Characterization of Diesel Engine Generator Operating at Different
Compression Ratio Fuelled with Palm Oil Biodiesel
Belyamin Belyamin1,a, Alias Mohd. Noor2,b, Mohanad Hamzah Hussein3,c, and Mazlan Said4,d
1 Transportation Research Alliance, Universiti Teknologi Malaysia, 81300 UTM Skudai,
Johor, Malaysia 2 Mechanical Engineering Department, Politeknik Negeri Jakarta, Depok 16425, Indonesia
3Mechanical Engineering Faculty, Universiti Teknologi Malaysia, 81300 UTM Skudai,
Johor, Malaysia
Keywords: Palm oil methyl ester, variable compression ratio, four stroke, direct injection
Abstract. Experiment to determine exhaust gas emission and combustion characteristics of a
compression ignition generator was carried out. The experiment used single cylinder four strokes
direct injection engine which was fuelled with diesel and palm oil methyl ester of B2 (blends 2%
palm oil methyl ester with 98% diesel on a volume basis), B5, B7 and B10. The experiment was
conducted at a fixed engine speed of 3000 rpm and 50% load with variety compression ratios of
16:1, 18:1, and 20:1and 22:1. Optimum compression ratio, influence of compression ratio on
specific fuel consumption and thermal efficiency were examined. Palm oil methyl ester produce
better output when the engine operate with variable compression ratio. Specific fuel consumption
decrease, NOx increase and thermal efficiency increase when optimum compression ratio of engine
is operated.
Introduction
There is a global increase in the investigation on the application of alternative fuel sources for
daily use, such as biodiesel and alcohol. This is due to the fact that petroleum products are
becoming very scarce and expensive and also the price of petroleum products is always on the high
side. There is also an awareness of air pollution caused by the extensive use of conventional fuel in
an internal-combustion engine.
In the past two decades, vegetable oil such as mahua oil, sun flower, seed oil, waste cooking oil,
and palm oil have been used as a substitute to diesel in an internal-combustion engine [1, 2, 3].
These papers study the performance and emission characteristic of generator fueled with biodiesel
or its blend. It shows that biodiesel can substitute fossil fuel in an internal-combustion engine with
or without engine modification. It is also economical and competitive compare to pure diesel. When
the fuel is waste palm oil, no engine modification is required.
In addition, biodiesel has lower sulphur, aromatics contents, and net carbon dioxide (CO2)
emission [4]. It has better lubricity and biodegradability and less toxic relative to fossil diesel [5].
Bio diesel can be used readily since it can be mixed at any proportion with diesel. This enables it to
be applied immediately in diesel power generator without much modification. Considering exhaust
emissions, the use of bio diesel results in lower emissions of unburnt hydrocarbons, carbon
monoxide, smoke and particulate matter beside some increase in emissions of NOx [6]. A number of
researchers have investigated vegetable oil-based fuels [2, 3, 7, and 8]. Vegetable oil can be safely
burnt for a short period of time in a diesel engine [3]. However, the use of raw vegetable oil for
extended period of time may result in severe engine deposits, piston ring sticking, injectors choking,
and thickening of the lubricating oil.
This experiment is to determine exhaust gas emission and combustion characteristics of a
compression ignition generator using B2, B5, B7 and B10.
Applied Mechanics and Materials Vol. 388 (2013) pp 241-245Online available since 2013/Aug/30 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMM.388.241
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Methodology
Experiment to examine combustion characteristic and exhaust gas emission was conducted on a
four stroke single-cylinder diesel engine generator for variety CR (Compression ratio) and fuel such
as diesel fuel, D, and biodiesel formulation, B2, B5, B7 and B10.
