Experimental assessment on performance and combustion behaviors of reactivity-controlled compression ignition engine operated by n-pentanol and cottonseed biodiesel

Abstract

In relative to traditional combustion, the reactivity-controlled compression ignition (RCCI) technique using fuels with different reactivity has gained significant interest because of its high thermal efficiency and low NOx and smoke emissions. Hence, the present work investigates the RCCI mode of operation in a light-duty diesel engine by introducing Cottonseed oil biodiesel as high reactivity fuel directly into the combustion chamber and n-pentanol as low-reactivity fuel intake. The experimental results revealed that NOx and smoke emissions were considerably decreased by 44.2% and 35.0% with RCCI mode of operation compared to Cottonseed oil biodiesel-based operation mode at 100% load condition. However, a significant rise in emissions of unburnt hydrocarbon (HC) and carbon monoxide (CO) was noted at medium load (50%) conditions in reactivity-controlled compression ignition mode but emissions of HC and CO tended to decrease at peak load conditions. Moreover, the engine's brake thermal efficiency was found to increase by 7% when operating under RCCI mode at 20% of the n-pentanol share, although a marginal reduction in brake thermal efficiency was recognized in the case of above 20% energy share at 100% engine load. Considering the combustion characteristics, the RCCI mode working on Cottonseed oil biodiesel/n-pentanol showed substantial improvement in peak pressure and heat release rate compared with the single-fuel mode. Overall, it has been identified that the operation of diesel engines on RCCI mode could result in a simultaneous reduction of smoke opacity (up to 21.2%) and NOx emission (up to 36%) and a marginal improvement in the engine performance.