Investigation of soot suppression by ammonia addition to laminar ethylene flames at varying pressure

Abstract

Blending ammonia with hydrocarbon fuels is a promising pathway to expedite its use in different industries, as it might offer a good compromise between energy output and minimizing the emissions of both NOx and carbonaceous combustion products, including soot. This work describes the effects of pressure on soot formation in ethylene/ammonia laminar co-flow diffusion flames. A high-pressure chamber was used to study the flames at pressures between 1 to 7 atm, and ammonia addition mole fractions between 0 and 50% (38% in mass fraction). Soot volume fraction and soot temperature measurements using a Spectral Soot Emissions technique show that adding a 50% mole fraction of ammonia at atmospheric pressure reduces soot concentration below the detection limit of the technique and between 70% and 80% for all the remaining studied pressures; that is, the ammonia soot suppression characteristics are demonstrated when increasing pressure. Maximum soot yield and total volumetrically integrated soot volume fraction results are investigated to reveal the contrasting effects of pressure and ammonia addition on the flame structure and the soot formation mechanisms. The results showcase the potential of NH3 in high-pressure applications when mixed with hydrocarbon fuels to reduce carbon emissions.