Rushton桨搅拌槽内轴弯矩的数值模拟

针对搅拌槽内流体流动、柔性结构振动和流动流体与柔性结构相互作用(流固耦合)的特征,分别采用计算流体动力学(不考虑结构振动)、计算结构动力学(不考虑流体作用)和两种计算动力学相互瞬态耦合模拟(同时考虑结构振动和流体作用)研究Rushton桨搅拌轴的弯矩幅值平均和波动特性。研究结果表明:搅拌槽内流体充当了振动的阻尼作用,抑制了搅拌桨轴侧向振动的幅度,但主体流动的低频宏观不稳定性显著地增加了搅拌桨轴旋转的不稳定性,同时搅拌桨轴侧向振动增加了搅拌桨叶片上的流体载荷不稳定性,但对不均衡性影响很小;弯矩流体成分(来源于流体压力和粘性力)与结构成分(来源于结构重力和惯性力)之间夹角是随机的,但平均夹角接近于90°;耦合模拟结果与实验数据吻合较好,且明显优于计算流体动力学和计算结构动力学分离模拟计算结果。研究结果有助于深入理解搅拌槽内流固耦合对搅拌轴弯矩的影响,对搅拌设备的机械设计具有指导意义。

Numerical Simulation of Moment Acting on Shaft Used in Stirred Vessel with Rushton Turbine

With respect to the characteristics of fluid flowing in stirring vessel,vibration of flexible structure and interaction of fluid flowing and flexible structure（FSI）,by using computational fluid dynamics（CFD）,computational structure dynamics（CSD） and coupling simulation of CFD and CSD,the average and fluctuating values of moment acting on the shaft for Rushton impeller were studied in this article.The result had shown that the fluid in vessel played the role of damping action so that the amplitude of lateral vibration of agitator was restrained.But,macro instability in low frequencies in bulk flow enhanced the instability of impeller’ s rotation.At the same times,the lateral vibration of the impeller increase the instability of fluid loading on the blades of impeller,however,it has a little effect to the balance of loading.Although,the angle between the vectors of moment induced from fluid（pressure and viscosity） and structure（density and inertia force） is random,the average one is close to 90°.The results from coupling simulation and experiment are in good agreement,and the result from coupling simulation was obviously better than that from CFD and CSD carried out separately.The result of investigation presented herein can help to understand the effect of fluid and solid interaction to the moment acting on shaft,so it can be used as the guidance for design of stirring equipment.