Study On The Particle Motion Characteristics And Throwing Mechanism Of The Disc Knife Chaff Cutter On Gas-solid Coupling

The chaff cutter is one of the primary machines for processing agricultural fiber crops.It is loved by the majority of agricultural and animal husbandry users in the Inner Mongolia Autonomous Region for its simple operation,low cost,and stable work.However,the current chaff cutter has problems such as high power consumption and straightforward blockage,which seriously affect its use and promotion.This study takes corn stalk as the object of cutting and,because of the shortcomings of the current chaff cutter research,uses a combination of theoretical analysis,CFD-DEM gas-solid coupling simulation,and high-speed camera technology to study the working mechanism of the corn stalk particle throwing process,the flow field characteristics within the throwing device and the particle group movement characteristics.The main research findings are as follows:(1)To study the chaff cutter’s throwing mechanism in-depth,based on the kinetic theory,the straw throwing motion process was divided into seven stages with single straw particles as the research object.The kinetic model was established for the material from chopping to collision with the blade,the material moving along the throwing blade,moving along the throwing straight and curved pipe,and after the material was thrown out of the outlet.The throwing distance tests show that the throwing distance test values at different speeds have the same variation trend as the calculated values,with a maximum relative error of 6.6%,indicating that the established kinetic model is reasonable and has a particular reference value.Through MATLAB/Simulink simulation software to study its motion law,the straw particles only in the process of moving along the blade there is acceleration phenomenon,in other stages are deceleration movement,throwing blade in the process of throwing material plays a significant role.The results show that the throwing distance increases linearly with the increase of the spindle speed.And the larger the spindle speed,the more beneficial to the material throwing.The throwing distance increases with the increase of the blade inclination angle and then decreases,the backward inclined blade is more excellent than the inclined front blade,and the backward inclined blade is more beneficial to the material movement.Based on the kinetic model,a characterization equation for the energy consumption of the material in the throwing process was established.The energy consumption test results show that the test and theoretical values tend to be the same.The maximum relative error is 5.3%,indicating that the energy consumption characterization equation can predict the machine’s energy consumption.(2)A CFD model of the throwing device was developed to investigate the effect of the flow field characteristics in the throwing device on the throwing performance.The numerical results show that the fluid flow on the outer side of the throwing tube is relatively smooth and that eddy currents are easily generated in the rotating area.The gradual change of the throwing tube structure from large to small will lose part of the fluid kinetic energy and reduce the throwing performance.The greater the rotational speed,the greater the airflow velocity.The simulation and test results can conform to this rule,with the maximum relative error within 10%.The CFD model established will be used to study the flow field characteristics in the device with a certain degree of confidence.(3)To improve the accuracy of the CFD-DEM gas-solid coupling simulation results,the critical parameters of the straw particles were tested and calibrated.The densities of the stalk,inner stalk,and stalk node tissues were 0.6131 g/cm3,0.4216 g/cm3,and0.9344 g/cm3,respectively,using the liquid immersion method.A quadratic polynomial prediction model was obtained for the input and calculated values of the collision recovery coefficients based on the high-speed camera-based collision recovery coefficient test and the EDEM numerical simulation reproduction test.A combination of the Plackett-Burman test,the steepest climb test,and the star point design test was applied to calibrate the static and rolling friction coefficients between the particles and between the particles and the machine shell,using the stacking angle of the rind,node and pith particle mixtures as indicators.The CFD-DEM gas-solid coupling model,which reflects the realistic distribution of the straw particle field and airflow field,provides data support.(4)A CFD-DEM gas-solid coupling model was developed to move pith,rind,and node particles inside the guillotine throwing device.The trajectories of single particles and particle clusters,the flow characteristics of straw particle clusters and airfields,and the forces on particle clusters were analyzed.The results show that the single particles are thrown in good agreement with the theoretical analysis and that the throwing blade provides the main driving force for the particle motion.The trajectories of single particles and particle clusters are similar,and the feeding volume does not significantly affect the trajectory of the particles.The results of the particle motion test based on highspeed camera technology show that the particle motion trajectory in the filmed area has the same trend as the motion trajectory in the simulation.It indicates that the established coupled CFD-DEM model and simulation parameters are reasonable.The distribution of the coupling force in the throwing device is consistent with the air velocity distribution,with the straw pellets being subjected to the highest coupling force as they enter the throwing duct area and the coupling force decreasing the closer they are to the discharge port.As the spindle speed increases,the average coupling force and the total coupling force both tend to increase,which is conducive to improving the throwing performance.The normal and tangential average forces between the inner and inner straws showed irregular fluctuations,with the more significant the spindle speed,the greater the fluctuations.The average force between straw particles is much greater than the average coupling force between straw and air.The normal and tangential mean forces between the inner straw particles and the throwing blades fluctuate enormously,but the normal mean force fluctuates more strongly.The normal and tangential mean force fluctuations between the inner pellets and the machine housing have similar strengths.This paper combines theoretical analysis and coupled simulation to investigate the motion of corn stalk particles in the throwing device.A theoretical and systematic theoretical mathematical model is more in line with the actual situation established.The motion characteristics of the corn stalk particle population in the throwing device are obtained from the perspective of gas-solid two-phase flow.It reveals the throwing mechanism of the chaff cutter.This study provides a theoretical basis and technical guidance for optimizing the structure and working parameters of the chaff cutter.