Laser sheet droplet illumination was used to visualize the concentration of fuel droplets over the piston top area. Four different cylinder designs were examined: Open transfer channels and three types of cup handle transfer channels.
Optical access to the scavenging area of the engine was achieved by removing the silencer and use a window in the top of the engine. The engines were run at their rated speeds: 9000 rpm for three of the engines and 5800 rpm for one of them.
Images of the concentration patterns were captured at various crank positions, −20, −10, 0, 10, 20, 30 Crank Angle Degrees (CAD) from Bottom Dead Center (BDC). Results show that the concentration of fuel droplets is higher close to the back wall of the cylinder with cup handle transfer channels.
Late in the scavenging phase, the concentration pattern is more spread over the entire cylinder area, for all types of transfer channels.