Steam turbine jointed stationary blade

Abstract: Two stage jointed stationary blade of high pressure or intermediate pressure steam turbine is made by bolt joint in place of weld joint so as to make detachment and disassembling possible thereby to facilitate maintenance and inspection work and to reduce assembling man-hour. Stationary blade (front stage)(2), outer ring front portion (1) and inner ring front portion (3) are welded into integral structure. Stationary blade (rear stage) 22, outer ring rear portion (21) and inner ring rear portion (23) are welded into integral structure. The outer ring front portion 1, outer ring center portion 10 and the outer ring rear portion 21 are mutually engaged via engaging portions (4, 11) and (12, 24) with precise positioning and then jointed together integrally by bolt (30). Two stage jointed stationary blade so made is engaged with moving blades (33, 35), labyrinth seals (32, 34) are fitted to seal fitting portions (6, 26) and seal fins (31, 34) are fitted in seal fin grooves (13, 27).

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to a jointed stationary blade of steam turbine according to the preamble portion of claim 1 and more particularly to a two stage jointed stationary blade, applied to a high pressure or intermediate pressure steam turbine, in which an outer ring for jointing a front stage stationary blade and a rear stage stationary blade together fixedly is made in a bolt joint structure so as to be detached and disassembled easily thereby to have a reduced assembling man-hour and an enhanced maintainability. Description of the Prior Art In a high pressure or intermediate pressure steam turbine, trials are being done to use a two stage jointed stationary blade in which mutually adjacent front stage and rear stage stationary blades are jointed together fixedly. Fig. 4 is a cross sectional view of such a two stage jointed stationary blade after it is assembled and Fig. 5 is a cross sectional view of two stationary blade structural portions before they are assembled, wherein Fig. 5(a) shows a stationary blade (front stage) portion and Fig. 5(b) shows a stationary blade (rear stage) portion. In the prior art two stage jointed stationary blade shown in Fig. 5, a stationary blade (front stage) 42 on an upstream side of steam flow S is made in an integral structure fitted with an outer ring front portion 41 and an inner ring front portion 43 fixedly by welding. A stationary blade (rear stage) 52 is also made in an integral structure fitted with an outer ring rear portion 51 and an inner ring rear portion 53 fixedly by welding. These integrally made stationary blades 42, 52 are jointed together fixedly by electron beam welding at a position, shown by numeral 70 (Fig. 4), of the outer ring front portion 41 and the outer ring rear portion 51, so that the two stage jointed stationary blade of an integral structure is constructed. It is to be noted that there are worked seal fitting portions 44, 54 for fitting thereto labyrinth seals in the inner ring front portion 43 and the inner ring rear portion 53, respectively, as well as there are worked seal fin grooves 55, 56 in the outer ring rear portion 51, as described later. In the integral structure of the stationary blade (front stage) 42 shown in Fig. 5(a), the outer ring front portion 41 is fitted to an outer side of the blade via welded portions 45, 46 and the inner ring front portion 43 is fitted to an inner side of the blade via welded portions 47, 48, and the seal fitting portion 44 for fitting thereto a labyrinth seal is worked in the inner ring front portion 43. In the integral structure of the stationary blade (rear stage) 52 shown in Fig. 5(b), the outer ring rear portion 51 consists of portions 51a, 51b, 51c, wherein the portions 51a, 51b are jointed together via welded portions 58, 59 and the portions 51b, 51c are jointed together via welded portions 56, 57, and the outer ring rear portion 51 so constructed is fitted to an outer side of the blade via welded portions 57, 59. Also, the inner ring rear portion 53 is fitted to an inner side of the blade via welded portions 60, 61. The seal fitting portion 54 for fitting thereto a labyrinth seal is worked in the inner ring rear portion 53. Furthermore, the seal fin grooves 55, 56 are worked in the outer ring rear portion 51. Thus, the respective integral structures of the stationary blade (front stage) 42 and the stationary blade (rear stage) 52 are jointed together by electron beam welding at the position 70, as shown in Fig. 4, thereby the two stage jointed stationary blade is constructed. In the prior art two stage jointed stationary blade as mentioned above, the respective integral structures of the outer ring, the stationary blade and the inner ring are made by TIG (tungsten inert gas) welding or MAG (metal active gas) welding and the front stage and rear stage structural bodies thereof are jointed together by electron beam welding at the position of the outer ring front portion and rear portion, thereby the two stage jointed stationary blade is made in the integral structure. Therefore, the front stage and rear stage portions thereof cannot be separated from each other for a repair or inspection work, which results in making the work difficult. Also, the welding work itself requires a lot of man-hour, especially the jointing of the outer ring front portion 41 and the outer ring rear portion 51 requires a welding around