TY - JOUR
TI - UV-visible digital imaging of split injection in a Gasoline Direct Injection engine
AU - Merola Simona Silvia S
AU - Irimescu Adrian
AU - Tornatore Cinzia
AU - Valentini Stefano
AU - Krucȥek Grzegorz
AU - Szlęk Andrzej
AU - Adamczyk Wojciech
JN - Thermal Science
PY - 2015
VL - 19
IS - 6
SP - 1873
EP - 1886
PT - Article
AB - Ever tighter limits on pollutant emissions and the need to improve energy  conversion efficiency have made the application of gasoline direct injection  (GDI) feasible for a much wider scale of spark ignition engines. Changing the  way fuel is delivered to the engine has thus provided increased flexibility  but also challenges, such as higher particulate emissions. Therefore,  alternative injection control strategies need to be investigated in order to  obtain optimum performance and reduced environmental impact. In this study,  experiments were carried out on a single-cylinder GDI optical engine fuelled  with commercial gasoline in lean-burn conditions. The single-cylinder was  equipped with the head of a commercial turbocharged engine with similar  geometrical specifications (bore, stroke, compression ratio) and wall guided  fuel injection. Optical accessibility was ensured through a conventional  elongated hollow Bowditch piston and an optical crown, accommodating a  fused-silica window. Experimental tests were performed at fixed engine speed  and injection pressure, whereas the injection timing and the number of  injections were adjusted to investigate their influence on combustion and  emissions. UV-visible digital imaging was applied in order to follow the  combustion process, from ignition to the late combustion phase. All the  optical data were correlated with thermodynamic analysis and measurements of  exhaust emissions. Split injection strategies (i.e. two injections per cycle)  with respect to single injection increased combustion efficiency and  stability thanks to an improvement of fuel air mixing. As a consequence,  significant reduction in soot formation and exhaust emission with acceptable  penalty in terms of HC and NOx were measured.