多肥料变比变量施肥过程模拟与排落肥结构优化

变比变量施肥中,排肥管和落肥管结构对多种肥料的掺混性能和排肥滞后有重要影响。在已完成掺混腔结构优选的基础上,使用离散元法对变比变量施肥和撒播过程加以仿真,分析不同排肥管高度与落肥管三角波纹形状对颗粒运动的影响,依据提出的性能评价指标,优化排肥管和落肥管结构。计算结果及机理分析表明:排肥管高度越大,颗粒在下落、碰撞及混合各阶段的速度越大,颗粒与掺混腔壁面碰撞后形成的散布面积越大,颗粒混合均匀性越好,颗粒混合配比标准差越小;落肥管三角波纹高度在4~6 mm范围内,相对于无波纹情况,可增加颗粒与落肥管间和颗粒间的碰撞次数进而促进颗粒均匀掺混,但高度过大会延缓与其接触的颗粒下落。当落肥管三角波纹高度约为2 mm时,即为肥料颗粒直径的40%~60%,最有利于促进肥料颗粒之间的混合,同时三角波纹对颗粒下落的滞后影响较小。

Granular Multi-flows Fertilization Process Simulation and Tube Structure Optimization in Nutrient Proportion of Variable Rate Fertilization

The structures of fertilizer tube and fertilizer falling tube have an important impact on the granular multi fertilizer flows blending and fertilizing hysteresis performance in the nutrient proportion of variable rate technology (NPVRT). On the basis of the optimal structure of the blending cavity structure, the granular multi fertilizer variable rate fertilizing process was simulated by discrete element method in this paper, and the impact on particles motion under varied height of fertilizing tube and varied diameter of triangular shape of the bellows was analyzed. According to the proposed performance evaluation indexes, the structures of fertilizing tube and bellows were optimized. The computing and mechanism analysis results show that: first, the greater height of fertilizer tube was, the higher particles speed in falling, collision , mixing and the various stages were. Second, the greater the spread area after the particles colliding with the blending cavity was, the better the particles blending was, and the smaller the standard deviation of particle blending ratio was. Then, the height of triangular shape of the bellows for fertilizer dropping was in range of 4~6mm, relative to the non-bellows one, that could raise the number of collisions among the particles and bellows, thus improving the uniformity of particles blending. However, excessive height slowed down the dropping particles contacted with bellows. If the height of triangular shape of the bellows was about 2mm, that was approximately 40% to 60% the diameter of fertilizer particle, the uniformity blending of particles could be promoted, and triangular shape had smaller effect on time-lagging of particles.