Abstract
Among the alternative fuels existing for spark-ignition engines, ethanol is considered worldwide as an important renewable fuel when mixed with pure gasoline because of its favorable physicochemical properties. An in-depth and updated investigation on the issue of CO and HC engine out emissions related to use of ethanol/gasoline fuels in spark-ignition engines is therefore necessary. Starting from our experimental studies on engine out emissions of a last generation spark-ignition engine fueled with ethanol/gasoline fuels, the aim of this new investigation is to offer a complete literature review on the present state of ethanol combustion in last generation spark-ignition engines under real working conditions to clarify the possible change in CO and HC emissions. In the first section of this paper, a comparison between physicochemical properties of ethanol and gasoline is examined to assess the practicability of using ethanol as an alternative fuel for spark-ignition engines and to investigate the effect on engine out emissions and combustion efficiency. In the next section, this article focuses on the impact of ethanol/gasoline fuels on CO and HC formation. Many studies related to combustion characteristics and exhaust emissions in spark-ignition engines fueled with ethanol/gasoline fuels are thus discussed in detail. Most of these experimental investigations conclude that the addition of ethanol with gasoline fuel mixtures can really decrease the CO and HC exhaust emissions of last generation spark-ignition engines in several operating conditions.
Highlights
Most of experimental investigations conclude that the addition of ethanol with gasoline fuel mixtures can effectively decrease HC and carbon monoxide (CO) exhaust emissions of new generation SI
The high amount of oxygen in the ethanol/gasoline blends can effectively improve the efficiency of the combustion process and involve the leaning effect in the fuelrich zones of engine, reducing CO and HC exhaust emissions
The decrease in exhaust emissions is produced by faster flame speed due to the combustion of ethanol/gasoline blend as compared to gasoline; under such operating conditions, the resulting quick and complete combustion process involves a decrease in CO and Throughout the cold-transient phase, the decrease in the CO and HC emissions compared to gasoline is significant for 20% ethanol v/v due to the rise in oxygen percentage in the gasoline/ethanol fuels, which enhances the oxidation of CO and HC, with a resulting more efficient combustion process in cold operating conditions
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In our recent studies based on experimental tests [5,27,32], CO and HC engine out emissions of a new generation four-stroke SI engine were measured in cold and hot operating conditions for several ethanol/gasoline blends Starting from such results, the aim of this new investigation is to offer a complete literature review on the present state of ethanol combustion in last generation spark-ignition engines under real working conditions to clarify the possible change in CO and HC emissions. This article focuses on the effects of ethanol/gasoline blends on CO and HC formation; numerous studies related to both combustion characteristics and exhaust emissions in spark-ignition engines fueled with ethanol/gasoline fuels are examined Most of these experimental investigations conclude that the addition of ethanol with gasoline fuel blends can decrease the HC and CO exhaust emissions of new generation SI engines. The results obtained in this research can help to guide the current research of emissions reduction systems related to use of ethanol in gasoline engines
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