Description:TURBINE COOLING ARRANGEMENT

FIELD OF THE INVENTION
[0001] The present subject matter described herein relates to a turbines. More specifically, the present invention relates to turbine cooling arrangement for turbiners operating at above ultra supercritical steam parameters to enhnance the creep life.
BACKGROUND OF THE INVENTION
[0002] 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.
[0003] In a typical larger power station 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 of the steam into mechanical energy to rotate the turbine.
[0004] 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 utilizing these turbines which shall have input steam temperature to an extent higher than ultra super critical parameter.
[0005] For such high temperatures, steam turbine including turbine forged components such as rotors, inner and outer casings etc. are formed of exotic alloy materials apt to demonstrate desired mechanical properties at elevated temperature and pressure at inlet and exit of the turbine.
[0006] The manufacturing of such large turbine components also demand the provisions of correspondingly large manufacturing casting / forging facilities. Therefore, bimetallic large turbine components including a high temperature material section formed of a high temperature material, and a low temperature material section formed of a low temperature material is economical alternative in reducing the cost of the turbine.
[0007] To cool off these turbine components, it is required to lower the temperature of the different components at a certain level. Hitherto many ways for cooling of turbine components have been implemented for elevated working fluid temperature and pressure, among which the prominent being Internal Bypass Cooling Arrangement IBCA. This cooling arrangement is an established practice for supercritical parameter turbine generator sets for a certain temperature limit and is not found feasible for further higher temperatures.
[0008] If the same IBCA is implemented similar to existing design with modified materials grades suiting higher temperature application, the scheme of the IBCA was not found feasible due to casing/forging tonnage limitation of the manufacturing facilities globally.
[0009] In the existing art, internal cooling arrangement of the turbine components, the mid-stage steam is expanded to a lower temperature and pressure compared to main inlet steam parameters is lead towards the balancing piston. Thus, the surface temperatures are reduced which enhance the creep properties of the turbine casing by reducing creep stresses and increasing life time of the components. The cooling steam is mixed with the leak-off steam from the main inlet steam and the resulting mixed steam restored into the main High Pressure HP flowpath at a lower stage.
[0010] If internal cooling arrangement technology is applied to turbines operating above ultra supercritical steam temperature after throttling, a low temperature steam hereinafter termed as ‘cooling steam’ unless stated otherwise of around 640  20 degree celcius would be required to be extracted from main steam flowpath and fed into the annulus space between inner casing and outer casing. Exposure of the turbine outer casing to such a temperature pressure would necessitate use of exotic alloys such as but not limited to nickel alloy in the components.
[0011] As the selection of materials for turbine inner casing and turbine outer casing are governed primarily by the steam parameters they are exposed to, producing such large casings is technologically challenging and cost of producing such casings is exorbitant as compared to existing chrome grade material casting as often favorably used in turbine applications because of cost and strength factors. It is therefore decided to explore other ways of cooling turbine components to produce a cost effective and deliverable turbine design.
[0012] Further, to meet the limitations of casting tonnage, a more competitive cost effective design and requirement of higher pressure at the balance piston to balance the thrust, an externally sourced steam with controlled pressure at requisite low temperature was anticipated.
[0013] Thus there exists a need for a new turbine component cooling arrangement that can cater to the abovementioned issues without the need of selecting high cost material alternates of exotic alloys and keep the manufacturing cost of the turbine components feasible and competitive.
OBJECTS OF THE DISCLOSURE
[0014] It is therefore the object of the present disclosure to overcome the aforementioned and other drawbacks in prior arts.
[0015] It is a primary object of the present disclosure to provide a steam turbine cooling arrangement operating above supercritical steam parameters that caters to the abovementioned issues while eliminating the need of selecting high cost material of exotic alloys and keep the manufacturing cost of turbine components feasible and competitive.
[0016] These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taken into consideration with accompanying drawings in which preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
[0017] 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.
[0018] Solution to one or more drawbacks of existing technology and additional advantages are provided through 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 a part of the claimed disclosure.
[0019] The present disclosure offers a solution in the form of a steam turbine cooling arrangement operating above supercritical steam parameters that transferring a cooling steam to multiple components of a HP steam turbine. The said arrangement includes mixing of a hot steam flow and a cold steam flow by a thermal mixer upto predetermined parameters, thereby forming a cooling steam, maintaining pressure of the cooling steam by a plurality of control valves, wherein a pressurized cooling steam flow is received by an HP turbine outer casing inlet and distributing a pressurized cooling steam flow in a plurality of flow paths, wherein one part of the cooling steam flow is fed through a HP valve inlet connection, other part of the cooling steam flow is fed through overload valve inlet connection and remaining part of the cooling steam flow is fed to a balance piston.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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
[0024] 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:-
[0025] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the present disclosure may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0026] Fig. 1 illustrates the schematic view of the turbine cooling arrangemet in accordance to the present invention.
