A Numerical Study on the Flow and Acoustic Mechanisms of Fan Rotor-Stator Interaction Noise Reduction With the Wavy Leading-edge Stator

The broadband noise scattered by the fan rotor-stator interaction is the most important noise source in high bypass turbofan, and has become the focus in current aeroacoustics due to the complexity of its physical mechanism and the unavoidability during the turbofan working process. The flow and acoustic mechanisms of fan rotor-stator interaction noise reduction with bionic wavy leading-edge stator configuration was numerically investigated in this paper. A hybrid DDES/LAA flow-sound field method were used to simulate the rotor-stator interaction noise(Delayed-Detached-Eddy Simulation(DDES), Lighthill Acoustic Analogy method(LAA)). It is found that the stator blades with the wavy leading-edge have a significant mitigation on the fan tone and broadband noise, and the larger the amplitude of the wave configuration, the more significant suppression effect on the noise. The numerical simulation results show that the wavy leading-edge stator could significantly adjust the fan duct sound modes energy distribution, and has a significant mitigation effect on the higher-order circumferential sound modes. It is also found that the wavy leading-edge blade configuration can effectively reduce the pressure fluctuations strength on blade surface, and significantly changes the pulsation pressure distribution on the suction surface of the stator. It is proposed that a vortex structure similar to an aircraft wingtip vortex will be generated at the wavy leading edge of the blade, and this similar wingtip vortex will significantly reduce the turbulent pressure pulsation at the leading edge of the blade. However, when the vortex on adjacent sides of the wavy leading edge meet in the trough, the two opposite rotating vortices will interact and result in the vortex broken, forming strong airflow pulsations at the trough position which generate the hump-shaped pulsating pressure distribution.