Imaging studies of in-cylinder HCCI combustion

Abstract

An optically accessed, single cylinder engine operated in homogenous charge compression ignition (HCCI) mode with negative valve overlap (NVO) strategy was used to perform combustion processes diagnostics under premixed conditions corresponding to the low load regime of the HCCI operational envelope. The aforementioned processes analysis was conducted utilizing synchronized simultaneous combustion event crank-angle resolved images, acquired through piston crown window with in-cylinder pressure recording. This investigation was carried out for one-step ignition fuel-standard gasoline, fuel proceeding single-stage ignition process under conditions studied. The initial combustion stage is characterized by a maximum local reaction spreading velocity in the range of 40-55 m/s. The later combustion stage reveals values as high as 140 m/s in case of stoichiometric combustion. The mixture as well as combustion stages effects are pronounced in these observed analytical results.