Design of a fuel-efficient two-stroke Diesel engine for medium passenger cars: comparison between standard and reverse uniflow scavenging architectures

International audienceIn 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 CO 2 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 bypass of fresh air toward the exhaust line. For the considered application, the uniflow scavenging architecture, which is featured by ports located in the bottom of the cylinder and valves in the head, is selected. Two possible arrangements for the intake and the exhaust are compared: either the standard configuration for which the intake is ensured by the ports and the exhaust by the valves or the reverse configuration. Both standard and reverse configurations are first compared through 0D system simulations, performed with LMS Imagine.Lab Amesim and then by 3D CFD simulations with CONVERGE. The standard configuration is favored, thanks to better ISFC performances, especially at low and medium loads operating conditions. In addition, the scavenging is strongly penalized for the reverse architecture due to the drag downstream the intake valves