Apparatus and method of correcting deformation of gas turbine blade

An apparatus for correcting deformation of a gas turbine blade includes a stationary die fixed to a backside of a tip shroud of a gas turbine blade to hold a back surface thereof and a pressing die pressing a front surface of the tip shroud so as to press the tip shroud of the blade between the pressing die and the stationary. A hydraulic drive mechanism including pressure generator is arranged for pressing the pressing die against the tip shroud held by the stationary die and a control device is operatively connected to the hydraulic drive mechanism so as to set and indicate a driving condition on a basis of deformation correction data preliminarily stored in the control device.

BACKGROUND OF THE INVENTION

1. Industrial Field of the Invention

The present invention relates to apparatus for and method of correcting deformation of a gas turbine blade, capable of correcting or adjusting the deformation of a tip shroud of the gas turbine blade used for a generator by using a press.

2. Related Art

Gas turbine blades for generators are used under severe conditions, and for this reason, the material of the gas turbine blades deteriorates and deforms during a long time operation. Since the gas turbine blade is made of expensive heat resisting alloy, it is desirable in an economical viewpoint to repair and reuse deteriorated or deformed gas turbine blade as much as possible without discarding or newly manufacturing the blade. Regeneration by an HIP (Hot Isostatic Pressing) material reproduction treatment has been tried with respect to the material deterioration, and some extent of effect has been obtained.

On the other hand, without carrying out the correction to the deformation, the arrangement of circumferentially arranged gas turbine blades are changed so that adjustment is made to prevent the contact area of a tip shroud of adjacent gas turbine blades from becoming too small.

The deterioration of the material can be regenerated in some extent by employing the HIP material regeneration treatment. However, as the HIP material regeneration treatment utilizes an isotropic pressing technology by using gas, it is impossible to correct the deformation. Then, the arrangement of gas turbine blades is adjusted in consideration that the contact area of the tip shroud of the adjacent gas turbine blades does not become too small. Therefore, much time and cost are taken to adjust the arrangement, and even if the contact area is secured by the adjustment, it is difficult to entirely adjust the balance of gas turbine blades. In addition, there is the case where the contact area is not secured even if these gas turbine blades are suitably arranged as much as possible. In such a case, an expensive and new gas turbine blade must be applied to the portion difficult to adjust.

In the known art concerning such turbine blade deformation correction, at the time of manufacturing steam turbine blade or gas turbine blade through casting process, the correction of “twist distortion (strain)” or “bent distortion (strain)” caused particularly to an effective portion (i.e., portion at which steam or combustion gas as operation gas flows) of the blade has been performed by fixing the blade itself to a large-scale press and pressing thereby the blade (effective portion) from front and rear sides thereof. (For example, refer to Japanese Patent Laid-open No. HEI 6-262262 and No. HEI 8-276216).

However, in such prior art, the correction is mainly made to correct or adjust the distortion of the blade at newly manufacturing process or distortion only to the blade effective portion, and accordingly, it was difficult to apply such correction technology to the deformation of the blade tip shroud.

SUMMARY OF THE INVENTION

An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide apparatus for and method of simply and easily correcting a deformation of a tip shroud of a gas turbine blade.

This and other objects can be achieved according to the present invention by providing, in one aspect, an apparatus for correcting deformation of a gas turbine blade comprising:

a stationary die fixed to a backside of a tip shroud of a gas turbine blade to hold a back surface thereof when deformation of the tip shroud of a gas turbine blade is corrected;

a pressing die pressing a front surface of the tip shroud so as to press the tip shroud of the blade between the pressing die and the stationary die;

a supporting mechanism for supporting the stationary die with respect to the pressing die;

a hydraulic drive mechanism connected to the pressing die and including pressure generator for pressing the pressing die against the tip shroud held by the stationary die; and

a control device operatively connected to the hydraulic drive mechanism and adapted to set and indicate a driving condition of the hydraulic drive mechanism on a basis of deformation correction data preliminarily stored in the control device.

In the deformation correction (correcting) apparatus for gas turbine blade of this aspect, when the deformation of the tip shroud of a gas turbine blade is corrected, the pressing die presses the surface of the tip shroud against the stationary die, and then, the tip shroud is pressed between the stationary die and the pressing die under the control of the pressure and displacement of the pressure applying device according to a predetermined data or like to thereby correct the deformation.

In a preferred embodiment, the surface of the stationary die contacting the tip shroud of the blade has a shape subtracting a return amount from the shape of the tip shroud after the correction of the deformation, and on the other hand, the surface of the pressing die contacting the tip shroud has a shape adding a return amount to the shape of the tip shroud after the correction of the deformation.

