| 摘要: |
| 引射器对跨临界CO2引射制冷系统性能有极大的影响。本文考虑CO2两相引射器中存在的非平衡相变、超音速和壅塞等复杂流动现象，构建了CO2两相引射器的1D分布模型，并采用延迟均衡理论分析喷嘴中的非平衡相变过程。与实验结果比较显示，所建立的延迟均衡模型能够很好的预测引射器的性能。此外，通过与均衡模型的相比显示，在本文所选工况下，延迟均衡模型计算所得的主动流流量比均衡模型预测值低12.39%~25.30%，同时非平衡现象将延缓喷嘴中的膨胀过程，使得喷嘴出口压力比均衡模型预测值高。本文采用所建模型进一步分析了引射器的结构对性能的影响，结果显示在一定的工况下存在最优的混合室直径使得引射系数和升压比都较高；而当混合室直径一定时，较长的混合室有利于提高引射器的升压比。 |
| 关键词: 两相引射器 延迟均衡模型 非平衡相变 CO2 |
| DOI： |
|
|
| 基金项目:国家自然科学基金（51076120）资助项目。 |
|
| A CO2 Two-phase Ejector Model Based on Delayed Equilibrium Model |
| He Yang,Zhang Zaoxiao,Xue Changle,Zhang Yazhou,Deng Jianqiang |
| (State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University;State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University;School of Chemical Engineering and Technology, Xi'an Jiaotong University) |
| Abstract: |
| The ejector is key to the performance of the transcritical CO2 ejector refrigeration system. Considering the complex processes, such as metastable phase change, supersonic flow, and choking phenomena et al., in the CO2 two-phase ejector, a 1D distributed model was built in this paper and the delayed equilibrium theory was employed to analyze metastable phenomena in the motive nozzle. After the comparison with the relevant experiments data, the model was validated to be reliable to predict ejector performance. Compared with the homogeneous equilibrium model (HEM), the proposed model presented a 12.39%~25.30% lower critical mass flow rate. Meanwhile, the comparison results showed that the metastable phenomena would slow down the expansion process causing higher nozzle outlet pressure than that of the HEM simulation results. Moreover, the model is used to study the effect of the dimensions on the ejector performance and the results revealed that under a certain operating condition, an optimal mixing section diameter existed for both high entrainment ratio and pressure lift. Besides, a longer mixing section with a fixed mixing section diameter would increase the pressure lift ratio. |
| Key words: two-phase ejector delayed equilibrium model metastable phase change CO2 |
