Today, nations are in the path of low-emission transformation mandating stricter emission norms with periodic revisions. With the expected introduction of Bharath Stage VI (BS VI) for two wheelers in India by 2020, limitation in primary pollutants namely - Carbon Monoxide (CO), Total Hydro-Carbons (THC) and Nitrogen Oxides (NOx) are reduced by 50%, 75% and 85% respectively in comparison to the existing Bharath Stage IV. The original equipment manufacturers (OEMs) are identifying measures to improve the overall efficiency and raw emissions from the engine through strategies like multi-spark configurations, improved charge induction concepts, liquid cooling, lean combustion etc. With end user demands for performance, low end torque, high power to displacement ratio, quick acceleration and fuel efficiency, the balance with the emission regulation is expected to be challenging.
This study aims at understanding the typical thermodynamic losses associated with a liquid cooled single cylinder fuel injected spark ignition engine using Bosch Engine Combustion Analysis Tool (Be-CAT). The in-cylinder, intake and exhaust pressure measurements on the engine are the basis for the study. In the current study, the influence of multiple spark combustion is analyzed and compared against single spark combustion with equivalent ignition energy. Also multiple spark plug positions are evaluated and the ideal position for better-quality combustion is identified. Followed by, a study of ignition coil energies of 25mJ and 45mJ at the chosen spark plug position is conducted. The results indicate that the central spark plug position is favorable for least cyclic variations, two spark plugs mounted at side locations are ideal for low HC and CO emissions and the three spark plug configuration yields the least NOx emissions among the three configurations. The study also proves that increasing the ignition energy beyond what is required do not yield any benefits.