Optimization of EGR effects on performance and emission parameters of a dual fuel (Diesel plus CNG) CI engine: An experimental investigation

Rapidly depleting conventional fuel reserves had prompted research on alternative fuels for diesel engines as diesel is most widely used in public transportation all over the world. The environmental consequences of using diesel are also encouraging to shift our focus towards alternative fuels. The nitrogen oxides (NOx) and smoke are the significant emissions that must be controlled effectively as the NOx is responsible for forming the acid rain and ozone layer depletion, which is further associated with the adverse effects on the health of human being. It is clear from the previous literature that diesel can be partially replaced by compressed natural gas (CNG) in a compression ignition (CI) engine and able to reduce NOx and smoke emissions. In the this research, tests are performed on a variable speed CI engine operated under dual fuel mode (D + 10% CNG), (D + 15% CNG) and (D + 20% CNG) modes at various exhaust gas recirculation (EGR) rates, such as 5%, 10% and 15% for three different loading conditions. The results showed that in all loading conditions, BTE dropped by 1-2% and the BSFC decreased at higher load by 2-3% as compared to diesel. The HC and CO emissions are higher at low and high load conditions as compared to diesel. In dual fuel mode, the highest reduction in NOx and smoke is 21% and 18% respectively as compared to diesel. A model equation is developed using ANOVA analysis to optimize the emission results.