Jet Characteristics And Experimental Research Of Submersible Mixer

Submersible mixers, a new type of efficient stirring machinery, are widely used in the sewage treatment for industry and agriculture. Highly valued by the government to the sewage treatment technology, the application industries of submersible mixers gain unprecedented development. To explore the design theory of submersible mixers, flow mechanism and flow law inner the stirring fluid, this article launches a systematic study for the submersible mixers based on theoretical analysis, physical experiment and numerical simulation. The main research contents and innovations of this article are as follows.1. Computational formulas of hydraulic thrust, torque and power of the submersible mixers are derived for the first time to come to the conclusion that stirring power is proportional to the third power of rotate speed, to stirring fluid density, and hydraulic thrust is proportional to stirring fluid density. The estimation formula of the submersible mixers’ efficiency is decuced from a theoretical perspective for the first time to draw a conclusion that the efficiency of submersible mixers is proportional to the3/2power of hydraulic thrust, is inversely proportional to the impeller diameter and is inversely proportional to the impeller rotate speed. Thus it has offered a theoretical basis for the design of submersible mixers’blades.2. The grid irrelevance is discussed, and three treating methods-grid assumption, VOF model, Wall face to the free surface of the pool are analyzed. Compared the calculation value with experiment value, combined with the physical conditon, grid assumption is finally adopted to deal with the free surface of the pool. This simulation is quite reasonable.3. According to different shape pools, optimum installation method of single or multiple mixers is firstly put forward to obtain satisfactory stirring effect, which has significant practical value for engineering application.4. The four different models of submersible mixers are combined to calculate by numerical simulation. The following conclusions are presented for the first time that the flow state of stirring fluid belongs to submerged non-free turbulent round section swirl jet, and is inter-affected by radial Wall jet and impact jet flow; there exsit entrainment phenomenon, Wall attachment phenomenon and vortex phenomenon; the axial advance distance of submersible is x, effective stirring radius is R, and meanwhile the matching pool critical dimension is proposed. The four different models of submersible mixers are numerically simulated and present the expression maximum axial velocity declines by the hyperbolic form.5. The emphasis is put on detailed numerical simulation analysis to the fluid in the4000mm×1000mm×1500mm pool stirred by the WJ0.75-4-210submersible mixer. The Wall attachment effect and vortex phenomenon inner the pool are observed. The pool is stationary calculated, while the axial velocity, radial velocity, and circumference velocity of the fluid inner the pool are analyzed respectively. Meanwhile, pressure field and velocity field on the impeller, the circulation in the impeller exit, axial velocity, radial velocity, and circumference velocity are studied respectively and the following conclusions are drawn:the fluid inner the pool is high reynolds number and presents turbulance intensity; the fluid inner the pool forms jet flow along the impeller, and the fluid thrusts axially, diffuses radially; the flow velocity near the impeller is relatively higher, while the velocity in the other parts is lower; flow surface and the flow velocity field in the bottom of pool is distributed double parabolically, while the flow velocity near the installation sections of the mixers in the center of the pool is distributed parabolically; the attachment effect of fluid field inner the pool is obvious, and there form large-scaled vortex and A vortex, with many small-sized vortexes, which flow complicatedly. These conclusions can be mutually authenticated with the theoretical analysis. At the same time, the fluid inner the4000mm×1000mm×1500mm pool stirred by the WJ0.75-4-210submersible mixer is given unsteady calculation to observe the amplitude domain, time domain and frequency domain of the pressure fluctuation on the inlet of impeller, inside the impeller and outlet of impeller. Thus, the mixing flow rules by WJ0.75-4-210submersible mixer are revealed to lay a solid foundation for the further research of the key technology to design and manufacture the submersible mixers.6. Two methods are adopted to test the stirring flow field of the submersible mixer for the first time. One is to use current meter to test the whole flow field; the other is to use PIV to test the partial flow field. The test results fully prove the characteristic of the fluid of submersible mixer and the reliability of law of the stirring flow field which are concluded in the previous chapters.