Flow Field Analysis And Operation Optimization Of Submersible Mixer

With the social and economic development, the level of urbanization has been increasing; the consumption of water has increased. Now water pollution is becoming more and more serious. The sewage treatment has become an important topic for the time being. As an important part of sewage treatment, the submersible mixer is widely used in industrial and domestic sewage treatment. As one of the key equipment in water treatment technology, the effect of its mixing and pushing flow has important influence on the quality of sewage treatment, energy saving and consumption reduction. Therefore, studying the mixing flow field and its operation optimization has both theoretical and practical significance.The software Turbogrid, Pro-E, ICEM were used to make 3D model and mesh the axial flow pump impeller, Beite impeller, a tank, a simplified motor shell model. Based on the standard k-ε turbulent model, the numerical simulation was carried out on different working conditions, namely, different motor speed, different blade tip clearance, different blade angle, different installation angles, with or without diversion shell. The characteristics of the external flow field and internal flow field of submersible mixer were analyzed; the external characteristics of submersible mixer under different conditions were compared; a comprehensive evaluation was made on the effect of submersible mixer under different conditions; finally the optimal operating parameters were obtained. In the paper, the axial flow pump impeller and Beite impeller blade were compared in order to assess their advantages and disadvantages. According to the Newton’s third law of force and counterforce, a set of experimental apparatus was designed, which can measure the submersible mixer axial thrust and torque and submersible mixer motor power, and a comparison was made with experimental results and numerical simulation results. Meanwhile, the flow field in the tank was measured by propeller instrument, and the measured results and numerical simulation results were comparatively analyzed.With the increase of the blade angle, the axial power and axial thrust increased gradually. When the blade was placed at the angle of +4 degrees, it basically met the requirements of the mixing. With the increase of the speed of the motor, the shaft power and thrust increased continuously, the effective mixing ratio was increasing, and the energy consumption was reduced as much as possible in order to meet the basic requirements, as a result,576r/min was selected as the best optimal speed. The installation angle had no effect on the flow and shaft power. With the increase of the installation angle, mixing area increased and the dead zone decreased. When the value of installation angle was to 45 degrees, the mixing area reached the maximum value; and then with the increasing of the installation angle, the mixing area gradually decreased, but were higher than that at the installation 0 angle. With the increase of the blade gap, near the catheter the disturbance became strong, and jet flow diffusion angle had a tendency to spread; outlet flow had nothing to do with the size of blade clearance; therefore, and the 6mm was selected ultimately as the optimal blade clearance. Due to the blade force enlarging, motor power of submersible mixer with the catheter was smaller than that without the catheter and can also save energy, but jet disturbance radius of submersible mixer without catheter is larger and Stirring effect of submersible mixer without catheter is better. Axial flow pump impeller had a long advancing distance and can effectively reduce the wall effect, while Beite impeller had a better mixing effect. The precise control and measurement of the motor speed was realized by the combination of Holzer sensor and transducer. The thrust and torque measuring device had the advantages of high precision, and the deviation of torque and thrust between the numerical simulation values and laboratory is very small. The velocity of fluid measured by the propeller meter had the same trend with the numerical simulation values, which validated the accuracy of the of numerical simulation.