Combustion apparatus

Information

  • Patent Grant
  • 6470685
  • Patent Number
    6,470,685
  • Date Filed
    Friday, April 6, 2001
    23 years ago
  • Date Issued
    Tuesday, October 29, 2002
    22 years ago
Abstract
A wall structure for a gas turbine combustor arranged to have a general direction of fluid flow therethrough includes inner and outer walls defining a space therebetween. The inner wall is made up of a plurality of tiles having axial edges aligned generally with the direction of fluid flow, a gap being defined between axial edges of adjacent tiles. Orifices are provided within the axial edges to direct leakage air passing through the gaps to give the leakage air a flow component in the general direction of fluid flow through the combustor.
Description




The invention relates to a combustion apparatus for a gas turbine engine. More particularly the invention relates to a wall structure for such a combustion apparatus, and to a wall element for use therein.




A typical gas turbine engine combustor includes a generally annular chamber having a plurality of fuel injectors at an upstream head end. Combustion air is provided through the head and in addition through primary and intermediate mixing ports provided in the combustor walls, downstream of the fuel injectors.




In order to improve the thrust and fuel consumption of gas turbine engines, i.e. the thermal efficiency, it is necessary to use high compressor pressures and combustion temperatures. This results in the combustion chamber experiencing high temperatures and there is therefore a need to provide effective cooling of the combustion chamber walls. Various cooling methods have been proposed including the provision of a doubled walled combustion chamber whereby cooling air is directed into a gap between spaced outer and inner walls, thus cooling the inner wall. This air is then exhausted into the combustion chamber through apertures in the inner wall. The exhausted air forms a cooling film which flows along the hot, internal side of the inner wall, thus preventing the inner wall from overheating.




The inner wall may comprise a number of heat resistant tiles, such a construction being relatively simple and inexpensive. The tiles are generally rectangular in shape and curved to conform to the overall shape of the annular combustor wall. The tiles are conventionally longer in the circumferential direction of the combustor than in the axial direction.




The tiles are typically of cast construction, while the outer “cold” wall of the combustor wall structure is typically of sheet metal. Neither of these production methods produces components to very high tolerances and this inevitably results in gaps between adjacent tiles. It is also necessary to leave gaps between the edges of adjacent tiles, particularly the axially directed edges, in order to allow for expansion of the tiles in hot conditions. The air in the gap between the tiles and the outer cold wall is at a higher pressure than that inside the combustion chamber, and it is therefore inevitable that cooling air will leak into the combustion chamber through the axial gaps between adjacent circumferentially spaced tiles. The leaked air tends to form a relatively stiff, inwardly directed “wall” of air, which has a detrimental effect on the quality of the cool air film provided along the hot side of the tiles. As a result, overheating of the tiles may occur immediately downstream of the axial gap.




According to the present invention there is provided a wall structure for a gas turbine engine combustor arranged to have a general direction of fluid flow therethrough, the wall structure including inner and outer walls, the inner and outer walls define a space therebetween, wherein the inner wall includes a plurality of wall elements, the plurality of wall elements include axial edges aligned generally with the direction of fluid flow, a gap being defined between adjacent axial edges of adjacent tiles, and wherein means are provided for directing leakage air passing through the gaps such that the leakage air has a flow component in the general direction of fluid flow through the combustor.




Preferably at least one wall element includes a body portion and an axial edge portion, the body portion conforming to the general shape of the combustor wall structure and the axial edge portion including a member, the member extending from the body portion towards the outer wall of the combustor wall structure. The member may extend in a generally radial direction of the combustor.




The means for directing the leakage air may include at least one orifice, the at least one orifice provided in the axial edge portion of the wall element. Preferably the at least one orifice is provided in the member which extends from the body portion towards the outer wall of the combustor wall structure.




Preferably the orifices are directed at an angle of between 5° and 70° to the general direction of fluid flow through the combustor. Most preferably the orifices are directed at an angle of between 10° and 45° to the general direction of fluid flow through the combustor.




Preferably the at least one orifice lies generally parallel to the inner wall of the wall structure. The orifices may be cast into the wall element. Alternatively the orifices may be laser drilled into the wall element.




The axial edge portion may include a portion, the portion in use being overlapped by an axial edge portion of an adjacent wall element.




