Piezoelectric Actuator for Gas Turbine Blade Tip Clearance Control
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Solution Overview
Problem
Gas turbine engines face inefficiencies due to varying blade tip clearances caused by differential heating, leading to suboptimal performance during different flight phases, as existing solutions like selective case cooling and radially moveable casing segments are either ineffective or mechanically complex.
Innovation Solution
A clearance control arrangement using piezoelectric material sandwiched between metal layers, actuated by a voltage source, allowing for rapid adjustment of blade tip clearance to match changing thermal conditions, with a feedback loop for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If selective case cooling is used to decrease clearance during cruise, then clearance is reduced improving efficiency, but clearance cannot be wholly minimised as the casing must be able to radially grow quickly enough to prevent blade tip rubbing during step climb manoeuvres
Solution Approach 1:
The casing is divided into multiple segments that can move independently relative to each other in the radial direction. This segmentation allows different parts of the casing to respond differently to thermal conditions, enabling rapid clearance adjustment during cruise while maintaining the ability to radially grow during transient maneuvers without requiring the entire casing to move.
Solution Approach 2:
The casing segments are designed with dynamic movement capability, allowing them to adjust their radial position in real-time based on operating conditions. This dynamic behavior enables the system to optimize clearance during steady-state cruise operations while rapidly expanding during transient step climb maneuvers to prevent blade tip rubbing.
2Loss of energy
If radially moveable segments of casing are provided to decrease clearance, then clearance control is improved, but the mechanism becomes mechanically complex and heavy requiring significant actuation components
Solution Approach 1:
Traditional mechanical actuation systems are replaced with a thermally-driven mechanism. The casing segments utilize thermal expansion and contraction of smart materials (such as shape memory alloys or piezoelectric materials) to achieve radial movement, eliminating the need for complex motors, linkages, and control mechanisms while reducing overall system weight and complexity.
Solution Approach 2:
The system changes physical parameters of the casing segment materials, specifically utilizing phase transitions or piezoelectric effects that cause dimensional changes in response to thermal or electrical stimuli. This allows the segments to change their radial position through material property changes rather than mechanical actuation, simplifying the overall mechanism.
3Loss of energy
If radially moveable segments of casing are used, then clearance can be adjusted, but the segments cannot respond rapidly enough to transient aircraft manoeuvres such as step climb
Solution Approach 1:
By replacing slow mechanical actuation systems with thermally-responsive smart materials, the system achieves rapid response times. These materials can change their dimensional properties almost instantaneously in response to thermal or electrical inputs, enabling the casing segments to rapidly expand or contract to match the speed of transient aircraft maneuvers like step climbs.
Solution Approach 2:
The casing segments incorporate materials that undergo phase transitions (such as shape memory alloys transitioning between austenite and martensite phases) in response to thermal stimuli. These phase transitions occur rapidly and produce large dimensional changes, enabling the segments to respond quickly to transient maneuvers while maintaining precise clearance control during steady-state operations.
4Reliability
If minimum clearance is specified at all flight phases as required for take off, climb and step climb, then safety is maintained, but the engine is more inefficient in cruise where clearance is larger than optimal
Solution Approach 1:
The clearance control system transitions from a static, conservative clearance specification to a dynamic, adaptive system. The casing segments continuously adjust their radial position based on real-time operating conditions, maintaining the minimum safety clearance during critical phases (takeoff, climb, step climb) while optimizing clearance to minimal values during cruise phases to maximize engine efficiency and reduce fuel consumption.
Solution Approach 2:
Different regions of the casing are given different functional qualities - some segments maintain larger clearances for safety during all conditions, while other segments dynamically adjust to minimal clearances during cruise. This local differentiation allows the system to maintain overall safety margins while optimizing performance in specific operating phases.
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
This solution enables efficient blade tip clearance control, improving engine efficiency and reducing fuel consumption by minimizing clearance during cruise phases, while maintaining sufficient clearance during transient maneuvers, thus enhancing overall engine performance and reducing costs.
Implementation Method 1
a layer of piezoelectric material that changes thickness when actuated
Data Source
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AI summary
A clearance control arrangement comprising first (48) and second (54) components defining a clearance (52) therebetween. The first component comprises a surface portion having at least a layer (50) of material that changes thickness when actuated. The clearance control arrangement also comprises a driver (60,62) to actuate the layer of material.