Experimental Investigation of a RCCI Combustion Concept with In-Cylinder Blending of Gasoline and Diesel in a Light Duty Engine

Within this study a dual-fuel concept was experimentally investigated. The utilized fuels were conventional EN228 RON95E10 and EN590 Diesel B7 pump fuels. The engine was a single cylinder Diesel research engine for passenger car application. Except for the installation of the port fuel injection valve, the engine was not modified. The investigated engine load range covered low part load operation of IMEP = 4.3 bar up to IMEP = 14.8 bar at different engine speeds. Investigations with Diesel pilot injection showed that the dual-fuel approach can significantly reduce the soot/NO_x-trade-off, but typically increases the HC- and CO-emissions. At high engine load and gasoline mass fraction, the premixed gasoline/air self-ignited before Diesel fuel was injected.

Reactivity Controlled Compression Ignition (RCCI) was subsequently investigated in a medium load point at IMEP = 6.8 bar. Here, the impact of EGR, gasoline mass fraction and DI injection pressure and timing on emissions and combustion behavior were investigated. Despite elevated HC- and CO-emissions, it was possible to achieve a higher efficiency while simultaneously keeping the engine-out NO_x-emissions below the EU-6.1 level. Moreover, the combustion was almost soot-free and featured reduced noise emission compared to conventional Diesel injection compression ignition (DICI).