Numerical investigation of noise reduction of a pump-jet propulsor using porous metal

Abstract

A novel strategy for noise reduction in pump-jet propulsor (PJP) is proposed through the design of porous metal trailing edges on stator blades. The interference between stator wake vortices and rotor blades is one of the primary mechanisms for noise generation in PJP. The goal is to use a porous medium to diminish the intensity of turbulent vortices behind the stator blades, control the interaction between these shedding vortices and the rotor blades downstream of the stator, and ultimately suppress the rotor noise generation source. Large eddy simulation and acoustic analogy analysis of the entire propulsion system based on the Ffowcs-Williams and Hawkings equation are performed. It is found that with the use of porous stator trailing edges, the wake flow pattern of the stator is notably altered, the strong impact of the turbulent vortices on the rotor blades is weakened, and the wall pressure fluctuations on the rotor blades and duct are significantly reduced. As a result, the far-field radiation noise and tonal noise are both effectively reduced, with the maximum reduction in total and tonal sound pressure levels reaching 3.8 dB and 12.53 dB, respectively, corresponding to percentage reductions of 6.0% and 21.69%. These findings demonstrate that porous media have great potential for practical engineering applications in PJP noise control.