Session: 05-06 Topics in Instrumentation (II)

Paper Number: 82750

82750 - Analytical Methods for Transonic Compressor Rotor Blade Tip Clearance Measurements Using Capacitive Probes 

A method is presented to improve the sensitivity of proximity sensing capacitance probes used in rotor blade tip clearance (BTC) measurements. This research presents the development of a post-processing method to calibrate capacitance probes and to measure and analyze BTC of a transonic axial fan under high-speed and transient or resonant loading. The raw signal of capacitance probes normally exhibit a high signal-to-noise ratio (SNR) at larger tip clearances.. By synchronizing data via a once-per-revolution (OPR) signal, the variations in rotational speed can be eliminated. Each revolution’s raw capacitance probe signal was normalized to the OPR signal via linear interpolation. This also reduced timing inaccuracies in the sampling frequency that is inherent to the data acquisition system (DAQ) and puts the raw signal into a spatial domain to remove time dependence. A fast Fourier transform based lowpass filter is then applied to this normalized signal. The location of the maximum and minimum of the signal is found from the filtered signal, which eliminates uncertainty in the position of the peaks due to noise. These locations are then used to determine the peak-to-peak signal of the normalized raw signal from multiple blade passes. The application of this technique produces a more sensitive calibration curve especially at large distances from the rotor.

Presenting Author: Anthony Gannon Naval Postgraduate School

Presenting Author Biography: Position: Associate Professor<br/>Department of Mechanical and Aerospace Engineering<br/>Naval Postgraduate School<br/>Director of the Vavra Turbopropulsion Laboratory of the Naval Postgraduate School<br/>Education: <br/>Post-Doctorate 2005: Naval Post-graduate School, Monterey, California, USA.<br/>Doctorate (Mechanical Engineering) 2001: University of Stellenbosch, Cape Town, South Africa.<br/>Masters (Mechanical Engineering) 1996: University of Stellenbosch, Cape Town, South Africa.<br/>Bachelor of Science (Mechanical Engineering) 1994: University of Natal, Durban, South Africa<br/>Areas of Expertise:<br/>Energy: Renewable based cooling systems. System design, test and analysis. Thermal storage. Thermodynamic cycles. Solar Thermal Cycles. Solar heating. Power and propulsion cycles. Renewable powered HVAC.<br/>Turbomachinery: Design and testing. Low speed axial turbines. Industrial fans. Transonic compressors. MEMS vacuum. Accurate machine performance testing. Steam and foreign gas ingestion to compressors. Test Rig Design, compressor and turbine.<br/>MEMS: Micro-scale turbomachines. High Knudsen number flows. Micron scale flows.<br/>Data-Acquisition: Kulite pressure high speed data processing. Signal processing. Transonic compressor instability detection.<br/>Design optimization: Design optimization. Optimization algorithms.

Authors:

Anthony Gannon Naval Postgraduate School
David Magno Naval Postgraduate School
Walter Smith Naval Postgraduate School
Garth Hobson Naval Postgraduate School