Research On Active Control Method For Low Frequency Noise Of Pump Jet Propeller

At present,pump-jet thruster,as a new low-noise propulsion mode,has gradually attracted the attention of various countries.After using the pump-jet propeller,the noise of underwater vehicle has been obviously reduced,but it still has obvious low-frequency line spectrum noise produced by the propeller.Therefore,it has certain practical significance to study the low-frequency noise control method for pump-jet thruster.Active noise control method is an effective means to reduce low frequency noise.In the active noise control system,the arrangement of secondary sound sources and error sensors will have a great influence on the noise reduction effect of the whole control system.Therefore,combined with the pump-jet propulsion structure,this paper focuses on the study of the placement of secondary sound sources and near-field error sensors.Considering that propeller noise can be approximated as point sound source or dipole sound source in far field,this paper simulates the noise of pump-jet propeller with point sound source and dipole sound source respectively.Firstly,the characteristics of low-frequency radiated sound field of pump-jet propeller duct structure are analyzed.Secondly,the characteristics of the coupled sound field between the secondary sound source and the duct structure are analyzed based on the two types of secondary sound sources,point sound source and vibration area source.Then,combined with the results of sound field numerical analysis,the objective function under complex sound field conditions is established,and the optimal allocation method of error sensors is studied by combining particle swarm optimization.Then,combined with the pump-jet propeller structure,the position of the error sensor is optimized under the conditions which the number of secondary sound sources is different,and the noise reduction amount when the error sensor is located at the optimal position is obtained.Considering that the optimal positions of error sensors are different at different frequencies,the fitness function considering multi-frequency points is constructed,and the position of error sensors considering multi-frequency points is optimized.Finally,the principle verification test of active control method for low-frequency noise of underwater structure is carried out on the lake.The test results show that the active control method can realize the low-frequency radiation line spectrum noise control for sound source in bounded acoustic cavity,and the noise reduction of active control system can be effectively improved by optimizing the position of secondary sound source and error sensor.