US3233867A

US3233867A - Turbines

Info

Publication number: US3233867A
Application number: US336000A
Authority: US
Inventors: Ishibashi Eiichi; Kawagoe Katsuhiko
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1963-01-11
Filing date: 1964-01-06
Publication date: 1966-02-08
Anticipated expiration: 1983-02-08
Also published as: CH394252A

Description

INVENTOS SHIDHS//l KHLJHCO( ATTORNEY KnrsuHlKo EUCH:

Feb- 8, 1955 EucHl lsHlBAsHl ETAL TURBINES Filed Jan. 6, 1964 Bw fw@ w67.

United States Patent Office 3,233,367 Patented Feb. 8, 1956 3,233,867 TURBINES Eichi Ishibashi and Katsuhiko Kawagoe, Hitachi-shi,

Japan, assignors to Hitachi, Ltd., Tokyo, Japan, a corporation of Japan Filed Jan. 6, 1964, Ser. No. 336,000 Claims priority, application Japan, Jan. 11, 1963, 258/445 2 Claims. (Cl. 253-69) The present invention relates generally to turbines, and more particularly to an improved construction for nozzles and blades in turbines whereby leakage of the operating medium through axial clearances between the nozzles and blades can be reduced to a minimum.

As is well known, one of the most important problems in manufacturing a high eiiiiciency turbine is to minimize the leakage of the operating medium through passages defined by nozzles, blades and other elements. Especially, a great amount of operating medium leaks in the radial direction from axial clearance between the blades and nozzles which lie in the path of the operating medium. However, a high manufacturing technique is required to minimize the leakage of the operating medium through such axial clearances. Generally, a turbine casing is made of material different from that of a turbine rotor. Therefore, in case of quick starting, stopping or variation in load, the turbine casing will have an axial temperature distribution different from that of the turbine rotor due to the differencev in heat capacities between the two and the attendant dierence in the thermal expansion therebetween will result in variation in the axial clearances between the blades and the nozzles. It has been a general practice in turbine construction to secure the turbine rotor at one end thereof by means of a thrust bearing assembly provided in the turbine casing so that the rotor is allowed to extend towards the other end thereof when subject to thermal expansion.

In such construction, however, the relative difference in elongation between the casing and rotor is successively accumulated at a position remote from the thrust bearing assembly until finally there arises a danger that a portion of the casing remotest from the thrust bearing assembly may abut a corresponding portion of the rotor. Therefore, a successively greater axial clearance is provided between the blade and the nozzle as they are disposed at a point more remote from the thrust bearing assembly so as to avoid possible abutment of the blade with the nozzle. Although such arrangement is effective for the turbine operation as in the case of starting, the efciency of the turbine will be considerably lowered in the normal steady operation due to leakage of the operating medium through such great axial clearances.

The present invention intends to obviate such difficulty encountered by conventional turbines and has for its object to provide an improved structure of a blade and a nozzle whereby leakage of an operating medium through a clearance therebetween can be reduced to a minimum.

According to the invention, there is provided a turbine comprising diaphragms, a nozzle plate included in each of said diaphragms, annular recesses provided on one face of said nozzie plate along the entire circumference radially inside and outside of nozzle openings in said nozzle plate, `blades fixed in rows to a turbine rotor for unitary rotation therewith, and projections provided along the entire inner and outer peripheries on one face of each of said blades, said projections being disposed opposite said recesses so that said projections are axially movable relative to said recesses.

There are other objects and particularities of the invention which will become obvious from the following description with reference to the accompanying drawings, in which:

FIG. l is an enlarged longitudinal sectional view of the struicture of the nozzle portion of a conventional turbine, showing the relation between a nozzle and a blade;

FIG. 2 is an enlarged longitudinal sectional view of the structure of the nozzle portion of a turbine of the invention, showing the relation between a nozzle and a blade in one position;

FIG. 3 is a longitudinal sectional View of part of the turbine of the invention in an assembled state;

FIG. 4 is a longitudinal sectional view similar to FIG. 2, but showing the relation between the nozzle and the blade in another position; and

FIG. 5 is a detail view of th'e bearing block assembly and means for axially shifting the rotor. l

At rst, referring to FIG. l, there is shown the structure of the nozzle portion of a conventional turbine, in which it Will be seen that a minimum clearance of the order of 1 mm. is usually provided between a nozzle and a blade in order to facilitate the assembling and overhauling, and this value is successively made greater for a nozzle and a blade which are disposed at a position remote from a thrust bearing assembly. However, reduction in the predetermined great clearance due to the difference in the thermal expansion between the rotor and the casing is only encountered in an unusual operation such as during starting. Therefore, the great clearances so provided remain unchanged in the normal steady operation, and leakage of an operating medium through the clearances during the normal steady operation will greatly lower the turbine eiliciency. In modern turbines which are higher in capacity and greater in rotor span, loss of efliciency due to leakage of the operating medium through clearances between nozzles and blades will become inevitably greater since a greater clearance must be provided between a nozzle and a blade which are disposed at a position remote from the thrust bearing assembly.

