运行参数对倒伞曝气机曝气性能影响试验

转速、浸没深度和液位高度对倒伞曝气机曝气性能的影响较大,为了研究各影响参数协同作用下倒伞曝气机曝气性能的变化情况,该文通过试验研究了不同转速、浸没深度和液位高度对曝气性能的影响。研究表明:在相同转速时随着运行时间的增加曝气池溶解氧浓度随之增大,但增幅逐渐降低;随着转速的增加,叶轮对水的做功能力增强,提高了水面的湍动强度及水面下的复氧强度,进而缩短了曝气池达到氧饱和的时间,转速为300 r/min达到氧饱和的时间比150 r/min缩短了约57%。转速、浸没深度和液位高度的改变均会极大地影响倒伞曝气机的性能:转速的增加能够提升倒伞曝气机的标准氧总转移系数和标准充氧能力,但对于标准动力效率的提升有一个上限值,该上限值与浸没深度有关;倒伞曝气机低速运行时,浸没深度和液位高度对标准氧总转移系数和标准充氧能力的影响较小。液位高度的增加会加大倒伞曝气机的标准充氧能力和标准动力效率,但是相同液位高度下,随着转速的增加标准动力效率增幅明显小于标准充氧能力增幅,当液位高度为250 mm时,转速从150增加到300 r/min,标准充氧能力值提高2.91倍而标准动力效率提高1.22倍。该研究可为倒伞曝气机的经济运行提供参考。

Experiment on influence of operating parameters on aeration performance in inverse umbrella aerator

Abstract: The inverse umbrella aerator is widely used in the waste water treatment process because of its simple structure, large action area, high energy use efficiency and so on. Depending on the rotating speed, immersion depth and liquid level of the inverted aeration aerator have a great influence on the aeration performance. In order to study the influence of parameters on the synergistic effect of inverted aeration machine aeration performance changes, in this study, an aeration performance rig was established for investigating the influence of the rotating speed, immersion depth, and liquid level to the aeration performance of the inverse umbrella aerator. To study the effect of rotating speed, the experiment was carried out under the condition with the constant liquid level and the same level between the impeller and the liquid surface. The standard oxygen mass transfer coefficient, the standard oxygen transfer rate and the standard aeration efficiency were analyzed at the rotating speeds of 150, 180, 210, 240, 270 and 300 r/min. To study the effect of immersion depth, we kept the other two variables unchanged, and analyzed the standard oxygen transfer rate and the standard aeration efficiency at the immersion depth of 5, 0, and -5 mm. To study the effect of liquid level, we kept the other two variables unchanged, and analyzed the standard oxygen transfer rate and the standard aeration efficiency at the liquid level of 200, 250 and 300 mm. An intermittent unsteady state method was used to measure the change of dissolved oxygen concentration with time. At the beginning of each test run, the sodium sulfite was added as a deoxidizer to the tap water and the cobalt chloride was added as a catalyzer to the tap water. The inverse umbrella aerator was rotating in a lower speed until the dissolved oxygen reached into zero level and the inverse umbrella aerator was kept in a constant speed until the dissolved oxygen reached the oxygen saturation. The concentration of dissolved oxygen in the test section was measured by using a dissolved oxygen meter. The speed and the power were obtained by a torque meter. The least square regression analysis was used to deal with the aeration data in order to get the oxygen mass transfer coefficient. The oxygen mass transfer coefficient combined with the empirical coefficient can be transferred into the standard oxygen mass transfer coefficient. Through comparing the experimental data, the results showed that the standard oxygen mass transfer coefficient and the standard oxygen transfer rate were proportional to the speed. But the standard aeration efficiency had no clear relation with the speed. The dissolved oxygen concentration increased with the increase of operation time at the same speed while the increasing amplitude had the opposite trend. With the increase of the speed, the capacity of the impeller to the water was enhanced and the turbulence intensity on the surface and the re-oxygenation intensity in the bottom were increased, which resulted in the short time to reach the oxygen saturation, comparing with 150 r/min. The time needed to reach the oxygen saturation of 300 r/min was reduced by about 57%. The change in rotating speed, immersion depth and level height greatly affected the performance of the inverted aeration aerator. The increase in speed can increase the standard oxygen total transfer coefficient and standard oxygenation capacity of the inverted umbrella aerator. But the standard power efficiency of the upgrade had a ceiling, and the upper limit depended on the immersion depth. The immersion depth and liquid level had little effect on the total oxygen transfer coefficient and standard oxygenation capacity when inverted umbrella aeration machine at a low speed. Increasing the height of the liquid level increased the standard oxygenation capacity and standard power efficiency of the inverted umbrella aerator. Therefore, the study provides a certain reference for the economical operation of the inverse umbrella aerator.