Combustor heat shield and method of cooling same

A combustor for a gas turbine engine includes an annular shell, an annular bulkhead connected to the shell, and a heat shield panel. The heat shield panel has a first surface facing a combustion chamber and a second surface opposite the first surface. The heat shield panel is mounted to the bulkhead and defines a cooling chamber between the bulkhead and the heat shield panel. The heat shield panel has a wall extending from the heat shield panel toward the bulkhead around at least a portion of a periphery of the heat shield panel. The wall includes a circumferential wall portion including at least one cooling air passage extending between the cooling chamber and a cavity defined between the circumferential wall portion and the shell. The at least one cooling air passage is configured to purge the cavity by directing a first cooling air stream from the cooling chamber into the cavity.

BACKGROUND

1. Technical Field

This disclosure relates generally to combustors for gas turbine engines, and more particularly to heat shields for use in a combustor.

2. Background Information

Combustors, such as those used in gas turbine engines, may generally include radially spaced inner and outer shells which define a combustion chamber therebetween. A bulkhead may be provided at the forward end of the combustion chamber to shield a forward section of the combustor from the relatively high temperatures in the combustion chamber. A heat shield including one or more heat shield panels may be mounted on the bulkhead for further heat protection. Typically, relatively cool air from outside of the combustor is used to cool the bulkhead side of the heat shield panels. This cooling air may then be directed into the combustion chamber through effusion holes in the heat shield extending between the bulkhead side and the combustion chamber side.

However, in an attempt to improve flame anchoring within the combustor, modern heat shield panels may not contain large amounts of effusion holes. Due to the nature of hot gas recirculation near the heat shield, the lack of effusion cooling holes in the heat shield panels may result in significantly increased heat shield temperatures in the mid cavity (e.g., 6 and 12 o'clock) portions of the heat shield. This high-temperature effect on the heat shield can be particularly aggravated in proximity to low-flow cavity regions disposed between the heat shield and the combustor shells.

SUMMARY

According to an embodiment of the present disclosure, a combustor for a gas turbine engine includes an annular shell, an annular bulkhead connected to the shell, and a heat shield panel. The heat shield panel has a first surface facing a combustion chamber and a second surface opposite the first surface. The heat shield panel is mounted to the bulkhead and defines a cooling chamber between the bulkhead and the heat shield panel. The heat shield panel has a wall extending from the heat shield panel toward the bulkhead around at least a portion of a periphery of the heat shield panel. The wall includes a circumferential wall portion including at least one cooling air passage extending between the cooling chamber and a cavity defined between the circumferential wall portion and the shell. The at least one cooling air passage is configured to purge the cavity by directing a first cooling air stream from the cooling chamber into the cavity.

In the alternative or additionally thereto, in the foregoing embodiment, the combustor further includes a liner panel mounted to the shell. The liner panel has a first end portion at a first end of the liner panel. The first end portion further defines the cavity.

In the alternative or additionally thereto, in the foregoing embodiment, the liner panel has a first surface facing away from the shell and a second surface opposite the first surface. The liner panel includes a liner wall extending from the second surface of the liner panel at the first end of the liner panel and contacting the shell.

In the alternative or additionally thereto, in the foregoing embodiment, the first end portion of the liner panel is configured to direct the first cooling air stream from the cavity to the first surface of the heat shield panel.

In the alternative or additionally thereto, in the foregoing embodiment, the liner panel includes at least one effusion hole directed toward the heat shield panel.

In the alternative or additionally thereto, in the foregoing embodiment, the at least one effusion hole is directed toward a radial end portion of the heat shield panel.

In the alternative or additionally thereto, in the foregoing embodiment, the heat shield panel includes an opening having an opening center axis. The opening extends through the heat shield panel between the first surface and the second surface of the heat shield panel.

In the alternative or additionally thereto, in the foregoing embodiment, the heat shield panel includes a plurality of cooling holes disposed about the opening and extending through the heat shield panel between the first surface and the second surface of the heat shield panel.

In the alternative or additionally thereto, in the foregoing embodiment, each cooling hole of the plurality of cooling holes is directed, at least in part, radially inward with respect to the opening central axis.

In the alternative or additionally thereto, in the foregoing embodiment, the heat shield panel is free of penetrations between the plurality of cooling holes and the at least one cooling air passage.

In the alternative or additionally thereto, in the foregoing embodiment, the at least one cooling air passage is a plurality of cooling air holes.

In the alternative or additionally thereto, in the foregoing embodiment, the plurality of cooling holes extend substantially perpendicularly through the circumferential wall portion.

