Abstract:

According to the thermodynamic process and the sound speed calculation models of the single/two-phase flow, a method with real gas is presented to design cylindrical mixing chamber ejectors. The entrainment ratios calculated by the proposed method match the experimental results relatively well with an error of ±17%. The proposed method predicts that there must be an optimal exit pressure of the mixing chamber corresponding to the maximum design entrainment ratio. The optimal reciprocal value of diffuser pressure ratio is introduced in order to determine the relationship between the optimal exit pressure of the mixing chamber and design conditions of ejectors conveniently and quickly. The relation curves of optimal reciprocal values of diffuser pressure ratios vs expansion and compression ratios for steam, ammonia, R290, R134a and R22 ejectors are calculated based on usual working conditions, and further the corresponding regression expressions are fitted. Those expressions can figure out the optimal reciprocal values of diffuser pressure ratios rapidly so as to obtain the optimal exit pressure of the mixing chamber, and thus a high efficient ejector can be designed.

Key words: real gas, ejector, mixing chamber exit pressure, thermodynamic process, gas-liquid two-phase flow, optimal design

摘要：

从热力学过程出发,通过引入单相及两相流声速计算模型,提出了基于实际气体的圆柱形混合室喷射器设计方法。用该方法计算出的喷射系数能与实验值较好吻合,误差在±17%内。新设计方法预测出必定存在一个使喷射系数设计值最大的最优混合室出口压力,为方便且快速确定该最优混合室出口压力与喷射器设计工况的关系,引入了最优扩压室升压比倒数。分别计算了水蒸气、氨、R290、R134a和R22圆柱形混合室喷射器常见工况下最优扩压室升压比倒数与膨胀比、压缩比的关系曲线,进而拟合出最优扩压室升压比倒数与膨胀比、压缩比的关系式。在喷射器设计过程中利用这些关系式可迅速算出最优扩压室升压比倒数,从而确定最优混合室出口压力,设计出高效喷射器。

关键词: 实际气体, 喷射器, 混合室出口压力, 热力学过程, 气液两相流, 优化设计