Analysis And Optimization Of Vibration Radiation Noise For A Forage Rubbing Machine

Forage crusher is a kind of forage processing equipment developed by our country.At present,there is a big problem of vibration and noise when forage crusher works.The results show that the noise of forage crusher is about100-110 d B(A),which exceeds the national standard of 90 d B(A).It not only seriously affects the service life and working performance of the crusher,but also produces noise pollution,which endangers the physical and mental health of the operator.In order to control the noise of forage crusher effectively,it is important to predict and optimize the vibration radiation noise of forage crusher shell.In order to predict the vibration and radiation noise accurately and optimize the structure sound,the unsteady flow field of the forage crusher was simulated based on the CFD and DEM coupling method,the basic characteristics of the unsteady flow field on the shell wall were obtained Pulsating pressure load with material.Secondly,the finite element method is used to analyze the mode of the shell,and the harmonic response of the shell is analyzed by loading the fluctuating pressure of gas-solid coupling flow field.The vibration response of the shell under different frequency loads is obtained.Thirdly,taking the vibration response of the shell as the acoustic boundary condition,the vibration radiation noise of the shell caused by the unsteady flow is calculated by the acoustic solid coupling method which combines the finite element method with the indirect boundary element method,the experimental research on the noise of the shell is carried out by the acoustic pressure method,the result of the noise number is verified.Finally,Kriging model and multi-objective genetic algorithm are used to optimize the structure sound design of shell vibration radiation noise.The specific research is as follows:(1)The pulsating pressure amplitude of the gas-solid flow field of the shell at the feed inlet is the largest,the pulsating pressure amplitude on the circular shell is the second,and the pulsating pressure amplitude on the discharge pipe is the smallest;the energy of the pulsating pressure decreases with the increase of the excitation frequency generated by the rotor rotation.(2)The first six natural mode frequencies of the shell are less than thefundamental and double frequency of the excitation frequency of the rotor,so there is no resonance.(3)The maximum deformation displacement of the shell decreases with the increase of the excitation frequency.The deformation displacement at the excitation fundamental frequency of 130 Hz is the largest,and the maximum deformation occurs at the feed inlet;the deformation displacement at the second frequency of260 Hz is the second,and the maximum deformation occurs at the feed outlet.(4)The structure of sound pressure level spectrum at each measuring point of forage crusher is very similar.The noise frequency is composed of discrete spectrum and continuous spectrum.The main noise source is the rotary hammer rotor dipole sound source.Among them,the sound pressure level of measuring point1 close to the feeding section area is the largest,the sound pressure level of measuring points 2,3 and 4 close to the circular shell accessories is the second,and the sound pressure level of measuring point 5 close to the side of the discharge pipe is the smallest.(5)Under the load condition,the simulation value of the sound pressure level of each measuring point at the basic frequency and the frequency doubled is basically the same as the test value,and the maximum difference of the sound pressure level is 1.69 d B,which shows that the vibration and noise numerical model is accurate and reliable.(6)When the hammer rotor speed is 2500r/min,the shell thickness of the feeding section is 4mm,the shell thickness of the crushing section is 3.5mm,and the shell thickness of the discharging section is 4mm,the total sound pressure level of the maximum noise radiated from the shell of the forage crusher reduces from102.9d B(A)to 86.9d B(A),which is lower than the national standard requirements of 90 d B(A).