Fuel flexibility study of various fuels with charge dilution and high compression ratio for medium-load operating RCCI engine

Abstract

This study examines the dual-fuel (RCCI) combustion mode using gasoline, ethanol, methanol, and compressed natural gas (CNG) as low reactive fuels (LRF) and diesel, neem biodiesel as high reactive fuel (HRF). The fresh and diluted charge (with hot EGR) combustion is compared at a high compression ratio for medium load operation. For obtaining the near-zero NOx-soot emissions and improved performance, the feasibility of different reactivity and renewable fuels are studied. The use of methanol and gasoline as LRF and diesel as HRF with charge dilution shows improved fuel-air-mixing, reactivity stratification, and thermal efficiency. The use of ethanol and gasoline as LRF and biodiesel as HRF with charge dilution shows near-zero NOx emissions while soot emissions are above the minimum acceptable range. The use of CNG as LRF and diesel as HRF with charge dilution shows minimum thermal efficiency and high fuel consumption. The reduced combustion rate and increased premixed combustion with charge dilution result in lower combustion temperatures and pressure rise rates for G + D and M + D.