气力集排式水稻分种器设计与试验

针对水稻直播高速作业和大播量的要求,设计了一种适用于气力集排式水稻直播机的分种器。从直播机的适应性、作业速度、播量调节等方面研究了气力集排式分种器的分种机理,分析了分种器的适应性、均匀性和稳定性;根据水稻种子的物理特性,采用Solidworks Flow软件进行计算流体动力学(computational fluid dynamics,CFD)仿真,对比不同结构分种器速度流场分布图,得到了较优等种数流场,获得了分种器设计参数;分种器划分为等种数流场结构、输送结构、下种结构,等种数流场结构又分为聚种、分种、派种3部分,通过理论分析与流体仿真计算,对比速度大小和离散度,模拟等种数速度场流线图,优化分种盖结构,选择合适的气源,设计了气种混合均匀的分种器,提高了直播机分种的均匀性和稳定性。试制了分种器并进行了台架试验,试验结果与CFD仿真分析基本一致,设计的10行分种器各行之间和行内播量变异系数分别为3.58%和4.55%,设计的20行分种器各行之间和行内播量变异系数分别为3.91%和5.04%,能满足不同直播机的要求。试验结果表明,直管输送管增加波纹结构有助于水稻种子向管道中央集聚;排种管的长短影响分种效果,特别是行内的稳定性,排种管的长度应尽可能一致;分种器内部结构影响气体速度场的分布,分种器内外盖形成的等距圆弧结构和输送管内波纹结构有利于分种器中气种等种数混合流场的形成,使播种均匀性更好。

Design and experiment of rice pneumatic centralized seed distributor

Abstract: Aiming at the requirements of high speed and large sowing quantity for rice direct seeding, a kind of rice pneumatic centralized seed distributor, including outer cover, inner cover, metering disc, gasket, mounting holes, distribution port, conveying pipe, was designed based on rice pneumatic centralized drilling machine. The distribution mechanism of pneumatic centralized seed distributor was studied according to the adaptability, working speed and seeding quantity adjustment of the drilling machine; the adaptability, uniformity and stability of pneumatic centralized seed distributor were analyzed; the computational fluid dynamics (CFD) simulation with Solidworks Flow software was carried out according to the physical characteristics of rice seeds; the distribution of velocity flow field of the seed distributors with different structure was compared, which contained 3 groups of comparative analysis: Factor 1 was for the internal structure of the conveying pipe, including the corrugated straight pipe and straight pipe without ripple, in which the spreader tube length and distribution port number were the same; Factor 2 was for the length of spreader tube, with 2 lengths of 1.5 and 2.8 m, in which the internal structure of conveying pipe and distribution port number were the same; Factor 3 was for the distribution port number, and one was 10 and the other was 20, in which the internal structure of conveying pipe and spreader tube length were the same. The optimal equal amount flow field (EF) was obtained, whose structure was the central symmetric body, with the velocity and pressure magnitude being equal for each point on the circumference with equal radius; the changes of air velocity flow field were consistent from the beginning to the end, the flow line and the track were coincident, and the seed distributor design parameters were obtained; the seed distributor contained the EF structure, the transportation structure and the spreading structure. And the EF structure was divided into 3 parts: EF1 (the horizontal part of flow field of the cover), EF2 (the circular part of flow field of the cover), and EF3 (the vertical part of flow field of the cover), which were for gathering seeds, dividing seeds and sending seeds, respectively. The structure of the outer cover was optimized through the theoretical analysis and fluid simulation, the velocity magnitude and the dispersion of equal amount flow field were compared, the flow line of EF velocity field was simulated, the proper air source was selected, a seed distributor with homogeneous mixture for air and seeds was designed, and the distribution uniformity and stability of drilling machine were improved. Platform experiment of seed distributor was carried out, and the experimental results were in accord with the CFD simulation analysis. The coefficients of variation of the seeding quantity between rows and intra-row for the 10-row seed distributor, which had the same spreader tubes and corrugated pipe for each row, were 3.58% and 4.55% respectively, and that for the 20-row seed distributor, which had the same spreader tubes and corrugated pipe for each row, were 3.91% and 5.04% respectively, which could meet the requirements of different drilling machines. The CFD and experiment results show that the adding of corrugated structure in the straight pipe can help the rice seeds gathering in the center of the pipe; the length of spreader tubes will influence the seed distribution effect, and therefore especially the intra-row stability, and the length of the seeding pipe should be as uniform as possible; the internal structure of the pipe affects the distribution of the velocity flow; the equidistant circular arc structure formed by the inner and outer covers and the corrugated structure in the conveying pipe are beneficial to the formation of the air and seeds mixed equal amount flow field, which makes the seeding uniformity better.