EXPERIMENTAL STUDY ON EFFECTIVE USE OF MAHUA METHYL ESTER AS ALTERNATIVE TO DIESEL IN CI ENGINES Dr. Mrityunjayaswamy K M 1, Dr. Ramesha D K 2, Dr. Vijayasimhareddy B G 3 1 Associate Professor, Vemana Institute of Technology, Bangalore 2 Associate Professor, Thermal Science & Engineering, University Visvesvaraya College of Engineering, Bangalore University, K R Circle, Bangalore- 1 3 Principal, Vemana Institute of Technology, Bangalore Abstract--There is an increased interest in many countries to search for suitable alternative fuels which are environmental friendly. Vegetable oils and their methyl esters are found to be good alternative renewable fuels for compression ignition engines. The major problem associated with the direct use of vegetable oils is their high viscosity and low volatility. The best possible method to reduce viscosity is transesterification which produces esters of respective oils. This work presents the results of investigations carried out in studying the properties of mahua methyl ester and its blends with diesel fuel from % to % by volume and running a diesel engine with these fuels. The engine tests have been carried out to determine the performance and emissions and to compute the behavior of diesel engine running with above mentioned fuels. The B- blend substantially reduces the emission level with acceptable efficiency. The properties of methyl ester of mahua oil are comparable with conventional diesel. Further, the tests have been carried out at a constant speed of 15rpm at different brake power at three different injection pressures. The results show that mahua methyl ester blend (B-) performs well in running a diesel engine at bar injection pressure which is higher than rated injection pressure of diesel engine which is 18bar. Based on this study the methyl ester of mahua oil can be used as a suitable additive with diesel in compression ignition engine. I. INTRODUCTION Self reliance in energy is vital for the economic development of a nation. The needs to search for alternative sources of energy which are renewable and eco-friendly assume top priority in view of the uncertain supplies and frequent price hikes of fossil fuels in the international market. There is an increasing interest in many countries to search for suitable alternative fuels that are environment friendly. Although straight vegetable oils can be used in diesel engines, their high viscosities, low volatilities and poor cold flow properties have led to investigation of various derivatives. There are many tree species which bear seeds, rich in oil, having properties of an excellent fuel and can be processed into a diesel substitute. Some of the important varieties are Pongamia, Jatropha, Neem, Mahua, Simrouba, Sal, Undi, Pilu etc. Non-edible oils that can be used to produce biofuels are gaining world wide acceptance as one of the comprehensive solutions for problems of the environmental degradation, energy security, restricting imports, rural employment and agricultural economy [1, 2, 4]. Biofuels are the fuels produced by a number of chemical/ biological processes from biological materials like plants, agricultural wastes etc. Being sourced from trees already existing and to be further propagated, biofuel is a good source of renewable energy. Bio-diesel can be used as a pure fuel or blended with petroleum diesel in any proportions. The various alternative fuel options researched for diesel are mainly biogas, producer gas, ethanol, methanol and vegetable oils. Out of all these, vegetable oils offer an advantage because of its comparable fuel properties with diesel and can be substituted between %-% [2, 5]. Various edible vegetable oils like Sunf1ower, Soyabean, Peanut, Cotton seed etc have been tested successfully in diesel engines. Research in this direction with edible oils has yielded encouraging results. Since India imports a huge quantity of edible oils, the use of non-edible oils like Mahua (Madhuca Indica) oil need to be investigated. II. NEED FOR VEGETABLE OIL MODIFICATION Petroleum diesel fuel is a complex mixture of saturated, unsaturated, branched and non-branched, straight chain and aromatic molecules with carbon atoms ranging from 12 to 18. In contrast, vegetable oil is a mixture of organic compounds ranging from simple straight chain compounds to complex proteins, fat-soluble vitamins and fatty acids. Fatty acids vary in carbon chain length and in the number of unsaturated bonds (double-bonds). Vegetable oils are usually triglyceride with a number of branched chains of different lengths. IJIRAE 14-17, All Rights Reserved Page -7
