Energy Fuels 2010, 24, 1365–1373 Published on Web 12/30/2009
: DOI:10.1021/ef901089d
Investigation of the Characteristics of Multicomponent Biodiesel Fuel (D-FAME-E) for Practical Use in Lithuania Sergejus Lebedevas,† Galina Lebedeva,‡ Egle Sendzikiene,§ and Violeta Makareviciene*,§ ‡
† Department of Marine Engineering, Klaipeda University Maritime Institute, I. Kanto 7, LT-92123 Klaipeda, Lithuania, Computer Science Department of Faculty of Natural Sciences and Mathematics of Klaipeda University Maritime Institute, I. Kanto 7, LT-92294, Klaipeda, Lithuania, and §Laboratory of Chemical and Biochemical Research for Environmental Technology, Lithuanian University of Agriculture, Studentu 11, Akademija, LT-53361, Kaunas r. Lithuania
Received September 25, 2009. Revised Manuscript Received November 20, 2009
The results of studies into tricomponent fuel mixtures containing fossil diesel fuel (D), fatty acid methyl esters (FAME), and ethanol (E) are presented. We propose the possibility of the use of D-FAME-E in Lithuania. We determined the limits of component concentrations that make it possible to produce stable tricomponent fuel mixtures of D-FAME-E at different concentrations of ethanol (i.e., 99.8% and 96%) and at different temperatures (20, 0, and -10 °C). Engine tests were performed with fuels prepared according to these conditions. During the performance testing of 2FL511 and 1A41 diesel engines, we determined the possible influence of ethanol admixture on fuel effectiveness and emission of toxic components of exhaust gases. Admixture of ethanol increased the indicated efficiency of diesel engines by about 2% and decreased NOx emission by 5-7%. It also decreased the smoke density and increased hydrocarbon (HC) emissions. Particular alterations of fuel characteristics were experimentally fixed for fuels containing ethanol. Technological measures are suggested for the development of an efficient and stable diesel engine fleet for operation in Lithuania on tricomponent biofuel mixtures, i.e., D-FAME-E.
methyl esters of vegetable or animal origin.1,6-13 The concentration of ethanol in these mixtures varies from 5% to 20% of the mixture volume. The goal of these studies has been the evaluation of the influence of ethanol on fuel consumption and on ecological parameters of the engine, such as the emission of toxic compounds (CO, NOx, hydrocarbons (HC), smokiness) in exhaust gases. The data concerning the influence of ethanol on CO and NOx concentration are controversial.11-13 Even when the experiments are conducted using the same diesel engine under different conditions, the results obtained differ qualitatively and quantitatively. It has been observed that the usage of ethanol increases the concentration of HC in exhaust gases. The variation of the concentrations of CO, NOx, and HC in exhaust gases, and the smokiness of exhaust gases, is not linear. The best ecological parameters of diesel engines were observed when the fuel contained 10-15% ethanol. Few results concerning the influence of ethanol on indices of the indicatory process and fuel injection in the diesel engine have
1. Introduction Analysis of the potential of the raw materials available in Lithuania that are required for production of the standard rapeseed oil methyl esters (RME) suggests that fulfillment of the EU prospective norm indices may be problematic. Instead, further increase of biofuel production and use of fossil diesel fuel in Lithuania are recommended. Despite the presence of sufficient productive capacity, the main limits are related to the potential of the agricultural system, namely, the lack of growing areas and low rapeseed productivity in comparison with other EU developed countries. Because of this, the development of new kinds of biofuels is important, as is extension of the raw material base of Lithuania. A new kind of biofuels being widely used in the EU, the USA, Brazil, and other regions of the world such as China, India, Australia, and South America is a multicomponent fuel mixture of fossil fuels composed of fossil diesel fuel (D), fatty acid methyl esters (FAME), and ethanol (E).1-3 Studies have mainly focused on two-component mixtures of D and bioethanol with small quantities (1.5-2.0%) of expensive solvents or emulsifiers and on tricomponent mixtures containing fossil diesel fuel, ethanol, and fatty acid
(6) Song, C. L.; Zhou, Y. C.; Huang, R. J.; Wang, Y. Q.; Huang, Q. F.; Lu, G.; Liu, K.M. J. Hazard. Mater. 2007, 149, 355–363. (7) Shi, X.; Yu, Y.; He, H.; Shuai, S.; Wang, J.; Li, R. Fuel 2005, 84, 1543–1549. (8) Zvonov, V. A. Toxicity of the internal Combustion engine; Mashinostrojenye: Moscow, 1981;160 p. (9) Zeldovich, J. (1946) The Oxidation of Nitrogen in Combustion and Explosions. Acta Physiochim. URSS 1946, 21, 577–628. (10) Kumar, M. S.; Kerihuel, A.; Bellettre, J.; Tazerout, M. Fuel 2006, 85, 2646–2652. (11) Chen, H.; Wang, J.; Shuai, S.; Chen, W. Fuel 2008, 87, 3462– 3468. (12) He, B. Q.; Shuai, S. J.; Wang, J. X.; Hong, He Atmos. Environ. 2003, 37, 4965–4971. (13) Choi, C. Y.; Bower, G. R.; Retiz, R. D. Effects of Biodiesel Blended Fuels and Multiple Injections on D.I. Diesel Engine Emissions; SAE Paper No. 970218, 1997; 388-407.
