2016 International Conference on Energy Development and Environmental Protection (EDEP 2016) ISBN: 978-1-60595-360-1 Experimental Investigation on the Stability of Hydrous Ethanol Gasoline Blends and Emission Products from SI Engine Musaab O. El-Faroug 1,2,3,a, Ma-Ji LUO 1,2,b,*, Fu-Wu YAN 1,2,c, Yun-Peng LIU 1,2,d 1 Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan 430070, China 2 Hubei Collaborative Innovation Center for Automotive Components Technology, Wuhan University of Technology, Wuhan 430070, China 3 Mechanical Engineering Department, Faculty of Engineering, Elimam Elmahdi University, Sudan a musaabgaffar@yahoo.com, b mjluo@whut.edu.cn, c yanfuwu@vip.sina.com * Corresponding author Keywords: Gasoline, Ethanol, Water, Additives, Phase separation, SI engine, Emission. Abstract. In this study, gasoline ethanol water mixtures were tested for stability, at two gasoline compositions (gasohol E10 and commercial gasoline E0) and five additives. Then, Comparative experiments were carried on a port injection gasoline engine fueled with hydrous ethanol gasoline (HE10), ethanol gasoline (E10) and commercial gasoline (E0). The effects of the engine loads and the additions of ethanol and water on exhaust emission (NOx, HC, CO 2, CO) were analyzed deeply. The experimental results showed the phase separation temperature of hydrous ethanol gasoline made up by gasohol (E10) is lower than that made up by commercial gasoline by 14 o C, at the same ethanol content and the same water content. The use of chemical additives can importantly decrease the phase separation temperature of E25 hydrous ethanol gasoline. The usage of HE10 decreased NO X, HC and CO emissions significantly at 20 N.m, 40 N.m and 60 N.m While CO 2 emissions increased for HE10. From the results, it can be decided that HE10 fuel can be considered as a possible alternative fuel for gasoline engine applications. Introduction Ethanol (C 2 H 5 OH) is the green fuel, as it is obtained from renewable energy sources. It is a colorless, volatile, flammable, transparent, neutral, oxygenated liquid hydrocarbon [1]. Ethanol has more advantages over the market gasolines: (1) Ethanol is a renewable fuel; (2) Ethanol has the high-octane number;(3) Ethanol is less toxic than gasoline;(4) Ethanol burn reduces the greenhouse-gas emissions significantly;(5) Ethanol provides more oxygen in the combustion process, which assists in complete burning and (6) reduced stoichiometric air-fuel ratio (AFR), allowing an increase of engine performance [2]. Ethanol fuel conditions all over the world conventionally prescribe the use of less than 1% water to anhydrous ethanol for gasoline blending, Hydrous ethanol, a promising additive for gasoline, can save a large consumption of energy and equipment without the further dehydration step[3, 4]. It has been suggested that 37% of the production cost is associated with water distillation and dehydration [5].
