叶片数对倒伞曝气机曝气性能影响试验研究

Experiment on influences of number of blades on aeration performance of inverted-umbrella aerator

为了研究各不同状态下叶片数对倒伞曝气机曝气性能的影响,制作了叶片数分别为6枚和8枚的2个倒伞曝气机叶轮,进行了溶解氧试验来研究倒伞曝气机的曝气性能.通过改变曝气池液位高度及倒伞曝气机浸没深度,研究了不同叶片数下,标准氧总转移系数、标准充氧能力和标准动力效率的变化规律.结果表明:在同一转速下,8叶片倒伞曝气机的标准氧总转移系数和标准充氧能力明显高于6叶片的.倒伞曝气机的叶片增加,叶轮的抛洒强度增加,液体与空气的接触面积增大,氧传质效率得到有效提高.同时,靠近自由液面的液体波动加大,使液体与气泡间的相互作用更加剧烈,增大了湍动传质的能力.但是增加叶片数会使得消耗的功率增加,故相同转速下不同叶片数的倒伞曝气机的标准动力效率差别较小.研究为倒伞曝气机的经济运行提供参考.

In order to study the influence of the number of blades on the aeration performance of inverted-umbrella aerator under various flow conditions,two impellers respectively with 6 blades and 8 blades were fabricated for an inverted-umbrella aerator.Then,dissolved oxygen experiments were carried out to study the aeration performance of the aerator.The total oxygen transfer coefficient,standard oxygenation capacity and standard dynamic efficiency were measured at two numbers of blades by changing liquid level height in the aeration tank and immersed depth of the aerator.At the same rotative speed,the 8-blade aerator is subject to significantly higher standard oxygen total transfer coefficient and standard oxygenation capacity than the 6-blade aerator.When the number of blades increases,the impellers have a stronger throwing and sprinkling strength,and the contact area between the liquid and the air is expanded,thus a greatly improving efficiency of oxygen mass transfer is resulted.Additionally,the fluctuation of the liquid near the free surface is intensified,the interaction between the liquid and the bubbles becomes stronger,thus the turbulent mass transfer is enhanced.However,the increase of the number of blades will consume more power,consequently,the standard power efficiency of two aerators with two numbers of blades shows a little difference at an identical rotative speed.Nevertheless,the study provides a certain reference for the economical operation of an inverted-umbrella aerator.