| An investigation was made to determine the effects of hydrogen enrichment in the lean combustion regime for ethanol and to determine if it could extend the lean operating limit for both ethanol and methanol. In this study, a 0.745 liter 2-cylinder Kawasaki engine was modified to operate with both alcohol and hydrogen fuels. Hydrogen concentrations of 0%, 15%, and 30% by volume hydrogen in the primary fuel were fumigated into the intake before the throttle; the engine was operated at 2000 RPM and part throttle.;Data were collected to calculate NO and HC emissions, power, exhaust gas temperature, thermal efficiency, volumetric efficiency, brake-specific fuel consumption, and flame development and rapid burning angles. It was shown that hydrogen enrichment demonstrated an ability to not only decrease NO emissions, but also stabilize and accelerate the combustion process in the lean combustion regime. At a given equivalence ratio, hydrogen addition decreased NO emissions; this decrease was attributed to a change in dominate NO production mechanism(s) under lean operating conditions.;Hydrogen enabled a marginal extension of the lean operating limit (LOL) for both fuels, with the potential of further extending the LOL if the stability criteria are changed. Hydrogen enrichment at both 15% and 30% by volume reduced engine-out NO emissions near the lean operating limit by more than 95% relative to stoichiometric ethanol operation while both the COV and HC emissions were kept low, making it a potentially competitive alternative to NO reduction through traditional three-way catalytic aftertreatment. Power, thermal efficiency, and volumetric efficiency were not significantly affected by hydrogen addition at a given equivalence ratio; however, if hydrogen addition is used to decrease the lean operating limit, decreases in power and thermal efficiency were observed. Power in the lean combustion regime decreased by between 31 and 37% when compared to stoichiometric operation without hydrogen. |
