The Use of Eddy Current Sensors for the Measurement of Rotor Blade Tip Timing: Development of a New Method Based on Integration

Abstract

The advent of tip-timing systems makes it possible to assess turbomachinery blade vibration using non-contact systems. The most widely used systems in industry are optical. However, these systems are still only used on developmental gas turbine engines, largely because of contamination problems from dust, dirt, oil, water etc. Further development of these systems for in-service use is problematic because of the difficulty of eliminating contamination of the optics. Eddy current sensors are found to be a good alternative and are already being used for gas turbine health monitoring in power plants. Experimental measurements have been carried out on three different rotors using an eddy current sensor developed in a series of laboratory and engine tests in-house to measure rotor blade arrival times. A new tip-timing algorithm for eddy current sensors based on integration has been developed and is compared with two existing tip-timing algorithms: peak-to-peak and peak-and-trough. Among the three, the integration method provided the most promising results in the presence of electrical noise interference. The main aim of this work is to develop an algorithm that can be used to build a simple, robust, real-time and low cost analogue electronic circuit for use in-service health monitoring of engines.

Experimental Investigation of High Temperature-Resistant Inductive Sensor for Blade Tip Clearance Measurement

“…Sridhar V. and Chana K.S. et al [16,17,18,19] used an eddy current probe on the gas turbine engine to obtain tip clearance values in the high pressure turbine stage. The results showed the sensor was able to perform at these extreme environments without losing accuracy.…”

A Review of NDT/Structural Health Monitoring Techniques for Hot Gas Components in Gas Turbines

“…Lui et al proposed a new method to improve the measuring accuracy of EC sensors by considering torsional vibration [66]. Ghana et al showed new tip timing algorithm for EC sensors which was verified in laboratory and real engines [67]. Tsutomu et al published their work on the usage of EC sensors for displacement measurements successfully [68].…”

Single-Coil Eddy Current Sensors and Their Application for Monitoring the Dangerous States of Gas-Turbine Engines

“…Despite the existing variety of methods for measuring the RC [5,8], their implementation is limited by very harsh and even extreme conditions in the gas-air path, which are associated with high temperatures in the measurement zone, reaching 1200 • C or more in GTE turbines, high linear speeds of the monitored blades tips, contamination of the gas-air path by fuel combustion products, vibrations, etc. The measurement methods on the base of eddy current sensors are one of the most promising methods for obtaining information about RC in such extreme conditions [10][11][12][13][14][15][16].…”