The present invention intends to obviate such diiculty in the prior art structure and to make an eiective proposal for the improved structural relation between a nozzle plate and a blade. According to the invention, annular recesses are formed on a nozzle plate in a diaphragm at portions radially inside and outside of a nozzle opening in the nozzle plate and projections are formed on a shroud ring and the root of a blade at portions corresponding to said recesses in opposed relation thereto so as to minimize leakage of an operating medium therethrough.

Now, a preferred embodiment of the invention will be explained with reference to FIGS. 2-4. FlG. 3 shows a longitudinal sectional view of part of a steam turbine embodying Ehe invention in an assembled state. A rotor 1 is journalled in a thrust bearing assembly 12, while diaphragms 2 are fitte-d fast to a turbine casing 13. Clearances between the diaphragme 2 and the rotor 1 are suitably sealed by labyrinth packings fitted to the inner peripheries of the diaphragms. An operating medium or steam is made to flow into the casing 13 through a portion A and discharged therefrom at a portion B as in a common turbine structure. FIGS. 2 and 4 show enlarged views of a nozzle and blade section or a portion C of FIG. 3 in diierent operative positions. FIG. 2 shows the structure according to the invention, wherein recesses 6 are formed over the entire circumference of a nozzle plate 9 in the diaphragm 2 at portions radially inside and outside o a nozzle opening, said recesses being such that the turbine casing may not be abutted by the rotor under all operating conditions including the starting operation. 0n the other hand, a projection 5 is formed on a shroud ring 4 and a projection 7 is .formed on the root or" a blade 3 at portions corresponding to the radially outer and inner recesses 6 on the nozzle plate 9, respectively, so that during assembling the respective projections 3 and 7 on the blade .3 can be disposed opposite and in closelyadjacent relation to the outer and inner recesses 6 formed on the nozzle plate 9, as shown in FlG. 2. Thus, it will be seen that curved passages in a negative direction with respect to a flow of the operating medium are formed in the gap between the blade 3 and the nozzle plate 9, and the steam flow 8 from the nozzle can pass through the blade 3 in an extremely effective manner, which will bring forth an improvement in the turbine emciency.

The manner of assembling the blade 3 and the nozzle is quite different from that of a conventional case. According to the invention, the diaphragm 2 and the blade 3 art at rst kept in a spaced apart relation as shown in FIG. 4.l Then, a thrust bearing block 10 is displaced in the forward direction by means such as a jack or a screwed-in block 10a (FIG. 5) connected between the block 10 and the lower bearing box 15 to set the blade 3 relative to the diaphragm 2 to the position shown in FIG. 2. In case of overhauling, the thrust bearing block 1li is displaced in the backward direction so that the lade 3 is spaced apart from the diaphragm 2 as shown in FIG. 4, and the casing is lifted while paying attention so that the diaphragm 2 may not contact the blade 3. In the case of assembling, the turbine assembly is properly set by the use of a runner 11 after the entire rotor is displaced to the normal operating position.

lt will be understood from the foregoing description that the invention is highly advantageous in that a merely additional structural feature applied to tlhe structure of the conventional turbine is elective to minimize the loss of efficiency due to leakage of the operating medium through the clearances ybetween the nozzles and the blades.

What is claimed is:

ll. A turbine comprising a rotor, a casing enclosing a plurality of spaced diaphragms and a plurality of turbine blades interdigitated with said diaphragme, a nozzle plate including nozzle openings provided on each of said diaphragms, a pair of concentric annular grooves provided on one corresponding face of each of said nozzle plates along the entire circumference radially inside and outside of said nozzle openings in each nozzle plate, said diaphragms being fixed at one end to said rotor for unitary rotation therewith, a pair of concentric annular projections provided along the entire inner and outer peripheries on one face of each of said blades, said projections being disposed opposite to and in engagement with said grooves in Van adjacent nozzle plate so as to provide a negative ilow path to the operating medium of said turbine, the other face of each of said blade being axially spaced from the opposing face of the adjoining diaphragm at least by a distance equal to the axial overlap between said grooves and said projections whereby the rotor may be axially shifted to disengage said projections from said recesses and thrust bearing means for rotatably supporting said rotor Vin said casing including means for axially shifting said rotor in said casing to effect said disengagement of said projections from said I'CCSSSSS.

