Measurement of unsteady flow and turbulence in a low speed axial compressor

A two-stage experimental axial compressor with incompressible flow conditions and relatively large geometric dimensions is utilized for a detailed investigation of the unsteady flow field and the structure of turbulence. Hot-film probes in split-film configuration operated in constant temperature (CT) mode in different forms and orientations are applied. Evaluation of the measurements in a mainflow/crossflow/radial flow reference system renders turbulence data and Reynolds-stress terms compatible with the physics of the wake flow. Turbulence between the rotor blade wakes is relatively low with 3% and nearly isotropic. Turbulence in the wakes increases about threefold to 10%, has a characteristic structure and is definitely anisotropic. It depends distinctly on the operating point of the compressor. A comparison of the different probe types shows good results between the rotor blade wakes. In the wake region the circumferential extension of one probe type enables a correct measurement of the unsteady flow components. (C) 1998 Elsevier Science Inc. All rights reserved.