The high viscosity of vegetable oils (25- cst) as compared to diesel oil (4 cst) at 4 C leads to unfavorable pumping and spray characteristics (atomization and jet penetration etc.). The inefficient mixing of fuel with air contributes to incomplete combustion and increased carbon deposition, injector clogging, piston ring sticking, lubrication oil dilution and degradation. The combination of high viscosity and low volatility of vegetable oils cause poor cold starting, misfire and longer ignition delay. The polyunsaturated nature of the vegetable oils causes long-term problems due to slow polymer gum formation causing ring sticking, excessive engine wear due to dilution of lubricating oil etc. Because of these problems, vegetable oils need to be converted to more compatible fuels for existing engines. Thus, neat vegetable oils need to be modified to bring their combustion related properties closer to those of mineral diesel oil. This fuel modification is mainly aimed at reducing the viscosity and increasing the volatility. Considerable efforts have been made to develop vegetable oil derivatives that approximate the properties and performance of the hydrocarbon based fuels. The problems with substituting triglycerides for diesel fuels are mostly associated with their high viscosities, low volatilities and polyunsaturated character. These can be changed in at least four ways: pyrolysis, micro emulsification, dilution and transesterification [2, 11]. III. TRANSESTERIFICATION Transesterification is the conversion of one ester into another, i.e. a glyceride ester into an alkyl ester, in case of biodiesel where methanol replaces the glycerine. The biodiesel molecule is smaller and less complex. Biodiesel has lower viscosity than raw vegetable oil, because the transesterification process shortens the carbon length of the fatty acid molecules in the oil. Transesterification converts the triple chain triglyceride vegetable oil molecule to three single chain methyl ester molecules with glycerine as a byproduct, but the chain lengths of the fatty acids themselves remains same. Triglycerides are esters, esters are acids such as fatty acids combined with an alcohol, and glycerine (glycerol) is a heavy alcohol. The catalyst breaks the bond holding the fatty acid chains to the glycerine, fatty acid chain then bonds with the methanol. Transesterification process occurs in three stages. First, one fatty acid chain breaks off the triglyceride molecule and bonds with methanol to form a methyl ester molecule, leaving a diglyceride molecule (two chains of fatty acids bound by glycerine). Then a fatty acid chain brakes off the diglyceride molecule and bonds with methanol to form another methyl ester molecule, leaving a monoglyceride molecule. Finally the monoglycerides are converted to methyl esters [2,4,6]. IV. PREPARATION OF BIODIESEL About.6 gms of catalyst is dissolved in ml methanol to prepare alkoxide and the mixture is stirred vigorously in a covered container until the alkali is dissolved completely in mins. The alcohol catalyst (KOH) mixture is then transferred to the reactor containing 8 ml moisture free vegetable oil. Stirring of the mixture is continued for five hours at a temperature between 6 C and 65 C. Provision is made to condense the evaporating methyl alcohol by fixing the condenser on the top of the reactor. Condenser is removed and the reactant is stirred for one hour to remove the excess methyl alcohol. The mixture turns turbid orange brown color within the first few minutes, then it changes to a clear transparent brown color and finally as the reaction is completed, the mixture becomes somewhat turbid and orange brown due to the emulsified free glycerol formed during the reaction. After about one hour the mixture is taken out and poured in to the separating funnel, soon the glycerol component of the mixture starts settling at the bottom. The mixture is allowed to settle by gravity in a separating funnel overnight. It is observed that two distinct