Rotary kinetic fluid motors or pumps – Selectively adjustable vane or working fluid control means – Upstream of runner
Reexamination Certificate
1999-04-30
2001-04-03
Ryznic, John E. (Department: 3745)
Rotary kinetic fluid motors or pumps
Selectively adjustable vane or working fluid control means
Upstream of runner
C415S230000
Reexamination Certificate
active
06210106
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to aircraft gas turbine engine variable stator vanes and, more particularly, seals deposed around trunnions of such vanes.
2. Disscussion of the Background Art
A typical gas turbine engine compressor includes several rows or stages of interdigitated compressor stator vanes and corresponding rows or stages of compressor rotor blades. As ambient air flows through each succeeding compressor stage during operation, it is successively compressed for providing compressed air to a combustor located downstream therefrom, wherein it is mixed with fuel and ignited for generating hot combustion gases which power the engine. One or more rows of compressor stator vanes are variable for allowing each vane to rotate around a longitudinal or radial axis to adjust the angular orientation of the vane relative to the airflow. This improves the efficiency and overall operation of the compressor. Variable stator vanes typically include an integral outer trunnion disposed in a stator casing for allowing angular adjustment of the vane relative to the airflow thereover. In a typical compressor, the trunnion is pivotally mounted in a bushing in the casing of the compressor or in a complementary mounting boss on the casing.
One problem with current designs is that compressor air leaks through air seals around the trunnion. Aerodynamic forces, acting on the vane, orients the vane into a cocked position opening up or increasing area of a leakage path. The leakage path allows compressed hot air to flow by the bushing degrading the bushing by oxidation of the resin system. One type of bushing material is a high temperature polyamide composite laminates. The high temperature air leak can exceed 700 degrees F in some applications and decompose the polyamide bushing materials causing severe bushing degradation due to erosion and oxidation of the resin matrix. This in turn leads to further degradation due to loss of the fiber because of fatigue failure. Manufacturing tolerances and maintenance practices are also known to causes larger leakage passages. Therefore, it is highly desirable to improve sealing effectiveness of variable vane assemblies having a trunnion and a bushing between the trunnion and the engine casing.
SUMMARY OF THE INVENTION
The present invention provides a sealing apparatus for sealing a gas turbine engine variable vane rotatably supported by an engine casing circumscribed about an engine centerline. The apparatus includes a trunnion of the variable vane rotatable about a trunnion axis, radially spaced apart inner and outer casing bores circumscribed about the trunnion axis and disposed radially outward of the engine centerline through the casing, and the trunnion rotatably disposed within the inner and outer casing bores. The inner bore is wider than the outer bore forming an annular shoulder with a planar radially inwardly facing shoulder surface. An annular recess in the trunnion has a planar radially inwardly facing recess surface substantially co-planar with the shoulder surface. A sealing ring is radially slidably disposed about the trunnion below the outer recess surface and has a radially outwardly facing sealing surface substantially co-extensive in a direction perpendicular to the trunnion axis and sealable with both the outer recess surface and the shoulder surface.
ADVANTAGES OF THE INVENTION
The present invention improves performance of the compressor and engine, durability of the bushing materials, and reliability of the compressor. The invention prevents or reduces leakage of high temperature air around the bushings at a high rate. This, in turn, prevents or reduces oxidization of the resin in composite bushing materials which would otherwise allow high pressure air from escaping the compressor causing loss of efficiency, loss of Exhaust Gas Temperature (EGT) margin, and reduction of Specific Fuel Consumption (SFC).
The present invention provides good sealing at the trunnion and accommodates cocking of the vane due to aerodynamic forces imparted on the vane during engine operation. The present invention provides good sealing at the trunnion and accommodates large variations in sealing effectiveness between the bushing and the engine casing due to manufacturing tolerances and maintenance practices.
REFERENCES:
patent: 4990056 (1991-02-01), McClain et al.
patent: 5039277 (1991-08-01), Naudet
patent: 5277544 (1994-01-01), Naudet
patent: 5324165 (1994-06-01), Charbonnel et al.
General Electric Company
Herkamp Nathan D.
Hess Andrew C.
Ryznic John E.
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