Description:A BLADE STUB FOR TURBINE ROTOR TESTING

FIELD OF INVENTION:

The present invention relates to the design of blade stubs which are to be assembled into test piece rotor. The invention in particular relates to a blade stub for turbine rotor testing.

BACKGROUND OF THE INVENTION:

Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

In a typical larger power stations based on the steam parameters, the steam turbines are split into three separate modules, the first being the high pressure module, the second being the intermediate pressure module and the third being the low pressure module. These turbines are designed to efficiently convert thermal energy into mechanical energy.

Today, it is a global quest to utilize fossil fuel more efficiently in power plants to achieve climate related goals on national as well as at a global front. To increase the efficiency of thermodynamic cycles of steam power plants the classical method is to increase the operating parameters such as input steam parameters. But higher the temperature of operation, lesser is the resistance of material to creep, a time-dependent failure of materials at elevated temperature under applied stresses. The utility of materials, exposed to elevated temperature and pressure, is limited by their capacity to sustain elevated temperatures without undergoing loss of strength over prolonged exposure. Today, designers are working to utilize these turbines which shall have input steam temperature to an extent higher than 700°C.

For such a temperature, steam turbine including rotor and its blades formed of exotic alloy materials apt to demonstrate desired mechanical properties at elevated temperature by withstanding such ever increasing operating conditions of more than 700°C, extent of difference in fluid pressure and temperature at inlet and exit of the turbine. Turbine rotor and associated blades often constitutes considerable material of the turbine and therefore significantly contributes to the cost of the turbine. If the rotor and blades incorporates high cost, high temperature metal alloys in entirety of their formation, the cost of the turbine module is even higher.

The manufacture of such large rotor also demands the provisions of correspondingly large manufacturing facilities, with the associated lifting and manipulation means. This limits the supplier competition which thereby pushes the cost further up.

Therefore, to overcome such challenges, bimetallic turbine rotor with its constructional features and its method of manufacturing were developed. Such bimetallic rotor includes a high temperature material rotor section formed of a high temperature material, and a low temperature material section formed of a low temperature material. The low temperature material section joined to an end of the high temperature material section. These rotors shall be capable to operate for a temperature range upto 720? and to meet the operational requirements.

BHEL is designing and developing the technology for AUSC turbine under which Rotor and associated blades to be designed and developed.

The rotor uses a high temperature material (HTM), such as but not limited to nickel based alloys, on the high temperature sides and uses a low temperature material (LTM), such as but not limited to 12% chrome alloy steels on the intermediate to low temperature, pressure sides because of their superiority in sustainable mechanical properties in this regime. At the location where the temperature is high enough to mitigate the use of LTM a bimetallic joint, such as a weld joint, between a high cost HTM and a low cost LTM is envisaged to lower the product cost while the rotor remains integrated with mechanical abilities under constant influence of service steam parameters it is exposed to.

Rotor testing is part of Rotor testing planned under test loop of AUSC project. The rotor is a part of inlet section of welded rotor configuration used in IP turbine design. The inlet section and few stages up to high temperature zones of IP turbine are designed with Alloy 617M material. The rest of the stages up to exhaust is designed with 10% chromium (X12) material. Both the materials are joined using Dissimilar Metal Joints. Alloy 617M being the new material used for the first time for steam turbine IP Rotor design application, the testing of Alloy 617M material Rotor including blade groove geometry is planned. For this a portion of inlet section of IP Rotor with Alloy 617M material taken, which is named as Test rotor.

As the testing is planned to simulate actual loading of rotor including blade grooves during turbine operation, the blade grooves are manufactured on the test Rotor as per actual design. However, to simulate the loading of blades on groove due to rotation, there existed a need of Blade Stubs which can be designed and used instead of actual blade geometry so as to save the design validation cost.

Rotor and stubs are part of the Rotor testing under AUSC mission project. The blade stubs are designed to simulate actual loading on the blade grooves of the rotor under operating temperatures during testing. The blade stubs are innovatively designed to have same root contour for blade fixing in rotor grooves, while no profile shape for easy manufacturing therefore avoids complexity of profile and shroud.

To meet the suitability of testing a detail study was made on the requirement of test rig set-up and procedure of the testing. There was limitation of blade height due to size of pit and provision of heating element on the test rig.

The blade stubs are designed to meet the desired loading condition of actual rotor during operation. The blade pull load was kept same for the stubs, while keeping the geometry simple for manufacturing and save cost.

The 3D model of each blade stubs are developed through design iteration, and are the object of invention. Similarly, the Engineering drawings of each blade stubs are developed for manufacturing are the object of invention.

