surfaces of the chamber was composed of pyrex glass to observe spray and flame developments, and the other side surface had an injector holder.

Figure 3.1.1.1: Schematic diagram of experimental apparatus

During experiment, the fuel injection is varied by controlling the common rail system. Nevertheless, the ambient condition of the combustion chamber was controlled by the air motion and temperature. Piston (aluminum 17ST-4) motion induced air inside the chamber. The RCM has a portable swirler at intake ports which allow the amount of swirl to be varied at 10-60 m/s by changing the port inclination angle controlled swirl velocity. Base swirl velocity r_s was r_s =19 m/s in this study.

3.1.2 Optical Setup

In this study, mixture formation, initial flame and burning process were examined by measuring the in chamber pressure and observation of direct photograph taken by high-speed color digital video camera (NAC, GX-1) via a