Comprehensive capacitance sensor calibration for high-speed fluid-machinery tip clearance characterization

Abstract

This paper aims to lay a foundation for high-fidelity tip clearance measurements with capacitance sensors that can be adapted to any highspeed fluid machine, such as high-pressure turbines and compressors. A novel calibration procedure that does not involve rotating components is investigated and compared against established methods. First, a calibration bench is developed to demonstrate the static and dynamic performance of the sensors and perform quasi-static and dynamic calibrations in a controlled environment. Second, an in-situ methodology is developed to calibrate the sensors once installed in a turbine rig without complex positioning systems. A comprehensive uncertainty quantification analysis based on Markov Chain Monte Carlo sampling techniques shows that combined standard uncertainties as low as uc = 2.40 μm and uc = 4.69 μm could be achieved with the proposed bench and in-situ methodologies, respectively.