Patent Publication Number: US-9903590-B2

Title: Combustion chamber

Description:
FIELD OF THE INVENTION 
     The present invention relates to a combustion chamber, and in particular to a combustion chamber for a gas turbine engine. 
     BACKGROUND TO THE INVENTION 
     Currently double walled combustors have an inner wall comprising a plurality of tiles. The tiles have studs that are integral with the tile for attachment to an outer wall. Conventional tiles have pedestals on their outer surfaces to provide cooling of the tiles. 
     Advances in gas turbine engine technology have resulted in an increase in temperature with increasing focus on emissions regulations, and consequently the pedestal cooling arrangement of the tiles may be superseded by an impingement effusion cooling arrangement of the tiles. 
     Tiles with an impingement effusion cooling arrangement have an array of effusion cooling holes arranged at a relatively low angle, typically twenty degrees, to the tile surface. Forming these holes at the angle required leads to manufacturing difficulties, due to the clash between a laser head and the protruding studs. As a consequence, the resulting tile either has a significant area around each stud that is devoid of effusion cooling holes, or alternative approach vectors have to be defined so that the laser head avoids clashing with the studs. The alternative approach requires extra programming time, extra manufacturing time, and leads to a compromise in the X and Y positioning of the effusion cooling holes on the tile surface, and the ‘a, b, c angular definition of the hole vector’. 
     In some arrangements of non-pedestal tiles the studs which are an integral part of the tile, and which protrudes through the combustor outer wall, are replaced with alternative arrangements which are disclosed in U.S. Pat. No. 5,079,915 and U.S. Pat. No. 4,085,580. In both of these arrangements the tile is provided with a threaded receptacle into which a bolt is inserted through the outer wall. The end of the receptacle abuts the internal surface of the outer wall and helps define the depth of the air flow channel which has an optimum depth to maintain a desired flow speed. Additionally, where pedestals are provided, the receptacles ensuring the pedestals abut the inner surface of the outer wall to aid heat transfer away from the combustor tile. 
     The securing arrangements described in U.S. Pat. No. 5,079,915 and U.S. Pat. No. 4,085,580 require a minimum number of thread turns to securely mount the tile on the outer wall. This may lead to the depth of the air flow channel being too great for the pedestals to make contact or the flow area being too great, thereby reducing efficiency, as more air is required for cooling, and as a consequence less air is available for diluting the combustion. 
     It is an object of the present invention to provide an improved combustion chamber. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided a combustor having a double wall structure comprising an annular inner wall and an annular outer wall, the annular outer wall having an inner surface, an outer surface and a plurality of circumferentially spaced apertures, the annular inner wall comprising a plurality of tiles, wherein the tiles have at least one interlocking member at a first circumferential end of the tile and at least one interengaging member at a second circumferential end of the tile, each interlocking member extending through a corresponding one of the circumferentially spaced apertures in the annular outer wall and resting on the outer surface of the annular outer wall, and the interengaging member at the second circumferential end of the tile engaging with the first circumferential end of an adjacent tile. 
     Optionally the at least one interlocking member extends radially from a first wall at the first circumferential end of the tile. 
     Preferably the first wall at the first circumferential end has at least one cutaway section to receive an interengaging member. 
     Preferably at least one interengaging member extends circumferentially from a second wall at the second circumferential end of the tile. 
     Preferably two interlocking members extend radially from the first wall at the first circumferential end of the tile, the first wall at the first circumferential end of the tile has two cutaway sections, and two interengaging members extending circumferentially from the second wall at the second circumferential end of the tile. 
     Optionally the tile further comprises at least one protrusion member located at a third wall of the tile. 
     The protrusion member may act as a positioning guide, wherein the protrusion member formed on the tile wall is mateably received in a corresponding blind aperture within the inner surface of the annular outer wall. 
     Optionally the annular outer wall further comprises at least one blind aperture extending into the inner surface to receive the protrusion member. 
     The blind aperture acts as a positioning guide, and may receive the corresponding protrusion member. 
     Preferably there is an interference fit between the protrusion member and the blind aperture. 
     The interference fit between the blind aperture within the inner surface of the annular outer wall and the protrusion member ensures that the tiles are aligned in both axial and circumferential planes with respect to the annular outer wall. 
     Preferably a combustor having a final tile, the final tile comprising at least one interlocking member at a first circumferential end of the final tile, or at least one interengaging member at a second circumferential end of the final tile. 
