the supply chamber with the shaft extending rotatably and sealingly through a side wall thereof.

7. A turbine as claimed in any preceding claim, wherein the nozzles are arranged in at least one ring and are divided into a plurality of arcuate 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.

8. A turbine as claimed in claim 7, wherein the nozzles in each arcuate row are in communication with a respective arcuate passage with which the respective radial port in the valve seat also communicates.

9. A turbine as claimed in any preceding claim, wherein in one position of the valve member all of the radial ports are closed off.

1 0. A turbine substantially as hereinbefore described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.