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According to thermodynamic analysis of ideal engine cycles, Otto cycle thermal efficiency exceeds that of the Diesel and Sabathe (or Dual) cycles. However, zero-dimensional calculations indicated that the brake thermal efficiency (BTE) of an actual Otto or Diesel engine could be higher with a Sabathe (or Seilliger) type cycle, within a limited peak firing pressure (PFP). To confirm these results with an actual engine, a three-injector combustion system (center and two sides) was utilized to allow more flexibility in the heat release rate (HRR) profile than the conventional single injector system in the previous study. The experimental result was qualitatively consistent with the calculated results even though its HRR had less peak and longer duration than ideal. In this study, a new thermodynamic cycle with higher HRR in the expansion stroke than the ideal Sabathe cycle, was thus developed. The proposed (higher) HRR was achieved by overlapped fuel injection with the three injectors.

In spite of the increasingly stringent emission standards, the constant growth of road traffic contributes to climate change and induces detrimental effects on the environment. The European REWARD project (REal World Advanced Technologies foR Diesel Engines) aims to develop a new generation of Diesel engines complying with stricter post Euro 6 legislation and with lower CO2 emissions. Among the different technologies developed, a fuel-efficient two-stroke Diesel engine suited for C-segment passenger cars will be designed and experimentally evaluated. One major challenge for two-stroke engines is the achievement of an efficient scavenging. As the emptying of the in-cylinder burnt gases and the filling by fresh gases is performed at the same time, the challenge consists in removing as much burnt gases as possible while avoiding the by-pass of fresh air toward the exhaust line.