The wall structure may comprise at least two adjacent wall elements including peripheral edges, the edges being aligned generally across the direction of fluid flow, a gap being provided between adjacent peripheral edges of the adjacent wall elements, and wherein means are provided for directing leakage air passing through the gap such that the leakage air has a flow component in the general direction of fluid flow through the combustor. At least one wall element comprises a peripheral edge portion and a body portion, the edge portion including a member, the member extending from the body portion of the wall element towards the outer wall of the combustor wall structure, and the means for directing the leakage air may be provided within this member.




The wall element may be adapted for use in conjunction with other similar wall elements to form a wall structure.




According to the present invention there is further provided a wall element for use as part of an inner wall of a gas turbine engine combustor wall structure including inner and outer walls, the inner and outer walls defining a space therebetween, the wall element including axial edges, the axial edges aligned in use with a general direction of fluid flow through the combustor, wherein the wall element includes means associated with the axial edges for directing leakage air passing around the axial edges such that the leakage air has a flow component in the general direction of fluid flow through the combustor.




The wall element may include a body portion and an axial edge portion, the body portion conforming to the general shape of the combustor wall structure and an axial edge portion including a member, the member extending in use from the body portion towards the outer wall of the combustor wall structure, and wherein the means for directing leakage air includes at least one orifice, the at least one orifice provided in the axial edge portion of the tile.




According to the invention, there is further provided a gas turbine engine combustion chamber including a wall structure or wall element as defined in any of the preceding ten paragraphs.











Embodiments of the invention will be described for the purpose of illustration only with reference to the accompanying drawings, in which:





FIG. 1

is a schematic diagram of a ducted fan gas turbine engine having an annular combustor;





FIG. 2

is a diagrammatic cross section of an annular combustor;





FIG. 3

is a partial circumferential cross section through two adjacent combustor wall tiles, according to the prior art;





FIG. 4

is a diagrammatic view in the direction of the arrow A in

FIG. 3

;





FIG. 5

is a partial diagrammatic circumferential cross section through two adjacent combustor wall tiles, according to a first embodiment of the invention;





FIG. 6

is a diagrammatic cross section along the line


6





6


view in the direction of the arrow


6


in

FIG. 5

; and





FIG. 7

is a partial diagrammatic circumferential cross section through two adjacent combustor wall tiles, according to a second embodiment of the invention.











With reference to

FIG. 1

a ducted fan gas turbine engine generally indicated at


10


comprises, in axial flow series, an air intake


12


, a propulsive fan


14


, an intermediate pressure compressor


16


, a high pressure compressor


18


, combustion equipment


20


, a high pressure turbine


22


, an intermediate pressure turbine


24


, a low pressure turbine


26


and an exhaust nozzle


28


.




The gas turbine engine


10


works in the conventional manner so that air entering the intake


12


is accelerated by the fan


14


to produce two air flows, a first air flow into the intermediate pressure compressor


16


and a second airflow which provides propulsive thrust. The intermediate pressure compressor


16


compresses the air flow directed into it before delivering the air to the high pressure compressor


18


where further compression takes place.




The compressed air exhausted from the high pressure compressor


18


is directed into the combustion equipment


20


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


22


,


24


and


26


before being exhausted through the nozzle


28


to provide additional propulsive thrust. The high, intermediate and low pressure turbines


22


,


24


and


26


respectively drive the high and intermediate pressure compressors


16


and


18


and the fan


14


by suitable interconnecting shafts.




The combustion equipment


20


includes an annular combustor


30


having radially inner and outer wall structures


32


and


34


respectively. Fuel is directed into the combustor


30


through a number of fuel nozzles (not shown) located at the upstream end of the combustor


30


. The fuel nozzles are circumferentially spaced around the engine


10


and serve to spray fuel into air derived from the high pressure compressor


18


. The resultant fuel and air mixture is then combusted within the combustor


30


.




The combustion process which takes place within the combustor


30


generates a large amount of heat. Temperatures within the combustor may be between 1,850K and 2,600K. It is therefore necessary to ensure that the inner and outer wall structures


32


and


34


are capable of withstanding these temperatures while functioning in a normal manner. The radially outer wall structure


34


can be seen more clearly in FIG.


2


.




Referring to

FIG. 2

, the wall structure


34


includes an inner wall


36


and an outer wall


38


. The inner wall


36


comprises a plurality of discrete tiles


40


which are all of substantially the same rectangular configuration and are positioned adjacent each other. The majority of the tiles


40


are arranged to be equidistant from the outer wall


38


. Each tile is conventionally of cast construction and is longer in the circumferential direction than in the axial direction of the combustor.




