Effects of Ambient Air Composition on Flame Temperature and Soot Formation in Intermittent Spray Combustion

The effects of CO₂ and N₂ mixing and the effect of O₂ concentration on intermittent spray combustion were examined experimentally under the same condition of ambient temperature and pressure, and the same injection pressure. Through the systematic experiments, it was confirmed that the O₂ concentration is the dominant factor affecting ignition delay and combustion duration. The flame temperature becomes lower with the decrease of O₂ concentration mainly due to the dilution effect. The decrease of flame temperature due to the dilution effect and that due to the thermal/chemical effect of CO₂ was quantified. Concerning the soot production, with the decrease of O₂ concentration, it is suppressed during the early stage of combustion, however it becomes higher in the middle to later stage of combustion.