Experimental study on mahua methyl ester

International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163
Issue 04, Volume 4 (April 2017) (SPECIAL ISSUE) www.ijirae.com
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EXPERIMENTAL STUDY ON EFFECTIVE USE OF MAHUA
METHYL ESTER AS ALTERNATIVE TO DIESEL IN CI
ENGINES
Dr. Mrityunjayaswamy K M 1
, Dr. Ramesha D K2
, Dr. Vijayasimhareddy B G3
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- 01
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 20% to 100% 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-20 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 1500rpm at different brake power at three different injection pressures. The results show that mahua
methyl ester blend (B-20) performs well in running a diesel engine at 200bar injection pressure which is higher than
rated injection pressure of diesel engine which is 180bar. 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
20%-100% [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.

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The high viscosity of vegetable oils (25-200 cSt) as compared to diesel oil (4 cSt) at 40°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 0.6 gms of catalyst is dissolved in 20 ml methanol to prepare alkoxide and the mixture is stirred vigorously in a
covered container until the alkali is dissolved completely in 20 mins. The alcohol catalyst (KOH) mixture is then transferred
to the reactor containing 80 ml moisture free vegetable oil. Stirring of the mixture is continued for five hours at a
temperature between 600
C and 650
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 30% 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 40ºC. 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 (42960 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 100ºC, 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 1500 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.

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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 NOx, 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 1500rpm, compression ratio 17.5:1 and injection timing
of 270
bTDC. The tests were conducted at various loads with B10, B20, B30, B40, B50 and B100. Experiments were
repeated at the three different injection pressures of 180, 200 and 220 bar for optimized blend B20.
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
B10, B20, B30 and B40 fuels have given higher efficiency than the diesel fuel at full load condition, but B50 and B100 fuels
is slightly lower than the diesel. The maximum BTE is obtained, nearly 30% for B20, which is higher than the diesel fuel
(28%) at full load conditions [7, 11].
Figure 2: Figure 3:
Variation of BTE with Load for MME and its blends Variation of NOx with Load for MME and its blends
10
15
20
25
30
35
0 1 2 3 4 5 6
Brake Power (kW)
BTE(%)
Diesel
B100
B50
B40
B30
B20
B10
300
400
500
600
700
800
900
1000
1100
1200
1 2 3 4 5 6
Brake Power (kW)
NOx(ppm)
Diesel
B100
B50
B40
B30
B20
B10

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6.1.2 OXIDES OF NITROGEN (NOX):
The variation of NOx with BP for different fuels is shown in Figure 3. The amount of NOx is increased with increase in load
for all fuels. This is because of increase in temperature of combustion chamber with increase in load, NOx emission mainly
depends on temperature. The NOx emission for B20 and B40 fuels are measured as 1030 ppm and 1040 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 30%
less in case of biodiesel and its blends compared to diesel. The CO emission of B20 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].
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 B20 is approximately
30% 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].
Figure 6: Variation of Opacity with Load for MME and its blends.
6.2 OPTIMIZATION OF INJECTION PRESSURE
6.2.1 BRAKE THERMAL EFFICIENCY (BTE):
The Figure 7 presents the variation of BTE with load for B20 fuel at three injector opening pressures. The maximum BTE
obtained is 29.84% for B20 fuel at injection pressure of 220 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 [5,6,10].
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6
Brake Power (kW)
UnburntHC(ppm)
Diesel
B100
B50
B40
B30
B20
B10
0
0.1
0.2
0.3
0.4
0.5
0.6
0 1 2 3 4 5 6
Brake Power (kW)
CO(%)
Diesel
B100
B50
B40
B30
B20
B10
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6
Brake Power (kW)
Opacity(%)
Diesel
B100
B50
B40
B30
B20
B10

____________________________________________________________________________________________________
Figure 7: Variation of BTE with Load for Figure 8: Variation of Opacity with Load for B20 B20
MME at different Injection Pressures. 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 B20 fuels is presented in Figure 8.
The smoke density is minimum for B20 fuel for 200 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 [5,6,10].
6.2.3 NOX EMISSION:
The variation of NOx with loads at four injector opening pressures and diesel at 180bar 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 [5,6,10].
Figure 9: Variation of NOx with Load for B20 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 B20 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 B20 fuel.
 Based on the engine performance and emission test, 20% 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 200 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 B20 biodiesel. This could be
due to more complete combustion of the fuel compared to diesel.
10
15
20
25
30
35
0 1 2 3 4 5 6
Brake Power (kW)
BrakeThermalEfficiency(%)
Diesel at 180 bar
160bar
180bar
200bar
220bar
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6
Brake Power (kW)
Opacity(%)
Diesel at 180 bar
160bar
180bar
200bar
220bar
300
400
500
600
700
800
900
1000
1100
1200
0 1 2 3 4 5 6
Brake Power (kW)
NOx(ppm)
Diesel at 180 bar
160bar
180bar
200bar
220bar

____________________________________________________________________________________________________
 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. CO2: Carbon Dioxide. UBHC: Unburnt Hydrocarbon.
NOx: 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
(2004) 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 2000,
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 05 pp 31-36[Nov 2007].
[5]. Narayana Reddy, A Ramesh,” Parametric studies for improving the performance of Jatropa oil-fuelled compression
ignition engine” Journal of Renewable Energy, vol31,pp 1994-2016,[2006].
[6]. R J Crooks, “Comparative bio-fuel performance in internal combustion engines”, Journal of Biomass and Bio energy
vol 30, [2006], 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-81-8424-098-8.
[8]. Dr. B.J. Ranganath, Dr. N. Ranapratap Reddy, Ramesha D.K., Dec 2007, “Performance and Evaluation of Ethanol
Conditioned Mahua and Honge oils for IC Engine applications” Intl CONICI-2007, JNT University, Andhra Pradesh,
India, pp 57-62.
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characteristics of ethanol esterified Mahua and Honge oils for CI Engine applications” Proceedings of the National
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APPENDIX:
TABLE 1: COMPARISON OF PROPERTIES OF RAW VEGETABLE OIL AND ITS BLENDS WITH CONVENTIONAL DIESEL FUEL.
TABLE 2: PROPERTIES OF MAHUA OIL METHYL ESTER (BIODIESEL) AND ITS BLENDS WITH DIESEL
PROPERTIES DIESEL RAW MAHUA OIL MME
Density (kg/m3
) at 40˚C 828 891 863
K.V (cSt) at40˚C 3.8 37.63 5.10
Calorific Value (kJ/kg) 42960 35614 36914
Flash Point (˚C) 56 212 129
Fire Point (˚C) 63 223 141
PROPERTIES B10 B20 B30 B40 B50 B100 DIESEL
Density (kg/m3
) at40˚C 830 833 837 839 842 863 828
K.V (cSt) at40˚C 3.91 4.04 4.20 4.32 4.45 5.1 3.78
Calorific Value (kJ/kg) 42349 41750 41156 40668 39963 36914 42960
Flash Point (˚C) 100 103 105 108 111 129 56
Fire Point (˚C) 109 111 114 120 123 141 63

Experimental study on mahua methyl ester

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