Combustion stratification and dynamic flame tracing analysis of partially premixed combustion in a compression ignition engine fueled with low-octane fuel 2019-01-1151
Partially premixed combustion (PPC) is one of the low temperature combustion (LTC) concept, which is between the conventional diesel compression ignition (CI) and the homogeneous charge compression ignition (HCCI). In PPC mode, the start of injection timing (SOI) is earlier than that of CI and later than that of HCCI and a stratified in-cylinder fuel/air mixture can be formed to control the auto-ignition by the fuel injection timing. Gasoline fuel is beneficial for PPC mode because its superior resistance to auto-ignition can enhance the fuel-air charge mixing process with the longer ignition delay time. The scope of the present study is to investigate the ignition sensitivity of PPC to the injection timing at different intake temperature (Tin). To better understand this, the fuel-tracer planar laser-induced fluorescence (PLIF) imaging and the natural flame luminosity (NFL) from the high-speed imaging (natural chemiluminescence) were performed to visualize the fuel injection and the subsequent combustion process at different SOI with different Tin. The static and dynamic flame tracing was performed to evaluate the combustion stratification. The combustion stratification analysis indicated that more inhomogeneous low-temperature combustion was achieved along with the decreased NFL and increased soot when the Tin decreased. The injector dribbling during the late stage of combustion was verified as an important source of soot formation.
Yanzhao An, Hao Shi, R Vallinayagam, Jaeheon Sim, Junseok Chang, Bengt Johansson
King Abdullah Univ. of Science & Tech., King Abdullah Univ of Science & Tech, Saudi Aramco