an entire periphery of the outer ring, thus there is a problem that large facilities of jigs, tools, etc. for the welding are needed and the man-hour is also increased. A prior art steam turbine jointed stationary blade structure with the features of the preamble portion of claim 1 is known from DE 195 27 662 C1. SUMMARY OF THE INVENTION In view of the problem in the prior art, therefore, it is an object of the present invention to provide an improved steam turbine jointed stationary blade in which an outer ring front portion and an outer ring rear portion are jointed together in a bolt joint structure in place of the weld structure in the prior art so as to be able to facilitate a repair or inspection work and to reduce man-hour of an assembling work. In order to achieve the mentioned object, the present invention provides a steam turbine jointed stationary blade structure as defined by claim 1. In the jointed stationary blade of the present invention, the front stage and rear stage stationary blade structural bodies, each being made integrally, are jointed together by the bolt, thereby detachment and disassembling thereof become possible and maintenance and inspection thereof can be done easily. In the prior art jointed stationary blade, the front stage and rear stage stationary blade structural bodies are jointed together by electron beam welding to be integrated fixedly, which results in a difficulty in the detachment and disassembling to require a difficult work of maintenance and inspection and, furthermore, the electron beam welding being needed to be done around the entire periphery of the outer ring, large facilities of jigs, tools, etc. are needed and man-hour therefor also is increased, but in the present invention, jointing work of the bolt only is needed and assembling man-hour can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross sectional view of a steam turbine jointed stationary blade of an embodiment according to the present invention. Fig. 2 is a partial front view seen from plane X-X of Fig. 1. Fig. 3 is a cross sectional view of three stationary blade structural portions before they are assembled, wherein Fig. 3(a) shows a stationary blade (front stage) portion, Fig. 3(b) shows an outer ring center portion and Fig. 3(c) shows a stationary blade (rear stage) portion. Fig. 4 is a cross sectional view of a steam turbine jointed stationary blade in the prior art, as assembled. Fig. 5 is a cross sectional view of two stationary blade structural portions before they are assembled, wherein Fig. 5(a) shows a stationary blade (front stage) portion and Fig. 5(b) shows a stationary blade (rear stage) portion. DESCRIPTION OF THE PREFERRED EMBODIMENT Herebelow, an embodiment according to the present invention will be described concretely with reference to figures. Fig. 1 is a cross sectional view of a steam turbine jointed stationary blade of an embodiment according to the present invention. Fig. 2 is a partial front view seen from plane X-X of Fig. 1 and Fig. 3 is a cross sectional view of three stationary blade structural portions before they are assembled, wherein Fig. 3(a) shows a stationary blade (front stage) portion, Fig. 3(b) shows an outer ring center portion and Fig. 3(c) shows a stationary blade (rear stage) portion. In Fig. 3(a), like in the prior art case, an outer ring front portion 1 is jointed to an outer side of a stationary blade (front stage) 2 and an inner ring front portion 3 is jointed to an inner side of the stationary blade (front stage) 2, so that an integral structure of the stationary blade (front stage) 2 is constructed. A seal fitting portion 6 for fitting thereto a labyrinth seal is worked in the inner ring front portion 3. A bolt hole 5 as a hole for a bolt head portion is worked in the outer ring front portion 1 to pass therethrough. In a right, or rear, end top portion of the outer ring front portion 1, an engaging portion 4 is worked in a stepped form for joint engagement with an end portion of an outer ring center portion 10 to be described next. In Fig. 3(b), the outer ring center portion 10 has engaging portions 11, 12 worked in both end portions thereof, wherein the engaging portion 11 is for engagement with the engaging portion 4 of the outer ring front portion 1 and the engaging portion 12 is for engagement with an end portion of an outer ring rear portion 21 to be described below. A bolt hole 14 is provided in the outer ring center portion 10 to pass therethrough so as to communicate with the bolt hole 5 of the outer ring front portion 1. Further, there are provided seal fin grooves 13 in the outer ring center portion 10. In Fig. 3(c), an integral structure of a stationary blade (rear stage) 22 is shown, wherein an outer ring rear portion 21 is jointed to an outer side of the stationary blade (rear stage) 22 by welding and an inner ring rear portion 23 is also jointed to an inner side of the stationary blade (rear stage) 22 by welding, like in the prior art case. An engaging portion 24 is provided in a left, or front, end portion of the outer ring rear portion 21 for engagement with the engaging portion 12 of the outer ring center portion 10 and a bolt hole 25 as a hole for a bolt end portion is worked in the outer ring rear portion so as to communicate with the bolt hole 14 of the outer ring center portion 10. A seal fitting portion 26 for fitting thereto a labyrinth seal is worked in the inner ring rear portion 23 and also