Gas Velocity Measurements Within a Compressor Rotor Passage Using the Laser Doppler Velocimeter

The laser Doppler velocimeter, a new instrument capable of making nondisturbing gas velocity measurements, was used to investigate the flowfield within the rotating blade row of a low speed axial compressor. The velocimeter operates by measuring the transit time of a seed particle across interference fringes produced at the intersection of a split and crossed laser beam. The velocity (magnitude and direction) measurements made with the laser at the rotor inlet and discharge generally agreed within 2 to 3 per cent with measurements made with a hot film anemometer, pitot-static probe and wedge and tuft angle probes. Detailed flowfield measurements within the rotor passage were then obtained and compared with the analytical results from a potential flow model. This technique shows promise in making detailed flow measurements within high speed fans, compressors, turbines and nozzles, including the mapping of shock structures.