| The complexity of Turbornachinery internal flows has few rivals in fluid dynamics practice. The geometry of the blade passages is highly complex, with stationary vanes, rotating blades, curved passages and obstructions in the flow channels. With the high bypass turbofans of the modem airliner, the jet noise has been reduced to the point where the acoustic radiation from the fan and compressor has become a serious headache. Presently, a major source of aircraft engine noise comes from interaction of the rotor viscous wake with the exit guide vanes, or stators; aeroacoustic analysis of the engines has thus taken on significant importance. The current study involved a numerical modelling of a single stage of an axial flow compressor in order to focus on the rotor-stator interactions and the flow phenomena responsible for acoustic generation. A 3D numerical study was carried out using URANS, along with the Reynolds Stress turbulence model, to model the flow through a single stage of the Purdue research compressor. The analysis of the flow variables and a correlation study involving the turbulence parameters and the acoustic pressure pinpointed the stator leading edge as the primary location of noise generation. Once the source of the fan noise was located, various geometry and operating parameters were changed to study their impact on the blade surface unsteady pressure field. Finally, a novel idea of dynamically altering blade geometry was employed to favourably affect the sound generation. Dynamically altering the stator blade thickness by 10% at blade passing frequency was found to reduce the tonal noise without affecting the macro level performance of the stage. |
