Energy Fuels 2010, 24, 1822–1828 Published on Web 02/23/2010
: DOI:10.1021/ef901306z
Study of the Performance and Emissions of the Compression-Ignition (CI) Engine Using Ethyl Acetate as a Surfactant in Ethanol-Based Emulsified Fuel M. P. Ashok* Department of Mechanical Engineering, Faculty of Engineering and Technology, Annamalai University, Annamalai Nagar 608002, Tamil Nadu, India Received November 6, 2009. Revised Manuscript Received January 20, 2010
In this research work, emulsified fuel has been prepared with the help of ethyl acetate as a surfactant and its performance and emission characteristics have been compared to diesel fuel number 2. The best emulsified fuel ratio [50% diesel and 50% ethanol (50D/50E), 100% proof] has been used in this work. A water-in-oiltype emulsion method has been used in the preparation of the emulsified fuel. It has been tested with a fourstroke, water-cooled, single-cylinder, compression-ignition (CI) diesel engine. The entire experiment has been carried out at a constant speed of 1500 revolutions/min. In comparison to diesel fuel, emulsified fuel is found to increase brake thermal efficiency and oxides of nitrogen and decrease specific fuel consumption, particulate matter, hydrocarbons, and carbon monoxide.
diesel fuel results in different physicochemical changes in diesel fuel properties, particularly a reduction in the cetane number, viscosity, and heating value.4 Therefore, different techniques involving ethanol-diesel fuel operation have been developed to make the diesel engine technology compatible with the properties of ethanol-based fuels. The best emulsified fuel ratio 50D/50E has been prepared on the basis of the water-in-oil-type emulsion method.5 The reason behind the selection of the above-mentioned ratio is due to its increase in brake thermal efficiency and decrease in specific fuel consumption, SD, PM, hydrocarbons (HCs), and carbon monoxide (CO). Much of the ethanol blending with diesel for the preparation of the emulsified fuel project has been carried out in countries such as Brazil, parts of the U.S.A., and some of the European countries.3,4 Their blending nature is only 5-10% (a maximum of 15%) of ethanol-diesel fuels. However, in this project, 50% ethanol and 50% diesel (50D/50E) have been used. Thus, this will not only reduce the problem of pollution but will also lessen the import bill for oil for many countries. The test engine available in our lab has been used to conduct the load test, by keeping speed constant.5 Similarly, the same results have also been obtained by keeping the load constant under varying speed levels.6 Speed as well as load tests have yielded very good results for the fuel ratio of 50D/50E without any modification being carried out in the diesel engine.6 A very small variation in efficiency is obtained in the load test. Considering all of the points, the selected emulsified fuel ratio is found to be the best one based on the better performance, less emissions, and lower cost. The cost of ethanol becomes less if ethanol production is increased. In the earlier decades, people knew that ethanol was a fuel and it could be mixed with
Introduction Diesel engines, rigid and simple in structure and known for their fuel economy, remain the major source for inland transportation and industrial power plants. Owing to their dominant advantages of high thermal efficiency, they are found to be the most advantageous fuel combustion engines and are expected to remain so in the foreseeable future. In short, they have proven their role for the consumption of diesel in the past as well as in the present. Also, the number of vehicles in industries, transportation, and agriculture will increase in the future. Therefore, use of diesel engines will definitely increase in the future. However, the pollutants emitted from the diesel engines are detrimental to human health as well as the ecological environment. Hence, diesel engines have been considered as one of the major air pollution sources. The major pollutants from diesel engines are particulate matter (PM), smoke density (SD), oxides of nitrogen (NOx), and other harmful emissions. These pollutants cause damage to the ozone layer, enhance the greenhouse effect, and produce acid rain. The photochemical smog formed from the reaction of NOx with ultraviolet sunlight might also damage the respiratory system, throat, and eyes. PM taken with polycyclic aromatic hydrocarbon (PAH) or metallic compounds, if inhaled continuously, might cause carcinogen diseases.1 The emulsification technique is one of the possible approaches to improve fuel economy and reduce the emission of pollutants from diesel engines.2 In this technique, ethanol has a higher miscibility with diesel fuel. Therefore, the use of ethanol in compression-ignition (CI) engines has received considerable attention in recent years.3 Ethanol addition to *To whom correspondence should be addressed. E-mail: mpab97@ yahoo.com. (1) Pischinger, F. F. Compression Ignition Engines; Academic Press: London, U.K., 1998; pp 261-263. (2) Marek, A. I.; Sayed, N. T. Presented at the National Conference on Ethanol Policy and Marketing, Las Vegas, NV, 2000. (3) Mohammadi, A.; Ishiyama, T.; Kakuta, T.; Kee, S.-S. SAE Tech. Pap. 2005-01-1725, 2005. r 2010 American Chemical Society
(4) Castanheira Faria, M. D.; da Cunha Pinto, R. R.; Murta Valle, M. L. SAE Tech. Pap. 2005-01-4154, 2005. (5) Ashok, M. P.; Saravanan, C. G. SAE Tech. Pap. 2007-01-2127, 2007. (6) Ashok, M. P.; Saravanan, C. G. National Conference on Biofuels for Internal Combustion Engines, National Institute of Technology (NIT), Suratkal, India, 2006; pp 24-29.
