Towards Lower Engine-Out Emissions with RCCI Combustion

Abstract

AbstractFuture emission standards and renewable energy targets present a significant challenge for internal combustion engine manufacturers, requiring continuous improvements in efficiency and use of newly developed, preferably carbon neutral, fuels. As an answer to the future challenges, Reactivity Controlled Compression Ignition (RCCI) concept was developed with the aim to attain low emissions of NOx and particulate mass (PM) simultaneously. In the recent years, the RCCI concept is becoming even more attractive, since recently up-scaled renewable fuels exhibit a wide interval of different reactivities, making them ideal for obtaining the desired combustion parameters in RCCI combustion concept. In the present chapter, an application of direct injection of renewable Hydrotreated Vegetable Oil (HVO) and port injection of Methane rich natural gas in RCCI concept is discussed. The application features low local combustion temperatures preventing local formation of high NOx concentrations, with a high degree of charge homogenization, which is crucial for achieving low emissions of particulate matter. The presented results and discussion focus on the influence that different engine control strategies have on the main combustion process and emission indicators. Relations between different engine control strategies, including variation of energy shares of utilized fuels, direct injection timing of the direct injection and gas path control, engine thermodynamic parameters and engine-out emissions were deeply investigated and benchmarked with conventional diesel combustion. The results show that with an innovative combination of alternative fuels, significant simultaneous reduction of NOx and PM engine-out emissions can be achieved.KeywordsRCCIRenewable fuelsDual-fuel combustionLight-duty engineEmissions