Simulation And Research On Air And Screen Cleaning Of Combine Harvest Based On CFD-DEM

Cleaning plays an indispensable role in the mechanized process of rice combine harvest.The improvement of cleaning device will lead to the improvement in harvesting quality.Because of the complexity of the cleaning process,it’s hard to describe working state through traditional methods,neither the theoretical calculation nor the stationing measurement can accurately reflect the interaction between airflow and cleaning materials,it’s difficult to demonstrate the changing of trajectory and state of materials under the effect of airflow.Research on air and screen cleaning of combine harvest through numerical coupling simulation method based on the CFD(Computational Fluid Dynamics)-DEM(Discrete Element Method)will be a new option.The method which deals with gas and solid phases respectively in different software and achieves the transinformation between the two phases through coupling interface can accurately describe the airflow field and particle motion in the airflow field.This paper introduces the related research of domestic and foreign scholars on the airflow field of air and screen cleaning.Illustrate application of the DEM in different fields and the probability theory of materials passing through the screen during the process of vibrating.Studied the movement and distribution of the airflow field of three different structures cleaning shoe by using CFD software-Fluent and made comparative analysis of fluid velocity magnitude and vectors in the same section of each structure,the results showed that the airflow field of the cleaning shoe equipped with double inlet and wind deflectors suited the distribution requirements;This paper introduced the basic contact model of DEM,grain and short stalks mechanical models were set up in the EDEM software.Untied simulation of working process of the three different structure cleaning shoe was done based on the CFD-DEM coupling theory,statistical results showed that the cleaning shoe equipped with double inlet and wind deflectors performed better than the other two kinds of structures,proved the accuracy of the airflow field analysis results.Single factor simulation experiments were done for the inlet velocity,amplitude,vibration frequency and up wind deflector angle.Using SPSS software to analyze experiment results,data analysis showed that inlet velocity,amplitude and vibration frequency had significant effect on the cleaning index,from high to low were inlet velocity,amplitude and vibration frequency.Regressionequation of three factors to the impurity and loss rate were established.Angle changing of the up wind deflector had no significant effect on the cleaning index.Rthogonal simulation experiment with factor of inlet velocity,amplitude and vibration frequency was carried out.9m/s inlet velocity,35 mm amplitude,6.5Hz vibration frequency,the best work parameters combination was given out by comprehensive evaluation method considering impurity rate and loss rate.In order to verify the accuracy of the simulation results,the field orthogonal experiment was carried out by changing different parameters of the harvester parts to adjust the test level,1400r/min rotate speed,35 mm amplitude,6.5Hz vibration frequency,the same best work parameters combination as the results of simulation was given out by comprehensive evaluation method considering impurity rate and loss rate.The data also showed that in the orthogonal experiment,rotate speed of fan,amplitude,vibration frequency still had significant effects on the cleaning index.The significant level was exactly the same as it in the simulation,which proved it was feasible to research the process of air and screen cleaning of combine harvester by using Fluent-EDEM united simulation based on CFD-DEM coupling theory,providing a new thought and method for the improvement of air and screen cleaning of combine harvester.