layers are formed; one is pale yellow at the top and the other being dark brown at the bottom. Without disturbing the funnel the bottom layer is separated out, which is glycerol, can be used as a resource material for soap or paint industry. The layer, which is retained in the funnel, is methyl ester of the vegetable oil. It is then washed to remove moisture. To do this, distilled water about % by volume of the ester is added, shaken properly and the mixture is once again transferred to the separating funnel wherein again the water with any emulsion formed settles at the bottom. The upper layer is pure methyl ester that is biodiesel ready for the use in diesel engine. 4.1 PROPERTIES OF BIODIESEL: Before conducting the performance tests, important properties such as density, kinematic viscosity, flash point, fire point and calorific value of mahua oil, its methyl ester and its blends are determined and tabulated. The Table 1 gives the comparison of properties of raw mahua oil and its methyl ester with conventional diesel and Table 2 gives the properties of MME and its blends with diesel. The kinematic viscosity of mahua oil was found to be 9.9 times that of diesel determined at 4ºC. After transesterification, the kinematic viscosity is reduced to 1.34 times that of diesel fuel. It is further reduced with increase in percentage of diesel in the blend. Similar reduction in density was also observed. However, the calorific value of biodiesel was found to be 36914 kj/kg which is less than the calorific value of diesel (4296 kj/kg) and greater than that of the mahua oil (35614 kj/kg). As the percentage of biodiesel in the blend is increased, the calorific value decreases. Flash point of mahua oil and biodiesel were found to be greater than ºC, which is safe for storage and handling. 4.2 ENGINE TEST: Experiments were conducted on a computerised diesel engine test rig shown in Figure 1. Kirloskar make single cylinder, 4- stroke naturally aspirated direct injection, water cooled diesel engine of 5.2 kw rated power at 15 rpm was directly coupled to an eddy current dynamometer. The engine and the dynamometer are interfaced to a control panel which is connected to a digital computer. This computerised test rig was used for recording the test parameters such as fuel flow rate, temperature, air flow rate, load etc. and for calculating the engine performance characteristics such as brake power, brake thermal efficiency, brake specific fuel consumption, volumetric efficiency etc. IJIRAE 14-17, All Rights Reserved Page -71
The calorific value and the density of the particular fuel were fed to the test rig software for calculating the performance parameters. Exhaust emissions such as NO x, UBHC, and CO were measured with exhaust gas analyzer and smoke opacity using an AVL smoke meter. Figure 1: Experimental Set up. V. EXPERIMENTAL PROCEDURES: The whole set of experiments were conducted at the rated speed of 15rpm, compression ratio 17.5:1 and injection timing of 27 btdc. The tests were conducted at various loads with B,, B,, and B. Experiments were repeated at the three different injection pressures of 18, and 2 bar for optimized blend. VI. RESULTS AND DISCUSSION 6.1 OPTIMIZATION OF BLEND 6.1.1 BRAKE THERMAL EFFICIENCY (BTE) The variation of BTE with brake power (BP) for methyl ester and its blends compared with diesel is shown in Figure 2. The BTE is improved with increase in BP for all fuels. This is due to reduction in heat loss. It is seen from the Figure, that the B,, B and fuels have given higher efficiency than the diesel fuel at full load condition, but and B fuels is slightly lower than the diesel. The maximum BTE is obtained, nearly % for, which is higher than the diesel fuel (28%) at full load conditions [7, 11]. 35 1 BTE (%) 25 15 B B B NOx (ppm) 1 9 8 7 6 5 B B B Figure 2: Figure 3: Variation of BTE with Load for MME and its blends Variation of NOx with Load for MME and its blends 4 1 2 3 4 5 6 IJIRAE 14-17, All Rights Reserved Page -72