In the alternative or additionally thereto, in the foregoing embodiment, the circumferential wall portion extends from the second surface of the heat shield panel a portion of a distance between the heat shield panel and the bulkhead.

In the alternative or additionally thereto, in the foregoing embodiment, the first cooling air stream is unobstructed between the circumferential wall portion and the shell.

According to another embodiment of the present disclosure, a combustor for a gas turbine engine includes an annular outer shell and an annular inner shell radially spaced from the outer shell. A bulkhead connects the outer shell to the inner shell. A heat shield panel has a first surface facing a combustion chamber and a second surface opposite the first surface. The heat shield panel is mounted to the bulkhead and defines a cooling chamber between the bulkhead and the heat shield panel. The heat shield panel has a wall extending from the heat shield panel toward the bulkhead around at least a portion of a periphery of the heat shield panel. The wall includes an outer circumferential wall portion and an inner circumferential wall portion. The outer circumferential wall portion includes a first at least one cooling air passage extending between the cooling chamber and an outer cavity defined between the outer circumferential wall portion and the outer shell and the inner circumferential wall portion includes a second at least one cooling air passage extending between the cooling chamber and an inner cavity defined between the inner circumferential wall portion and the inner shell. The first at least one cooling air passage is configured to purge the outer cavity by directing a first cooling air stream from the cooling chamber into the outer cavity and the second at least one cooling air passage is configured to purge the inner cavity by directing a second cooling air stream from the cooling chamber into the inner cavity.

In the alternative or additionally thereto, in the foregoing embodiment, the combustor further includes a plurality of liner panels. A first liner panel of the plurality of liner panels is mounted to the outer shell and a second liner panel of the plurality of liner panels is mounted to the inner shell. The first liner panel has a first forward end portion at a first forward end of the first liner panel. The first forward end portion further defining the outer cavity. The second liner panel has a second forward end portion at a second forward end of the second liner panel. The second forward end portion further defines the inner cavity. Each of the first liner panel and the second liner panel include at least one effusion hole directed toward the heat shield panel.

In the alternative or additionally thereto, in the foregoing embodiment, the heat shield panel includes an opening having an opening center axis, the opening extending through the heat shield panel between the first surface and the second surface of the heat shield panel, and a plurality of cooling holes disposed about the opening and extending through the heat shield panel between the first surface and the second surface of the heat shield panel. Each cooling hole of the plurality of cooling holes is directed, at least in part, radially inward with respect to the opening central axis. The heat shield panel is free of penetrations between the plurality of cooling holes and the at least one cooling air passage.

According to another embodiment of the present disclosure, a method for cooling a combustor for a gas turbine engine is provided. The method includes providing a heat shield panel mounted to a bulkhead and defining a cooling chamber between the bulkhead and the heat shield panel. The heat shield panel has a wall extending from the heat shield panel toward the bulkhead around at least a portion of a periphery of the heat shield panel. The wall includes a circumferential wall portion including at least one cooling air passage extending between the cooling chamber and a cavity defined between the circumferential wall portion and a shell connected to the bulkhead. The method further includes purging the cavity by directing a first cooling air stream, with the at least one cooling air passage, from the cooling chamber into the cavity.

In the alternative or additionally thereto, in the foregoing embodiment, the method further includes directing a second cooling air stream toward the heat shield with at least one effusion hole extending through a liner panel mounted to the shell.

In the alternative or additionally thereto, in the foregoing embodiment, the heat shield panel includes an opening having an opening center axis. The method further includes directing a third cooling air stream radially inward with respect to the opening center axis with a plurality of cooling holes extending through the heat shield.

DETAILED DESCRIPTION

It is noted that various connections are set forth between elements in the following description and in the drawings. It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. It is further noted that various method or process steps for embodiments of the present disclosure are described in the following description and drawings. The description may present the method and/or process steps as a particular sequence. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the description should not be construed as a limitation.

Referring toFIG. 1, an exemplary gas turbine engine10is schematically illustrated. The gas turbine engine10is disclosed herein as a two-spool turbofan engine that generally includes a fan section12, a compressor section14, a combustor section16, and a turbine section18. The fan section12drives air along a bypass flowpath20while the compressor section14drives air along a core flowpath22for compression and communication into the combustor section16and then expansion through the turbine section18. Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiments, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including those with three-spool architectures.

The gas turbine engine10generally includes a low spool24and a high spool26mounted for rotation about a longitudinal centerline28of the gas turbine engine10relative to an engine static structure30via one or more bearing systems32. It should be understood that various bearing systems32at various locations may alternatively or additionally be provided.