2. A turbine comprising a rotor, a casing enclosing a plurality of spaced diaphragms and a plurality of turbine blades interdigitated with said diaphragms, a nozzle plate including nozzle openings provided on each of sai-d diaphragms, a pair of concentric annular grooves provided on one corresponding face of each of said nozzle plate along the entire circumference radially inside and outside of said nozzle openings in each nozzle plate, said diaphragms being xed at one end to said rotor for unitary rotation therewith, a pai-r of concentric annular projections provided along the entire inner and outer peripherics on one face of each of said blades, said projections being disposed opposite to and in engagement with said groves in an adjacent nozzle plate so as to provide a negative flow path to the operating medium of said turbine, the other face of each of said blades being axially spaced from the opposing'face .of the adjoining diaphragm at least by a distance equal to the axial overlap between said grooves and said projections whereby the rotor may be axially shifted to disengage said projections from said recesses and thrust bearing means for rotatably supporting said rotor in said casing including means for axially shifting said rotor in said casing to effect said disengagement of said projections from said recesses,

said means for axially shifting said rotor in said casing including a thrust bearing block axially shiftable between iirst and second positions corresponding to positions of engagement and disengagement of said projections with said grooves.

References Cited by the Examiner UNITED STATES PATENTS 726,032 4/1903 Curtis 253-773 894,409 7/1908 Toms 253-69 X 1,527,910 2/ 1925 Parsons et al. 1,554,052 9/1925 Weidehoff 253-69 X 1,895,003 1/1933 Meyer.

2,411,124 11/1946 Baumann 253-773 3,092,393 6/1963 Morley et al. 253-773 FOREIGN PATENTS 477,373 6/ 1929 Germany.

DONLEY I. STOCKlNG, Primary Examiner.

JOSEPH H. BRANSON, JR., KARL J. ALBRECT,

Examiners.

Claims

1. A TURBINE COMPRISING A ROTOR, A CASING ENCLOSING A PLURALITY OF SPACED DIAPHRAGMS AND PLURALITY OF TURBINE BLADES INTERDIGITATED WITH SAID DIAPHRAGMS, A NOZZLE PLATE INCLUDING NOZZLE OPENINGS PROVIDED ON EACH OF SAID DIAPHRAGMS, A PAIR OF CONCENTRIC ANNULAR GROOVES PROVIDED ON ONE CORRESPONDING FACE OF EACH OF SAID NOZZLE PLATES ALONG THE ENTIRE CIRCUMFERENCE RADIALLY INSIDE AND OUTSIDE OF SAID NOZZLE OPENINGS IN EACH NOZZLE PLATE, SAID DIAPHRAGMS BEING FIXED AT ON END TO SAID ROTOR FOR UNITARY ROTATION THEREWITH, A PAIR OF CONCENTRIC ANNULAR PROJECTIONS PROVIDED ALONG THE ENTIRE INNER AND OUTER PERIPHERIES ON ONE FACE OF EACH OF SAID BLADES, SAID PROJECTIONS BEING DISPOSED OPPOSITEE TO AND IN ENGAGEMENT WITH SAID GROOVES IN AN ADJACENT NOZZLE PLATE SO AS TO PROVIDE A NEGATIVE FLOW PATH TO THE OPERATING MEDIUM OF SAID TURBINE, THE OTHER FACE OF EACH OF SAID BLADE BEING AXIALLY SPACED FROM THE OPPOSING FACE OF THE ADJOINING DIAPHRAGM AT LEAST BY A DISTANCE EQUAL TO THE AXIAL OVERLAP BETWEEN SAID GROOVES AND SAID PROJECTIONS WHEREBY THE ROTOR MAY BE AXIALLY SHIFTED TO DISENGAGE SAID PROJECTIONS FROM SAID RECESSES AND THRUST BEARING MEANS FOR ROTATABLY SUPPORTING SAID ROTOR IN SAID CASING INCLUDING MEANS FOR AXIALLY SHIFTING SAID ROTOR IN SAID CASING TO EFFECT SAID DISENGAGEMENT OF SAID PROJECTIONS FROM SAID RECESSES.