Abstract:
Comprehensive noise measurements were made in the inlet duct of a model of a typical two-stage transonic fan. The tests covered a range of variations in the inlet guide/rotor axial spacing from normal, in small increments, to a spacing of about one blade-chord length. The effect of compressor speed and flow is pronounced for both the discrete blade tone and the vortex noise. As the axial spacing is increased the discrete blade tone output is reduced, the vortex noise being virtually unaffected.