OBJECTS OF THE INVENTION:

It is therefore, an object of the present invention to propose a blade Stub in place of a cost expensive actual blade for testing turbine rotor wherein such blade stubs can be designed and used instead of actual blade geometry so as to save the design validation cost.

An another object of the present invention is to propose blade stub that can simulate actual loading on the blade grooves of the rotor under operating temperatures during testing.

Yet another object of the present invention is to provide blade stub, which can be suitably assembled on the rotor under testing and fulfil the desired objectives of testing.

Still another object of the invention is to provide blade stub for turbine rotor testing, which is simple in construction with ease in manufacturing.

These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:

One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

According to this invention, there is provided a blade stub for the rotor testing. In the exemplary embodiment of the invention, total 5 rows of blades stubs are designed for this application, out of which 1 row of blade stubs is in left hand side while 4 rows of blade stubs are in right hand side.

The parameters used for the design of blade stubs are as follows:
The original blade geometry of each stages/rows are used as input for design of blades stubs.
The fixing part of blades i.e. root is kept same as original turbine blades.
The length of the top part of original blades is determined, wherein the blade stubs do not have the profile and shroud part of turbine blade.
The geometry dimension of top part of blade is determined by equating the centrifugal pull of original blades of intermediate pressure Turbine.

Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS:

The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

Figure 1 shows: 3 dimensional view of Test Rotor with blade grooves, in accordance with the present invention;

Figure 2 shows: sectional plane of Test Rotor with blade grooves of the present invention;

Figure 3-7 shows: 3D Front view of Blade Stubs with single or double T-root for Test Rotor (from 1R to 4R and 1L), according to the present invention;

Figure 8 shows: a moving blade with T-root of actual turbine;

Figure 9 shows: an equivalent moving stub of that moving blade [figure 8] with the same T-root, in accordance with the invention.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

The invention makes a disclosure regarding a technology pertaining to blade stub for turbine rotor testing.

There are two basic requirements of blade Stub, first is the Centrifugal Pull of stub should be same as that of actual blade on the Test Piece Rotor of turbine and second is that the blade Stubs should be held tightly and do not loosen during rotation.

For that, the stubs design is made simple for manufacturing. The Stubs have the root for fixing/assembly into test rotor. The root design of stub is same as actual turbine blades. The blade profile and shroud of turbine blade is replaced with the dead weight of the blade stubs. The length of the stubs is modified in order to meet the centrifugal loading of actual blades during rotation.

The following equation is used to find the length of blade stubs:
M_Stubs.R_(c.g,stubs)=M_blade.R_(c.g,blade)
Where,
R_(c.g,stubs) of Stubs are iteratively determined by reducing height of stubs.

Few points are kept in mind while devising stubs for a particular turbine blade such as: a) equivalent centrifugal force for a stub should be equal to blade b) stub root is kept as per original blade root c) stubs fixing to be kept as per original blade fixing.

In one embodiment of the instant invention as best seen in figure 1 and 2, four rows of blade Stubs with Double-T Root Stubs and one row with Single T-Root Blade Stubs have been developed using the inventive concept of invention.
Reference may be made to figure 3-7 indicating blade Stubs with single or double T-root for Test Rotor (from 1R to 4R and 1L) according to exemplary embodiment of the present invention. Here, the blade stub [100] includes root forming bottom part [101] and top part [102] integrated to each other constituting a single piece. The stub [100], which is substantially having rhomboid shape/section from top and bottom thereof. In the front view, said root [101] of the stub [100] is having substantially T-section and the top part [102] has rectilinear section.

The aforesaid stub can be manufactured by the method of machining and can be made of material including Nickle alloy without restricting scope of the invention to the same. Thus, other materials and methods readily apparent to a person skilled in the art are understood to be within purview of the invention.

Thus, the proposed invention makes use of blade stub [100] for testing of turbine rotor instead of actual turbine blade. So that, the cost will be less.

3D model/proto type of moving blade and Stubs are prepared to determine and match centrifugal forces of the both. In figure 8, a moving blade has been shown with T-root of actual turbine and in figure 9, an equivalent moving stub of that moving blade has been shown with the same T-root.

There is one Lock blade stub for each row of blade stubs in each groove. The lock blade stub has modified root whereas Top part is same, wherein the whole lock blade stub is same as that of actual blade of turbine used for locking.

