The document discusses the effect of varying compression ratio on the performance, emissions, and combustion characteristics of a diesel engine fueled with a blend of 70% honge oil and 30% ethanol. Experiments were conducted at compression ratios of 17, 17.5, and 18. Brake thermal efficiency and cylinder pressure increased with higher compression ratios due to more complete combustion. Emissions of unburnt hydrocarbons and carbon monoxide decreased with increasing compression ratio. The highest performance was observed at a compression ratio of 18.

1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME
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EFFECT OF VARIATION IN COMPRESSION RATIO ON
CHARACTERISTICS OF CI ENGINE FUELLED WITH HONGE OIL-
ETHANOL BLEND
Nandkishore D. Rao1
, Dr. B. Sudheer Premkumar2
and Jaganath.S3
1
Associate Professor, Department of Automobile Engineering, Guru Nanak Dev Engineering
College, Bidar- Karnataka.
2
Professor and Head of Mechanical Engineering, Jawaharlal Nehru Technological University,
Hyderabad, Andhra Pradesh- INDIA.
3
Assistant Professor, Department of Automobile Engineering, Guru Nanak Dev Engineering College,
Bidar- Karnataka .
ABSTRACT
This paper presents, the effect of variation of compression ratio on performance, emission
and combustion characteristics of diesel engine fuelled with Honge oil-ethanol blend. During
investigation, compression ratio is changed from 17 to 18 by titling the engine cylinder block. The
experimental results show improvement in brake thermal efficiency, increase in cylinder pressure
and reduction in unburnt hydrocarbon, carbon monoxide and smoke opacity with increase in
compression ratio. Whereas, decrease in compression ratio results in inferior performance
characteristics and higher emission profiles as compared to preset compression ratio.
Index Terms: Compression ignition engine, Honge oil, blend, brake thermal efficiency, oxides of
Nitrogen.
1. INTRODUCTION
India, the fastest and largest economy in the world depends on petroleum products for its
energy requirement, particularly, on diesel due to widespread use of diesel engines for transportation,
agricultural applications and industrial sectors. Presently, India imports major portion of its
petroleum requirement from oil producing countries, which greatly affects its economy. Also, use of
diesel as fuel contributes harmful gases like carbon monoxide, oxides of nitrogen, smoke, etc. to the
environment causing air pollution. To address the dual problem of scare availability of diesel fuel
and environment pollution problem, it is necessary to develop an alternate fuel which can be
produced indigenously and will have lesser impact on environment as compared to diesel. As an
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alternative to the diesel, non edible oils produced Honge, Honne, Neem, Jatropha, Karanja, Mahua,
Neem, etc. can be used for diesel engine. These plant species can be grown in forests and semi-arid
land which fulfills the energy requirement of farmers.
Use of straight vegetable oils for diesel engine is limited due to their very high viscosity and
presence of gum, etc. From literature, it is observed that engine performance with straight vegetable
oil is inferior as compared to diesel due to above mentioned factors. To improve the engine
performance, the vegetable oil can be modified to make it compatible with existing engine.
Alternatively, the engine hardware can be modified to make it suitable for vegetable oil based fuels.
Different methods like trans- estrification, blending it with diesel/ suitable solvent, etc. have been
tried to improve the properties of vegetable oil based fuels. The trans-estrification of vegetable oil
with alcohols produces its ester having properties very close to diesel. But, it involves the skilled
labor and additional logistical support which adds cost to the fuel. Blending of vegetable oil with
diesel negates the idea of complete replacement of diesel with vegetable oil based fuel. Vegetable
oil- alcohol blends can be used as fuel as complete replacement for diesel as blends can be prepared
on the site of application, it does not requires any additional logistical support and it can replace the
diesel to full extent.
