Analysis of Engine Performances Improvement by Down Sizing in Relationship With Super- and Turbocharging, Adapted Scavenging and Direct Injection

摘要

The development of future internal combustion engines with high power density in correlation with drastically reduced fuel consumption/CO_2 emission and pollutant emission requires both an improvement of the thermodynamic process stages such as scavenging, mixture formation and combustion as well as new strategies regarding the engine function fields. An advanced concept in this direction is the combination of downsizing with supercharging and turbocharging coupled in different configurations.The paper presents the results of the comparison of four engine configurations: a 4-stroke, 4 cylinders engine family with gasoline direct injection: 1400 ccm engine, aspirated; 1400 ccm engine with turbocharging; 1400 ccm engine with super- and turbocharging; 1600 ccm engine, aspirated with a power range which is similar to the 1400 ccm engine with turbocharging. The experimentally obtained basic performances of these four engines are used in a numerical simulation program for analyzing the thermodynamic cycles and the behavior of maximum brake mean effective pressure, brake specific fuel consumption, carbon dioxide and pollutant emission, within the whole speed range when varying the intake/exhaust valve control and the direct injection modulation and timing. This analysis allows the development of an operation strategy for a compact engine with two stages of charging for maximum efficiency at minimum pollution. Such an engine configuration appears as an advantageous alternative to some mild or full hybrid configurations which combine the mechanical with the electrical propulsion.