Research On Acoustic Characteristics Analysis And Characteristic Line Spectrum Extraction Method Of Propulsion Pump Noise

As the basic premise of vibration and noise reduction and low noise design of the propul-sion pump,it is of great significance to fully reveal the key influencing factors and formation mechanism of the radiated noise of the propulsion pump.In the noise radiated by the propul-sion pump,the line spectrum noise has a strong identification degree and a high contribution to the overall noise,which can characterize the working state and structure information,and is the focus of the research on the noise radiated by the propulsion pump.In the propulsion pump,the mechanism of line spectrum noise is more complex because of the interaction be-tween guide vane,impeller and other components.Moreover,in some environments,the low signal-to-noise ratio(SNR)makes it difficult to identify and extract the line spectrum noise,which brings difficulty to the analysis of the propulsion pump noise mechanism.This paper focuses on the acoustic characteristics and line spectrum extraction method of the propulsion pump.Taking a pre-guide vane propulsion pump and a double-stage propul-sion pump as the objects,the extraction method of the characteristic line spectrum noise of the propulsion pump,the main acoustic characteristics and the characteristic line spectrum noise model of the propulsion pump under the condition of low SNR are mainly studied.The specific contents are as follows:(1)Propulsion pump noise testing and analysis system design based on Lab VIEW.It covers the hardware design of sensors and data acquisition,as well as the design of software modules such as signal analysis and display.The system supports simultaneous real-time acquisition of multi-channel sensor signals,and simultaneously analysis,display and storage of signals from each channel.It has the advantages of simple operation,high economy and efficiency.Based on the signal analysis module of the system,the acoustic characteristics of the noise,such as the energy distribution characteristics of the frequency band,and the spectrum characteristics,can be analyzed.(2)Radiated noise measurement and acoustic characteristics analysis of single-stage and double-stage propulsion pumps based on the cavitation tunnel test platform.On the basis of considering the influence of background noise,the variation law of acoustic characteristics of the pump noise under different working conditions was studied,and the correlation between the characteristic parameters of working conditions and the main characteristics of noise was studied.The results show that the noise energy of the propulsion pump is mainly concentrated in the middle and low frequency band.The sound pressure level of each characteristic frequency band of noise increases with the flow velocity,and the influence of the change of flow velocity on the noise energy distribution and the total sound pressure level of the propulsion pump is mainly reflected in the middle and low frequencies.(3)The noise signal model of the propulsion pump is studied based on the noise test data of the propulsion pump.Combined with the mechanism of noise signal and the characteristics of noise signal,the component analysis of noise signal is carried out.Based on the cyclosta-tionary characteristics of the noise signal of the propulsion pump and the characteristics of each component,The amplitude modulated signal model is established for the non-cavitation noise signal under the condition of constant speed.The cyclostationarity analysis method is used to extract features from the simulation signals with multiple SNR.The results show that the cyclostationarity analysis method has better extraction accuracy and anti-noise performance.(4)Research on the extraction of noise characteristic line spectrum of propulsion pump based on cyclostationary analysis algorithm.Firstly,the second order cyclostationary analysis algorithm was used to extract the characteristic line spectrum of the two kinds of propulsion pump noises,and the low-frequency line spectrum components,such as shaft frequency,blade passing frequency and harmonic frequency,were extracted.In order to further analyze the noise modulation characteristics and verify the extraction effect of cyclostationary analysis method,the pulse dynamic characteristics of the propulsion pump were obtained by CFD numerical simulation,and it was found that the low-frequency line spectrum extracted by the cyclosta-tionary analysis method could correspond to the characteristic line spectrum of the unsteady pulse force.Based on the results of feature extraction,the modulation relationship in the noise of propulsion pump is studied.It is found that the noise of propulsion pump has strong mod-ulation characteristics,in which the shaft frequency and rotor blade passing frequency are the main modulation frequencies.With the increase of flow velocity,the modulation contribution of rotor blade passing frequency will increase obviously.In this paper,the acoustic characteristics of propulsive pump noise are studied,and the extraction method of the feature line spectrum of propulsive pump noise under the condition of low signal-to-noise ratio is proposed,which can be used to extract the low frequency acoustic features under the condition of complex environmental interference,thus providing support for the research and engineering application of propulsive pump low noise design and target recognition.