Diffuser case assembly

A diffuser case assembly for a gas turbine engine includes a fairing disposed circumferentially about a longitudinal axis. The fairing defines a plurality of passages circumferentially spaced apart and forming at least a portion of a fluid path between a compressor and a combustor of the gas turbine engine. A diffuser frame includes a plurality of struts. Each of the plurality of struts is disposed between a pair of adjacent passages of the plurality of passages. The diffuser frame is configured to couple an inner diffuser case to an outer diffuser case.

BACKGROUND

1. Technical Field

This disclosure relates generally to gas turbine engines, and more particularly to diffuser case assemblies.

2. Background Information

During operation of a gas turbine engine, heated core gases flow from a compressor section to a combustor section where they are mixed with fuel and ignited. Elevated core gas temperatures may induce large thermal gradients on engine components in the core flowpath.

For example, during a transient acceleration from idle to takeoff power, a support structure for an inner diffuser case, forming part of the core flowpath, may rapidly reach takeoff metal temperatures. The resulting thermal gradient may create excessive stress concentrations at intersections of comparatively hotter and colder portions of the diffuser cases and associated support structure. The thermal stress concentrations are exacerbated by the need for the inner diffuser case structure to be stiff enough to support a shaft bearing of the gas turbine engine.

SUMMARY

According to an embodiment of the present disclosure, a diffuser case assembly for a gas turbine engine includes a fairing disposed circumferentially about a longitudinal axis. The fairing defines a plurality of passages circumferentially spaced apart and forming at least a portion of a fluid path between a compressor and a combustor of the gas turbine engine. A diffuser frame includes a plurality of struts. Each of the plurality of struts is disposed between a pair of adjacent passages of the plurality of passages. The diffuser frame is configured to couple an inner diffuser case to an outer diffuser case.

In the alternative or additionally thereto, in the foregoing embodiment, a space between each pair of adjacent passages of the plurality of passages defines a recessed portion of the fairing extending axially from an axial end of the fairing through a portion of the fairing.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser frame and the inner diffuser case form an integral component.

In the alternative or additionally thereto, in the foregoing embodiment, at least one of the struts is hollow.

In the alternative or additionally thereto, in the foregoing embodiment, the at least one hollow strut defines a channel extending radially through the strut.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser frame is physically independent of the fairing.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser frame is made of a first material and the fairing is made of a second material different than the first material.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser case assembly further includes at least one seal disposed between the fairing and the diffuser frame.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser case assembly further includes a sliding joint forming an interface between the fairing and the diffuser frame.

In the alternative or additionally thereto, in the foregoing embodiment, the sliding joint is configured to move radially in response to at least one of thermal expansion and contraction of the fairing in a radial direction.

In the alternative or additionally thereto, in the foregoing embodiment, the channel is configured to conduct a flow of fluid between a compartment radially outside the inner diffuser case to a compartment radially inside the inner diffuser case.

In the alternative or additionally thereto, in the foregoing embodiment, an auxiliary line extends through the channel.

In the alternative or additionally thereto, in the foregoing embodiment, the fairing is a single-piece casting.

According to another embodiment of the present disclosure, a diffuser case assembly for a gas turbine engine includes a fairing disposed circumferentially about a longitudinal axis and a diffuser frame including a plurality of hollow struts. The fairing defines a plurality of passages circumferentially spaced apart and forming at least a portion of a fluid path between a compressor and a combustor of the gas turbine engine and a space between each pair of adjacent passages of the plurality of passages. The space defines a recessed portion of the fairing extending axially from an axial end of the fairing through a portion of the fairing. Each strut of the plurality of struts defines a channel extending radially through the strut and each strut of the plurality of struts is disposed between a pair of adjacent passages of the plurality of passages. The diffuser frame is configured to couple an inner diffuser case to an outer diffuser case.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser frame and the inner diffuser case form an integral component.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser frame is physically independent of the fairing.

According to another embodiment of the present disclosure, a gas turbine engine includes an inner diffuser case, an outer diffuser case, and a diffuser case assembly coupling the inner diffuser case to the outer diffuser case. The diffuser case assembly includes a fairing disposed circumferentially about a longitudinal axis. The fairing defines a plurality of passages circumferentially spaced apart and forming at least a portion of a fluid path between a compressor and a combustor of the gas turbine engine. A diffuser frame includes a plurality of struts. Each of the plurality of struts is disposed between a pair of adjacent passages of the plurality of passages.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser frame and the inner diffuser case form an integral component.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser frame is physically independent of the fairing.

