Abstract
Previous research indicated that the large NOx formation in diesel engines is due to the weak mixing intensity in the spray tip region, where the flow and turbulence structure is quite different from the continuous jet flames. The fact suggests that there is a possibility of reducing NOx from diesel engines by enhancing mixing intensity at the spray tip region to the level of continuous jet flame. As one of the attempts to make the velocity profile of diesel spray similar to the steady jet, an inert gas was injected prior to the fuel injection. With the pre-injection of inert gases, the flame apparently became less luminous, and NO concentration decreased compared to the case without pre-injection. This paper investigates the phenomena by sampling local gases to identify NO distribution in the flame at a moment.
