The Axial-flow Impeller Design Based On Lifting-surface Theory

The mixing operation is widely used in aspects of industrial production, its complexity is that its principle involves heat transfer, mass transfer, chemical reactions, and other process. The axial-flow impeller has characteristics of large flow, low shear, low power, it’s applicable in the solid-liquid suspension and the operation with changeable surface height.Since1980s,the axial-flow propeller has been developed and got the unanimous approval for its excellent mixing performance, has good prospects in practical applications, but we lack awareness of the internal flow pattern in mixing tanks, therefore it’s significant to deepen the research on axial-flow propeller. There is no depth study on the mechanism of solid-liquid suspension. Axial mixing operation in suspension, suspension mechanism of solid particles by the lift has been discussed.In this paper, the lifting surface theory is used in calculation on lift in full suspension and state of part of the suspension, the mechanical model of axial mixing suspension is established. According to the mechanical model, shape of the axial-flow impeller is made, the turbulence model of axial-flow field is set up and with the help of computational fluid dynamics software FLUENT, simulation for solid-liquid suspension mixing of quartz sand-water system has been done. Effects for the diameter of the impeller, width of paddle and reversed angle and height of installation to the axial-flow field are done. Solid-liquid suspension mixing operation system contains two phases:quartz sand and water. The particle diameter is110μm, its density is2650kg/m3,and particle volume fraction is15%.Suspension density is1248kg/m3.Flat-bottomed cylindrical stirred tank is used, its diameter is0.6m, the same with the reactor’s liquid level. Standard k-ε model is used to simulate liquid flow and the suspended process is simulated by Eulerian multiphase model. The viscous resistance with water and gravity of particles will increase energy consumption. In addition, the concentration of solid particles in the stirred tank changes with the radius, liquid height, the concentration of solid particles at the center and beside the wall are higher than other regions of the tank. The axial-flow impeller designed based on lifting-surface theory provide a reference for industrial operations.