| 摘要: |
| 本文针对CO2引射器主动流喷嘴渐扩段3个角度0.076o、0.306o、0.612o，耦合对比了均相平衡、延迟平衡以及摩擦模型，并与文献实验数据作比较，探讨了非平衡相变和壁面摩擦两种流动机制对相应角度下喷嘴延迟膨胀过程的主导作用。结果表明：在本研究范围内，渐扩段角度较小（θ1=0.076°）时，壁面摩擦是导致喷嘴延迟膨胀的主要机制；渐扩段角度处于中间值（θ2=0.306°）时，非平衡相变成为主导机制；渐扩段角度较大（θ3=0.612°）时。喷嘴膨胀过程接近于等熵膨胀；设计优化时需要采用相应的模型模拟。渐扩段角度较小时，延迟平衡耦合摩擦模型后发现喷嘴真实喉部后移至渐扩段，获课题组实验间接证实，且预测的临界质量流量显著低于均相平衡和延迟平衡模型预测值；渐扩段角度较大时3种模型的预测值差别不大。 |
| 关键词: 两相喷嘴 非平衡相变 摩擦 CO2 |
| DOI： |
| 投稿时间：2018-12-26 修订日期：2019-03-16
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| 基金项目: |
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| Research on the Mechanism of Delayed Expansion Process in a CO2 Two-phase Nozzle |
| Ma Li,Deng Jianqiang,Li Yafei |
| (School of Chemical Engineering and Technology, Xi'an Jiaotong University) |
| Abstract: |
| In this paper, the motive nozzles of a CO2 ejector with a diverging angle ranging from small to large (0.076°, 0.306°, and 0.612°) were investigated. Coupled models for the homogeneous equilibrium (HEM), delayed equilibrium (DEM), and wall friction model were presented and compared with the experimental data from related literature to analyze the dominant effects of the two flow mechanisms, non-equilibrium phase change, and wall friction on the delayed expansion process in the nozzle at corresponding angles. The results showed that within the ranges of this study, wall friction was the dominant mechanism of the delayed expansion process in the nozzle with a small diverging angle at the θ1 of 0.076°. Furthermore, the non-equilibrium phase change was the dominant mechanism in the nozzle with a middle diverging angle at the θ2 of 0.306°. In addition, the expansion process of the two-phase flow in the nozzle is close to the isentropic process for the large diverging angle at the θ1 of 0.612°. It is necessary for the design and optimization of the nozzle to choose a reliable model considering the dominant mechanism. When the diverging angle is small, the simulation results of the DEM coupled with a friction model indicated that the flow could choke the downstream of the minimum-area throat; this is verified by our experimental results. In addition, the critical mass flow rate predicted by the above model was lower than those of the HEM and DEM. The critical mass flow rates predicted by the three models indicated a barely noticeable difference for the larger diverging angle |
| Key words: two-phase nozzle non-equilibrium phase change friction CO2 |