There are Lightning hole (s) in the lock blade stubs to reduce its overall weight. Its dimensions are determined by detail design of locking arrangement with locking screws.
Thus, the blade stub [100] for turbine rotor comprising a blade body having dead weight [102] and a root [101] designed to fix blade in the test piece Rotor groove so as to resemble the dead weight of actual blade stub to meet the centrifugal loading of actual blade during rotation.

The length of the blade stub is significantly reduced so as to minimize the test setup cost whilst the pitch angle ensures full contact while rotation of rotor at operating speed to eliminate any blade looseness and blade twist of the blade stub root ensures tightness of the assembly while completely eliminating the need of a conventional blade shroud and associated manufacturing costs.

The centrifugal pull of blade is same as that of actual blade on the test piece Rotor and stubs are held tightly and do not loosen during rotation.

3-D model of moving blade and Stubs are prepared to calculate and match centrifugal forces of the both.

The blade pull load is kept same for the stubs, while keeping the geometry simple for manufacturing and to save cost.

The blade stubs are installed in the Grooves of Rotor as illustrated in Figure 1 and 2, wherein each of the blades are in contact with other and the contact surface is called the pitch plane. The pitch plane of Blades roots is conical and is called as pitch angle. The Pitch angle is kept in such that there is full contact while rotation of Rotor at operating speed, and there is no looseness during operation. As the root of blades are of Rhomboid shape, the method of obtaining pitch angle is complex. The more tighter the installation of blade the more will be pitch angle, because the blades are given additional pre-twist for assembly in groove.
ADVANTAGES OF THE INVENTION:
Simple in construction;
Cost effective;
Ease in manufacturing;
Serves the purpose efficiently.

WORKING OF THE INVENTION:
The Blade Stubs will be assembled (from 1R to 4R and 1L) in Test Rotor using assembly items such as Lock screws & Caulking pieces. The assembled Rotor will be installed in Test pit where it will be rotated to various speed (rpm) for creep fatigue testing. The assembled Blade stubs will exert pull load on the Rotor (which is one of the requirement of testing). The Pull load exerted by Blade stubs will be same as that of actual Blade in the Turbine Rotor. The design of Blade stubs is simpler and economical as compared to actual turbine Blade.

TEST RESULT:
The design of Blade stubs has been carried out using standard design software which does not require any physical testing.

It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other cast structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.

Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims:WE CLAIM

1. A blade stub [100] for turbine rotor testing comprises of root forming bottom part [101] and top part [102] integrated to each other constituting a single piece, in which the stub [100] is substantially having rhomboid section in top and bottom view; said root [101] of the stub [100] is having substantially T-section and the top part [102] has rectilinear section in the front view, wherein the Centrifugal Pull of stub is same as that of actual blade on the Test Piece Rotor of turbine, and the blade Stub is held tightly and does not loosen during rotation, in which the root is assembled into said test rotor.

2. The blade stub [100] for turbine rotor testing as claimed in claim 1, wherein the root [101] of stub is same as actual turbine blade, in which the blade profile and shroud of turbine blade is replaced with the dead weight of the blade stub, and the length of the stub is determined in order to meet the centrifugal loading of actual blades during rotation.

3. The blade stub [100] for turbine rotor testing as claimed in claim 1 or 2, wherein the blade Stub is having Double T- Root/ Single T-Root.

4. The blade stub [100] for turbine rotor testing as claimed in claims 1-3, wherein the stub is manufactured by the method including machining and is made of material including Nickle alloy.

5. The blade stub [100] for turbine rotor testing as claimed in claims 1-4, wherein one Lock blade stub is provided for each row of blade stubs in each groove, in which the lock blade stub has modified root and the Top part is same, wherein the lock blade stub [100] is same as that of actual blade of turbine used for locking.
6. The blade stub [100] for turbine rotor testing as claimed in claims 1-5, wherein Lightning hole (s) is provided in the lock blade stub so as to reduce its overall weight, in which its dimensions are determined by locking arrangement with locking screws.

7. The blade stub [100] for turbine rotor testing as claimed in claim 6, comprising of a blade body [102] having dead weight and a root [101] designed to fix blade in the test piece Rotor groove so as to resemble the dead weight of actual blade stub to meet the centrifugal loading of actual blade during rotation.

8. The blade stub [100] for turbine rotor testing as claimed in claims 1-7, wherein the length of the blade stub is reduced so as to minimize the test setup cost whilst the pitch angle ensures full contact during rotation of rotor at operating speed to eliminate any blade looseness and blade twist of the blade stub root ensures tightness of the assembly while completely eliminating the need of a conventional blade shroud and associated manufacturing costs.