Title:
TURBINE VALVE CHEST AND NOZZLE PLATE CONSTRUCTION
United States Patent 3758229
Abstract:
A small steam turbine with a separate external bolted-on valve chest is arranged to support an internally mounted nozzle box with an adjustable nozzle plate. The valve chest, nozzle box and nozzle plate are manufactured as a sub-assembly and attached to the turbine casing as a separate unit. The nozzle plate can subsequently be adjusted for concentric alignment with the first-stage turbine buckets to compensate for accumulated dimensional variations due to manufacturing tolerances. BACKGROUND OF THE INVENTION This invention relates generally to an improved construction for small steam turbines of the type having external valve chests separately attached to the upper halves of the turbine casings and utilizing a multiplicity of steam control valves arranged for sequencial opening, and more particularly relates to more economical constructions of such turbines. In the past, the "nozzle plate," an arcuate member with an arcuate row of ports which admit steam from the stationary part of such a turbine to the rotating turbine buckets, has been attached to or located with respect to the turbine casing. Therefore, since the rotating turbine buckets are also carried on a rotor mounted within the casing, alignment between these two elements which are mounted on a common member was fairly simple. However, this approach required accurate machining of the casing which did not lend itself to economical mass production of the smaller types of steam turbines. Another disadvantage of prior art constructions where the passages supplying the nozzle plate were integral with the turbine casing was that large parts of the casing were exposed to inlet steam conditions and had to be made of alloys which could withstand these conditions. It is, of course, known in the art to provide a separate valve chest containing sequentially actuated control valves admitting steam through valve seats to the individual turbine nozzle arcs. In some cases, the valve chest is manufactured as an integral unit with the nozzle box and this sub-assembly is bolted or otherwise attached to the turbine casing. The nozzle box does not need to be accurately aligned with the inlet to the nozzle plate. However, the outlets from the nozzle plate, do need to be accurately aligned with respect to the rotating buckets, and hence, the nozzle plate is generally supported from the casing itself at accurately determined locations. Previously known methods for doing this have been confined to machines requiring smaller nozzle arcs. It has been previously suggested, as exemplified in U.S. Pat. No. 1,118,352 to Junggren, to support an arcuate nozzle plate of T-shaped cross section by means of two arcuate bolted-on segments. However, these members are not adjustable and are disposed in machined grooves closely located with respect to the turbine casing. Accordingly, one object of the present invention is to provide a more economical construction in steam turbines with a separately attached valve chest accurately locating the nozzle ports with respect to the turbine buckets. Another object of the invention is to provide an improved construction for a valve chest, nozzle box and nozzle plate sub-assembly which provides for adjustment due to accumulated dimensional tolerances. SUMMARY OF THE INVENTION Briefly stated, the invention comprises a turbine casing carrying a rotor with turbine buckets mounted thereon, a valve chest mounted on the turbine casing, a nozzle box mounted on the valve chest, and a nozzle plate adjustably mounted with respect to the nozzle box.
US Patent References:
/1118352.html
Junggren - November 1914 - 1118352
Nozzle box
Sachs et al. - August 1958 - 2848191
Standpipe connection for centrifugal pumps
Geer et al. - May 1964 - 3131642
/1118352.html
Junggren - November 1914 - 1118352
Nozzle box
Sachs et al. - August 1958 - 2848191
Standpipe connection for centrifugal pumps
Geer et al. - May 1964 - 3131642
Inventors:
Price, Philip N. (Leominster, MA)
Hoffman, Herbert N. (Lunenburg, MA)
Hoffman, Herbert N. (Lunenburg, MA)
Application Number:
05/200305
Publication Date:
09/11/1973
Filing Date:
11/19/1971
View Patent Images:
Export Citation:
Assignee:
General Electric Company (Schenectady, NY)
Primary Class:
Other Classes:
415/209.400, 415/185, 415/209.200
International Classes:
F01D9/04; F03B1/04
Field of Search:
415/217-219,201
Primary Examiner:
Husar C. J.
Claims:
What is claimed is
1. In a steam turbine having a casing with a rotor carrying a circumferential row of axial flow turbine buckets, the improvement comprising:
2. The combination according to claim 1, wherein said nozzle plate includes outer and inner arcuate flanges having enlarged holes therein, and wherein said fastening means comprises at least one arcuate ring segment disposed over one of said flanges together with bolts clamping the flange between the ring segment and the nozzle box,the bolt shanks providing substantial clearance inside said enlarged holes to provide for adjustment of the nozzle plate.
