Experimental determination of direct injection homogeneous charge compression ignition (DI-HCCI) combustion regime

Homogeneous charge compression ignition (HCCI) is an advantageous combustion concept for internal combustion engines in terms of efficiency and pollutant emissions. However, the limited operating range of this combustion concept suppressed its successful utilization. One applicable method to use this combustion concept in engines is to combine it with other similar combustion strategies, such as diesel and partially premixed combustion (PPC), while each combustion concept come into work during its optimum operating range. In this study, the transition from partially premixed combustion (PPC) to homogeneous charge compression ignition (HCCI) combustion is determined based on investigating the performance and emission characteristics obtained from experimental data. The determination is based on the fact that in the direct-injection (DI) HCCI combustion, the stratification generated from the fuel injection is not an influencing factor. The results reveal that in the case of very early fuel injection timing (when the whole injection is completed before 60 crank angle degrees to top dead center) the HCCI combustion regime is obtained.