عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In this study, a numerical model has been developed in AVL FIRE software to investigate combustion and injection inside the cylinder of a direct injection spark ignition CNG engine. In this regard two parts have been taken into consideration. In the first part of the study, gas injection via a single-hole injector into the cylinder with five different piston head geometries has been investigated. Using quantitative and qualitative representations of the results, the suitable combustion chamber geometry for DI application has been discussed. In the second part, combustion studies have been performed based on the selected geometry from the first part. Spark plug location and ignition timing have been investigated as two of the most important combustion variables. Five different configurations for the spark plug have been taken into consideration and the idea of using two spark plugs has been also tested, where it showed the best combustion characteristics. The spark timing has also been studied based on the selected configuration. The results show that ignition timing should be at 50 degrees before top dead center in order to have the best combustion characteristics.