Abstract: Taking into account of the phenomena of choking in entrained flow and condensation shock in mixing chamber,a thermodynamic model of two-phase ejector was established by using mass,momentum and energy balances.In the simulation,the mixing area in the mixing chamber is constant.With R141b as refrigerant,the pressure change in the ejector at various mixing pressures was studied,and the effects of mixing pressure on the performance of compression/ejection cycle,the entrainment ratio and exit pressure of ejector were analyzed.The variations of optimum suction chamber pressure drop,the corresponding ejector entrainment ratio,the system optimum performance coefficient and the corresponding performance improvement ratio with condensation temperature and evaporation temperature were presented.The results show that under the operation conditions in this study,no condensation shock occurs in the mixing chamber of two-phase ejector.The constant area model for mixing chamber is more appropriate than constant pressure model.It is important to choose appropriate mixing pressure for optimizing the system performance,and the optimum mixing pressure,at which the ejector has the highest entrainment ratio,is slightly lower than the pressure of entrained flow but far larger than the critical pressure entrained flow.

Key words: compression/ejection, two-phase ejector, choking, condensation shock, mixing pressure

摘要： 考虑引射流体的壅塞现象和混合室内的凝结激波现象,对混合室采用恒面积混合模型,应用质量守恒、动量守恒和能量守恒对两相喷射器建立了热力学模型。以R141b为工质,研究了在不同混合压力条件下喷射器内的压力变化趋势,分析了混合压力对系统性能、喷射器喷射系数和出口压力的影响,探讨了喷射器最优引射室压降、系统最优性能系数及相应的性能提高率随冷凝温度和蒸发温度的变化情况。结果表明:在本文计算工况范围内,两相喷射器混合室内无凝结激波的发生;对混合室采用恒面积混合模型相比等压混合模型更合理;恰当选择混合压力对优化系统的性能非常重要,其最佳值略低于引射流体压力,而远高于引射流体的临界压力,且其对应于喷射器取得最高的喷射系数。

关键词: 压缩/喷射, 两相喷射器, 壅塞, 凝结激波, 混合压力