An advanced combustion model coupled with detailed chemical reaction mechanism for D.I diesel engine simulation

摘要

A multi-dimensional computational fluid dynamics (CFD) modeling was conducted on a direct injection turbo-charged diesel engine based on KIVA-4 code under full and mid engine loads. Multi-component fuel evaporation model of KIVA-4 was used and coupled with advanced combustion chemistry to generate a multi-component fuel combustion model by integrating CHEMKIN Ⅱ into the KIVA-4 code. As the coding schema of KIVA-4 in the case of data/parameter allocation, etc. was different compared to previous version of KIVA-3V, a considerable amount of FORTRAN programming was performed in order to develop a multi-component fuel combustion model. The developed combustion model was capable of modeling combustion process of number of chemical species as the components of direct injected liquid fuel. Comparing to the single component fuel combustion model, new model is capable of comprehensive combustion modeling of blend fuel and heavy hydro-carbon fuels. Furthermore, spray breakup and collision models were changed to more advanced Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) and O'Rourke models, respectively. The model was used to simulate direct injected diesel engine under full and mid engine loads at three engine speed conditions. Extracted temporal and spatial results for equivalence ratio distribution inside the combustion chamber showed that under full load condition, a considerable amount of fuel was trapped in piston bowl after initiation of the injection process where such fuel rich local regions provide the potential for production of higher soot emission. Mean value of the fuel concentration history showed that the ignition delay was increased under mid engine load at all engine speeds producing higher amounts of unburned hydro carbons and carbon monoxide. By reducing engine load and speed, output power was decreased as well. However, same trend was not reported for the indicated thermal efficiency as the middle engine speed in considered engine loads, had slightly higher efficiency.