Relative flow and turbulence measurements within and downstream of an axial flow rotor

Abstract

This article presents the results of an experimental investigation on the relative flow within and behind an axial fan rotating row. The flow within the rotor passages has been surveyed over blade-to-blade surfaces with a laser-Doppler velocimeter (LDV), while the flow leaving the rotating blades has been measured by means of stationary hot-wire probes and fast-response miniature pressure transducers. A phase-locked sampling and ensemble-average technique has been applied to separate periodic and random contributions from the instantaneous signals of the different stationary measuring instruments. Within the rotor both axial and tangential velocity components and the related variance have been measured by rotation of the single-channel laser-Doppler optics operating in back-scatter mode. In the plane aft of the rotor all mean velocity and Reynolds stress components of the relative flow have been determined using a 12-orientations single-sensor hot-wire technique. The static and relative total pressure distributions have been obtained from the velocity components and the ensemble-averaged total pressure distributions given by the fast-response miniature pressure transducers. The results, shown in terms of secondary vector plots and contours of mean flow characteristics, turbulence intensity, and Reynolds stress components, give a detailed picture of the rotor flow kinematic structure and of the relative total pressure loss and turbulence distributions.