EDEM-Based Screw Delivery Mechanism For Crushed Maize Straw

For further exploration of the screw delivery mechanism theory of crushed maize straw,discrete element modelling and calibration of crushed maize straw was carried out,physical tests and simulations of its screw delivery mechanism process were performed,and screw delivery tests were made at different pitch,feed rate and screw shaft speed test factors with productivity and power as indicators.Key research elements and conclusions are as follows:(1)Crushed maize straw is roughly divided into three main categories according to different materials: stalks of core,leaf and skin;the range of their intrinsic and contact parameters are measured through physical tests,i.e.the range of parameters for density,modulus of elasticity,shear modulus,Poisson’s ratio,coefficient of static friction,coefficient of rolling friction and coefficient of collision recovery of the stalks of core,leaf and skin of the crushed maize straw was obtained;then the repose angle of the crushed maize straw was measured using the siding lifting method and a repose angle of30.4° was concluded for the crushed maize straw.(2)Individual discrete element method of the stalks of core,leaf and skin of crushed maize straw;the Plackett-Burman test was performed to obtain the significant effects of stalks of core-leaf rolling friction coefficient,skin-leaf rolling friction coefficient and leaf-leaf static friction coefficient on the simulated repose angle;then the significance factors on the repose angle were obtained by Box-Behnken test: stalks of core-leaf rolling friction coefficient > skin-leaf rolling friction coefficient > leaf-leaf static friction coefficient;the repose angle test value of 30.4° was set as the target for finding the optimum,and the parameter combinations with the best significance factors were obtained as follows: leaf-stalks of core rolling friction coefficient of 0.303,skin-leaf rolling friction coefficient of 0.409 and leaf-leaf static friction coefficient of 0.371;and the reliability of the optimum parameter combinations was verified using t-tests.(3)The entire screw delivery mechanism process is investigated by a combination of physical tests and simulation optimization design.Single-and multi-factor discrete element simulations and physical tests were carried out on the pitch,feed rate and screw shaft speed during the screw delivery process of crushed maize straw.The results show that pitch,feed rate and screw shaft speed have significant effects on the productivity and power of screw delivery,and there is a significant interaction effect,with the factors influencing productivity in the order of feed rate > screw shaft speed > pitch,and influencing power in the order of feed rate > screw shaft speed > pitch;With the target parameters of productivity as the maximum value and power as the minimum value,the optimal parameters were found to be 300 mm in pitch,82.675 kg/min in feed rate and117 r/min in screw shaft speed,with a productivity of 81.035 kg/min and a power of496.701 W.The reliability was verified by t-test.