[0027] 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.
DETAIL DESCRIPTION OF INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS OF THE PREFERRED EMBODIMENTS:
[0028] While the embodiments of the disclosure are subject to various modifications and alternative forms, a specific embodiment thereof has 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 alternatives falling within the scope of the disclosure.
[0029] The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.
[0030] The present invention is related to a steam turbine cooling arrangement adequate for operating at above ultra supercritical steam parameters and is cost effective. The steam cooling arrangement caters to the cooling requirements to turbne components viz. a HP turbine outer casing, a main steam valve inlet connection, an Over Load Valve (OLV) inlet connection and a balance piston of turbine rotor.
[0031] Referring to Figure 1, the turbine cooling arrangement 100 includes the mixing of a hot steam flow 102 and a cold steam flow 103 by a thermal mixer 104 upto predetermined parameters, thereby forming a cooling medium 105.
[0032] A cooling steam 105 is extracted from the thermal mixer 104 after mixing two steam of different steam parameters. There are two different steam with different parameters that are tapped from the boiler 101. The pre determined parameters of mixed steam parameters at inlet 107 of HP turbine outer casing 106 are selected based on the material constrain and design configuration of HP turbine outer casing 106, main steam inlet connection 108 and the balance piston 109 .
[0033] The thermal mixer 104 is envisaged which brings a hot steam 102 from the boiler 101 and a cold steam 103 from the boiler 101 to desired parameters after steam mixing 105 to cool turbine components as envisaged. For Turbine Maximum Continous rating TMCR for full load operation, the designed mass flow from thermal mixer shall be based on the total mass flow required for the effective cooling of the main steam inlet connections 108, HP turbine outer casing 106 and the balance piston 109.
[0034] Further, a pressure is maintained between an external cooling admission point 107, the HP turbine outer casing 106 and the thermal mixer 104. The allowable fluctuation range of Pressure is ±10 bar and Temperature is ±10°C from rated external cooling steam parameter at respective load conditions. The external cooling pressure at the HP turbine outer casing inlet 107 is maintained greater than turbine steam flowpath entry stage pressure at location 110 in all conditions. Further there may be a pressure drop in piping and valves connecting the thermal mixer 104 and external cooling steam admission point 107 in the HP turbine outer casing 106.
[0035] Mixer control philosophy is based on the, pressure drop in pipe connection between external cooling admission point 107 in the HP turbine outer casing 106 and the thermal mixer 104. therefore the ratio of total pressure to turbine steam flowpath entry stage pressure is maintained in the thermal mixer 104 with the help of control valves 111 and pressurized mixed cooling steam 105 is received by an HP turbine outer casing inlet 107.
[0036] Steam pressure is measured by pressure transmitters mounted at the upstream of the external cooling steam valve . For measuring upstream steam temperature of the external cooling valve, thermocouples are provided. Signals from pressure transmitters and the thermocouples are taken to a digital control system (not shown in figures, inbuilt in thermal mixer 102). The said control system works based on the temperature difference recorded by the instruments, based on the difference of the temperature mixing of steam is controlled through pressure difference to maintain designed pressure range.
[0037] Pressure transmitters are provided to measure the cooling steam pressure at the upstream of admission point to the HP turbine outer casing inlet 107.
[0038] The third step 203 includes distributing the pressurized cooling steam 105 in a plurality of flow paths.
[0039] The pressurized external cooling steam flow 105 after entering the HP turbine outer casing inlet 107 is distributed in three flow paths i.e. one part 105A of the pressurized external cooling steam flow 105 is fed through HP valve inlet connection 108 in all load conditions, other part 105B of the pressurized external cooling steam flow 105 is fed through the overload valve inlet connection 112 (only during Valve wide open VWO condition) and the remaining part of the pressurized external cooling steam 105C is fed to the balance piston 109. The cooling steam flow through valve inlet connections is regulated using orifice 113 for each valve connection.
[0040] The external cooling steam 105C which is fed to the balance piston 109 is further distributed towards generator side and turbine side of balance piston 109 . One part of the external cooling steam 105C will leak as the balance piston leak-off steam 114A towords end of the balance piston 105 Generator side and other part 114B of the external cooling steam 105C mixes with a main steam leak-off 115 forming a mix steam 116 that is fed to the overload valve chamber 117.
