撞击流反应器内幂律流体流动特性的数值模拟

采用数值模拟方法对撞击流反应器内幂律流体的流动特性进行研究，分析了不同喷嘴间距和入口流速下清水和不同质量分数幂律流体的径向射流扩展率、径向速度衰减率、剪切应力、表观黏度等分布规律，研究表明：幂律流体中径向射流的径向速度分布规律与清水径向射流相似。随喷嘴间距的增大，扩展率增大，径向速度衰减率减小，平均剪切应力呈先增大后减小的变化规律，其中L=3D时平均剪切应力值最大，更利于流体混合。入口流速越大，扩展率越小，径向速度衰减率越大，平均剪切应力也随之增大。幂律流体的平均剪切应力大于清水，且随质量分数的增大，其扩展率增大，为清水扩展率的1.3~3.3倍，而幂律流体的径向速度衰减率从-1.268~-1.125降低到-1.144~-1.082，逐渐小于清水。幂律流体径向射流区域的剪切应力呈“M”形分布，表观黏度则呈“W”形分布，流体的流变性质对撞击流反应器内流体的流动规律影响显著。

Numerical simulation of power-law fluid flow characteristics in impinging stream reactor

The flow characteristics of power-law fluid in impinging stream reactor are studied by numerical simulation method. The distribution laws of radial jet spread rate, radial velocity decay rate, shear stress and apparent viscosity of clean water and power-law fluid with different mass fraction under different nozzle spacing and inlet velocity are analyzed. The research shows that the radial velocity distribution law of radial jet in power-law fluid is similar to that of clear water radial jet. With the increase of nozzle spacing, the spread rate increases and the radial velocity decay rate decreases. The average shear stress increases first and then decreases. When L=3D, the average shear stress is the largest, which is more conducive to fluid mixing. With the increase of inlet velocity, the spread rate decreases, and the radial velocity decay rate and average shear stress increase. The average shear stress of power-law fluid is greater than that of clean water, and with the increase of the mass fraction of power-law fluid, the expansion rate of power-law fluid increases, about 1.3—3.3 times that of clean water, but the radial velocity decay rate of power-law fluid decreases from -1.268—-1.125 to -1.144—-1.082, gradually smaller than that of clean water. The shear stress in the radial jet region of power-law fluid is “M” shaped distribution, and the apparent viscosity is "W” shaped distribution. The rheological properties of the fluid have a significant impact on the flow law of the fluid in the impinging stream reactor.