*To whom correspondence should be addressed. Address: Lithuanian University of Agriculture, Studentu 11, LT-53361, Akademija, Kaunas r., Lithuania. Phone/Fax: þ370 37 75 22 92. E-mail:
[email protected]. (1) Kwanchareon, P.; Luengnaruemitchai, A.; Jai-In, S. Fuel 2007, 86, 1053–1061. (2) Nguyen, D.; Honnery, D. Fuel 2008, 87, 232–243. (3) Hansen, A.; Zhang, Q.; Lyne, P. W. Bioresour. Technol. 2005, 96, 277–285. (4) L€ u Xing-cai, L.; Jian-guang, Y.; Wu-gao, Z.; Zhen, H. Fuel 2004, 83, 2013–2020. (5) Li, X.; Qiao, X.; Zhang, L.; Fang, J.; Huang, Z.; Xia, H. Renewable Energy 2005, 30, 2075–2084. r 2009 American Chemical Society
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been reported. Such experiments are important for the development of fuel containing ethanol for utilization in diesel engines. For this reason, thorough investigations of diesel engines working with fuel containing ethanol need to be performed. One such study is being carried out as collaboration between the scientists of the Lithuanian University of Agriculture (LUA) and the Klaipeda University Maritime Institute (KUMI). In this article, we present the results of studies conducted during 2008 and 2009. These studies sought to investigate the concentration limits of ethanol (E) in the multicomponent biofuel D-FAME-E and to evaluate the potential for its further use in Lithuania. First, we demonstrate a high level of performance for diesel engines running on two-component rapeseed oil methyl esters (RME)-E mixtures, where the portion of E was increased up to 40%.16 For our studies on the tricomponent diesel fuel D-FAME-E, the following problems were addressed: Determination of the properties of the diesel fuel prepared with a wide range of D, FAME, and E component concentrations (density, viscosity, cetane number, calorific value, etc.) and evaluation of its conformity to the currently enforced standards. Examination of the diesel fuels’ operating characteristics (solubility and stability of the mixtures depending on the quality of ethanol and the temperature of the biofuel, combustibility, etc.) and determination of the optimal fuel composition on engine tests. Examination of engine performance (fuel operating economy, ecological indices and diesel engine tractive characteristics) in order to generate practical recommendations for D-FAME-E application.
Table 1. Main Technical Parameters of Diesel Engines F2L511 and 1A41 parameter cylinder diameter, m piston stroke length S, m engine displacement Vh, dm3 compression ratio ε rated output Penom, kW rated break mean effective (indicated) pressure pme (pmi), MPa rated speed, rpm fuel injection type of combustion chamber
F2L511
1A41
0.10 0.105 1.65 17 25.7 0.62
0.13 0.14 1.115 16 14 (0.85)
3000 direct open
1750 direct open
The biofuel tests were carried using two different diesel engines (lA41 and F2L511) in order to determine the generality of the results and to develop practical recommendations for use. The high speed naturally aspirated F2L511 diesel engine (made by JSC “Oruva ir Ko”, Mazeikiai, Lithuania) and the single cylinder section 1A41 of diesel engine A41 (made by JSC “Altaiskij motornij zavod”, Barnaul, Russian Federation) were tested on an engine test bed. These engines were chosen as typical models used for agricultural purposes in Lithuania. The results of these studies can be used for preliminary evaluation of the expected efficiency of fuel mixtures containing ethanol that may replace fossil diesel fuel. Recommendations based on the results described herein may be made not only for the abovementioned diesel engines but also for other types of diesel engines in Lithuania.18 The main parameters of the tested diesel engines are given in Table 1. Testing on engine 1A41 was carried out when the diesel engine was running at the rated speed of 1750 rpm within the load range (Pmi; brake mean indicated pressure) from 0.25 to 0.85 MPa. The types of tested fuels are as follows: fossil diesel fuel (D) and tricomponent mixtures D25/RME55/E20 and D15/RME55/E30. For these tests, ethanol was used at a concentration of 96%. Tests were carried out during the summer period, when the ambient temperature was from þ5 °C to þ8 °C. The temperature of the components in the fuel mixture preparation was from 0 °C to þ5 °C. During the experiments, due to heating of the walls of the fuel feeding aggregates, the fuel temperature increased to þ30-40 °C. The engine 1A41 tests were performed on a certified motor stand that was equipped with an electric brake, automatic fuel consumption gauge, and pressure and temperature sensors in the cooling and lubricating oil systems. The emission of exhaust gases containing harmful components was measured with a “Quintox 9106” automatic gas analyzer. In all tested diesel engine running regimes, an H-2000 digital station and a sensor set to indicate pressure with a needle on a fuel injector nozzle were used to measure the fuel pressure in a high pressure fuel line, the gases in the diesel engine cylinder, and the actual angles at the start and end of fuel injection. The data were averaged over 30-100 subsequent diesel engine running cycles. Experimental analyses of motor characteristics were made on a certified stand that was supported by modern automated measuring and registration devices to determine the technical and economical (fuel consumption, temperature of exhaust gases, etc.) parameters of emission of harmful components in exhaust gases.
