Laser two-focus velocimetry (L2F) for turbomachinery flow measurements

The mean flow through the Purdue Research Centrifugal Compressor is studied using a laser two-focus velocimeter (L2F). The beam deviation associated with measurements through curved windows is analyzed and optical corrections determined. L2F data are then obtained which quantify: (1) the compressor inlet flow field; (2) the velocity field through the rotating impeller blade passages; and (3) the flow in the radial diffuser, including the vaneless space and the vaned diffuser. The laser two-focus system is then discussed in terms of measurement accuracy, ease of use including sample time per correlated event, and the ability to utilize small particles for measurements.