| Oxidation ditch is widely used in wastewater treatment currently. Surface aerator is the core equipment in the oxidation ditch. It affects the efficiency of the oxidation ditch treating sewage directly. Numerical simulation is a new method of wastewater treatment research, because it can describe the flow field vividly and accurately. So the flow field of oxidation ditch was analyzed by FLUENT software in this article and the best working conditions were got.The standard k ?εmodel and multiple reference frame model and SIMPLEC algorithm were used to simulate the 3-D numerical simulation of the flow field of a 32m(L)×8m(W)×4m (H) oxidation ditch. According to the engineering requirements, the distribution of turbulent kinetic energy and the velocity field of the oxidation ditch were analyzed to get the best working conditions when the surface aerator power is 12 kW. Firstly, the key factors of influencing the flow field of oxidation ditch such as the impeller blade shape and number of the surface aerator, the immersion depth of the surface aerator and the radius of guide wall near the surface aerator were analyzed, the results showed that the best working conditions and the largest mixed force were obtained when the impeller blade shape is airfoil , the number was 10, the immersion depth of the aerator was 0.5m, and the radius of guide wall near the aerator was 0.5m. Secondly, the average velocity of the section and the bottom of oxidation ditch were analyzed by orthogonal experiment, the results showed that the impeller blade shape and number of the surface aerator were the most significant factors. The optimal combination appeared when the impeller blade shape was airfoil, the blade number was 10, the immersion depth of the aerator was 0.5m and the radius of guide wall near the surface aerator was 0.5m. The linear relation of the average velocity of the section of the oxidation ditch with the factors was educed by multiple linear regression:y =0. 1637+0.01456x1+0.1198x2-0.00355x3; The linear relation of the average velocity of the bottom of the oxidation ditch with the factors was educed by multiple linear regression:y =0 .06593+0.01121x1+0.03275x2+0.00195x3. Finally, in order to optimize the surface aerator further, the reverse angles of the airfoil impeller blade were optimized designed, the result showed that the flow field fit the engineering requirements most when the reverse angles was 20.By using the numerical simulation method, the flow characteristics of oxidation ditch were analyzed, and the priority of factors in the design was grasp better, the result had a significant forecast for the project, could avoid the poor working condition, and saving the energy consum- ption. |
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