Study On Mixing Performance Enhanced By Single-wire Flexible Impeller

Stirred reactor has been widely used in chemical industry,non-ferrous metallurgy,sewage treatment and other fields of industrial production.As one of the key parts of stirred reactor,the impeller affects fluid mixing performance,economic efficiency and safety of industrial production.Therefore,it is of great significance to enhance mixing performance,and guide the development and utilization of efficient energy-saving stirred reactor by designing and optimizing impeller structure.In this thesis,single-wire flexible impeller was proposed.The mixing performance and chaotic characteristics were evaluation indicators.The effects of impeller type,the distance between impeller and bottom,the length of flexible wire and the diameter of flexible wire on the fluid mixing behavior were analyzed.The internal structure of flow field in the stirred tank was investigated by CFD numerical simulation.Single-wire flexible impeller and solid particles synergistically enhanced fluid mixing behavior.The effects of impeller type,solid concentration,the diameter of solid particles and the flexible material on mixing time and chaotic characteristics were analyzed.The main conclusions are as follows:?1?Both traditional rigid impeller and single-wire flexible impeller had symmetrical flow field structure.Compared with traditional impeller,mixing area was larger,isolation area was smaller,and the direction of fluid movement was more confusing with single-wire flexible impeller.It was consistent with experimental results.?2?Single-wire flexible impeller can effectively reduce energy loss,shorten mixing time,enhance mixing efficiency and chaotic characteristics by regulating and controlling the flow field structure and the way of energy dissipation.At rotation speed120 r·min^-1,compared with traditional rigid impeller,C_e was decreased by 87.4%and LE_maxax was increased by 53.2%with single-wire flexible impeller,C_e was decreased by43.8%and LE_maxax was increased by 10.8%,compared with single-wire rigid impeller.?3?The effect of structural parameters on fluid mixing behavior was studied,and the optimal parameters were determined:the diameter of flexible wire was at 0.8 mm,and the distance between impeller and bottom was at 0.25 T.In addition,the effect of the length of flexible wire on the fluid mixing behavior was the greatest,followed by the diameter of the flexible wire,the distance between impeller and bottom was the least.?4?Fluid mixing performance was almost unchanged after adding solid particles in the system of rigid impeller.when operated using solid particles synergistically with single-wire flexible impeller,isolation area disappeared quickly and chaotic mixing performance of fluid was effectively enhanced.At 4500 W·m^-3,at solid concentration 0,1%,2%,3%,4%,mixing time was respectively shortened by 65.4%,67.0%,68.9%,71.1%,and LE_max was respectively increased by 25.3%,31.6%,32.3%,34.2%,35.4%,compared with traditional rigid impeller.?5?Increasing solid concentration led to destroying the stability of isolation area more easily,shortening mixing time and increasing the degree of chaos.Increasing the diameter of solid particles,the energy loss increased,the liquid phase velocity decreased,the mixing time increased and the degree of chaos decreased.Compared with the 201and 304,the flexible vibration of NiTi alloy was stronger,which was more conducive to fully exerting the rigid-flexible-flow coupling effect and the synergistic strengthening effect of single-wire flexible impeller and solid particles,shortening mixing time and increasing the chaotic characteristics.In conclusion,single-wire flexible impeller can effectively enhance fluid mixing behavior,improve mixing efficiency and enhance chaotic characteristics.