亚洲一区欧美在线,日韩欧美视频免费观看,色戒的三场床戏分别是在几段,欧美日韩国产在线人成

In order to solve the problem that when the corn planter works at high speed and precision, the seed throwing point is high and the seed collides violently, which leads to the poor uniformity of grain spacing, a seed guiding device assisted by positive pressure air flow was designed based on Venturi principle. the main structure and key parameters of the seed guiding device were determined. The mechanism of air-assisted delivering seeds to realize “zero-speed seeding” was analyzed. The DEM-CFD coupling simulation method was used to simulate the working process of the seed guiding device. By comparing and analyzing the airflow field and the seed exit velocity, it was determined that the constriction angle of the intake chamber was 70°, and the length of the constriction section of the intake chamber was 8.2mm. The speed matching test, bouncing test, operation performance test and comparison test were carried out on the performance test platform of the seed metering device. The results showed that when the operating speed was 8~16km/h and the grain spacing was 20~25cm, the qualified rate was not less than 85.7%;and the coefficient of variation of particle spacing was not more than 15.8%. Compared with the gravity type seed guide tube, the higher the operating speed was, the more outstanding the excellent operating performance of the positive pressure airflow assisted seed guide device was. When the operating speed was 16km/h, the qualified rate of particle spacing was increased by 13.6 percentage points and the coefficient of variation of particle spacing was decreased by 7.4 percentage points, which met the requirements of precision seeding under high-speed conditions and was conducive to improving the overall performance of high-speed precision seeders.