Furthermore, the preliminarily stored data includes data of pressure and displacement to be outputted to the pressure generator of the hydraulic drive mechanism, the control device includes a pressure operating element and a displacement operating element, and the return amounts are operated and set by the pressure operating element and the displacement operating element based on a predetermined data with a position of the pressing die contacting the deformed portion of the tip shroud being a reference position.

According to this embodiment, the surface of the stationary die contacting the tip shroud has a shape subtracting a return amount from the shape of the tip shroud after the correction of the deformation. Therefore, the return amount of elastic deformation can be properly corrected. Moreover, in addition to this effect, since the surface of the die contacting the tip shroud has a shape adding a return amount to the shape of the tip shroud after the correction of the deformation, the return amount of elastic deformation can be properly corrected. Furthermore, the deformation correction of the blade can be done in suitable consideration of the return amounts after correction by means of the pressure calculator and displacement calculator of the control device on the basis of the preliminarily stored data particularly concerning the pressure and the displacement.

In the other embodiments, the pressing die may be composed of a plurality of divided sections, and the pressure generator includes a plurality of pressing devices corresponding to the divided sections of the pressing die so as to press the respective divided sections independently in accordance with setting conditions set for the divided sections, respectively successively.

The stationary die may be also composed of a plurality of divided sections so as to correspond to the divided sections of the pressing die, and the hydraulic drive mechanism further includes a pressure generator including a plurality of pressing devices corresponding to the divided sections of the stationary die so as to press the respective divided sections thereof independently in accordance with setting conditions set for the divided sections, respectively successively.

Accordingly, the divided each pressing die section is independently pressed successively against the surface of the tip shroud so as to correct the deformation. Therefore, the pressing does not concentrate on the deformed portion and no crack occurs therein. Moreover, the divided each stationary die section is independently pressed successively against the backside of the tip shroud so as to correct the deformation. Thus, various deformed shapes can be corrected.

Furthermore, the pressing die may be constructed to have a convex portion contacting the tip shroud and the hydraulic drive mechanism includes a pressure generator for pressing the pressing die so that the convex portion contacts a portion of the tip shroud of the blade and also includes a moving device for horizontally moving the pressing die along an entire surface of the tip shroud while being pressed to thereby correct the deformation of the tip shroud during the movement.

The pressing die contacting the tip shroud may be constructed to have convex surface and the hydraulic drive mechanism includes a pressure generator for pressing the pressing die so that the pressing surface thereof rolls along an entire surface of the tip shroud by moving a loading point of the pressing die against the tip shroud surface.

According to such embodiments, the convex portion of the moving die is pressed against the tip shroud while contacting a portion of the surface of the tip shroud and is gradually moved along the entire surface of the tip shroud so as to correct the deformation of the tip shroud. Therefore, the deformed portion is corrected ranging from the central portion to the distal portion without using a complicated die.

Furthermore, the load applying position of the pressing die is gradually moved while the convex surface is gradually moved (rolls) in position contacting the surface of the tip shroud to correct the deformation of the tip shroud. Therefore, pressing force does not concentrate on the deformed portion, and scratches by rubbing in the movement are hard to occur at the pressing operation.

In another aspect of the present invention, there is also provided a method of correcting deformation of a gas turbine blade comprising the steps of:

inspecting presence or absence of deformation of a tip shroud of a gas turbine blade;

judging whether the deformed portion of the tip shroud is to be corrected or not;

softening a blade to which it is judged that the deformation correction is needed;

fixing a stationary die for holding a back surface of the tip shroud to the gas turbine blade on the back side of the tip shroud;

setting a pressing die pressing a front surface of the tip shroud so as to be movable under pressure and stop at a time of contacting the tip shroud; and

pressing the tip shroud against the stationary die from the time of contacting the tip shroud.

The method may further includes the step of judging presence or absence of the displacement of the pressing die when pressed and continuing the correction working in the judgment of presence or stopping the correction working in the judgment of absence.

In the deformation correcting method for gas turbine blade described above, the deformation of the tip shroud of the gas turbine blade can be operated and processed including calculation process in accordance with the past experience data and experiment data, in addition to the return amount due to pressing of the pressing die. Moreover, the softening treatment is carried out with respect to the tip shroud of the gas turbine blade, and thereafter, the deformation of the tip shroud is corrected. Therefore, it is possible to prevent crack occurring in the correction of the deformation.

Furthermore, an HIP material regeneration treatment and solid solution aging heat treatment may be further carried out with respect to the entire gas turbine blade after the correction of the deformation of the tip shroud. Accordingly, even if micro defect occurs in the inside of the gas turbine blade, the defect could be eliminated.

