Blade Tip Clearance Sensing Using 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 complexities arising from thermal growth, centrifugal loading, wear, and vibration, which affect engine efficiency.
Innovation Solution
A system using magnetically coupled eddy current sensors with multiple coils to induce voltage waveforms, determining clearance based on deterministic timing and amplitude changes, and incorporating signal processing units for real-time calibration adjustments.
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 under complex operating conditions (thermal growth, centrifugal loading, wear, vibration) deteriorate
Solution Approach 1:
The patent transforms the clearance measurement problem from direct distance measurement to timing interval measurement. By measuring the time interval between voltage waveform peaks from two sensing elements rather than direct amplitude or position, the system achieves robustness against thermal growth, centrifugal loading, wear, and vibration while maintaining high measurement precision
Solution Approach 2:
The patent replaces traditional mechanical or direct electromagnetic sensing approaches with an eddy current-based electrical measurement system. The clearance is inferred from electrical voltage waveform timing characteristics rather than direct mechanical contact or simple field strength measurement, providing non-contact, robust measurement under harsh conditions
2Measurement precision
If sensitivity to variations in target properties and operating conditions is increased to improve measurement accuracy, then measurement precision improves, but system complexity increases
Solution Approach 1:
The patent extracts only the essential timing information from the voltage waveforms produced by the two sensing elements. By focusing solely on the time interval between waveform peaks rather than analyzing complete waveform characteristics or using complex signal processing, the system achieves high sensitivity to clearance variations while maintaining relatively simple system architecture
Solution Approach 2:
The patent divides the measurement function into two separate sensing elements positioned at different locations. Each element produces its own voltage waveform, and the clearance is determined from the timing relationship between these segmented measurements rather than from a single complex sensor, improving precision without proportionally increasing overall complexity
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 precise clearance measurement with sensitivity to variations in target properties and operating conditions, allowing for real-time adjustment to account for wear and rub events, enhancing engine efficiency.
Implementation Method 1
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).
Implementation Method 2
A system uses magnet and coils that are magnetically coupled to a region traversed by an electrically conductive machine part (target or blade).
Data Source
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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.