Abstract:
A novel and improved combustion liner for use in a gas turbine engine is provided in which the premixer assembly is removably fastened to the combustion liner. Apparatus and method for removably securing the premixer assembly to the combustion liner is provided. A combustor dome plate, swirler assembly and inlet ring basket are coupled together by a plurality of removable fasteners in order to increase accessibility to portions of the combustion liner for inspection and repair processes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 61/815,835, filed on Apr. 25, 2013. This application is related by subject matter to commonly-assigned U.S. Non-Provisional Patent Applications entitled REMOVABLE SWIRLER ASSEMBLY FOR A COMBUSTION LINER (Attorney Docket No. PSM-316/PSSF.199280) and SWIRLER ASSEMBLY AND STIFFENING MECHANISM FOR PREMIXER ASSEMBLY OF A GAS TURBINE COMBUSTOR (Attorney Docket No. PSM-318/PSSF.199282) and assigned to the same assignee as the present application. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention generally relates to a gas turbine combustor. More specifically, the present invention is directed towards a premixer assembly for a gas turbine combustor, where the premixer assembly is secured together by a plurality of removable fasteners. As a result, the premixer assembly enhances combustor performance and increases component life through improved assembly and disassembly techniques and improved cooling configurations. 
       BACKGROUND OF THE INVENTION 
       [0003]    In a typical gas turbine engine, a compressor having alternating stages of rotating and stationary airfoils is coupled to a turbine through an axial shaft, with the turbine also having alternating stages of rotating and stationary airfoils. The compressor stages decrease in size in order to compress the air passing therethrough. The compressed air is then supplied to one or more combustors, which mixes the air with fuel. An ignition source proximate the one or more combustors ignite the mixture, forming hot combustion gases. The expansion of the hot combustion gases drives the stages of a turbine, which is coupled to the compressor through an axial shaft. The exhaust gases can then be used as a source of propulsion, to generate steam through a heat recovery steam generator, or in powerplant operations to turn a shaft coupled to a generator for producing electricity. 
         [0004]    The combustion system of a gas turbine engine can take on a variety of configurations. A combustion system for a gas turbine engine can comprise a single combustion chamber, a plurality of individual combustion chambers spaced about the axis of the engine, a plenum-type combustion system, or a variety of other combustion systems. Depending on the engine geometry, performance requirements, and physical operating location, the exact combustor arrangement will vary. 
         [0005]    One such combustion system comprises a casing secured to the frame of the engine, a combustion liner secured within at least a part of the casing, and one or more fuel nozzles positioned within or adjacent to the combustion liner for injecting a fuel (gas, liquid, or both) into the combustion chamber. The combustion system is in fluid communication with the engine. More specifically, the casing and liner arrangement provides a way for air from the compressor to enter the combustion system, where it mixes with fuel from the one or more fuel nozzles. The fuel-air mixture is ignited by an ignition source, such as a spark igniter. Hot combustion gases travel through the combustion liner and often through one or more transition pieces and into the turbine. The transition piece is essentially a duct having a geometry that changes from the shape of the combustor to the inlet of the turbine. 
         [0006]    The combustion liner is at the center of combustor operations. The combustion liner geometry is dictated by a variety of factors including the operating parameters of the engine, performance requirements, and available geometry. While combustion liner geometries can vary, the combustion liner typically includes at least a portion for receiving fuel nozzles, for mixing fuel and air together and for containing the reaction when the fuel and air mixture is ignited. 
         [0007]    Combustion liners of the prior art have met certain performance requirements, but have also exhibited various shortcomings. For example, prior combustion liners have been primarily or exclusively welded assemblies, thereby making it difficult for operators or repair facilities to easily access all of the features of the combustion liner to be repaired. Furthermore, prior combustor designs of similar structure were capable of operating approximately 8,000 hours prior to refurbishment or replacement. In an effort to improve gas turbine engine availability, there is a strong desire in the operator community to be able to extend the timeframe between repairs, so as to reduce engine downtime and repair/overhaul costs. 
       SUMMARY 
       [0008]    In accordance with the present invention, there is provided a novel and improved combustion liner for use in a gas turbine engine. The combustion liner is generally cylindrical in shape and has an inlet end and a discharge end, opposite the inlet end. The combustion liner of the present invention further comprises a premixer assembly which is removably fastened to the combustion liner. 
         [0009]    In accordance with an embodiment of the present invention, there is provided a premixer assembly for a gas turbine combustor comprising an inlet ring basket, a plurality of swirler assemblies each having a premix tube, premix swirler in the premix tube, and a first and second mounting block positioned along the premix tube, a dome plate and a plurality of fasteners, where lugs of the inlet ring basket are positioned between a mounting block of the swirler assembly and the dome plate such that the fasteners pass through the dome plate, openings in the lugs and a hole of the mounting block so as to assemble the premixer. 
