Validation of a 4-cylinder engine concept for heavy-duty vehicles with a parameterized model

Abstract

Carrying over the major trend of downsizing from passenger cars to commercial engines is not entirely possible for several reasons. One reason is that commercial engines have to also comply with the most stringent exhaust gas emission limits at full load. Another one is a much higher requirement regarding the life time of the engine. Both reasons limit the achievable specific performance to a rather low level compared to passenger car engines. Nevertheless development engineers are challenged more than ever with the need to reduce fuel consumption, size and weight of heavy duty engines. Moreover this has to be fulfilled at acceptable engine costs. This paper shows a possibility to combine the advantages of downsizing with the requirements of a commercial engine. This is achieved by reducing the number of cylinders but keeping the total displacement of the original engine.

The focus of the research is a 215 kW truck engine with a displacement of 7.4 l. This engine is realized as a 6 cylinder and as a geometrically similar 4 cylinder engine. Both engines are designed in CAD for geometrical investigations and in new engine models for thermodynamic investigations. The thermodynamic models were parameterized in terms of heavy duty engines. This models answers questions of friction, gas exchange and fuel consumption. Furthermore the models can be used for a wide range (3 l – 15 l displacement) of commercial vehicles.

The aim of this article is to provide a short overview of the structure of these different calculation models. These tools are developed for the very early stage of an engine design to judge about the engine performance beyond the application scope of the final engine. In summary each tool was used to compare the new engine layout of the 4 cylinder in contrast to a 6 cylinder engine in special and commercial engines in general.