射流混药装置变工况流场特性试验与数值分析

Experiment and Numerical Analysis of Flow Field in Jet Mixing Device under Variable Working Conditions

为了解射流混药器在变工况条件下的流场特性,采用CFD数值分析和试验方法对其射流流场进行了分析。研究结果显示数值模型可以较准确地预测混药比随出口静压的变化,混药比随出口静压的增大而线性降低。通过分析变工况条件下的装置内流场可知,沿路径a-d-e方向的静压最低点位于靠近点d前端的混药室流域,流体静压在喷嘴内部迅速降低,在混药管内则呈上升趋势。在喷嘴射流影响下,靠近射流核心区的路径c-d段出现了局部旋涡。根据无量纲性能曲线分析结果可知,混药装置的压力比与混药比之间呈线性递减的关系,数值分析结果显示压力比预测误差最大值为6%,当扩散管出口静压大于0.45 MPa时,装置内出现药液回流现象,并失去在线混合的功能。

To investigate flow field characteristics of jet mixing under variable working conditions, a jet flow field was analyzed with CFD simulation method and experimental analysis. The results indicated that the proposed numerical model could exactly predict the mixing ratio changed with outlet static pressure. It is showed that the mixing ratio decreased linearly with the increase of outlet static pressure. The static pressure distributions under different conditions demonstrated that the lowest pressure point along path a- d-e located in mixing chamber was ahead of point d, and the static pressure decreased rapidly in nozzle field and rose up slowly in mixing tube. A local vortex appeared closed to jet core zone along path c-d, which was affected by jet flow. The non-dimensional performance curves presented a decreasing linear relationship between the pressure ratio and mixing ratio. The prediction error between numerical and experimental results was less than 6% ; when the outlet static pressure was higher than 0. 45 MPa, the reflux status appeared in the jet mixing device which lost the function of water-pesticide mixing online.