         [0010]    In accordance with another embodiment of the present invention, a method of assembling a premixer for a gas turbine combustor is disclosed. A dome plate is provided having a plurality of dome mounting holes, an inlet ring basket having a plurality of lugs, and a plurality of swirler assemblies, each having at least one mounting block and hole therein. The swirler assemblies are then inserted into the inlet ring basket and loosely retained in the radial direction by the first mounting block. The dome plate is then placed into contact with the plurality of lugs and the swirler assemblies are then inserted into the dome plate. The mounting holes of the dome plate are aligned with corresponding openings in the lugs and holes in the mounting block. A removable fastener is then placed through the fastener opening of the dome plate, the opening in the lug, and the hole in the mounting block so as to secure the dome plate, lug (inlet ring basket) and mounting block (swirler assembly) together. 
         [0011]    In accordance with yet another embodiment of the present invention, an interface joint for coupling components of a premixer assembly is disclosed. The interface joint comprises a lug of an inlet ring basket, a swirler assembly having a mounting block positioned along an outer wall of the premix tube of the swirler assembly, and a dome plate. One or more fasteners secure the lug, mounting block, and dome plate together. 
         [0012]    Additional advantages and features of the present invention will be set forth in part in a description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention. The instant invention will now be described with particular reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]    The present invention is described in detail below with reference to the attached drawing figures, wherein: 
           [0014]      FIG. 1  is a partial cross section view of a gas turbine engine of the prior art in which a combustion system in accordance with an embodiment of the present invention is capable of being used; 
           [0015]      FIG. 2  is a cross section view of a gas turbine combustor of the prior art capable of operating within the gas turbine engine of  FIG. 1 ; 
           [0016]      FIG. 3  is a perspective view of a combustion liner in accordance with an embodiment of the present invention; 
           [0017]      FIG. 4  is a cross section view of a combustion liner taken through a pilot swirler in accordance with an embodiment of the present invention; 
           [0018]      FIG. 5  is an alternate view of the cross section of  FIG. 4 , in accordance with an embodiment of the present invention; 
           [0019]      FIG. 6  is a cross section view of a combustion liner taken through the main swirler in accordance with an embodiment of the present invention; 
           [0020]      FIG. 7  is an alternate view of the cross section of  FIG. 6 , in accordance with an embodiment of the present invention; 
           [0021]      FIG. 8  is a perspective view of a main swirler portion of the combustion liner of  FIG. 3  in accordance with an embodiment of the present invention; 
           [0022]      FIG. 9  is a detailed cross section view taken through the inlet portion of the combustion liner of  FIG. 3  in accordance with an embodiment of the present invention; 
           [0023]      FIG. 10  is a partial cross section view of the main swirler portion of the combustion liner in accordance with an embodiment of the present invention; 
           [0024]      FIG. 11  is a detailed section view of the interface joint for the premixer assembly in accordance with an embodiment of the present invention; and, 
           [0025]      FIG. 12  is a flow diagram of the steps for assembling a premixer for a gas turbine combustor. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The subject matter of the present invention is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different components, combinations of components, steps, or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. 
         [0027]    Referring initially to  FIG. 1 , a gas turbine engine  100  of the prior art is depicted in partial cross section. The gas turbine engine  100  generally comprises an outer casing  102 , enveloping the main portions of the engine. A shaft  104  extends axially along an engine axis A-A and is coupled to a compressor  106  and a turbine  108 . The compressor  106  receives air through inlet region  110  and directs the air through alternating rows of rotating and stationary airfoils of decreasing size in order to compress the air as it passes therethrough, thereby increasing the temperature and pressure of the air. The compressed air is then directed through one or more combustion systems  112  where fuel and air are mixed together and ignited to form hot combustion gases. The hot combustion gases are then directed into the turbine  108  and through alternating rows of rotating and stationary airfoils of increasing size, so as to expand the fluid and convert the energy of the combustion gases into mechanical work to drive the shaft  104 . The shaft  104  may also be coupled to a shaft of an electrical generator for purposes of generating electricity (not shown). 
         [0028]      FIG. 2  discloses a cross section of a combustor  200  of a gas turbine engine of the prior art. As such, this typical gas turbine combustor  200  comprises a casing  202 , a cover  204 , one or more fuel injectors  206 , and a combustion liner  208 . A transition piece  210  connects the combustion liner  208  to an inlet of the turbine  212 . 
