Experimental Investigation on the Influence of Simulated EGR Addition on Swirl-Stabilized CH4 Flames

Low-temperature combustion concepts for transport and power generation employ mixture dilution techniques, such as exhaust gas recirculation (EGR), that offer the potential of fuel flexibility, reduced pollutant emissions, and improved efficiency. These combustion modes, however, display a higher sensitivity to the compositional changes brought about by dilution, which in turn may have an adverse influence on the overall system performance. A fundamental study on the interactions between methane and simulated EGR was carried out on a swirl-stabilized, stoichiometric flame. The effects of varying levels and composition of diluents and preheating temperatures on flame structure and exhaust emissions, were experimentally investigated. Reductions of up to 90% and over 95% in NO_x and CO emissions, respectively, where observed for higher levels of added diluents, whereas an increase in preheating temperature resulted in the opposite trends. It has been further demonstrated that, depending on fuel and the chemical composition of the diluents, chemical effects on NO_x and CO emissions can be very significant.