The through-flow and broadband noise analysis methods are developed for axial flow compressor design system.
The flow-field in compressor blade is analyzed by the streamline curvature method as a through-flow analysis and the blade-to-blade empirical correlations. Spanwise loss and secondary flow models are proposed for the streamline curvature computing scheme to consider the three-dimensional flow effects blading. The blade profile loss is computed along streamlines which are obtained from the streamline curvature method, and the secondary flow loss is distributed in a parabolic function from hub to tip on a mass-averaged basis. Moreover end-wall boundary layer and tip clearance loss models are applied only to wall streamlines. The secondary flow generated in compressor blade cascade is approximated by the inviscid secondary flow theory in plane cascade. The through-flow field predictions by the through-flow analysis with the present loss and secondary flow models are good agreements with available experiments for axial flow compressors.
In the broadband noise analysis of axial flow compressor, a theory for predicting the noise due to the vortex shedding in blade wake is presented. The blade wake is assumed to be considered as classical Karman vortex street, and then the vortex strength and shedding frequency are determined from the wake structure. The fluctuating pressure and lift on blade surface are analyzed by incorporating the wake model with the thin airfoil theory. The predicted noise results by the present method show reliable agreements with the measured results for airfoils and several axial flow fans.
With the present through-flow and broadband noise analysis methods the effects of blade design conditions on the aero-acoustic performance of axial flow compressor are investigated by using parametric analysis. The parametric analysis results represent that in the case of lightly loaded fan, efficiency improvement and noise reduction can be achieved by decreasing the blade solidity, while the noise reduction by increasing the cascade spacing penalizes the attainable efficiency when fan or compressor is operated at highly loaded condition.