Ethanol-gasoline blends is essentially immiscible with water, while ethanol can mix in both water and gasoline due to its polar and non-polar groups [6]. Solubility of water into gasoline ethanol blends is affected by temperature, ethanol content, composition of gasoline and content of other oxygenates (additives) [7-10]. The purpose of this study is to characterize mainly the water phase stability of ethanol gasoline blends with hydrous ethanol in the amount from 20 to 40 vol%. The influence of hydrocarbon composition of gasoline and the influence of five types of additives were studied. Furthermore, compares the emission characteristics (nitrogen oxides (NOx), carbon monoxide (CO), unburned hydrocarbon (HC), and carbon dioxide (CO 2 )), of hydrous ethanol gasoline (HE10), anhydrous ethanol gasoline (E10) and pure gasoline (E0) in a port-injected gasoline engine at various load conditions. Experimental Section Mixtures Stability Materials and Instruments. 99.9% ethanol, commercial gasoline NO. 93, commercial gasohol E10, n-butanol 99.5%, isobutanol 99%, methyl tert-butyl ether, palmitic acid, sorbitan monooleate (Span80), distilled water. The instruments consisted of several tubes, 50µl micro-injector (minimum scale 1µl), 100µl micro-injector (minimum scale 2µl), 5ml sampler (minimum scale 0.2ml), 1ml sampler (minimum scale 0. 02ml), programmable temperature and humidity control box. Methods. Gasohol E10 and commercial gasoline E0 fuels are used as a reference fuel for preparation of hydrous ethanol gasoline mixtures. The mixtures prepared processing have been taking proper quantities of pure ethanol, distilled water and gasohol E10 or commercial gasoline and then placed in a test tubes and shock well. If the mixed solution is clear and transparent (described phase separation temperature of the hydrous ethanol gasoline below room temperature), then put in a mixed solution at programmable temperature and humidity control box, with an interval of 1 o C, cooling, while observing whether the solution appears cloudy stratification. If the mixed solution becomes cloudy and clarified by the stratification, the temperature recorded at this moment, is called the phase separation temperature of hydrous ethanol gasoline is the cloud point. If the mixed solution turbid stratification occurs (described phase separation temperature of the hydrous ethanol gasoline is higher than room temperature), a mixed solution of the first will be raised until the mixed solution becomes cloudy layered clear and transparent, and then the mixed solution was cooled, record the phase separation temperature of the mixed solution. Finally, five stability additives were added in different ratios and examined whether they could improve the mixture s stability, i.e. n-butanol, isobutanol, methyl tert-butyl ether, palmitic acid, sorbitan monooleate (Span80). Engine Measurements Materials and instruments. During the experiments, three different fuels were tested, which were prepared by splash blending: commercial pure gasoline which also was the base fuel (E0), (E10), i.e a mixture of 10% anhydrous ethanol-90% gasoline and HE10, i.e 10% hydrous ethanol (water content 5% by volume)-90% gasoline. The experiment was conducted on a four-cylinder, port injection, and electronic controlled automotive engine. The detailed specifications of the tested gasoline engine are listed in Table 1. The engine was loaded with
eddy current dynamometer. The exhaust gases, including NO X, CO, HC and CO 2 were measured with a gas analyzer, Model AVL Digas 4000. Methods. The tests in this experiment were conducted at speed of 1800 rpm; three loads 20, 40 and 60 Nm. The tests were repeated for three times, finally, the values of the three readings were averaged. Table 1. Main specifications of the tested engine. Cylinders Four in a row Injection type Aspirate port fuel injection Bore x stroke 75.0mm x 84.8mm Connecting road length 143.70 mm Compression ratio 10.50:1 Results and Discussion Mixtures Stability In Fig.1 a and b the resulted phase separation temperatures plots are shown for commercial gasoline E0 water ethanol mixtures and gasohol E10-water-ethanol mixtures respectively, Ethanol and water concentration in the range of 20% -40% and the water content for the same case in the range of 4% -6.5% by volume. Ambient temperature is an important factor affecting the stability of hydrous ethanol gasoline, keeping the temperature mixture high improves the compatibility of gasoline/water/ethanol mixture. Thus, a stable mixture at an elevated temperature can easily become unstable and separate from lower temperatures; while the proportion of ethanol is constant with a mixed solution of water content increases the phase separation temperature is gradually increased. As the proportion of ethanol