Advanced Ignition System to Extend the Lean Limit Operation of Spark-Ignited (SI) Engines—A Review

Lean-burn spark-ignition (SI) engines are envisaged as the future combustion engines owing to its higher efficiency and lower engine-out emissions. Lean-burn SI engine has several advantages over the conventional SI engine like lower in-cylinder temperature, reduced heat losses, better thermodynamic and combustion efficiency and lower hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxide (NOX) emissions. However, few practical difficulties associated with lean-burn SI engine include combustion instability, engine misfire and lower flame speed. The development of advanced ignition systems increases the flame speed and achieves stable combustion in lean-burn SI engines. The most common advanced ignition systems which are efficient and widely researched for lean-burn SI engines are laser ignition (LI), turbulent jet ignition (TJI), radio-frequency corona ignition (RFCI) and microwave-assisted spark-ignition (MASI) system. The major objective of these advanced ignition system is to increase the supplied ignition energy and induce multi-point ignition to support the development of lean-burn SI engines. The principle of operation, fundamental understanding, engine characteristics, advantages, limitation and challenges of these advanced ignition systems are discussed briefly in this chapter.