Blade Tip Clearance Sensing With Dual Eddy-Current Waveforms
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Solution Overview
Problem
Existing technologies lack a robust sensing solution for accurately measuring clearance between rotating machine components in turbomachinery, such as aviation gas turbines, due to factors like thermal growth, centrifugal loading, and wear, which affect engine efficiency.
Innovation Solution
A system using magnetically coupled sensors that induce eddy currents in conductive targets, combined with signal processing units, measures clearance by analyzing voltage waveforms and timing differences, accounting for variations in target properties and operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensing technologies (magnetic fields, eddy currents, capacitance, optical) are used to measure clearance, then measurement capability is provided, but robustness and accuracy in harsh gas turbine environments is insufficient
Solution Approach 1:
The system uses multiple sensing parameters (waveform timing, amplitude, slope, frequency) derived from eddy current signals to measure clearance. By analyzing multiple parameters simultaneously and using timing information between multiple coils, the system achieves accurate clearance measurement while compensating for environmental variations and target property changes, thereby improving both precision and reliability
Solution Approach 2:
The system continuously monitors clearance measurements and uses this feedback to adjust operating parameters and maintain optimal clearance. The real-time measurement capability allows the system to compensate for thermal growth, centrifugal loading, and wear by dynamically adjusting parameters, improving measurement reliability in harsh environments
2Reliability
If multiple sensing coils and waveform analysis are used to improve measurement robustness, then sensitivity to target property variations is reduced, but device complexity increases
Solution Approach 1:
The sensing system is divided into multiple independent coils, each providing waveform information. By segmenting the measurement function across multiple coils and analyzing the timing and amplitude differences between their outputs, the system achieves robust measurements that are less sensitive to individual coil variations or target property changes, while keeping each coil relatively simple in design
Solution Approach 2:
The same sensor assembly performs multiple functions: measuring clearance, characterizing target properties, and monitoring vibration. The waveform analysis from the eddy current sensors provides multiple measurement capabilities simultaneously, reducing the need for separate dedicated sensors and thereby managing overall system complexity while improving measurement robustness
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 clearance measurements with sensitivity to variations in temperature and wear, enabling real-time calibration adjustments and improved engine efficiency.
Implementation Method 1
as the target passes through the magnetic field created by the sensor, eddy currents are induced in the target and generate a voltage waveform in the sensor coil(s)
Implementation Method 2
In non-ferrous targets, as the target passes through the magnetic field created by the sensor, eddy currents are induced in the target and generate a voltage waveform in the sensor coil(s)
Data Source
AI summary
Systems and methods for measuring a clearance between a rotating machine component and a sensor unit are disclosed. In some aspects, a system includes a sensor unit oriented to detect the rotating machine component as the rotating machine component rotates past the sensor unit, the sensor unit including at least a first sensing element and a second sensing element spaced apart from the first sensing element. The system includes a sensor processing unit in electrical communication with the sensor unit. The sensor processing unit is configured for receiving a first waveform from the first sensing element; receiving a second waveform from the second sensing element; and determining, based on a comparison between the first waveform and the second waveform, a distance between the blade tip and the sensor unit.