An improved method for studying mixing-controlled compression ignition (MCCI) flame interactions with an engine combustion chamber has been developed. It is implemented in a constant pressure vessel, which contains a portion of a piston and a portion of a cylinder head, where the cylinder head is emulated by a transparent fused silica window. This method allows for vaporizing or combusting fuel jets to be imaged from two orthogonal directions. The piston and cylinder head can be adjusted to emulate in-engine piston positions from top dead center (TDC) to approximately 15 mm away from TDC. The design allows for pistons from engine bore sizes up to approximately 175 mm to be studied, including the ability to simulate injector spray included angles from 120°-180°. In this study, the piston was made as an extruded piston bowl profile, where the length of the extrusion approximated the arc length between two neighboring jets from a 6-hole injector.
Four high speed cameras and two photodiodes were used to simultaneously capture light emissions from two views. One camera with a CH filter provided a profile view, and the other three cameras (NL, CH, OH) provided a top view of the piston bowl through the transparent cylinder head.
The objectives of this study were to look at flame penetration in the piston bowl and squish region and at how the flame penetrates in the profile view, at four piston locations relative to TDC to be able to use this information as simulation validation data.
The resulting images from this improved method clearly show how the flame penetrates, spreads in the piston bowl, and is split between entering the squish region and recirculating along the cylinder head.