Eddy Current Probe Shroud for Turbomachine Blade Monitoring

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Solution Overview

Problem

Existing blade monitoring systems in turbomachines, such as magnetic pickup type transducers, face challenges with low signal amplitude at low blade speeds, high signal amplitudes at high speeds, susceptibility to and induction of magnetic fields, and degradation due to thermal or mechanical stresses.

Innovation Solution

An eddy current proximity probe assembly with a non-metallic probe tip shroud, which fills the void between the probe tip and the turbomachine casing, reducing flow disturbances and using eddy current probes to monitor blade health by detecting changes in impedance and voltage outputs indicative of blade clearance and degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If magnetic pickup type transducers are used to monitor blade degradation, then blade health monitoring is enabled, but signal amplitude becomes inconsistent across different blade speeds and magnetic interference occurs

Engineering Contradiction:

Improveblade clearance detection accuracyVSAvoidsignal consistency across blade speeds

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces magnetic pickup transducers with eddy current proximity probes. This substitution eliminates magnetic field interference and the associated signal inconsistency across different blade speeds. The eddy current probes provide stable, consistent signals regardless of blade speed variations, directly resolving the reliability issue while maintaining measurement precision for blade clearance detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters of the probing system by using eddy current technology instead of magnetic pickup. This parameter change affects the physical principle of operation, resulting in consistent signal amplitude across the full range of blade speeds and eliminating the magnetic interference problems that plagued the previous system.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If magnetic pickup probes are used, then blade monitoring is achieved, but magnetic fields are induced and susceptibility to magnetic interference increases

Engineering Contradiction:

Improveblade presence detectionVSAvoidmagnetic field interference

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent substitutes eddy current probes for magnetic pickup probes, replacing a magnetic-based measurement system with an electromagnetic induction system that does not generate significant magnetic fields. This eliminates the harmful magnetic field interference while maintaining the ability to detect blade presence and clearance accurately.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If probe tips are exposed within the turbomachine casing, then blade clearance measurement is enabled, but flow disturbances are created

Engineering Contradiction:

Improveblade clearance measurementVSAvoidflow disturbances

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a non-metallic shroud as an intermediary component that surrounds the probe tip. This shroud acts as a mediator that allows the probe to measure blade clearance while preventing direct interaction between the probe tip and the fluid flow. The shroud eliminates flow disturbances while maintaining measurement capability through its non-metallic, flow-friendly design.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a non-metallic shroud that acts as a protective shell around the probe tip. This shell design allows the probe to function while minimizing disruption to the fluid flow path. The shroud's material and geometry are designed to be flow-friendly, eliminating turbulence and pressure losses associated with exposed metal probe tips.

Inventive Principle:

Principle #30Flexible shells and thin films

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

The solution provides consistent signal amplitude across a wide range of blade speeds, reduces magnetic interference, and enhances the reliability of blade monitoring by accurately detecting blade health and clearance without increasing flow disturbances within the turbomachine.

Implementation Method 1

an eddy current proximity probe having a probe tip and a probe tip shroud disposed about the probe tip

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Data Source

PatentEP2615410B1Turbomachine blade monitoring system

Publication Date: 2020.03.04 GENERAL ELECTRIC CO

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AI summary

Embodiments of the present disclosure are directed toward a system that includes a turbomachine blade monitoring system 50 having an eddy current proximity probe assembly 138. The eddy current proximity probe assembly includes an eddy current proximity probe 52 having a probe tip 56 and a probe tip shroud disposed about the probe tip, wherein the probe tip shroud comprises a non-metallic material. The eddy current proximity probe is configured to provide a signal indicative of a presence of a turbomachine blade 22, wherein the eddy current proximity probe assembly is configured to be disposed within a turbomachine casing. The turbomachine blade monitoring system also includes a monitor coupled to the eddy current proximity probe assembly, wherein the monitor is configured to monitor a parameter of the turbomachine blade based on the signal.