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Energy Fuels 2010, 24, 1822–1828
: DOI:10.1021/ef901306z
Ashok
Table 1. Properties of Ethyl Acetate, Ethanol, and Diesel Number 2 chemical formula boiling point (°C) cetane number self-ignition temperature (°C) viscosity in centipoise units at 20 °C specific gravity lower heating value (kJ/kg) density (kg/m3)
ethyl acetate
ethanol (100% proof)
diesel number 2
C4H8O2 77.1 143 426 0.45 0.8945 30600 906
CH3CH2OH 78 8 420 1.2 0.783 27000 794
C12H26 180-330 50 200-420 3.9 0.894 42800 830
emulsified fuel 150 95 390 2.1 0.873 801
method
ASTM D613 ASTM D 445 ASTM D 4809 ASTM D 1298
petrol products.3,9 However, at present, modifications have been made. The previous generations had less of an idea of the emulsified fuel; however, the present generation is well familiar with the use of ethanol, and any further work will be most welcomed in the future. Although emulsified fuel is used to a large extent in some countries, it has not become popular throughout the world. It is hoped that this efficient emulsified fuel will be implemented all over the world for its advantage of higher brake thermal efficiency, less specific fuel consumption, and less harmful emissions to compensate for the depletion of fossil fuel. Present Work The objective of this work is to study the performance and emission characteristics of ethyl acetate added (10% by volume basis) to emulsified fuel for the selected ratio of 50D/50E, and the results are to be compared to diesel fuel number 2. In the earlier work, it has been identified that emulsified fuel gives the best performance and reduces pollutants.6 The cetane number plays a vital role for the emission properties of the emulsified fuel. A lower cetane number increases the effect of the delay period. In addition, the enhancement of delay period increases the gas temperature, which in turn raises NOx emissions.7
Figure 1. Experimental setup.
produced by the helical blades of the shaft and fixed blades in the emulsified fuel vessel. In this traditional fuel injection system, fuel is fed through a high-pressure fuel pump. The high pressure and the starting and ending of the injection in the cylinder are controlled with the help of the fuel injection system. Only the feed inputs are fed into the computer, and the final output is obtained from the data acquisition system. The fuel injection nozzle has a sharp edge inlet injector, operating with a higher injection pressure to overcome friction loss. The engine is designed such that the injection pressure is fixed at 220 kgf/cm2. Also, in the traditional system, the injection pressure and flow rate of the fuel remain constant. Hence, in the traditional system, the injection time is being described as the fuel delivery angle. Also, the self-ignition temperature is the temperature at which “a substance can be brought to flames without any sort of external force, like a flame”.7 The self-ignition temperature for diesel number 2 ranges from 527 to 558 K. The properties of ethyl acetate, ethanol, diesel number 2, and emulsified fuel have been listed in Table 1. On the basis of the properties, the viscosity of diesel is 3.9 cP at 20 °C. Similarly, for emulsified fuel, the value is less than diesel fuel. Therefore, at 20 °C, the fuel injection system may inject the fuel without any problem. On the basis of the viscosity values, it is understood that diesel is more viscous than the emulsified fuel. Considering the viscosity of diesel fuel, the injection system injects emulsified fuel faster than diesel fuel. Hence, the entire system works without damaging any part of the fuel injection pump and other components.
