Patent Application
20130302151
A gas turbine engine is disclosed with stator segments that are prevented from circumferentially rotating about the axis of the engine and/or along the case that holds the stator segments in place. More specifically, an anti-rotation stator segment and adjacent stator segment are disclosed that facilitate the assembly of an endless ring of stator segments or an endless ring of stator segment clusters.
A gas turbine engine includes one or more forward compressor sections for increasing the pressure of an incoming air stream. For example, a turbofan jet engine includes a low pressure compressor (LPC) disposed between fan at the inlet of the engine and a high pressure compressor (HPC). Each compressor includes alternating axial stages of rotors and stators. Each stator is disposed within a circumferential case. Each rotor may include an outer ring of rotating blades; each stator may include a ring of stator segments, with each segment including a shroud connected to an individual vane or a shroud connected to a plurality of vanes. Each shroud may include forward and aft hooks for coupling the segment to the case. More specifically, each shroud may include a forward hook that is received in a forward slot of the case. Further, each shroud may include an aft hook that is received in an aft slot of the case or a pair of aft hooks that receive a forwardly extending tab of the case.
The case may be split into forward and aft portions. For example, during assembly, each segment is inserted axially into the case by inserting the aft hook(s) of each segment into the aft slot of the aft case portion. Then, when all of the segments are installed in the aft case portion, the forward portion of the case may be axially installed by inserting the forward hooks of the stator segments into the slot of the forward portion of the case.
One problem associated with the above-described stators is the potential for axial movement of the individual stator segments within the case when a load is imposed upon the stator assembly. See, e.g., U.S. Pat. No. 7,032,904. One way to avoid axial movement of the individual stator segments is to provide non-linear or non-straight side edges of the shrouds of the individual stator segments. The side edges may be shaped so that adjacent side edges of stator vane segments will fit together in a complementary manner. However, using non-linear side edges for the shrouds of the individual stator segments creates problems when axially inserting the individual stator segments into the case. Specifically, the last vane segment of each stator to be placed in the case may only be installed radially, not axially, due to interference with the side edges of the remaining stator segments. This is problematic because of the use of the forward and aft hooks to secure the stators to the case.
As a result, there is a need for an improved stator segment design that enables all stator segments to be inserted into an endless case axially as opposed to radially and in an efficient manner.
An improved stator assembly is disclosed. The disclosed stator assembly includes an endless case coupled to a lug and which defines an axis. The case is also coupled to a plurality of stator segments for forming an endless ring of stator segments. Each stator segment includes a shroud coupled to the case and a radially inwardly extending vane. The shroud of each stator segment includes first and second opposing side edges. Each of the side edges engages an adjacent stator segment. The plurality of stator segments includes three types. First, an anti-rotation stator segment is provided that is coupled to the lug. Second, a neighbor stator segment is disposed adjacent to the anti-rotation stator segment. Finally, the plurality of stator segments includes a plurality of middle stator segments.
The first side edges of the middle stator segments are non-linear and the second side edges of the middle stator segments are also non-linear and are shaped for abuttingly engaging the first side edge of an adjacent middle stator segment. The first side edge of the anti-rotation stator segment is linear. Further, the second side edge of the neighbor stator segment is also linear for abuttingly engaging the linear first side edge of the anti-rotation stator segment. The second side edge of the anti-rotation stator segment is non-linear and shaped to abuttingly engage a first side edge of an adjacent middle stator segment. The first side of the neighbor stator segment is non-linear and is shaped to abuttingly engage a second side edge of an adjacent middle stator segment.
An improved gas turbine engine is also disclosed. The engine includes an outer shroud and a stator assembly coupled to the outer shroud. The stator assembly includes an endless case coupled to a lug and which defines an axis. The case is coupled to a plurality of stator segments for forming an endless ring of stator segments. Each stator segment includes a shroud coupled to the case and a radially inwardly extending vane. The shroud of each stator segment includes first and second opposing side edges. Each of the side edges engage an adjacent stator segment. The plurality of stator segments also includes an anti-rotation stator segment that is coupled to a lug, a neighbor stator segment disposed adjacent to the anti-rotation stator segment and a plurality of middle stator segments disposed therebetween. The first side edges of the middle stator segments are non-linear as are the second side edges of the middle stator segments. The second side edges of the middle stator segments are shaped for abuttingly engaging the first side edge of an adjacent middle stator segment in a complementary manner. The first side edge of the anti-rotation stator segment is linear. The second side edge of the neighbor stator segment is also linear for abuttingly engaging the first side edge of the anti-rotation stator segment. The second side edge of the anti-rotation stator segment is non-linear and shaped to abuttingly engage a first side edge of an adjacent middle stator segment while the first side edge of the neighbor stator segment is non-linear and shaped to abuttingly engage a second side edge of an adjacent middle stator segment.
