Abstract:

Aiming at the problem that the filling of seed metering device for both rice and wheat could not achieve accurate seed capsule，a seed blowing device based on accurate counting was designed. According to the horizontal throwing trajectory and Venturi principle， the rice and wheat detection and seed blowing device were designed，respectively. The key factors affecting the seed filling performance of rice and wheat were identified according to the theoretical study. Based on CFD gas-solid coupling method， effects of structural parameters including nozzle structure， working speed and air inlet pressure on motion characteristics of seeds in the process of detection and seed blowing were analyzed. The feasibility of detection and seed blowing device was verified by simulation experiment，and the bench test was carried out to determine the delay time between grains. The results showed that the velocity distribution of type 3 nozzle tube structure at the nozzle mouth was wide， and the velocity distribution at X direction was more uniform. It was determined that the section length， width， height of nozzle tube were 18， 7， 3 mm，respectively. The air inlet pressure and working speed had a significant impact on the seed movement characteristics， and the resultant force and combining speed increased with the increase of air inlet pressure and working speed. Therefore， during rice and wheat seed metering， the better air inlet pressure was 300 Pa and the working speed was 20 r?min^-1. Under this operating condition， the simulation time of seed interval was much smaller than the theoretical time. Finally， the feasibility of the detection and seed blowing device was verified. The results of the bench test showed that the qualified rate of rice and wheat were 90.7% and 93.2%， respectively， when the intergranular delay time was 12 ms， the inlet pressure was 300 Pa and the seed plate rotary speed was 20 r?min^-1. The results provided reference for structural optimization design of mechanical seeding device for the rice and wheat.

Key words: rice, wheat, dual use seed metering device, precise counting, detection and seed blowing device, simulation test

摘要：

针对稻麦兼用排种器充种环节无法实现精确囊种的问题，设计了一种基于精确计数的吹种装置。根据平抛运动轨迹和文丘里原理分别设计稻麦检测装置和吹种装置，通过理论分析确定影响稻麦充种性能的关键因素，基于CFD（computational fluid dynamics）气固耦合方法仿真分析喷嘴结构形式、工作转速、气流入口压力对种子运动状态特性的影响，仿真试验验证检测与吹种装置的可行性，并开展台架试验确定粒间延时时间。结果表明，Type 3方形喷嘴管在喷嘴口处的速度分布较广且X方向速度分布更均匀，确定喷嘴管截面长度为18 mm，宽度为7 mm，高度为3 mm。气流入口压力和工作转速对种子运动特性有显著影响，合力和合速度均随气流入口压力和工作转速的增加而增加，确定水稻和小麦排种时较优的气流入口压力为300 Pa、工作转速为20 r·min^-1，在此作业条件下，种子间隔的仿真时间远小于理论时间，验证了检测与吹种装置的可行性。台架试验结果表明，在粒间延时时间为12 ms、入口压力为300 Pa、工作转速为20 r·min^-1时，水稻和小麦排种的合格率分别为90.7%和93.2%，满足稻麦兼用播种要求。研究结果可为机械式稻麦精量排种器结构优化设计提供参考。

关键词: 水稻, 小麦, 兼用排种器, 精量计数, 检测与吹种装置, 仿真试验