     Preferably the final tile comprising an integral stud formed at the first circumferential end or second circumferential end, the integral stud extending radially from the first circumferential end or second circumferential end. 
     The integral stud formed at the first circumferential end or at the second circumferential end extending through an aperture in the annular outer wall. 
     The at least one interlocking member may be L-shaped or any other suitable shape. the combustor may be an annular combustor, the annular outer wall being arranged around the annular inner wall, the at least one interlocking member extending radially outwardly through the corresponding one of the circumferentially spaced apertures in the annular outer wall. 
     The tile or final tile may be manufactured from a casting process. 
     Alternatively the tile or final tile may be manufactured from an additive layer manufacturing route. 
     Preferably the additive layer manufacturing route is direct laser deposition. 
     The combustor comprising a double wall structure may be a gas turbine engine combustor. 
     According to a second aspect of the present invention there is provided a combustor tile comprising a curved surface, the curved surface bounded by walls, the combustor tile comprising at least one L-shaped interlocking member at a first end of the tile, and at least one interengaging member at a second end of the tile, wherein the interengaging member extends away from the first end and the second end, and the L-shaped interlocking member extends away from the curved surface and away from the first end and the second end. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully described by way of example with reference to the accompanying drawings in which:— 
         FIG. 1  shows a turbofan gas turbine engine having a combustor. 
         FIG. 2  shows a cross section of an annular combustor. 
         FIG. 3  shows a perspective view of a part assembled outer wall structure of an annular combustor. 
         FIG. 4  shows a perspective view of a combustor tile. 
         FIG. 5  shows a cross sectional view of an outer wall of the outer wall structure. 
         FIG. 6  shows a cross sectional view of the outer wall structure. 
         FIG. 7  shows an alternative cross sectional view of the outer wall structure. 
         FIG. 8  shows a perspective view of the assembled combustor tiles. 
         FIG. 9  shows a cross sectional view taken through side elevation of the outer wall structure. 
         FIG. 10  shows a perspective view of a final combustor tile. 
         FIG. 11  shows a perspective view an alternative final combustor tile. 
         FIG. 12  shows a cross-sectional view of the outer wall structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , a ducted fan gas turbine engine generally indicated at  10  has a principal and rotational axis  11 . The ducted fan gas turbine engine  10  comprises, in axial flow series, an air intake  12 , a propulsive fan  13 , an intermediate pressure compressor  14 , a high pressure compressor  15 , combustion equipment  16 , a high pressure turbine  17 , an intermediate pressure turbine  18 , a low pressure turbine  19  and a core exhaust nozzle  20 . A nacelle  21  generally surrounds the engine  10  and defines the intake  12  and a bypass exhaust nozzle  29 . 
     The ducted gas turbine engine  10  works in the conventional manner so that air entering the intake  11  is accelerated by the fan  13  to produce two air flows: a first air flow into the intermediate pressure compressor  14  and a second air flow which passes through a bypass duct  22  and out of the bypass exhaust nozzle  29  to provide propulsive thrust. The intermediate pressure compressor  14  compresses the air flow directed into it before delivering that air to the high pressure compressor  15  where further compression takes place. 
     The compressed air exhausted from the high pressure compressor  15  is directed into the combustion equipment  16  where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low pressure turbines  17 ,  18 ,  19  before being exhausted through the core exhaust nozzle  20  to provide additional propulsive thrust. The high, intermediate and low pressure turbines  17 ,  18 ,  19  respectively drive the high and intermediate pressure compressors  15 ,  14  and the fan  13  by suitable interconnecting shafts  23 ,  24  and  25  respectively. The fan  13  is circumferentially surrounded by a structural member in the form of a fan casing  26 , which is supported by an annular array of outlet guide vanes  27 . 
     The combustion equipment  16  includes an annular combustor  28  having radially inner and outer wall structures  30  and  32  respectively, as shown in  FIG. 2 . Fuel is directed into the annular combustor  28  through a number of fuel nozzles located at the upstream end of the annular combustor  28 . The fuel nozzles are circumferentially spaced around the engine  10  and serve to spray fuel into the air supplied from the high pressure compressor  15 . The fuel is then combusted in the air in the annular combustor  28 . 
