Radial rotary slide valve for controlling the steam flow rate in a steam turbine

A radial rotary slide valve for controlling a steam flow rate in a steam turbine, includes an immobile fixed ring and a rotary ring which is disposed concentrically on the latter in such a way as to be rotatable into an angular position that can be varied through the use of a servo motor. The rotary ring has first control profiles which correspond to corresponding second control profiles belonging to the fixed ring in such a way that control slots situated between the control profiles can be varied for opening or closing. The rotary ring is divided into a top part and a bottom part by a joint in the region of a joint in the casing. In order to optimize the play required for sliding between the fixed ring and the rotary ring, the top part of the rotary ring and the bottom part of the rotary ring can be connected to one another by a suitable connecting device for varying the distance between at least two opposing half-ring ends. This makes it possible to vary an inside diameter of the rotary ring to accommodate the sliding play required for rotary movements between the rotary ring and the fixed ring.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The invention relates to a radial rotary slide valve for controlling a 
steam flow rate in a steam turbine, including an immobile fixed ring and a 
rotary ring disposed concentrically on the latter in such a way as to be 
rotatable into an angular position that can be varied by a servo motor, 
the rotary ring having control profiles corresponding with corresponding 
control profiles of the fixed ring to vary control slots between the 
control profiles for opening and closing, and the rotary ring being 
divided in the region of a joint into a top part and a bottom part. 
In steam turbine construction, almost exclusive use is made of valves which 
are not of the rotary-slide type to control steam bleeds, although in 
comparison rotary slide valves are of relatively simple construction and 
also have a number of other advantages. Problems are posed, however, by 
the sliding conditions under which the rotary ring has to be capable of 
rotary displacement on the fixed ring. Of great significance in that case 
are pressure conditions generated by static pressure forces since they are 
responsible for friction between the components which slide on one 
another. While there is no relief from those problems in the case of axial 
rotary slide valves, there is automatic static relief of the rotary ring, 
situated on the outside, in the case of radial rotary slide valves, due to 
the fact that the static steam forces counteract one another. 
German Published, Non-Prosecuted Patent Application DE 42 14 775 A1, 
corresponding to U.S. application Ser. No. 08/180,106, filed Jan. 12, 
1994, has disclosed an axial rotary slide valve in which the sliding 
friction of the rotary ring is largely replaced by rolling friction with 
the aid of axial needle bearing rings. A corresponding rolling bearing 
configuration is, of course, also possible in the case of radial rotary 
slide valves but is only acceptable if the sliding gap which arises in 
that case is so small that the steam losses due to it remain small. 
However, a very narrow sliding gap is difficult to control, not only 
because manufacturing tolerances are small, but because of the fact that 
it can lead to problems even under normal operating conditions. During 
use, rotary slide valves are subject to the action of temperatures of 
several hundred degrees. Nonuniform thermal expansion in the rotary ring, 
on one hand, and the fixed ring, on the other hand, can give rise to large 
movement-inhibiting forces because the play provided disappears and, as a 
result, actual jamming is produced. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the invention to provide a radial rotary 
slide valve for controlling the steam flow rate in a steam turbine, which 
overcomes the hereinafore-mentioned disadvantages of the heretofore-known 
devices of this general type, in which a width of a sliding gap is 
successfully optimized and a risk of jamming of the system, which is 
extremely risky for turbine operation, is avoided or at least 
significantly reduced. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, a radial rotary slide valve for controlling 
a steam flow rate in a steam turbine, comprising an immobile fixed ring; a 
rotary ring disposed concentrically and rotatably on the fixed ring, the 
rotary ring divided along a joint into a top half-ring part and a bottom 
half-ring part having opposing half-ring ends; a servo motor for varying 
an angular position of the rotary ring; the rotary ring having first 
control profiles and the fixed ring having second control profiles, the 
first and second control profiles defining control slots therebetween and 
the first and second control profiles corresponding with each other for 
variably opening and closing the control slots; and a connecting device 
interconnecting the top and bottom half-ring parts of the rotary ring for 
varying a distance between at least two of the opposing half-ring ends and 
permitting a change in inside diameter of the rotary ring to accommodate a 
sliding play required for rotary movements between the rotary ring and the 
fixed ring. 
Just as the turbine casing is split into a top part and a bottom part by a 
joint, the fixed ring and the rotary ring are fundamentally split in the 
case of a radial rotary slide valve. However, in contrast to conventional 
structures, it is a significant advantage of the structure according to 
the invention that the top part of the rotary ring and the bottom part of 
the rotary ring are not connected rigidly but instead are connected to one 
another by a suitable connecting device in such a way that the distance 
between at least two opposing ends of these two ring halves can be varied. 
This makes it possible to vary the inside diameter of the rotary ring, and 
the sliding play required for rotary movements between the rotary ring and 
the fixed ring can be accommodated. 
In accordance with another feature of the invention, the connecting device 
interacts with at least one spring element which normally holds the two 
parts of the rotary ring firmly together but, under the action of clamping 
forces, automatically makes an enlargement of the sliding play possible. 
In accordance with a further feature of the invention, the use of one 
spring element on each of the two ends of the ring halves to be connected 
to one another can be further simplified by holding two opposing ends of 
the two halves of the rotary ring together through the use of a hinge, so 
that just one spring element is required. 
