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Stringent emission legislations, increasing environmental and health issues, have driven extensive research on combustion engines to control pollutants. Modeling of emissions offers a cost-saving alternative to experimental analysis for combustion chamber design and optimization. Soot modeling in diesel engines has evolved over four decades from simple empirical relations to detailed kinetics involving polycyclic aromatic hydrocarbons (PAHs) and complex particle dynamics. Although numerical models have been established for predicting soot mass for parametric variations, there is a lack of modeling studies for predicting soot particle size distribution for parametric variations. This becomes important considering the inclusion of limits on soot particle count in recent emission norms. The current work aims at modeling the soot particle size distribution inside a heavy-duty diesel engine and validating the results for a parametric variation in injection pressure and intake temperature. Closed cycle combustion simulations have been performed using converge, a 3D computational fluid dynamics (CFD) code. A sectional soot model coupled with gas-phase kinetics has been used with source terms for inception, condensation, surface reactions, and coagulation. Numerical predictions for soot mass and particle size distribution at the exhaust show good agreement with experimental data after increasing the transition regime collision frequency by a factor of 100.

In this work, the influence of direct dual fuel injection on a compression ignition engine fueled with gasoline and diesel has been investigated. To do this, closed cycle combustion simulations have been performed. Gasoline has been supplied through port injection and early direct and late direct injection to achieve fuel stratification and emission reduction. Simulations have been done for various start of injection (SOI) timings of diesel fuel. A detailed discussion on a low temperature heat release (LTHR) mechanism has been done. Results revealed that the maximum gross indicated thermal efficiency (GITE) of 39% is obtained for port injection of gasoline mode. Direct dual fuel combustion (type 2) (DDC2) mode shows approximately 2% and 38% less GITE and oxides of nitrogen (NOx), respectively, and 40% more soot as compared to the port injection gasoline mode. DDC2 mode shows lower oxides of carbon and hydrocarbon emissions as compared to other dual fuel modes. More than 99% of combustion efficiency and less maximum pressure rise rate have been noticed in the DDC2 case. Strong LTHR and high temperature premixed combustion region have been found in advanced SOI timing cases (in DDC2). In-cylinder contours for the DDC2 case show that diesel and gasoline fuels combusted successively cause less in-cylinder temperature than that for the conventional dual fuel combustion case.