Coaxial Clearance Sensor Assembly for Stable Tip Gap Measurement
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Solution Overview
Problem
Existing clearance sensors in rotary machines suffer from decreased long-term measurement reliability due to variations in assembly accuracy and potential wear caused by thermal expansion and vibrations, affecting the tip clearance measurement between a casing and rotor blades.
Innovation Solution
A clearance sensor design featuring a columnar detection electrode with coaxial guard and ground electrodes, connected by insulation members and locked together through screw-bonding or pin insertion, with insulation layers filling gaps to stabilize the components and suppress positional deviation, and optionally incorporating cooling flow paths for temperature management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulation layers are attached by thermal spraying and assembly is performed with fit adjustment, then the clearance sensor can be manufactured, but assembly accuracy variation becomes great and long-term measurement reliability decreases
Solution Approach 1:
The sensor is divided into modular components (detection electrode, guard electrode, ground electrode, insulation members) that can be assembled through simple connection operations rather than complex fit adjustments, reducing assembly accuracy variation while maintaining manufacturing feasibility
Solution Approach 2:
Insulation members are introduced as intermediary components that connect electrodes without requiring direct metal-to-metal contact or complex fitting, simplifying the assembly process and reducing accuracy variation while enabling thermal spraying application
2Measurement precision
If a simple three-layer electrode structure is used, then the sensor structure is straightforward, but positional deviation occurs due to thermal expansion and vibrations affecting measurement accuracy
Solution Approach 1:
Insulation members serve as stable intermediary structures that mechanically connect electrodes and maintain their relative positions, preventing positional deviation caused by thermal expansion and vibrations while preserving the simple three-layer electrode configuration
Solution Approach 2:
The sensor employs composite construction with insulation members combining structural support and electrical insulation functions, creating a stable framework that resists thermal expansion and vibration while maintaining measurement precision
Data Source
AI summary
A clearance sensor includes: a columnar detection electrode having a detection end surface on one end side in the axial direction of the center axis; an electrode member including a guard electrode and a ground electrode having the center axis coaxial with that of the detection electrode; an insulating member linking between the detection electrode and the guard electrode, and linking between the guard electrode and the ground electrode; and an insulating layer filling the spaces between the detection electrode, the guard electrode, the ground electrode, and the insulating member, wherein the space between the electrode member and the insulating member is retained in the axial direction and/or the direction around the axis of the center axis.