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In this work, optimization of various parameters, such as injection timing, compression ratio (CR) and amount of ultra-cooled exhaust gas recirculation (EGR) has been done for a variable compression ratio engine. The CR can be adjusted dynamically by changing the clearance volume through a tilting cylinder block arrangement. An EGR system, suitable for achieving ultra-cooled as well as treated EGR and large range of flow rates, has been implemented. Taguchi analysis was employed to carry out minimum number of experimental runs and still get the essence of large number of test cases. Effect of these parameters on engine performance and exhaust emissions has also been studied with the help of signal to noise (SN) ratio analysis. Flatter and wider HRR traces were observed in previous work of Brijesh et al., indicating a low temperature combustion (LTC) mode for the runs having optimized input parameters.

The mixture generation in Diesel engines is mainly driven by the combustion chamber geometry and the fuel spray characteristics. Thus, combustion chamber geometry is considered as an important parameter for Diesel engine in-cylinder emission control strategy. In this work, effect of nozzle tilt angle and various combustion chamber geometries such as mexican-hat combustion chamber (MHCC), double-lip combustion chamber (DLCC), bow combustion chamber (BCC) and toroidal combustion chamber (TCC) on in-cylinder processes and emissions has been studied numerically using a CFD-tool called Converge. Converge code has been validated against the experimental results of a Diesel engine. Results showed that a significant reduction in soot, HC and CO has been achieved with the optimum (156°) nozzle tilt angle; but NOx was increased.