非平衡凝结流动的多流体模型

Multi-fluid Model for Non-equilibrium Condensing Flow

凝结两相流动中凝结过程与流场的强烈耦合使流动呈现高度的非平衡性,需要发展准确的多相流数理模型以更好地揭示非平衡凝结流动的过程机理。非平衡凝结流动过程中的相间滑移不仅会影响气相流场和凝结液滴的动力学行为,而且会影响凝结过程参数。建立一种适用于多组分凝结两相流动系统的多流体模型,同时引入气液相间速度滑移和两相温差的影响,对超音速喷管内湿蒸汽凝结流动进行验证与分析。结果表明,湿蒸汽两相流中相间滑移的存在对流动参数具有较大影响,提出的考虑相间滑移影响的多流体模型提高湿蒸汽凝结流动数值模拟的精度。在湿蒸汽凝结流动中,凝结初始阶段相间滑移和两相温差都非常显著,凝结结束后气液相基本接近平衡状态,相间滑移和气液相温差基本消失。

Spontaneous condensation flows are highly non-equilibrium processes, which has strong coupling with the gas flow field in the two-phase condensing flow. The development of accurate multi-phase numerical model is necessary to reveal the mechanism of the non-equilibrium condensation flow. The gas-liquid inter-phase slip not only has great influence on the gas flow and the motion trajectory of condensing droplet, but also would affect the condensation process. A multi-fluid condensing model is presented for the multi-component condensing system, of which the gas-liquid inter-phase velocity slip and the temperature difference is taken into account. The model is used for the numerical analysis of the wet steam condensing flow in supersonic nozzle. The simulation results showed that, the inter-phase velocity slip has significant effects in the two-phase wet steam flow, and the proposed multi-fluid model which takes the inter-phase slip into account can improve the simulation accuracy. In the wet steam flow, the inter-phase slip and temperature difference are very significant at the initial stages of condensation, and then the non-equilibrium properties almost disappear until the near equilibrium state is reached.