Fuel property effects on distributed combustion

•Examined the impact of fuel type on seeking volume distributed combustion.•Increase in gas entrainment and decrease in O2 conc. fostered distributed combustion.•Examined methane, propane, and hydrogen enriched methane flames.•Distributed combustion resulted in ultra-low emissions for all the fuels examined.•Relation predicting distributed combustion conditions is proposed for fuels examined.

Colorless Distributed Combustion (CDC) has been shown to provide benefits on ultra-low pollutants emission, enhanced stability and thermal field uniformity. The impact of fuel type (methane, propane, and hydrogen enriched methane) on achieving distributed combustion is investigated. A mixture of nitrogen and carbon dioxide was mixed, at different temperatures, with the normal air upstream of the combustor to simulate the hot recirculated gases. Increasing the amounts of nitrogen and carbon dioxide reduced the oxygen concentration within the combustor. Distributed combustion was identified through OH∗ chemiluminescence distribution across the combustor. For methane, this oxygen concentration varied between 13.8% and 11.2% (depending on the mixture temperature) with 85% reduction in NO emissions as compared to that without entrainment. Similar behavior was demonstrated with propane and hydrogen enriched methane, albeit at a lower oxygen concentration (13.7–11.6% and 12.2–10.5%), to result in 94% and 92% reduction in NO emission, respectively. The mixed gases temperature was varied between 300 K and 750 K. Experimental data using a variety of fuels showed NO emissions of 1 PPM or less. Analysis and extrapolation of obtained data suggest that distributed combustion can be achieved at an oxygen concentration of 9.5% for hot reactive entrained gases having a temperature of 1800 K. This value may be used as a guideline to achieve distributed combustion with ultra-low emission.