侧入式搅拌槽中多相流流场特性的数值模拟

运用计算流体力学(CFD)技术对不同安装偏角的侧入式搅拌反应器中单相及多相流场进行了数值模拟。模拟结果表明,典型安装偏角下,搅拌槽内流场是由内部围绕搅拌槽中心的高速环形上升流和外部沿搅拌槽壁面的低速下降流组成的大循环流。水平偏角既增加了整个搅拌槽流场的平均速度,有利于固体颗粒在整个搅拌槽内的悬浮性能,又增大了槽底高速流体区域的面积,因而改善了槽底固相沉积状况。竖直偏角增大了槽底高速流体区域的面积,并对槽底施加一定的冲刷作用,从而进一步降低了槽底固相沉积的可能性。无安装偏角时槽底固含率最多的地方主要积聚在搅拌器下方区域。搅拌器在水平偏角θ=10°,竖直偏角φ=5°时槽底大部分区域的固含率分布较均匀,仅在槽底搅拌器右侧的壁面区域存在小面积的固含率较高区域,在该安装偏角下整个搅拌槽的固液悬浮性能及防止底部固相沉积性能达到最佳。

Numerical simulation on field characteristics of multiphase flow in side-entering stirred tank

Single phase and multiphase flow fields in side-entering agitation reactor with different installation angles of agitators were simulated numerically by CFD technology. The results showed that, with the typical installation angle of agitator, the flow field was a big circular flow combined with two parts, which were the internal upwelling flow with high speed and the external downwelling flow. The horizontal dip angle of agitator increased the average speed of the whole flow field, which favored the suspension situation of solid particles. It also enlarged the area of the high speed flow at the tank bottom, which improved the aggradation situation of solid phase. Meanwhile the vertical dip angle enlarged the area of the high speed flow at the tank bottom too, and flushed the tank bottom, therefore further reduced the possibility of aggradation. While there was no dip angle, the area of highest solid ratio mainly laid under the agitators. When the horizontal dip angle was 10°and vertical dip angle was 5°,the solid ratio of most areas at the tank bottom was homogeneous distribution, except some areas at the right side of the agitators near the tank wall, where the solid ratio was higher. And with this installation angle, the quality of solid-liquid suspension and the ability to avoid the aggradation of solid at the bottom could be the best.