     Referring to  FIG. 2 , the radially outer wall structure  32  comprises an inner wall  34  and an annular outer wall  36 . The inner wall  34  comprises a plurality of tiles  38  each of which has substantially the same rectangular configuration, and the tiles  38  are positioned adjacent to each other. The tiles  38  are arranged in axially adjacent rows and each row comprises circumferentially adjacent tiles  38 . The tiles  38  are arranged such that the downstream edge of each tile  38  in a row is in the same plane as an adjacent tile  38 . The outer wall  36  has a plurality of impingement holes  31 , and coolant (air) delivered from the high pressure compressor  15  enters the impingement holes  31  and is directed onto an outer surface  35  of each tile  38 . The coolant flows over the outer surfaces  35  of the tiles  38  and then passes through the effusion cooling holes  33  formed through the tiles  38 , thereby providing a cooling film over an inner surface  34  of each tile  38 . 
     A part assembled radially outer wall structure  32  of the annular combustor  28  is shown in a perspective view in  FIG. 3 . The annular outer wall  36  having an inner surface  42  and an outer surface  44 . The annular inner wall  34  comprises a plurality of tiles  38  as mentioned previously.  FIG. 3  shows part of the overall assembly, only showing three tiles  38   a ,  38   b  and  38   c  of the annular inner wall  34  mounted on the annular outer wall  36 . The tiles  38   a ,  38   b  and  38   c  are mounted on the annular outer wall  36  by providing apertures through the annular outer wall  36 , and introducing interlocking members  52 , that are provided at one tile end, through the corresponding apertures. The detail of the present invention and the method of assembly will now be described. 
     A tile  38   a  is shown in a perspective view in  FIG. 4 . The tile  38   a , comprising a substantially rectangular shape and having a curved outer surface  35 . The curved outer surface  35  is bounded by mainly perpendicular walls  50  extending from the curved outer surface  35 . Each tile  38   a  having two walls  50   a  and  50   b  which extend radially outwards at first and second circumferentially spaced ends. The tile  38   a  having two further walls  50   c  and  50   d  which extend radially outwards at first and second axial edges, and thus the walls  50   a ,  50   b ,  50   c  and  50   d  fully bound the curved surface  35  of the tile  38   a.    
     Two interlocking members, or hooks,  52  extend radially and circumferentially from the first wall  50   a  at the first end of the tile  38   a . The interlocking members  52  may be L-shaped or any other suitable shape. In this arrangement the two interlocking members  52  are positioned on the first wall  50   a  near to the walls  50   c  and  50   d  at the first and second axially spaced edges. Each interlocking member  52  is positioned at the same distance from the centre of the first wall  50   a . The first wall  50   a  has two cutaway sections  54  formed and located adjacent to and inwards from the interlocking members  52 . In summary, the interlocking members  52  and cutaway sections  54  are arranged symmetrically on the first wall  50   a , whereby from the midpoint of the first wall  50   a , there is a cutaway section  54  and then an interlocking member  52 . The interlocking members  52  are an integral part of the first wall  50   a  of the tile  38   a , and are formed during the tile manufacturing process. 
     Two interengaging members, or tabs,  56  are provided on the tile  38   a  at the second wall  50   b . The interengaging members  56  extend circumferentially from the external surface of the second wall  50   b  of the tile  38   a .  FIG. 4  shows two interengaging members  56  which are positioned away from the middle of the second wall  50   b . The two interengaging members  56  at the second wall  50   b  of the tile  38   a  are in a spaced relationship with the two cutaway sections  54  formed at the opposing first wall  50   a  of the tile  38   a . The interengaging members  56  at the second wall  50   b  of the tile  38   a  are thus aligned with the corresponding cutaway sections  54  formed at the first wall  50   a . The interengaging members  56  are an integral part of the tile  38   a , and are formed during the tile manufacturing process. 
     Protrusions, or lugs,  58  are provided on each of the third and fourth walls  50   c  and  50   d  respectively. The protrusions  58  extend radially outwards from the third and fourth walls  50   c  and  50   d . The protrusions  58  are aligned longitudinally, circumferentially, with each other as shown in  FIG. 4 . Alternatively the protrusions may be located in different longitudinal, circumferential, positions on the third and fourth walls  50   c  and  50   d . If the protrusions  58  are in an aligned relationship, then there is symmetry about the longitudinal axis of the tile  38   a.    
     The annular outer wall  36  has a series of apertures  60  that extend from the inner surface  42  to the outer surface  44 . Each aperture  60  having dimensions arranged to receive an associated interlocking member  52 , and is shown in cross section in FIG.  5 . Each aperture  60  may have a tapered cross section, a chamfered or angled cross section, thus making it easier for the interlocking member  52  of the tile  38   a  to be manipulated and introduced into the aperture  60 . The exact positioning of the apertures  60  on the outer wall  36  is dependent on the corresponding positioning of the interlocking members  52  on the tiles  38   a.    