In the alternative or additionally thereto, in the foregoing embodiment, the diffuser frame is made of a first material and the fairing is made of a second material different than the first material.

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.

FIG. 1schematically illustrates a gas turbine engine10. The gas turbine engine10is disclosed herein as a two-spool turbofan that generally incorporates a fan section12, a compressor section14, a combustor section16, and a turbine section18. The fan section12drives air along a bypass flowpath B while the compressor section14drives air along a core flowpath C for compression and communication into the combustor section16then expansion through the turbine section18. Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, 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 three-spool architectures.

The gas turbine engine10generally includes a low-speed spool20and a high-speed spool22mounted for rotation about an engine central longitudinal axis24relative to an engine static structure26. It should be understood that various bearing systems at various locations may alternatively or additionally be provided.

The low-speed spool20generally includes an inner shaft28that interconnects a fan30, a low-pressure compressor32and a low-pressure turbine34. The inner shaft28is connected to the fan30through a geared architecture36to drive the fan30at a lower speed than the low-speed spool20. The high-speed spool22includes an outer shaft38that interconnects a high-pressure compressor40and high-pressure turbine42. A combustor44is arranged between the high-pressure compressor40and high-pressure turbine42.

The core airflow is compressed by the low-pressure compressor32then the high-pressure compressor40, passed through a diffuser case assembly60, mixed and burned with fuel in the combustor44, and then expanded over the high-pressure turbine42and the low-pressure turbine34. The turbines rotationally drive the respective low-speed spool20and high-speed spool22in response to the expansion.

FIG. 2illustrates a cross-sectional view of the diffuser case assembly60of the gas turbine engine10illustrating the high-pressure compressor40, the combustor44, and the core flowpath C therebetween. An exit guide vane46is positioned within the core flowpath C immediately aft of the high-pressure compressor40and alters flow characteristics of core gases exiting the high-pressure compressor40, prior to the gas flow entering the combustor44.

Referring toFIGS. 2-5, a fairing48is disposed immediately aft of the exit guide vane46and forms at least a portion of the core flowpath C (i.e., providing fluid communication) between the high-pressure compressor40and the combustor44. The fairing48is disposed circumferentially (e.g., annularly) about the longitudinal axis24ofFIG. 1. The fairing48includes a plurality of passages52extending (e.g., generally axially) through the fairing48and configured to form the core flowpath C through the fairing48between the high-pressure compressor40and the combustor44. The fairing48further includes a plurality of recessed portions50defined between adjacent passages52of the fairing48. For example, the recessed portions50may extend axially from an aft axial end (i.e., an end proximate the combustor44) of the fairing48through a portion of the fairing48. In some embodiments, each recessed portion of the plurality of recessed portions50may be disposed between each respective pair of circumferentially adjacent passages of the plurality of passages52. In some embodiments, the fairing48may be configured as a single piece, for example a single-piece casting or a fully machined component. In some other embodiments, the fairing48may be configured as a plurality of circumferential segments subsequently assembled (e.g., welded or otherwise attached together) to form the fairing48.

Annular inner and outer diffuser cases54,56radially house the fairing48. The outer diffuser case56is disposed radially outward of the fairing48. The inner diffuser case54is disposed radially inward of the fairing48. In some embodiments, the inner and outer diffuser cases54,56may extend generally axially through all or part of the compressor section14and/or the combustor section16. The inner and outer diffuser cases54,56mechanically support structures of the gas turbine engine10, for example, the inner diffuser case54may support a shaft bearing of the gas turbine engine10.

The inner diffuser case54includes a diffuser frame58which extends between and couples the inner diffuser case54and the outer diffuser case56. The inner diffuser case54, outer diffuser case56, and diffuser frame58form a diffuser case assembly60(i.e., a “cold structure” in contrast to the “hot” fairing48). In some embodiments, the diffuser frame58and the inner diffuser case54may form a single integral component.

