Phase Resolved Hot-wire Measurements for High-speed Turbomachinery Flows

Abstract

Detailed measurements of total temperature and velocity in high-speed, rotating turbomachinery flows are difficult due to the high sensor frequency response required. Constant temperature hot-wires have the needed frequency response, but are sensitive to both Tt and effective wire ρU which vary significantly in high speed flows. The multiple overheat method can be used to decouple the phase locked averages of Tt and wire effective ρU from the phase locked average hot-wire voltages. The present study will demonstrate the efficacy of this technique as well as a detailed uncertainty analysis of the multiple overheat method. The overall uncertainty is primarily determined by: the quality of the hot-wire calibration, the frequency response of the constant temperature hot-wire system, and the ability of the turbomachinery facility to maintain a constant operating point while the hot-wire overheat values are changed. As a proof of concept, a single constant temperature hot-wire was operated at four different overheats at the exit of a transonic axial compressor rotor. The phase locked average Tt and wire effective ρU fields show flow features relative to the rotor including blade wakes and tip clearance flows. These phase locked average measurements were validated against each other.