Numerical Simulation Of Gas-Liquid Two-Phase Flow Characteristics In Microporous Aeration

Due to its simple process, flexible control, high degree of purification, stable and reliable operation and good plug flow efect, oxidation dich is widely used in the field of wastewater treatment in China，and there are also problems such as complex hydraulic characteristics,uneven flow rate and sludge deposition. In this paper, the gas-liquid two-phase flow of micro hole explosive gas oxidation dich is simulated by using computational fluid dynamics software.The influence on the treatment eficicncy and operation eficiency of oxidation dich is studied by changing the structure parameters of oxidation dich, including:(1)Referring to the experimental aeration tank, a three-dimensional gas-liquid two-phase flow model of aeration tank was established, in which RNG k-ε model was used as turbulence model. Euler model and VOF model were used for numerical simulation. The results show that the simulation data of VOF model have a good ft with the experimental data, and the simulation results have a certain degree of cedibilit; The RNG k-ε Turbulence model and VOF model are combined to simulate gas-liquid two-phase flow.(2)A three dimensional gas-liquid two-phase flow model of microporous explosion oxidation dich was established to ensure the same acration rate. Different types of acration holes were aranged on the bottom of the oxidation dich. The simulation of the oxidation ditch was carried out, and the liquid-phase flow velocity, turbulence parameters, gas content and other aspects under diferent working conditions were compared and analyzed to select the appropriate arrangement of aeration holes. The results show that when the acration holes are evenly arranged on the bottom plate, the flow field is more stable, the overall velocity is larger,the velocity non-uniformity coffcient is smallr, the velocity is more uniform, and the mixing ffet of internal sewage is better; The turbulence cofficient is larger, the turbulence is more intense, and the active mixing degree of gas is greater. According to the stisis of the average gas content of different working conditions,it is also found that the gas content is higher when the bottom plate is evenly arranged with aeration holes.(3)Based on the selection of a reasonable bottom hole layout model,the effects of given different plug flow pressure differences on the flow field structure of the oxidation ditch,the plumb flow rate of the survey line and the gas volume fraction are studied.When the pressure difference is large,the flow velocity distribution is more uniform,the area of the return zone is small,and the average flow velocity is large,and the area of low velocity area is small,which is conducive to the improvement of sludge deposition at the bottom;the increase of internal gas content is conducive to the mixing of gas and liquid.If the pressure difference is too large,it will increase the energy consumption,so it is necessary to choose a reasonable pressure difference in actual conditions.