考虑相间滑移影响的湿蒸气自发凝结流动数值研究

Numerical investigation of wet steam spontaneous condensing flow with considering the velocity slip

建立了考虑相变、相间滑移等因素的双流体模型.应用该模型对二维拉伐尔喷管及Bakhtar叶栅中的湿蒸气自发凝结流动进行了数值模拟,其计算结果与实验结果整体上吻合较好,但部分计算结果与实验结果的差别仍表明对成核后液滴生长的模拟精度可以进一步提高.对喷管的研究表明,进口过冷度对自发凝结流动具有较大影响,进口过冷度越低,"凝结冲波"强度更低且自发凝结发生位置也将更靠近流道出口.而针对Bakhtar叶栅的研究则表明,膨胀比与入口过冷度对流动中自发凝结的发生的影响具有不同作用,入口过冷度的增加会使叶栅中自发凝结提前发生,而增加进出口膨胀比则会在一定能程度减弱这一效果.

A new dual-fluid model was proposed considering the phase transition along with the velocity slip between phases. Based on this dual-fluid model, numerical simulations were conducted on the flow field in 2D Laval nozzle as well as in Bakhtar cascade. The simulated results were shown to be of high consistency with the experimental results, but the existing difference still implied that the simulation accuracy of droplets growing could be improved further. The research on the flow in nozzle showed that the degree of supercooling at the inlet has great impact on the process of spontaneous condensation, i.e. lower degree of supercooling at the inlet will bring lower intensity of ＂condensing shock＂ and in the meantime, the position where condensation occurred would be closer to the exit of nozzle as well. The study of the condensing flow in Bakhtar cascade then inferred that the expansion ratio of the passage had opposite effect on the condensation compared with the degree of supercooling at the inlet. Namely, the increase of the inlet degree of supercooling will bring the occurrence of the spontaneous condensation forwards, but the ascent of the expansion ratio then will postpone the condensation.