The engine performance, emission and combustion characteristics mainly depends on quality
of the fuel, droplet size (injection pressure, nozzle diameter), rate of injection, spray pattern,
injection timing, combustion chamber geometry and compression ratio, etc. For diesel engine, the
compression ratio determines the state of air - fuel mixture at the end of compression which affects
the combustion phenomenon. At higher compression ratios, injection of fuel in air at higher
temperature and pressure, increase in density of air and lower air dilution by residual gases
accelerates the pre-flame reactions resulting in faster combustion. S. Jindal et al. [1] conducted
investigations on performance of diesel engine fuelled with jatropha methyl ester at different
compression ratio and injection pressure. The investigations were conducted at compression ratio of
16, 17 and 18. At each compression ratio, experiments were conducted at different injection pressure
(150 bar, 200 bar and 250 bar). The highest performance was delivered by the engine at 250 bar
injection pressure and compression ratio of 18. Increase in compression ratio resulted in increase in
hydrocarbon emissions and exhaust gas temperature and decrease in smoke and CO emissions preset
compression ratio. R. Anand et al. [2] used methyl ester of cottonseed oil and it’s blends with diesel
(in four different compositions of ester varying from 5% to 20% in steps of 5%). The investigations
were made to study the effect of change in compression ratio on diesel engine characteristics. The
tests were conducted on a single cylinder variable compression ratio diesel engine at a constant speed
of 1500 rpm. During tests, the compression ratio was varied between 15 to 17. For all test fuels the
engine performance in terms of brake thermal efficiency and emissions improved with increase in
compression ratio. Nitesh Mohite et al. [3] conducted study on performance characteristics of
variable compression ratio diesel engine with diesel-ethanol blends. The compression ratio was
varied from 15 to 18 without changing combustion chamber geometry. It was observed that with
increase in compression ratio improved the engine performance. Eknath R. Deore et al [4]
investigated the performance of single cylinder diesel engine fuelled with diesel and its blends with
ethanol. Increase in percentage of ethanol in blend resulted in higher specific fuel consumption with
lower thermal efficiency as compared to diesel due to lower calorific value of the blend. They also
observed that decrease in compression ratio caused deterioration brake thermal efficiency, increase
in brake specific fuel consumption and exhaust gas temperature. M. Venkataman and G.
Devaradjane [5] conducted experiments on diesel engine fuelled with diesel-pungam methyl ester
blends (PME10, PME20 and PME30) at different compression ratio, injection pressure and injection
timing. During experiments, compression ratio was raised from 16:1 to 19:1, injection timing was
advanced from 21°CA bTDC to 27°CA bTDC and injection pressure was increased from 200 bar to
240 bar. They observed improvement in engine performance with increase in compression ratio. At

3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME
359
compression ratio 19:1, engine performance improved as compared to compression ratio of 16 and
17.5 due to increase in peak pressure and combustion temperature. Highest brake thermal efficiency
was observed at 27°CA bTDC as compared to preset injection timing of 24°CA bTDC. This
improvement in BTE was due to occurrence of peak pressure closer to top dead centre and higher
heat release during short duration of combustion. Increase in brake thermal efficiency was observed
with increase in injection pressure due to injection of finer spray and better entrainment. The brake
thermal efficiency with PME20 at compression ratio of 19, injection timing of 27°CA bTDC and
injection pressure of 240 bar was even higher than diesel under similar condition.
In present investigation, an attempt is made to investigate the effect of compression ratio on
performance, combustion and emission characteristics of diesel engine fuelled with a blend of 70%
Honge oil and 30% pure ethanol (BHO-70). Various physical and chemical properties of BHO-70
are mentioned in table 1. Experiments are conducted on Variable Compression Ratio (VCR) diesel
engine at different compression ratios. The various performance parameters like brake thermal
efficiency, specific fuel consumption, exhaust gas temperature, emissions of CO, HC, NOx, and
smoke intensity and combustion characteristic like cylinder pressure and rate of heat release are
analyzed at compression ratio of 17,17.5 and 18.
2. EXPERIMENTAL SET- UP
Fig. 1 shows schematic diagram of engine test setup used for present investigation. The
Diesel engine used for investigations is a single cylinder, water cooled, constant speed, four stroke,
variable compression ratio diesel engine. It is connected to an eddy current dynamometer for loading.
