Performances Of Flow And Mixing Characteristics In Static Mixer With New Structure

Although static mixing technology widely used in process industries has matured,but in many applications,there are still plenty of problems,which in the limited mixing distance,the maximum realization of the material quickly,perfect mix,is still a difficult problem to solve.Based on the technology of selective catalytic reduction as an example,a new type of geometrical structure was proposed.The static mixer characteristics were studied from the aspects of flow field characteristics,mixing performance and resistance loss.Firstly,based on the numerical calculation method,the comparison experiment on mixing efficiency of different mixing element structures was carried out,and the downstream distribution field of the velocity field and the concentration field were taken as the research object,showing that after the mixing of the components,two pairs of oppositely longitudinal vortices appeard in the downstream,and the mixing effect factor increased sharply.Furthermore,the mixed efficiency of the rounded rectangular mixing element was the best by comprehensive comparison of concentration uniformity,velocity uniformity,resistance loss and other quantitative analysis indicators.The second part focused on the flow field characteristics of the new mixer by using the hot wire velocity measurement technique.It was found that the coverage and angle of the mixing element were the factors that significantly influenced the flow field.The velocity field was newly distributed,the turbulence kinetic energy and the turbulence intensity increased rapidly,and there was a peak positively correlated with coverage and angle in the area of influence.Further study found that the mixing element had a significant effect on the flow field with a region width of less than 1 times the equivalent diameter.Finally,to observe the mixing performance of the static mixer,virtually mixing experiment via numerical simulations were conducted for the mixing section.From the effects of jet tube and mixing elements on the uniform distribution of tracer CO concentration,it was inferred that increasing the velocity and concentration of the jet phase was not an effective measure for improving the mixing effect,in the jet tube part,when the injection phase velocity increased 4 times,thereby improved the comprehensive efficiency but also was less than 5%,and the change of the injection phase concentration had no significant effect on the concentration field and velocity field.At the same time,in the mixing elements part,its coverage rate,line spacing and tail distance were the significant influencing factors of mixing performance.The coverage rate,line spacing and tail distance were increased,and the mixing efficiency increased first and then decreased.When the coverage rate was 0.175 the combined mixing efficiency was the highest,and when the line spacing and the tail distance were 0.125 times and 0.25 times the inlet equivalent diameter,the maximum mixing of the components could be achieved.