The Effects Of Oxygen Concentration Distribution On The Flame Structure In One-dimensional Counterflow Flames

Results from computations of diffusion flames, lean premixed flames, partiallypremixed methane/air counterflow flames and oxygen diluted partially premixed/oxygenenriched supplemental combustion flames are reported. The OPPDIF code in theCHEMKIN was used. The effects of one-dimensional oxygen concentration distribution onflame structure, species reaction rate, and pollutant emissions were analysised.By comparison, the high temperature zone is narrow for the diffusion flames with thehigh pollutant emissions. There are some advantages of reacting readily and uniformtemperature, but disadvantages of unsteady flame, flame backfire and blowout for leanpremixed flames. Compared with the diffusion flames, the pollutant emissions is lower andcompared with lean premixed methane/air flames, NOx emissions is lower for partiallypremixed methane/air counterflow flames, with changing the equivalence ratio of thepartily premixed flow.Also, it is not only of strong flame stability and combustion intensitybut also in the position to prevent flame oscillation. Based on partially premixedmethane/air counterflow flames, oxygen diluted partially premixed/oxygen enrichedsupplemental combustion flames help lower them further when these pollutant emissionswere low, with changing oxygen concentration distribution and there are severaladvantages of the strong flame stability and the high combustion efficiency too.Detailed studies of the effects of oxygen concentration distribution on oxygen dilutedpartially premixed/oxygen enriched supplemental combustion flames reveals followingconclusions including:(1) lower pollutant emissions, uniform temperature and much widerdouble-flames regime with decreasing the equivalence ratio of the partily premixed flow inthe fuel-rich mixture,(2) significantly more NOx emission with regard to decreasingoxygen enriched concentration supplemental combustion in the oxidants, and (3) noticeablereduction in CO emissions, NOx emissions and C2H2concentration as oxygen dilutedconcentration in the fuel-rich mixture reduced.The optimum conditions based on this paper are18%-19%in the oxygen dilutedconcentration partially premixed in the fuel-rich mixture,22%in oxygen enrichedconcentration supplemental combustion in the oxidants,1.2≤ΦP≤1.4given for theequivalence ratio of the partily premixed flow in the fuel-rich mixture. NOx emission index is reduced by7.5%-59.4%and CO emission index is reduced by22.5%-62.5%bycomparison to partially premixed methane/air counterflow flames, when the equivalenceratio of the premixed flow is the same.