RF Resonance Probe Sensing for Turbine Blade Clearance and Speed
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Solution Overview
Problem
Conventional position sensor technologies fail to reliably detect and measure the presence and speed of turbine blades over a wide range of axial and radial displacements, especially in hostile temperature environments, and are not suitable for mid- and long-range detection and speed sensing of electrically conductive rotor blades.
Innovation Solution
A target sensor with a resonance frequency that changes with separation, driven by a radio frequency signal regulated below its resonance frequency, and a detector that varies with impedance changes to improve sensitivity and range, allowing for detection of multiple targets and indication of mechanical failure or speed of rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional position sensor technologies (variable capacitance sensors, optical sensors, eddy current devices) are used, then the sensor can detect turbine blades, but the sensor fails to achieve sufficient range, sensitivity, and robustness in hostile temperature environments
Solution Approach 1:
The patent changes the operating parameter from driving the sensor probe at its resonance frequency to driving it at a frequency below resonance. This parameter change fundamentally alters the sensor's impedance characteristics, enabling it to achieve both high sensitivity for detecting small displacements and extended range for large axial and radial movements, while maintaining robustness in hostile environments
2Measurement precision
If the sensor probe is driven at its resonance frequency, then measurement accuracy of blade-tip clearance is improved, but sensitivity and range for detection and speed sensing are reduced
Solution Approach 1:
The patent inverts the conventional approach by driving the sensor probe at a frequency below resonance rather than at resonance. This inversion exploits the impedance characteristics in the sub-resonance region, where the sensor achieves enhanced sensitivity for detecting blade presence and speed, while maintaining adequate measurement capability for blade-tip clearance
3Measurement precision
If inductive sensor elements are optimized for accurate quantitative measurements of blade-tip clearance, then measurement accuracy is improved, but performance for detection and speed sensing over wide ranges is compromised
Solution Approach 1:
The patent makes the sensor system universal by optimizing it for multiple functions simultaneously: detection of blade presence, measurement of blade speed, and quantification of blade-tip clearance. By driving the probe below resonance and using impedance detection, the system achieves adequate performance across all these functions without requiring separate optimized systems for each application
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 sensor achieves improved sensitivity and range for detecting turbine blades, providing effective blade-tip clearance and speed sensing, while maintaining robustness and immunity to noise and temperature variations.
Implementation Method 1
a sensor probe having a resonance frequency that changes as the separation of the sensor probe and a target changes
Implementation Method 2
an inductive sensor element (a coil) in the casing of the engine connected to a specially designed electronic controller
Implementation Method 3
an oscillator arranged to apply a radio frequency (RF), signal to the sensor probe
Implementation Method 4
a detector arranged to detect an electrical characteristic of the oscillator that varies with the impedance of the sensor probe indicating an interaction of the sensor probe with the target
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3
AI summary
Target sensor comprising: sensor probe having a resonance frequency that changes as the separation of the sensor probe and a target changes. Oscillator arranged to apply a radio frequency (RF) signal to the sensor probe, the oscillator having: control circuitry configured to regulate the frequency of the RF signal applied to the sensor probe to below the resonance frequency of the sensor probe. Detector arranged to detect an electrical characteristic of the oscillator that varies with the impedance of the sensor probe indicating an interaction of the sensor probe with the target.