Research On The Flow Field Characteristics And Flocculation Efficiencies Of The Innovative Hydraulic Impeller Flocculator

Hydraulic condition plays significant role in flocculation process.Different types of hydraulic conditions in various types of flocculation equipment,devices,and flocculation pool determines the flocculating effect and efficiency.Because of the complexity of the flow regime in the process of flocculation,especially the turbulent motion in flocculation,researches on flocculation kinetics has certain limitation.Therefore,there are lack of science,system and reasonable explanation for the real cause of flocculation kinetics.In addition,the flocculation process commonly used in water treatment works still exist shortcomings in operation efficiency.Therefore,combining with the related new technology and new method of research,the development of new type of flocculation reaction device with low energy consumption,well flow control and operation efficiency were studied in this work.And the intrinsic relationships between flocculation kinetics and operation efficiency was consequently investigated.Through studies above,it can increase the efficiency of the flocculation process and improve the safety of drinking water security.Moreover,it has important theoretical and practical value.On the basis of flocculation kinetics principle,the development and design of a new type Hydraulic Impeller Flocculator(HI-F)was conducted in this work.And researches focusing on working principle and operation efficiency of HIB-F were conducted from two aspects including theory and experiment.Based on the combination of Particle Image Velocimetry flow field simulation analysis technology(Particle Image Velocimetry,PIV)and Computational Fluid Dynamics(Computational Fluid Dynamics,CFD),studies topics of this paper mainly contains following divisions including: hydraulics effect generated in the process of flocculation of HI-F,relationships between micro vortex and floc growth process,and quantity and scale of vortex.Based on these studies,response mechanism between operation efficiency and flow field characteristics of HI-F,and control method of hydraulic condition will be clearly interpreted.Research on operation condition optimization of HI-F shows that the optimum operation condition was confirmed as the following: the best operation condition for flocculation in the early stage using synthetic-rotating hydraulic propeller,the middle and later stage adopted the count-rotating hydraulic propeller.For low turbidity water,it should use the count-rotating hydraulic propeller,the reaction time can be controlled within 8 min.And the flocculant dosing of HI-F reduced 29.7% and 23.7%,respectively,in comparison with Reciprocating Clapboard Flocculation pool and Grid Flocculation(G-F).For low temperature and low water,flocculant dosing of HI-F reduced 25.4% in comparison with G-F.Moreover,the head loss of HI-F was only 42.1 ~ 51.2% of G-F in same conditions.In this study,during researches focusing on flow field characteristics,the combination forms of hydraulic impeller can be divided into four kinds of circumstances including single oar,axial,paddle radial adjacent to a higher rotating paddle,and radial adjacent to rotate paddle.Studies focusing on flow field characteristics,operation efficiencies and flocculation kinetics were evaluated under above four conditions.Results suggested that the axial hydraulic propeller can keep the continuous shaft in the vortex of sustainability.The radial direction adjacent rotating hydraulic propeller can increase the vortex shear force between.The adjacent to the radial rotating hydraulic blade can reduce the vortex shear force between the control mechanism of turbulent shear stress.Using PIV particles velocity measuring technology,the actual flow field characteristics and velocity distribution of HI-F was analyzed.Results interpreted the reasonable distribution of the number,size and strength of the micro vortex is the mechanisms of flocculation kinetics in HI-F.Results also illuminates that the HI-F hydraulic propeller can form much more vortex and interaction between vortexs were the mechanism of flocculation kinetics in HI-F.Velocity change law for reference in a specific area,the PIV measurement results and the numerical simulation of flow field in four kinds of turbulence model(Standard k-?,RNG k-?,Realizable k-? and LES)compares the simulation results of analysis,comprehensive analysis result shows that the RNG k-? turbulent model for flow field numerical simulation of the best model.In order to further enhance the accuracy of the results of numerical simulation and accuracy,using “non equilibrium function” and “PISO”pressure and velocity coupling algorithm" of RNG k-? turbulence model parameters are revised;Among them,the pressure,momentum,k and ?,etc of the relaxation factor correction respectively as follows: 0.3,0.6,0.6,0.6.Based on computational fluid dynamics software(Fluent12.0)computing tools,HI-Fdifferent hydraulic propeller combination of characteristics of flow field in a full range of simulation calculation,the velocity,pressure,v elocity gradient,turbulence kinetic energy and turbulent dissipation rate of change as the evaluation index,further clarify the HI-F is beneficial to increase the efficiency of the flocculation pool flocculation kinetics of cause.According to the charact eristics in different stages of the flocculation reaction,combination of optimizing the hydraulic propeller technology to determine the actual effect of flocculation,and compared with the more commonly used grid flocculation pool has carried on the comprehensive contrast.The results show that the HIB-head loss was reduced by 40% or more of the F process,stress,velocity gradient distribution is more advantageous to floc growth,avoid the floc breakage.