Systems and methods involving multiple torque paths for gas turbine engines

Systems and methods involving multiple torque paths of gas turbine engines are provided. In this regard, a representative spool assembly for a gas turbine engine, which incorporates a compressor, a turbine and a gear assembly, includes: a shaft operative to be driven by the turbine; a first spool segment operative to couple the shaft to the compressor; and a second spool segment operative to couple the shaft to the gear assembly. The first spool segment and the second spool segment are not coupled to each other.

BACKGROUND

1. Technical Field

This disclosure generally relates to gas turbine engines.

2. Description of the Related Art

A gas turbine engine typically incorporates a spool that mechanically interconnects rotating components of a turbine with rotating components of a corresponding compressor. In order to accommodate axial loads of the spool, one or more thrust bearings typically are provided. Unfortunately, mechanical failure of a spool forward of the thrust bearing can decouple the load provided by the fan and compressor from the turbine, thereby resulting in an overspeed of the turbine. Such an overspeed can be severe enough to cause turbine disks and blades to fail structurally. Specifically, structural failure of a turbine disk can cause the disk to break into multiple pieces and depart the engine by penetrating a casing that surrounds the turbine. In order to alleviate this concern, turbine disks and associated blades oftentimes are designed to accommodate such overspeed conditions resulting in the use of heavier, more robust components.

SUMMARY

Systems and methods involving multiple torque paths of gas turbine engines are provided. In this regard, an exemplary embodiment of a method for reducing overspeed potential of a turbine of a gas turbine engine comprises: providing a first load to the turbine via a first torque path; providing a second load to the turbine via a second torque path; and operating the turbine such that: mechanical failure of a component defining at least a portion of the first torque path does not inhibit the second load from being applied to the turbine via the second torque path; and mechanical failure of a component defining the second torque path does not inhibit the first load from being applied to the turbine via the first torque path.

An exemplary embodiment of a spool assembly for a gas turbine engine, which includes a compressor, a turbine and a gear assembly, comprises: a shaft operative to be driven by the turbine; a first spool segment operative to couple the shaft to the compressor; and a second spool segment operative to couple the shaft to the gear assembly. The first spool segment and the second spool segment are not coupled to each other.

An exemplary embodiment of a gas turbine engine comprises: a turbine; a shaft operative to be driven by the turbine; a compressor; a first spool segment coupling the shaft to the compressor; a gear assembly; a second spool segment coupling the shaft to the gear assembly; and a fan operative to be driven by the gear assembly. The first spool segment is operative to transfer torque from the shaft to the compressor and not to the gear assembly; and the second spool segment is operative to transfer torque from the shaft to the gear assembly and not to the compressor.

DETAILED DESCRIPTION

Systems and methods involving multiple torque paths for gas turbine engines are provided. In this regard, several exemplary embodiments will be described. In particular, these embodiments incorporate the use of multiple torque paths, e.g., two such paths, that are used to transfer torque from the turbine of a gas turbine engine to other components. For example, one of the torque paths can be used for transferring torque to a compressor, while the another torque path can be used for providing torque to a gearbox, which is used to rotate a fan. Notably, use of separate torque paths can potentially prevent an overspeed condition of a turbine when one or more components defining one of the torque paths mechanically fails. That is, even if one of the torque paths experiences a mechanical failure that uncouples a load from the turbine, the component being driven by the other of the torque paths still provides a load to the turbine. In some embodiments, this ability to prevent turbine overspeed potentially allows for use of less robust, and oftentimes lighter, components in the turbine which can result in improved gas turbine engine efficiency.

Referring now in more detail to the drawings,FIG. 1is a schematic diagram depicting an exemplary embodiment of a system involving multiple torque paths. As shown inFIG. 1, system100is generally configured as a geared turbofan gas turbine engine that incorporates a compressor102, a combustion section104, a turbine106(e.g., a high pressure turbine) and a shaft108. The shaft108is mechanically coupled to rotating components of the turbine, including turbine disks (such as turbine disk112) and associated blades (such as blades114).

