| Fine particles are very common in the industry,which is the main cause of haze weather.Traditional dust removal equipment has poor capture efficiency for fine particles,adding a particle pretreatment device(turbulent agglomerator)in front of it becomes an effective way to improve the particle separation efficiency.However,the research on turbulent agglomeration is not enough at present,which limits the development and improvement of turbulent agglomerator.Therefore,this paper will investigate the agglomeration characteristics of fine particles in turbulent field,and the main work is as follows:Firstly,the computational fluid dynamics(CFD)coupled the discrete element method(DEM)numerical model is established,the large eddy numerical simulation model and the modified particle contact model with liquid bridge force are selected.The simulation of agglomeration characteristics of fine particles in turbulent field is realized.Secondly,the CFD+DEM coupling model is used in the third chapter to study the influence of vortex generator structures on particle agglomeration,the following factors are considered:the geometric size of the vortex generator,the transverse pitch,the longitudinal pitch,the row number,the arrangement and the form of the vortex generator.The results show that the structure of the vortex generator has an important effect on the agglomeration efficiency of particles.At the same time,the dimensionless parameter K is defined to judge the agglomeration efficiency,the rule of turbulence characteristic parameters and agglomeration efficiency is found out.Thirdly,coupling the relationship between turbulence characteristic parameters and agglomeration efficiency,the turbulence agglomeration kernel function is modified and the correction coefficient α(agglomeration efficiency)is added.The results show that the simulated results with the modified kernel function are much closer to the actual situation.Finally,the influence of the structure of turbulent agglomeration on particle agglomeration efficiency is studied by using Euler multiphase flow model coupled with Population Balance model(PBM)and embedding the modified agglomeration kernel function through the UDF function of Fluent software.The results show that the sawtooth turbulent agglomeration has the best agglomeration efficiency.The ratio of the length of vortex generator horizontal to the direction of incoming flow to that vertical to the direction of incoming flow is recorded as a/b,small a/b ratio has better agglomeration efficiency.The transverse pitch and the longitudinal pitch of the turbulence agglomeration should be moderate,too large or too small will weaken the agglomeration efficiency of particles.There is little difference in the agglomeration effect between aligned arrangement and staggered arrangement.Agglomeration efficiency increases with the increase of row number and then remains stable,but the row number is not easy to be too large,which will lead to greater flow resistance.At the same time,regardless of the type of turbulent agglomerator,when the agglomeration efficiency is the best,the corresponding transverse pitch and longitudinal pitch are the same. |