2. Materials and Methods 2.1. Materials. Ethanol (E) was obtained from Sigma Co. Rapeseed oil methyl esters (RME) and pork lard methyl esters (PME) were produced by the alkali-catalyzed two step transesterification process of refined rapeseed oil, and pork lard was purchased from a local market. The quality characteristics of these products met the requirements of European Norm EN 14214 Automotive fuels, Fatty acid methyl esters (FAME) for diesel engines, Requirements and test methods. The RME content in the product was more than 98.7%; the PME content was more than 96.8%. The quality of the fossil diesel fuel (D) met the requirements of European Norm EN 590 Automotive fuels, Diesel, Requirements and test methods. Composition was alcanes, 42%; cycloalcanes, 35%; aromatic hydrocarbons, 23%. 2.2. Methods. The solubility of the tricomponent fuel mixtures was determined by turbidimetric analysis at isothermal conditions.17 The mixture of two components was placed in the cell of a spectrophotometer equipped with a magnetic stirrer and titrated by a third component while the absorbance was measured at a wavelength of 590 nm. Formation of an emulsion indicated a significant rise of absorption. The obtained results are presented in phase equilibrium diagrams using classical methods. (14) Satge de Caro, P.; Mouloungui, Z.; Vaitilingom, G.; Berge, J. Ch. Fuel 2001, 80, 565–574. (15) Rakopoulos, D. C.; Rakopoulos, C. D.; Giakoumis, E. G.; Papagiannakis, R. G.; Kyritsis, D. C. Fuel 2008, 87, 1478–1491. (16) Lebedevas, S.; Lebedeva, G. Expansion of the Biodiesels Nomenclature in Transport Sector of Lithuania at the Expense of Blended Alcohol Fuels Use. Proceedings of the International Conference on Transport Means; Technologija: Kaunas, 2008; pp 71-74. (17) Komers, K.; Tichy, J.; Skopal, F. J. Prakt. Chem. 1995, 337, 328– 331.
(18) Lebedevas, S.; Vaicekauskas, A.; Lebedeva, G.; Makarevicien_e, V.; Janulis, P. Energy Fuels 2007, 21, 3010–3016.
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Table 2. Accuracy of Measurement of Engine Parameters for 1A41 and F2L511 Diesel Engines accuracy of parameters recording parameter
1A41
F2L511
torque, N 3 m diesel speed, rpm rated brake mean indicated pressure, MPa liquid temperature in cooling and lubricating oil systems, °C Liquid pressure in a cooling and lubricating oil systems, bar fuel specific consumption, g/kW 3 h fuel pressure in a high pressure fuel line, MPa fuel injection start angle, crank angle (CA) degree fuel injection end angle, crank angle (CA) degree cylinder pressure, bar CO exhaust emission, ppm NOx exhaust emission, ppm HC exhaust emission, ppm Bosch index
(0.5% (0.5% (1.0% (2 °C (1% (0.5% (1% (0.5°CA (0.5°CA (1% (5% (5%
(0.5% (10 rpm (0.5% (2 °C (2 °C (0.5%
(0.1 unit
In order to guarantee that the testing conditions correspond to the real operational conditions of diesel engines, the analyses were made while the F2L511 engine was running at a wide range of loads (mean effective pressure Pme= 0.2-0.7 MPa) and rotation speeds (n = 3000 min-1). To regulate the load, we used a hydraulic brake (Z€ ollner 20LLNE3N19A) controlled by a computer (FIPS-S486/66FTFT-635-ES/AT-08-4SER/TM-PLU). The fuel consumption was measured by a fuel feeding rate gauge (PLU 401-115W/116HR). The emissions in the exhaust gases were measured by an analyzer (MIR 9000) designed to continuously register the harmful components of exhaust gases using the method of infrared absorption spectroscopy and gas filter correlation. The concentrations of carbon dioxide (CO2), carbon monoxide, nitrogen monoxide (NO), and hydrocarbons (HC) were measured. The smoke opacity of exhaust gases was measured by a Bosch analyzer. The types of tested fuels were as follows: fossil diesel fuel (D), B30 (D70/KME30), and tricomponent fuel mixtures (D70/KME30)95/E5, (D70/KME30)90/E10, (D90/KME10)95/E5, (D80/KME20)95/E5, and (D80/RME20)95/E5. Pure 99.8% ethanol was used for all preparations. Pork lard methyl esters (PME) were used to evaluate the possibility of increasing the basis of raw materials for biodiesel fuel production. The results were compared with those of tests performed with the above-mentioned tricomponent mixtures (D25/RME55/ E2O and D15/RME55/E30). The ethanol concentration in these mixtures was 96%. Testing of diesel engine 2FL511 was carried out with a constant rpm of 2800. Break mean effective pressure limits, Pme, varied from 0.3 MPa up to the nominal value of 0.6 MPa. Testing was carried out during summer, when the ambient temperature was 25-30 °C. The temperature of the biofuels after preparation and during testing was 20 °C. The accuracy of the measurements of the 1A41 and F2L511 diesel engine parameters during tests is given in Table 2
(30 ppm (0.5% (20 ppm (0.1 unit
Figure 1. Isotherms of solubility of the D-E-RME system at 20 °C when the ethanol concentration = b, 99.8%; 9, 98.5%; 2, 94%.
