Variable Vane End Wall Insert for Gas Turbine Engine
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Solution Overview
Problem
Variable cycle jet engines face challenges in minimizing gaps between rotating variable vanes and flowpath surfaces, leading to increased hot gas migration and reduced turbine performance and durability, particularly when vanes rotate within cylindrical or conical flowpaths.
Innovation Solution
A variable vane assembly with an insert between the rotating vane and the case, supported by a bearing or bushing, and sealed with a piston seal, where the insert is constructed from a different material than the vane, such as ceramic, to minimize gaps and accommodate thermal expansion, using a wave spring for sealing engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the variable vane nominal endwall gap at the outer diameter is increased to avoid clashing during rotation, then the variable vane can rotate freely without collision, but hot gas migration under the vane endwalls from the pressure side to the suction side increases, reducing turbine performance and airfoil durability
Solution Approach 1:
The endwall is segmented into a rotating portion (attached to the vane) and a stationary insert portion (fixed to the case). The stationary insert provides a stable sealing surface that does not rotate with the vane, maintaining consistent gap control and preventing hot gas migration while allowing the vane to rotate freely within the segmented structure.
Solution Approach 2:
A stationary insert acts as an intermediary element between the rotating vane and the case. This insert provides a fixed reference surface for sealing, mediating between the rotating motion requirements and the sealing requirements. The insert includes features like grooves and seals that actively prevent hot gas migration while allowing vane rotation.
2Adaptability or versatility
If the variable vane rotates within conical inner and/or outer diameter flowpaths, then the engine can accommodate variable cycle requirements, but the gap between the vane endwall edges and flowpath surfaces increases, causing severe hot gas migration and performance loss
Solution Approach 1:
The stationary insert is designed with dynamic features including grooves that can accommodate seal elements and flexible sealing surfaces that can adapt to the conical flowpath geometry. The insert remains stationary while the vane rotates, allowing the sealing features to maintain contact and prevent hot gas migration throughout the rotation range required for variable cycle operation.
Solution Approach 2:
The stationary insert provides localized sealing quality at critical locations where hot gas migration occurs. The insert includes specific features such as grooves, seals, and surface finishes tailored to the local requirements of the conical flowpath, concentrating sealing effectiveness at the interface between the rotating vane and the stationary case structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces leakage and hot gas migration, enhancing turbine performance and durability by eliminating gaps between the vane and the flowpath surfaces, thereby improving overall engine efficiency and part life.
Implementation Method 1
a wave spring, which seals the insert with respect to the case
Implementation Method 2
a piston seal is received in the groove and engages the bore
Data Source
Figure 1
Figure 2~4B
Figure 5A~5B
AI summary
A variable vane assembly for a gas turbine engine (20) includes a case (70; 170) having a bore (89) and a recess (103). The case (70; 170) provides a first portion of a flow path surface. A vane (78) includes a journal (90) that extends along an axis from a vane end (114; 214) and received in the bore (89). An insert (104; 204) is arranged in the recess (103) and provides a second portion of the flow path surface adjacent to the first flow path surface. The insert (104; 204) includes a pocket (110; 210) that slidably receives the vane end (114; 214). The vane end (114; 214) is configured to move axially relative to the insert (104; 204).