The low spool24generally includes a first shaft34that interconnects a fan36, a low-pressure compressor38, and a low-pressure turbine40. The first shaft34is connected to the fan36through a gear assembly of a fan drive gear system42to drive the fan36at a lower speed than the low spool24. The high spool26generally includes a second shaft44that interconnects a high-pressure compressor46and a high-pressure turbine48. It is to be understood that “low pressure” and “high pressure” or variations thereof as used herein are relative terms indicating that the high pressure is greater than the low pressure. An annular combustor50is disposed between the high-pressure compressor46and the high-pressure turbine48along the longitudinal centerline28. The first shaft34and the second shaft44are concentric and rotate via the one or more bearing systems32about the longitudinal centerline28which is collinear with respective longitudinal centerlines of the first and second shafts34,44.

Airflow along the core flowpath22is compressed by the low-pressure compressor38, then the high-pressure compressor46, mixed and burned with fuel in the combustor50, and then expanded over the high-pressure turbine48and the low-pressure turbine40. The low-pressure turbine40and the high-pressure turbine48rotationally drive the low spool24and the high spool26, respectively, in response to the expansion.

Referring toFIGS. 2, 3, 4A-D, and5A-C, the combustor50includes an annular outer shell52and an annular inner shell54spaced radially inward of the outer shell52, thus defining an annular combustion chamber56therebetween. An annular hood58is positioned axially forward of the outer shell52and the inner shell54and spans between and sealably connects to respective forward ends of the outer shell52and the inner shell54. It should be understood that relative positional terms, such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are relative to the normal operational attitude of the gas turbine engine10and should not be considered otherwise limiting.

A bulkhead60includes a first side62facing the combustion chamber56and a second side64opposite the first side62. The bulkhead60further includes an outer radial end66and an inner radial end68opposite the outer radial end66. The bulkhead60may be connected to and extend between the outer shell52and the inner shell54. For example, the bulkhead60may be connected to the outer shell52at the outer radial end66while the bulkhead60may be connected to the inner shell54at the inner radial end68. The bulkhead60divides the combustion chamber56and a hood chamber70. An annular heat shield72is mounted to the first side62of the bulkhead60and generally serves to thermally protect the bulkhead60and forward portions of the combustor50, such as the hood chamber70.

The heat shield72includes one or more heat shield panels74. The heat shield panel74may include a first surface76facing the combustion chamber56and a second surface78opposite the first surface76, an outer circumferential side80and an inner circumferential side82opposite the outer circumferential side80, and a first radially extending side84and a second radially extending side86opposite the first radially extending side84. Each of the first radially extending side84and the second radially extending side86may extend radially between the outer circumferential side80and the inner circumferential side82. The heat shield panel74may include an opening88extending through the heat shield panel74between the first surface76and the second surface78. The opening88may be configured to receive a mixture of fuel and air for combustion in the combustion chamber56, for example, from a fuel injector (not shown). Fuel, air, and other fluids provided by the fuel injector may pass through a swirler92which may extend through the opening88of the heat shield panel74.FIG. 4Billustrates an opening center axis94indicating a centerline axis of the opening88.

The heat shield panel74may include a wall96extending from the second surface78of the heat shield panel74toward the bulkhead60. The wall96may extend around all or a portion of a periphery of the heat shield panel74(e.g., the outer circumferential side80, the inner circumferential side82, the first radially extending side84, and the second radially extending side86). All or a portion of the wall96may contact the first side62of the bulkhead60and may form a seal between the bulkhead60and the heat shield panel74. The heat shield panel74may include one or both of an outer circumferential wall portion128, including the portion of the wall96extending along the outer circumferential side80of the heat shield panel74, and an inner circumferential wall portion130, including the portion of the wall96extending along the inner circumferential side82of the heat shield panel74. The first side62of the bulkhead60and the second surface78of the heat shield panel74may defined a cooling chamber98therebetween. To cool the heat shield panel74, relatively cool air from outside the combustor50may be directed to the second surface78of the heat shield panel74. For example, cooling air may be directed from the hood chamber70and through a plurality of impingement holes100extending through the bulkhead60such that the cooling air enters the cooling chamber98and impinges upon the second surface78of the heat shield panel74, thereby cooling the heat shield panel74. The heat shield panel74may further include one or more studs102projecting from the second surface78of the heat shield panel74for mounting the heat shield panel74to the bulkhead60.

