Computational Study of HCCI-DI Combustion at Preheated and Supercharged Inlet Air Conditions

In this work, combustion and pollutant formation phenomena in a direct injection Diesel engine are studied using n-Dodecane as fuel. The initial part of work is to validate the results from three dimensional computational fluid dynamics (CFD) with the engine experimental data. Various state-of-the-art models for simulating the droplet spray, impingement, collision, boiling and combustion are employed with the full kinetic mechanism. Extended coherent flame model for three zones predicts the averaged in-cylinder pressure data within 5 % of the experimental readings. CO, CO₂, UBHC and NO_x are found to be within the error limits between the CFD and experimental results. The CFD study is further extended towards the addition of little EGR for achieving lower NO_x emissions and partial injection of fuel in the intake stroke followed by main injection. To facilitate the easy evaporation and mixing of fuel, preheated air is introduced. As compared with early fuel injection without preheating, computed results with preheated inlet air show an increase in peak cylinder pressure. In the final part of CFD work, supercharged air is preheated to compensate for the reduced intake air. Predicted results reveal further increase in peak cylinder pressure with reduced emissions as compared with traditional injection timing results. The full cycle 3D-CFD multi-dimensional engine simulation carried out presents a detailed insight into the working conditions as in a real engine model.