Diesel fuel was combusted in diesel generator Yanmar l70N6-MTRIYJ of standard compresion
ratio 20. Power generated was loaded by set of lamps. Electric current and voltage of the lamps were
measured to determine power. This method is an alternative way to determine power by measuring
electrical power instead of mechanical power. In mechanical power, the power is observed by
torque measurement. Besides, fuel consumed was measured by determining time taken by diesel
generator to consume certain amount of fuel. The rotation of the engine was also monitored. The
exhaust gases emissions such as NOx, CO, CO2 and exhaust smoke density was measured by using
the emission analyzer. After combustion of pure Diesel fuel, The experiment was repeated using
fuel of biodiesel formulation of 2% biodiesel and 97% diesel (B2), B5, B7, and B10.
The experiments were repeated for different compression ratio. Variety of CR is achieved by
changing the cylinder head gasket thickness. CR increase when gasket thickness is reduced.
All these results were discussed to determine the effect of changing the CR and fuel formulation.
Result and Discussion
Specific Fuel Consumption. Fuel consumption, FC, is calculated by Equation 1.
FC = V / t. (1)
Specific Fuel Consumption is then calculated by Equation 2
SFC = FC/ P. (2)
The variation of Specific Fuel Consumption (SFC) with Compression Ratio (CR) is given in Fig. 1.
It can be observed that the SFC is a clear indication of efficiency with which the engine develops
power. The smaller SFC indicates the more effective use of fuel to generate power. For all fuels
tested, the SFC have optimum value at CR 20. This is due to increase of temperature in combustion
chamber, leading to complete combustion. It has been observed that the maximum SFC of B2
reduced by 0.96% at CR 20 relative to CR 22. At CR 18 and 16, SFC B5 and B7 have the highest
rise of SFC by 1.1%, 1.26% respectively. This indicates the CR 18 and 16 is not a proper
compression ratio to be used. This is because to be efficient in use of fuel is to use fuel in condition
with lower SFC. This happen in CR 20 to 22. B10 always have the higher value of SFC which mean
the worst one in term of fuel efficiency. At higher percentage of blends, the SFC increases due to
decrease in calorific value.
Thermal Efficiency. Thermal efficiency is calculated by Equation 3
�th = P/ Qin. (3)
Qin is calculated by Equation 4
Qin = m CV . (4)
The thermal efficiency (ɳth) of the engine is considered one of the most important criteria for
evaluating the performance of the engine. It indicates the combustion effectiveness of the engine.
242 Advances in Thermofluids
The �th is defined as the actual work per cycle divided by fuel chemical energy (fuel calorific
value). Fig. 2 shows the variation in �th with CR for blends fuel tested. The �th of biodiesel at all
blends was found to be lower than diesel for all CR monitored. This might be due to lower fuel heat
value and so higher fuel consumption of the bio diesel blends to produce the same power.
In this figure, it appears that the optimum �th of B2 occur at CR 20. This may be due to the fuel
calorific value and low SFC. At CR 18 and CR 16 the �th of B5, B7 reduce by 11%, 17%
respectively compare to CR 20, it was also observed that �th of biodiesel can follow the increase of
�th of biodiesel although the value is lower than that of diesel. Due to their low volatility and high
viscosity, biodiesel perform relatively better at higher compression ratios [9].
Exhaust Gas Emission
Nitrogen Oxide. The variation of Nitrogen Oxide (NOx) with respect to CR for different blends
and constant load is shown in Fig. 3. NOx emission for diesel and other blends increase when the
CR is increased. The augmentation in the biodiesel ratio in the fuel blend increased NOx emissions
by 1.07%, 1.12%, 1.16% and 1.18% for B2, B5, B7 and B10, respectively, the reason for higher
NOx emission for blends is higher peak temperatures. This figure shows an increase in NOx by 1.3%
at CR 22 while the NOx decreased by 17.7% and 30% at CR 18:1 and 16:1 respectively as compared
to the CR 20. The changes in NOx resemble up to some extent to exhaust temperature which is
related to an increase in CR.
