Strategies and methods of RCCI combustion: A review

Reactivity controlled compression ignition (RCCI) is found promising low temperature combustion mode that has recorded tremendous success towards improving thermal efficiency and reducing NOx and soot emissions to nearly zero but has high specific fuel consumption, unburned hydrocarbon (UHC) and carbon monoxides (CO) emissions. Besides, RCCI requires combustion phasing control and loads extension to higher levels. Numerous researchers employed different strategies like use of exhaust gas recirculation (EGR) rate and dual fuel control to improve RCCI combustion performance and emission characteristics but little attention was paid to some strategies such as use of dual direct injection, oxygenated biofuels, and fuel additives. In addition, most of the researchers do consider one strategy without exploring the combined effects of many strategies at a time; hence, the technique requires combined strategies and methods for effective control and improved performance. This paper reviewed previous research activities and recent reviews on RCCI engine performance and emission characteristics with the view to finding information on current RCCI combustion methods and strategies while identifying its shortcomings. Eventually, some challenges of RCCI that affects its adaptability for effective commercialization were identified with respect to strategies integration and areas that require more efforts for more advances in the combustion mode were suggested.