A ground test application of laser Doppler velocimetry to aircraft gas turbine engine inlet flow

Engine inlet velocity flow fields are important for determining inlet flow distortion, optimizing inlet design, and understanding high angle of attack operation. We show that laser Doppler velocimetry (LDV) offers high spatial and temporal resolution for the case of a ruggedized LDV system incorporating a high-bandwidth real-time signal processor. An inlet duct with optical access and seeding methodology were developed. One-component axial mean and rms velocity profiles were successfully determined under steady state and transient engine run conditions from idle to maximum afterburner. Time-velocity correlations during transient engine maneuvers and an estimate of LDV data rate vs. laser power were also obtained. The results show that LDV may be applied to full-scale engine inlets both with and without seeding. Data rates in most cases would be adequate for active feedback control of the engine. The results of this work will be used to guide the development of an in-flight instrument. (Author)