Potato-Soil Aggregate Fragmentation And Separation Characteristics Investigation

This thesis aims to investigate the problem of incomplete separation of soil and potato during potato harvesting,which leads to a high potato skin breakage rate.The potato-soil aggregates are studied as the research object,and a swing separation sieve is used as the mechanical basis.The EDEM-Adams coupling simulation method is employed to explore the crushing and separation characteristics of potato-soil aggregates,and to obtain an optimal parameter combination for the separation sieve.Subsequently,a field experiment is conducted to validate the optimal parameters.(1)Theoretical analysis of potato-soil aggregates crushing and separation.In order to investigate the working principle of the separation screen and the potato-soil aggregate separation mechanism during potato harvesting,a kinematic analysis of the separation screen was performed.The force analysis of potato-soil aggregates in three scenarios,namely rebound jumping,forward sliding,and backward sliding,was conducted to identify the main factors affecting soil fragmentation and potato-soil separation,which include the mass of aggregates,crank radius,inclination angle of the screen surface,vibration angle of the screen surface,crank rotational speed,and friction coefficient.(2)Soil physical parameter testing and analysis of its crushing characteristics.Direct shear tests and unconfined compression tests are conducted to measure the physical parameters of soil,including its compressive and shear strength.Sand soil in the potato planting area of Inner Mongolia is selected as the research object,and a drop test is performed using a factorial experiment and single-factor experiment methods to evaluate the soil’s fragmentation characteristics.Results show that the significant factors affecting soil fragmentation are soil volume,soil hardness,and drop height.The degree of soil fragmentation increases with increasing soil volume and drop height,but decreases with increasing soil compactness.(3)Simulation analysis of potato kinematic characteristics during potato-soil separation process.A three-dimensional model of the potato harvester separation sieve,a multi-sphere model of the potato,and a soil adhesion model were established using the EDEM-Adams coupling method.Single-factor experiments were conducted to explore the kinematic characteristics of potatoes under different crankshaft speeds,machine forward speeds,and sieve inclinations during the potato-soil separation process.The results showed that the smaller the crankshaft speed and sieve inclination,and the larger the machine forward speed,the more times the potato jumped on the sieve,and the more thorough the potato-soil separation.However,this also resulted in a greater impact force on the potato and lower transport efficiency.(4)Analysis of potato-soil aggregate fragmentation and separation characteristics and verification of optimal parameters for the separation sieve.The dynamic characteristics of the potato-soil aggregate fragmentation process were analyzed using the EDEM-Adams coupling simulation single-factor experiment.The potato’s force and bonding key rupture were explored to obtain the optimal parameter combination for the separation sieve.On this basis,field experiments were conducted to verify the rationality of the optimal parameter results.The results showed that the proportion of bonding key rupture increased with increasing crankshaft speed and decreasing sieve inclination,and was highest when the machine forward speed was 1.9 km/h.The peak force on the potato increased with increasing crankshaft speed and decreasing machine forward speed,while the sieve inclination had little effect on the peak force.The optimal parameter combination for the separation sieve was a crankshaft speed of 180 r/min,a machine forward speed of 1.9 km/h,and a sieve inclination of 14.4°.Through field experiments,this parameter combination achieved a tuber recovery rate of 98.01% and a potato skinning rate of 0.68%,meeting the technical specifications for potato harvesters.