Research On Optimization Design Theory Of Airfoil Based On CFD And Its Application In Aerator

Oxidation ditch is the most common form of treatment process in activated sewage sludge treatment,and the most critical mechanical equipment in the oxidation ditch treatment process is the surface aerator.It can determine the efficiency of the oxidation ditch process to treat sewage.Surface aerators are widely used in the sewage treatment industry because of their advantages of simple structure,easy disassembly and replacement of worn parts,convenient maintenance and low cost.After a lot of investigation,it is found that the surface aerators used in the oxidation ditch treatment sewage process in China are mostly inverted umbrella type surface aerators.The impeller of the inverted umbrella type surface aerator is arranged with a large angle taper and a wide blade straight radiation.The profile of the blade is rectangular.The aeration equipment has the characteristics of low power efficiency,high energy consumption and uneven fluid flow rate.Based on the research results of the research group,through the analysis of the geometric parameters and aerodynamic performance of the NACA series airfoil,the paper innovatively proposes the application of the non-equivariant angle logarithmic spiral curve as the generatrix and NACA0012 airfoil as the profile Airfoil aerator blades.In this paper,the theoretical analysis,numerical simulation and reduction model test are used to analyze the operation mechanism and aeration performance of the airfoil blade.The CFD numerical simulation technology was used to analyze the flow field of a non-equivariant angle logarithmic spiral airfoil blade aerator.The process of forming a water jet at the liquid surface is verified,and the negative pressure zone is formed on the back of the blade to entrain and lift the fluid and the circular flow formed in the fluid.The flow velocity of the fluid in the oxidation tank gradually decreases as the distance from the liquid surface increases,and the fluid below the liquid surface continuously updates the liquid at the blade under the action of the circulation and lifting force formed by the blade push flow.Improve the aeration effect.The fluid velocity is the lowest at the bottom of the pond and the junction between the bottom and the wall surface directly under the blades,and it is easy to form sludge deposits and affect the aeration effect.Using 3D printing fused deposition rapid prototyping technology,the blades of two blades with non-equivariant angle logarithmic spiral curve airfoil aerators were printed.The scale model test rig was made using the Froude’s similarity criterion,and the performance data of the airfoil aerator blade was measured using a flow meter and a dissolved oxygen meterThrough the analysis of the data,the standard oxygenation capacity and total oxygen transfer coefficient of the non-equivariant angle logarithmic spiral curve airfoil blade surface aerators increased significantly with the increase of the number of blades.At the same speed and the same immersion depth,the number of blades of the aerofoil aerator has less effect on the standard power efficiency of the aerofoil aerator,but when the speed is lower than 140 r / min,the aerofoil with a small number of blades should be used Gas machine.