| Forage kneading machine is a new type of forage processing equipment between grinder and guillotine cutting machine independently developed by China.When the forage kneading machine is working,the crop straw and other forage materials enter the kneading chamber from the inlet of the kneading machine.Under the impact of the high-speed rotating hammer,it rubs and shears with the tooth plate on the inner wall of the lower casing.After being crushed into a silky section,it is thrown out of the machine through the deflector and the impeller.At present,there is a major noise problem when working on the forage crusher,which not only affects the performance and service life of the whole machine,but also affects the working environment and the physical and mental health of the operator.Therefore,in order to effectively control the noise,the analysis and optimization of the pneumatic noise of the forage crusher is very important.In this paper,the 9R-40 forage crusher is used as the research object.First,the two-way fluid-solid coupling method and the dense discrete phase DDPM model are combined to control the unsteady airflow field and the bulk material-airflow two-phase in the forage crusher.The coupled flow field is numerically calculated to obtain the distribution law and pulsating pressure data of the gas flow field and the two-phase coupled flow field.Secondly,after obtaining the pulsating pressure data on the hammer rotor surface of the crusher,the static pressure fluctuation is converted into a rotating hammer rotor dipole sound source using the sound analogy theory FW-H equation.In order to consider the reflection and scattering effects of the shell on the sound field,the sound source of the rotary hammer rotor dipole and the wall of the shell are used as acoustic boundary conditions.The indirect boundary element method is used to discretely solve the equation,so as to numerically calculate the aerodynamic noise of the forage crusher prediction.Third,the sound pressure method is used to measure and analyze the aerodynamic noise of the forage crusher under no-load and load conditions,and compare the aerodynamic noisemeasurement results with the simulation results under load to verify the accuracy of the noise prediction model.Finally,based on the verified numerical prediction model,the optimized Latin hypercube sampling and multi-island genetic algorithm were used to optimize the design of aerodynamic noise for the forage crusher.Research indicates:(1)The frequency change law and change trend of air and load aerodynamic noise are similar.The main components of aerodynamic noise are discrete noise and broadband noise,and the maximum noise is discrete noise.(2)The total sound pressure level of the no-load and load inlet is mainly affected by the rotor rotation fundamental frequency 130 Hz sound pressure level,and the outlet outlet total sound pressure level is mainly affected by the 2nd frequency 260 Hz sound pressure level.(3)Compared with the no-load load,the total sound pressure level at the feed inlet of the forage crusher increased by 0.31 d B(A),and the total sound pressure level at the outlet decreased by 0.68 d B(A).(4)The aerodynamic noise test under load is basically consistent with the simulated sound pressure level spectrum curve.The main aerodynamic noise source is the fan sound source of the rotor rotation.The difference between the test and simulation total noise at the discharge port is 0.08 d B(A),and the difference at the feed port is 0.89 d B(A).It can be seen that the aerodynamic noise prediction results are reliable and the prediction model is basically accurate.(5)After optimization,the sound pressure level of the aerodynamic noise of the feed inlet of the forage crusher is 89.74 d B(A),and the sound pressure level of the outlet is 88.75 d B(A),both of which are lower than 90 d B(A),which meets the national standard Claim. |
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