四槽轮配肥器肥料颗粒碰撞掺混离散元分析与优化设计

为解决精准施肥过程中变比配肥施肥机械搅拌掺混效率低、掺混均匀度一致性差等问题，设计了一种带有二次碰撞掺混锥形体的四槽轮变比配肥器，可根据4种肥料的需肥量控制4个槽轮以不同转速排肥，二次碰撞掺混腔实现变比配肥的非机械搅拌均匀掺混。测定了4种肥料颗粒的物料特性及在不同含水率条件下的破碎力和粘附力。采用离散元法，选用Hertz-Mindlin无滑动接触模型，分析4种肥料排料运动和碰撞掺混规律。通过正交试验和方差分析，发现槽轮转速在20～80 r/min范围内时，转速对掺混偏离度标准差影响不显著，四槽轮变比配肥器可以实现变比配肥均匀掺混；优化设计二次碰撞掺混锥形体在圆柱形掺混腔内最优高度为12.1 mm,在此高度下二次碰撞掺混锥形体锥角为57.9°。利用力链分析肥料颗粒在槽轮排肥器工作时受力分布，解算4种肥料颗粒所受到的挤压力均小于其破碎力，变比配肥时不会造成肥料颗粒破碎。另外，利用高速摄影分析不同频率、振幅的振动对肥料颗粒碰撞掺混的影响，发现振动对碰撞掺混均匀度影响很小；进行变比配肥碰撞掺混试验，试验结果表明，各组配肥掺混均匀度基本一致，实现了多种肥料的变比配肥和非机械搅拌均匀掺混。

Discrete Element Analysis and Optimization Design of Collision Blending for Four Flute-wheels Fertilizer

To solve the problems of low blending efficiency and poor consistency of blending uniformity in the precision fertilization process,four flute-wheels variable rate fertilization distributor with the secondary collision blending device was designed. It could change the speed of four flute-wheels to variable rate fertilization according to the fertilizer demand. And the secondary collision blending device could uniform blend of different rates of fertilizer without mechanical. The hygroscopic saturated moisture content, adhesive force and breaking force were measured under different moisture contents. Hertz-Mindlin no slip particle contact model of discrete element was used to analyze the regularity of four kinds of fertilizer particles in collision blending process. By means of orthogonal test and analysis of variance, the results showed that there was no significant effect on the standard deviation of blending when the speed of flute wheel was in the range of 20~80r/min and the four flute-wheels fertilizer distributor could blend four kinds of fertilizer evenly. The optimal height of the cone in secondary collision blending device was 12.1mm.Under this condition the cone angle of the cone was 57.9°. When working it was found that the pressure on the fertilizer particles was less than the break force compared with the force distribution of the fertilizer particles calculated by the force chain, fertilizer particles would not be broken in collision blending process. Besides, The high-speed photography were used to analyze the influence of vibration with different frequencies and amplitudes on the collision blending performance of four flute-wheels fertilizer distributor. It was found that vibration had little influence on working process. The collision blending test was carried out, the test results showed that the blending uniformity was basically the same, and the designed fertilizer distributor could achieve variable rate fertilizer blending and non-mechanical blending of four kinds of fertilizers.