Alternative Diesel fuels effects on combustion and emissions of an Euro4 automotive Diesel engine

The present paper describes the first results of a cooperative research project between GM Powertrain Europe and Istituto Motori of CNR aimed at studying the impact of Fatty-Acid Methyl Esters (FAME) and gas-toliquid (GTL) fuel blends on the performance, emissions and fuel consumption of modern automotive diesel engines. The tests were performed on the architecture of GM 1.9L Euro4 diesel engine for passenger car application, both on optical single-cylinder and on production four-cylinder engines, sharing the same combustion system configuration. Various blends of biodiesels as well as reference diesel fuel were tested. The experimental activity on the singlecylinder engine was devoted to an in-depth investigation of the combustion process and pollutant formation, by means of different optical diagnostics techniques, based on imaging multiwavelength spectroscopy. The tests on the multi-cylinder engine were done in a wide range of engine operation points for the complete characterization of the biodiesels performance in the new European driving cycle (NEDC). The optical engine results have confirmed the good quality of spray formation of FAME fuels with engine and their capability to reduce soot formation, thanks to lack of precursors and oxygen in the fuel. The four-cylinder engine results, besides validating single-cylinder outcomes, have also highlighted critical aspects on the interaction between the alternative fuel characteristics and the engine-management strategies of electronically-controlled diesel engines.