3. The combination according to claim 2, and further including dowel means joining said ring segment and said flange for accurately locating the nozzle plate after final adjustment.
4. In a steam turbine having a casing with a rotor carrying a circumferential row of axial flow turbine buckets, the improvement comprising:
1. In a steam turbine having a casing with a rotor carrying a circumferential row of axial flow turbine buckets, the improvement comprising:
2. The combination according to claim 1, wherein said nozzle plate includes outer and inner arcuate flanges having enlarged holes therein, and wherein said fastening means comprises at least one arcuate ring segment disposed over one of said flanges together with bolts clamping the flange between the ring segment and the nozzle box,the bolt shanks providing substantial clearance inside said enlarged holes to provide for adjustment of the nozzle plate.
3. The combination according to claim 2, and further including dowel means joining said ring segment and said flange for accurately locating the nozzle plate after final adjustment.
4. In a steam turbine having a casing with a rotor carrying a circumferential row of axial flow turbine buckets, the improvement comprising:
Description:
DRAWING
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding of the specification. The invention, however, both as to organization and method of practice, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which:
FIG. 1 is an elevation drawing, partly in section, of the inlet portion of a steam turbine;
FIG. 2 is an enlarged cross-sectional view of the adjustable nozzle plate and nozzle box attachment; and
FIG. 3 is an end view of the nozzle plate and attaching means shown in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 of the drawing, portions are shown of the inlet portion of a turbine casing 1 in which is disposed a rotor having turbine wheels with buckets mounted thereon, the first-stage wheel being indicated at 2 and buckets at 2a. The rest of the turbine casing (not shown) is of conventional construction and the details are not material to the present invention.
Mounted on top of casing 1 is a separately attached valve chest 3 likewise of conventional construction and held in place by a ring of bolts 4. Valve chest 3 is typically elongated and is shown here in end view,there conventionally being a row of control valves 5 actuated in sequence by a lift bar and control mechanism not pertinent to the present invention.
In accordance with the present invention, the valve chest 3 has an extending ledge 6 on its underside to which is attached a separate nozzle box or nozzle chest 7 by means of a ring of internal bolts 8. The nozzle box 7 contains at its uppper end a row of valve seats 9 leading to a plurality of separate passages 10 in a conventional manner.
Attached to the face of nozzle box 7, so as to cover the outlet from each passage 10, is an arcuate nozzle plate 11 which is adjustable with respect to nozzle box 7 in a manner to be described in detail. Plate 11 is machined to provide a number of slanted nozzle passages 12 in conventional manner which supply steam to the turbine buckets 2a on wheel 2.
Referring to FIG. 2 of the drawing, the nozzle plate 11 is seen to be of T-shaped cross section with upper and lower flanges 13, 14, respectively. Outer and inner arcuate ring segments 15, 16 serve to clamp the respective flanges 13, 14 to the nozzle box by means of bolts 17. Top and bottom flanges 13, 14 are provided with oversized holes 18 accommodating the shanks 17a of bolts 17 so that the nozzle plate 11 can be slid to the desired position on the face of nozzle box 7 before clamping in place. Dowel pins 19 drilled after final assembly and alignment then locate the nozzle plate 11 with respect to the inner ring segment 16.
Reference to FIG. 3 of the drawing showing an end view illustrates the location of the bolts 17 on the inner and outer ring segments 15, 16. Also, the locations of the two locating dowels 19 are indicated. Reference to the right-hand side of FIG. 3 shows how the generous clearance of holes 18 in the nozzle plate flanges around the bolt shanks 17a will permit sliding the nozzle plate to the final desired location. As indicated on the left-hand side of FIG. 3, the inner ring segment 16 is located with respect to the nozzle box by bolts 17 and the final assembly placement of dowels 19 then locates the nozzle plate 11 with respect to the inner segment.
OPERATION OF THE INVENTION
Operation of the invention will be made more clear by reference first to FIG. 1. The first source of possible variation due to manufacturing tolerances is the juncture of casing 1 with valve chest 3. The next source of possible variance is at the juncture of valve chest 3 with nozzle box 7. A third source of variance is due to variation of the rotor location with respect to the casing and variations in manufacture of turbine wheel 2 which ultimately affects the location of turbine buckets 2a. Thus, an accumulation of otherwise acceptable manufacturing tolerances for each separate piece could place the nozzle ports 12 substantially out of alignment with turbine buckets 2a. These accumulated tolerances are compensated for by movement of the nozzle plate 11 by means of the adjustable fastening arrangement indicated in FIGS. 2 and 3. Therefore, using the present invention, the various units such as the valve chest 3, nozzle box 7, and nozzle plate 11 may be manufactured from the most economical alloys which meet the service requirements for each separate part. Then they may be preassembled as a sub-assembly and attached to the turbine at a subsequent time, all of the foregoing leading to reduced cost of manufacture.
