| The wastewater-treatment is an important measure of the environmental protection section and enterprise to solve the water pollution nowadays. And the urban wastewater-treatment infrastructure has become a indispensable part in modern urban economic development and protection of water resources. The wastewater-treatment mixer is a kind of new efficient diving mix device, which is applicable for the treatment of aeration tank and anaerobic tank in the industry, city and village wastewater-treatment plant. Impeller is the mainly transduction device in the mixing process, which transformed the mechanical energy into kinetic energy of fluid. The impeller structure and running situation are the important factors that decided the flow field distribution and energy conversion efficiency. So it is necessary to use modern design method to research and develop a kind of wastewater-treatment mixer that has high efficiency, and study flow field of wastewater-treatment pond.The theory of design impeller of wastewater-treatment mixer is not developed well up to now. We can use impeller design methods of axial flow pump and marine propeller to design impeller of wastewater-treatment mixer.The main research contents and important conclusions of this paper are below:(1) The three design theories of aerofoil blade were summarized, and their characteristics were analyzed. Based on those design theories, we designed a wastewater-treatment mixer blade.(2) The internal flow of wastewater-treatment pond was simulated by using CFD software FLUENT and multi-reference frame was used in the simulation. The macroscopic law of the flow field and the characteristic of velocity were analyzed. We can draw conclusions: the wastewater-treatment mixer mostly produces axial flow.(3) By changing some design and installation parameters of wastewater-treatment mixer, we can compare and analyze the numerical simulation results and find that: (a)When the wastewater-treatment mixer was deviate from the narrow side with 15°, the service area of wastewater-treatment mixer was max, and mixing requirement of flow in the pond can be realized; (b) Analyzing the wastewater-treatment mixer, the calculation formula of hydraulic thrust and power were deduced and demonstrated, which is significant in theory and valuable in practice, and the relation between thrust and density of a working fluid was put forward. This can be proved by FLUENT6.3 simulation. (c) Compared to flow filed in different wastewater-treatment ponds which mixed by with or without dome wastewater-treatment mixers, we got the function of the dome. The dome can guide flow in axial direction, and it can reduce the pond-wall-boundaries effection to fluid. These studies for optimization design of the wastewater-treatment mixer provide theoretical and project guidance.(4) Wastewater-treatment mixer with dome was studied experimentally, and a platform for the experiment was built. The thrust of the wastewater-treatment mixer and the velocity of points in the wastewater-treatment pond were measured, and at the same time, the flow field were drawn, analyzed and compared to numerical simulation.
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