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HCCI combustion has a disadvantage in controlling ignition timing. In this study, we applied Pulsed Flame Jet (PFJ) to HCCI under Exhaust Gas Recirculation (EGR) conditions. PFJ is the jet of burning gas issuing from a small cavity facing a combustion chamber. It is expected to advance autoignition. On the other hand, EGR leads to the retard of autoignition. Thus combining PFJ and HCCI may lead to the optimization of ignition timing. The experiments were performed with a rapid compression expansion machine. With PFJ, the indicated work under EGR conditions was improved by optimizing the timing of spark discharge of PFJ.

Combustion behavior in Rotary Engine (RE) is quite different from that in conventional reciprocating engines. Therefore, it is important to observe the combustion in RE. In the previous studies, an optical RE was developed, which enabled the observation of the flame propagation in the rotor rotating direction (side view). In the present study, modification was made to the optical RE so that the observation of the flame propagation in the rotor width direction (bottom view) became possible. By using two high-speed cameras, the combustion in RE was observed by bottom view and side view simultaneously. Consequently, it was found that the flame propagation in the rotor width direction is also important for better engine performance as well as that in the rotor rotating direction.

This paper describes the performance of an Imploding Detonation (ID) plug to ignite a lean methane-air mixture at high pressure and high temperature using a compact Rapid Compression Machine (RCM). The effects of the oxygen enrichment in the ID plug on the combustion characteristics in a combustion chamber were examined, varying oxygen fraction from 32 % to 40 %. The increase in oxygen fraction brought the increase in the burning velocity of the mixture in the ID plug, and thus the induction time of the imploding detonation was reduced. The increase in oxygen fraction also brought the increase in the momentum of the combustion jet that issued from the nozzle of the ID plug into the combustion chamber.