Optimizing The Structure Of Multistage Rotor-Stator Mixer To Strengthen The Mixing Of Highly Viscous Fluids

How to achieve uniform mixing of highly viscous fluids with low energy consumption is a major industry demand and one of the hot spots of mixing research.Due to the small shear gap,the multistage rotor-stator mixer can better avoid the formation of dead zones and has good self-cleaning ability.And it is widely used in the industry to mix highly viscous materials.Compared with the stirred tank,the rotor-stator mixer has a higher cost;therefore,in order to enable the multistage rotor-stator mixer to mix highly viscous fluids more efficiently under high throughput to improve its cost performance,the method of computational fluid dynamics combined with part of the experimental verification is used to optimize its structure.The mixing index and power consumption are used to evaluate the performance of the mixers.Firstly,the influence of different operating parameters and structural parameters on the mixing of highly viscous Newtonian fluids in the multistage rotor-stator mixer is studied.The torque sensor combined with the rotor speed control method is used to measure the shaft power,which verifies that the CFD simulation method can accurately simulate the mixing process.The simulation results show that the flow rate,rotor speed and the number of mixing units have significant effects on the performance of the mixer,while the performance of the mixer is less affected by the fluid viscosity,the number of rotor-stator teeth,the teeth angle and other teeth structures.Under the condition of 10times the conventional processing capacity（residence time of 1.1 s）,the mixing index of the mixer with optimized rotor-stator structure is 0.455 at 3.33 r·s^-1（power consumption is 2403 W）and is 0.903 at 16.67 r·s^-1（power consumption is 18925 W）.The mixing index and power consumption of the mixer are dimensionlessly correlated with the flow rate,rotor speed,and the number of mixing units,and the correlation is obtained by fitting.For the mixing index and power consumption,the average absolute relative error between the simulated value and the fitted value is 3.4%and 1.4%,respectively.Furthermore,in order to obtain a better mixing effect under low power consumption,the mixing performance of the multistage rotor-stator mixer with a distributor under the working conditions of highly viscous fluid was studied.The simulation results show that the mixer with an optimal distributor（X1-T1）can increase the mixing index from 0.455 without the distributor to 0.85 at 3.33 r·s^-1.The power consumption is increased from 2403 W without the distributor to 2556 W with the distributor.Based on X1-T1,the effects of different rotor-stator structural parameters and operating parameters on the mixing performance of the mixer are studied.The simulation results show that the flow ratio of the two fluids,fluid viscosity,shear gap,and power law of the fluid have certain effects on mixing performance of the mixer.Under the condition of the shear gap of 0.0085 m,straight blades are used to increase the circumferential mixing,and the mixer with 4-stage straight blades and 16-stage rotor-stator（16Y-4P）has the highest mixing index.By increasing the rotor speed of the16Y-4P to 6.67 r·s^-1,the mixing index of the mixer reaches 0.98,and the power consumption is 4171 W;the mixing index of the 20-stage rotor-stator mixer without distributor and straight blades at 6.67 r·s^-1 is 0.662,and the power consumption is 4468W.Therefore,this article optimizes the structure of the multistage rotor-stator mixer.The use of distributors and straight blades improves the performance of mixer with highly viscous fluids,achieves low power consumption and high throughput,and provides a basis for further industrial applications.