Flame Luminesce in an Optically Accessible Engine with an Active Fuelled Pre-Chamber Ignition System

Homogeneous lean or diluted combustion can significantly increase the efficiency of SI engines. Active fuelled Pre-Chamber ignition systems can overcome the problem that common spark ignitions systems are incapable to ignite strongly diluted mixtures. In the research project LEANition, an active Pre-Chamber with an integrated pressure transducer was developed. The active fuelling is done by volatile components of gasoline fuel using an in-house developed fuelling system. To understand the combustion processes with active Pre-Chamber ignition, optical investigations of the flame luminescence are performed inside an optical accessible engine through a piston crown window. To record single cycles with high temporal resolution, an highspeed intensifier and a highspeed camera was used to reach an imaging frequency of 36 kHz. The selected engine speed is 1200 rpm. Both stochiometric composition and lean charges at Lambda = 1.8 in the cylinder are investigated regarding the ignition and combustion processes. In lean cylinder environments the jets from the Pre-Chamber entrain the surrounding gas and the ignition expands from the center of the jets to the remaining cylinder. In contrast to this, at stochiometric cylinder charges, the jets cross the cylinder bore at high speed, the cylinder combustion is induced from the outside of the cylinder bore inwards to the middle of the bore. Increased charge motion in the cylinder with imposed swirl decreases the combustion duration as the flame front reaches the area between the reactive jets faster.