Abstract
Compressed Natural Gas (CNG) direct injection engine has many advantages for the reduction of CO2 emission. For further improvement of those engines, a numerical simulation technique has been developed for the analysis of combustion process. Prior to an in-cylinder calculation, the wall function was modified to improve the accuracy of the wall heat loss. Then the nozzle-to-cylinder entire calculation was performed. Good agreements were obtained in comparison with the experiment for the behavior of impinging jets. This method was applied to the analysis of the difference of combustion processes between CNG and conventional gasoline direct-injection engines. It is accordingly found that the velocity and the turbulence of in-cylinder gas are increased by the fuel injection into CNG engine and thus the combustion speed is enhanced significantly.