The pressure of the air in a feed annulus defined between the outer wall


38


and combustor casing


39


is about 3% to 5% higher than the pressure within the combustor (perhaps 600 psi as opposed to 570 psi). The air temperature outside the combustor is about 800K to 900K. Feed holes (not illustrated) may be provided in the outer wall


38


such that high pressure, relatively cool air flows into a space


50


between the tiles


40


and the outer wall


38


. Angled effusion holes (not illustrated) may be provided within the tiles


40


such that the cooling air flows through the tiles


40


and forms a cool air film over the hot, internal surface of the tiles. This air film prevents the tiles


40


from overheating.




The cooling film flows over the tiles


40


in the general direction of fluid flow through the combustor, i.e. to the right as shown in FIG.


2


.




Referring to

FIG. 3

, the tiles


40


are provided with upstanding pedestals


51


, which extend into the gap


50


. The air within the gap


50


flows over and around the pedestals


51


, this further helping to cool the tiles


40


and prevent overheating.




Still referring to

FIG. 3

, each tile


40


includes a main body


42


which is shaped to conform to the general shape of the combustor wall structure. At an axially extending peripheral edge


40




b


of each tile, a sealing rail


44


extends from the main body


42


of the tile towards the outer wall


38


. There may be a small gap


46


between the sealing rail


44


of each tile and the outer wall


38


due to manufacturing tolerances. Adjacent sealing rails


44


of adjacent tiles


40


are located a small distance apart, resulting in a gap


48


.




Because the pressure within the space


50


between the tiles


40


and the outer wall


38


is higher than the pressure within the combustor


30


, air leaks from the space


50


through the gaps


46


and


48


into the combustor


30


. Referring to

FIG. 4

, a substantially planar “wall” of leakage air forms inwardly of the axial gap


48


. This wall of air disrupts the cooling air film provided on the inner hot side of the tiles


40


. The film is particularly disrupted in a region


54


just downstream of the axial gap





FIGS. 5 and 6

illustrate the axial sealing rail


44


of two adjacent tiles


40


according to the invention. Each sealing rail


44


is provided with a plurality of substantially cylindrical orifices


56


angled in the range of between 5° and 70° and preferably approximately 40° and 50° to the general direction of flow within the combustor


30


. The orifices


56


control the direction of flow of the leakage air, preventing it from leaving the gap


48


in a radial direction and instead causing it to flow generally along and parallel to the inner wall of the tiles


40


.




The orifices


56


prevent the formation of a sheet or wall of air internally of the axial gaps


48


and instead result in the provision of a controlled flow of air traveling generally with the existing air film. The orifices


56


also result in cooling of the sealing rails


44


, which minimizes distortion of the sealing rails and further reduces uncontrolled leakage of air.





FIG. 7

illustrates an alternative embodiment of the invention, in which a sealing rail


44


A of a tile


40


A is modified to further minimize/control leakage. The sealing rail


44


A includes an additional foot portion


58


, lying generally adjacent and parallel to the outer wall


38


in use. An adjacent tile


40


B includes a sealing rail


44


B provided with orifices


56


B similar to those illustrated in FIG.


6


. The sealing rail


44


B is able to move circumferentially relative to the foot portion


58


, by sliding over the foot portion. Thus the embodiment of

FIG. 7

still allows circumferential expansion of the tiles


40


A,


40


B but the foot portion


58


minimizes uncontrolled leakage between the outer wall


38


and the tile sealing rails


44


A,


44


B.




The orifices


56


may be formed in the tile during the casting process. Alternatively, the orifices may be cut (for example by laser drilling) into the tiles after casting or may be formed by any other manufacturing process.




There is thus provided a tile which causes the leakage air flow to have a downstream component and thus minimizes the damage that it does to the cool air film located along the inside of the inner wall. This minimizes problems of overheating caused downstream of the axial gaps between adjacent tiles. Because the leakage is controlled, it may be possible to allow relatively more of a pressure drop across the tiles


40


and relatively less across the outer wall


38


. Allowing a greater pressure drop across the tiles


40


can result in the provision of an enhanced cooling air film on the internal side of the tiles and enhanced heat removal from the external tile surface, thus minimizing the risk of the structure overheating.




