Evaluation of Homogeneous Charge Compression Ignition at High Engine Speeds using a Super Rapid Compression Machine 2008-01-2403

We had improved RCM and developed a Super Rapid Compression Machine (SRCM) that realizes an extremely rapid compression compared with the conventional RCM. In this study, the performance of the developed SRCM was evaluated. The SRCM was used to investigate on the effects of equivalence ratio on HCCI of n-heptane and iso-octane fuel/air mixture. Experimental results for ignition delay time, τ, and combustion time, t, were obtained from the cylinder pressure histories. The HCCI at high engine speeds was clarified by Optical observation using a high speed camera. As a result, the ignition delay time and combustion time are found to saturate above equivalence ratio of 0.6 at constant compression ratio. In the HCCI combustion in high compression ratio case, shock wave occurs from the core region of the roll-up vortex cause by piston motion. The HCCI combustion has many peaks over a wide range of frequency.