Clearance Measurement Device Specular Reflection Suppression
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Solution Overview
Problem
Conventional clearance measurement devices for rotating machines, such as axial compressors and turbines, face errors due to specular reflection from the marker surface, leading to inaccurate measurement of clearance between the casing and turbine blades.
Innovation Solution
The clearance measurement device employs a configuration with planar light sources and optical sensors where light reception fibers intersect at a predetermined angle, reducing light distribution variations and suppressing specular reflection, using fluorescent plates and scattering plates to ensure accurate light emission and reception, and includes a filter to block excitation light, thereby enhancing measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a point light source (optical fiber) is used to emit laser light to the marker surface, then the device structure is simple, but specular reflection occurs due to surface roughness causing measurement errors
Solution Approach 1:
The patent changes the light source parameter from a point source to a planar light source, and alters the light emission pattern from a single direction to multiple directions. This parameter change eliminates specular reflection errors by ensuring that at least some light rays always reflect to the detector regardless of surface roughness, thereby improving measurement accuracy
Solution Approach 2:
The patent transitions from a one-dimensional point light source to a two-dimensional planar light source. This dimensional change allows light to be emitted from multiple positions and angles simultaneously, creating a more robust measurement system that is insensitive to surface roughness variations on the marker
2Stability of the object's composition
If multiple light sources are arranged in a row along the rotating direction, then light distribution uniformity is improved, but the device structure becomes more complex
Solution Approach 1:
The patent combines multiple light-emitting elements into a single planar light source structure. Instead of using separate point light sources arranged in a row, the invention integrates them into one unified planar component, thereby achieving uniform light distribution while avoiding the complexity of multiple discrete elements and their associated mounting structures
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 configuration allows for precise measurement of clearance by minimizing errors caused by specular reflection, ensuring accurate detection of marker passage time and subsequent clearance calculation.
Implementation Method 1
a light transmission fiber configured to emit excitation light having a predetermined wavelength, and a fluorescent plate configured to emit fluorescence by the excitation light emit from the light transmission fiber
Implementation Method 2
a light transmission fiber configured to emit light, and a scattering plate configured to scatter the light emitted from the light transmission fiber
Implementation Method 3
receive light reflected from the rotating member, and detect the marker based on a change in amount of the received reflected light
Data Source
AI summary
A clearance measurement device is for measuring a clearance between an inner peripheral surface of a cylindrical casing and an outer peripheral surface of a rotating member configured to rotate in the casing. The clearance measurement device includes a marker provided to the outer peripheral surface; an optical sensor attached to the casing, and configured to emit light toward the outer peripheral surface, receive light reflected from the rotating member, and detect the marker based on a change in amount of the received reflected light; and a measurement controller configured to perform signal processing on signals from the sensor. The sensor includes light reception fibers disposed such that optical axes intersect and having a measurement region on the outer peripheral surface, and planar light sources provided in a row along a rotating direction and each configured to emit light in a manner overlapping with the measurement region.