The Modeling and Design of a Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) Engine

摘要

Engine downsizing of the spark ignition gasoline engine is recognized as one of the most effective approaches to improve the fuel economy of a passenger car. However, further engine downsizing beyond 50% in a 4-stroke gasoline engine is limited by the occurrence of abnormal combustion events as well as much greater thermal and mechanical loads. In order to achieve aggressive engine downsizing, a boosted uniflow scavenged direct injection gasoline (BUSDIG) engine concept has been proposed and researched by means of CFD simulation and demonstration in a single cylinder engine. In this paper, the intake port design on the in-cylinder flow field and gas exchange characteristics of the uniflow 2-stroke cycle was investigated by computational fluid dynamics (CFD). In particular, the port orientation on the in-cylinder swirl, the trapping efficiency, charging efficiency and scavenging efficiency was analyzed in details. Following the CFD analysis, a single-cylinder uniflow 2-stroke research engine was commissioned and successfully operated with spark ignition combustion. The design of the engine is characterized with the compression ratio flexibility, intake port configuration flexibility, port/valve timing flexibility as well as the provision of optical access. The engine was used to carry out in-cylinder flow measurements by the PIV technique. The measured PIV results were then compared with the CFD outputs.