While there has been described what is considered to be the preferred embodiment of the invention, other modifications may occur to those skilled in the art and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding of the specification. The invention, however, both as to organization and method of practice, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which:
FIG. 1 is an elevation drawing, partly in section, of the inlet portion of a steam turbine;
FIG. 2 is an enlarged cross-sectional view of the adjustable nozzle plate and nozzle box attachment; and
FIG. 3 is an end view of the nozzle plate and attaching means shown in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 of the drawing, portions are shown of the inlet portion of a turbine casing 1 in which is disposed a rotor having turbine wheels with buckets mounted thereon, the first-stage wheel being indicated at 2 and buckets at 2a. The rest of the turbine casing (not shown) is of conventional construction and the details are not material to the present invention.
Mounted on top of casing 1 is a separately attached valve chest 3 likewise of conventional construction and held in place by a ring of bolts 4. Valve chest 3 is typically elongated and is shown here in end view,there conventionally being a row of control valves 5 actuated in sequence by a lift bar and control mechanism not pertinent to the present invention.
In accordance with the present invention, the valve chest 3 has an extending ledge 6 on its underside to which is attached a separate nozzle box or nozzle chest 7 by means of a ring of internal bolts 8. The nozzle box 7 contains at its uppper end a row of valve seats 9 leading to a plurality of separate passages 10 in a conventional manner.
Attached to the face of nozzle box 7, so as to cover the outlet from each passage 10, is an arcuate nozzle plate 11 which is adjustable with respect to nozzle box 7 in a manner to be described in detail. Plate 11 is machined to provide a number of slanted nozzle passages 12 in conventional manner which supply steam to the turbine buckets 2a on wheel 2.
Referring to FIG. 2 of the drawing, the nozzle plate 11 is seen to be of T-shaped cross section with upper and lower flanges 13, 14, respectively. Outer and inner arcuate ring segments 15, 16 serve to clamp the respective flanges 13, 14 to the nozzle box by means of bolts 17. Top and bottom flanges 13, 14 are provided with oversized holes 18 accommodating the shanks 17a of bolts 17 so that the nozzle plate 11 can be slid to the desired position on the face of nozzle box 7 before clamping in place. Dowel pins 19 drilled after final assembly and alignment then locate the nozzle plate 11 with respect to the inner ring segment 16.
Reference to FIG. 3 of the drawing showing an end view illustrates the location of the bolts 17 on the inner and outer ring segments 15, 16. Also, the locations of the two locating dowels 19 are indicated. Reference to the right-hand side of FIG. 3 shows how the generous clearance of holes 18 in the nozzle plate flanges around the bolt shanks 17a will permit sliding the nozzle plate to the final desired location. As indicated on the left-hand side of FIG. 3, the inner ring segment 16 is located with respect to the nozzle box by bolts 17 and the final assembly placement of dowels 19 then locates the nozzle plate 11 with respect to the inner segment.
OPERATION OF THE INVENTION
Operation of the invention will be made more clear by reference first to FIG. 1. The first source of possible variation due to manufacturing tolerances is the juncture of casing 1 with valve chest 3. The next source of possible variance is at the juncture of valve chest 3 with nozzle box 7. A third source of variance is due to variation of the rotor location with respect to the casing and variations in manufacture of turbine wheel 2 which ultimately affects the location of turbine buckets 2a. Thus, an accumulation of otherwise acceptable manufacturing tolerances for each separate piece could place the nozzle ports 12 substantially out of alignment with turbine buckets 2a. These accumulated tolerances are compensated for by movement of the nozzle plate 11 by means of the adjustable fastening arrangement indicated in FIGS. 2 and 3. Therefore, using the present invention, the various units such as the valve chest 3, nozzle box 7, and nozzle plate 11 may be manufactured from the most economical alloys which meet the service requirements for each separate part. Then they may be preassembled as a sub-assembly and attached to the turbine at a subsequent time, all of the foregoing leading to reduced cost of manufacture.
While there has been described what is considered to be the preferred embodiment of the invention, other modifications may occur to those skilled in the art and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.