3.1. Tricomponent Fuel D-RME-E Properties. Studies of the tricomponent fuel mixtures were performed to evaluate their usefulness in diesel engines. The above-mentioned biofuels contain fossil diesel fuel (D), rapeseed oil methyl esters (RME), and ethanol (E). The intersolubility of the components and the stability of the mixtures of D-RME-E were determined depending on the components’ concentration, quality (i.e., concentration of ethanol), and the temperature of the mixture. In Figure 1, isotherms of the solubility of the tricomponent mixtures at 20 °C are presented. A soluble mixture is formed when the concentration of the components (described by the section of triangle) sits above the isotherm. According to our data, the solubility of the mixture significantly depends on the concentration of E. When the concentration of ethanol is decreased, the section of the triangle corresponding to the solubility of mixture is also decreased. A positive influence of RME admixture on the solubility of E in fossil diesel fuel can be observed when the concentration of ethanol is 99.8% and the ratio of RME and D is less than 2:8. The solubility of E in the tricomponent mixture is significantly limited. Admixture of ethanol into a stable solution could not exceed 5%. Mixtures were also stable when the proportion of ethanol was too large, i.e., more than 90%. However, results of previous studies demonstrate that such biofuels cannot be used practically.19
3. Results and Discussions The aim of experiments was to evaluate the possibilities to use bioethanol containing fuel mixtures in diesel engines. In this chapter, the following research results are presented (1) data about solubility of tricomponent fuel mixtures D-FAME-E and quality parameters of stable fuel mixtures containing ethanol and (2) data about influence on ethanol concentration in fuel mixtures on diesel engine performance and ecological indices.
(19) Sendzikiene, E.; Makareviciene, V.; Janulis, P. Renewable Energy 2006, 31, 2505–2512.
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Because of this, we varied the concentration of ethanol in our tests from 4.7% to 28% in bulk in order to evaluate influence of ethanol on the technical, economical, and ecological indices of diesel engines. The composition of the fuels tested is given in Table 4. Mixtures were chosen where the portion of fossil diesel fuel was varied from 15.2% up to 66.2%, but the portion of RME or FAME was varied from 26.3% up to 56.8%, i.e., over a sufficiently wide range of concentrations. Furthermore, some tests were performed with 96% ethanol in order to evaluate the possibility of the use of lower concentrations of ethanol in diesel engines. Mixtures that were stable at 0 °C could be produced when the concentration of absolute ethanol did not exceed 5%. Therefore, such a biofuel could be used by a diesel engine in the summer time. At the same time, at -10 °C, all the tests indicated instability of the tricomponent mixtures, and these mixtures are, therefore, not suitable during the winter period. We next sought to identify additives such as depressants that could lower the CFPP (cold filter plugging point) of such mixtures and the solubility of its components as well. The parameters of tricomponent mixtures used for engine tests are given in Table 4. Demands of European Standard EN 590, which concerns the quality of fossil diesel fuel, are also given. The data demonstrate that quality indices of nearly all investigated tricomponent mixtures conform to the demands of the standard. The cetane number of the mixtures is under the standard level since the cetane number of ethanol is significantly less in comparison with fossil diesel fuel. Ash content exceeded the acceptable norm but conformed with standard EN14214 for biofuels. The maximum acceptable norm is 0.02%. 3.2. Operating Characteristics of Diesel Biofuel (B30) with 5-10% of E. During testing of tricomponent biofuels, a two-component mixture of fossil diesel fuel containing 30% (vol) of pork lard methyl esters (PME) was prepared with 5-10% pure 99.8% ethanol. Diesel biofuel B30 was chosen for testing based on results of its performance in complex diesel engine tests.20 It was determined that application of a 30% bulk volume concentration of FAME mixed with fossil diesel fuel resulted in the best compromise with respect to diesel engine indices of fuel conservation and improvement of ecological indices. Mechanical and thermal load indices of diesel engines running on the biofuel mixture did not exceed the loads observed while running on fossil diesel fuel. For this reason, we did not need to change the control parameters for the diesel engines or the fuel injection system. Fuel Consumption Indices. Admixture of 5% and 10% ethanol to biofuel B(B30(PME)95/E5) or B(B30(PME) 90/ E10) increased fuel consumption, which resulted in an equal output of the diesel engine due to the lower heat caloric value of ethanol, Hu (see Table 4). An increase of the efficiency of specific fuel consumption be in the main range of Pme averaged l% when 5% ethanol was added and no more than 2% when 10% ethanol was added (see Figure 2). At the same time, ethanol improved the combustion process characteristics and promoted an increase in the index of efficiency of heat fuel combustion when converted into mechanical work in the cylinder; i.e., it increased the
Table 3. Minimum Quantity of RME in Stable Tri-Component Solutions at Temperatures 20, 0, and -10°C RME, % ethanol, %
þ20 °C
0 °C
-10 °C
5 10 15 20 30 5a 10a 15a 20a 30a
9 12 15 16 18 29 46 48 47 44
20 29 31 32 29 42 60 64 63 58
65 67 64 58 57 88 95 93 89 86
a
Mixtures with 96% ethanol.
