Combustion and Emissions Improvement of Engine Idling via Advanced Ignition Strategies

Future transportation requires a variety of propulsion systems, using sustainable and renewable energy sources with low carbon footprints. Spark ignition engines remain effective power systems for automotive applications, especially for light and medium-duty applications. However, SI engines are susceptible to excess emissions during engine cold start, as the in-cylinder temperature is low, which leads to unstable ignition and incomplete combustion. More effective and more reliable ignition sources, e.g., with properly modulated and elevated energy, become more favorable for engine cold start. The research results from the author’s lab show that the spark current boost is an effective way to stabilize the spark plasma, increase the discharge energy, and improve the flame kernel development. In addition, recent research results from the author’s lab indicate that the current boost ignition system can provide robust ignition control under low load and lean limit conditions, where ignition receives major challenges. In this study, an in-house developed current boost system is applied to provide flexible control of the discharge current level and discharge duration. The previous experimental results using the current boost system were limited to the constant volume combustion chamber and rapid compression machine. This study investigates the efficacy of the current boost ignition system on a spark-ignited inline 4-cylinder production engine. A special focus of this study is on the emission and combustion performance during engine cold start. The current boost ignition system is based on a multi-coil system with a discharge current level of 200mA. The emission and combustion performance has been investigated under various levels of engine loads, from idling conditions (1.1 bar BMEP) to medium engine load (5.5 bar BMEP).