Effect Of H₂/CO Doping On Soot Formation In Ethylene Diffusion Flame In CO₂ Oxygen Enriched Atmosphere

Soot is the product of undercombustion of hydrocarbon fuel,which not only causes huge energy loss,but also causes serious damage to human health,ecological environment and industrial equipment.In addition,global warming and frequent haze events in China are closely related to soot particles.At present,the requirements of environmental protection policies are gradually tightening,and it is imperative to reduce soot emission.Therefore,the research on soot generation characteristics and influencing factors is indispensable in order to find ways to solve environmental pollution and improve energy efficiency.For research on soot generation,stable and reliable diagnostic technology is essential.Based on a comprehensive comparison of relevant diagnostic methods at home and abroad,this paper selects the extinction method as the experimental detection method and independently builds an experimental platform for the extinction method;the extinction method has the advantages of accurate measurement,easy construction,simple operation and relatively low equipment cost.In addition,on the basis of experiments,this paper uses the CoFlame program to carry out numerical simulation research on related experiments,in order to have a deeper understanding of soot generation changes at the mechanism level.This article first conducts pre-experiments on the numerical model and experimental platform used,and compares the results with the literature.It is found that the overall data trend is similar to the results in the literature,with only slight differences in numerical values,which verifies the reliability of the numerical model and the experimental platform;Later,by changing the proportion of flame additives,the effect of blending H₂/CO on the soot generation in ethylene flame under CO₂oxygen-rich atmosphere was studied.The results show that under the CO₂oxygen-enriched atmosphere,with the increase of the H₂/CO addition ratio,the suppression effect of the soot generation of the ethylene flame in the simulation and experimental results becomes stronger;taking the simulation results as an example,when the H₂/CO ratio is 0.1/0.1,0.1/0.3,0.2/0.2,0.3/0.1,0.3/0.3,the volume fraction of soot decreased by 9.6%,13.9%,18.1%,21.4%,25.3%,respectively;when the total amount of H₂/CO added is the same,the greater the H₂ratio,the more the soot volume fraction decreases;The H₂/CO ratio increases,the flame brightness becomes darker,and the height change is small;the maximum experimental flame height difference is 0.17 cm,and the maximum simulated height difference is 0.2 cm;the flame temperature rises slightly,and the change is small,basically within 1%,which shows from the side that temperature changes are not the main reason for the suppression of soot generation;Analysis of the related process and components of the simulation found that the addition of H₂/CO mainly reduced the concentration of C₃H₃,C₂H₂,and C₆H₆,increased the concentration of H₂,so as to reduce the formation of polycyclic aromatic hydrocarbons;reduces the concentration of pyrene,slows down the soot nucleation process,and inhibits the surface growth process,and finally achieves the purpose of inhibiting soot generation;changes in oxidation rate and H⁺concentration are not the main reasons for the suppression of soot generation.