The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described hereunder with reference to the accompanying drawings.

Referring toFIG. 1representing the first embodiment of the blade deformation correction apparatus of the present invention, the deformation correction apparatus includes a stationary die3for fixing a tip shroud2of a gas turbine blade1and a pressing die4for pressing the tip shroud2. The stationary die3is arranged to a lower side of the pressing die4at the time of deformation correction. In order to correct a deformed portion2A of the tip shroud2, the tip shroud2is pressed between the stationary die3and the die4so that the deformed portion2A can be corrected so as to provide a flat shape.

When correcting the deformed portion2A of the tip shroud of the gas turbine blade1, the gas turbine blade1is held between stationary die3(composed of two sections for front and back side surfaces of the blade) to be entirely fixed thereto. That is, the stationary die3has a two-divided structure, and the inner surfaces of the divided two stationary die sections are formed so as to correspond to a shape of the blade directly below the tip shroud. Thus, the stationary die3holds the gas turbine blade of the tip shroud2at a lower portion thereof between the inner surfaces of the two die sections, which are fixed to the deformation correction apparatus.

The stationary die3holding the gas turbine blade1is placed on a fixed table of a portal press shown in FIG.3. The pressing die4is attached to a movable portion of the portal press and the press is actuated so that the pressing die4contacts the deformed portion2A. The contacting position is set as a relative reference position.

When the pressing die4is further depressed downward, the contact surface is pressed against the warped-up deformed portion2A, so that the deformed portion2A is elastically deformed. In this case, a displacement transducer, not shown, measures the descent from the reference position, and the press is moved up after the pressing die4descends to a predetermined position. Then, the gas turbine blade1is taken out of the stationary die3, and the deformation correcting operation ends.

When correcting the deformed portion2A of the tip shroud2into a flat surface, the press is released after the deformed portion2A of the tip shroud2is made flat by the operation of the pressing die4. In such operation, although the plastic deformation is corrected, there exist return of elastic deformation, so-called a spring-back, and the deformation has been still left. Then, the surface of the stationary die3abutting against the tip shroud2is set as a curved surface subtracting the return amount from the final corrected shape, that is, the flat surface. This curved surface may be a surface further bend from a predetermined curved surface. Likely, the pressing die4has a shape adding the return amount to the flat surface.

With reference toFIG. 4, showing the tip shroud shape of the gas turbine blade to which the deformation correction apparatus of the present invention is applicable, in the gas turbine blade1, a preceding end face2F of the tip shroud2of the blade1in the rotating direction contacts a following end face2′B of a tip shroud2′ of another gas turbine blade1A arranged on the preceding side of the blade1. In the same manner, a following end face2B of the tip shroud2of the blade1in the rotating direction contacts a preceding end face2″F of a tip shroud2″ of another gas turbine blade1B arranged on the following side of the blade1. Vibration of the blades can be prevented by friction force due to such contactings of the tip shrouds.

In a case where a gas turbine plant provided with such gas turbine blades is operated for a long period, especially, a portion of the tip shroud2on the following end face2B side of the gas turbine blade1B will be deformed due to the repeated contacts between the following end face2B of the gas turbine blade tip shroud2and the preceding end face2″F of the other blade tip shroud2and due to temperature difference on both upper and lower surfaces of the tip shrouds2.

Furthermore, a plurality of seal fins10are provided for the upper portions of the tip shrouds2of the gas turbine blades1for preventing an operation fluid such as combustion gas from leaking through the front end portions of the blades. In addition, since the gas turbine blade1is exposed to high temperature atmosphere for a long time during its running period, the surface material or substance of the blade is oxidized or nitrated, and especially, the seal fin portions became likely cracked. Because of this reason, when the deformation of the tip shroud is corrected merely by using the press, the seal fins10may be cracked and it is obliged to exchange the blade with new one.

Taking the above facts into consideration, according to the present invention, in order to prevent the causing of such cracks, when the deformation of the gas turbine blade1is corrected, moment force loaded and displacement applied to the deformed portion are always monitored, a spring-back amount is grasped on the basis of data preliminarily obtained through experiments, and a pressing force to be applied is controlled. Further, in a case where the displacement necessary for a predetermined constant pressure obtained from the experiment data is not obtained, the pressing process is not applied (stops).

FIG. 2shows deformation correction steps according to the first embodiment.

FIG. 2Ashows a state that the pressing die4is lowered towards the tip shroud2of the gas turbine blade1which is secured to the stationary die3. In this step, the lowering motion is once stopped at a moment when the pressing die4contacts the deformed portion2A (upwardly deformed) of the tip shroud2. The position of the pressing die4at this moment is stored. Thereafter, a pressure is further applied slowly to the pressing die4so as to continue the deformation correction step to thereby lower the pressing die4. The deformation of the portion2A is to be confirmed. In this operation, when the pressing die4does not indicate any deformation, the operation stops because of possibility of occurrence to certain abnormality.

