Variable Turbine Vane Actuation Bumper Ring
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining precise actuation of variable stator vanes due to thermal expansion differences between the engine case and unison ring, leading to binding and deformation issues under high temperature conditions.
Innovation Solution
A variable vane actuation assembly featuring a concentrically disposed unison ring, bumper ring, radial spline connection, and bumper shims, which allows the bumper ring to float radially and prevent circumferential rotation, thereby accommodating thermal expansion differences and maintaining the centricity of the unison ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If bumpers are positioned between the unison ring and the engine case to increase rigidity, then the unison ring maintains centricity, but thermal expansion of the engine case causes binding with the bumpers
Solution Approach 1:
The bumper ring is designed to float radially on the splines, allowing it to move dynamically in response to thermal expansion. This converts the static bumper connection into a dynamic system that adapts to changing dimensions, preventing binding while maintaining centricity support.
Solution Approach 2:
The radial floating mechanism allows the bumper ring's position parameter to change in response to thermal expansion of the engine case. By permitting controlled movement along the spline direction, the system accommodates dimensional changes without compromising functional performance.
2Adaptability or versatility
If the unison ring is suspended over the engine case by crank arms, then the unison ring can rotate to actuate vanes, but the unison ring deforms under actuator loads
Solution Approach 1:
The bumper ring acts as an intermediary element between the unison ring and the engine case. It provides a stable reference surface that supports the unison ring during actuation, distributing loads and preventing deformation while allowing the unison ring to rotate freely.
Solution Approach 2:
The bumper ring is pre-positioned to engage with the unison ring before actuation occurs. This preliminary support structure is in place to prevent deformation during the actuation process, ensuring the unison ring maintains its shape while rotating.
3Strength
If the engine case is made rigid to contain high pressures, then structural integrity is maintained, but thermal expansion causes the case to grow into the unison ring
Solution Approach 1:
The design explicitly accounts for thermal expansion by providing a floating radial mechanism. The splines are configured to accommodate the expected expansion of the engine case, allowing the bumper ring to move radially outward as the case grows, preventing binding and interference with the unison ring.
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 prevents deformation and binding of the unison ring, ensuring precise and consistent actuation of variable stator vanes across varying operating conditions, even under significant thermal gradients.
Implementation Method 1
the engine case undergoes greater thermal expansion than the unison ring, resulting in a greater increase in the circumference of the engine case
Data Source
AI summary
A variable vane actuation assembly for gas turbine engines having rotatable stator vanes comprises an engine casing, a unison ring, a bumper ring, a radial spline connection and a plurality of bumper shims. The engine casing is configured to encase the rotatable stator vanes. The unison ring is disposed concentrically with the engine casing. The bumper ring is disposed concentrically between the engine casing and the unison ring. The radial spline connection extends from the engine casing and joins with the bumper ring to permit the bumper ring to float radially with respect to the engine casing, but prevent the bumper ring from rotating circumferentially with respect to the engine-casing. The plurality of bumper shims are positioned between the unison ring and the bumper ring to limit deformation of the unison ring.