This application relates to a bearing for use in supporting a stator trunnion. This application also relates to a method of installing the bearing into a support structure.
A turbine engine typically includes multiple compressor stages. Circumferentially arranged stators are arranged axially adjacent to the compressor blades, which are supported by a rotor. Some compressors utilize variable stator vanes in which the stators are supported for rotation by an outer case. The stator vanes are actuated between multiple angular positions to change the operating characteristics of the compressor.
An outer diameter of the stator vane includes a trunnion that is supported by a bushing in the outer case. The outer case includes an axially outwardly extending boss providing a bore that receives the bushing. One typical bushing includes a two-piece construction. An outer titanium sleeve is press-fit within the bore. A transfer molded composite bearing liner, for example a braided carbon fiber polyimide resin, is arranged at the inner diameter of the titanium sleeve. The composite bearing liner provides a low friction surface for supporting the trunnion.
Excessive temperatures in the compressor significantly degrade the resin binder and thereby reduce the bushing's life. Typically, the bushing degrades by delaminating or disintegrating when subjected to sustained temperatures at these excessive temperatures. Once the bearing liner fails, the titanium sleeve begins to wear and the vane angle is affected. What is needed is a bushing with greater heat tolerance and extended life.
A stator assembly for a turbine engine includes a support structure, such as an outer case, providing a bore. A non-metallic bushing is arranged in the bore and extends radially between inner and outer diameters providing a one-piece structure. The outer diameter of the bushing engages the bore in a press-fit relationship, in one example. A stator includes a trunnion arranged within and engaging the bushing inner diameter. In one example, the non-metallic bushing is constructed from an electrographitic carbon. The bushing is installed into the bore such that an end of the bushing is generally flush with or recessed from a wall on the support structure.
These and other features of the application can be best understood from the following specification and drawings, the following of which is a brief description.
One example turbine engine 10 is shown schematically in
The engine 10 includes a low spool 12 rotatable about an axis A. The low spool 12 is coupled to a fan 14, a low pressure compressor 16, and a low pressure turbine 24. A high spool 13 is arranged concentrically about the low spool 12. The high spool 13 is coupled to a high pressure compressor 17 and a high pressure turbine 22. A combustor 18 is arranged between the high pressure compressor 17 and the high pressure turbine 22.
The high pressure turbine 22 and low pressure turbine 24 typically each include multiple turbine stages. A hub supports each stage on its respective spool. Multiple turbine blades are supported circumferentially on the hub. High pressure and low pressure turbine blades 20, 21 are shown schematically at the high pressure and low pressure turbines 22, 24. Stator vanes 26 are arranged between the different blade stages and may be of fixed or variable geometry.
Referring to
Referring to
In one example, the bushing 44 is a unified construction of a non-metallic material. The non-metallic material extends radially from an inner diameter surface 52, which engages an outer trunnion outer diameter surface 50, to an outer diameter surface 54 that engages the bore 40. In one example, the bushing 44 is constructed from an electrographitic carbon. One type of electrographitic carbon is sintered to approximately 4,000° F. during its formation. The electrographitic carbon can be brittle and subject to fracture if unsupported. To this end, it is desirable to install the bushing 44 into the bore 40 so that one or both of ends 46, 48 are supported within the bore 40.
Referring to
In operation, during installation, a sleeve 56 abuts the boss 39. A spacer 60 is arranged adjacent to the sleeve 56 opposite the boss 39. A threaded fastener 58 extends through the spacer 60, sleeve 56, bushing 44 and adapter 62. A nut 64 is secured to the fastener 58 near the adapter 62. The fastener 58 is tightened to draw the bushing 44 into the bore 40 in an interference fit. The shoulder 70 seats against the wall 72 thereby ensuring that the bushing 44 has been inserted into the bore 40 to the desired radial depth 68, thus ensuring adequate support to prevent damage. Of course, other installation tooling arrangements may be used.
Although a preferred embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.