Experimental investigations on the wall pressure measurement on the blade of axial flow fans

摘要

The topic treated in these experimental investigations is the wall pressure fluctuations in axial flow fans. Steady and unsteady wall pressure measurements of an automotive cooling fan have been achieved. In fact, in order to predict the flow induced noise, a predictive tool which can model wall pressure fluctuations in complex geometries is required. Computational Fluid Dynamics (CFD) coupled with semi-empirical aeroacoustic models is used. The models using Reynolds Averaged Navier-Stokes (RANS) equations are chosen as they are able to predict flow characteristics well for configurations of practical interest. Then semi-empirical models that predict the surface pressure power spectra are used with the RANS boundary layer data. Since these models were developed for flows over a flat plate, a test rig allowing the acquisition of wall pressure on the blade of an axial flow fan is designed and manufactured. Flush mounted compact pressure sensors and a slip ring enable the measurement of wall pressure in rotation. Mean surface pressure data from numerical simulation are compared with experimental ones. The wall pressure spectra levels computed with semi-empirical models are underestimated in the low frequency range (100-2000. Hz) but match quite well in the high frequency range (2-10. kHz).