Laser-Doppler Velocimeter Measurement of Annulus Wall Boundary Layer Development in a Compressor Rotor

Detailed measurement of the flow field in the tip region of a compressor rotor was carried out using a laser-Doppler velocimeter (LDV). The axial and tangential components of relative velocities were measured upstream, inside the passage, and at the exit of the rotor, up to about 20 percent of the blade span from the blade tip. In addition, the relative stagnation pressures were measured from a Kiel probe; static pressures were derived from this and from the LDV measurement. The data are interpreted to understand annulus-wall boundary layer development inside the rotor, leakage flow, and losses in the tip region. The annulus wall boundary layer is well behaved at the leading edge and far downstream of the rotor. But inside the passage, complex interactions between the leakage flow and the annulus-wall boundary layer result in unconventional profiles with wide deviations from models employed for analyses.