A method for forming a stator stage of a gas turbine engine is also disclosed. The method includes providing an endless case coupled to a plurality of lugs and defining an axis. The case includes forward and aft portions that extend towards each other to form forward and aft pockets respectively. The method includes coupling the forward or aft portion of the endless case to an outer shroud of the engine. The method further includes providing a plurality of stator segment clusters. Each stator segment cluster includes an anti-rotation stator segment, a neighbor stator segment and a plurality of middle stator segments disposed therebetween. Each anti-rotation stator segment, neighbor stator segment and middle stator segment includes a shroud and a radially inwardly extending vane. The shroud of each anti-rotation stator segment, neighbor stator segment and middle stator segment includes first and second opposing side edges for engaging an adjacent stator vane segment. The first and second side edges of the middle stator segments are non-linear but are shaped for abuttingly engaging each other when inserted into the case in a side-by-side fashion. The first side edges of the anti-rotation stator segments are linear as are the second side edges of the neighbor stator segments for abuttingly engaging the first side edge of one of the anti-rotation stator segments. The second edges of the anti-rotation stator segments are non-linear and shaped to abuttingly engage the first edge of an adjacent middle stator segment the first side edges of the neighbor stator segments are non-linear and shaped to abuttingly engage the second side edge of an adjacent middle stator segment.
The method further includes axially inserting the anti-rotation stator segment of one cluster into the case at one of the lugs to couple the anti-rotation stator segment to the lug. The method further includes axially placing a middle stator segment next to the anti-rotation stator segment so the first edge of the middle stator segment abuttingly engages the second side edge of the anti-rotation stator segment. The method then further includes repeatedly and axially placing middle stator segments into the case so that the first side edge of a succeeding middle stator segment engages the second side edge of a preceding middle stator segment until a gap exists between a succeeding middle stator segment and a succeeding lug. The method then includes axially inserting the neighbor stator segment into the gap and, the method also includes axially inserting another anti-rotation stator segment into the case to couple the anti-rotation stator segment to the succeeding lug and so the second side edge of the neighbor stator segment engages the first side edge of the anti-rotation stator segment.
Referring to
The LPC 14, HPC 15, HPT 20 and LPT 17 each include a plurality of rotors, shown generally at 21, that rotate between stationary stators, shown generally at 22. The dynamic loading of each stator 22 caused by the rotors 21 can generate tangential forces or circumferential forces about the central axis 23 of the engine 10 that can approach 500 lb·f (2225 N).
Each stator assembly 22 may include three types of stator segments including a “middle” stator segment 30 as shown in
Returning to
Turning to
However, when installing the stator segments 30, 31, 32 in an endless case 54 the last segment installed to complete an endless ring of stator segments 30, 31, 32 cannot be inserted in an axial direction as indicated by the arrow 71 but, instead, must be inserted from a radial direction which is problematic, if not impossible because of the case design. To solve this problem while still enabling the middle stator segments 30 to have curved side edges 56, 57, the side edges 59, 61 of the neighbor stator segment 31 and anti-rotation stator segment 32 are straight or linear, although angled. By providing the straight or linear side edges 59, 61 in addition to the curved side edges 56, 57, 58, 59, 62, the stator segments 30, 31, 32 will resist movement in either axial direction 71 and can also be assembled in an endless case with all segments being inserted axially, as opposed to radially. Further, the planar side edges 59, 61 facilitate a simplified machining of the stator segment cluster 70 to a specific arcuate length 80. An accurate machining of s-shaped or chevron-shaped side edges is inherently more difficult and therefore is more costly.
Turning to
Thus, a stator assembly is disclosed that includes an endless case coupled to the outer shroud of a gas turbine engine. The endless case accommodates a plurality of stator segments or a plurality of stator segment clusters. Stator segments include three types. An anti-rotation stator segment that engages a lug coupled to the endless case that prevents circumferential movement of the stator segments about the endless case. The second type of stator segment includes the “neighbor” stator segments which may be inserted into the case axially between a previously installed anti-rotation stator segment and a middle stator segment. The third type of stator segments includes the middle stator segments.
The middle stator segments include shrouds with curved side edges that prevent axial movement of the stator segments when a load is imposed on the vanes. To facilitate assembly of the stator segments in the endless case or to enable each stator segment to be placed in the case from an axial direction as opposed to a radial direction, the anti-rotation stator segment includes one linear or straight side edge, although it may be angled. The “neighbor” stator segment is placed between the anti-rotation stator segment and a previously installed middle stator segment. The neighbor stator segment also has a linear or straight side edge that is angled and that abuttingly engages the linear edge of the anti-rotation segment.
Although the side edges of the middle stator segments and the curved side edges of the neighbor and anti-rotation stator segments have an S-shaped profile, other geometries and designs that will prevent axial movement of the stator segments within the case will be apparent to those skilled in the art.