Next,FIG. 2Bshows a state that the upwardly deformed portion2A of the tip shroud2is depressed by the pressing die4. In this state, as shown, the deformed portion2A of the tip shroud2is depressed downward further from a horizontal level in consideration of return amount of the elastic deformation.

FIG. 2Cshows a state that the pressing force is released and the pressing die4is returned upward. In this state, since the deformed portion2A of the tip shroud2is pressed by an extra amount in consideration of the return amount, the deformed portion2A of the tip shroud2provides a flat shape which is finally desired after the removal of the pressing force by the pressing die4.

A deformation correction (correcting) apparatus, according to the fist embodiment, for carrying out the steps or operations mentioned above will be explained hereunder with reference to FIG.3.

With reference toFIG. 3, the deformation correction apparatus100of the present embodiment generally comprises the stationary die3to which the tip shroud2of the gas turbine blade1is secured, the pressing die4adapted to press the tip shroud2, a supporting mechanism56,57for supporting the stationary and pressing dies3,4, a hydraulic drive mechanism52,53for driving the pressing die4, and a control system or device51for controlling the operation of the hydraulic drive mechanism.

In more detail, the pressing die4is secured to a flange61formed to the front end portion of a piston60reciprocally moving in a hydraulic cylinder53supported by an outside support column56. On the other hand, the stationary die3is fixed to a horizontal beam57aof an inside support column57and adopted to support the tip shroud2when pressing the deformed portion2A thereof as well as support the blade1from the lower surface side of the tip shroud2. A stud11provided for a portion of the blade1on the end side opposite to the location of the tip shroud2is snapped and fastened, in an embedded state, between stud chuck58which is moved on a rail member58A, to be opened or closed, disposed on a fixing base59. Since the gas turbine blade1is secured by the stationary die3and the stud chuck58, the entire blade1is not deformed even if pressure by the hydraulic cylinder53is applied. The hydraulic cylinder53is operated, through a hydraulic control duct(s)55, by the hydraulic pressure generator52generating a pressure suitable for the blade1to be corrected in response to various control signals from the control device51through a control bus54. The piston60, the hydraulic cylinder53, the pressure generator52and the ducts or like55,54constitute the hydraulic drive mechanism for driving the pressing die4.

In the deformation correction apparatus100of the structure mentioned above, the hydraulic pressure generator52gives pressure and/or displacement force necessary for carrying out the deformation correction process to the hydraulic cylinder53through the piston60and then to the pressing die4in response to various control signals from the control device51.

On the other hand, the gas turbine blade1is fixed at its tip shroud lower surface and embedded stud11, only the deformed portion2A can be corrected without influencing other portions. Further, the outside and inside support columns56and57are firmly secured to the base59, so that the dies3and4can be driven at the deformation correction working without being adversely affected even by a large pressure applied by the hydraulic cylinder53.

FIG. 5shows a detail structure of the control device51.

With reference toFIG. 5, at the time of starting the deformation correction working to the gas turbine blade1, an initial data202, for example, concerning deformed amount, material of blade, deformation correction history and so on, is first inputted into a deformation correction processing device (element)201arranged inside the control system or device51through an inputting device such as key-board. The deformation correction processing device201operating device201indexes an experiment data base (DB)203and a correction experience data base (DB)204, preliminarily stored, in accordance with the initial data202mentioned above and, in accordance with the most suitable experiment data or past deformation correction data, information (data) regarding displacement and pressure are derived and transmitted to displacement operating device (calculator)205and pressure operating device (calculator)206, which are then operated in accordance with the data from the deformation correction processing device201and then transmit signals representing the data through the operation of the piston60of the hydraulic cylinder53by the hydraulic pressure generator52.

When the blade deformation correction working starts, the data of actual displacement through the contact of the pressing die4to the deformed portion2A of the tip shroud2is sequentially transmitted as feedback data to an indication/actual displacement comparator207of the control device51.

In the indication/actual displacement comparator207, indication signals from the displacement operating device205and pressure operating device206are compared with signals representing the actual displacement from the hydraulic cylinder53, and the compared result (data) is then transmitted to the deformation correction processing device201, in which the comparison with the experiment data base203and the correction experience data base204is again performed. In this comparison, in case a large difference therebetween be found, a signal for stopping the working is transmitted.