Carbon Monoxide. Fig. 4 illustrate the variation of CO for variety fuel blends with respect to
CR. From this figure it seen that the specified blends produce less CO emission than diesel for every
CR at applied load, it might due to increase the cylinder temperature. Therefore engine temperature
Fig. 1. Variation of specific fuel consumption
with compression ratio for different fuel blends
Fig. 2. Variation of thermal efficiency with
compression ratio for different fuel blends
Fig. 3. Variation of Nitrogen Oxide with
compression ratio for different fuel blends
Fig. 4. Variation of Carbon Monoxide with
compression ratio for different fuel blends
Applied Mechanics and Materials Vol. 388 243
lead to better combustion process and might cause less CO emission. The CO decrease by 29.1%,
10.87%, 4.2% and 0.5% when the compression ratio increase from 20 to 22 for diesel,B2,B5,B7
and B10 respectively, This could be because biodiesel provide more oxygen to the combustion
chamber. This lead to the more complete combustion. The other reason is that the percentage of CO
decreases due to rising temperature in the combustion chamber. physical and chemical properties of
the fuel, air–fuel ratio, the effects of fuel viscosity on spray quality will be expected to cause CO
emission increase with vegetable oil fuels [10].
Carbon Dioxide. The variation of CO2 with CR is shown in Fig. 5. From this figure, it can be
observed that the CO2 emission when enhine operating with CR 22 increases by around 18% than
CR20. In decreasing CR, blends of fuel increase its CO2 emission by 4%, 4.5%, 8% and 11% for the
B2, B5, B7 and B10 respectively. This is due to the high oxygen content of blends. Higher amounts
of CO2 is an indication of complete combustion of fuel in the combustion chamber. It also relates to
the exhaust gas temperature. CO2 emissions of the fuel blends slightly increase by increasing the
load for specified compression ratios due to complete combustion.
Smoke Density. The variation of Smoke density emission with VCR at constant load is shown in
Fig. 6. In this figure, it was shown that the smoke density increased by 35% and 60% when the CR
decreased to 18 and 16 respectively. At lower CR the temperature is lower. Incomplete combustion
in the combustion chamber then lead to more smoke exhausted from the engine. The smoke
decreased when the blends percentage is increased. These figures show that the smoke was reduced
significantly by around 9%, 12%, 17% and 22% for B2, B5, B7 and B10 than diesel. In addition, it
was found that the maximum reductions were around 20% at CR 22 for all fuel blends than CR20,
this is due to the increase of inside temperature of the combustion chamber and because palm oil
contains more oxygen which improves the combustion process. At the end this will decrease the
smoke. The Smoke is emitted from diesel engines because of the incomplete combustion in the
combustion chamber.
Conclusion
An experimental was conducted on direct injection diesel engine generator evaluate the
performance, combustion and exhaust emission at different blends and compression ratio. Bio diesel
blend can replace pure diesel oil although its heating value is relative lower. Biodiesel replacement
to pure diesel reduce CO emission and increase CO2. It indicates better combustion performance.
Optimum CR to provide optimum SFC and Thermal efficiency is 20 and above
Fig. 5. Variation of Carbon Oxide with
compression ratio for different fuel blends
Fig. 6. Variation of Smoke density with
compression ratio for different fuel blends
244 Advances in Thermofluids
Acknowledgment
The authors are grateful to the Ministry of Higher Education and Universiti Teknologi Malaysia for
grant GUP project under Vot Q.J130000.2609.00J35 and Q.J130000.2444.00G54.
Nomenclature
B2 blend of 2% biodiesel and 98% diesel
B5 blend of 5% biodiesel and 95% diesel
B7 blend of 7% biodiesel and 93% diesel
B10 blend of 10% biodiesel and 90% diesel
CO carbon monoxide
CO2 carbon dioxide
CR compression ratio
CV Calorific Value of fuel
D 100% diesel
FC Fuel consumption
m mass flow rate of fuel
NOx nitrogen oxides
O2 oxygen
P Power generated
Qin Heat input
t time taken to consume the fuel
SBFC specific brake fuel consumption
VCR variable compression ratio
V volume of fuel used
ɳth brake thermal efficiency
References
[1] S.C.A. Almieda, C.R. Belchior, M.V.G. Nascimento, L.S.R. Vieira, G. Fleury, Performance of
a diesel generator fuelled with palm oil, Fuel. 81 (2002) 2097-2102.