Procedure for the Preparation of Emulsified Fuel On the basis of the hydrophile-lipophile balance (HLB) value, ethyl acetate has been selected for the preparation of emulsified fuel. Surfactant ethyl acetate is added by 1, 2, ..., 10% on a trial and error method for very low quantities of dispersion and dispersed media (by volume basis). The optimum quantity and quality of the surfactant have been identified at 10% (values varied on the basis of the quantity of ethanol, diesel, and surfactant). Hence, in this method of preparation of emulsified fuel, 10% ethyl acetate is added to 45% volume of diesel number 2. Then, 45% ethanol is added to the mixture. In the ethanol-indiesel emulsion fuel preparation method, diesel and ethanol are the dispersion and dispersed media, respectively. Hence, the dispersed medium is added slowly to the dispersion medium. After all of the above are added, the mixture is placed in a special type of mechanical stirrer, with the specifications of three-phase alternating current (AC) supply, 0-10 000 revolutions/min variable speed, vertical motor having twin blades, helical shape attached with the vertical shaft of the motor, and four zig-zag-shaped blades fixed in the emulsified fuel containing a drum vessel to obtain a swirl motion for better mixing. After the required time interval is allowed, a good emulsion is formed because of the effects
Experimental Section The experimental setup of the diesel engine is shown in Figure 1. Specifications of the engine are given in Table 3, and properties of test instruments and their values of accuracy are shown in Table 2. The fuel flow rate is obtained using the buret method, and the airflow rate is obtained on a volumetric basis. The NOx emission is obtained using an analyzer working on the chemiluminescence principle. The PM from the exhaust is measured with
(7) Ashok, M. P.; Saravanan, C. G. SAE Tech. Pap. 2007-01-2126, 2007.
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Table 2. Properties of Test Instruments and Their Values of Accuracy instruments
accuracy
fuel measurement (mL) temperature measurement (°C) dynamometer (load-applying error) (N m) tachometer (speed) (revolutions/min) cooling water flow rate (mL) di-gas analyzer (%)
þ5 þ3 þ5 þ10 þ10 þ5 in all measurements
Table 3. Specifications of the Test Engine type number of cylinder bore (mm) stroke (mm) compression ratio maximum power (kW) speed (revolutions/min) dynamometer injection timing injection pressure (kgf/cm2)
vertical, water cooled, four stroke 1 87.5 110 17.5:1 5.2 1500 eddy current 23° before TDC 220
the help of the micro high-volume sampler. An AVL smoke meter is used to measure the smoke capacity. An AVL DiGas 444 (DiTEST) five-gas analyzer is used to measure the rest of the pollutants from the range of 0-50 ppm for HC, 0-0.2% by volume for CO, and the delay period. This five-gas analyzer has been purchased from Digital Electronics Ltd., Japan. All of the measurements are collected and recorded by a data acquisition system. A buret is used to measure the fuel consumption for a specified time interval. During this interval of time, the fuel consumed by the engine is measured, with the help of a stopwatch. At the pressure of 220 kgf/cm2, the same engine is made to work with both emulsified fuel and diesel fuel. This is because ethanol is an easily combustible fuel. Also, the viscosities of diesel and emulsified fuels are 3.9 and 2.1 cP at 20 °C, respectively. The difference between the viscosity of diesel and emulsified fuel is 1.8 cP, which gives the variation of 46%. The viscosities of diesel and emulsified fuels are 3.9 and 2.1 cP at 20 °C, respectively. It shows that diesel has more viscosity than emulsified fuel. The mean droplet size increases with the increase in fuel viscosity. The values of viscosities of the different fuels have been measured, and the values are indicated directly. Because the viscosity of diesel fuel is high, larger droplets are formed at the circular orifice and cause a high penetration into the chamber. However, smaller droplets are required for quick mixing and evaporation of the fuel. The emulsified fuel, which has a low viscosity, forms smaller droplets at the circular orifice, leading to quick mixing and evaporation of the fuel. All of the tests have been carried out at a constant speed of 1500 revolutions/min under variable-load conditions. Performance and emission tests have been carried out for the emulsified fuel to find the optimum quality of ethyl acetate, and the results are compared to diesel number 2. Throughout the experiment, the static injection timing has been maintained at 23° before top dead center (TDC), which is optimal for the base diesel engine.
Figure 2. Quantity of ethyl acetate versus brake thermal efficiency.
