叶片形状对倒伞曝气机性能的影响

Influence of blade shape on performance in inverse umbrella aerator

为了探究直叶片和倾斜叶片对倒伞曝气机性能的影响,获得不同叶片形状倒伞曝气机驱动下氧化沟的流场特性,以1个符合几何相似、运动相似和动力相似理论的缩比双倒伞曝气机驱动下的氧化沟模型为研究对象,采用VOF自由液面模型与标准k-ε湍流模型相结合的方法,对不同叶片形状的倒伞曝气机驱动下的氧化沟内部流动进行了三维数值模拟.结果表明,2类倒伞曝气机消耗的功率相近,叶片形状的不同影响着倒伞曝气机的充氧能力和推流能力:直叶片倒伞曝气机驱动下,氧化沟过轴截面的气相体积分数较倾斜叶片大0.66%;直叶片倒伞曝气机对表层水域的推动能力较强,而倾斜叶片倒伞曝气机则对底层流体有较强的推动能力,沟底死水区相较于直叶片倒伞曝气机减小0.70%,且倒伞曝气机附近的流体能以较快的速度流向壁面;在双倒伞曝气机驱动下,氧化沟内的流动呈对称分布,下游倒伞曝气机能够明显提升和加速来流速度.

In order to study the effect of radial straight blade and leaned blade on the performance of inverse umbrella aerator and obtain the flow characteristic of an oxidation ditch driven by two inverse umbrella aerators with different kinds of blade shape,a lab scale oxidation ditch according with geometric similarity,kinematic similarity and dynamic similarity was taken as the research object. The volume of fluid（ VOF） model was adopted and the standard k-ε turbulence model was applied to close the governing equations. Through changing the blade shape of inverse umbrella aerator,three-dimensional numerical simulations were conducted. The results show that the power assumption of these two kinds of inverse umbrella aerators is much the same,the blade shape has a significant impact onoxygenation capacity and plug-flow capacity on the inverse umbrella aerator. Under the drive of inverse umbrella aerator with radial straight blade,the gas volume fraction of the section crossing the driving shaft in the oxidation ditch is 0. 66% higher than that in the oxidation ditch driven by the inverse umbrella aerator with leaned blade. While the inverse umbrella aerator with radial straight blade has a stronger ability to promote the fluid near the surface,the inverse umbrella aerator with leaned blade does better on driving fluid at the bottom of the ditch,with the dead water zone 0. 70% less than that in the ditch driven by the inverse umbrella aerator with radial straight blade. The fluid stirred by the inverse umbrella aerator with leaned blade flows to the wall at a higher speed. The flow distribution of the oxidation ditch driven by two inverse umbrella aerators is symmetrical. The downstream inverse umbrella aerator has an ability to lift and accelerate the incoming flow.