Variable-valve-actuation-enabled high-efficiency gasoline engine

Abstract

Abstract

Owing to their low carbon dioxide emissions and fuel consumptions, diesel engines have gained a significant market share of passenger cars in Europe. However, gasoline engines are exclusively used to power passenger cars in the People's Republic of China and many other countries. The introduction of diesel engines to the passenger car market in many countries is unlikely to take place in the near future because of the limited diesel fuel supply, higher cost of diesel cars, and public perception of diesel vehicles. Therefore, development of high-efficiency gasoline engines is of particular importance. As part of a State Key Project of the National Basic Research Program (the 973 Program), the present authors have carried out systematic research and development of a high-efficiency gasoline engine. The engine was equipped in production with devices for mechanically variable valve lift and timing and was operated with controlled autoignition (CAI) (homogeneous charge compression ignition) combustion under part-load conditions and spark-assisted combustion between the transitional region of CAI and the normal spark ignition (SI) combustion. This paper will describe the use of devices for variable valve lift and timing in a single-cylinder engine and their control. The engine performance and emission results in the CAI operational region are presented. The ability of the engine to achieve rapid and smooth transition between CAI and SI will be illustrated. A brief discussion of the implication of the results on the calculated driving-cycle fuel consumption will be given at the end. Finally, the plan for future development of a multi-cylinder engine of variable valve actuation will be given.