Figure 3. Variation of brake thermal efficiency.
addition of ethyl acetate has not been found in use. This is the procedure for introducing the surfactant for the preparation of the emulsified fuel. The emulsified fuel ratio of 50D/50E gives a better efficiency than diesel fuel. The differences in values of the brake thermal efficiency between the emulsified fuel ratio of 50D/ 50E and the diesel fuel are 3.1% at the initial and 5.2% at the maximum load conditions (Figure 3). Specific fuel consumption (SFC) is defined as the ratio of the fuel consumption per unit time to power. This is attributed to the higher quantity of oxygen enriched in air present in ethanol fuel than in diesel fuel. The presence of the volume of air in ethanol and diesel fuel is 4.3-19 and 1.5-8.2, respectively, and the presence of the volume of oxygen in the surfactant ethyl acetate is 12-26.5. Also, the overall oxygen concentration in the emulsified fuel will vary from 48 to 59.2 (depending upon the availability of O2 in the atmosphere). The possible reason for this increase in efficiency is that ethanol contains oxygen atoms, which are freely available for combustion.8 The oxygen
Results and Discussion A graph (Figure 2) has been plotted exhibiting the relationship between the quantity of ethyl acetate and brake thermal efficiency. Normally, the brake thermal efficiency is defined as is the ratio of energy in the brake power to the input fuel energy. The graph result shows the clear value for the selection of the quantity of surfactant. From Figure 2, it is concluded that 10 mL of ethyl acetate blended with an ethanol-in-diesel fuel mixture gives maximum efficiency. After 10 mL, the next trial of 12 mL of ethyl acetate added to emulsified fuel has been prepared. However, the fuel prepared using 12 mL showed the problem of breaking (fuel instability problem). Hence, the preparation of emulsified fuel beyond 10 mL
(8) Kumar, N.; Sharma, P. B.; Das, L. M.; Garg, S. K. SAE Tech. Pap. 2004-28-032, 2004.
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Figure 4. Variation of SFC.
Figure 5. Variation of SD.
present in ethanol generally improves the brake thermal efficiency when it is mixed with neat diesel.7 Hence, the brake thermal efficiency increases as the concentration of ethanol is increased. The surfactant added has O2, which causes easy combustion. On the basis of the above reasons, the brake thermal efficiency is higher for emulsified fuel than for diesel fuel. From this, it is understood that emulsified fuel gives comparatively better efficiency without any modification in the present diesel engine. However, considerable attention has to be given to the compatibility and corrosiveness of the materials.9 SFC takes lower values for emulsified fuel than diesel fuel (Figure 4). This is because of the reduction in the energy content because of the addition of ethanol.10 The emulsified fuel mixture has a poor energy content as ethanol, which has a low energy content when added to diesel. Hence, the lower heating value (LHV) is less for the other two fuels when compared to diesel fuel. Because of this reason, SFC is lower for the emulsified fuel ratio of 50D/50E. The two parameters essential for the good performance of an engine, namely, thermal efficiency and SFC, are inverse in nature. This could be achieved with the emulsified fuel ratio of 50D/50E. Therefore, the performance of the engine will be good if it is run with emulsified fuel. It is seen from Figure 5 that the emulsified fuel ratio of 50D/ 50E takes lower values of SD than diesel fuel. The addition of ethanol and ethyl acetate causes a decrease in the smoke level, because of the better mixing of air and fuel and an increase in the OH radical concentration. This OH radical concentration is measured with the help of the five-gas analyzer to identify SD.11 Also, smoke emission of ethanol-in-diesel fuel emulsion is lower than those values obtained with neat diesel fuel, because of the soot-free combustion of ethanol under normal diesel engine operating conditions.11 SD decreases for the emulsified fuel as well as for the PM (Figure 6). It has become evident that SD and PM are directly proportional. Therefore, the higher the PM, the higher the SD and vice versa. PM is reduced because of the fact that ethanol
Figure 6. Variation of PM.
can be combusted essentially soot-free under typical combustion conditions.12 Here, the PM emission is higher for diesel fuel than the emulsified fuel ratio of 50D/50E. The difference in the value of PM emission between the 50D/50E ratio and diesel fuel at 5.2 kW brake power is 0.81 g kW-1 h-1. Figure 7 shows the variation of the brake power with the exhaust gas temperature. Emulsified fuel has given almost the same result given by diesel fuel for the exhaust gas temperature. At any brake power point condition, only þ32 °C variation of the temperature has been obtained. However, there is a smaller significant change with the decrease in values caused by emulsified fuel than diesel fuel because of the higher latent heat of evaporation of ethanol.13 Diesel number 2 gives a longer ignition delay for all load conditions. The longer ignition delay value is obtained by the (12) United States Environmental Protection Agency (EPA). A Report: Automobile Emissions. National Center for Environmental Research, U.S. EPA, Washington, D.C., 1994. (13) Corkwell, K. C.; Jackson, M. M.; Daly, D. T. SAE Tech. Pap. 2003-01-3283, 2003.