[2] A. Srivastava, R. Prasad, Triglycerides-based diesel fuels, Renew. Sust. Energ. Rev. 4 (2000)
111–133.
[3] F. Karaosmanoglu, G.O. Kurt, T. Zaktas, Longterm CI engine test of sunflower oil, Renew
Energ. 19 (2000) 219–231.
[4]. M.Z. Sulaiman, F.M. Isa, The effect of different gasoline blends doped with used engine oil on
the forming Tendency of simulated in take valve deposits, Proc. Inst. Mech. Eng. D J. (1999) 213.
[5] H.Z. Goetllen, M. Ziejewski, K.R. Kaufman, G.L. Pratt, Fuel injection anomalies observed
during long-burn engine performance test on alternate fuels, SAE Technical paper (1985) 852089.
[6] M.S. Graboski and R.L. McCornimik, Combustion of fat and vegetable oil derived fuels in
diesel, Prog. Energ. Combust. 24 (1998) 125–164.
[7] A. Isigigur, F. Karaosmanoglu, H.A. Aksoy, F. Hamdullahpur, L.O. Gulder, Performance and
emission characteristics of a diesel engine operating on sunflower seed oil methylester, Appl.
Biochem. Biotechnol. 45/46 (1994) 93–102.
[8] R. Altin, S. Cetinkaya, H.S. Yucesu, The potential of using vegetable oil fuels as fuel for diesel
engines, Energ. Convers. Manage. 42 (2001) 529–538.
[9] H. Raheman, S.V. Ghadge, Performance of diesel engine with biodiesel at varying compression
ratio and ignition timing, Fuel. 87 (2008) 2659–2666.
[10] K. Muralidharan, D. Vasudevan, Performance, emission and combustion characteristics of a
variable compression, Appl. Energ. 88 (2011) 3959-3968.
Applied Mechanics and Materials Vol. 388 245
Advances in Thermofluids 10.4028/www.scientific.net/AMM.388 Characterization of Diesel Engine Generator Operating at Different Compression Ratio Fuelled with
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DOI References
[1] S.C.A. Almieda, C.R. Belchior, M.V.G. Nascimento, L.S.R. Vieira, G. Fleury, Performance of a diesel
generator fuelled with palm oil, Fuel. 81 (2002) 2097-2102.
http://dx.doi.org/10.1016/S0016-2361(02)00155-2 [2] A. Srivastava, R. Prasad, Triglycerides-based diesel fuels, Renew. Sust. Energ. Rev. 4 (2000) 111–133.
http://dx.doi.org/10.1016/S1364-0321(99)00013-1 [3] F. Karaosmanoglu, G.O. Kurt, T. Zaktas, Longterm CI engine test of sunflower oil, Renew Energ. 19
(2000) 219–231.
http://dx.doi.org/10.1016/S0960-1481(99)00034-8 [7] A. Isigigur, F. Karaosmanoglu, H.A. Aksoy, F. Hamdullahpur, L.O. Gulder, Performance and emission
characteristics of a diesel engine operating on sunflower seed oil methylester, Appl. Biochem. Biotechnol.
45/46 (1994) 93–102.
http://dx.doi.org/10.1007/BF02941790 [8] R. Altin, S. Cetinkaya, H.S. Yucesu, The potential of using vegetable oil fuels as fuel for diesel engines,
Energ. Convers. Manage. 42 (2001) 529–538.
http://dx.doi.org/10.1016/S0196-8904(00)00080-7 [9] H. Raheman, S.V. Ghadge, Performance of diesel engine with biodiesel at varying compression ratio and
ignition timing, Fuel. 87 (2008) 2659–2666.
http://dx.doi.org/10.1016/j.fuel.2008.03.006 [10] K. Muralidharan, D. Vasudevan, Performance, emission and combustion characteristics of a variable
compression, Appl. Energ. 88 (2011) 3959-3968.
http://dx.doi.org/10.1016/j.apenergy.2011.04.014