Specific consumption of liquid biofuels

Fuel 87 (2008) 3362–3368

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Fuel
journal homepage: www.elsevier.com/locate/fuel

Specific consumption of liquid biofuels in gasoline fuelled engines
Renato Cataluña *, Rosângela da Silva, Eliana Weber de Menezes, Ricardo Boeira Ivanov
Department of Physical Chemistry, Institute of Chemistry, Federal University of Rio Grande do Sul, Avenida BentoGonçalves, 9500, 91501-970 Porto Alegre, RS, Brazil

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Oxygenated fuels increase fuel consumption due to their low enthalpy of combustion; however, their high antiknock index renders them suitable for use in engines with a high compression rate, increasing their thermal yield. This study evaluated the performance of biorenewable oxygenated fuels (ethanoland isoamyl alcohol) and partially renewable fuels (ETBE: ethyl tert-butyl ether, TAEE: tert-amyl ethyl ether and di-TAE: di-tert-amyl ether) with high degree of purity and in mixtures with automotive gasoline, based on tests with Otto cycle engines. Among the oxygenated fuels evaluated here, di-TAE was found to present the best characteristics of performance, both individually and in mixtureswith gasoline. Ó 2008 Elsevier Ltd. All rights reserved.

Article history: Received 11 October 2007 Received in revised form 21 March 2008 Accepted 28 April 2008 Available online 4 June 2008 Keywords: Biofuels Ethers Gasoline formulation Performance tests

1. Introduction Today, the two technically viable alternatives for reducing CO2 emissions from automotive traffic are the increase of thethermal efficiency of engines and the use of liquid biorenewable fuels [1–4]. High pressure systems for injecting fuel directly into the combustion chamber of gasoline-driven engines present good results in terms of greater thermodynamic efficiency of the thermal cycle [5–6]. The operation of gasoline-driven engines in the lean-burn region also reduces fuel consumption, but this type of solution haslimitations, since the three-way catalysts used for selective reduction of nitrogen oxides (NOx) are inefficient [7–8], allowing engines to lose power when operating in this region. Gasoline formulations with oxygenated compounds have become a common practice to improve fuel quality not only with respect to octane rating but also in terms of reduced emission of carbon monoxide (CO) and unburnedhydrocarbons (HC) [9–14]. In fact, the introduction of a minimal percentage of oxygen in gasoline formulations has become a legal requirement in most countries, which have poor air quality [15]. The use of liquid biofuels as ethanol, ethyl tert-butyl ether (ETBE), and tert-amyl ethyl ether (TAEE) with high degree of purity and in mixtures with automotive gasoline has presented good results in terms ofquality [16–18]. When incorporated into gasoline, these additives alter the physicochemical properties of density, volatility, octane rating and, especially, enthalpy of combustion. Allied to the engine type and operating conditions, these properties directly affect fuel consumption and the level of emissions.
* Corresponding author. Tel.: +55 51 3308 6306; fax: +55 51 3308 7304. E-mail address:rcv@ufrgs.br (R. Cataluña). 0016-2361/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2008.04.041

Ethanol is the biorenewable oxygenated compound most widely used in the formulation of automotive gasolines. It is currently produced by fermentation of crops high in sugar, or by a sequence of hydrolysis/fermentation steps for starch crops [19–20]. It is produced inlarge scale (Brazil and USA) and it can be easily blended with gasoline to operate in spark ignition (SI) engines. In Brazil, ethanol is used as neat ethanol in 100% alcohol-fuelled passenger cars (hydrous ethanol) or is blended (anhydrous ethanol) with all the gasoline in proportions of usually about 24% to operate in gasoline engines; or it is still used (as hydrous ethanol) in any proportion...