Study On Relationships Between Cavitation State And Vibration Signal Characteristics Of Poppet Valve Based On EEMD

As an important element in hydraulic transmission and control,poppet valve is widely used in hydraulic systems because of its good sealing performance,strong overcurrent capability,fast response,strong anti-pollution ability and simple structure.However,the cavitation phenomenon in the poppet valve and the problems caused by cavitation such as vibration,pressure pulsation,noise and solid surface erosion seriously affect and restrict the application efficiency of the poppet valve.Therefore,it is of great engineering significance to monitor the cavitation state of poppet valve.Based on the cavitation test of tapered throttle valve model,this paper used the ensemble empirical mode decomposition(EEMD)method to analyze the vibration signal and extracted the vibration signal cavitation characteristic parameters.The variation of these parameters with the cavitation state of the poppet valve was analyzed.In order to obtain the cavitation characteristic parameters of the poppet valve vibration signal,the vibration signal and the cavitation image in different cavitation states were collected synchronously.At first,the wavelet packet denoising algorithm was used to denoise the vibration signal.Then,using the integrated empirical mode decomposition method combined with cavitation images,the cavitation component in the vibration signal is separated.Based on the analysis of waveform and Hilbert marginal spectrum,the root mean square value,marginal spectrum peak value,marginal spectrum center frequency and marginal spectral bandwidth of the vibration signal IMF2 components were extracted as cavitation feature parameters.The change of working pressure of poppet valve will cause the cavitation state to change.The variation law of vibration signal cavitation characteristic parameters under different inlet pressure and outlet pressure is analyzed,and the variation trend of the characteristic parameters of the vibration signal and the cavitation area under different inlet pressure and outlet pressure were compared and analyzed.The results show that as the inlet pressure increases or the outlet pressure decreases,the degree of cavitation in the poppet valve is continuously increasing.The root mean square value and marginal spectrum peak value of IMF2 mainly depend on the unit time of single cavitation events and they increase gradually with the increase of cavitation,while due to the influence of many factors,the variation law of marginal spectrum center frequency and marginal spectrum bandwidth is different at different stages of cavitation development.In general,with the increase of cavitation,they increase at first,then decrease and finally increased again.Valve opening is an important parameter affecting the cavitation state of the throttle valve.The influence of the valve opening on the cavitation characteristic parameters is analyzed.The results show that with the increase of valve opening,the degree of cavitation of the poppet valve is firstly enhanced and then weakened.The root mean square value,marginal spectrum peak value of IMF2 and the cavitation degree of the throttle valve have the same trend,and they tend to increase first and then decrease with the increase of the opening degree.The center frequency and the marginal spectrum bandwidth of the IMF2 marginal spectrum increase at first,then decrease and finally increased again.In this paper,the cavitation characteristic parameters of poppet valve vibration signal were studied,which lays a foundation for the real-time cavitation monitoring of poppet valve.