Various modifications may be made to the above described embodiments without departing from the scope of the invention. The precise shapes of the tiles may be modified. In particular, the shapes and orientations of the orifices may be modified, provided that they result in the leakage air having a downstream component of flow. In tiles incorporating peripheral sealing rails along their circumferentially directed edges, orifices may also be provided in these sealing rails.




Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.



Claims
  • 1. A wall structure for a gas turbine engine combustor arranged to have a general direction of fluid flow therethrough, the wall structure including inner and outer walls, the inner and outer walls defining a space therebetween, wherein the inner wall includes a plurality of wall elements, the plurality of wall elements include axial edges, the axial edges being aligned generally with the direction of fluid flow, a gap being defined between adjacent axial edges of adjacent wall elements, and wherein means are provided for directing leakage air passing through the gaps such that the leakage air has a flow component in the general direction of fluid flow through the combustor.
  • 2. A wall structure according to claim 1 wherein at least one wall element includes a body portion and an axial edge portion, the body portion conforming to the general shape of the combustor wall structure and the axial edge portion including a member, the member extending from the body portion towards the outer wall of the combustor wall structure.
  • 3. A wall structure according to claim 2 wherein the member extends in a generally radial direction of the combustor.
  • 4. A wall structure according to claim 2 wherein the means for directing the leakage air includes at least one orifice, the at least one orifice provided in the axial edge portion of the wall element.
  • 5. A wall structure according to claim 4 wherein the at least one orifice is provided in the member which extends from the body portion towards the outer wall of the combustor wall structure.
  • 6. A wall structure according to claim 4 or claim 5 wherein the orifices are directed at an angle of between 5° and 70° to the general direction of fluid flow through the combustor.
  • 7. A wall structure according to claim 6 wherein the orifices are directed at an angle of between 10° and 45° to the general direction of fluid flow through the combustor.
  • 8. A wall structure according to claim 4 wherein the at least one orifice lies generally parallel to the inner wall of the wall structure.
  • 9. A wall structure according to claim 4 wherein the at least one orifice is cast into the wall element.
  • 10. A wall structure according to claim 4 wherein the at least one orifice is laser drilled into the wall element.
  • 11. A wall structure according to claim 2 wherein the axial edge portion includes a portion, the portion in use being overlapped by an axial edge portion of an adjacent wall element.
  • 12. A wall structure according to claim 1, wherein at least two adjacent wall elements include peripheral edges, the peripheral edges being aligned generally across the direction of fluid flow, a gap being provided between adjacent peripheral edges of the adjacent wall elements, and wherein means are provided for directing leakage air passing through the gap such that the leakage air has a flow component in the general direction of fluid flow through the combustor.
  • 13. A wall structure according to claim 12 wherein at least one wall element comprises a circumferential edge portion and a body portion, the circumferential edge portion including a member, the member extending from the body portion of the wall element towards the outer wall of the combustor wall structure and wherein the means for directing leakage air is provided within the member.
  • 14. A gas turbine engine combustion chamber including a wall structure according to claim 1.
  • 15. An elemental wall structure according to claim 1 wherein a single wall element is adapted for use in conjunction with other similar wall elements.
  • 16. A wall element for use as part of an inner wall of a gas turbine engine combustor wall structure including inner and outer walls, the inner and outer walls defining a space therebetween, the wall element including axial edges, the axial edges aligned in use with a general direction of fluid flow through the combustor, wherein the wall element includes means associated with the axial edges for directing leakage air passing around the axial edges such that the leakage air has a flow component in the general direction of fluid flow through the combustor.
  • 17. A wall element according to claim 16 wherein the wall element includes a body portion and an axial edge portion, the body portion conforming to the general shape of the combustor wall structure, the axial edge portion including a member, the member extending in use from the body portion towards the outer wall of the combustor wall structure, and wherein the means for directing leakage air includes at the least one orifice, the at least one orifice provided in the axial edge portion of the tile.
Priority Claims (1)
Number Date Country Kind
0009166 Apr 2000 GB
US Referenced Citations (5)
Number Name Date Kind
4695247 Enzaki Sep 1987 A
5216886 Ewing Jun 1993 A
5605046 Liang Feb 1997 A
5799491 Bell et al. Sep 1998 A
6029455 Sandelis Feb 2000 A
Foreign Referenced Citations (2)
Number Date Country
2 298 266 Aug 1996 GB
2 317 005 Mar 1998 GB