ATP文丘里施肥器喉管结构优化与流场计算

为了验证试验得到的最佳喉管进出口直径之比λ的准确性,并进一步研究所对应模型的优越性与相关参数变化规律,采用软件Solidworks以及CFD对8种不同模型进行建模并计算,得出喉管压差与出口雷诺数、吸肥量、最小压力的变化规律,以及在相同工况下,8种不同λ值对文丘里施肥器的流场特性影响.结果表明:计算得到的最佳λ值与试验得到的λ值误差为8.6%,进口流量与试验对比误差为10.0%左右;压差与出口雷诺数呈幂函数变化规律,与最小压力呈线性变化规律;计算得到了该系列施肥器产生负压的必要条件,当λ=1.27时,产生负压条件的压差为4.3 kPa;提出当1.00≤λ<1.27时,初始压差随λ增大而减小,当1.27≤λ<1.68时,初始压差随λ增大而增大,增大趋势逐渐变大,当1.68≤λ<2.00时,初始压差随λ增大而减小;λ=1.27时比其他7种型号吸肥性能好,可靠性高,是ATP3,4,5,6系列施肥器λ的最优值.

Throat structure optimization and flow field analysis of ATP Venturi fertilizer applicators

In order to verify the correction of throat-to-outlet diameter ratio of nozzles, and clarify the superiority of the Venturi with this ratio and its related parameters variation rule further, software SolidWorks was used to generate 8 different Venturi 3D models, and a CFD software was launched to calculate fluid flows through them. The variation rules of pressure difference, Reynolds number, fertilizer suction flow rate, and minimum pressure were obtained, and the influences of λ on flow field characteristics under the same working condition were analyzed. The results show that the optimal λ simulated is different from that in literature by 8.6% and the error in the inlet flow rate between prediction and experiment is around 10%. The pressure difference varies with Reynolds number in terms of power function, but with minimum pressure linearly. The necessary conditions for a negative pressure in this series of fertilizer are obtained. The differential pressure for a negative pressure, p_ini, is 4.3 kPa when λ =1.27. p_ini decreases with increasing λ if 1.00≤λ<1.27. While p_ini increases with increasing λ but also shows a gradually increasing trend when 1.27≤λ<1.68. Pinitial decreases with increasing λ once more when 1.68≤λ<2.00. According to the calculated results, the flow field in the symmetrical plane of Venturis is analyzed and confirms that the suction performance of the Venturi with λ=1.27 is better than the other fertilizer applicators. Since λ=1.27 means a Venturi to be reliable, it should be the optimal value of λ for ATP 3, 4, 5, 6 series fertilizer applicators. 