The use of small engines as surrogates for research in aftertreatment, combustion, and fuels

In this research, small, single cylinder engines have been used to simulate larger engines in the areas of aftertreatment, combustion, and fuel formulation effects. The use of small engines reduces overall research cost and allows more rapid experiments to be run. Because component costs are lower, it is also possible to investigate more variations and to sacrifice components for materials characterization and for subsequent experiments. Using small engines in this way is very successful in some cases. In other cases, limitations of the engines influence the results and need to be accounted for in the experimental design and data analysis. Some of the results achieved or limitations found may be of interest to the small engine market, and this paper is offered as a summary of the authors' research in these areas. Research is being conducted in two areas. First, small engines are being used to study the rapid aging and poisoning of exhaust aftertreatment catalysts. This research includes diesel oxidation catalysts, lean NOx traps, and diesel particulate filters. Where necessary, additional bench reactor experiments have been added for more precise evaluation of the surrogate engine aged catalysts. The surrogate tests have been matched to the applications by scaling total lube oil consumption and space velocity and by compared to field service catalysts in order to compare mechanisms and rates of deterioration. On the engine side, the authors have converted both gasoline and diesel engines to homogeneous charge compression ignition for studying fuel chemistry and fuel property effects on advanced combustion. In this research, combustion phasing is controlled by combinations of valve timing, intake air heating, and compression ratio. Combustion is found to be a combination of low temperature and high temperature heat release and combustion behavior tracks mainly to traditional fuel properties such as cetane or octane, with some effects from more detailed chemical composition.