Prechamber optimal selection for a two stage turbulent jet ignition type combustion system in CNG-fuelled engine

Searching for further reduction of fuel consumption simultaneously with the reduction of toxic compounds emission new systems for lean-mixture combustion for SI engines are being discussed by many manufacturers. Within the European GasOn-Project (Gas Only Internal Combustion Engines) the two-stage combustion and Turbulent Jet Ignition concept for CNG-fuelled high speed engine has been proposed and thoroughly investigated where the reduction of gas consumption and increasing of engine efficiency together with the reduction of emission, especially CO₂ was expected. In the investigated cases the lean-burn combustion process was conducted with selection of the most effective pre-combustion chamber. The experimental investigations have been performed on single-cylinder AVL5804 research engine, which has been modified to SI and CNG fuelling. For the analysis of the thermodynamic, operational and emission indexes very advanced equipment has been applied. Based on the measuring results achieved for different pre-chamber configurations the extended methodology of polioptimization by pre-chamber selection and the shape of main chamber in the piston crown for proposed combustion system has been described and discussed. The results of the three versions of the optimization methods have been comparatively summarized in conclusions.