The diffuser frame58includes a plurality of circumferentially spaced-apart struts62with each strut of the plurality of struts62configured to radially extend through the fairing48between a pair of adjacent passages of the plurality of passages52. For example, each strut of the plurality of struts62may be disposed within a respective recessed portion of the plurality of recessed portions50. In some embodiments, each pair of adjacent passages of the plurality of passages52may correspond to a respective strut of the plurality of struts62, i.e., a strut of the plurality of struts62may radially extend through the fairing48between each pair of adjacent passages of the plurality of passages52. In other embodiments, a quantity of the plurality of struts62may be less than a quantity of the plurality of passages52. For example, each strut of the plurality of struts62may radially extend through the fairing48between each other pair, each third pair, etc. of adjacent passages of the plurality of passages52or any other suitable configuration of the plurality of struts62and the plurality of passages52. This configuration may provide for simpler assembly by allowing the diffuser case assembly60to be installed and then allowing the fairing48to be installed between the plurality of struts62from the forward end (see, e.g.,FIG. 5). In some embodiments, the diffuser frame58may be physically independent of the fairing48(i.e., there is no physical contact between the diffuser frame58and the fairing48).

As shown inFIGS. 4 and 5, in some embodiments, at least one strut of the plurality of struts62may be hollow, thereby defining a channel86extending radially through the at least one hollow strut. A hollow configuration of the plurality of struts62may provide a reduction in the weight of the diffuser case assembly60. The channel86may be configured to conduct a flow of fluid (e.g., cooling air), for example, between a compartment radially outside the inner diffuser case54to a compartment radially inside the inner diffuser case54.

During operational transients of the gas turbine engine10, the fairing48may experience an increased flow of hot gases along the core flowpath C. For example, during a transient acceleration from idle to takeoff power, the increase flow of hot gases through the fairing48may cause the fairing48to rapidly increase in temperature. Separation of the core flowpath C from the diffuser case assembly60(i.e., the “cold structure”) by the fairing48may prevent the development of large thermal gradients across one or both of the diffuser case assembly60and the fairing48. As a result, the temperature of the fairing48may increase while the diffuser case assembly60remains at a more constant, lower temperature compared to the fairing48. Similarly, the fairing48may achieve a more constant, higher temperature compared to the diffuser case assembly60. Thus, thermal stress concentrations, for example, between the diffuser frame58and the inner diffuser case54or across the fairing60may be reduced as a result of the minimized thermal gradients.

The fairing48may include one or more seals68between the fairing48and the diffuser case assembly60. In the illustrated embodiment, the fairing48includes a seal68between the fairing48and the inner diffuser case54. The fairing48includes an additional seal68between the fairing48and a seal carrier84. The seals68may be configured to maintain the seal between the diffuser case assembly60and the fairing48as the fairing48expands and contracts (e.g., in a radial, axial, etc. direction), independent of the diffuser case assembly60, as a result of changes in the temperature of the fairing48. The seals68may be configured, for example, as piston seals or any other suitable type of seal. In other embodiments, the number and location of the seals68may vary according to diffuser case assembly60configuration. In some embodiments, the seal carrier84may include a retaining ring88configured to maintain the sealing function of the seal carrier84in response to radial movement of the fairing48. In some embodiments, the diffuser case assembly60may include a mixing seal70configured to provide a seal between an aft portion of the diffuser frame58and the outer diffuser case56.

The diffuser case assembly60may include at least one sliding joint72to provide a support interface between the fairing48and the diffuser case assembly60, while still allowing the fairing48to thermally expand and contract. In the illustrated embodiment, the at least one sliding joint72includes an alignment pin74extending radially inward from the diffuser frame58. The alignment pin74mates with a pin bushing76disposed on the fairing48(i.e., a pin boss configuration), thereby movably supporting the fairing48by allowing relative radial movement between the fairing48and the alignment pin74. For example, the alignment pin74may move radially within the pin bushing76in response to at least one of thermal expansion and contraction of the fairing48in a radial direction.

As discussed above, the gas turbine engine10transients may cause the fairing48to thermally expand or contract while the diffuser case assembly60maintains a more consistent and cooler temperature. Accordingly, in some embodiments, the diffuser frame58may be made from a first material while the fairing48is made from a second material, different than the first material. For example, the fairing48may be made from a high-temperature resistant material (e.g., waspaloy, nickel-based alloys, ceramics, ceramic matrix composites, etc.) while the diffuser frame58is made from a comparatively stronger material (e.g., Inconel718, titanium, etc.) for improved support and structural stiffness of the diffuser case assembly60.

In some embodiments, one or more auxiliary lines78may extend through one or both of an aperture64of the outer diffuser case56and a channel86of the plurality of struts62. For example, the at least one auxiliary line78may be a bearing service line configured to convey oil to or from a bearing of the gas turbine engine10.

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. Accordingly, the present disclosure is not to be restricted except in light of the attached claims and their equivalents.