The Numerical Simulation Research Of Solid-Liquid Two-Phase Flow Simulation On The New Rotational Flow Grit Chamber

To ensure the follow-up one and two pretreatment normal operation, the gritchamber is one of the necessary pre-treatment structures in the sewage treatmentplant, which is used to remove a certain particle size of sand in the sewage. Therotational flow grit chamber, as a class of the grit chamber, is widely used insewage treatment process, because of its high desand effect, small groundoccupation and low power consumption.In order to optimize the sand removal efficiency, operation and structuralparameters of the rotational flow grit chamber, and improve its structure in actualoperation, based on small scale model, the subject combined with the subject ofNational863Project, conducts the numerical study of the rotational flow gritchamber: In view of CFD theory, the geometric model and the meshing strategy ofthe new rotational flow grit chamber are established by the Gambit software. Theinternal liquid flow distribution of the rotational flow grit chamber is simulated bythe RNG k-ε turbulence model and the MRF model in Fluent. And based on theliquid flow field and the discrete phase model, the different and particle sizedistribution is defined by the Rosin-Rammler distribution function, thenthree-dimen-sional flow field and sand trajectory of the rotational flow gritchamber are simulated successfully, and compared with the experimental values ingood agreement.In the numerical simulation of the new rotational flow grit chamber, based onthe characterization of its internal three-dimensional liquid flow field distribution,grit removal efficiency and sand trajectory etc, the relevant factors of the runningof the impact of the rotational flow grit chamber: a single factor and orthogonal ex-periments are conducted in①water hydraulic conditions;②the number of mix-ing blades piece;③the stirrer speed;④mixing blade piece from the bottom of thedistance;⑤The impeller radius;⑥the inclination of the impeller. The resultsshowed that:(1) the operation of the rotational flow grit chamber is mainly basedon the forced vortex mechanism. In the pressure field, the pressure difference willaffect the movement of the sand; In the velocity field, two flow regimes are in the chamber: the horizontal circulation and axial circulation.(2) When the direction ofrotational movement of the impeller is different, the formation of axial circulationflow field are quite different, which a clockwise rotation contribute to thesettlement and removal of sand.(3) According to the influent flow rate and stirrerspeed relationship, the other factors under certain conditions, water flow rate is keyfactor for sand deposition and removal, and a certain impeller speed will affect thesubsequent stages of sand running and remove.(4) According to the agitatorinclination changes,30°and60°are similar on the removal of sand, and the singlefactor and orthogonal experiments are conducted based on the two on the impact ofthe relevant factors of the rotational flow grit chamber, and the correlation analysisis conducted, then the best sand removal efficiency of the rotational flow gritchamber is obtained：①combined with the change curve of the various influencingfactors on sand removal effect, inclination of60°is the experimental subjects;②The orders of the impact factors of the grit removal efficiency are: water flow rate>impeller speed>impeller from the bottom distance>impeller radius> the number ofmixing blades piece;③respectively, the best running conditions of the rotationalflow grit chamber is: water flow rate is0.09m/s, the number of mixing blades pieceis6, the impeller speed is24rpm, the impeller from the bottom distance is30mm,and the impeller radius is124mm;④The grit removal efficiency is88.89%underthe optimal conditions.