Optical Displacement Probe for Axial Radial Clearance Measurement
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Solution Overview
Problem
Existing methods for measuring clearance in gas turbine engines, such as capacitance probes, face challenges with access and temperature limitations, and are limited in accurately determining both axial and radial displacements.
Innovation Solution
An optical displacement probe arrangement featuring a target with circumferentially encoded surface features and an optical probe with a light emitter and receiver, allowing for the measurement of axial and radial displacements by analyzing variations in the reflectivity pattern as the target rotates, using a single or dual optical fibre configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance probes are used for clearance measurement, then measurement capability is provided, but the equipment size is relatively large and access is difficult
Solution Approach 1:
The patent replaces the mechanical/electrical capacitance probe system with an optical measurement system using light emitters, receivers, and encoded targets. This substitution enables clearance measurement while significantly reducing equipment size and improving access capability in confined spaces.
Solution Approach 2:
The patent uses optical encoding of target features on the rotating component to create a measurable representation of displacement. The encoded target patterns serve as optical copies that can be detected and translated into precise clearance measurements without requiring direct physical contact or large measurement equipment.
2Measurement precision
If capacitance probes are used for clearance measurement, then measurement capability is provided, but temperature limitations affect probe construction
Solution Approach 1:
The patent replaces temperature-sensitive electrical capacitance probes with an optical measurement system that is inherently more resistant to high temperatures. The optical components (light emitters, receivers, and encoded targets) can operate in higher temperature environments typical of gas turbine engines without the same thermal constraints as electrical equipment.
3Measurement precision
If optical devices are used for displacement measurement, then measurement capability is provided, but the ability to identify both axial and radial displacement is limited
Solution Approach 1:
The patent divides the measurement function into separate optical detection paths: one for axial displacement measurement and another for radial displacement measurement. By segmenting the measurement capabilities into distinct optical channels with appropriate encoding schemes, the system can independently measure and identify both axial and radial displacement components.
Solution Approach 2:
The patent extends the measurement capability from single-axis to multi-axis by introducing angular/rotational encoding dimensions. The encoded target patterns incorporate circumferential variations that enable the optical system to detect displacement in multiple dimensions (axial and radial) simultaneously, transforming a one-dimensional measurement into a multi-dimensional measurement capability.
4Measurement precision
If conventional optical detectors are used, then displacement measurement is provided, but access requirements are not met in limited space applications
Solution Approach 1:
The patent replaces conventional bulky optical detectors with a miniaturized optical measurement system that can be accessed through limited spaces. The compact arrangement of light emitters, receivers, and encoded targets enables installation in confined areas of gas turbine engines where traditional optical equipment would not fit.
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 measurement of axial and radial displacements with high temperature resistance and minimal space requirements, suitable for use in gas turbine engines and other applications with limited access, providing precise clearance measurements.
Implementation Method 1
the optical probe comprises a light emitter and a light receiver to reflect light from the target
Data Source
AI summary
In order to determine displacement, axial and radial in a rotating component, an optical displacement probe is used incident upon a target formed from surface features in a rotating component surface. The surface features create a target which is axially variable in terms of reflectivity, but substantially consistent for the same circumferential band incident position. In such circumstances, differences in responses can be determined by a controller deducting time period ΔT differences between peaks 20, 21, 30, 31 in one axial position from the time period in a different axial position in order to provide an axial signal proportional to axial displacement. In terms of determining radial displacement, an angularly presented probe part in the form of an optical fiber 3 is used so that variation of the time period is proportional to radial as well as axial displacement. In such circumstances by deducting the axial displacement determined through compounding a perpendicularly presented probe it is possible to determine radial displacement. The targets created may comprise stripes, wedge or parallel bands of surface features which have reflectivity from background activity as determined by the probes for signal processing by a controller as described.