Diesel odor studies in a laboratory spray burner

Abstract

An air aspirated burner facility has been modified and instrumented for studying diesel odor formation. Odor sampling and analysis techniques, based on the Diesel Odor Analysis System (DOAS), have been developed and refined. Burner stoichiometry, combustion aerodynamics, swirl, wall quenching and fuel composition were investigated for their effect on odor formation. Fuel composition had a negligible influence and swirl had only a small effect except at very high swirl levels. The most significant factor was overall burner stoichiometry. This pronounced stoichiometry effect appears to be the result of the aerodynamic turbulence and wall quenching at lean operating conditions. Fuel droplet diameter, while having no direct effect on odor production, probably has an indirect effect through its influence on both aerodynamics and quenching. The effect of stoichiometry was to increase odor from very low or undetectable levels at equivalence ratios near 0.5 to moderate to strong levels as burner operation becomes very lean and to very strong levels at rich operating conditions. Increasing aerodynamic turbulence caused odor levels to drop by increasing the size and intensity of the recirculation pattern, thereby allowing more complete combustion. Conversely, increased wall quenching removed energy from the reaction zone, resulting in incomplete combustion and higher odor levels. Very high swirl appeared to cause faster reaction rates and lower odor levels.