A Comparison of Ethanol and Butanol as Oxygenates Using a Direct-Injection, Spark-Ignition Engine

Abstract

This study was designed to evaluate a “what if” scenario in terms of using butanol as an oxygenate in place of ethanol in an engine calibrated for gasoline operation. No changes to the stock engine calibration were performed for this study. Combustion analysis, efficiency, and emissions of pure gasoline, 10% ethanol, and 10% butanol blends in a modern direct-injection four-cylinder spark-ignition engine were analyzed. Data were taken at engine speeds of 1000 rpm up to 4000 rpm with load varying from 0 N m (idle) to 150 N m. Relatively minor differences existed between the three fuels for the combustion characteristics such as heat release rate, 50% mass fraction burned, and coefficient of variation in indicated mean effective pressure at low and medium engine loads. However at high engine loads the reduced knock resistance of the butanol blend forced the engine control unit to retard the ignition timing substantially, compared with the gasoline baseline and, even more pronounced, compared with the ethanol blend. Brake specific volumetric fuel consumption, which represented a normalized volumetric fuel flow rate, was lowest for the gasoline baseline fuel due to the higher energy density. The 10% butanol blend had a lower volumetric fuel consumption compared with the ethanol blend, as expected, based on energy density differences. The results showed little difference in regulated emissions between 10% ethanol and 10% butanol. The ethanol blend produced the highest peak specific NOx due to the high octane rating of ethanol and effective antiknock characteristics. Overall, the ability of butanol to perform equally as well as ethanol from an emissions and combustion standpoint, with a decrease in fuel consumption, initially appears promising. Further experiments are planned to explore the full operating range of the engine and the potential benefits of higher blend ratios of butanol.

Characterisation of flame development with ethanol, butanol, iso-octane, gasoline and methane in a direct-injection spark-ignition engine

“…Very few studies on butanol combustion in DISI engines exist in the literature. Wallner et al [18] studied the combustion performance of 10% ethanol and 10% butanol addition to gasoline in a 4-cylinder DISI engine. Data were taken at engine speeds in the range 1000-4000 RPM.…”

An Analysis of the Combustion Behavior of Ethanol, Butanol,Iso-Octane, Gasoline, and Methane in a Direct-Injection Spark-Ignition Research Engine

“…This example illustrates that results should not be assumed to carry over easily to various combustion systems, and that there are difficulties in drawing general conclusions from such data in the literature, when changes in hardware and operating strategies can easily change the outcome of a particular test in practice. Other recent studies with various types of injection systems for DISI engines presented results with a diversity of gasoline= ethanol and gasoline=butanol blends but did not focus on comparing pure ethanol and butanol fuels (Aleiferis et al, 2010b;Brewster, 2007;Cairns et al, 2009;Kapus et al, 2007;Wallner et al, 2009). The optical studies of Serras-Pereira et al (2008) with ethanol and butanol DI, using early injection for homogeneous engine operation, as well as that of Smith and Sick (2007) with ethanol and iso-butanol DI, using late injection for stratified operation, provided some useful insights, but did not focus on various fuel types and strategies over a large area of low-load engine conditions.…”

Insights into Stoichiometric and Lean Combustion Phenomena of Gasoline–Butanol, Gasoline–Ethanol, Iso-Octane–Butanol, and Iso-Octane–Ethanol Blends in an Optical Spark-Ignition Engine

“…In contrast, very few alcohol-blended combustion studies have been conducted in latest technology Direct Injection Spark-Ignition (DISI) engines that are more sensitive to fuel properties than PFI engines. Wallner et al (2009) studied the combustion performance of 10% ethanol and 10% butanol addition to gasoline in a 4-cylinder DISI engine. Data were taken at engine speeds in the range 1000-4000 RPM.…”