On the other hand, the data transmitted from the displacement operating device205and the pressure operating device206to the hydraulic pressure generator52are branched immediately after the transmitting and then inputted respectively to an indication signal/actual signal comparing calculator208, into which the actual displacement data is also inputted from the cylinder53. The indicated displacement and pressure data and their feedback data from the indication signal/actual signal comparing calculator208are stored in the correction experience DB204together with the initial input data in the deformation correction processing device201. The data stored in this correction experience DB is referred to in deformation correction working of the same gas turbine blade which will be again performed in future.

Further, as concrete data of the experiment DB203, there will be listed up: data of a return amount (spring-back amount) with respect to the displacement applied to the deformed portion2A by the pressing die4; data of elastic deformation or plastic deformation caused to the deformed portion2A at the time of applying a load (pressing time) of the pressing die4; and other data, which will include data concerning the actual experiment or numerical analysis.

On the other hand, the concrete data of the correction experience DB204may include data of return amount (spring-back amount) with respect to the deformation given to the deformed portion2A by the pressing die4, and data of displacement indication amount, pressure indication amount, material, operation time, blade length, plant name, tip shroud shape, and so on, in addition to the data of elastic deformation or plastic deformation caused to the deformed portion2A at the time of applying a load (pressing time) of the pressing die4.

According to the first embodiment, the backside of the tip shroud2is fixed by using the stationary die3, and the embedded stud11of the blade1is also fixed. Therefore, the correction working can be done stably regardless of the blade length, and the turbine blade1can be readily fixed to the stationary die3. Further, since the warped-up deformed portion2A of the tip shroud2is corrected, there is no need of adjusting the arrangement of the gas turbine blades in order to secure the contact area of the gas turbine blades1. Furthermore, it is possible to recycle the gas turbine blades1, without discarding, which have been discarded because of the reason that the contact area is not secured even if the arrangement is adjusted.

Since the return due to the elastic deformation in the shape of the stationary die3and the pressing die4is taken into consideration in accordance with the preliminarily stored experiment data, a desired shape is obtainable after the pressing has been released. In addition, since the pressure at the pressing time is controlled and the minimum deformation is only given to obtain the predetermined final shape, crack which may be generated by the extra deformation will be effectively prevented. That is, this embodiment may be especially applicable to the tip shroud the deformation of which is relatively small to the extent that the deformation can be corrected by one pressing operation.

FIG. 6shows the shape change of the gas turbine blade, before and after the deformation correction, to which the first embodiment of the present embodiment is applied. The axis of ordinate represents deformation amount (percentage) at respective portions with reference to the top point of the tip shroud2and the axis of abscissa represent front and rear distances (percentage) from the top position (reference point) of the tip shroud2.

With reference toFIG. 6, the deformation of the tip shroud2of the blade1at a time of being newly manufactured is shown with dotted line, in which the tip shroud2shows a mount shape viewed from rotational surface of the blade1. The solid line shows the deformation amount before correction of the tip shroud of the blade used for a long time, from which it is found that the tip shroud2is largely deformed on one side from the top point in comparison with the newly manufactured blade. Furthermore, the dot-and-dash line shows the deformation amount, after correction by using the deformation correction apparatus of the present invention, of the tip shroud from which it is found that the shape as that of the tip shroud returns almost the same shape of the new one. In addition, it will be also found that other deformed portions not so largely deformed can be corrected to substantially the same shape of the new one.

The second embodiment of the present invention will be described hereunder with reference toFIG. 7showing the structure of an essential portion of the deformation correction apparatus for a gas turbine blade. According to the second embodiment, the pressing die4is composed of divided two or more blocks (sections), unlike the first embodiment shown in FIG.1. The respective blocks of the pressing die4are independently pressed against the tip shroud so as to correct the deformation.

As illustrated inFIG. 7, the gas turbine blade1is fixed by using the stationary die3. The way to fix the stationary die3is the same as that of the first embodiment. In the second embodiment, the pressing die4is divided into two or more blocks. That is, the pressing die4is composed of a main section4a, a first section4b, a second section4cand a third section4d.

The entire structure of the deformation correction apparatus of this second embodiment is shown inFIG. 8, in which the same reference numerals are used to designate components identical to those of the first embodiment, and the overlapping explanation is omitted herein.

In the deformation correction apparatus of this second embodiment, a plurality of hydraulic cylinders53(53A to53D) are arranged so as to independently drive the divided pressing die sections4ato4d, and in correspondence to this arrangement, a plurality of hydraulic pressure generators52(52A to52D) are also arranged. The other structure is substantially the same as that of the first embodiment of FIG.3.

