Abstract
Turbine tip clearance of aero-engine is important to engine performance. Proper tip clearance can reduce the gas leakage over turbine blade tips and improve the engine efficiency of turbo machinery and reduce the fuel consumption. 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 may cause the material electromagnetic performance change for the conductivity and permeability varies with temperature. In order to verify the temperature effect on the sensor performance, the repeated calibration experiments were carried out to obtain the sensor repeatability error of 5.4%. Then, the sensor was calibrated in the range of 0 mm–4 mm clearance at temperature from 600 °C to 1000 °C and obtained the measurement error of 4.6%. Results indicate when the temperature ranged from 600 °C to 1000 °C, clearance measurement error is smaller than the sensor repeatability error so the temperature effect on the sensor characteristics can be ignored. This conclusion makes the sensor promising for monitoring the blade tip clearances at various temperature environment.
Highlights
The blade tip clearance of gas turbine is significant for its performance and efficiency
Based on the principle of inductive clearance measurement sensor and comparative experimental repeated measurement. This indicates the difference of measurement results during the range of research, the following conclusions can be drawn in this paper: 600 ◦ C–1000 ◦ C may be caused by the sensor repeatability error, and the temperature effect on the
The designed sensor with planar coil made of platinum wire was proved to be a good inductive sensor for its phase angle is up to 80◦ under 4 MHz excitation frequency and the sensor performance meets the requirements of tip clearance measurement for the measuring range was over 5 mm and the resolution is better than 0.01 mm within 5 mm range according to the static calibration result
Summary
The blade tip clearance of gas turbine is significant for its performance and efficiency. Precise measurement of tip clearance is the premise of accurate design and optimization of the tip clearance [1,2,3]. The study of sensor with high precision and high resolution for tip clearance measurement is necessary and crucial. Mark R.W. et al [4,5,6] from NASA Glenn Research Center started effort on microwave method applying to tip clearance measurement since 2003. The microwave sensor probe is able to operate at extremely high temperature and is unaffected by the contaminant in the turbine. While the sensing range is limited by the working frequency and the probe can only operate at 900 ◦ C without cooling
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