Variation in compression ratio is done by tilting block method without changing combustion
chamber geometry. The engine is attached with necessary instruments and sensors for measurement
of cylinder pressure, injection pressure, crank angle, fuel consumption, exhaust gas temperature,
coolant temperature, etc. An individual piezoelectric pressure sensor is used for measurement of in-
cylinder pressure and fuel line pressure separately. Thermocouples are used for measurement of
exhaust gas temperature and cooling water temperature. Signals from above instruments and sensors
are sent to data acquisition system and to computer for further processing. The software is developed
to calculate engine performance characteristics like brake power, brake specific fuel consumption,
mechanical efficiency, brake and indicated thermal efficiency and combustion characteristics like net
rate of heat release, cumulative heat release, mass burnt fraction, etc. The engine specifications are
given in Table 2.
TABLE NO 1
FUEL PROPERTIES
Fuel Diesel BHO -70
Sp.gr. 0.83 0.86
Viscosity (cSt) 4.25 10.08
Flash point (°C) 79 37
Fire point (°C) 85 42
Calorific value (MJ/kg) 42.70 34.10

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
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TABLE NO 2
SPECIFICATION OF ENGINE
1
1-Test engine, 2-Eddy current dynamometer, 3-fuel burette, 4-Fuel filter, 5-Fuel injection pump, 6-
air box with U tube water Manometer, 7-TDC marker and speed sensor, 8- Data acquisition system
and loading device , 9-Exhaust gas calorimeter, 10-Smoke meter, 11-four gas analyzer, 12-computer,
13 & 14 Fuel tanks
Fig.1: Schematic diagram of experimental setup.
Sl.No Parameter Specification
1 Type Four stroke direct
injection single cylinder
diesel engine
2 Software used Engine soft 8.5
3 Injector opening
pressure
200 bar
4 Rated power 3.5 KW @1500 rpm
5 Cylinder diameter 87.5 mm
6 Stroke 110 mm
7 Compression ratio 12 to 18
8 Injection
pressure/advance
200 bar/23° bTDC
1
3
1
4
3
4
8
5
6
27
11 10
9
12

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3. EMISSION MEASUREMENT
The exhaust gas is sampled from exhaust pipe line and passed through a four gas analyzer for
measurement of carbon monoxide, carbon dioxide, unburnt hydrocarbon and oxides of nitrogen
present in exhaust gases. A smoke meter is used for measurement of smoke opacity. The
measurement range and accuracy of the exhaust gas analyzer and smoke meter is mentioned in
Table 3.
TABLE NO 3
Specification of Gas analyser and Smoke meter
4. RESULTS AND DISCUSSION
4.1 PERFORMANCE PARAMETERS
4.1.1 BRAKE THERMAL EFFICIENCY
The variation of brake thermal efficiency at different compression ratio is presented in fig. 2.
Increase in brake thermal efficiency is observed with increase in compression ratio from 17.5 to 18.
This is due to the fact that increase in compression ratio ensures more complete combustion due to
injection of fuel in higher temperature and pressure compressed air; better air-fuel mixing and faster
evaporation etc. Whereas, reduction in compression ratio to 17 resulted in lower brake thermal
efficiency due to lower compression temperature and pressure, slow combustion process and more
dilution by residual gases.
4.1.2 BRAKE SPECIFIC FUEL CONSUMPTION
The brake specific fuel consumption (BSFC) for BHO-70 is higher than diesel due to its
lower calorific value and incomplete combustion on account of its higher viscosity as compared to
diesel. Increase in compression ratio causes reduction in BSFC due to reduction in dilution of charge
by residual gases, increase in charge density, etc. which results in better thermal efficiency and
decrease in BSFC (Fig. 3). However increase in BSFC is observed with reduction in compression
ratio due to slow combustion process because of more charge dilution and lower compression
pressure and temperature, etc.
