Advanced Combustion Technologies for Higher Thermal Efficiency

Recently, new technologies for higher thermal efficiency have been developed in internal combustion engines. New types of combustion processes and technologies have been proposed regardless of the type of an engine. Low temperature combustion (LTC) such as homogeneous charge compression ignition (HCCI) has been studied to achieve low NOx (oxides of nitrogen) and particulate matter (PM). This chapter discusses history and advantages of the HCCI combustion. HCCI combustion technology has been evolved into the reactivity controlled compression ignition (RCCI) and spark assisted compression ignition (SACI) types. Abnormal knocking combustion that occurs due to the flame propagation and thermochemical autoignition in the end-gas region is considered one of the barriers to achieve higher thermal efficiency. However, under controlled conditions, knocking combustion can be avoided in SACI and in the Premixed Mixture Ignition in the End-gas Region (PREMIER) combustion processes. Furthermore, new laser- and plasma-based ignition systems have been developed instead of conventional spark ignition system. Laser ignition, non-thermal plasma assisted ignition such as microwave assisted spark ignition, nanosecond pulsed discharge, corona, etc. are described. These technologies are explained in this chapter, which shows future directions of internal combustion engines toward increasing thermal efficiency and minimizing NOx and PM emissions.