Phase-Based Reactance Measurement for Turbo-Machine Clearance
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Solution Overview
Problem
Eddy current sensors face challenges in providing accurate absolute measurements of static separation, particularly in high-temperature environments like turbo-machine assemblies, where factors such as drift and signal interference complicate the detection of proximity, leading to inefficiencies and potential engine performance issues.
Innovation Solution
A reactance measuring apparatus that uses phase measurements instead of amplitude, employing a circuit with fixed reactance, alternating current, and analysis units to measure and output the phase-dependent reactance of a sensing component, which includes features like balanced differential signals, limiting amplifiers, and phase locked loops for noise rejection and precision, along with temperature correction using resistance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amplitude-based detection is used in eddy current sensors, then regular changes in separation can be detected, but accurate absolute measurements of static separation are compromised due to drift and signal interference
Solution Approach 1:
The patent changes the measurement parameter from amplitude to phase. By measuring the phase of the voltage signal across the sensing component rather than its amplitude, the system achieves accurate static separation measurements that are immune to drift and signal interference. The phase measurement provides a stable reference that does not suffer from the same degradation issues as amplitude-based detection.
2Reliability
If nominal clearance is set to prevent blade-casing contact during extreme events, then safety is ensured, but clearance is larger than necessary during normal operation, increasing fuel costs
Solution Approach 1:
The patent implements feedback through phase-based measurement that accurately monitors static separation in real-time. This reliable feedback enables active clearance control systems to adjust casing shape or size based on actual measured clearance, allowing the system to optimize clearance dynamically rather than relying on conservative fixed settings. The accurate phase measurement provides the necessary feedback signal for closed-loop control.
Solution Approach 2:
The patent enables dynamic clearance control by providing accurate real-time measurement of static separation. Instead of relying on fixed nominal clearances set for extreme conditions, the system can actively adjust clearance based on actual operating conditions, transitioning from a static safety margin approach to a dynamic optimization approach that reduces energy loss during normal operation while maintaining safety.
3Measurement precision
If capacitive or optical sensors are used for clearance measurement, then measurement capability is provided, but sensors degrade quickly and are vulnerable to contamination or loss of function in high temperature environments
Solution Approach 1:
The patent replaces capacitive or optical sensing mechanisms with eddy current sensing based on electromagnetic induction. This substitution uses a coil as the sensing component that generates eddy currents in the target object, providing a contactless measurement method that is inherently more robust in high temperature environments. The electromagnetic-based approach avoids the degradation issues associated with capacitive or optical components exposed to extreme thermal conditions.
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
This approach enables reliable detection of small reactance changes and accurate measurement of static separations, even in noisy conditions, improving sensor robustness and accuracy across a wide temperature range, thus enhancing turbo-machine efficiency and reducing fuel costs.
Implementation Method 1
an electrical source configured to drive an alternating current through the circuit; and an analysis unit configured to: measure the phase of a signal in the circuit that is dependent on the reactance of the sensing component
Implementation Method 2
When a metallic object is brought close to the coil, significant eddy currents are generated in the object and the amplitude of the response changes
Data Source
AI summary
Apparatus and methods for reactance measurements are disclosed. The apparatus and methods are particularly suitable for eddy current proximity sensors in turbo-machine assemblies. In one arrangement, there is provided an apparatus comprising a circuit for receiving a sensing component of a sensor. The circuit has a unit having fixed reactance. An electrical source is provided for driving an alternating current through the circuit. An analysis unit measures the phase of a signal in the circuit that is dependent on the reactance of the sensing component. A measure of the reactance of the sensing component is output based on the measured phase.