Multidimensional modeling of CNG direct injection and mixture preparation in a SI engine cylinder

In this study, a numerical model has been developed with avl fire softwareto perform an investigation into a direct natural gas injection into the cylinder of sparkignition internal combustion engines. two main parts have been taken into consideration,aiming to convert an mpfi gasoline engine to a direct injection ng engine. in the rstpart, multi-dimensional numerical simulation of the transient injection process, the mixingand the ow eld have been performed using dierent validation cases in order to assurethe numerical model validity of results. in all cases, the present results were found to haveexcellent agreement with experimental and numerical results from literature. in the secondpart, the validated model has been applied to methane injection into the cylinder of a directinjection engine. five dierent piston head shapes have been taken into considerationand a centrally mounted inwardly-opening single-hole injector has been adapted to allcases. the eects of injection and combustion chamber geometry have been studied onthe mixing of air-fuel inside the cylinder via quantitative and qualitative representation ofresults. furthermore, the eect of real engine cylinder head shape on gas injection has beeninvestigated. based on the results, suitable geometrical conguration for a ng di enginehas been discussed.