Research on Performance and Temperature Control of Glow Plugs for PPCI Low Load Assist

Partial premixed compression ignition (PPCI) combustion is one of the most promising concepts to achieve combustion with high efficiency and low engine emissions. Glow plugs can be utilized to increase the combustion stability of PPCI combustion at idle or low loads, assisting the auto-ignition of gasoline or fuel with high octane number, which are major challenges remaining in PPCI combustion. The low load ignition assist application of glow plug is quite different from the traditional cold start assist. Other than simply heating the air in the cylinder, in the PPCI application the glow plug needs to heat the charge to specific temperatures at specific time, because the heating is vital to the ignition timing control in PPCI combustion. As a preliminary work of PPCI combustion low load assist application, in this paper infrared thermometer and some other devices were utilized to study the performance of representative glow plugs in open air. Based on the experiments, GPCU (glow plug control unit) was designed, open-loop and closed-loop temperature control algorithms were proposed. Further a lumped heat capacitance model of the glow plug was built based on system identification to study glow plug surface temperature behavior. It was found that PSG glow plug has excellent performance, maximum temperature of more than 1200°C was observed, 600 °C surface temperature was achieved in around 3 seconds. Open-loop temperature control was verified on GPCU; two glow plug temperature models were proposed, which can estimate the glow plug temperature for feedback control.