The heat shield panel74may further include a wall104extending from the second surface78of the heat shield panel74toward the bulkhead60around all or a portion of a periphery of the opening88. All or a portion of the wall104may contact the first side62of the bulkhead60and may form a seal between the bulkhead60and the heat shield panel74further defining the cooling chamber98. In various embodiments, the heat shield panel74may include one or more rails106extending from the second surface78of the heat shield panel74toward the bulkhead60. The one or more rails106may contact the first side62of the bulkhead60and may form a seal between the bulkhead60and the heat shield panel74. Accordingly, the one or more rails106may subdivide the cooling chamber98into a plurality of cooling chambers (e.g., an outer radial cooling chamber98A and an inner radial cooling chamber98B as shown inFIG. 3).

The combustor50may include one or more liner panels108mounted to and spaced away from one or both of the outer shell52and the inner shell54. The liner panel108may include a first surface110facing the combustion chamber56and a second surface112opposite the first surface110. The second surface112of the liner panel108have be spaced from the respective shell52,54so as to define a liner cooling chamber114therebetween. The liner panel108may further include a first end116, which is a proximate end of the liner panel108with respect to the heat shield panel74, and a second end118opposite the first end116. Similar to the heat shield panel74, the liner panel108may include a liner wall120extending from the second surface112of the liner panel108toward the respective shell52,54. The liner wall120may extend around all or a portion of a periphery of the liner panel108. The liner wall120may include a first end portion122including the portion of the liner wall120extending along or proximate the first end116of the liner panel108. The first end portion122of the liner panel108may include a lip90which extends past the liner wall120(see, e.g.,FIGS. 2 and 4A). Alternatively, the first end portion122of the liner panel108may be configured without the lip90such that the liner wall120extends directly along the first end116of the liner panel108(see, e.g.,FIGS. 4B-D).

One or both of the outer shell52and the inner shell54may include a plurality of impingement holes124extending through the respective shell52,54between an exterior of the combustor50and the liner cooling chamber114of the one or more liner panels108. The plurality of impingement holes124may be configured to direct cooling air into the liner cooling chamber114so as to impinge upon the second surface112of the liner panel108, thereby cooling the liner panel108. The liner panel108may further include a plurality of effusion holes126extending through the liner panel108between the liner cooling chamber114and the combustion chamber56. Accordingly, cooling air directed into the liner cooling chamber114by the plurality of impingement holes124may then flow through the plurality of effusion holes126and may then flow along the first surface110of the liner panel108to create a film cooling layer along the first surface110.

The combustor50may include one or both of an outer cavity132and an inner cavity134. The outer cavity132may be defined, at least in part, by one or more of the outer circumferential wall portion128of the heat shield panel74, the outer shell52, the bulkhead60, and the first end portion122of the liner panel108. The inner cavity134may be defined, at least in part, by one or more of the inner circumferential wall portion130of the heat shield panel74, the inner shell54, the bulkhead60, and the first end portion122of the liner panel108.

The outer circumferential wall portion128may include at least one cooling air passage136extending between the cooling chamber98and the outer cavity132. The at least one cooling air passage136may be configured to purge the outer cavity132by directing a cooling air stream138from the cooling chamber98into the outer cavity132. Similarly, the inner circumferential wall portion130may include at least one cooling air passage140extending between the cooling chamber98and the inner cavity134. The at least one cooling air passage140may be configured to purge the inner cavity134by directing a cooling air stream142from the cooling chamber98into the inner cavity134. For example, purging one or both of the outer cavity132and the inner cavity134may include removing at least a portion of the combustor gases from the cavities132,134which are relatively hotter, on average, than the temperatures of the cooling air streams138,140. The at least one cooling air passage138,140may include, for example, holes (see, e.g.,FIGS. 3 and 5A), slots (see, e.g.,FIG. 5B), a partial-height wall, for example, a wall extending a portion of a distance between the heat shield panel74and the bulkhead60(see, e.g.,FIG. 5C), or any combination thereof. It should be understood that the at least one cooling air passages136,140may be of any suitable number, shape, or size, as appropriate. The at least one cooling air passages138,140may extend substantially perpendicularly through the respective circumferential wall portion128,130(e.g., with respect to the direction of the wall96between the heat shield panel74and the bulkhead60). Accordingly, the term “substantially”, used with respect to the orientation of the at least one cooling air passages136,140, may refer to the at least one cooling air passages136,140having an angle of 90 degrees+/−15 degrees with respect to the direction of the wall96between the heat shield panel74and the bulkhead60.

