Computed Extinction Limits and Flame Structures of H2/O2 Counterflow Diffusion Flames with CO2 Dilution

A narrowband radiation model is coupled to the OPPDIF program, which uses detailed chemical kinetics and thermal and transport properties to enable the study of 1-D counterflow hydrogen/oxygen diffusion flames with carbon dioxide as dilution gas over the entire range of flammable stretch rates. The effects of carbon dioxide dilution, ambient pressure and inlet temperature of opposed jets on the flame structures and extinction limits are compared and discussed. Both high-stretch blowoff and the low-stretch quenching limits are computed. When the CO₂ percentage is higher, the flame is thinner and flame temperature is lower. The combustible range of stretch rates is decreased with increasing CO₂ percentage due to the effects of CO₂ dilution, which is categorized as dilute effect, chemical effect and radiation effect. The extinction limits and flame temperatures are increasing with increasing atmospheric pressure and temperature, but the flame thickness is decreased with the pressure. At higher pressure and temperature, the extinction limits are extended more on the high-stretch blowoff limits, indicating the influence of the ambient pressure and temperature on the chemical reaction.