蒸汽喷射器变工况性能的CFD探讨

CFD discuss of vapor ejector on variable condition

利用二维轴对称,真实气体模型对喷射式制冷空调系统的喷射器进行CFD计算。真实气体模型占用较多的计算机资源,但它的计算结果更加真实。计算的目的在于得到在变工况条件下喷射器性能的变化和制冷系统性能的变化情况。在计算范围中,存在一最优的发生压力Pg*(3.973568bar),使得此时的喷射系数和系统COP最大。当Pg>Pg*时,喷射系数和COP随着发生压力的增加而减少;当Pg<Pg*时,喷射系数和COP随着发生压力的下降而急剧下降。利用CFD的优势分析了造成这种结果的原因:发生压力的变化引起激波的变化,激波的变化导致工作流流体流量和引射流体流量的变化。

The 2D axisymmetric, real gas model was developed to calculate the ejector in the ejector cooling system. The calculation of the real gas model occupies more computer rcsourecs, but its result can bc more authcntic. The aim of the prediction is to obtain the ejector performance and COP in variable operating condition. There is an optimum generator pressure P5^＊ （3. 973568bar） with the giving geometry parameters. When P5 = P5^＊ , the entrainment ratio reached the maximum value; when P5 〈 P5^＊ , the cntrainmcnt ratio decreased sharply; when P5 〉 P5^＊ , the entrainment ratio decreased a little slowly. The change of the primary and secondary mass flow is caused by the change of shock wave; the change of shock wave was the result of the change of generator pressure.