Effect of clocking on compressor noise generation

Abstract

The effect of stator clocking on the acoustic noise generation characteristics in an axial high-pressure compressor is analysed. A realistic geometry with one-and-a-half stages is assessed using high fidelity and low-order numerical methods for different clocking positions at approach operating conditions. The compressor efficiency and the acoustic noise emission is found to vary insignificantly between the simulated clocking configurations. Nonetheless, the pressure distribution is altered significantly right upstream of the inlet guide vanes. Although the cut-on modes exhibit at least 10 dB higher amplitudes, the cut-off modes contribute decisively to the wave pattern in the near field. Optimal acoustic liner design can expand on the differently evolving interference pattern of acoustic waves at discrete frequencies. The low-order model is found to predict the directionality of the acoustic waves and the cut-on criteria for the individual modes in excellent agreement with the high fidelity simulations. However, the phase cannot be estimated due to the simplicity of the low-order formulation.