| Soot particles in the air can brings different degrees of harm on both human body and natural environment.Incomplete combustion is the major cause of the generation of soot.due to the complexity of formation and oxidation process,it still hasn’t been understood and cognized well,so it is necessary for us to study the principle of soot distribution for different time or space and make a measurement on soot concentration in the combustion process,understanding the characteristic of its formation,which has important significance for controlling the formation of soot.As a kind of non-intervention visulization technique,Laser Induced Incandescence can carry out measurements without intervention in flame combustion and shares the characteristics of fast response,high precision,getting both domestic and overseas attention in recent years.This paper adds a image doubler device,based on the traditional method of Laser Induced Incandescence,which can realize the measurements of soot concentration with method of two-dimensional Laser Induced Incandescence(2D-LII).This method use the signal itself for calibration and can be more convenient compared with traditional single point method.This paper first systematically introduce the basic principle of 2D-LII,then explain and analyze the selection of energy and wavelenth of laser,wavelenth of band pass filter,ICCD shooting parameters and some other key parameters of the control system.Second,introduce the 2D-LII measurement system in detail,which mainly consist of burner systems,laser device,ICCD and its control system,developing Matlab program algorithm to calculate soot volume fraction of flame and turn it into GUI interface in Matlab.Then use 2D-LII technique to make measurements on the soot concentration of standard ethylene flame in a gas burner,averaging the images taken at the two wavelenths and use Davis software to do the image correction proccesing,remove the signal noise through background images,calculate the distribution of soot volume fraction of the 2D-LII signal with program designed.Next,compare and analyze the measurement results of diferent methods at three flame heights.The conclution is,the soot volume fraction calculated by 2D-LII has a few discrepancies compared with extinction method and traditional LII method,but in the allowed error range,the results of 2D-LII measurement coincide with the experimental data in the past,which verifys the validity of this method,and lay a theoretical foundation for the next step.Next,use 2D-LII method to study and analyze soot formation characteristics of various blending ratio of biodiesel-diesel,biodiesel-diesel,propyl alcohol-diesel,amyl alcohol-diesel under same oxygen content.biodiesel-diesel,biodiesel-diesel,propyl alcohol-diesel,amyl alcohol-diesel under same blending ratio.The results show,Under the same flame height,As the biodiesel blending ratio increases gradually,the flame region of high concentration of distribution area gradually reduce.Soot distribution on the axis of the flame first increase gradually,reaching its peak at the middle of the flame,and then gradually oxidate,the soot concentration gradually decrease,the soot volume fraction presents a state of closure.With the increase of blending amount of biodiesel,the number of pixels with high fume content gradually decreased and the total amount of soot decreased.Compared with B0 flame,B20,B40 and B60 flame In the total amount of soot decreased by 37.5%,44.9%,61.8%.It is not a linear relationship to reduce the concentration of soot in the flame,but a process of decreasing the effect.At the same fuel flow rate,as the blending ratio of biodiesel increases,the caloric value of the fuel gradually decreases,the flame height decreases and the soot concentration of the flame decreases gradually and decreases compared with the same flame height condition The trend is more obvious.Under the condition of the same oxygen content,the distribution of soot volume fraction in the flame area is gradually changed from the low concentration interval to the high concentration interval because A17.2,P33 and B55 contain the aromatic hydrocarbon components gradually.A17.2,P33,B55 showed a trend of reducing the total amount of soot,compared with A17.2,P33 decreased 28.6%,B55 decreased by 59%.The maximum volume fraction of soot decreased,compared with A17.2,P33 decreased by 13.1%,B55 decreased by 41.4%. |
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