A Comparative Study of Combustion Stability Improvement via Prolonged Discharge Duration under Engine Idling Conditions

Proper control over combustion and emission characteristics under engine idling conditions remains to be challenging, especially when engine block temperature is low. In previous publication from the author’s laboratory, a specially designed common-coil pack was demonstrated to improve engine idling performance by supplying prolonged ignition duration and elevated discharge current amplitude. In this paper, the progress on further development of the ignition system was reported with improved system stability and enhanced ignition performances. The impact of discharge current amplitude and discharge duration on the combustion stability was investigated in detail under a wide range of spark timings, aiming to eliminate misfire events and reduce engine-out emissions under engine block temperature of 30°C. Such improvement can help to reduce the HC and CO emissions during engine cold start process before the light up of the three-way catalyst, therefore, reduce the total emissions of a standard engine test cycle. The energy consumption of the ignition system under various operation conditions are also calculated and compared with the extra engine power gained by the ignition system. Based on the research results, the concept of “crank-angle based spark duration” is proposed to provide different discharge duration under various engine speeds to support robust ignition process, as well as mitigate electrode erosion and improve spark plug lifespan. An on-demand control strategy is implemented using a standalone Field Programmable Gate Array system to self-regulate the discharging duration according to the engine speed. Thereby, the ignition energy can be provided sufficiently when the engine is required under various conditions.