Der Einfluss der Zuströmbedingungen auf das breitbandige Geräusch eines Axialventilators

Beside the aerodynamic performance the sound power is an important parameter of fans. The
direct noise calculation based on the governing equations of fluid mechanics (“Computational
Aeroacoustics“) seems not to be applicable for industrial use within the next years although
recently considerable methodical progress was achieved.

This work is concerned with the prediction of broadband noise from an axial fan by means of
semi-empirical noise prediction models taken from literature and the comparison with
measurements. In these models different noise generating mechanisms are taken into account
and modeled separately. Emphasis is placed on the investigation of the mechanism “inflow
turbulence and interaction with the fan blades”, which can become a dominant factor in the
broadband noise spectrum of the fan if the incoming flow is disturbed. Characteristic
parameters of a range of turbulent flow fields generated by various inflow arrangements are
measured with hot wire anemometry and fed into the fan noise prediction models. The
predicted broadband spectra as well as the broadband overall sound power levels are in
reasonable or even satisfying agreement with the measurements.