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.

High unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions, on account of the premixed air-fuel mixture entering the crevices and pre-mature combustion, are setbacks to reactivity-controlled compression ignition (RCCI) combustion at a low load. The influence of direct-injected B5 and port injection of biogas at the intake valve was, experimentally, examined in the RCCI mode. The port injection at the valve was to elevate the temperature at low load and eliminate premixing for reduced pre-mature combustion and fuel entering the crevices. An advanced injection timing of 21° crank angle before top dead centre and fraction of 50% each of the fuels, were maintained at speeds of 1600, 1800 and 2000 rpm and varied the load from 4.5 to 6.5 bar indicated mean effective pressure (IMEP). The result shows slow combustion as the load increases with the highest indicated thermal efficiency of 36.33% at 5.5 bar IMEP. The carbon dioxide and nitrogen oxides emissions increased, but UHC emission decreased, significantly, as the load increases. However, CO emission rose from 4.5 to 5.5 bar IMEP, then reduced as the load increases. The use of these fuels and biogas injection at the valve were capable of averagely reducing the persistent challenge of the CO and UHC emissions, by 20.33% and 10% respectively, compared to the conventional premixed mode.

Gas turbines have long been utilized as the main device for power generator. High temperature of ambient air flowing into inlet can reduce their performance. The objective of this study is to investigate the performance of a 1.5 kW micro-gas turbine at reduced inlet temperature using dry-ice as the cooling elements. Dryice is placed surrounding the outer wall of contained in a net-like holder at the inlet before the compressor and the inlet air temperature found to be decreased till 13°C from the ambient temperature. Comparison test was performed with a baseline result, which is the operation without the dry-ice cooling unit and the results shows that the power output decreases linearly with the increase of inlet air temperature. It was recorded that increase power output of 8.5% achieved from reduction of temperature of 7.5%. The power output was found also to be decreased with time, due to the inlet duct exposed to the heat form the combustion chamber. This indicates better insulation or adapted data recording approach is needed.