Performance Characteristics of Lean Burn Engine Fuelled with Hydrogen Rich Gas from Plasma Fuel Reformer

In order to analyze the effect of hydrogen rich gas addition (HRG) on lean burn engine’s thermal efficiency and emission, an experimental research was conducted on a gasoline direct injection (GDI) engine using definite fraction of HRG. The results showed that HRG addition could significantly extend the lean operation limit, improve the engine’s lean burn ability, and decrease burn duration. HRG addition 10%, 18%, and 30% extended the lean limit equivalence ratio 0.62, 0.58, and 0.52 respectively. Combustion duration decreased as increasing fraction of HRG due to speed up flame propagation. HC emission decreased with the increasing fraction of HRG upto equivalence ratio 0.6 due to higher cylinder temperatures making it easier to burn lean mixtures. But thereafter HC emissions steadily increased despite of HRG addition as amount of fuel in regions was very lean to burn during primary combustion process. The same trend was observed in CO emission. However, nitrogen oxides (NOx) were found to increase with HRG addition because of hydrogen’s high burn speed. Thermal efficiency increased 3% with addition of HRG at equivalence ratio 0.7. The experimental results showed that the maximum brake torque timing (MBT), air fuel ratio and HRG supplementation were implied significant influence on lean limit operation, burn durations, thermal efficiency and exhaust emission. It was concluded that taking advantage of hydrogen’s high burn speed, obviously spark timing has to be retarded to MBT for substantial reduction of NOx emissions and further increase of engine’s thermal efficiency.