In accordance with an added feature of the invention, in order to provide 
for the use of the spring element on the two opposing ends of the two 
halves of the rotary ring which are not connected by a hinge, a collared 
bolt is provided for engagement at this location. The collared bolt is 
screwed into a threaded bush belonging to one half of the rotary ring. The 
head of the collared bolt engages on a compression spring which is 
supported on a collar on the other half of the rotary ring. As soon as 
clamping forces occur which are greater than the spring force stemming 
from the compression spring and connecting the two halves of the ring, the 
joint between the two halves of the ring increases in size at this point 
and the sliding friction is reduced. 
Even more reliable opening of the joints in the event of excessive sliding 
friction is achieved if the actuating forces of the servo motor which 
actuates the rotary ring engage directly on the joint. Therefore, in 
accordance with an additional feature of the invention, there is provided 
a coupling lever which establishes the connection with the servo motor and 
ends at a coupling fork having prongs on which respective inward-pointing 
studs are secured, and centrally with respect to the joint, these two 
studs engage in a hole, one half of which is formed in the top part of the 
rotary ring and the other half of which is formed in the bottom part of 
the rotary ring. 
The control profiles determine the nature of the control slots which belong 
to the steam duct and are opened or closed in accordance with the 
direction of actuation of the rotary ring. It is advantageous to give the 
control profiles an aerodynamic shape. In accordance with yet another 
feature of the invention, the fixed ring is assigned the profile heads, 
while the profile ends are situated in the fixed ring. When the control 
slots are fully open, the total profile then comes into effect. 
In accordance with a concomitant feature of the invention, although the 
automatic enlargement of the sliding play is very advantageous, it is also 
possible, as an alternative, to provide a connecting device which can be 
adjusted through the use of corresponding tools, preferably by actuating 
screw-action elements. This would make it possible to optimize the 
required sliding play in each individual case. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
radial rotary slide valve for controlling the steam flow rate in a steam 
turbine, it is nevertheless not intended to be limited to the details 
shown, since various modifications and structural changes may be made 
therein without departing from the spirit of the invention and within the 
scope and range of equivalents of the claims. 
The construction and method of operation of the invention, however, 
together with additional objects and advantages thereof will be best 
understood from the following description of specific embodiments when 
read in connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the figures of the drawings in detail, it is noted that an 
understanding of the configuration to be described below will be 
facilitated if complementary details of FIGS. 1 to 3 are considered 
together. A radial rotary slide valve 1, 2 which is disposed within a 
turbine casing 3 has a fixed ring 1 and an outer, rotary ring 2, which is 
disposed concentrically with respect to the latter. Both the turbine 
casing 3 and the radial rotary slide valve 1, 2 are divided into top and 
bottom parts along a joint 16. 
Steam is controlled through the use of control profiles 4, having profile 
heads 4a which are assigned to the rotary ring 2 and profile ends 4b which 
are assigned to the fixed ring 1. Control slots 17, which are disposed 
between the control profiles, belong to a steam duct 5 and are fully open 
in the illustrations provided. In this angular position of the rotary ring 
2 relative to the fixed ring 1, the profile heads 4a and the profile ends 
4b rest form-lockingly on one another and, by virtue of their 
aerodynamically optimized shape, pose only a relatively low resistance to 
the steam flowing through from a front part 5a of the steam duct to a rear 
part 5b of the steam duct in a steam direction 7. The steam then passes 
from there to rotor blades of a turbine rotor 6. The profile heads 4a can 
be displaced by turning the rotary ring 2 to such an extent relative to 
the profile ends 4b that the control slots 17 are fully closed. The shape 
of the control profiles 4 is then no longer as significant with a reduced 
cross-section of the control slots 17. 
A schematically illustrated servo motor 20 engages on the rotary ring 2 by 
way of a coupling lever 10, to provide for the rotary adjustment of the 
rotary ring 2 relative to the fixed ring 1. For this purpose, an end of 
the coupling lever 10 has a coupling fork 11 with fork prongs 11a, 11b in 
which inward-pointing studs 12 are secured and engage in corresponding 
holes in the rotary ring 2 in the vicinity of the joint 16. In the 
configuration described thus far, a tensile force from the servo motor 20 
would pull the bottom part or half-ring 2b of the rotary ring away from 
the top part or half-ring 2a of the rotary ring, while the conditions 
would be reversed in the case of a compressive force. In both cases, 
however, the inside diameter of the rotary ring 2 and of the sliding gap 
18 at the joint 16 would increase. 
However, an enlargement of the inside diameter should only take place when 
the sliding friction exceeds a predetermined limit value in order to 
reduce this value to an appropriate magnitude in this case. For this 
purpose, a correspondingly dimensioned compression spring 15 is provided 
which is held by a head of a collared bolt 14 and pressed against a collar 
19 at the top part or half-ring 2a of the rotary ring. Since the collared 
bolt 14 is screwed into a threaded bush 13 on the bottom part or half-ring 
2b of the rotary ring, the top part 2a of the rotary ring and the bottom 
part 2b of the rotary ring are held together by the compression spring 15 
with its inherent spring force. The collar 19 and the threaded bush 13 are 
disposed at opposed half-ring ends of the rotary ring 2. It is only if 
friction which exceeds this spring force arises between the rotary ring 2 
and the fixed ring 1 that the sliding gap 18 in the region of the joint 16 
increases in size upon actuation of the coupling lever 10 to such an 
extent that the sliding friction falls and a rotary movement becomes 
possible. A hinge 8 with a hinge shaft 9 holds two opposite ends of the 
two parts or half-rings 2a, 2b of the rotary ring together. Elements 8, 9 
and 11 to 15 together form a connecting device.