[0041] In the present arrangement, there are suitable sealing arrangements 118 envisaged for the entire width of balance piston to minimize the steam losses for example abradable seal. Passage provided inside the HP turbine inner casing 119 to connects the OLV chamber 117 at terminal point 120 to the balance piston at location 121 .
[0042] A plurality of seal segments 118 is provided between the main steam inlet 122 and a mix steam 116 is a mixture of steam leak-off 115 and the cooling steam 114B at location 121 and seal segments 118 between the mix steam 116 and the cooling steam entry point at the balance piston location 123.
[0043] The pressure at location 121 is governed by a steam flowpath entry stage 124/OLV chamber 117 pressure hence its pressure is lesser than the main steam inlet 122 and the part of external cooling steam 105C. Therefore main steam 124 will leak from location 122 to location 121 and the cooling steam will leak towards location 121. Then, mixed steam 116 is fed to the OLV chamber 117 connected with the flowpath at location 110.
[0044] Further, at an end of the balance piston 109, balancing passage is provided to maintain HP turbine pressure. Being at lesser pressure at an end of the balance piston 109 with resepect to the external cooling pressure, other part of external cooling steam 105C leaks as the balance piston leak-off 114B.
[0045] The proposed cooling steam arrangement eliminates the turbine exposure to high temperatures which enhances the creep properties of the turbine casing and lowers the overall cost of turbine manufacturing by eliminating the necessity to use extremely cost expensive exotic alloys which comes with their own limitations of casting/forging tonnage and size.
[0046] With the help of the solution as proposed herein in the context of the present disclosure, transferring of cooling flow to the components of the HP turbine is made seamless.
[0047] The HP steam turbine can sustain high temperature and is cost effective.
[0048] 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 particular claim containing such introduced claim recitation to disclosures 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. Also, 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 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 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.”
[0049] It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present disclosure contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the disclosure, and other dimensions or geometries are possible. Also, while a feature of the present disclosure may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present disclosure. The present disclosure also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
[0050] 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.
[0051] 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.
[0052] 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”.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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 steam turbine cooling arrangement 100 operating above supercritical steam parameters, the said arrangement 100 comprising :
- a thermal mixture 104 for mixing of a hot steam flow 102 and a cold steam flow 103 upto predetermined parameters, thereby forming a cooling steam 105;
- a plurality of control valves 111 for maintaining pressure of the cooling steam 105, wherein a pressurized cooling steam flow 105 is received by an High Pressure HP turbine outer casing 106; and
- a plurality of steam paths 105A, 105B and 105C for distributing the cooling steam 105 in to different sections of the turbine wherein one part of the cooling steam 105A is fed through a main steam inlet connection 108, other part of the cooling steam flow 105B is fed through overload valve inlet connection 112 and remaining part of the cooling steam flow 105C is fed to a balance piston 109.
2. The steam turbine cooling arrangement 100 as claimed in claim 1, wherein the heat source such a steam generator 101.
3. The steam turbine cooling arrangement 100 as claimed in claim 1-2, wherein the hot steam flow 102 and the cold steam flow 103 is received by the thermal mixer 102 from an outlet and an inlet of a heat source 101.
4. The steam turbine cooling arrangement 100 as claimed in claim 1-3, wherein the predetermined parameters including temperature and pressure are selected based on a turbine outer casing 104, a valve connection and material constraints of the balance piston 105 of the steam turbine.
5. The steam turbine cooling arrangement 100 as claimed in claim 1-4, wherein the pressure at the turbine outer casing inlet 107 is maintained greater than a turbine steam flowpath at an entry stage pressure in all conditions.
6. The steam turbine cooling arrangement 100 as claimed in claim 1-5, wherein the part of the cooling steam flow 105 fed to the balance piston 109 is distributed forming a second cooling flow 116.
7. The steam turbine cooling arrangement 100 as claimed in claim 1-6, wherein a plurality of seal segments 118 is provided between the main steam inlet 122 and a mix steam 116 is a mixture of steam leak-off 115 and the cooling steam 114B at location 121 and seal segments 118 between the mix steam 116 and the cooling steam entry point at the balance piston location 123.
8. The steam turbine cooling arrangement 100 as claimed in claim 1-7, multitude of sealing arrangements 118 are envisaged for the entire width of balance piston to minimize the steam losses.