By using the deformation correction apparatus of this embodiment, first, the main section4ais actuated to press the relatively central portion of the deformed portion2A of the tip shroud2. In this state, the first die section4bis pressed against the deformed portion. Further, in this state, second and third die sections4cand4dare pressed in succession. Therefore, the deformation from the distal end to the central portion of the deformed portion2A is stepwise corrected. The pressing force is released after the pressing of all the die sections4ato4d, and the stationary die3is then removed, thus completing the deformation correcting process.

Further, in this second embodiment, in the control device51, moment force acting to the boundary portion of the deformed portion2A of the tip shroud2corresponding to the main and first die sections4aand4bis calculated, and the control signal is given to the cylinder53B pressing the first die section4bin consideration of this moment force so as not to cause any crack to the deformed portion2A. Under the state, the second die section4cis pressed, at which in the control device51, moment force acting to the boundary portion of the deformed portion2A of the tip shroud2corresponding to the first and second die sections4band4cis calculated, and the control signal is given to the cylinder53C pressing the second die section4cin consideration of this moment force so as not to cause any crack to the deformed portion2A. Furthermore, under this state, the third die section4dis pressed, at which in the control device51, moment force acting to the boundary portion of the deformed portion2A of the tip shroud2corresponding to the second and third die sections4cand4dis calculated, and the control signal is given to the cylinder53D pressing the third die section4din consideration of this moment force so as not to cause any crack to the deformed portion2A.

According to the second embodiment, it is possible to correct the deformation without generating cracks even if a large deformation is generated in the distal end of the tip shroud2. That is, when the large deformation is generated in the distal end of the tip shroud2, if a non-divided pressing die4is used, a large deformation is initially generated in the distal end of the deformed portion. Thus, there is a possibility that a strain which may reach a breaking elongation will occur in the material of the gas turbine blade1. This phenomenon will be further increased because of the denature of the blade surface because of the long time operation. On the contrary, in this second embodiment, the deformed portion is pressed from the proximal root portion to the distal end portion in succession by using the pressing die4having divided sections. Therefore, the load, i.e., moment force, is controlled with respect to the deformed portions corresponding to the respective die sections, and accordingly, the press correction does not concentrate on the distal portion, and hence, no crack occurs therein.

The third embodiment of the present invention will be described hereunder with reference to FIG.9and FIG.10.

In the third embodiment, the stationary die3is divided into two or more blocks, in addition to the second embodiment shown in FIG.9. Blocks, that is, die sections3ato3dare independently pressed against the back surface of the tip shroud2in succession to thereby correct the deformation of the tip shroud2.

As shown inFIG. 9, the stationary die3and the pressing die4are individually divided into or composed of two or more blocks. In the embodiment ofFIG. 9, the stationary die3is divided into four sections, that is, a stationary die main section3a, a first die section3b, a second die section3cand a third die section3d. On the other hand, as mentioned before, the pressing die4is divided into four sections, that is, a pressing die main section4a, a first die section4b, a second die section4cand a third die section4d.

In the deformation correction apparatus of this third embodiment, a plurality of hydraulic cylinders53(53E to53G) are arranged so as to independently drive the divided stationary die sections3bto3d, and in correspondence to this arrangement, a plurality of hydraulic pressure generators52(52E to52G) are also arranged. The other structure is substantially the same as that of the first embodiment of FIG.8.

First, in a state that the stationary die sections3ato3dare kept at the normal position, the pressing die main section4ais actuated to press against the relatively central portion of the deformed portion2A of the tip shroud2. In this state, the first (pressing) die section4bis pressed. After being pressed, the first die section4bis moved up so as to release the pressing force, while the first (stationary) die section3bis moved up to the position shown by the broken line, that is, corresponding to the return amount due to the elastic deformation. Thereafter, the second pressing die section4cis pressed against the tip shroud, and then, the second (pressing) die section4cis moved up so as to release the pressing force. The second (stationary) die section3cis moved up to the position shown by the broken line, that is, corresponding to the return amount due to the elastic deformation. Finally, the third (pressing) die section4dis pressed against the tip shroud, and then, the third die section4dis moved up so as to release the pressing force. According to the manner mentioned above, the deformation can be completely corrected. As described above, the position of the stationary die3after the correction is shifted from “the position subtracting the return from the shape after correction” to “the position of the shape after correction”. Thus, the deformation has been corrected.

The control operation or mode of the control device51to the hydraulic mechanism including the hydraulic pressing devices52B to52D and the cylinders53B to53D for pressing the pressing die sections4bto4dare substantially the same as those of the second embodiment, so that the detail thereof is omitted herein.

