Experimental Assessment of Effects of n-Butanol on Performance, Emission, and Combustion Characteristics of Mahua Oil Fueled Reactivity Controlled Compression Ignition (RCCI) Engine

The emission and combustion characteristics of diesel engine operated under reactivity controlled compression ignition (RCCI) mode are investigated in this study. A separate electronic fuel injector was mounted on the intake manifold of the engine meant for RCCI operation. RCCI mode of operation was conducted by injecting "n-butanol" as low reactivity fuel into the intake, and "mahua oil" as high reactivity fuel directly into the combustion chamber. Experimental results reported that smoke and nitric oxide (NO) emissions are significantly reduced by 45.4% and 33.1% through RCCI mode when compared with single fuel mode (mahua oil) at peak load. Carbon monoxide (CO) and unburnt hydrocarbon (HC) emissions were substantially increased at part load conditions in RCCI mode by increasing n-butanol energy share, while both HC and CO emissions were reduced at maximum power output. About 6.2% increase in brake thermal efficiency (BTE) of the engine was found when operated in RCCI mode, with up to 20% of n-butanol share; beyond this energy share, a marginal drop in BTE was noted at peak load. A substantial rise in cylinder pressure and heat release rate (HRR) was found while operating in RCCI mode. At part load, ignition delay was found to be longer in RCCI operation, but at supreme load condition, it was reduced. It was concluded that RCCI mode of operation improved the engine's performance and similarly reduced smoke and NO emissions.