         [0029]    The present invention is shown in detail in  FIGS. 3-12  and discloses a new and improved premixer assembly for a combustion liner of a gas turbine engine. Referring initially to  FIGS. 3-7 , a combustion liner  300  having a premixer assembly  330  is disclosed. The combustion liner  300  comprises a generally cylindrical liner body  302  having an inlet end  304 , an outlet, or discharge end  306 , and an axis B-B extending through the combustor. The combustion liner  300  is generally cylindrical in cross section, but it is understood that the combustion liner  300  can vary in shape, have tapered sections, or sections of varying diameter. The combustion liner  300  is generally fabricated from rolled sheet metal that is welded along an axial seam and can be formed or expanded into a modified cylindrical structure depending on the specific combustion geometry. The combustion liner  300  is preferably manufactured from a high temperature alloy, such as Haynes 230, capable of withstanding elevated combustor conditions upwards of approximately 1400 degrees Fahrenheit. Alternate materials can be used such as Hastelloy-X or Inconel. 
         [0030]    The combustion liner  300  further comprises an inlet ring basket  308  secured to the generally cylindrical body  302 . The inlet ring basket  308 , as depicted in  FIG. 3-7 , consists of a series of generally axially-oriented spindles  310  coupled to a forward ring  312  and extends forward from the inlet end  304  of the combustion liner  300 . The forward ring  312  is positioned a distance from the combustion liner  300  in order to establish a mating location for a set of fuel nozzles (not shown) in order to position the fuel nozzles in the proper axial position within the combustor. 
         [0031]    Referring now to  FIGS. 9 and 10 , the inlet ring basket  308  also comprises a plurality of lugs  309  located in an annular array about the inlet ring basket  308 , with each of the lugs  309  having an opening  309 A extending through the lug  309 . The lugs  309  extend radially inward from the inlet ring basket  308  and are used in part for securing a premixer assembly  330 , as discussed in more detail below. The lugs  309  can be fabricated separately and welded to the inlet ring basket  308  or cast as part of the inlet ring basket  308 . The plurality of lugs  309  can be a fabricated component or a casting and is preferably made from a stainless steel material. 
         [0032]    More specific details of the present invention are shown in  FIGS. 6-8 ,  10  and  11 . In addition to the inlet ring basket  308  discussed above, the premixer assembly  330  also comprises a plurality of swirler assemblies  332 , each swirler assembly  332  for receiving a fuel injector. The swirler assembly  332  comprises a premix tube  342  having an inlet end  342 A and an opposing outlet end  342 B, and a longitudinal axis C-C extending therethrough. The swirler assembly  332  also comprises a premix swirler  336  positioned within the premix tube  342  where the premix swirler  336  has a plurality of turning vanes  338  for imparting a swirl to a passing flow through the premix tube  342 . For the embodiment depicted in  FIGS. 8-10 , the premix tube  342  is slightly conical, however, alternate shapes for the premix tube  342  are possible. 
         [0033]    The swirler assembly  332  also comprises two mounting blocks for securing the swirler assembly in a gas turbine combustor. A first mounting block  344  is positioned along an outer wall of the premix tube  342  proximate the inlet end  342 A of the premix tube  342 . The first mounting block  344  includes a plurality of first holes  348  located in an outer face  347  and oriented generally perpendicular to the longitudinal axis C-C of the premix tube  342 , as shown in  FIG. 8 . 
         [0034]    The swirler assembly  332  also comprises a second mounting block  346  positioned along the outer wall of the premix tube  342  and spaced an axial distance from the first mounting block  344 . The second mounting block  346  also has one or more second holes  356  extending through the second mounting block  346  in a direction generally perpendicular to the plurality of first holes  348 . 
         [0035]    A plurality of fasteners  350  and  358  are used to secure the swirler assemblies  332  to the inlet basket  308 . Fasteners  350  are used to secure the swirler assemblies  332  to the inlet basket  308  via the first mounting block  344  where the fasteners  350  are oriented generally perpendicular to the longitudinal axis C-C of the swirler assemblies  332 . Fasteners  358  are used to secure the swirler assemblies  332  to the inlet basket  308  via the second mounting block  346  where the fasteners  358  are oriented generally parallel to the longitudinal axis C-C of the swirler assemblies  332 . 
