Effect Of Methane Blending On Soot Formation Characteristics In Premixed Ethylene Flame

In terms of mobile pollution sources in the cities,the emissions of particulate matter from the combustion of gasoline and diesel engines bear the brunt.The main component of the particulate emissions from the engine is soot.Soot has a significant impact and harm on climate change and human health.Therefore,reducing or eliminating engine soot formation and emissions and reducing PM2.5 emissions from the engine source are important aspects of solving the PM2.5 problem in the atmosphere.Currently,in the field of engines,soot generation and emissions are reduced mainly through in-cylinder combustion control(homogeneous compression ignition,fuel design,injection strategy,etc.)and exhaust gas aftertreatment technologies(DPF and GPF).The engine combustion soot model is the basis for predicting the combustion soot formation in the cylinder,which can provide important guidance for optimizing the cylinder combustion and reducing the engine soot generation.An important basis for the development of soot generation mechanisms / models is accurate and direct experimental measurements of characteristic parameters(soot particle size distribution,number density and volume fraction,etc.)of soot formation and growth.This not only verifies the accuracy of soot formation mechanism / model,but also provides guidance and reference for the development of soot generation mechanism / model.Gasoline and diesel are first cracked into small molecular hydrocarbons when they are burned,mainly composed of ethylene,propylene,methane,ethane and propane.Over the past decade,significant progress has been made in the study of the mechanism of soot formation for these small base hydrocarbon molecules.However,during the combustion of the practical fuel it is not a single small molecule that participates in the reaction,but rather a mixture of these since the practical fuel will pyrolysis first before oxidation.Therefore,it is very important to study the influence of the mixture of small molecular hydrocarbon fuels on soot formation.One of the most interesting features related to fuel mixture sooting propensity is the synergistic effect.Synergy means that,under the same conditions,a mixed fuel produces more PAH and soot than the single fuel.In this study,the methane blending effect on soot formation was investigated based on a premixed ethylene flame,whose equivalence ratio was 1.9 and calculated maximum flame temperature was 1727 K.Different ratios of methane was mixed into the ethylene flame,keeping the same equivalence ratio and maximum flame temperature.The particle size distribution function(PSDF)was measured in the burner stabilized stagnation(BSS)flame configuration,coupled with micro-orifice probe sampling technique and the scanning mobility particle sizer(SMPS).It was observed that with the increase of methane mixing ratio,the nucleation and growth rate of soot particles became smaller,and the total volume fraction of soot was also getting smaller.The calculated results of PAHs(pyrene)coincided with the experimental results.The results indicated that under the premixed flame conditions studied,there was no synergistic effect between ethylene and methane on soot formation characteristics.