(9) Gunnerman, R. W.; Russel, R. L. SAE Tech. Pap. 972099, 1997. (10) Tsukahara, M.; Yoshimoto, Y. SAE Tech. Pap. 92046, 1992. (11) Subramanian, K. A.; Ramesh, A. SAE Tech. Pap. 2001-01-0205, 2001.
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Figure 7. Variation of the exhaust gas temperature.
Figure 9. Variation of NOx.
Figure 10. Comparison of HCs.
Figure 8. Variation of the ignition delay.
ethyl acetate added to emulsified fuel at all loads. This longer ignition delay increases the peak pressure.14 The ignition delay is the time taken for the first droplet of fuel hitting the hot air in the combustion chamber and also starting through the burning phase. Therefore, the emulsified fuel curve takes a high value for the delay period (Figure 8). With the introduction of ethyl acetate, the dynamic injection timing is retarded. This leads the fuel to being injected closer to TDC, where the air temperature is high. This phenomenon leads to a higher ignition delay.15 As the percentage of ethyl acetate added in the blending of the emulsified fuel increases, the delay period also increases. The delay period could be measured between the engine head transducers (Piezzo Electric) connected to the software installed in the data acquisition system. Hence, each and every pulse of the engine is passed to the data acquisition system. The signal from the software completes the work, and the result is displayed. Thus, the values are obtained.
The low cetane depressing properties cause an increase in the ignition delay and greater rates of pressure rise, resulting in high peak cylinder pressure and high peak combustion temperature. The higher peak temperature leads to the higher formation of NOx.7 Hence, the ethyl acetate emulsified fuel emits higher NOx (Figure 9). This is due to the increase in the ignition delay. This longer ignition delay increases the mass of the fuel accumulated before combustion and increases the initial combustion rates, thereby increasing the peak temperature, thus increasing the NOx formation.16 Figure 10 shows the emission of HCs, which is high for diesel fuel and low for emulsified fuel. The figure shows that values of the emulsified fuel and diesel fuel are almost the same for the two initial conditions. However, for the other loads, the emulsified fuel takes low values. Normally, HCs are the direct result of incomplete combustion. This is due to the increase in the availability of oxygen by the addition of ethyl acetate to the emulsified fuel. Also, the engine combustion chamber portions of the fuel air mixture, which come in direct
(14) Orlee, R. M.; Lenane, D. L. SAE Tech. Pap. 840108, 1984. (15) Afify, E. M.; Korah, N. S.; Dickey, D. W. SAE Tech. Pap. 870555, 1987.
(16) Miyamoto, N.; Ogawa, H.; Wang, J.; Ohashi, H. SAE Tech. Pap. 950609, 1995.
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Figure 13. Comparison of the heat release rate at 100% load. Figure 11. Comparison of CO.
Figure 14. P-θ for various fuels at 50% load.
Figure 12. Comparison of the heat release rate at 50% load.
decrease of CO in the emulsified fuel. As the air-fuel mixture ratio increases, the CO emission decreases. The difference in value between diesel fuel and emulsified fuel at 2.078 g/kW condition is 0.33 g kW-1 h-1. Figures 12 and 13 show the comparison of the heat release rate at 50 and 100% load conditions, respectively. In both cases, the emulsified fuel ratio releases more heat than diesel fuel. This is due to the higher and lower values of latent heat of evaporation of ethanol and diesel fuel, respectively (latent heat of evaporation: ethanol, 840 kJ/kg; diesel, 300 kJ/kg).20 Hence, emulsified fuel emits more heat release than diesel. At the rated output, the heat release rate is the highest with ethanol-diesel operation because of the enhancement of the premixed combustion phase. Normally, the rate of heat release largely depends upon the turbulence intensity and also the reaction rate, which are dependent upon the mixture composition. Therefore, 50D/50E based on its ethanol concentration takes the highest heat release rate value. Figures 14 and 15 show the comparison of the cylinder pressure at 50 and 100% load conditions, respectively.
