The typical tradeoff between the two major emissions from compression ignition (CI) engines, smoke and oxides of nitrogen, is the unresolved challenge to the researchers. Techniques like engine downsizing, lowering intake oxygen concentration, multiple injections, use of retarded injection timings and higher injection pressures, etc. are widely employed for the alleviation of these harmful emissions. The influence of variation of fuel injection pressure (FIP), boost pressure, pilot injection timing (PIT), pilot injection quantity (PIQ) and main injection timing (MIT) are experimentally investigated in the present work. Mahindra mHawk four-cylinder diesel engine with provisions of a variable-geometry turbocharger (VGT), exhaust gas recirculation (EGR), and common-rail direct injection (CRDi) is chosen for the experimentation. Test runs are conducted at 1750 rpm and 80.3 N.m (4.6 bar bmep) corresponding to highway drive conditions, using 10 % EGR. Response surface methodology is employed for the design of experiments and to analyze the experimental data. Multi-objective response optimization is carried out to optimize engine-operating parameters that give desired performance and engine-out emissions. Confirmatory tests are conducted at design conditions to validate the results predicted by the model. This study reveals that the optimum performance and emission characteristics could be obtained using 120 kPa boost pressure; 61.1 MPa fuel injection pressure; 11.5 % pilot injection quantity with pilot injection at 332 °CA and main injection at 359 °CA.

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