Soft-lead Capacitance Probe for Gas Turbine Blade Tip Clearance
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Solution Overview
Problem
Existing systems for monitoring blade tip clearances in gas turbine engines face challenges in accurately measuring distances due to thermal expansion and the limitations of sensor size and weight, leading to potential inefficiencies such as increased turbulence and internal drag.
Innovation Solution
A capacitance probe system with a circuit board sensor and soft leads embedded in a thermally conforming liner, allowing for accurate measurement of blade tip clearances while accommodating thermal expansion, with minimal increase in size and weight, using capacitors and an insulating material within a conductive housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional hard lead sensor is used for monitoring blade tip clearance, then the sensor structure is rigid and easy to manufacture, but the sensor cannot accommodate thermal expansion and adds excessive weight and size
Solution Approach 1:
The patent uses a soft lead instead of a traditional hard lead, allowing the sensor to flex and accommodate thermal expansion of the turbine engine components. The soft lead is embedded in the turbine blade, enabling the sensor to move with the blade during thermal cycling while maintaining electrical connection for capacitance measurement.
Solution Approach 2:
The patent changes the physical state of the lead from rigid to soft/flexible, allowing it to deform elastically in response to thermal expansion. This parameter change enables the sensor to maintain measurement accuracy while accommodating dimensional changes in the engine components during operation.
2Measurement precision
If a traditional hard lead sensor is used for monitoring blade tip clearance, then the sensor structure is simple, but the sensor cannot accommodate thermal expansion leading to measurement errors
Solution Approach 1:
The soft lead acts as a flexible element that can deform to accommodate thermal expansion of the turbine blade and surrounding components. This flexibility allows the sensor to maintain accurate relative position measurements even as the engine components expand and contract during operation.
Solution Approach 2:
The sensor system transitions from a static, rigid structure to a dynamic, flexible structure that can adapt to changing thermal conditions. The soft lead enables the sensor to move and deform in response to thermal expansion, maintaining measurement accuracy throughout the engine's operational temperature range.
3Measurement precision
If a circuit board sensor with metallic plate and insulating material is used, then measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent combines the capacitor plates, insulating material, and circuit board into a single integrated circuit board sensor assembly. This merging of components simplifies the overall structure while maintaining the capacitance measurement functionality, reducing the number of separate parts that need to be assembled and managed.
Solution Approach 2:
The patent replaces traditional mechanical displacement sensors with a capacitance-based sensing system. The capacitance probe measures blade tip clearance through electrical field interactions rather than mechanical contact, eliminating the need for complex mechanical linkages and moving parts while improving measurement precision.
4Ease of operation
If the sensor is made small and lightweight, then ease of installation is improved, but measurement precision may be compromised
Solution Approach 1:
The patent uses a capacitance-based sensing system that requires minimal physical presence in the measurement location. The electric field extends through space, allowing accurate measurements without requiring a large physical sensor structure, thus enabling small and lightweight sensor design while maintaining precision.
Solution Approach 2:
The soft lead and flexible sensor design allow the sensor to be made compact while maintaining its measurement capability. The flexibility enables the sensor to conform to the limited space available in the turbine blade structure without compromising its ability to accurately measure blade tip clearance.
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 system provides precise measurement of blade tip clearances, maintaining desired tolerances and improving engine efficiency by accurately tracking changes in distance and accommodating thermal expansion without adding bulk, thus enhancing operational performance.
Implementation Method 1
a capacitance probe including a circuit board sensor having a metallic plate disposed within an insulating material
Implementation Method 2
As a gas turbine engine operates, certain parts may expand due to the heat generated and absorbed
Data Source
AI summary
A capacitance probe monitors the distance between a blade tip and a fan, compressor or turbine case. The capacitance probe may be attached to a liner, and may travel with the liner as it radially expands due to thermal changes. The capacitance probe may include a circuit board sensor with a metallic plate, and one or more capacitors. The metallic plate may be encapsulated within an insulating material. A plurality of soft leads may be in electrical communication with the circuit board sensor, allowing a lower lead weight, reduced size and increased flexibility. The soft leads may also be embedded in the liner. In this way, the capacitance probe can record more accurate distance measurements and promote a gas turbine engine's continued and efficient operation.