Performance and Emission Characteristics of n-Butanol and Iso-Butanol Diesel Blend Comparison 2015-01-2819

The growing energy demand and limited petroleum resources in the world have guided researchers towards the use of clean alternative fuels like alcohols for their better tendency to decrease the engine emissions. To comply with the future stringent emission standards, innovative diesel engine technology, exhaust gas after-treatment, and clean alternative fuels are required. The use of alcohols as a blending agent in diesel fuel is rising, because of its benefits like enrichment of oxygen, premixed low temperature combustion (LTC) and enhancement of the diffusive combustion phase. Several researchers have investigated the relationship between LTC operational range and cetane number. In a light-duty diesel engine working at high loads, a low-cetane fuel allowed a homogeneous lean mixture with improved NOx and smoke emissions joint to a good thermal efficiency. The very low cetane number limits the usage of neat alcohols in diesel engines so they should be blended with diesel fuel without any modifications in the engine fuel system. Alcohol has higher heat of vaporization; therefore, it reduces the peak temperature inside the combustion chamber leading to lower NOx emissions and increased engine power. The oxygen presence in alcohol fuel provides soot-free combustion. Long chain alcohol like butanol is better suited for blending in diesel than short chain alcohol like methanol and ethanol, because of its higher energy content, stability in blend, low corrosiveness and lower miscibility in water. The use of EGR with blends of butanol and diesel can achieve LTC and simultaneously decrease the NOx emissions and the soot emissions with a slight decrease in the fuel economy. An experimental investigation is conducted to evaluate the effects of using blends of n-butanol and isobutanol with diesel fuel separately, with 10%, 20% and 30% (by volume) of both the alcohols, on the performance and exhaust emissions namely brake specific fuel consumption (BSFC), brake thermal efficiency (BTE) and emissions of CO, HC and NOx of a single cylinder, four-stroke, direct injection diesel engine employing EGR.