there are worked seal fin grooves 27 in an inner periphery of a right, or rear, portion of the outer ring rear portion 21. In Fig. 1, a cross section of a steam turbine two stage jointed stationary blade is shown, wherein each of the separated blade portions shown in Fig. 3 is jointed together to form an integral structure of the steam turbine jointed blade. In Fig. 1, the outer ring front portion 1, the outer ring center portion 10 and the outer ring rear portion 21 are engaged with each other via two engagement portions, one being of the engaging portions 4, 11 and the other being of the engaging portions 12, 24, so that positioning of the bolt holes 5, 14, 25 is ensured easily. In this state, a jointing bolt 30 is inserted to be screwed into the bolt holes 5, 14, 25, thereby the portions 1, 10, 21 of the outer ring are fastened together strongly to be integrated into one unit. In Fig. 2, which is a partial front view seen from plane X-X of Fig. 1, the outer ring front portion 1 is made in an annular form and a plurality of jointing bolts 30 are provided along the annular form for fastening the outer ring front portion 1, the outer ring center portion 10 and the outer ring rear portion 21 together strongly as mentioned above. It is to be noted that in the example illustrated in Fig. 2, an interval between each of the jointing bolts 30 is so selected that a central angle of the outer ring made by said interval is set to 14 degrees (not shown), but arrangement of the jointing bolts 30 is not limited thereto. In the two stage jointed stationary blade having the jointing bolt 30 as shown in Fig. 1, the stationary blade (front stage) 2, a moving blade 33, the stationary blade (rear stage) 22 and a moving blade 35 are arranged sequentially in a direction of steam flow S, and a labyrinth seal 32 is fitted to the seal fitting portion 6 of the inner ring front portion 3 as well as a labyrinth seal 34 is fitted to the seal fitting portion 26 of the inner ring rear portion 23, thus a seal portion for sealing a rotor disc side is formed. Further, seal fins 31 are fitted in the seal fin grooves 13 of the outer ring center portion 10 to form a seal portion for sealing a tip end portion of the moving blade 33 and seal fins 34 are fitted in the seal fin grooves 27 of the outer ring rear portion 21 to form a seal portion for sealing a tip end portion of the moving blade 33. According to the jointed stationary blade of the present embodiment as described above, the outer ring is divided into the front portion 1, the center portion 10 and the rear portion 21; the outer ring front portion 1, the stationary blade (front stage) 2 and the inner ring front portion 3 are jointed together by welding to form an integral structure; the outer ring rear portion 21, the stationary blade (rear stage) 22 and the inner ring rear portion 23 are also jointed together by welding to form an integral structure; and these outer ring front portion 1, center portion 10 and rear portion 21 are fastened together strongly by the jointing bolt 30, thereby as compared with the prior art two stage jointed stationary blade made integrally by welding, detachment and disassembling become possible, maintenance becomes facilitated and assembling man-hour can be reduced.

Claims: A steam turbine jointed stationary blade structure comprising: a front stage stationary blade structural body and a rear stage stationary blade structural body, wherein said front and rear stage stationary blade structural bodies are each composed of an outer ring (1,21) integrally joined with radially outer sides of stationary blades (2,22) by welding and an inner ring (3,23) integrally joined with radially inner sides of said stationary blades (2,22) by welding, wherein said front and rear stage stationary blade structural bodies are jointed together at their respective outer rings (1,21) by bolts (30), and wherein an outer center ring (10) is positioned between the outer rings (1,21) of said front and rear stage stationary blade structural bodies and said bolts (30) extend through said outer center ring (10), characterized in that said outer and inner rings (1,21;3,23) are joined with said stationary blades (2,22) by welding, and said outer center ring (10) is additionally connected with the outer rings (1,21) of said front and rear stage stationary blade structural bodies via engaging portions (4,11;12,24) worked in a stepped form. The steam turbine jointed stationary blade structure of claim 1, wherein said outer center ring (10) is provided with seal fin grooves (13) for forming a seal portion in cooperation with seal fins (31) provided at a tip end portion of a moving blade (33) placed between said front stage stationary blade structural body and said rear stage stationary blade structural body when mounted in a steam turbine.

Inventors: KONISHI TETSU, KUWANA TOYOKAZU, MAGOSHI RYOTARO, MATSUO ASAHARU, TANAKA KEIZO, TODA HIDEYUKI, KONISHI, TETSU, KUWANA, TOYOKAZU, MAGOSHI,RYOTARO, TANAKA, KEIZO, TODA, HIDEYUKI, Konishi, Tetsu, c/o Mitsubishi Heavy Ind. Ltd., Kuwana, Toyokazu, c/o Mitsubishi Heavy Ind. Ltd., Magoshi,Ryotaro, c/o Mitsubishi Heavy Ind. Ltd., Matsuo Asaharu, c/o Mitsubishi Heavy Ind. Ltd., Tanaka, Keizo, c/o Mitsubishi Heavy Ind. Ltd., Toda, Hideyuki, c/o Mitsubishi Heavy Ind. Ltd.
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI HEAVY INDUSTRIES, LTD.
Application year: 1999
Main classification: F01D25
IPC codes: F01D25, F01D9