Relationship between natural gas characteristics and performance of heavy duty engines

The present paper analyses in details the effects of natural gas (NG) composition variability, due to different NG sources, on engine performance and emissions. The application of this study is to give indications useful for designing, realising, and homologation of heavy duty engines fuelled with NG. The effects of fuel properties have been investigated by experimental tests carried out on heavy duty engine fuelled with different mixtures NG/Ni. In addition, general formulas for the computation of power and air/fuel ratio as a function of fuel physico-chemical properties have been determined. Therefore an useful parameter (Shift Index) for quantification of air/fuel (A/F) ratio variability connected to different fuel compositions has been defined and discussed. The global examination of above topics suggested that self-adapting closed-loop feed control systems have the potentiality to compensate the fuel variability. The different properties of the NG mixtures widely diffused on European market have been examined and discussed.