Analysis of laser Doppler anemometer data arising from high speed turbomachinery studies

The laser Doppler velocimetry technique and data analysis methods used to measure the air velocities just outside the impeller of a small high speed centrifugal compressor are described. The difficulties encountered in applying the laser technique to this area are increased by high tip speeds of around 400 m/s, flow passage widths of the order of 7mm, and blade passing frequencies of up to 24KHz. Processing of the data was achieved by photon correlation and a fourier transform data reduction procedure.