According to the third embodiment, the tip shroud2is sectionally pressed, and therefore, it becomes possible to correct the deformation even with a low pressing ability. The tip shroud2is gradually corrected ranging from the central portion to the distal portion of the deformed portion2A with the already deformed portion being fixed, so that the deformation does not become large, and no crack occurs therein.

In addition, the combination pattern of the divided dies may be changed, so that the various deformed shapes can be corrected correspondingly.

FIGS. 11 and 12represent the fourth embodiment of the present invention.

According to the fourth embodiment, a small-sized pressing die5, which is constructed to be movable, is used in place of the pressing die4, unlike the first embodiment shown in FIG.1. The movable pressing die5has a portion contacting the tip shroud2formed so as to provide a convex shape. The convex portion is pressed while contacting a portion of the surface of the tip shroud2, and is gradually moved to the entire tip shroud2as the movable pressing die5is moved horizontally. Thus, the deformation of the tip shroud2is corrected.

With reference toFIG. 12showing the entire structure of the deformation correction apparatus of this fourth embodiment, the movable pressing die5is mounted to a pressing die support structure5awhich is movable along the longitudinal direction of the blade tip shroud2by means of pistons of hydraulic cylinders53B1and53B2for horizontally moving the pressing die5, the cylinders53B1and53B2being supported by a pressing column56aprovided to the front end of the piston60of the hydraulic cylinder53A supported by the outside support column56.

The respective hydraulic devices, i.e., cylinders,53A,53B1and53B2are connected to the hydraulic pressure generators52A and52B, which are controlled and driven by the control device51in response to the control signals transmitted therefrom via signal buses54A and54B so as to output most suitable pressure (pressing force) and displacement to the deformed portion2A of the blade tip shroud2.

To the other structure, the same reference numerals are used to designate components identical to the first embodiment, and the overlapping explanation is omitted herein.

In the fourth embodiment, the shape of the small-sized movable pressing die5is different from the pressing die4of the first embodiment, and the downwardly convex portion is formed. The convex portion of the movable pressing die5has a shape contacting the portion of the tip shroud2. The moving die5is moved from the proximal portion to the distal portion of the deformed portion2A of the tip shroud2while being gradually pressed against the deformed portion2A. InFIG. 11, a pressing die5′ shown by a broken line is the final press position of the movable pressing die5after being moved. In this manner, the pressing force is released after being pressed, and deformation correcting has been completed.

In a preferred example, it is desirable to move the pressing die5at a moving speed of 1 to 5 mm/sec. On the contrary, when moved at a speed lower than this moving speed, working time is merely elongated and no substantial effect for the deformation correction is obtainable, and when moved at a speed higher than that moving speed, the die5is moved before the completion of the plastic deformation, resulting in bad deformation correction efficiency. Further, it may be possible to be moved in a repeated manner from the root position to the distal end position of the deformed portion2A. In this operation, it is necessary to pay an attention to start the moving from the root position towards the distal end position of the deformed tip shroud portion2A. If the repeated moving is started from an intermediate position, difference in strength is caused to portions of the tip shroud2, resulting in damage on use life thereof.

According to this fourth embodiment, one movable pressing die5presses the deformed portion2A of the tip shroud2ranging from the central portion to the distal end portion. Therefore, any complicate divided die is not required. Even if the gas turbine blade1has different tip shroud shape, one movable pressing die5of this structure is applicable without changing the shape of the pressing die5as far as it has a relatively similar shape.

The fifth embodiment of the present invention will be described below with reference toFIG. 13showing the structure of an essential portion of the deformation correcting apparatus for a gas turbine blade.

In the fifth embodiment, the surface of the pressing die4contacting the tip shroud2is formed into a shape of convex surface, unlike the first embodiment shown in FIG.1. The loading position of the pressing die4is gradually moved so as to gradually move the convex surface along the position contacting the tip shroud surface. Therefore, the deformation of the tip shroud2is also corrected by this fifth embodiment. The same reference numerals are used to designate components identical to the first embodiment, and the overlapping explanation is omitted.

According to this embodiment, as illustrated inFIG. 13, the gas turbine blade1is fixed by using the stationary die3. The way to fix the stationary die3is the same as that of the first embodiment. In the fifth embodiment, the pressing die4is not moved to the lateral direction and formed to provide the convex surface so as to press against the deformed portion2A.

That is, the pressing die4is first pressed against the tip shroud2so as to contact the central portion. Thereafter, the press loading position of the pressing die4is gradually shifted to the distal end portion of the deformed portion2A, and accordingly, the contact surface of the pressing die4with respect to the deformed portion2A of the tip shroud2gradually changes. Finally, the pressing is carried out by the position of the die4′ shown by a broken line. Thereafter, the press is released, and the deformation correction has been completed.

