The Effect of Elevated Water Content on Ethanol Combustion: A Feasibility Study

In order to make ethanol economically competitive, market forces are demanding that the fuel deliver more energy per dollar invested. The process of distillation accounts for as much as 37% of the energy cost associated with producing bio-ethanol. This paper investigates the possibility of sustaining a combustion reaction with fuel that has a higher water content than is currently accepted as standard. The use of such aqueous fuel in lieu of the more energy expensive alternative could reduce the overhead of producing the fuel and lead to a better financial return. In this study, hydrous ethanol is burned in a continuous flame using a swirl-stabilized combustor with a dump diffuser at the inlet and pressure-orifice atomizing nozzles for fuel injection. The flame is observed as air flow rate is held constant and water content varies from 0% to 40% water. Fundamental relationships between water content and flame temperature, NOx formation, and lean blow out conditions are presented. By characterizing these relationships effectively it may be possible to establish an optimum water content that yields the highest energy delivered per dollar invested.