Experimental investigation on the effects of multiple injections and EGR on n-pentanol–biodiesel fuelled RCCI engine

Stringent emissions and fuel economy regulations have necessitated the need to boost the research interest in oxygenated alternate fuels such as n-pentanol and biodiesel under low-temperature combustion strategies due to their renewability and cleaner combustion characteristics. Being higher alcohol, n-pentanol has desirable fuel properties that are comparable to mineral diesel, which enable easy blending of these fuels. In the present study, the Reactivity Controlled Compression Ignition (RCCI) operation in a modified single-cylinder diesel engine operating at the rated speed of 1500 rpm and 50% load was investigated with non-edible karanja oil-based biodiesel–diesel blend with B20 as high reactivity fuel (HRF) and n-pentanol as low reactivity fuel (LRF). The intake temperature was maintained constant at 40 °C, intake pressure was ambient and the LRF was varied from 20% to 50%. The engine's performance with split injection was investigated by sweeping starts of injection (SOI) crank angles and these were optimized at 47°, 27°, and 17° bTDC for SOI 1, SOI 2, and SOI 3 respectively at 400 bar injection pressure. The engine performance characteristics were investigated by introducing 10% to 30% cooled exhaust gas recirculation (EGR) and was optimized at 25%, based on the stable operation of the engine with acceptable ringing intensity and emission. The combined effect of EGR, multiple injections (three), and varying PFI mass fractions was investigated and compared with a single injection of HRF. A simultaneous reduction of 76% smoke and 91.5% NO(X) emission was obtained with a marginal increase in CO and HC emissions.