increased with a mixed solution of water content is constant the phase separation temperature is gradually decreased. When used gasohol E10 as a reference fuel promoted more tolerance to water and helps stabilize of fuel mixtures more than used pure gasoline E0. (a) Figure 1. The phase separation temperature of the gasoline (a.commercial gasoline E0, b. gasohol E10) with 20%-40% by vol. ethanol. The use of chemical additives to prevent phase separation has been studied and successfully applied. Fig. 2 shows how n-butanol, isobutanol, methyl tert-butyl ether, palmitic acid and sorbitan monooleate (Span80) aids to further improve stability when added to the HE25 (75% gasoline and 25% hydrous ethanol (5%water content)). The results showed that five additives can reduce the phase separation temperature of the hydrous ethanol gasoline; (b)
with increasing additive content, the phase separation temperature of hydrous ethanol gasoline decreases. N-butanol and isobutanol are the best additives improved stability of mixture more than methyl tert-butyl ether, palmitic acid and sorbitan monooleate (Span80) When added 3% of n-butanol or isobutanol by volume that reduced the phase separation temperature of the mixture from 9 o C to -17 o C and -18 o C respectively. Figure 2. Effect of various additives on the phase separation temperature of the gasoline with 25vol% hydrous ethanol. Engine Measurements a) NO X emission b) HC emission c) CO emission d) CO 2 emission Figure 3. Comparison of NO X, HC, CO and CO 2 emissions for three fuels at various load conditions. For three various fuels, NOx emissions for varying engine loads at the speed of 1800 rpm are illustrated in Fig. 3.a.It can be observed that NOx emission for three fuels increases with the increasing engine load. The use of hydrous ethanol reduces the specific emissions to a
significant extend. The key is the existing water, which lowers the peak temperature during burning and slows down the procedure of NOx formation [8]. Figs.3. b depicted HC emission; it can be observed that HC emission for three fuels decreases with the increasing engine load; hydrous ethanol gasoline blends also appears to be a good choice for HC emissions reduction, probably because of lower molar C/H ratio of hydrous ethanol gasoline blend compared to gasoline. Fig.3c and d shows that hydrous ethanol gasoline blends produces higher carbon dioxide and lower carbon monoxide engineout emissions than the gasoline throughout the whole load range studied. The addition of oxygen content of ethanol improves the oxidation of CO, thereby resulting in a reduction of CO production. At all loads, CO emissions of HE10 are less than those of E10. This can be explained by the addition of water breakdown into the hydroxy radical ( OH) and the hydrogen radical ( H) promotes the oxidation of CO at high temperature conditions. In addition, according to chemical kinetics, moderate addition of water promotes the oxidation of CO on the condition of sufficient reaction [11]. Summary The chemical composition of the gasoline used is a significant factor for the stability of hydrous ethanol- gasoline blends. Hydrous ethanol gasoline made up by gasohol (E10) results in lower phase separation temperatures. Increasing the amount of the additives fraction in the gasoline-ethanol blends of known ethanol and water content decreases the phase separation temperatures of the blends. N-butanol and isobutanol as phase stability additives showed more improvement in mixture stability. NOx emissions were reduced when burning HE10 due to slower burning inside cylinder and possibly lower peak temperature during the burning procedure. HE10 also appears to be a good choice for HC emissions reduction, probably because of lower molar C/H ratio of HE10 blend compared to E0. CO emissions of HE10 are less than those of E10. The use of HE10 increases CO 2 emissions, when compared to E0 and E10 blends. Acknowledgement This work was supported by "the Fundamental Research Funds for the Central Universities (WUT: 2015III040)". Musaab O. El-Faroug acknowledges the Chinese Scholarship Council (CSC) for financial support for his PhD studies in the form of CSC grant No. 2014GF145. References [1] A. Ganguly, P. Chatterjee, A. Dey, Studies on ethanol production from water hyacinth A review, Renewable and Sustainable Energy Reviews, 16 (2012) 966-972. [2] B. Masum, H. Masjuki, M. Kalam, I.R. Fattah, S. Palash, M. Abedin, Effect of ethanol gasoline blend on NOx emission in SI engine, Renewable and Sustainable Energy Reviews, 24 (2013) 209-222. [3] I. Schifter, L. Diaz, J. Gómez, U. Gonzalez, Combustion characterization in a single cylinder engine with mid-level hydrated ethanol gasoline blended fuels, Fuel, 103 (2013) 292-298.
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