喉管直径对文丘里施肥器性能影响的数值模拟

基于雷诺时均Navier-Stokes方程和标准k-ε湍流模型,利用Fluent软件对文丘里施肥器的内部流动进行了数值模拟,并对数值计算方法的正确性进行了验证.模拟分析了喉管进口直径为4,5,6 mm,以及出口直径与进口直径之比λ为1.0,1.1,1.2,1.3和1.4时15种结构方案的吸肥性能.结果表明：喉管直径对喉管及扩散段内流动特性、吸肥性能和效率均有一定影响,但出口直径与进口直径之比λ对文丘里施肥器性能的影响要明显甚于喉管进口直径.根据效率最高原则,喉管直径比应为1.2～1.3.建立了λ=1.2或1.3时文丘里施肥器吸肥效率与流量比之间的回归模型,并应用回归模型预测了吸肥效率最大值.喉管进口直径4 mm的文丘里施肥器当直径比为1.3时吸肥效率可达到15.5%,与直径比为1.0相比,前者的扩散段内部流动平顺、无漩涡出现,且相同横截面的平均湍动能值要小.该研究结果为文丘里施肥器的优化设计提供了一定的理论参考.

Numerical simulation for influence of throat diameter on Venturi injector performance

The flow inside a Venturi injector was investigated numerically by Fluent software based on Reynolds-averaged Navier-Stokes equations and Standard k-ε turbulent model,and the reliability of calculations was examined and validated. 15 different throat structures constituted by inlet diameters as 4,5,and 6 mm,respectively,and diameter ratio λ of outlet diamer to inlet diameter as 1.0,1.1,1.2,1.3 and 1.4,respectively,were conducted for predicting injection performance. The results showed that the throat diameter has some influence on the internal flow behaviour of throat and diffusion pipe,injection performance and efficiency.The diameter ratio λ of outlet diamer to inlet diameter for Venturi throat has more influence on the injection performance than the throat inlet diameter.According to the principle of high efficiency,the range of diameter ratio is from 1.2 to 1.3.The regression models between injection efficiency and ratio of injection rate to inlet flow rate were established when λ was either 1.2 or 1.3,and their maximum efficiency was predicted.The Venturi injector with the throat inlet diameter of 4mm and diameter ratio of 1.3 can achieve the highest effeciency of 15.5%,having no vortex inside the diffusion pipe and less average turbulent energy at the same cross sections compared with diameter ratio of 1.0.The research results provide a theoretical reference for optimal design of Venturi injector.