The at least one cooling air passages136,140may direct the respective cooling air streams138,142through the respective cavities132,134, for example, along exemplary cavity purge flowpaths144, as illustrated inFIG. 4B. The cooling air streams138,142may flow into and then out of the respective cavities132,134and subsequently form a cooling film along the first surface76of the heat shield panel74. The cooling air streams138,142may flow along the first surface76of the heat shield panel74in a general direction from the respective circumferential side80,82of the heat shield panel74and toward the opening88of the heat shield panel74. Accordingly, the cooling air streams138,142may provide additional cooling to the heat shield panel74, particularly in portions of the heat shield panel74subjected to higher temperatures such as the portions of the heat shield panel74that are radially disposed between the circumferential sides80,82and the opening88.

In various embodiments, one or more of the plurality of effusion holes126of the liner panel108may be directed toward the heat shield panel74. For example, the one or more of the plurality of effusion holes126directed at the heat shield panel74may be configured to direct a cooling air stream146,148toward the first surface76of the heat shield panel74. One or more of the plurality of effusion holes126may be configured to direct the cooling air stream146,148toward a radial end portion150of the first surface76of the heat shield panel74. In various embodiments, the radial end portion150may have a width W1extending between radially extending sides84,86of the heat shield panel74and a length L1from the respective circumferential side80,82that is less than or equal to 10% of a length L2of the heat shield panel74between the circumferential sides80,82. In various embodiments, the length L1from the respective circumferential side80,82may be less than or equal to 20% of a length L2of the heat shield panel74between the circumferential sides80,82. The cooling air stream146,148may further direct the respective cooling air streams138,142along the cavity purge flowpaths144so as to form the cooling film along the first surface76of the heat shield panel74. The cooling air streams146,148may combine with the respective cooling air streams138,142to form the cooling film along the first surface76of the heat shield panel74.

In various embodiments, the one or more of the plurality of effusion holes126directed toward the heat shield panel74may extend through the liner panel108between the first surface110and the second surface112(see, e.g.,FIGS. 4A and 4B), through the first end portion122of the liner wall120between the liner cooling chamber114and the combustion chamber56(see, e.g.,FIG. 4C), or a combination thereof. In various embodiments, the one or more of the plurality of effusion holes126directed toward the heat shield panel74may alternatively or additionally extend through the shells52,54(see, e.g.,FIG. 4D) which may provide a higher velocity cooling air stream146,148compared to the effusion holes126shown inFIGS. 4A-C. In various embodiments, the one or more of the plurality of effusion holes126directed toward the heat shield panel74may be disposed at an angle A2relative to the first surface110of the liner panel108, for example, between 40 and 100 degrees or between 50 and 80 degrees.

In various embodiments, the heat shield panel74may include a plurality of cooling holes152disposed about the opening88and extending through the heat shield panel74between the first surface76and the second surface78of the heat shield panel74. The plurality of cooling holes152may be disposed in rows that surround and are generally concentric to the opening88, such as one, two, three, or more rows of the plurality of cooling holes152around the opening88. The plurality of cooling holes152may be configured to direct a cooling air stream154. The plurality of cooling holes152may have an orientation that is skewed in a circumferential direction such that the plurality of cooling holes152provide a swirl effect about the opening center axis94. As shown inFIG. 4B, each cooling hole of the plurality of cooling holes152may have an orientation such that the plurality of cooling holes152are configured to direct the cooling air stream154, at least in part, in a generally radially inward direction with respect to the opening center axis94. In various embodiments, each of the plurality of cooling holes152may be proximate the opening88, for example, within 1.5 inches of the opening88or within 2.0 inches of the opening88. In various embodiments, the plurality of cooling holes152may be disposed at an angle A1relative to the first surface76of the heat shield panel74, for example, between 20 and 40 degrees or between 25 and 35 degrees.

An exemplary swirler recirculation flowpath156illustrated inFIG. 4B. The cooling air streams138,142,146,148, and154may all be generally directed in a same direction as swirler recirculation gases traveling along the swirler recirculation flowpath156, thereby strengthening flow rate of the gases traveling along the swirler recirculation flowpath156. The heat shield panel74may be free of penetrations (e.g., effusion holes) between the plurality of cooling holes152and the circumferential sides80,82and radially extending sides84,86of the heat shield panel74in order to prevent interference with the gases of the swirler recirculation flowpath156and cooling air traveling along the cavity purge flowpaths144and to improve flame anchoring within the combustor50.

While various aspects of the present disclosure have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the present disclosure. For example, the present disclosure as described herein includes several aspects and embodiments that include particular features. Although these particular features may be described individually, it is within the scope of the present disclosure that some or all of these features may be combined with any one of the aspects and remain within the scope of the present disclosure. References to “various embodiments,” “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Accordingly, the present disclosure is not to be restricted except in light of the attached claims and their equivalents.