Cylinder Charge, Initial Flow Field and Fuel Injection Boundary Condition in the Multidimensional Modeling of Combustion in Compression Ignition Engines

Cylinder charge, cylinder flow field and fuel injection play the dominant roles in controlling combustion in compression ignition engines. Respective computational cylinder charge, initial flow field and fuel injection boundary affect combustion simulation and the quality of emission prediction. In this study the means of generating the initial values and boundary data are presented and the effect of different methods is discussed. This study deals with three different compression ignition engines with cylinder diameters of 111, 200 and 460 mm. The initial cylinder charge has been carefully analyzed through gas exchange pressure recordings and corresponding 1-dimensional simulation. The swirl generated by intake ports in a high-speed engine is simulated and measured. The combustion simulation using a whole cylinder model was compared with a sector model simulation result. The difference between a sector mesh simulation and a whole cylinder model simulation was found to be considerable in case of a high speed diesel engine. In case of a medium speed engine the gains of using the whole cylinder model were more questionable. The simulation of fuel injection rate and injection velocity at the nozzle exit is presented in this study, as well. The validation of this simulation was made through injection pressure and injector needle lift measurements. The fuel injection boundary condition, the predicted injection velocity, was found to have a noteworthy effect on the simulated heat release.