Flame Shape And Flow Field Research Of Lean Premixed Combustion

As the improvement of green environmental protection consciousness,high efficiency and low pollution clean combustion technology hasdrawn great attention of the academic circles.Because lean premixed combustion technology has the advantages of low pollution,high efficiency,it has become the focus of research.However,due to the operating conditions are far below the normal chemical equivalent ratio,combustion instability phenomenon such as blow out and thermal-acousticinstabilities are easily to happen.At the same time,in the combustion process flame shape transformation especially flame flashback to the corner part is always take place,it serious influence the normal work of combustion chamber,has seriously restricted the development of premixed combustion technology.This paper takes the lean premixed combustion process as the investigative object,flame shape transformation havebeen studied,the influence ofoperation parameters and structure parameters on flame shape transformation and the cause of it have been analyzed.The main research work and conclusions in this paper are as follow:(1)Established the visualization experimental system of lean premixed combustion,records the flameand its changes by high-speed photography,analysis the structure of the cold and hot state flow field using PIV system,the experiment platform is the foundation of carrying out experimental research work.(2)On the experimental platform,the effect of different equivalent ratio on flame structure was studied.The study found that as the equivalent ratio reduce from 0.7 to 0.2,the flame undergo a process ofcompacted flame,M-shape flame,the column shape flame,the flame suspended in the combustion chamber,and the blow-out.(3)The experiment found that the structure of the combustion chamber and the location of the cyclone could greatly affect the flame shape transformation: in the combustion chamber diameter of 60 mm didn’t exist a V-shaped flame;in the combustion chamber diameter of 80 mm,flame existed several structure transformation;in the combustion chamber diameter of 100 mm,V-M shape transformation happened when the location of the cyclone was more than 60 mm.(4)Measured the cold flow field under the different cyclone position and in the different diameter combustion chamber,analyzed the influence of the combustor structure on flow field,the study found that the exist of the shear layer and the corner recirculation zone mainly affected by the angle between the shear layer and the backward step.(5)Measured and analyzed the flow field under different flame shape structure,the result showed that: in the V-shaped flame flow field,there was no vortex in thecorner recirculation zone,in critical transition flame and M-shaped flame,there were obvious vortex structures;the instantaneous flow field under the V-shaped flame,critical transition flame and M-shaped flame were analyzed,found that there were less vortex in the corner recirculation zone under V-shaped flame;the vortex frequency in the corner recirculation zone was analyzed to get the relationship of thefrequency and flame shape transformation.