Any quantity of absolute ethanol can be dissolved into mixtures of RME and D where the ratio of the concentration of components is 3:7 or more. At the same time, the limits of solubility of D-RME-E tricomponent mixtures were significantly reduced when 94% ethanol was used. At 20 °C, stable solutions of D-RME-E could be obtained with an E concentration of 10% or more and a large quantity RME in the mixture; i.e., the RME-D ratio needed to be 7.5:2.5 or higher. These mixed biofuels with such large contents of RME are potentially useful because they contain a significant portion of renewable components. However, currently the RME portion mixed with fossil diesel fuel cannot exceed 5% in most EU countries, not including the Czech Republic and Poland, where admixture of up to 30% RME is allowed. It was impossible to obtain tricomponent soluble mixtures with such a quantity of RME mixed with 94% ethanol. For internal combustion engines, low temperature fuel properties are very important and are characterized by the clouding temperature and the cold filter plugging point (CFFP). In Lithuania, fuels with a CFFP no higher than þ5 °C in the summer, -15 °C in the transition period, and -32 °C in the winter are allowed. Studies were performed to assess the stability of tricomponent mixtures with components of absolute and 96% ethanol with respect to temperature. Tests were conducted at 20, 0, and -10 °C in order to allow for a detailed evaluation of the possibility of the use of tricomponent mixtures of D-RME-E in diesel engines. The results are given in Table 3. The results show that the limits of solubility of tricomponent mixtures were narrowed when the temperature of the mixture was lowered. At 20 °C, stable solutions could be obtained when the E concentration was 30% and the quantity of RME was no less than 18%. At -10 °C, such solutions were stable when the portion of RME in the mixture was much higher, i.e., 57-67% depending on portion of ethanol. A higher quantity of RME was necessary to stabilize tricomponent mixtures of D-RME-E when a lower concentration of ethanol was used. The solution was stable when 96% ethanol was used at 20 °C, or when the concentration of ethanol was up to 30% and the concentration of RME was 29-48%. At -10 °C, the portion of RME needed to be at least 86-95%. As a result, the portion of fossil diesel fuel required for a stable soluble mixture is rather insignificant. The results of preliminary studies demonstrate that stable work of the diesel engine is determined by the portion of oxygen in tricomponent mixtures. Either this cannot not exceed 19.5% or the portion of E must be less than 46%.19
(20) Lebedevas, S.; Vaicekauskas, A.; Lebedeva, G.; Janulis, P.; Makarevichien_e, V. Research of operational parameters of diesel engines running on RME biodiesel. Transport 2006, 4, 260–268.
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Table 4. Composition and Physicochemical Characteristics of the Tested Multi-Component Fuel fuel composition (D-E-RME(PME), % characteristic density, kg/m3 (15 °C) viscosity, mm2/s 40 °C cetane number flash point, °C ash content, % mass sulfur content, mg/kg calorific value, Hu MJ/kg copper plate corrosion (3 h. at 50 °C) a
EN 590 limit values 820-845 2.00-4.50 g51 g55 e0.01 e50
No 1 66.2-4.7-29.1a
No 2 63.1-9.3-27.6a
No 3 59.7-14.0-26.3a
No 4 25-18.6-56.4b
No 5 15.2-28-56.8b
842 3.01 48 85 0.011 25 41.2
838 2.89 46 80 0.014 24 40.5
835 2.78 43 75 0.015 22 39.7 1
850 3.04 44 94 0.018 13 37.4
846 2.84 42 88 0.018 9 35.9
rating
Fuel mixtures containing PME. b Fuel mixtures containing 96% ethanol.
Figure 3. Operating indices of diesel engine F2L511 while running on D-PME-E biofuel.
Figure 2. Diesel engine F2L511 fuel effectiveness while running on fuels D-PME-E.
indicated efficiency of the engine cycle (ηi).4,5 Analogous results were obtained in our study: admixture of 5% ethanol increased η (Δηi) up to 1% in the diesel engine rated power regime. However, in the case of 10% of ethanol, the increase was 1 to 2% within the range of Pme values considered (see Figure 3). The alteration of diesel engine performance indices when ethanol was added fully confirmed the above-mentioned improvement of ηi (see Figure 4). The excess air coefficient R, which directly influences fuel combustion characteristics, increased insignificantly within the range of Pme values studied; i.e., the increase for 5% E was 2-3% and 4-10% for 10% E. The larger values are characteristic for minor loads. An increase of R confirms the fact that equality of diesel engine power results in a smaller increase of fuel feed for fuel containing E compared to the decrease of the heat value of biofuel after ethanol addition. The decrease of the temperature of diesel engine exhaust gases (Tg) when ethanol was added to diesel biofuel B30 indirectly demonstrates the improvement of heat utilization indices: an increase in the heat portion of fuel combustion that is converted into useful effective work. Tg values decreased on average by 5-7 °C
Figure 4. Influence of D-PME-E biofuels on the indicated efficiency of diesel engine F2L511.