4.1.3 EXHAUST GAS TEMPERATURE
Fig. 4 shows variation in exhaust gas temperature with compression ratio. It is found that the
exhaust gas temperature decreases with increase in compression ratio and reduction in compression
ratio results in higher exhaust gas temperature as compared to preset compression ratio. Increase in
compression ratio increases the air temperature at the end of compression which accelerates the rate
of combustion, more complete combustion results in lower heat loss in exhaust gases. However, at
lower compression ratio, exhaust gas temperature increases due to slow combustion.
Machine Measurement Parameter Range Resolution
CO (Carbon Monoxide) 0-15% 0.01%
Gas Analyser CO2 (Carbon Dioxide) 0-19.9% 0.1%
NOx (Oxides of Nitrogen) 0-5000ppm 1ppm
HC(Hydrocarbon) 0-20000ppm 1ppm
Diesel smoke
meter
Opacity 0-99.9% 0.1%

6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
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4.2 COMBUSTION PARAMETERS
CYLINDER PRESSURE AND NET RATE OF HEAT RELEASE
Fig. 5 and fig. 6 presents the effect of compression ratio on cylinder pressure and net rate heat
release at full load condition respectively. With change in compression ratio, the in-cylinder pressure
and net rate of heat release changes due to change in air temperature and pressure at the time of fuel
injection and at end of compression stroke which affects the combustion process. The cylinder
pressure increases with increase in compression ratio and decreases with decrease in compression
ratio. This may be due to the fact that at higher compression ratio, increase in density of air fuel
mixture, better mixing of unburnt and brunt charge results in fast and efficient combustion.
However, at lower compression ratio, peak cylinder pressure decreases due to slower combustion
because of lower compression pressure, weak swirl, improper burnt and unburnt charge mixing, etc.
The maximum net rate of heat release in case of compression ratio 18 and 17 is higher than 17.5
compression ratio. Higher rate of heat release rate at CR of 18 is due to faster combustion, whereas
higher rate of heat release at CR of 17 may be due to injection of more quantity of fuel during longer
delay period and slow combustion.
4.3 EMISSION PARAMETERS
4.3.1 UNBURNT HYDROCARBON EMISSIONS
Fig. 7 shows variation in unburnt hydrocarbon emissions with compression ratio. Increase in
compression ratio increases the air temperature at the end of compression stroke, enhancement in
combustion temperature and reduction in charge dilution leads to better combustion and reduction in
hydrocarbon emissions. Increase in hydrocarbon emissions is observed with reduction in
compression ratio is due to slow combustion process.
4.3.2 CARBON MONOXIDE EMISSIONS
Fig. 8 shows the variation in carbon monoxide emissions at different compression ratios. It is
observed that increase in compression ratio results in lower carbon monoxide emissions due to better
combustion. At higher compression ratio, less dilution of charge by residual gases accelerates the
carbon oxidation to form carbon dioxide. Whereas, at lower compression ratio, the carbon monoxide
emissions are increased due to more dilution of fresh air with residual gases, lower compression
temperature and poor mixing of fuel air because of lower swirl intensity, etc.
4.3.3 CARBON DIOXIDE EMISSIONS
Fig. 9 shows the variation in carbon dioxide emissions at different compression ratio. The
CO2 emissions are increased with increase in compression ratio due to better combustion. Whereas at
lower compression ratio, carbon dioxide emissions are lowered due to slower and incomplete
combustion which is evident from above discussion.
4.3.4. OXIDES OF NITROGEN EMISSIONS
From Fig. 10, it is observed that the NOx emissions are increased with increase in
compression ratio. This may be due to the fact that increase in compression ratio increases the
combustion pressure and temperature which accelerates the oxidation of nitrogen to form oxides of
nitrogen. On the other hand at lower compression ratios, the combustion takes place during
expansion stroke which results in lower combustion temperature and pressure and lower NOx
emission.
4.3.5. SMOKE OPACITY
Fig. 11 shows effect of variation in compression ratio on smoke opacity at various loading
condition. It is observed that increase in compression ratio causes reduction in smoke opacity due to

7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME
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better combustion because of stronger swirl, increase in air temperature and pressure at the time of
combustion, etc. The smoke opacity at compression ratio of 18 is least as compared to other
compression ratios.
