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Enhancement of mixture homogeneity for DI-CI engine to achieve Homogeneous Charge Compression Ignition (HCCI) combustion characteristics: a numerical approach

ABSTRACT Homogeneous Charge Compression Ignition (HCCI) engine is a new mode of engine combustion concept used for decreasing emissions like NOx and soot and to meet stringent emission norms. A numerical and modeling analysis of the performance and emission characteristics of a DI-CI engine is presented in this paper. The numerical analysis was carried out using CONVERGE CFD software. In this paper, four different engine parameters were considered, i.e., Compression Ratio (CR) (14.5 to 19.5), Exhaust Gas Recirculation (EGR) (0 to 30%), Fuel Injection Pressure (FIP) (200 to 280 bar), and Start of Injection (SOI) (17 to 29° CA bTDC). Response Surface Methodology (RSM) was used for developing the design matrix in the given parameter ranges. Results were analyzed in terms of NOx, soot emissions, and Indicated Specific Fuel Consumption (ISFC) with an objective of lowering ISFC, soot, and NOx. The statistical analysis showed that CR of 18.9, SOI of 25.89° CA bTDC, EGR of 24.9%, and FIP of 262.45 bar predicted as an optimum combination of operation parameters set. From the ANOVA analysis, it is observed that CR and SOI are the most influencing parameters on the output response parameters. The mixture homogeneity (i.e., Target Fuel Distribution Index (TFDI)) of air-fuel was improved by 19.2% for optimum configuration as compared to baseline configuration.