DESC:FIELD OF THE INVENTION

[001] This invention relates to an improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine.

BACKGROUND OF THE INVENTION

[002] 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.
[003] A conventional axial flow gas turbine engine includes an array of turbine blades which extend through a flow path for hot gases, or working fluid, exiting a combustion section. As a result of the engagement with the working fluid flowing through the flowpath, the array of blades rotate about a longitudinal axis of the gas turbine engine. Efficient operation of the turbine requires minimizing the amount of working fluid which bypasses the turbine blades as the working fluid flows through the turbine.
[004] One provision of accomplishing this is to provide an annular shroud which extends about the array of turbine blades in close radial proximity to the radially outward tips of the turbine blades. Shrouds/diaphragms not only act as means to optimize the clearance between rotor and stator, but also act as protective shield for casing. Shroud segments are radially retained to the turbine casing by means of hook type circumferential rail integrally machined into the casing.
[005] Currently available gas turbine engines typically use shrouds comprising of a plurality of segments which are circumferentially aligned to form the annular shroud.
[006] Problem Statement: During scheduled major inspection of gas turbine, stage 2 hook fit pertaining to turbine casing was damaged during removal of seized Stage 2 shroud segment.
[007] Damage portion is located in seg #22 and seg #23. ~58% hook fit contact lost in seg #22 and ~21% hook fit contact lost in seg #23 as indicated in figure 1.
[008] There are instances of hook fit damages (like cracks, missing material). This results in insufficient engagement between the casing and the shrouds/diaphragms segments resulting in casing being unusable.

Initial Containment Plan

- No repair method available for turbine casing hook fit.
- Development program needed for any patch repair or any other form of repair recommendation.
- Considering the above challenges, casing replacement is only option available.
[009] Available options of new casing or patch ring repair (needs development program) leads to significant cost as well as significant outage delay (>5-6 months if new casing is considered).
[010] Thus, in order to restore gas turbine operation, the gas turbine tube has to be sent back to service center for casing replacement, which is both costly and time consuming.
[011] In view of the above, it is required to devise an alternative for quick restoration of the unit. Hence, the present invention has been introduced proposing custom made (customized) shroud segment.
OBJECTS OF THE INVENTION

[012] An object of the invention is to propose an improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine which overcomes shortcomings of the prior art.
[013] Another object of the invention is to propose an improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine which is simple in construction.
[014] Still another object of the present invention is to provide an improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine which is cost effective.
[015] Yet another object of the present invention is to develop an improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine for quick restoration of gas turbine operation.
[016] 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

[017] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus 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.
[018] According to this invention, there is provided an improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine comprising of a shroud segment integrated to a cover so as to cover damaged hook fit area, wherein the shroud segment is having circumferential length equivalent to length of two existing shroud segments.

[019] The cover is having a profile corresponding to that of hook maintaining clearance from the damaged hook of the turbine casing so as to avoid interference therewith.
[020] The cover is placed on the inner surface of the shroud segment facing the hook of said turbine casing.

[021] The shroud is having length of two shroud segments thereby having longer circumference causing sufficient engagement ratio between the turbine casing hook fit portion and shroud for safe operation of the machine.

[022] The shroud segment can be made of any steel and can be manufactured by machining.
[023] 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 figure in which like numerals represent like components.
[024] 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.
[025] 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 THE ACCOMPANYING DRAWINGS

[026] 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: An improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine according to present invention and also segments of turbine casing of known art.
Figure 2: Shroud segment of present invention.
Figure 3: Sectional view of an improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine in accordance with present invention.
[027] The figure depicts 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.
DETAIL DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS OF PREFERRED EMBODIMENTS

[028] This invention provides an improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine constituting a customized shroud for covering damaged hook fit. The shroud is having length of two shroud segments thereby having longer circumference causing sufficient engagement ratio between the turbine casing hook fit portion and shroud for safe operation of the machine.
[029] Now, reference may be made to figure 1, 2 and 3.
[030] The improved shroud (100) includes a shroud segment integrated with a cover so as to cover damaged hook fit area of turbine casing.
[031] The hook type circumferential rail is integrally provided in the turbine casing.
[032] From figure 2, it can be observed that the shroud (100) of present invention is having length equivalent to length of two existing shroud segments (101).
[033] Thus, the above provision leads to increase in the hook fit engagement area. Further, the shroud segments can be customized according to hook fit damage area.
[034] Here, the cover of the shroud segment is having a shape corresponding to that of hook maintaining desired clearance from the damaged hook of the turbine casing so as to avoid interference therewith during operation of the turbine engine.
[035] The shroud segment of invention can be made of any steel without limit scope of the invention to the same. Thus, other materials readily apparent to a person skilled in the art are understood to be within purview of invention. The shroud can be manufactured by machining.
[036] With the help of the present invention, the casing is no more required to be replaced, instead shroud segments are replaced adjacent to the damaged hook area. This renders the same highly cost effective.
[037] Thus, the present invention increases the hook fit engagement area. Further, the shroud segments can be customized based on hook fit damage area.

Advantages:

- Improved hook fit contact area considering single segment.

- Damage portion located in the middle of the proposed shroud segment (100), unlike ends on current seg#22 and seg#23 (Fig.1).

- New shroud segment is made considering sum of circumferences of two existing segments leading to sufficient engagement ratio between the turbine hook fit and shroud.

- Installation of new segment in the casing along with remaining shroud segments.

- This unique solution of customized shroud segment reduces significant cost and also around ~5 month downtime if casing replacement is considered.

[038] 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.
[039] 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.
[040] 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 analogous 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”.
[041] 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.
[042] 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.
[043] 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.
[044] 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:1) An improved shroud (100) for covering hook fit damage area of turbine casing in axial flow gas turbine engine comprising of a shroud segment integrated to a cover so as to cover damaged hook fit area, wherein the shroud segment is having circumferential length equivalent to length of two existing shroud segments (101) of the turbine casing.

2) The improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine as claimed in claim 1, wherein the cover is having a profile corresponding to that of hook maintaining clearance from the damaged hook of the turbine casing so as to avoid interference therewith.

3) The improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine as claimed in claim 1 or 2, wherein the cover is placed on the inner surface of the shroud segment facing the hook of said turbine casing.

4) The improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine as claimed in the claims 1-3, wherein the shroud is having length of two shroud segments thereby having longer circumference causing sufficient engagement ratio between the turbine casing hook fit portion and shroud for safe operation of the machine.

5) The improved shroud for covering hook fit damage area of turbine casing in axial flow gas turbine engine as claimed in the claims 1-4, wherein the shroud segment can be made of any steel and can be manufactured by machining.