5. CONCLUSION
In present investigation, experiments are conducted to evaluate the effect of variation in
compression ratio on performance, combustion and emission characteristics of diesel engine fuelled
with Honge - ethanol blend. Trials at different compression ratios (17, 17.5 and 18) reveled that,
increase in compression ratio results in improvement in brake thermal efficiency, reduction in
emissions of hydrocarbon emissions, carbon monoxide emission and smoke opacity. Higher peak
cylinder pressure, rate of heat release and NOx emissions are also observed with increase in
compression ratio due to better combustion of fuel.
It can be concluded that the engine fuelled with blend BHO-70 performed better at
compression ratio of 18 as compared to other compression ratios.
Fig. 2 Variation in Brake thermal efficiency at Fig. 3 Variation in Specific Fuel
consumption at different compression ratio different compression ratio
Fig. 4 Variation in Exhaust Gas Temperature at Fig. 5 Variation in cylinder pressure at full
load different compression ratio condition at different compression ratio
0
0.2
0.4
0.6
0.8
1
1.2
0 0.8 1.7 2.5 3.2
BrakeSpecificFuel
Consumption(kg/kW-hr)
Brake Power(kW)
BHO-70 at 17 CR
BHO-70 at 17.5 CR
BHO-70 at 18 CR
0
5
10
15
20
25
30
0 0.8 1.7 2.5 3.2
BrakeThermalEfficiency(%)
Brake Power(kW)
BHO-70 at 17 CR
BHO-70 at 17.5 CR
BHO-70 at 18 CR
100
150
200
250
300
350
400
0 0.8 1.7 2.5 3.2
ExhaustGasTemperature(°C)
Brake Power(kW)
BHO-70 at 17 CR
BHO-70 at 17.5
BHO-70 at 18 CR
0
10
20
30
40
50
60
70
-50
-40
-31
-22
-13
-4
5
14
23
32
41
50
CylinderPressure(bar)
Crank Angle ( ° CA)
BHO-70 at 17 CR
BHO-70 at 17.5 CR
BHO-70 at 18 CR

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Fig. 6 Variation in Rate of heat Release at full load Fig. 7 Variation in Unburnt Hydrocarbon
condition at different compression ratio emissions at different compression ratio
Fig. 8 Variation in Carbon monoxide emissions Fig. 9 Variation in Carbon dioxide emissions
at different compression ratio at different compression ratio
Fig. 10 Variation in Oxides of Nitrogen at Fig. 11 Variation in Smoke Opacity at
different compression ratio different compression ratio
0
10
20
30
40
50
60
70
0 0.8 1.7 2.5 3.2
UnburntHydrocarbon
Emissions(ppm)
Brake Power(kW)
BHO-70 at 17 CR
BHO-70 at 17.5 CR
BHO-70 at 18 CR
0
2
4
6
8
10
12
0 0.8 1.7 2.5 3.2
CarbonDioxideemissions(
%)
Brake Power(kW)
BHO-70 at 17 CR
BHO-70 at 17.5 CR
BHO-70 at 18 CR
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0 0.8 1.7 2.5 3.2
Cabonmonoxide
emissions(%)
Brake Power(kW)
BHO-70 at 17 CR
BHO-70 at 17.5 CR
BHO-70 at 18 CR
100
150
200
250
300
350
400
0 0.8 1.7 2.5 3.2
OxidesofNitrogenEmissions
(ppm)
Brake Power(kW)
BHO-70 at 17 CR
BHO-70 at 17.5
BHO-70 at 18 CR
0
10
20
30
40
50
60
0 0.8 1.7 2.5 3.2
SmokeOpacity(%)
Brake Power (kW)
BHO-70 at 17 CR
BHO-70 at 17.5 CR
BHO-70 at 18 CR
-10
-5
0
5
10
15
20
25
30
35
40
-50
-35
-21
-7
7
21
35
49
63
77
91
105
119
NetRateofHeatRelease
(J/°CA)
Crank Angle (° CA)
BHO-70 at 17 CR
BHO-70 at 17.5 CR
BHO-70 at 18 CR

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