Experimental comparison of acetone-n-butanol-ethanol (ABE) and isopropanol-n-butanol-ethanol (IBE) as fuel candidate in spark-ignition engine

Among primary alcohols, bio-n-butanol is considered as a promising alternative fuel candidate. However, relatively low production efficiency and high cost of component recovery from the acetone-n-butanol-ethanol (ABE) or isopropanol-n-butanol-ethanol (IBE) fermentation prevents bio-n-butanol's use in modern engines. Therefore, the purpose of this study is to compare the potential of ABE and IBE as fuel candidate in spark ignition (SI) engine. The combustion, performance and emissions characteristics of the engine without any modifications fueled with ABE- and IBE-gasoline blends were investigated. It was found that IBE-gasoline blends showed an advanced combustion phasing with a shorter initial and major combustion duration compared to gasoline and ABE-gasoline blends. In comparison with ABE10 (10 vol% ABE blended with gasoline) under various lambda from 0.8 to 1.2 and engine loads of 3 and 5 bar BMEP, IBE10 enhanced brake thermal efficiency by 0.9-1.8% and reduced carbon monoxide, unburned hydrocarbons and nitrogen oxides emissions by 0.9-7.3%, 3.3-25.1% and 1.6-5.9%, respectively. Due to the greater potential to increase energy efficiency and reduce pollutant emissions and more desired properties (less corrosive to the engine parts, higher energy content and octane number, etc.), IBE seems to be more attractive than ABE for fuel application in SI engine.