Multidimensional Modeling of CNG Direct Injection and Mixture Preparation in a SI Engine Cylinder


1 Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran

2 Amirkabir University of Technology (Tehran polytechnic), Tehran, Iran


In this study, a numerical model has been developed in AVL FIRE software to perform investigation of direct natural gas injection into the cylinder of spark ignition internal combustion engines. Two main parts have been taken into consideration, aiming to convert an MPFI gasoline engine to direct injection NG engine. In the first part multi-dimensional numerical simulation of transient injection process, mixing and flow field have been performed via different validation cases in order to assure the numerical model validity of results. In all cases, present results were found to have excellent agreement with experimental and numerical results from literature.

In the second part the validated model has been applied to methane Injection into the cylinder of a direct injection engine. Five different piston head shapes have been taken into consideration and a centrally mounted inwardly-opening single-hole injector has been adapted to all cases. The effects of injection and combustion chamber geometry have been studied on mixing of air-fuel inside cylinder via quantitative and qualitative representation of results. Furthermore the effect of real engine cylinder head shape on the gas injection has been investigated. Based on the results, suitable geometrical configuration for a NG DI engine has been discussed.