Spatiotemporal flame luminosity and solid particle characteristics in a gasoline direct injection engine

Since gasoline direct injection(GDI) engines have the advantages of improved compression-ratio and high performance, the usage of GDI engines has been increased worldwide. Lean burn from GDI engines improves fuel economy; however, high engine-out particle number(PN) and mass(PM) have been issued from GDI engines. In this study, engine-out PN and PM were experimentally investigated from a GDI engine operating in lean and stoichiometric combustion modes with in-cylinder spatiotemporal flame luminosity. A multi-channel optical sensor was used to measure the flame characteristics in the combustion chamber during the combustion process. Lean combustion mode can achieve 10 % less fuel consumption and stable operation under high load and speed Lean mode shows one-tenth particle mass concentration compared to stoichiometric mode even with strong diffusion flame propagations. The source of large particles(> 50 nm) is highly related to the mixture formation and combustion process, whereas the small particles come from other sources.