喉部面积比对喷射器性能的影响分析

摘要

A 2D axisymmetric model used by real gas was developed to calculate CFD of ejector in air conditioning system and evaluate the influence of throat area ratio (AR) on ejector performance. There was an optimum ejector throat area ratio AR*(5.76) with the giving calculation operating condition and the other geometry parameters. When AR = AR * , the entrainment ratio reached the maximum value. When AR ＞ AR * , the refrigerant flow backward the entrainment inlet, and with the increase of the AR, the backward flow increased sharply. When AR ＜ AR* , the entrainment ratio increased with the increase of AR. The critical back pressures (CBP) on the different AR had obtained. When AR was larger, CBP was lower; AR was smaller, CBP was higher. When AR ＜ 3.41, ejector could not work even if the back pressure was super low. The change of the primary and secondary mass flow were caused by the change of shock wave. The change of shock wave was the result of the change of nozzle diameter.%利用真实气体的二维轴对称,模型对喷射式空调系统的喷射器进行CFD计算,为了研究喷射器的喉部面积比对喷射器性能的影响.在计算工况条件下,存在一最优的喉部面积比AR*(5.76),使得此时的喷射系数和系统COP最大.当AR AR*时,喷射器出现倒流现象,而且随着AR的增加,倒流加剧.计算还得到了不同喉部面积比下的临界背压值.喉部面积比越大,临界背压越低,喉部面积比越小,临界背压越高.但是喉部面积比如果小于一定的数值(3.41),如何降低背压都不可能使喷射器工作.利用CFD的优势分析了造成发生变化的原因:喉部面积比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.