     Additionally the annular outer wall  36  has a number of blind apertures  64 , as shown in  FIG. 12 , extending radially into the inner surface  42 . During assembly of the tiles  38  onto the annular outer wall  36 , an interference fit is created between the protrusions  58  on the tiles  38  and the blind apertures  64  formed in the inner surface  42  of the annular outer wall  36 . This interference fit, or push fit, ensures that the tiles  38  are aligned in both axial and circumferential planes. 
     The next stage is to assemble each tile  38  into the annular outer wall  36 , thus forming the outer wall structure  30  of the annular combustor  28 . Each tile  38 , configured as  38   a  and shown in  FIG. 4  is held, and the interlocking members  52  at the first wall  50   a  are aligned with the corresponding apertures  60  within the annular outer wall  36 . The circumferentially extending portion and then the radially extending portion of the interlocking members  52  are manipulated through the corresponding apertures  60  within the annular outer wall  36 . The circumferentially extending portion of the interlocking members  52  are seated against the outer surface  44  of the annular outer wall  36  as shown in  FIG. 6 . In an alternative arrangement, once the interlocking members  52  are manipulated through the apertures  60  within the annular outer wall  36 , the circumferentially extending portions of the interlocking members  52  are seated within corresponding recesses and are flush with the outer surface  44  of the annular outer wall  36  as shown in  FIG. 7 . 
     The assembly of the adjacent tile  38   b  may now begin, building up the tiles  38  into an annular array of tiles  38  within the annular outer wall  36 . The previously partially fitted tile  38   a , with its first wall  50   a  mounted onto the annular outer wall  36  has its second wall  50   b  freely hanging. An adjacent tile  38   b  is held, and the interlocking members  52  at the first wall  50   a  are aligned with the corresponding apertures  60  within the annular outer wall  36 . The circumferentially extending portion and then the radially extending portion of the interlocking members  52  are manipulated through the corresponding apertures  60  within the annular outer wall  36 , and the second wall  50   b  of the adjacent tile is again freely hanging. The circumferentially extending portions of the interlocking members  52  of the adjacent tile  38  are assembled to be seated against the outer surface  44  of the annular outer wall  36 , or seated in a recess in the outer surface  44  of the annular outer wall  36 , similarly to the previously fitted tile  38   a.    
     The next part of the assembly is to mateably receive the interengaging members  56  of the previously part fitted tile  38   a  into the corresponding cutaway sections  54  of the adjacent tile  38   b . The freely hanging wall  50   b  of the previous tile  38   a  is raised by applying a small force from the tile base  46 , and manipulating the interengaging members  56  of the tile  38   a  into the corresponding cutaway sections  54  in the adjacent tile  38   b , as shown in  FIG. 8 . 
     The next stage of the assembly ensures that the longitudinal axis (corresponding with the circumferential orientation of the combustor  16  and gas turbine engine  10 ) and the lateral axis (corresponding to the axis of the combustor  16 , and gas turbine engine  10 ) of the tile  38   a  is aligned to the circumferential and axial direction of the annular outer wall  36 . The tile  38  is pressed from the base  46  to apply a radial outward force to fixedly engage the protrusion members  58  in their respective blind apertures  64  in the annular outer wall  36 . 
       FIG. 9  shows a cross section taken in direction X as shown in  FIG. 8 , through the side elevation of the assembled tiles  38   a  and  38   b  and shows the interengaging members  56  and the annular outer wall  36 . The above sequence is repeated until the final combustor tile needs to be positioned and assembled within the annular outer wall  36 . 
     The final tile  38  is generally the same as tile  38   a , and differs in the following respects. A first final combustor tile  138  is shown in  FIG. 10 . The tile  138  does not have interlocking members located at a first wall  50   a . A radially extending stud  62  extends from the first wall  50   a  and is integrally formed during the manufacturing of the tile  138 . An alternative final tile  238  is shown in  FIG. 11 . The tile  238  does not have interengaging members extending circumferentially from the second wall  50   b . Instead a radially extending stud  62  extends from the second wall  50   b , and again is integrally formed during the manufacture of tile  238 . A corresponding aperture through the annular outer wall  36  is made to receive the stud  62  for fastening the tile  138  or  238 , to the annular outer wall  36 . 
