Combustion Stability Improvement via Multiple Ignition Sites on a Production Engine

For spark ignition (SI) engines, further improvement of engine efficiency has become the major development trend, and lean burn/EGR technologies, as well as intensified in-cylinder flow, need to be adapted to reach that target. Stronger ignition sources become more favorable under extreme lean/EGR conditions. Among the ignition technologies developed, multiple ignition sites technology has been proved to be an effective way to help with the initial flame kernel development. In this paper, a spark ignited 4-cylinder turbo-charged production engine is employed to investigate the impact of multiple ignition sites technology on engine performance under lean burn conditions. Four in-house designed 3-core sparkplugs are installed on the cylinders to replace traditional stock sparkplugs, in order to generate multiple ignition sites in the cylinders. Under partial load, the pumping loss can be reduced when engine is running under lean conditions, so the brake engine efficiency can be improved. However, combustion stability becomes worse in terms of higher cycle to cycle variation of the engine IMEP. Compared with traditional ignition system, the multiple ignition sites technology can extend engine lean operation limit with shorter ignition delay, which can effectively reduce the cycle to cycle variation.