Low Loss Screening Mechanism Of Drum Screen Of Fritillaria Ussuriensis Maxim Harvester And Its Parameter Optimization Test

In the process of mechanized harvesting,the damage to the Fritillaria ussuriensis maxim(FUM)bulb is serious,especially caused by the core component drum screen.The damaged FUM as seed results in a decrease in regenerative capacity affects the development and growth of seedlings,and causes the loss of production.As a medicinal commodity,the appearance and quality are poor,the price is going down and the economy is lost.Therefore,studying the damage of bulbs and improving the harvester is of great significance to ensure the green,high-quality,efficient,and healthy development of the FUM industry.In this study,the low loss of the FUM bulb is taken as the target.The collision caused by movement and the damage caused by collision are taken as the main line.Based on the theoretical analysis,discrete element simulation,collision test,and other methods,the low loss screening mechanism and parameter test research of the drum screen are carried out,aiming to provide theoretical support and technical reference for the development of the low loss harvest machine of FUM.The main contents are as follows:(1)The basic material parameters,such as triaxial size and grain weight of FUM bulb,soil moisture,coefficient of static friction,coefficient of rolling friction,and coefficient of restitution,were measured.The triaxial dimensions of different FUM bulbs followed a normal distribution.The average grain weight was 5.60g,2.33g,0.95g,0.48g,and 0.13g,respectively.The critical moisture content that affected the speed of soil agglomeration was 26%.Soil aggregates with moisture content less than 26%increased slowly with increasing moisture content,while the soil agglomeration of more than 26%accelerated with the increase of moisture content.The increase in soil agglomeration resulted in a significant increase in the amount of soil on the screen.The coefficients of static friction were 0.29,0.58,0.39,and 0.47,and the coefficients of rolling friction were 0.079,0.066,0.07 and 0.097,respectively.The coefficients of restitution were 0.30,0.24,0.41 and 0.38,respectively.(2)Based on kinematics and mechanics principles,the velocity model of the dropback point was established in the drum screen with a lifting plate.By using discretization of the model,polynomial fitting of discrete points,and high-speed photography,the change law of the dropback point velocity of FUM screening material was corrected and analyzed.Based on the law of conservation of kinetic energy and momentum,the mathematical models of kinetic energy and collision energy loss of FUM screening material were established,and the influence of dropback point kinetic energy on collision loss energy was analyzed.The theoretical analysis results showed that the dropback point velocity and the drum rotation speed were a quadratic function relationship and increased with the increase of the radial inclination angle of the lifting plate.When the radial inclination angle of the lifting plate was 30°,the maximum dropback point velocity was 4.91 m/s.The lost energy and the dropback point kinetic energy had a positive proportional relationship,and its ratio was 1-e~2.(3)The simulation models of the FUM screening material and the drum screen were established,and the change law of motion and collision with the drum rotation speed,radial angle,and normal inclination angle were analyzed numerically.The regression model of FUM screening material between the collision energy loss and the drum rotation speed,radial angle,and axial angle was established.The influence of the drum rotation speed,radial and axial inclination angle on normal and tangential energy loss of FUM in screening material,and the distribution of the energy loss with FUM-screen mesh,FUM-FUM,and FUM-soil particle were analyzed.The collision energy loss of FUM first increased and then decreased with the increase of drum rotation speed.The parameters of the drum structure with the lowest energy loss were obtained as follows:the radial inclination angle was 0°,and the axial inclination angle was 20°.(4)A simulated collision test was conducted to analyze the influence factors of loss energy(impulse)and mass loss ratio of FUM in the process of drum screening,and regression models of both were established by polynomial fitting.The results of the collision showed the mass loss ratio between FUM and screen mesh,between FUM bulbs,and between FUM and soil was positively correlated with the energy loss(impulse).(5)The test bench of the FUM drum screen was developed.The mass loss ratio,crushing rate,and soil content were used as test indexes,and the percentage content of FUM,drum rotation speed,and screening time were used as test parameters to carry out the single factor test and quadratic regression orthogonal rotation test.The optimum value of each test index and its test parameters was obtained.Through the enumeration method,the best parameter combination of each index was obtained:the percentage of FUM was 10%,the rotation speed was 14.8r/min,and the screening time was 20s.Field test results showed that under the condition of 0.62km/h forward speed,the drum screening device had a good operation effect and could meet the requirements of FUM harvest.