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The combustion and emissions of a diesel/natural gas dual-fuel engine are studied. Available engine experimental data demonstrates that the dual-fuel configuration provides a potential alternative to diesel engine operation for reducing emissions. The experiments are compared to multi-dimensional model results. The computer code used is based on the KIVA-3V code and consists of updated sub-models to simulate more accurately the fuel spray atomization, auto-ignition, combustion and emissions processes. The model results show that dual-fuel engine combustion and emissions are well predicted by the present multi-dimensional model. Significant reduction in NOx emissions is observed in both the experiments and simulations when natural gas is substituted for diesel fuel. The HC emissions are under predicted by numerical model as the natural gas substitution is increased.

In order to meet stricter diesel engine emissions regulations, several researchers have investigated the feasibility of utilizing natural gas as an alternative engine fuel. This study reports the performance, gas-phase emissions, and particulate emissions of a single-cylinder prechamber type diesel engine modified to run on natural gas/diesel dual fuel. During dual fueling, up to 73 percent of the diesel fuel energy input was replaced with natural gas while the engine power output was maintained at levels similar to those obtained using diesel fuel alone. Thermal efficiency obtained was 38 percent lower for dual-fueling than for straight diesel fueling at one-quarter load. However, at full load the thermal efficiency obtained for dual fueling was similar to that for straight diesel fueling. Similar exhaust NOx concentrations were obtained at one-quarter load, but at higher loads NOx concentrations were higher for dual fueling.