Noise reducing stator assembly for a gas turbine engine

A stator assembly for a gas turbine engine having an axis of rotation A.sub.r and which has an annular flow path for working medium gases disposed about the axis of rotation which has a height H.sub.D, the stator assembly extending circumferentially about the axis of rotation of the engine and bounding the flow path, comprising:

• an outer wall extending circumferentially about the axis of rotation and outwardly bounding the annular flow path for working medium gases;
• an inner wall spaced radially inwardly from the outer wall, the inner wall extending circumferentially about the axis of rotation and inwardly bounding the working medium gases;
• an array of rotor blades, each rotor blade having a tip region and extending radially outwardly across the annular flow path such that the tip region is in close proximity with the outer wall, and having a chord length b.sub.r as measured in the axial direction;
• an array of a number of stator vanes spaced axially downstream from the array of rotor blades, each stator vane extending radially outwardly from the inner wall across the annular flow path and having a chord length b.sub.v as measured in the axial direction and a radial span S as measured at the leading edge, at least one of which is adapted to integrally attach an intermediate wall;
• an array of a number of struts spaced axially downstream from the array of rotor blades, each strut extending radially inwardly from the outer wall across the annular flow path and being adapted to attach an intermediate wall;
• a circumferentially extending intermediate wall spaced radially inwardly from the outer wall leaving an annular channel therebetween, the intermediate wall being integrally attached to and inwardly supported by at least one of said stator vanes extending radially across the annular flow path and being integrally attached to and outwardly supported by at least one of said struts extending across the annular channel, the intermediate wall having a length L.sub.w, and a normalized length L.sub.n that is equal to the length of the intermediate wall divided by the axial chord of the stator vane (L.sub.n =L.sub.w /b.sub.v);
• said annular channel being outwardly bounded by the outer wall and inwardly bounded by the intermediate wall and extending axially from a location disposed between the blades and vanes and said channel extending radially and circumferentially and disposed entirely within the outermost twenty percent (20%) of the working medium flow path having
• an inlet spaced axially from the trailing edge of the rotor blades such that the distance between the rotor blades and the inlet to the annular channel is less than four chord lengths (4b.sub.r) of the rotor blade,
• an axial length L.sub.C that is equal to the axial length of the intermediate wall L.sub.w (L.sub.C =L.sub.w),
• a radial height of the channel that is less than or equal to twenty percent (20%) of the height H.sub.D of the working medium flow path (H.sub.C .ltoreq.0.20 H.sub.D) perpendicular to the flow,
• a normalized height of the channel that is equal to the radial height of the channel divided by the radial span of the stator vane (H.sub.n =H.sub.C /S),
• a ratio of the actual axial length of the channel to the actual radial height of the channel being greater than 3 (L.sub.C /H.sub.C >3), wherein the inner and outer wall of the annular channel capture turbulent flow discharged into the outer portion of the flow path from the tip region of the rotor blades, and wherein the number of struts is less than the number of vanes to provide a fewer number of radially extending surfaces upon which the flow may impact.

A method for forming a flow path for working medium gases for a gas turbine engine having an axis of rotation Ar, and an outer wall extending circumferentially about the axis of rotation outwardly bounding the flow path, comprising the steps of:

• disposing a number of rotor blades in the gas turbine engine, each rotor blade having a tip region and extending across the flow path;
• disposing a number of stator vanes in the gas turbine engine spaced axially downstream from the rotor blades, each stator vane extending across the flow path;
• disposing a lesser number of struts as compared to said number of stator vanes in the gas turbine engine spaced axially downstream from the rotor blades, each strut extending across the flow path;
• disposing an intermediate wall radially inwardly from the outer wall, said intermediate wall being inwardly supported by at least one of said stator vanes and outwardly supported by at least one of said struts;
• and
• forming a channel entirely within the radially outermost twenty percent (20%) of the working medium flow path between the outer wall and intermediate wall;
• wherein sound energy discharged from the tip region of the rotor blades impacts on a number of radially extending surfaces of the struts which is less than the number of stator vanes.