Influence of Turbine Wheelspace Temperature on Measurements of Radial and Axial Displacements of Blade Tips

Abstract

This paper presents the results of a simplified analysis of a differential measuring circuit with pulsed supply of the single-coil eddy current sensors connected to the circuit, with approximate differentiation of currents, and with an ADC at the output. The circuit is designed as part of automation systems for tests of gas turbine engines. Methods for eliminating the temperature influences on the sensors using the hardware and software of the measurement system are considered. Using a model of the measuring circuit, we determined the families of conversion functions (dependences of the code on the desired radial and axial displacements) for normal and nominal temperatures and then, from their difference, the families of functions of temperature influence on code changes, which characterize possible errors. Quantitative estimates of the maximum values of the influence functions were obtained which confirm the efficiency of the proposed methods.