| Soot is a kind of particles produced during combustion of fossil fuel, and sootparticles are formed due to incomplete combustion, which can lead to dramaticallydecrease in fuel efficiency. In addition, soot will damage the environment and harm thehealth of human beings, which can result in respiratory disease. In recent years, in order tocope with the global warming problem, oxy-fuel combustion technology, which replacesair by O2/CO2flow as the oxidizer combined with flue gas recirculation, has receivedmuch attention due to the advantages in CO2recycling. Thus, a deeper understanding onphysical and chemical processes of soot formation, especially in CO2atmosphere ofoxy-fuel combustion, has practical significance on the development of clean combustiondevices and decreasement of pollutant emmision.Firstly, based on JSR/PFR system, soot formation in post-flame regions forethylene-enriched premixed flame is studied numerically, and the main formation paths oftypical PAHs are investigated by reaction path analysis and sensitivity analysis. Besides,the combustion characteristics in N2and CO2atmospheres are compared, and the effectsof CO2on soot formation are investigated. The results showed that in the formationprocess of A1, C2H2and C3H3are important intermediates. The growth process of PAHs isbased on H-Abstraction-C2H2-Addition (HACA) mechanism and PAH+PAH radicalrecombination and addition reactions. In addition, the chemical effect of CO2hasinhibitory effects on soot formation.Then, impacts of flame structure and combustion characteristics on soot formation in1-D opposed-flow diffusion flames was investigated with different stoichiometric mixturefractions (Zst), and the difference between CO2and N2atmospheres are compared. Theresults showed that in both atmospheres, with the increase of oxygen-enrichment andfuel-dilution, the amount of soot in the flame decreased. In addition, the thermal and chemical effects of CO2have inhibitory effects on soot formation, and the thermal effecthas a greater impact.In the end, the effects of incensement of oxygen concentration on combustioncharacteristics and soot formation in2-D coflow diffusion flames are studied. At the sametime, the simulation results are compared with experimental results. The results showedthat with the increscent of oxygen concentration in oxidizer, the height of flame decreasegradually, and the temperature peak increases, and high temperature regions shift from thetwo sides to the top and sides of flame. In addition, the peak of soot volume fraction doesnot decrease monotonously, but increases at first, and then decreases. |
PDF Full Text Request