Experimental study of glow plug assisted compression ignition

The purpose of this study is to investigate the effects of glow plug assist on a four-cylinder compression ignition (CI) engine fueled with dieseline. Pressure sensor glow plugs (PSG) are utilized to assist low temperature combustion (LTC) at low to medium load range, and the glow plugs are required for fast response and accurate output control. Therefore, a glow plug control unit (GPCU) is developed, and a closed-loop power feedback control algorithm is used. Equipped with PSGs and GPCU, the engine is tested at three speeds under varying loads. As a part of multi-mode combustion for CI engines, glow plug assisted combustion (GA-CI) appears earlier combustion phases and higher peak in-cylinder pressure. GA-CI can effectively reduce cycle-to-cycle variations and misfire is avoided, especially at low load conditions. The nature of the glow plug assisting process is to enhance the in-cylinder temperature and fuel reactivity. Plus, glow plugs also play a role in triggering the auto-ignition of the pre-mixture. With glow plug assist, NOx emissions rise slightly but are still below 0.2 g/kW h, whereas particulate matter (PM) emissions drop sharply and decrease to under 0.02 g/kW h. Since CO emissions and HC emissions decrease as well, the combustion efficiency is significantly enhanced, with the maximum being over 98%.