6.1.2 OXIDES OF NITROGEN (NO X ): The variation of NO x with BP for different fuels is shown in Figure 3. The amount of NO x is increased with increase in load for all fuels. This is because of increase in temperature of combustion chamber with increase in load, NO x emission mainly depends on temperature. The NO x emission for and fuels are measured as ppm and 4 ppm, which is lower compared to diesel [7,11]. 6.1.3 CARBON MONOXIDE (CO): The Figure.4 presents variation of the CO with BP for all fuels considered. From the Figure it is seen that the amount of CO decreased at part loads again increased at full load conditions for all fuels. The CO emission is approximately 25% to % less in case of biodiesel and its blends compared to diesel. The CO emission of is about 42% lower than the diesel fuel. This is due to the presence of oxygen in the fuel, which promotes more complete combustion [7, 11]..6 7 CO (%).5.4.3.2 B B B Unburnt HC (ppm 6 5 4 B B B.1 Figure 4 Figure 5 Variation of CO with Load for MME and its blends Variation of UBHC with Load for MME and its blends 6.1.4 UNBURNT HYDROCARBON (UBHC): The variation of UBHC with BP for all fuels is presented in Figure 5. The UBHC increases with increase in load for all fuels. The UBHC emission for pure biodiesel and its blends are lower than the diesel fuel. The UBHC for is approximately % to 35%, less than with diesel, which indicates more complete combustion of the fuel [7, 11]. 6.1.5 SMOKE OPACITY: The Figure 6 indicates the variation of opacity with BP for all fuels. The opacity is increased with increase in load for biodiesel and its blends; but the opacity is lower compared to diesel fuel. The opacity for methyl esters is approximately 55% in an average, which is less than that of diesel fuel (67%) [7,11]. 7 6 Opacity (%) 5 4 B B B 6.2 OPTIMIZATION OF INJECTION PRESSURE Figure 6: Variation of Opacity with Load for MME and its blends. 6.2.1 BRAKE THERMAL EFFICIENCY (BTE): The Figure 7 presents the variation of BTE with load for fuel at three injector opening pressures. The maximum BTE obtained is 29.84% for fuel at injection pressure of 2 bar for full load condition, which is higher than that of conventional diesel fuel (28.48%). The increase in BTE with increase in injection pressure is nearly one percent. This may be due to improved atomization [5,6,]. IJIRAE 14-17, All Rights Reserved Page -73
35 7 Brake Thermal Efficiency (%) 25 15 at 18 bar 16bar 18bar bar 2bar Opacity (%) 6 5 4 at 18 bar 16bar 18bar bar 2bar Figure 7: Variation of BTE with Load for MME at different Injection Pressures. Figure 8: Variation of Opacity with Load for MME at different Injection Pressures 6.2.2 SMOKE DENSITY: The variation of smoke density produced during the emission test of the engine for the fuels is presented in Figure 8. The smoke density is minimum for fuel for bar injection pressures. It is also observed that for all blends the smoke density is lower than that of diesel fuel. Smoke density is decreased with increase in injector opening pressure at full load condition [5,6,]. 6.2.3 NO X EMISSION: The variation of NOx with loads at four injector opening pressures and diesel at 18bar is shown in Figure 9. The amount of NOx is increased with increase in load for all fuels. The NOx emission is increased with increase in injector opening pressure due to the fact that NOx formation is a strongly temperature dependent phenomenon. On an average 8% reduction in NOx is obtained for biodiesel as compared to diesel. Similar trends of observations on CO production are also reported while running the diesel engines with methyl esters of mahua oil. The reductions in emissions (CO, smoke density and NOx).This is due to complete combustion of fuel as compared to diesel [5,6,]. 1 1 NOx (ppm) 9 8 7 6 5 at 18 bar 16bar 18bar bar 2bar 4 Figure 9: Variation of NOx with Load for MME at different Injection Pressures. VII. CONCLUSIONS The following conclusions are made based on the results obtained from both experimental and characteristic analysis of mahua oil and listed below: The mahua tree is indigenous to India; grows even in draught prone areas and is abundant in all parts of India. Mahua oil is a renewable and important alternative fuel. After transesterification of mahua oil, kinematic viscosity and density are reduced and calorific value is increased. The BTE is high for fuels which is approximately 2% higher than that of the diesel and other blends. The UBHC, CO and smoke opacity are significantly reduced with biodiesel and its blends. Compared to diesel fuel NOx emission is high for pure biodiesel and is low for fuel. Based on the engine performance and emission test, % blends of methyl esters with diesel fuel have better performance and lower emission characteristics, compared to other blends. For all fuels tested the BTE increases with increase in load and with increase in injection pressure. NOx emissions were lower at bar injection pressure indicating that effective combustion was taking place during early part of the expansion stroke. With increase in injection pressure emissions such as smoke and CO were reduced for biodiesel. This could be due to more complete combustion of the fuel compared to diesel. IJIRAE 14-17, All Rights Reserved Page -74