     The method of assembling final tile  138 , or  238 , will be described individually. Firstly considering tile  138  as shown in  FIG. 10 , the interengaging members  56  locate into cutaway sections  54  of the adjacent tile  38   a . The protrusion members  58  fixedly engage into respective blind apertures  64  within the inner surface  42  of the annular outer wall  36 . The tile  138  is pressed from a first wall  50   a  from the base  46 , so that the integral stud  62  is mateably received into the corresponding aperture made in the annular outer wall  36 , and the interengaging members  56  of the previous tile  38  locate in the cutaway sections  54  on the tile  138 . A fastening nut is fitted onto the protruding portion of the integral stud  62  to secure the tile  138  onto the annular outer wall  36 , thus completing the assembly of the radially outer wall structure  30 . 
     Alternatively, tile  238  may be used as the last tile to be assembled, as shown in  FIG. 11 . The interlocking members  52  are manipulated through the corresponding apertures  60  within the annular outer wall  36  in the same manner of assembly as the normal tiles  38 , as shown in  FIGS. 6 and 7 . The interengaging members  56  of the previous tile  38  locate in the cutaway sections  54  on the tile  238 . Similarly, the protrusions  58  are received into respective blind apertures within the inner surface  42  of the annular outer wall  36 . The tile  238  is pressed from a second wall  50   b  from the base  46 , so that the integral stud  62  is mateably received into a corresponding aperture made in the annular outer wall  36 . A fastening nut is fitted to the protruding portion of the integral stud  62  to secure the tile  238  onto the annular outer wall  36 , thus completing the assembly. 
     The tiles  38  described may be manufactured from a number of manufacturing routes. The tiles  38  may be manufactured using an additive layer manufacturing route, e.g. using a direct laser deposition technique. Equally the tiles  38  may be manufactured using a casting process. It is to be noted that the interlocking members  52  and the interengaging members  56  are integral with the tile, e.g. the interlocking members  52 , the interengaging members  56  and the tile  38  are one piece structures. 
     Other examples of tiles may have three interlocking members extending radially from the first wall at the first ends of the tiles, with the third interlocking member at the centre of the first wall, two cutaway sections in the first walls, and two interengaging members on the second walls of the tiles. 
     Further examples of tiles may have one interlocking member extending radially from the centre of the first walls at the first ends of the tiles, two cutaway sections in the first walls, and two interengaging members on the second walls of the tiles. 
     Additional examples of tiles may have two interlocking members extending radially from the first wall at the first ends of the tiles, one cutaway section in the centre of the first walls, and one interengaging member in the centre of the second walls of the tiles. 
     Although the present invention has been described with reference to the interlocking member, or interlocking members, extending radially from the first wall at the first end of the tile, it may be possible for the interlocking member, or interlocking members, to extend directly, radially from the outer surface of the tile at or adjacent the first end of the tile, and may be spaced from the first wall at the first end of the tile. 
     A number of advantages result from the present invention and are briefly discussed below. The number of fasteners required to assemble the tiles onto the annular outer wall is significantly reduced. Due to the reduction in the number of fasteners, there is a potential cost reduction and weight reduction. The reduction in the number of fasteners provides an assembly method which has almost eliminated the use of conventional bolt and or stud and nut type fasteners, and this may lead to a reduction in the overall assembly time. Additionally, the use of the interlocking members and interengaging members ensures that the high profile conventional fastener fixings are replaced by much lower profile fixings. The lower profile fixings provided by the present invention leads to minimal interference during further processing of the unassembled tile, and in particular makes it easier for a laser or similar tooling to produce low angle effusion cooling holes within the tiles. The effusion cooling holes may be produced in the desired position and with the required orientation. Finally, the assembly fixings are provided at the periphery of the tile, e.g. at a less intrusive position. 
     It will be understood that the invention has been described in relation to its preferred embodiments and may be modified in many different ways without departing from the scope of the invention as defined by the accompanying claims. The features of the embodiment may be interchangeable. The shape and design of the interlocking members, the interengaging members may be changed, and many different configurations are possible without moving away from the inventive concept. The shapes used within these embodiments are provided as one example. Where two interlocking members, two interengaging members or two protrusions are described, it may equally be assembled with at least one of these features. The arrangement of the double walled combustor structure is shown as an annular arrangement. The arrangement and assembly is not restricted to merely an annular combustor, and the approach of using interlocking members, interengaging members and cutaway sections to fasten a tile to a combustor wall is not restricted to a gas turbine engine combustor.