According to the fifth embodiment, the press loading position applied to the pressing die4is gradually shifted to successively press the deformed portion2A from the proximal portion to the distal portion. Therefore, the press correction does not concentrate on the distal end portion, and no crack occurs therein. In addition, since the pressing die4is not moved in the horizontal direction, rubbing scratches or like are hard to occur in the pressed portion during the movement.

Hereunder, the gas turbine blade deformation correction method according to another embodiment of the present invention is carried out by utilizing the deformation correction apparatus100of the first embodiment shown inFIG. 3, for example, and will be described with reference to the flowchart of FIG.14.

In a case where a gas turbine equipped with a blade tip shroud2having a deformed portion2A has been continuously driven, an adverse phenomenon such as abnormal vibration or power lowering will occur. Therefore, it is necessary to carry out a periodical inspection to monitor the operating state.

Usually, in the use of the deformation correction apparatus100of the characters mentioned above, the turbine blades are subjected to the deformation correction working one by one by setting the deformation correction apparatus, and for this reason, it is first necessary to stop the operation of the gas turbine plant (step S1).

Then, the deformed condition of the tip shroud portion is visually inspected one by one (step S2). In the case of no deformation or slight deformation which requires no specific correction working, the blade in the next stage is inspected (step S3).

In the case of finding the deformed one, it is withdrawn from the gas turbine shaft (step S4). The withdrawn gas turbine blade is degraded in its quality or material and its ductility because of long-term use thereof in a sever condition. In such a case, a heat-softening treatment is performed (step S5) by putting and heating the blade in a vacuum furnace or locally heating a portion near the deformed portion through a high-frequency induction heating process. In such heating treatment, the heating temperature depends on the material of the blade, and in usual, this heating temperature is set to a temperature more than that required for fusing the material.

Next, the turbine blade is set to the stationary die3of the deformation correction apparatus100(step S6) and positioned and fixed thereto (step S7). The stud portion11of the blade1is then fixed (step S8). According to these steps, the blade is firmly fixed to the deformation correction apparatus100, and the pressure in the deformation correction working time is not applied to the entire blade.

The pressing die4is set to the hydraulic cylinder53of the deformation correction apparatus100(step S9). The stationary die3and the pressing die4having preliminary determined shapes are used in view of the preliminary observation of the deformed condition, the past correction working data, past experiment data and so on.

In the next step (step S10), the hydraulic cylinder to which the pressing die4is mounted is lowered to a position at which it contacts the deformed portion2A of the tip shroud2of the blade1. This step S10is performed for the reason of determining a reference position for collecting, as data, relationship between the displacement of the deformed portion or pressure of the cylinder and the actual displacement of the deformed portion and for the reason of avoiding an occurrence of a crack to the material due to the rapid or violent deformation correction working. Next, a pressure is applied to the hydraulic cylinder53to press the deformed portion2A of the tip shroud between the stationary die3and the pressing die4(step S11). In this step, the pressure of the cylinder53and the actual displacement of the pressing die4are transmitted to the control device51as feedback data.

In this step, the pressure to be applied to the hydraulic cylinder53and the displacement of the deformed portion of the tip shroud2are monitored and it is discriminated whether the displacement of the deformed portion2A of the tip shroud2exist or not (step S12). In the case where it is discriminated that the preliminarily determined displacement of the deformed portion is obtained together with the pressure, it is judged that the correction is completed and then the correction working is ended. On the other hand, in the case of no displacement of the tip shroud even in the increasing of the cylinder pressure or obtaining a displacement data extremely different from the past data, it is judged that some abnormal portion exists and the correction working is interrupted (step S13). In such case, the deformation corrected blade is removed from the deformation correction apparatus and a new blade to be corrected is set to the apparatus and new correction is started from the step S6.

Further, as occasion demands, an HIP material regeneration treatment may be performed after the deformation correction working to regenerate the material of the whole blade, and in addition, a solution annealing and aging heat treatment suitable for the material of the gas turbine blade may be further carried out.

According to the blade deformation correction method of this embodiment, the tip shroud is softened before the correction of the deformation of the tip shroud, thus occurring no crack therein. In addition, at a time when the deformation of the tip shroud is corrected, a micro defect occurs in the inside of the tip shroud. Even if the foregoing micro defect occurs, the defect could be eliminated in the HIP material regeneration after the correction of the deformation, thus safety being secured.

As described hereinbefore, according to the present invention, it is possible to simply correct the deformation of the tip shroud of the gas turbine blade without generating cracks. The deformation of the tip shroud is simply corrected, so that the gas turbine blade after operation can be recycled without newly using an expensive gas turbine blade and adjusting the arrangement of the gas turbine blade.