Abstract:In order to rationally develop and utilize brackish water resources, the structure and operating parameters of a continuous first-but-mix stirring reactor at the front end of an agricultural irrigation system were optimized. The effects of mixing speed and paddle width on the mixing performance were investigated by using a double-layer paddle mixer with a diameter of 290mm. Realizable k-ε model and Eulerian multiphase flow model were used for numerical simulations and validated by experimental data. The analysis of turbulent kinetic energy, velocity flow field, brackish water volume fraction distribution, mixing time and power consumption of the agitator showed that the increase in mixing speed and paddle enhanced the turbulence and flow velocity for both the threebladed open type and the combined anchor type. It was found that the rotational speed had a greater effect on the studied parameters than the paddle width. Overall, the effect of rotational speed on the studied parameter was significantly more than paddle width, in addition to the significant difference in the effect of these two factors on the two types of agitators. Compared with the three-bladed open agitator, the combined anchor agitator reduced the agitation time by 6.8%, but increased the agitation power consumption by about 10%. Taking into account of crop irrigation requirements, mixing efficiency and equipment energy consumption, it was recommended to use a three-blade open agitator with a lower speed (90r/min) and a wide paddle (50mm). This configuration can effectively balance the mixing efficiency and energy consumption of a continuous salt and freshwater mixing and stirring system. The results can provide a reference for the design optimization of continuous brackish freshwater mixing and stirring reactors.
