Effect of a Cetane Number (CN) Improver on Combustion and Emission Characteristics of a Compression-Ignition (CI) Engine Fueled with an Ethanol-Diesel Blend

摘要

Ethanol-dieset blended fuel has the potential to reduce diesel engine exhaust smoke and particulate emission as well as partially solve the energy crisis. However, with the increase of the ethanol fraction of the blends, the engine combustion will be affected significantly because of the change of fuel properties, especially the ignition delay (τ_(ig)). Generally, a cetane number (CN) improver should be added to improve the engine combustion. In this study, E30 (30 vol % of ethanol in the blend) was prepared. A CN improver was added at 0,0.3, and 0.6% (in volume), respectively. With a two-cylinder diesel engine, the effects of a CN improver on the engine combustion and emissions were investigated. Experimental results show that, in comparison to the diesel engine, the brake thermal efficiency of the E30 engine is improved, the τ_ig is prolonged, while the total combustion duration becomes shorter. With the increase of the CN improver fraction, the brake thermal efficiency, diffusive combustion phase, and total combustion duration all increase, while the τ_ig decreases. The addition of ethanol and a CN improver in diesel has no effect on nitric oxides (NO_x); however, the particulate matter (PM) and smoke emissions of the E30 engine decrease significantly, and they will be deteriorated with a high fraction blending of a CN improver.