From the above discussions it can be concluded that a significant improvement in the performance and emissions are observed if the blend and injection pressure are properly optimized when a diesel engine is to be operated with methyl esters of mahua oil. NOMENCLATURE MME: Mahua oil Methyl Ester. BTE: Brake Thermal Efficiency. CO: Carbon Monoxide. CO 2 : Carbon Dioxide. UBHC: Unburnt Hydrocarbon. NO x : Oxides of Nitrogen. KOH: Potassium Hydroxide. NaOH: Sodium Hydroxide. REFERENCES [1]. Pringin V Non Traditional oil seeds of India 1987 Oxford and IBH publishing company Pvt Ltd. [2]. A.S Ramdas, S. Jayaraj, C Muraleedharan Use of vegetables oils as IC engine Fuels-A review Renewable Energy29 (4) pp 727-742 [3]. 3. Gerhard Knothe, Monitoring a Progressing Transesterification Reaction by Fiber-Optic Near Infrared Spectroscopy with Correlation to 1H Nuclear Magnetic Resonance Spectroscopy, Paper no. J9483 in JAOCS 77, May, pp489-493. [4]. Ramesha D.K., B.J. Ranganath, N. Rana Pratap Reddy. Characteristics of Ethanol Esterified Pongma Pinnata and Madhuka indica oils for compression ignition engine applications Journal of middle European construction and design of cars. Vol 5 pp 31-36[Nov 7]. [5]. Narayana Reddy, A Ramesh, Parametric studies for improving the performance of Jatropa oil-fuelled compression ignition engine Journal of Renewable Energy, vol31,pp 1994-16,[6]. [6]. R J Crooks, Comparative bio-fuel performance in internal combustion engines, Journal of Biomass and Bio energy vol, [6], pp461 468. [7]. Ramesha D.K, B.J. Ranganath, N.Rana Pratap Reddy. Control of physical properties of Bio- oils for application in IC engines., Proceedings of national conference on emerging trends in physics, electronics and engineering sciences Allied publishers Pvt ltd, New- Delhi.ISBN-81-8424-98-8. [8]. Dr. B.J. Ranganath, Dr. N. Ranapratap Reddy, Ramesha D.K., Dec 7, Performance and Evaluation of Ethanol Conditioned Mahua and Honge oils for IC Engine applications Intl CONICI-7, JNT University, Andhra Pradesh, India, pp 57-62. [9]. Ramesha D.K, B.J. Ranganath, N.Rana Pratap Reddy. Effect of Injection Parameter on performance and emissions characteristics of ethanol esterified Mahua and Honge oils for CI Engine applications Proceedings of the National Conference on Recent Advances in Mechanical Engineering (RAIME 8) - 21 March 8, National Engineering College, K.R. Nagar, Kovilpatti 628 53. Tamil Nadu, India pp 53-6. []. Ramesha D.K, B.J. Ranganath, N.Rana Pratap Reddy.(7) Effect of injector opening pressure on performance and evaluation of esterified Mahua and Honge oils for CI Engine applications Proceedings of National conference on Advances in materials and manufacturing processes, October 5-6,7, UBDT, Kuvempu university, Karnataka, pp59-513. [11]. Rana Pratap Reddy, Basavarajaiah T Performance and Emissions of engine (methyl ester of Honge oil) and its blends, Proceedings of Intl conference on Bio fuels propespctives and prospects. 16-17, sept4. APPENDIX: TABLE 1: COMPARISON OF PROPERTIES OF RAW VEGETABLE OIL AND ITS BLENDS WITH CONVENTIONAL DIESEL FUEL. PROPERTIES DIESEL RAW MAHUA OIL MME Density (kg/m 3 ) at 4 C 828 891 863 K.V (cst) at4 C 3.8 37.63 5. Calorific Value (kj/kg) 4296 35614 36914 Flash Point ( C) 56 212 129 Fire Point ( C) 63 223 141 TABLE 2: PROPERTIES OF MAHUA OIL METHYL ESTER (BIODIESEL) AND ITS BLENDS WITH DIESEL PROPERTIES B B B DIESEL Density (kg/m 3 ) at4 C 8 833 837 839 842 863 828 K.V (cst) at4 C 3.91 4.4 4. 4.32 4.45 5.1 3.78 Calorific Value (kj/kg) 42349 4175 41156 4668 39963 36914 4296 Flash Point ( C) 3 5 8 111 129 56 Fire Point ( C) 9 111 114 1 123 141 63 IJIRAE 14-17, All Rights Reserved Page -75