Numerical Simulation Study On Effect Of Oxidation Ditch Flowmaker Operating Parameters On Hydraulic Characteristics

With the progress of society,industrial and domestic wastewater are increasing,and improving urban wastewater treatment capacity has become a hot topic.The oxidation ditch process is one of the most widely used water treatment processes in China,which has the characteristics of less process,stable treatment effect,flexible form,more types,and can adapt to different environments.The simulation study of oxidation ditches can clarify the hydraulic characteristics of oxidation ditches and provide a reference for improving water treatment capacity and reducing energy consumption.In this paper,the RNG k-ε turbulence model,VOF method,and MRF model were selected by CFD technology to simulate the six-channel Carrousel oxidation ditch numerically.The effects of rotational speed and differential pressure on the hydraulic characteristics of the oxidation ditch were analyzed when the oxidation ditch aeration rotor was operated alone.The differential pressure thruster was used alone,and the effects of differential pressure on the hydraulic characteristics of the oxidation ditch were simulated when both were operated simultaneously.The main conclusions are as follows:(1)Model validation results show that the simulated value of the longitudinal velocity of the measurement line agrees well with the measured value.The section near the curve is affected by the upstream flow,which makes the speed of the internal test and the outer side of which is large.The vertical flow distribution of the section gradually becomes uniform.(2)When running the aeration turntable alone,the flow rate contained in the oxidation ditch is positively correlated with the rotational speed of the aeration turntable.Still,the aeration turntable at five rotational speeds pushes the flow less;the liquid flow rate is low and easy to produces siltation,which is not conducive to the operation of the oxidation ditch;the gas content rate in the oxidation ditch is positively correlated with the change in rotational speed,the gas content rate in the ditch increases with the height from the bottom of the ditch,and the growth rate of the gas content rate increases with the growth of height.(3)When runing a differential pressure pushing device alone,the oxidation ditch flow line shows the characteristics of smooth in the middle,poor at the bottom and top,and different flow line disorder areas at the top and bottom;when the pressure differential increases to 300 Pa,the flow line disorder situation in the oxidation ditch is improved,while the average speed in the ditch and the speed at the bottom of the ditch can meet the speed requirements for regular operation of the oxidation ditch,when the pressure differential increases again,the flow line will be further improved,but When the differential pressure rises again,the flow line will be further improved,but the change is small,and at the same time,a super high flow velocity area of more than 0.7m/s will be generated at the bottom,which leads to the increase of energy consumption;the gas content rate in the oxidation ditch is positively related to the height from the bottom of the ditch,and the gas content rate growth rate is basically the same under each working condition,and the gas content rate at the bottom of the ditch is lower than the gas content rate when only the aeration turntable is running.(4)When the aeration turntable speed is set at 2.5 rad/s and the differential pressure of the pusher is set differently,the flow field structure changes less than when only the pusher is set,and the flow line still shows the characteristics of smooth in the middle and chaotic in the top and bottom parts;the overall flow velocity in the oxidation ditch has a greater increase,and the average flow velocity at each level is greater than the sum of the average flow velocity at the surface when the aeration turntable and differential pressure pusher are run separately under the same parameters;The gas content rate increases with the increase of height under each working condition,but the growth rate of gas content rate is different than when running differential pressure pusher alone,and the growth rate of gas content rate is larger for the working condition with slight pressure difference;the gas content rate at the bottom of the oxidation ditch is greatly improved,which proves the feasibility of running aeration turntable and differential pressure pusher at the same time in the oxidation ditch,and provides some reference for parameter optimization and cost control in the actual project.