A high-efficiency 2-stroke engine concept: Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) engine with the air hybrid operation

Abstract

© 2019 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company. A novel 2-stroke Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) engine was proposed and designed to achieve aggressive engine down-sizing and down-speeding for higher engine performance and efficiency. In this paper, the design and development of the BUSDIG engine are reviewed and the key findings are summarised to highlight the progress of the development of the proposed 2-stroke BUSDIG engine. In order to maximise the scavenging performance and produce sufficient in-cylinder flow motions for fuel/air mixing process in the 2-stroke BUSDIG engine, the engine bore/stroke ratio, intake scavenge port angles and intake plenum design were optimized by three dimensional (3D) computational fluid dynamics (CFD) simulations. In addition, the effects of the opening profiles of scavenge ports and exhaust valves on controlling the scavenging process were also investigated. In order to achieve optimal in-cylinder fuel stratification, the mixture formation processes by different injection strategies were studied by using CFD simulations with a calibrated Reize-Diwakar breakup model. Based on the optimal design of BUSDIG engine, the one-dimensional (1D) engine simulations were performed in Ricardo WAVE and the results indicated that the maximum brake thermal efficiency of the 2-stroke BUSDIG engine can achieve 47.2% with lean combustion and water injection. The peak brake torque of 379 N∙m and peak brake power density of 112 kW/L were achieved at 1600 rpm and 4000 rpm respectively in the BUSDIG engine with the stoichiometric condition.