Effect of the Impeller Pitch of Double-layer Improved Propeller on Flow Field in the Stirred Tanks
Particle image velocimetry was used to experimentally study the characteristics of the flow field in the stirred tank at different impeller pitches C2,and the large eddy simulation model,standard k-ε model and RNG k-ε model were used to simulate the flow field in the tank,respectively.The research results show that the impeller pitch has a great influence on the flow streamlines and velocity distribution in the tank.When the impeller pitch C2=0.23H(Hrepresents the liquid level height),affected by the upper impeller discharge and entrainment effects,the vortex of the lower impeller zone cannot be formed,and the mixing effect of materials in the tank would be poor;When the impeller pitch C2=0.26H,compared with C2=0.23H,the high-speed zone in the upper impeller zone increases by about 20％,the high-speed zone in the lower impeller zone increases by nearly 25％,and the lower impeller zone begins to form regional self-circulation.When the impeller pitch increases to C2=0.29H,low-speed vortices and flow dead zone gradually appear between two propellers,meanwhile,the mixing efficiency decreases.By comparing the position at r/T(r/T represents the circumferential distance ratio)=0.4,it was found that the simulation results using the large vortex simulation model are closer to the experimental results of the flow field in the stirred tank.The research results provide a reference for the practical application of this stirring impeller.
propeller impellerstirred tankimpeller pitchparticle image velocimetrylarge eddy simulationflow field
万方数据
