| Since air pollution and erosion contaminants from the roof, or the ground, the early rainwater pollution is serious, it can not be collected for directly used, if discharged directly pollution, the river would be polluted. Therefore the early rainwater treatment is extremely important. Vortex grit chamber and advection grit chamber process are very important structures in the sewage treatment. But, it is said that the vortex grit chamber has problems like water distribution difficulties, easily entangled fiber material on the impeller and energy consumption in a long time practical application. Also, it is difficult to deal with issues such as the sediment generated during sewage treatment; Advection grit chamber exists with large area, it own good effect but inefficiencies.Vortex- advection grit chamber is a novel treatment process used in the initial treatment of rainwater, which takes the grille, coagulate with dosing, vortex grit chamber and advection grit chamber organically linked together by line mode. And it has important significance to the treatment of early rainwater.In this paper, simulation of vortex grit chamber and advection grit chamber will based on the computational fluid dynamics(CFD, Computational Fluid Dynamics). It brings theory and design parameter for the vortex- advection grit chamber.This article takes Euler-Lagrangian method to establish the solid-liquid two-phase flow equations of vortex grit chamber, advection grit chamber and vortex- advection grit chamber.In the vortex grit chamber design process, this article achieve a smooth application of hydraulic paddle in the vortex grit chamber by writing UDF procedures, while in the process of calculation using multiple reference frame(MRF) technology. Under the certain conditions, single factor is controlled such as the flow rate of the water, paddle blade angle, the number of paddle blades and the distance from the paddle to the bottom of vortex grit chamber. The simulation results show that, when the vortex grit chamber influent flow rate of 1.0 m/s, the number of paddle blades 3, an inclination of 60 °, paddle from the bottom 50 mm, the highest efficiency.During the numerical of advection grit chamber, the phenomenon of reflux has been analyzed. The results show that reflux caused by baffle, which is near the water inlet is in favor of settling of the solid particles. So, this article discusses the impact of the advection grit chamber flow field when the baffle in a horizontal position of 0m, 0.5m, 1.0 m, 1.5 m, 2.0 m. It is concluded that when baffle in a horizontal position when at 1.5m, grit chamber sanding removal rate reach the highest.Based on the Simulation result of the vortex grit chamber and advection grit chamber, vortex- advection grit chamber was established by design parameters when the two chamber reach the highest sanding removal rate. And make some impact simulations. Final conclusion : the sanding removal rate of vortex- advection grit chamber can reach 78.83%, when the vortex grit chamber influent flow rate of 1.0 m/s, the number of paddle blades 3, an inclination of 60 °, paddle from the bottom 50 mm, and baffle in a horizontal position when at 1.5m with slope of 0.02. Then get the design parameters of vortex- advection grit chamber. When the water flow to expand to 1~1.3 times, the sanding removal rate of vortex- advection grit chamber grit can be 78%, desanding rate will decrease resulting in flow further increase. When water quality deterioration from 1~1.1 times, the sanding removal rate of vortex-advection grit chamber grit can be 78%, further deterioration of water quality will lead to deterioration in sanding removal rate. |
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