Passive Wireless Strain Gauge for Turbine Blades
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Solution Overview
Problem
Current strain gauge technologies are not suitable for measuring strain in harsh environments like turbine engines due to issues with adhesion, mass, durability, and the need for physical connections, which can be problematic in high-temperature and high-stress conditions, and they often require continuous power supply.
Innovation Solution
A passive wireless strain gauge that translates strain into electrical capacitance and then to a frequency shift in an RF carrier, allowing for strain measurement without physical connections, using a thin, low-mass microwave circuit deposited directly on the engine blade, and a novel transponder circuit for interrogation and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional wired strain gauges are used in turbine engines, then strain measurement can be achieved, but adhesion problems occur due to high gas velocities and extreme g-forces
Solution Approach 1:
The patent replaces the mechanical adhesion system (adhesives bonding gauges to surfaces) with an electromagnetic field-based wireless measurement system. The strain gauges are equipped with RF transponders that communicate strain data wirelessly through electromagnetic fields, eliminating the need for physical attachment and thereby solving the adhesion reliability problem in high-velocity gas flow and high-g-force environments.
Solution Approach 2:
The patent introduces an RF transponder as an intermediary between the strain gauge and the external measurement system. This transponder receives power and transmits strain data wirelessly through electromagnetic fields, serving as a mediator that eliminates the need for direct physical connection and adhesive bonding, thereby resolving the adhesion reliability issue.
2Measurement precision
If wired strain gauges with continuous power supply are used, then continuous strain monitoring is achieved, but power supply failures occur in harsh environments
Solution Approach 1:
The patent implements periodic interrogation of the strain gauge transponder by an external reader system. Instead of continuous power supply, the transponder is periodically activated and interrogated to transmit strain data. This periodic action maintains continuous monitoring capability while eliminating the need for continuous power supply, thereby improving reliability in harsh environments where power supply failures are common.
Solution Approach 2:
The strain gauge transponder is designed to harvest energy from the electromagnetic field of the interrogating reader and use it to power its own operation temporarily. This self-service capability allows the transponder to function without an external continuous power supply, eliminating power supply failures in harsh environments while maintaining continuous strain monitoring.
3Area of stationary object
If optical fiber strain sensors are used, then distributed strain measurement over large structures is achieved, but physical connections are required which are problematic in high-temperature conditions
Solution Approach 1:
The patent replaces the mechanical physical connection system (optical fiber cables and connectors) with a wireless electromagnetic field-based communication system. Multiple strain gauges equipped with RF transponders can be distributed over large structures and communicate strain data wirelessly, eliminating the need for physical connections that are problematic in high-temperature conditions while maintaining distributed measurement coverage.
4Reliability
If thin film strain sensors are used, then adhesion and mass issues are improved, but the gas flow path can still be adversely affected by the sensor presence
Solution Approach 1:
The patent replaces the physical thin film sensor that occupies space and potentially interferes with gas flow with a wireless RF transponder-based strain gauge. The strain measurement is achieved through electromagnetic field interaction rather than physical presence in the gas flow path, thereby maintaining improved adhesion characteristics while eliminating gas flow interference.
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
Enables accurate and reliable strain measurement in harsh environments without power supply failures, maintaining the mechanical integrity of turbine blades and reducing maintenance costs by eliminating the need for physical connections and power sources.
Implementation Method 1
translating strain into electrical capacitance
Implementation Method 2
frequency shift in an RF carrier
Data Source
AI summary
A system and method of using a passive wireless gauge to detect the physical properties on an object.