From the turbine, shaft108extends forward to the compressor. However, in contrast to gas turbine engines that include a single torque path for each spool, two torque paths are provided forward of a thrust bearing116. In particular, system100includes a first torque path or spool segment120and a second torque path or spool segment122. The spool segments120,122interconnect with the shaft at an intersection124located adjacent to thrust bearing116. Notably, the thrust bearing accommodates axial loads of the shaft and prevents movement of the shaft in an aft direction, i.e., toward the turbine, if the first and second spool segments were to fail.

Spool segment120is mechanically coupled to the compressor. That is, the first spool segment is mechanically coupled to compressor130, which includes blades (e.g., blade132). Notably, vanes (e.g., vein134) are interposed between the rotating sets of compressor blades.

Spool segment122is mechanically coupled to a gearbox138. Gearbox138is used to provide torque to a gear-driven fan140.

An electronic engine control (EEC)150also is provided. The EEC150receives inputs corresponding to engine operating parameters and provides corresponding outputs for controlling operation of the gas turbine engine. Although desirable, it should be noted that the EEC may not be able to adequately control rotating speed of a turbine responsive to a total failure of a spool forward of a thrust bearing. In contrast to a spool that provides a single torque path from the turbine forward of a thrust bearing, the embodiment ofFIG. 1, however, potentially alleviates this situation by dividing the torque provided by the turbine between multiple torque paths; in this case, first and second torque paths.

In this regard, reference is made to the schematic diagram ofFIG. 2, which identifies three general areas of spool108that may be subjected to mechanical failure. In particular,FIG. 2depicts location A (located aft of thrust bearing116), location B (located along spool segment120), and location C (located along spool segment122). Notably, mechanical failure of the spool at location A causes the portion of the spool aft of the failure to move axially aft. As such, the turbine blades tend to clash with the adjacent vanes. Although resulting in turbine failure, such blade clashing may reduce a tendency of the turbine to overspeed to the point of turbine disk liberation.

In contrast, mechanical failure of the first spool segment120(location B) results in load of the gearbox and the gear-driven fan being applied via the second spool segment122to the turbine. Similarly, mechanical failure of the second spool segment122(location C) results in load of the compressor being applied via the first spool segment120to the turbine. Since at least a portion of the normal operating load is still applied to the turbine via a remaining torque path despite failure of one of the spool segments, the EEC may have adequate time to respond to any sensed failure. As such, the EEC may be able to provide outputs to reduce the rotational speed of the turbine, thereby potentially avoiding a critical overspeed.

FIG. 3is a schematic diagram of another embodiment of a system involving multiple torque paths. In particular,FIG. 3schematically depicts a portion of a gas turbine engine300including a shaft302, a compressor304, a first torque path306, a second torque path308and a thrust bearing310. Note that the rotating components of the gas turbine are shaded to visually distinguish those components from other components of the gas turbine.

In operation, torque is provided from a turbine (not shown) to compressor304via shaft302and torque path306. Additionally, torque is provided from the turbine to a gearbox (not shown) via shaft302and torque path308. Note that the torque path306diverges from torque path308at an intersection312, which is located in a vicinity of the thrust bearing310.

FIG. 4is a flowchart depicting functionality of an embodiment of a system involving multiple torque paths. Specifically,FIG. 4depicts an embodiment of a method for reducing overspeed potential of a power turbine of a gas turbine engine. In this regard, the functionality (or method) may be construed as beginning at block402, in which a first load is provided to the turbine via a first torque path. In some embodiments, the first load can be associated with a compressor of the gas turbine engine. In block404, a second load is provided to the turbine via a second torque path. In some embodiments, the second load can be associated with a gear assembly of the gas turbine engine. In block406, the turbine is operated such that: mechanical failure of a component defining at least a portion of the first torque path does not inhibit the second load from being applied to the turbine via the second torque path; and mechanical failure of a component defining the second torque path does not inhibit the first load from being applied to the turbine via the first torque path.