基于MUSIG模型的气液两相流离心泵内部流动数值模拟

Numerical simulation on gas-liquid two-phase flow in centrifugal pump based on MUSIG model

为了解决气液两相流泵内部流动数值模拟中所采用的欧拉-欧拉双流体非均相流模型无法考虑气泡离散相粒子直径变化以及气相之间的聚合作用与破碎作用,导致在高含气量时的模拟结果与试验存在一定差距的问题,文中将一种新型的欧拉-欧拉双流体拓展模型,即MUSIG模型用于气液两相流泵内部流动的数值模拟,通过与气液两相流工况外特性试验数据对比发现,入口含气率在5%左右时,MUSIG模型计算得到的外特性曲线与试验结果整体趋势吻合较好;普通的欧拉-欧拉两相流模型在大含气率下与试验相差较大.基于MUSIG模型,分析入口含气率对内部流动特性的影响,发现入口含气率的增加会引起内流失稳和流线紊乱,气相逐渐聚集在前盖板与流道中间部位,最后引起能量损失,叶轮出口压力下降.这些现象会随着入口含气率增加而逐渐加剧,最终扬程与效率均会随着含气率增加而下降.含气率小于3%时,内流较稳定;当入口含气率为5%时,扬程下降至32 m,效率下降至55%,推测此时流道内气相聚合,生成气囊.

The Eulerian-Eulerian two-phase flow model used in the simulation of the the gas-liquid two-phase flow pump cannot consider the air bubbles diameter changing.There is a certain gap between the simulation result and the test when the gas content is relatively high.The MUSIG model,which is a new type of expansion model based on original Eulerian-Eulerian model,can calculate more accurately.Comparison with the experimental data shows that when the gas content is about 5%,the hydraulic characteristic curve calculated by the MUSIG model has a slight deviation from the experimental results,but the overall trend is in good agreement.Based on the original model,the flow cha-racteristics inside the pump for different IGVF(inlet gas volume fraction)show that the increase of the inlet gas content will cause entire flow instability and streamline turbulence;the gas phase will gradually accumulate in the middle of the should and the flow channel;the pressure of the impeller drops.These phenomena will gradually intensify with the IGVF increasing,and head and efficiency will decrease obviously.When the gas content is less than 3%,the internal flow is relatively stable;when the inlet gas content is 5%,the performance will suddenly drop,and the gas accumulation occurs in flow channel.