关键词: 自吸射流, 非均相, 搅拌桨, 计算流体力学, 混合

Abstract: As a new type of stirred device, the self-priming jet stirred tank has potential engineering application value in heterogeneous mixing enhanced process. The engineering design and industrial application of self-priming jet stirred tank were restricted by the insufficient research on the mixing characteristics. In this study, the liquid-liquid heterogeneous mixing process in self-priming jet stirred tank was investigated using numerical simulation and experiment. Water and oil were set as continuous phase and dispersed phase, respectively. Realizable k-ε turbulence model and Eulerian-Eulerian multiphase flow model were used to numerically simulate the liquid-liquid heterogeneous flow field in the self-priming jet stirred tank. The enhanced mass transfer mechanism of the self-priming jet impeller was investigated. The results showed that the dimensionless velocity on the axis of self-priming jet pipe was less affected by the stirring speed and the dispersed phase holdup. However, the single-phase flow without oil phase had lower velocity inside the self-priming jet pipe and higher velocity outside the pipe. The flow field and dispersed phase distribution in the stirred tank were significantly influenced by the inclination angle β of self-priming jet pipe. When β<0°, the self-priming flow was formed at lower end of the pipe and the jet was formed at upper end of the pipe, which was unfavourable to the radial mixing of oil and water in the stirred tank. When β=0°, the fluid velocity in pipe was close to the impeller speed, and there was no self-priming and jet flow. The impeller only produced the stirring function, which was not good to axial mixing. When β>0°, the self-priming flow was formed at upper end of the pipe and the jet was formed at lower end of the pipe. The high oil phase fluid was sucked by the self-priming jet pipe, and was jetted downward into the low oil phase fluid. The oil phase moved upward by buoyancy. For the self-priming jet impeller with β>0°, the turbulent kinetic energy at the bottom of stirred tank was effectively increased. β>0° was beneficial to eliminate the flow inhomogeneity and oil-water heterogeneous mixing process was enhanced. When β=30°, the fluid region, which dimensionless phase fraction was 0.95~1.05, accounted for 81.88% of the stirred tank volume, and the oil phase distribution was more uniform along the axial and radial directions.

Key words: self-priming jet, Heterogeneous, agitator blade, computational fluid dynamics, mixing