Carrousel氧化沟流场的数值模拟及断面优化研究

发布时间：2018-10-15 11:28

【摘要】：氧化沟是污水处理中常见的一种工艺形式,运用非常广泛。在实际运行过程中氧化沟工艺水力流态复杂,容易在弯道及前后的直段形成滞水区,导致污泥沉积,从而降低氧化沟内的容积利用率及处理效果,影响出水水质。本论文利用CFX软件进行氧化沟流场的三维数值模拟,研究氧化沟的水流特性,通过对氧化沟三维流动特性的分析为氧化沟的设计与运行提供行之有效的参考意见。本论文采用RNG k-ε湍流模型和多重参考坐标系模型(MRF),并采用SIMPLE算法,对氧化沟内的流场进行三维数值模拟。首先,对氧化沟表面曝气机叶片扭转角为30°和-30°两种工况下的氧化沟流态进行模拟。研究发现当曝气机叶片扭转角为30°时,氧化沟内的曝气更加充分,氧化沟底部流速大于0.3m/s的区域更大,发生污泥沉积的区域更小。其次,固定曝气机叶片扭转角度为30°,对曝气机位于氧化沟端部中间和氧化沟端部下游两种工况下的氧化沟流态进行模拟。研究发现当表面曝气机位于氧化沟端部中间时,氧化沟沟底流速大于0.3m/s的区域较大,不易发生污泥沉积现象。然后,固定曝气机叶片扭转角度为30°且曝气机位于氧化沟端部中间,研究在曝气机侧是否设置导流墙对氧化沟流态的影响。研究发现设置半圆形导流墙时,导流墙后容易产生污泥堆积,水流速度极低,因此建议将导流墙设置于流道中间或者不设置导流墙。最后,将氧化沟内侧横断面设置为半径分别为R=1m、2m、3m的半圆形,研究氧化沟内流体速度流场,发现均可使氧化沟内沟底流体平均流速增大,不易产生污泥沉积。本文运用数值模拟的方法研究了各因素对氧化沟流动特性的影响规律,对工程实践有着不可或缺的预测意义,避免较差工况的产生,节约能耗。
[Abstract]:Oxidation ditch is a common process form in wastewater treatment and is widely used. The hydraulic flow state of oxidation ditch process is complex in the actual operation process, and it is easy to form the stagnant water area in the bend and the straight section before and after, resulting in sludge deposition, thus reducing the volume utilization rate and treatment effect in the oxidation ditch, and affecting the effluent quality. In this paper, the three-dimensional numerical simulation of oxidation ditch flow field is carried out by using CFX software, and the flow characteristics of oxidation ditch are studied. Through the analysis of three dimensional flow characteristics of oxidation ditch, an effective reference is provided for the design and operation of oxidation ditch. In this paper, RNG k- 蔚 turbulence model and multiple reference coordinate system model (MRF), and SIMPLE algorithm are used to simulate the flow field in oxidation ditch. Firstly, the flow state of oxidation ditch was simulated under the conditions of 30 掳and -30 掳torsion angle of aerator blade on the surface of oxidation ditch. It is found that when the blade torsion angle of aerator is 30 掳, the aeration in the oxidation ditch is more adequate, the area where the flow velocity at the bottom of the oxidation ditch is larger than 0.3m/s, and the area where sludge deposition occurs is smaller. Secondly, the blade torsion angle of the fixed aerator is 30 掳. The flow state of the aerator is simulated under the two working conditions of the oxidation ditch end and the lower end of the oxidation ditch. It is found that when the surface aerator is in the middle of the end of the oxidation ditch, the flow rate at the bottom of the oxidation ditch is larger than that of 0.3m/s, and sludge deposition is not easy to occur. Then, the blade torsion angle of the fixed aerator is 30 掳and the aerator is located in the middle of the oxidation ditch. The effect of the diversion wall on the flow state of the oxidation ditch is studied. It is found that when the semi-circular diversion wall is installed, sludge accumulation is easy to occur behind the diversion wall and the flow velocity is very low. Therefore, it is suggested that the diversion wall should be placed in the middle of the channel or not. Finally, by setting the inner cross section of the oxidation ditch to a semicircle with a radius of 1 m ~ 2 m ~ 3 m, the flow field of the fluid velocity in the oxidation ditch is studied. It is found that the average flow velocity of the bottom fluid in the oxidation ditch can be increased and sludge deposition is not easy to occur. In this paper, the influence of various factors on the flow characteristics of oxidation ditch is studied by means of numerical simulation, which has an indispensable predictive significance for engineering practice, avoids the generation of poor working conditions and saves energy consumption.
【学位授予单位】：西华大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X703

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