and 10-15 °C, when 5% and 10% ethanol were added, respectively (see Figure 4). The results allowed us to evaluate the influence of ethanol admixture on diesel biofuel, which influences diesel engine characteristics. The expectation of a decrease in diesel engine 1369
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Figure 5. Ecological indices of diesel engine F2L511 while running on D-PME-E biofuels.
rated power without alteration of the high pressure fuel pump control parameters in proportion to the increase of be and does not exceed 2%. On partial loads, when Pme values are equal, the specific fuel consumption be will increase. Thus, admixture of 5-10% ethanol to diesel biofuel will not significantly influence the tractive characteristics of the diesel engine. Ecological Indices. Unlike the similar evaluations of the influence of ethanol on be and η, contradictory results have been published with respect to the influence of ethanol diesel engine ecological indices.1,6,8,9 Therefore, we performed studies of emissions of toxic components (NOx, CO, and HC concentrations in exhaust gases and the smoke density of exhaust gases). Toxic ejections of exhaust gases were continuously recorded with consequent averaging of 5-10 readings after the diesel engine’s operational regime was stabilized. The analysis was performed using measurements that comply with current standards. Smoke density of exhaust gases. Admixture of 5-10% E did not influence smoke density within the range of Pme values studies (see Figure 5). CO emissions, in comparison with B30, did not change with changes in power of the engine. Taking into consideration the lower level of eco, which is equal to about 2 g/kWh, a decrease of Pme caused an insignificant increase of CO emissions by 10-15% when 10% E was added (see Figure 5). Admixture of 5% E did not influence CO emissions. NOx emissions did not change when ethanol was added, and this is consistent with what is known about the physical processes of CO and NOx formation in the cylinder of a diesel engine, which are principally different.8-10 When an engine runs on the same fuel, an increase or decrease of CO emissions is typically accompanied by an opposite decrease or increase of NOx emissions and this is stipulated by alteration of control parameters.10 When a diesel engine runs on biofuels B30 or B30 with 5% E, values of eNOx are identical over the whole range of Pme values. When diesel biofuel is prepared with 10% E (e.g., biofuel B30, which contains FAME90/E10), on average loads, the NOx emission values tend to increase by 5-10% compared to when the engine runs on pure B30. Therefore, taking into consideration the above-mentioned changes of diesel engine R and Tg, one may conclude that admixture of 5-10% E to biofuel
B30 influences the ecological indices of the diesel engine. This occurs mostly by means of phasic changes in parameters of the fuel injection process and through the process of heat release. Because of this alteration of the fuel feed control parameters, running an engine on biofuels with added ethanol can be considered one of many technical means by which the ecological indices of a diesel engine can be influenced. Combustion of biofuels with 10% E was accompanied by an increase of HC emissions of about 7-15% (see Figure 3), consistent with results reported in the literature.11-13 Admixture of 5% E did not influence eHC values. Thus, admixture of 5-10% E to biofuel B30, which is formulated on the basis of FAME, did not significantly influence the ecological indices or the tractive characteristics of the diesel engine when operating as a drive or power consumption object. At the same time, improvement of power consumption indices, i.e., the efficiency of the cycle was 1 to 2%. An increase in ethanol concentration causes an increase in ηi. 3.3. Influence of FAME Portion on Engine Performances of D-PME-E Biofuel. In order to determine the generality of our results, tests were performed with the experimental biofuel D-PME-E and the standardized biofuel RME. The use of 99.8% absolute ethanol and also thermal conditions (þ20 °C) allowed us to determine the influence of the proportion of FAME on biofuel D-FAME-E when the concentration of FAME was reduced to 10%. Fuel Consumption Indices. A decrease of the proportion of FAME in the tricomponent biofuel D-FAME-E from 30% to 10% significantly improved the fuel efficiency indices. A decrease of FAME to 10% when the concentration of E was 5% increased the efficient specific fuel consumption be by 4-6%, which demonstrates its identity to fossil diesel fuel (see Figure 6). Each 10% decrease of FAME concentration in the range of Pme = 0.3-0.6 MPa resulted in decreases in be by about l.5% on an average. When all versions of the tricomponent biofuels were tested, the results indicated that the efficiency ηi of the diesel engine was higher than when mineral diesel fuel was used. The best results, namely, an increase of ηi by 3%, were obtained within the range of loads when the concentration of FAME was the least, i.e., B(B10(PME)95/E5) (see Figure 7). 1370
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: DOI:10.1021/ef901089d
