气力式授粉喷气管道参数优化与试验验证

Parameter optimization and validation experiment on jet pipe of pneumatic pollination

杂交水稻制种气力式辅助授粉时,花粉随气流场运动,喷气管道多个喷孔的气流场叠加,表征气流场特性的射流极角、出孔动压对花粉分布均匀性、传播距离起决定性作用,为探索射流极角、出孔动压与管道参数之间的影响关系,获得较理想的气力授粉管道参数组合。该研究首先分析喷气管道气流场的叠加原理,采用消防烟雾弹发出有色气体经喷气管道的喷孔喷射并拍摄气流场图片,选取喷管直径、喷管壁厚、喷孔直径三因素为影响因子,以射流极角、出孔动压为评价指标,进行三因素五水平的单因素和多因素正交试验,通过对试验结果进行极差分析、矩阵分析,获得各因素对气流场特性的影响规律,找出较理想的因素组合并进行验证试验。结果表明,喷孔直径对射流极角和出孔动压的影响显著,3个因素的影响顺序为喷孔直径、喷管直径、喷管壁厚,较优的因素组合为喷管直径63 mm、喷管壁厚5 mm、喷孔直径12 mm,此时的射流极角为13.38°,出孔动压为31.6 Pa。验证试验表明,优化的因素组合明显提高花粉分布均匀性,花粉分布不均匀度(方差)降为1.33,花粉能形成覆盖母本行呈正态分布特性的单峰分布,能够满足气力辅助授粉对授粉管道的作业要求,研究结果为气力式授粉喷气管道的设计提供参考。

Auxiliary pollination is the most critical process during hybrid rice seed production. The uniform and sufficient pollination has significant meaning for improving seed setting rate and operating efficiency. In the process of pneumatic auxiliary pollination for hybrid rice seed production, the pollens move with airflow, the airflow fields of multiple parallel nozzles of jet pipe overlay, and the jet cone angle and nozzle air pressure are the most important characters in airflow field. Increasing jet cone angle can expand the coverage of airflow field and reduce blind area of pollination effect, and eventually improve the uniformity of auxiliary pollination. Increasing nozzle air pressure can improve the airflow speed and increase airflow penetration, which significantly influences the uniformity and sufficiency of pollen distribution and determines the propagation distance of pollens. In order to study the relationships among jet cone angle, nozzle air pressure and pipe parameters, and find the ideal combination of pipe parameters for pneumatic auxiliary pollination, the paper firstly analyzed the superposition principle of the airflow field formed by parallel multiple nozzles, and obtained the formulae of jet cone angle and nozzle air pressure. Chromatic smoke was generated by the smoke grenade and sprayed through the nozzle, and pictures of airflow field were taken by camera. Jet pipe diameter, pipe thickness, nozzle diameter of pipe were selected as 3 factors, jet cone angle and nozzle air pressure were selected as 2 evaluation indices, and the three-factor and five-level of single factor and multi-factor orthogonal tests were done. In experiment, initial airflow velocity of nozzle and vertical distance between airflow junction point and center line of jet pipe were measured, and 5 photos and 5 measurements were taken for each test; the range analysis and matrix analysis were carried out, the influence laws of various factors on airflow field characteristics and their weights were obtained, as well as the relationships between airflow field characteristics and jet pipe parameters. Results showed that the influences of nozzle diameter on jet cone angle and nozzle air pressure were very obvious. As the nozzle diameter of pipe increased, the nozzle air pressure and jet cone angle increased accordingly. The influence order of the 3 factors from high to low was nozzle diameter, pipe diameter and pipe thickness. The optimal combination of the factors to jet pipe was the pipe diameter of 63 mm, the pipe thickness of 5 mm, and the nozzle diameter of 12 mm. At this time, the jet cone angle was 13.38°, and the nozzle air pressure was 31.6 Pa. The optimal factors were verified by test. Pollination effects were evaluated by the selected 3 evaluation indices on effective distribution area ratio, average distribution density, nonuniformity of pollen distribution. The confirmatory test showed that the pollen distribution was more uniform, the effective distribution area ratio of pollen was obviously improved, the nonuniformity of pollen distribution（variance） dropped to 1.33, the degree of uneven distribution was significantly reduced, and the distribution images of pollen showed unimodal normal distribution. The pipe parameters can satisfy the requirements of auxiliary pollination, which provides important reference to the design of jet pipe for pneumatic auxiliary pollination in hybrid rice seed production.