Variable Flowpath Casing for Turbine Blade Tip Clearance
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Solution Overview
Problem
Turbine engines face challenges in maintaining optimal tip clearance between rotor blades and casings due to differential thermal expansion of materials, leading to performance losses, blade rubbing, and structural damage, which affect aerodynamic efficiency and stability.
Innovation Solution
A variable flowpath casing with a flexible component that adjusts tip clearance through actuators and linkages, allowing for material-independent control of blade-tip-to-casing clearance, using facesheets, dampers, and abradable layers to manage thermal and mechanical loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed rigid casing is used, then manufacturing precision and structural strength are improved, but the ability to accommodate thermal expansion and maintain optimal tip clearance deteriorates
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a fixed rigid casing to a variable flowpath casing with movable facesheets that can adjust their position. The facesheets are coupled to the casing via hinge rods and slider links, allowing them to move axially and radially to accommodate thermal expansion and maintain optimal tip clearance between rotor blades and the casing throughout the thermal cycle.
Solution Approach 2:
The patent applies parameter changes by enabling the casing geometry to change dynamically. The movable facesheets alter the internal flowpath volume and cross-sectional area in response to thermal and mechanical conditions. This allows the casing to adapt its shape and dimensions to compensate for differential thermal expansion between the casing and rotor blade materials.
2Loss of energy
If tip clearance is reduced to improve aerodynamic efficiency, then performance losses are reduced, but the risk of blade rubbing and structural damage increases
Solution Approach 1:
The variable flowpath casing dynamically adjusts tip clearance based on operating conditions. The facesheets can move to reduce clearance during optimal operating phases to maximize aerodynamic efficiency, and simultaneously move to increase clearance during thermal expansion phases to prevent blade rubbing and structural damage.
Solution Approach 2:
The system incorporates feedback mechanisms where sensors monitor tip clearance and actuator position. The control system uses this feedback to adjust the facesheet position in real-time, maintaining optimal clearance within a defined range while preventing both excessive reduction (which causes rubbing) and excessive increase (which causes performance loss).
3Strength
If material selection is optimized for strength and thermal resistance, then structural integrity is improved, but differential thermal expansion between materials worsens
Solution Approach 1:
The patent accepts that differential thermal expansion will occur between dissimilar materials (e.g., metal rotor blades and composite or metal casing) and designs a dynamic compensation system. The movable facesheets act as a mechanical feedback mechanism that absorbs and compensates for the dimensional changes caused by differential thermal expansion, maintaining stable operational clearance despite material composition differences.
Solution Approach 2:
The patent directly addresses thermal expansion by designing the facesheet mechanism to accommodate thermal growth. The hinge rod and slider link mechanism allows the facesheets to move outward as the casing expands thermally, preventing excessive clearance loss. The abradable layer on the facesheet surface provides friction-based control to limit the movement and maintain optimal clearance within a defined range.
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 maintains optimal tip clearance, reducing performance losses, preventing blade rubbing, and minimizing damage, thereby enhancing turbine engine efficiency and stability.
Implementation Method 1
an abradable layer on an inner facesheet of the variable flowpath casing
Implementation Method 2
dampers, and abradable layers to manage thermal and mechanical loads
Data Source
AI summary
Disclosed herein are example variable flowpath casings for blade tip clearance control. An example casing for a turbine engine includes a first annular substrate extending along an axial direction; a second annular substrate positioned radially inward relative to the first annular substrate, the second annular substrate movably coupled to the first annular substrate; and an actuator coupled to the second annular substrate such that a force applied by the actuator moves the second annular substrate relative to the first annular substrate to adjust a tip clearance.