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volumetric atomization of fuel without air charge motion into the cylinder. Direct injection of fuel is realized by means of an injector through its four jet orifices of D = 0.25 mm. Compared with current types of high speed diesel engines that have a cylinder diameter of 150 mm, the pump fuel feed pressure is realized by means of an in-line plunger pump. The A41 diesel engine is not high on the rated power regime, having no more than 55-56 MPa. This is further decreased to 25-30 MPa on partial loads of the diesel engine together with the initial phase of fuel feed static beginning, which is realized by means of a high pressure fuel pump, i.e., 28-30°crank angle degree (°CA) before top dead center. These factors stipulate high dynamic characteristics for the indicated process, i. e., λ, dp/dj max, making it very sensitive to fuels with a low cetane number.14,21 The low cetane number of E and a sufficient concentration of E (20-30%) in D-RME-E stipulate the testing on a single cylinder block of diesel engine 1A41. Tests were performed using the biofuels D25/RME55/E20 and D15/ RME55/E3O with 20% and 30% ethanol in the mixture. Fuel Consumption Indices. An increase of ethanol concentration from 20% to 30% caused an increase of be by about l.5% within the studied range of mean indicated pressure, Pmi = 0.4-0.8 MPa (see Table 5). The indicated efficiency increased by about 1.5-20%. The variations of R and Tg indirectly confirm the improvement of heat consumption when the portion of E in the fuel is increased. The result with respect to the influence of the portion E on be and ηi is consistent with results of tests with biofuels containing 5-10% E (see section 3.2). Ecological Indices. Increase of the concentration of E in the biofuel to 10% did not significantly influence emissions of NOx or CO (see Figure 9). The decrease of smoke density was 0.2-0.25 Bosh units. At the same time, unlike the results of tests with biofuels containing 5-10% E, the use of diesel engine F2L511 demonstrated a significant improvement of ecological indices compared with fossil diesel fuel. We observed a 3-fold decrease of smoke density (from about 2.5 Bosh units to 0.7-0.5 Bosh units for Pminom), a decrease of eCO by 30-40% on rated loads, and a 2-fold decrease in emissions of NOx on a partial load, which had an identical level on a rated load, i.e., Penom, compared with D. Significant improvements of diesel engine ecological indices compared with the use of D were connected with the sufficient portion of oxygen-containing components, i.e., the total portion of RME and E in the biofuels tested, 70% and 80%, respectively. At the same time, the influence of E on emissions of NOx was practically the same and did not depend on the value of the proportion of E. Indices of Fuel Injection and Indicated Process. For RME-E16 testing, the portion of E increased from 10% to 40% of the volume. Similar studies have reported that a small portion of E (5%, 10%, 15%) causes a decrease of the crank angle by about 2°, i.e., a decrease of the real injection phase of injection timing on partial loads of the diesel engine.15 At the same time, the maximum fuel feed pressure into a high pressure line is significantly higher on partial loads when the diesel engine is operating on E than when it is operating on D and FAME.22 On a rated power regime, the
Figure 6. Influence of FAME concentration in the biofuel D-FAME-E on specific fuel consumption in the diesel engine F2L511.
Figure 7. Influence of FAME concentration in D-PME-E biofuel on the indicated efficiency of diesel engine F2L511.
Therefore, to obtain the best indices of fuel effectiveness, the portion of FAME in the tricomponent biofuel should be decreased to the lowest values that allow the intersolubility of systems, taking into consideration the quality of D and the thermal operating conditions of the diesel engine. Ecological Indices. When the portion of FAME in diesel biofuel was decreased from 30% to 10%, the HC emission increased on partial loads. The same result was observed for CO emission and smoke density of exhaust gases when the load increased by 25-30% and was observed (see Figure 8). This result was expected since decreasing the FAME portion while the portion of E is fixed tends to decrease the total concentration of oxygen-containing components in the biofuel and, consequently, to worsen the ecological indices. Thus, the use of rather small concentrations of ethanol (5-10%) produces the best results with respect to fuel effectiveness. While the portion of E was increased, a decrease in the portion of FAME guaranteed the intersolubility of components. To decrease the emissions of toxic components and smoke density of the exhaust gases, the portion of oxygen-containing components, especially the portion of FAME, in the fuel should be increased. 3.4. Engine Performances of D-RME-E Biofuel When the Portion of E is 20-30%. Diesel engine 1A41 was chosen for testing because of the parameters of its design. Diesel engines of the A41 series, designed in 1970s, in the last century, have
(21) Portnov, D. A. Turbo-piston high-speed compression-ignition engines; Mashinostrojenye: Moscow, 1963; 638 p. (22) Gershman, I. I.; Lebedinskij, A. P. Multifuel diesels; Mashinostrojenye: Moscow, 1971; 221 p.