         [0036]    The premixer assembly  330  also comprises a dome plate  334  spaced an axial distance from the second mounting block  346  of each of the swirler assemblies  332 . As shown in  FIGS. 9-11 , the dome plate  334  is oriented generally parallel to the second mounting block  346  and the plurality of lugs  309 . The dome plate  334  is positioned against a face of the lugs  309 . The dome plate  334 , which can be more clearly seen in  FIGS. 10 and 11 , is a generally cylindrical plate fabricated from a stainless steel. The exact thickness of the plate can vary, but is approximately 0.350 inches thick. The dome plate  334  also comprises a large opening  370  for each swirler assembly  332  to pass therethrough, a series of fastener openings  372  for each axial fastener  358  to pass through, and a plurality of cooling holes  374 . The dome plate  334  includes numerous cooling holes  374  for directing a flow of compressed air into the combustion zone of the combustion liner  300 . For the dome plate  334  shown in  FIGS. 10 and 11 , the cooling holes  374  are oriented generally perpendicular to the dome plate  334  (the cooling holes  374  are generally parallel to the longitudinal axis C-C of the swirler assemblies  332 ). Alternatively, the cooling holes  374  could be oriented at a surface angle relative to the dome plate  334  as well as a compound angle in order to impart a swirl to the air passing through the dome plate  334  or to improve the cooling effectiveness through the dome plate  334 . The exact quantity, size, and shape of the cooling holes  374  can vary depending on the amount of compressed air to be directed through the dome plate  334  as well as to maintain a desired pressure drop into the combustion zone. 
         [0037]    Referring to  FIG. 11 , the plurality of lugs  309  of the inlet ring basket  308  are positioned axially between the mounting blocks  346  of the swirler assemblies  332  and the dome plate  334 . A plurality of fasteners  358  pass through each of the fastener openings  372  in the dome plate  334 , through the openings  309 A in the lugs  309  and through a second hole  356  in the second mounting block  346 . 
         [0038]    The main swirler assemblies  332  are positioned so as to be in fluid communication with adjacent tubes  352 , or hoovers, which pass the flow of fuel and air from the main swirler assembly  332  to the mixing zone of the combustion liner  300 . That is, the main swirler assemblies  332  are positioned so as to be adjacent to or slightly engaged in the tubes  352 . In order to ensure that the main swirler assemblies  332  are in the proper radial position in the combustion liner and dome plate  334  and thereby maintain a desired radial clearance with the tubes  352 , a plurality of stand offs  354  are located about the outer surface of the premix tubes  342 . 
         [0039]    The present invention also provides an interface joint for coupling components of a premixer assembly  330 . Referring to  FIG. 11 , the interface joint  400  comprises a lug  309  of an inlet ring basket  308 , where the lug  309  has an opening  309 A extending through the thickness of the lug  309 . The interface joint  400  also includes a swirler assembly  332  having a premix tube  342 , a premix swirler  336  and a mounting block  346  having one or more holes  356  extending through the mounting block  346  in a direction parallel to the premix tube  342 . A dome plate  334  also forms part of the interface joint  400 . More specifically, the dome plate  334 , has a plurality of cooling holes  374 , fastener openings  372 , and larger opening  370  for receiving the swirler assemblies  332 , as discussed above. The interface joint  400  also includes one or more removable fasteners  358  for securing the lug  309 , mounting block  346 , and dome plate  334  together. The fastener  358  draws the mounting block  346  and dome plate  334  towards the lug  309  of the inlet ring basket  308 . 
         [0040]    Referring now to  FIG. 12 , the present invention also provides a method  1200  of assembling a premixer for the gas turbine combustor. The method comprises the step  1202  of providing the components of the premixer including a dome plate having a plurality of fastener openings, an inlet ring basket having a plurality of lugs where each lug has an opening extending therethrough, and a plurality of swirler assemblies having mounting blocks with holes contained therein. 
         [0041]    In a step  1204 , the swirler assemblies are inserted into the inlet ring basket and loosely affixed to the first mounting block. Then, in a step  1206 , the dome plate is placed in contact with the plurality of lugs of the inlet ring basket and in a step  1208 , the swirler assemblies are inserted into the cup openings, or large openings, of the dome plate  334 . Then, in a step  1210 , the fastener opening in the dome plate, the opening in the lug, and the opening in the mounting block of the swirler assembly are all aligned together. For the embodiment shown in  FIGS. 10 and 11 , the swirler assembly has two mounting blocks, and for this embodiment, it is the second, or aft-most mounting block that is used this assembly process. 
         [0042]    Once the holes of the three components to be secured together are aligned, in a step  1212 , a removable fastener is placed through the fastener opening in the dome plate, through the opening in the lug, and through the hole in the mounting block, as shown in  FIG. 11 . The removable fastener engages a series of threads in the hole of the mounting block so as to secure the dome plate, lug, and mounting block of a swirler assembly together. This process is repeated for each of the fastener openings in the dome plate, corresponding lugs and swirler assemblies such that the dome plate and swirler assemblies are then bolted to the inlet ring basket. 
         [0043]    The present invention has been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. Alternative embodiments and required operations, such as machining of shroud faces other than the hardface surfaces and operation-induced wear of the hardfaces, will become apparent to those of ordinary skill in the art to which the present invention pertains without departing from its scope. 
         [0044]    From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the system and method. It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and within the scope of the claims.