An experimental investigation of the aeroacoustics of a two-dimensional bifurcated supersonic inlet

An experiment was conducted on a two-dimensional bifurcated, supersonic inl et to investigate the aeroacoustics at take-off and landing conditions. A 1 04.1 mm (4.1 in) diameter turbofan simulator was coupled to the inlet to ge nerate the noise typical of a turbofan engine. Aerodynamic and acoustic dat a were obtained in an anechoic chamber under ground-static conditions (i.e. , no forward flight effect). Results showed that varying the distance betwe en the trailing edge of the bifurcated ramp of the inlet and the fan face h ad negligible effect on the total noise level. Thus, one can have a large f reedom to design the bifurcated ramp mechanically and aerodynamically, with minimum impact on the aeroacoustics. However, the effect of inlet guide va nes' (IGV) axial spacing to the fan face has a first order effect on the ac roacoustics for the bifurcated 2-D inlet. As much as 5 dB reduction in the overall sound pressure level and as much as 15 dB reduction in the blade pa ssing frequency tone were observed when the IGV was moved from 0.8 chord of rotor blade upstream of the fan face to 2.0 chord of the blade upstream. T he wake profile similarity of the IGV was also found in the flow environmen t of the 2-D bifurcated inlet, i.e., the IGV wakes followed the usual Gauss ' function. (C) 2001 Academic Press.