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: DOI:10.1021/ef901089d
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Figure 8. Influence of FAME concentration in D-FAME-E biofuel on ecological indices of diesel engine F2L511. Table 5. Influence of 10% Increase of Ethanol into a D-FAME-E Mixture on Diesel Engine 1A41 Parametersa ηi
be, g/kW 3 h Pmi, MPa
I
0.39 0.50 0.59 0.69 0.80
775 475 394 348 327
a
II 477 406 350 337
R
tg,° C
eNOx, g/ kW 3 h
Δbe, %
I
II
Δηi, %
I
II
ΔR*
I
II
Δtg°, C
þ0.5 þ3 þ0.6 þ3.1
0.519 0.505 0.487 0.481 0.47
0.530 0.511 0.494 0.50 0.476
þ2.1 þ1.2 þ1.4 þ4.0 þ1.3
4.11 3.13 2.49 2.07 1.76
4.23 3.11 2.52 2.15 1.77
þ0.12 -0.02 þ0.03 þ0.08 þ0.01
250 310 380 430 470
250 310 370 410 470
0 0 -10 -20 0
I
II
3.7 3.6 4.4 4.0 5.2 5.1 7.7 1.1 10.6
eCO, g/ kW 3 h
ΔeNOx, %
I
-2.7 -10 -1.9
5.2 3.8 2.8 2.0 2.4
-3.6
II 4.1 3.0 1.8 2.3
SM, Bosch index
ΔeCO, %
I
II
ΔSM, %
þ7.9 þ7.1 -10 -4.2
0.7 0.9 1.1 0.9 0.8
0.5 0.7 1.0 0.6 0.7
-29 -23 -10 -33 -13
I, RME55/E20/D25; II, RME55/E30/D15
a high pressure line as E is evaporated. This in turn disturbs continuity of fuel flow and increases compressibility, causing a delay at the beginning of fuel feed. The cavities collapse when the next injection begins and can cause so-called water hammering, consequently leading to an increase of pressure in the high pressure line on partial loads. Analogous demonstrations of significant improvement of the indices studied here related to exhaust gas toxicity when ethanol is added to diesel biofuel have been reported by authors testing RME-E16 (Figure 10). When tricomponent fuel contained 10% of ethanol, maximum fuel feed pressure increased by ∼9% from 50 to 54.5 MPa. Real fuel injection angle determined from the beginning of injector needle rise hf (see Figure 10) decreased by ∼2°CA. As a result, ∼2°CA decreased the fuel burning beginning phase and gas pressure in a cylinder. Therefore, we recommend an increase of the residual fuel pressure into the high pressure line when the diesel engine fleet is converted to operate on alcohol-containing fuels. Our results demonstrate that purposeful alteration of the fuel feed timing phase is an effective method for improvement of the ecological indices of diesel engines running on biofuels.20 Figure 9. Ecological indices of diesel engine 1A41 while running on biofuels D-RME-E containing 20-30% E.
4. Conclusions One possible way to use ethanol as a fuel for diesel engines is to incorporate this component into fuel mixtures containing fossil diesel fuel and fatty acid methyl esters. The proportion of ethanol in D-FAME-E mixtures is limited and depends on the concentration of ethanol, temperature, and the ratio of D and FAME in the mixture. At 20 °C, stable solutions can be
spontaneous change in fuel feed does not occur. The fuel feed phase lag can be explained by the high pressure of saturated alcohol vapor compared with D and RME. At the moment of discharge of the high pressure line after the next fuel injection, the vapor locks (vacuum cavities) are formed into 1372
Energy Fuels 2010, 24, 1365–1373
: DOI:10.1021/ef901089d
Lebedevas et al.
and 26.3-56.8% FAME were performed. The results of engine performance tests in diesel engines F2L511 and 1A41 demonstrate the improvement of the operating characteristics when ethanol concentrations up to 30% are used in tricomponent D-FAME-E biofuels. An approximately proportional improvement of D-FAME-E biofuel effectiveness and a decrease of toxic emissions were observed when absolute 99.8% alcohol or 96% alcohol was used. Each 10% increase of ethanol concentration in the D-FAME-E mixture caused an increase of the effective specific fuel consumption be. This increase did not exceed 2%, but an increase of the indicated efficiency η was about 2% within a wide range of loads. Admixture of ethanol does not have a negative effect on the tractive characteristics of the diesel engine. Ecological indices were not significantly altered, including the trend of decreased NOx emission by 5-7%, decreased smoke density, and the trend of increased HC emission. To increase the fuel effectiveness of the diesel engine, the FAME portion should be decreased to the limits of intersolubility of the D-FAME-E system. The quality of E and the diesel engine’s operating thermal conditions must be taken into consideration. A decrease of the proportion of FAME by 10% improved be and ηi by approximately 1.5% and 1%. The ecological indices of CO, NOx, HC, and smoke density are determined by the total portion of oxygen-containing components of FAME and E.When out-of-date diesel engines are converted to run on D-FAME-E biodiesel fuel, the fuel feed systems should be modernized to increase the residual pressure in high pressure lines. The possibility of corrosion and troubles in fuel injection system functionality when fuel contains 96% ethanol requires further investigation and discovering possible solutions to apply possible technical measures.
Figure 10. Lag of phase of diesel engine 1A41 injection timing while running on biofuels that contain ethanol (Pmi = 0.8 MPa).
obtained with an E concentration of 30% when the quantity of RME is no less than 18% in the mixture. When 96% ethanol is used at 20 °C, the solution is stable at ethanol concentrations up to 30% and a proportion of RME in the range 29-48%. Lowering the temperature decreases the ethanol concentration in stable fuel mixtures. In order to evaluate the influence of ethanol on engine performance characteristics and emissions of harmful components in exhaust gases, engine tests of stable tricomponent mixtures containing 4.7-28% ethanol, 15.2-66.2% fossil diesel fuel,
Acknowledgment. Authors sincerely appreciate the assistance of the Agency for the Development of International Science and Technology.
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