Abstract:The problems, such as too high energy consumption for oxidation ditch operation and how to decide submerged propellers installation position, exist in sewage treatment plants currently, thus the flow in an oxidation ditch was simulated based on the Navier-Stokes equations, standardturbulence model and SIMPLE algorithm. The threedimensional submerged propeller model was built by the existing blade pattern drawing, and the fluid domains were meshed with unstructured tetrahedral cells. The shaft power of submerged propeller and the velocity distribution in various crosssections of the oxidation ditch were estimated under different working conditions; meanwhile, the flow field driven by the propeller was investigated as well. The results indicate that on the premise of the submerged propeller installation parameters unchanged, altering the installation position of submerged propeller can avoid the back mixing phenomenon caused from a too strong driving force. Besides, the sludge deposition problem, which is caused from too low flow velocity resulted by too much attenuation of the driving power in the bends, also can be solved. By properly adjusting the number of submerged propellers, a minimum power density can be determined to meet the driving force needed for mixing. Thus not only the velocity in the oxidation ditch has met the requirement, but also the minimum energy consumption has been achieved. The study can provide a theoretical guidance for determining the installation position and number of submerged propellers.
[1]曹瑞钰,付见中.改善氧化沟流速分布的措施[J].中国给水排水,2001,17(2):16-18.Cao Ruiyu,Fu Jianzhong.Measures for improving velocity distribution in oxidation ditch[J].China Water & Wastewater,2001,17(2):16-18. (in Chinese)[2]田飞,施卫东,陈斌,等.污水处理搅拌机不同转速下的搅拌性能研究[C]//第四届全国水力机械及其系统学术会议论文集.兰州:兰州理工大学,2011:494-497.[3]施卫东,田飞,陈斌.带导流壳的污水处理搅拌机流动分析与试验[J].农业机械学报,2011, 42(3):96-99.Shi Weidong, Tian Fei, Chen Bin.Flow analysis and measurement of wastewater treatmentmixer with dome[J].Transactions of the Chinese Society for Agricultural Machinery, 2011, 42(3): 96-99. (in Chinese)[4]张羽,黄卫东,勾全增,等.计算流体力学在氧化沟设计中的应用[J].工业用水与废水,2009,40(1):49-53.Zhang Yu,Huang Weidong,Gou Quanzeng,et al.Application of computational fluid dynamics in design of oxidation ditch[J].Industrial Water & Wasterwater,2009,40(1):49-53.(in Chinese)[5]杨华展,王涛,邓荣森.一体化氧化沟弯道流态特性研究[J].重庆建筑大学学报,2007,29(3):106-109.Yang Huazhan,Wang Tao,Deng Rongsen.Research on flow characteristic of curve channel of integrated oxidation Ditch[J].Journal of Chongqing Jianzhu University,2007,29(3):106-109. (in Chinese)[6]Yang Yin,Yang Jiakuan,Zuo Jiaolan,et al.Study on two operating conditions of a fullscale oxidation ditch for optimization of energy consumption and effluent quality by using CFD model[J].Water Research,2011,45(11):3439-3452.[7]Fan Long,Xu Nong,Wang Zhiqiang,et al.PDA experiments and CFD simulation of a labscaleoxidation ditch with surface aerators[J].Chemical Engineering Research and Design,2010,88(1):23-33.[8]赵星明,王萱,王爱军.氧化沟弯道水流特性研究[J].环境科学与技术,2008,31(4):104-106.Zhao Xingming,Wang Xuan,Wang Aijun.Flow behaviors in channel of oxidation ditch[J].Environmental Science and Technology,2008,31(4):104-106. (in Chinese)[9]许丹宇,张代钧,陈园,等.卡鲁塞尔氧化沟液-固两相流动混合物模型与两相水力特性模拟[J].环境科学学报,2008,28(12):2622-2627.Xu Danyu,Zhang Daijun,Chen Yuan,et al.A fluid and solid twophase flow model and modeling of a carrousel oxidation ditch[J].Acta Scientiae Circumstantiae,2008,28(12):2622-2627. (in Chinese)[10]Liu Yanchen,Shi Hanchang,Shi Huiming,et al.Study on a discretetime dynamic control model to enhance nitrogen removal with fluctuation of influent in oxidation ditches[J].Water Research,2010,44(18):5150-5157.[11]邓荣森.氧化沟污水处理理论与技术[M].北京:化学工业出版社,2006.