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

Abstract

Turbine tip clearance of aero-engine is important to engine performance. Proper control of rotor tip clearance contributes to engine efficiency improvement and fuel consumption reduction. Therefore, accurate tip clearance measurement is essential. The inductive measurement method is one of the non-contact distance measurement methods, which has the characteristics of high sensitivity, fast response speed and strong anti-interference ability. Based on the principle of inductive sensor measuring tip clearance, the ambient temperature change will cause the material electromagnetic performance change for the conductivity and permeability varies with temperature. The calibration experiment was conducted to obtain the sensor resolution and sensing range. The effect of temperature on sensor parameters was extracted from high temperature experiment data. Results show the resolution of planar coil made of platinum wire can be 10 μm and the maximum sensing range can reach 5 mm. At temperature from 500 ℃ to 1100 ℃, coil inductance almost does not change with temperature while coil resistance varies exponentially with temperature, that means the coil inductance variation can reflect the tip clearance change and resistance can indicate the measuring temperature.

Experimental Investigation of Inductive Sensor Characteristic for Blade Tip Clearance Measurement at High Temperature

“…This indicates the difference of measurement results during the range of 600 °C–1000 °C may be caused by the sensor repeatability error, and the temperature effect on the measurement results can be ignored at high temperature. This conclusion is consistent with the conclusion in [28] that the influence of temperature on sensor inductance can be ignored for the variable of distance measuring of inductive sensor is inductance.…”

“…The sensor probe in this paper was manufactured by the device as Figure 5 shows. According to the study results in [27,28], the planar coil was made of 0.3 mm platinum wire which melting point is over 2000 K. The platinum wire was in advance painted by insulating paint which is heat-resistant of 1050 °C to prevent the shortage between windings. First, drilled 1.2 mm diameter holes in the center of two separate 3 cm × 4 cm acrylic plates and then fixed them in parallel and kept the distance slightly over 0.3 mm.…”

“…The purpose of calibration at high temperature is validating the sensor so it can operate well at different environment temperatures over 500 °C. The heat resistance of the sensor was verified in [28]. The high temperature calibration was conducted with the device as Figure 12 shows.…”

“…The designed sensor was tested at extremely high temperature to prove it can withstand the actual operating temperature. In the recent study [28], the relation between temperature and sensor parameters has been explored. When the temperature varied from 50 °C to 1100 °C, the sensor resistance changed with temperature significantly while inductance was almost unchanged.…”

“…Hence, this paper focused on validating the high-resolution inductive sensor performance and aimed at finding the temperature influence on the sensor characteristics and measurement results in the range of 600 °C to 1000 °C. Furthermore, instead of the signal processing circuits in [28], the simpler voltage division circuit was used to measure the clearance variation signal. The sensor repeatability error was verified by repeated calibration and then the measurement error at different temperatures was obtained by calibration at different temperature.…”