微涡旋网格絮凝池特性参数的数值模拟与过程优化

发布时间：2018-01-04 23:10

本文关键词：微涡旋网格絮凝池特性参数的数值模拟与过程优化　出处：《哈尔滨理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：净水厂的工艺过程一般包括混合、絮凝、沉淀、过滤和消毒。絮凝是整个过程的关键阶段,它直接决定了水厂出水效果。微涡旋网格絮凝池是应用最为广泛的絮凝池形式之一,因此,对网格絮凝池设计特性参数进行数值模拟与过程优化显得尤为重要。本文在絮凝动力学基础上,利用计算流体力学软件(Fluent)对网格絮凝池进行模拟计算,确定最优设计参数,用以优化工程设计。本文以微涡旋网格絮凝池各设计参数为变量,利用Fluent软件进行数值模拟,采用标准k-ε模型及Realizable k-ε模型作为数值模拟方法,将湍动能k、湍动能耗散率ε、速度梯度G'及涡旋尺寸λ作为絮凝效果评价指标,通过分析流体运动状态探讨最佳设计参数。研究结果表明:(1)在絮凝池内安放网格会大幅度提高能量利用率,改善水流的湍动状态,增加微涡旋数量,且网格应悬空置于絮凝池竖井中;(2)在微涡旋网格絮凝池单层栅条二维数值模拟中,对栅条宽度5 mm-80 mm,栅条间距20 mm-120 mm,入口流速0.06 m/s-0.3m/s进行单因素模拟,当栅条宽度80 mm,栅条间距20 mm,入口流速0.3 m/s时,其产生的湍动能及湍动能耗散率最大,但当其产生的水流剪切力过大时,会导致已经产生的絮体被破坏,因此应将其控制在一定范围内,保证良好的絮凝效果;(3)合理的网格板间距对于提高输入能量的利用率有良好的促进作用;(4)在网格絮凝池三维模拟中,提出了四组具有较好絮凝效果的设计参数:栅条宽度50 mm,栅条间距120 mm,入口流速0.3 m/s,网格板间距200 mm;栅条宽度50 mm,栅条间距110 mm,入口流速0.3 m/s,网格板间距700 mm;栅条宽度70 mm,栅条间距40 mm,入口流速0.2 m/s,网格板间距300 mm;栅条宽度40 mm,栅条间距20 mm,入口流速0.08 m/s,网格板间距700 mm。
[Abstract]:The process of water purification plant generally includes mixing, flocculation, precipitation, filtration and disinfection. Flocculation is the key stage of the whole process. The micro-vortex grid flocculation tank is one of the most widely used flocculation pool forms. It is very important to simulate and optimize the design characteristic parameters of grid flocculation tank. This paper is based on the flocculation kinetics. The computational fluid dynamics software (CFD) was used to simulate and calculate the grid flocculation tank, and the optimal design parameters were determined to optimize the engineering design. In this paper, the design parameters of the micro-vortex grid flocculating tank were taken as variables. The standard k- 蔚 model and Realizable k- 蔚 model are used to simulate the turbulent kinetic energy k and the turbulent kinetic energy dissipation rate 蔚. Velocity gradient G 'and vortex size 位 are used as evaluation indexes of flocculation effect. The results show that the grid placement in the flocculation tank can greatly improve the energy utilization rate, improve the turbulent state of the water flow and increase the number of micro-vortices. And the grid should be suspended in the flocculation pool shaft; (2) in the two-dimensional numerical simulation of single-layer grid in a micro-vortex grid flocculation cell, the width of the strip is 5 mm-80 mm and the gap between the bars is 20 mm-120 mm. The inlet velocity of 0.06 m / s -0.3 m / s was simulated by a single factor, when the width of the bar was 80 mm, the gap between the bars was 20 mm, and the velocity of inlet was 0.3 m / s. The turbulent kinetic energy and the dissipation rate of turbulent kinetic energy are the largest, but when the flow shear force is too large, the produced flocs will be destroyed, so it should be controlled within a certain range to ensure good flocculation effect. 3) reasonable grid spacing can promote the utilization of input energy. 4) in the three-dimensional simulation of grid flocculation tank, four design parameters with good flocculation effect are proposed: the width of grid strip is 50mm, the spacing of grid strip is 120mm, and the inlet velocity is 0.3 m / s. Mesh spacing 200mm; The width of the bar is 50 mm, the gap between the bars is 110 mm, the inlet velocity is 0.3 m / s, and the grid spacing is 700 mm; The width of grid strip is 70 mm, the gap of grid bar is 40 mm, the inlet velocity is 0.2 m / s, the spacing of grid plate is 300 mm; The width of the bars is 40 mm, the gap between the bars is 20 mm, the inlet velocity is 0.08 m / s, and the grid spacing is 700 mm..
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ085.4

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