Abstract
The present paper analyses in details the effects of natural gas (NG) composition variability, due to different NG sources, on engine performance and emissions. Two different type of fuel feeding system are analyzed: Venturi mixing system and multi point injection The application of this study is to give indications useful for designing, realising, and homologation of heavy duty engines fueled with NG.
The effects of fuel properties have been investigated by experimental tests carried out on heavy-duty engine equipped with the two mentioned fuel feeding system and tested with different mixtures NG/N2. 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 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 oil European market have been examined and discussed.