Research On Dynamic Characteristic Of A Forage Rubbing Machine’s Rotor

9R-40 forage rubbing machine is a new type of forage processing equipment between crusher and mincing machine.As the main working part of the forage rubbing machine,the rotor withstand centrifugal force,gas-solid two-phase flow pressure,and its own gravity.It is easy to generate vibration and cause excessive noise,which affected the life of the machine and health of the operator seriously.In order to ensure the safe,reliable and stable operation of the forage rubbing machine.Based on the simulation of the flow field in the rubbing machine,using unidirectional fluid-structure coupling method,which could obtain the distribution of rotor’s equivalent stress,strain and total deformation,and the static strength is analyzed and optimized.Theoretical analysis,finite element simulation and laser vibration testing were used to analyze and test the modal of the rotor,that verified the reliability of theoretical analysis and finite element model,and the rotor was optimized for dynamic characteristics.(1)The rotor’s plates thickness,number,and rotational speed had little effect on the pressure distribution of the flow field.The rotor pressure distribution and the air flow velocity in the forage rubbing machine were greatly affected by the rotational speed,the number of shelves was the next,and the thickness of the plates was the last.(2)Base on the rated speed of the 9R-40 forage rubbing machine’s rotor,the maximum equivalent stress was 352.92MPa,which occurs at the connection between the main shaft and the throwing impeller plate,and it is easy to be damaged,therefore,static strength optimization is needed.(3)The thickness of the plate had the greatest effect on the maximum equivalent stress and the maximum total deformation.The diameter of plates and fillet of the impeller plate and the main shaft took the second place.The thickness and number of plates had no significant effect on the maximum equivalent stress of the rotor.After response surface optimization,the maximum equivalent stress of the rotor was 176.68MPa,which was 51.03%lower than before optimization.The static strength met the requirement of use.(4)The maximum relative error of simulated and experimental modal frequency was 6.39%.Moreover,the vibration modes were basically same.It is clear that the established finite element model and numerical calculation results are credible.The pre-stress increased the modal frequency of the rotor,especially the frequencies of the1st,2nd,3rd and 7~thh orders increased large.(5)Resonance analysis showed that the first-order pre-stress modal frequency,147.43Hz of the rotor is close to the excitation fundamental frequency 140Hz,and the avoidance rate is 5.03%.Resonance is easy to occur.Therefore,the dynamic characteristics must be optimized.The 2nd,3rd order modal frequencies and the 2nd and 3rd order excited frequencies avoidance rates meet the requirement.(6)The plates thickness had the greatest influence on the low-order pre-stressed frequencies of the rotor,the spindle diameter took the second place and the final one was the plate diameter.After optimization,the first-order modal frequency avoidance rate of the rotor increased to 15.49%.The second and third order frequency avoidance rates have been reduced but all can meet the requirement of 15%,which avoided the resonance.The total mass was reduced by 1.06%,after dynamic characteristics optimization,the static strength and stiffness of the rotor meet the requirements for use.