contact with the chamber walls, are quenched, but they do not burn.17 Some of this quenched fuel air mixture is forced out of the chamber during the exhaust stroke. The high local concentration of HCs in this mixture contributes to the high HC exhaust from the engine. Also, the poor content of oxygen in the diesel fuel increases the HC emission.18 The difference in HCs is 0.03 g kW-1 h-1 at the maximum level condition. Figure 11 shows the comparison of the CO emission between diesel and emulsified fuel. The value of the CO emission decreases for the lowest load but increases for all other load conditions. The CO emission is a product of incomplete combustion because of insufficient amount of air in the air-fuel mixture. Because ethanol has less carbon content than diesel fuel and its oxygen content increases the air-fuel ratio in the fuel-rich region, it results in complete combustion.19 Therefore, the addition of ethanol causes a (17) Muller-Dethlefs, K.; Schlader, A. F. Combust. Flame 1976, 27, 205–215. (18) Donahue, R. J.; Foster, D. E. SAE Tech. Pap. 2000-01-0512, 2000. (19) He, B.-Q.; Wang, J.-X.; Yan X.-G.; Tian X. SAE Tech. Pap. 2003-01-0762, 2003.
(20) Ajav, E. A.; Singh, B.; Bhattacharya, T. K. Biomass Bioenergy 1998, 15 (6), 493–502.
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5.2 kW condition. (2) Emulsified fuel has obtained less SFC than diesel fuel. SFC decreases from 0.32 to 0.215 kg kW-1 h-1 for diesel fuel and the emulsified fuel, respectively. (3) The SD value has been reduced from 52 Hartridge smoke units (HSU) for diesel fuel to 40.6 HSU for emulsified fuel. (4) The PM value decreases more for emulsified fuel than for diesel fuel. The difference in the PM value for emulsified fuel and diesel fuel noted at 5.2 kW is 0.81 g kW-1 h-1. (5) There is not much difference of the value for exhaust gas temperature between the fuels. The exhaust gas temperature value has been reduced from 320 °C for diesel fuel to 288 °C for emulsified fuel at the maximum load condition. (6) The ignition delay period is higher for emulsified fuel than for diesel fuel. (7) The NOx level is higher for emulsified fuel than for diesel fuel. NOx formation is purely based on the peak combustion temperature. The difference in value of 0.88 g kW-1 h-1 has been obtained between diesel fuel and emulsified fuel at full-load condition. (8) HC emission values are lower for emulsified fuel than for diesel fuel. (9) The emission of CO is lower for emulsified fuel than for diesel fuel. At the maximum load condition, the value for the emulsified fuel is 0.0503%, and for diesel fuel, it is 3.43 g kW-1 h-1. (10) At both 50 and 100% load conditions, emulsified fuel releases more heat than diesel fuel. The heat release rate is lower for diesel fuel than the emulsified fuel because the latter retains the latent heat of evaporation of ethanol. (11) The pressure rise is higher for emulsified fuel than for diesel fuel at both 50 and 100% load conditions. (12) Also, a stability test was conducted for the prepared emulsified fuel. The duration taken for keeping the stability is 41 h and 30 min. On the whole, the emulsified fuel ratio of 50D/50E has given the best performance based on the higher brake thermal efficiency and NOx and lower specific fuel consumption than the diesel fuel (both are inverse). Also, on the emission part (SD, PM, HCs, and CO), fewer values are obtained for emulsified fuel than diesel fuel. Hence, the emulsified fuel ratio of 50D/50E is selected as the best fuel for the present engine.
Figure 15. P-θ for various fuels at 100% load.
Pressure rises for the surfactant ethyl acetate added to emulsified fuel (50D/50E) are higher than those for diesel fuel. The pressure rise is due to the amount of fuel involved in premixed combustion, which increases with a longer ignition delay.21 This longer ignition delay helps to reach a high peak pressure to produce more work output during the expansion stroke. Conclusions The 50D/50E ratio of the emulsified fuel has shown an increase in brake thermal efficiency and a decrease in specific fuel consumption, SD, PM, exhaust gas temperature, HCs, and CO. (1) Brake thermal efficiency increases from 41.4 to 46.6% for diesel fuel and emulsified fuel, respectively, at (21) Tsukahara, M.; Murayama, T.; Yoshimoto, Y. Bull. JSME 1982, 25 (202), 612–619.
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