Optimization and experiment on pollination tube of collision and air-blowing hybrid rice pollination machine

Abstract: Pollination is the key process in the hybrid rice seed production. To realizing mechanical pollination of hybrid rice, this paper designed and trial-manufactured a hybrid rice pollination machine combined collision and air-blowing method. Flow field distribution of two types of the pollination tube on the machine, including air-blow nozzle type and air-blow hole type were simulated using CFD technology. And the flow velocity out of each nozzle or hole on pollination tube was measured, and the pollination experiments in the paddy field using pollination machine prototype were carried out. In the experiment, the pollen distribution produced by mechanical pollination and manual pollination was measured adopting gravity slide method, and the flow field model of the pollen distribution was established using Gambit software and Fluent software. The k-ε standard turbulence model was adopted during the simulation of solving the control equations. The inlet boundary condition was set as velocity inlet, and the outlet boundary condition was set as pressure outlet, and the others were set as tube wall. The results of numerical simulation showed that under the same condition of the inlet velocity, the airflow outside of the pollination tube with air-blow hole type is slant, and there are some dead zones where air could not reach outside of the pollination tube. The airflow direction outside the pollination tube with air-blow nozzle type is almost the same, which can provide uniform and stable airflow field for pollination. So the pollination tube with air-blow nozzle type is the ideal structure for hybrid rice pollination machine. In order to verify the simulation results, a trial-produced pollination machine and two types of pollination tubes with air nozzles were built for experiments. The velocities out of the blower on the machine were measured by an anemograph under different engine gears. These velocities were also the inlet velocities of pollination tube and they were 5.40 m/s, 10.00 m/s and 13.50 m/s respectively. Then the velocity out of each air nozzle on pollination tube was measured by the same anemograph under the above three inlet velocities. The results showed that the variation trends of air velocity both by measured and simulated are the same. The average errors between simulation value and measured value are 2.14%, 2.40% and 3.43% respectively, and the uniformity variation coefficient of air flow distributing along the pollination tube is 14.76%, 15.93%, 16.31% respectively in simulation. The pollination experiments in paddy field were conducted by the trial-manufactured pollination machine when the outlet velocity was 7.30 m/s. The pollen was collected by glass slide coated with Vaseline and the acquisition points were set on the four lines of female parent against the male parent. The same experiment method was used to collect pollen during manual pollinating. The results of field pollination experiments showed that the pollen amount on each line and pollen distribution uniformity among lines in mechanization pollination are better than that of manual pollination when the outlet velocity of air-blow nozzle is 7.30 m/s. The pollination efficiency of the mechanical pollination is higher than that of manual pollination, which provides practical machine model for mechanization pollination of hybrid rice.