THE PERFORMANCE OF BIODIESEL MIXTURES IN A VCR ENGINE

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International Journal of Advanced Research in Engineering and Technology
(IJARET)
Volume 6, Issue 8, Aug 2015, pp. 32-41, Article ID: IJARET_06_08_004
Available online at
http://www.iaeme.com/IJARET/issues.asp?JTypeIJARET&VType=6&IType=8
ISSN Print: 0976-6480 and ISSN Online: 0976-6499
© IAEME Publication
___________________________________________________________________________
THE PERFORMANCE OF BIODIESEL
MIXTURES IN A VCR ENGINE
Biju Cherian Abraham
Associate. Professor, Department of Mechanical Engineering, Mar Athanasius
College of Engineering, Kothamangalam, Ernakulum, India
S. Sathyajith
M Tech Scholar, Department of Mechanical Engineering, Mar Athanasius College of
Engineering, Kothamangalam, Ernakulum, India
ABSTRACT
In recent years alternate fuels have received much attention because the
world is confronted with the twin crisis of fossil fuel depletion and
environmental degradation. The biodiesel produced from Jatropha oil by
transesterification process represents one of the most promising options to
reduce the use of conventional fossil fuels. The present work studies the
performance and emission characteristics of a single cylinder water cooled
variable compression ratio engine using jatropha biodiesel and its mixtures as
fuel in a direct injection diesel engine. An additive DEE (Di-ethyl ether) is
used to enhance the combustion properties of biodiesel. A total of 3 samples
of fuels are used such as diesel, BD25 (Jatropha biodiesel 25%), BDM
(Biodiesel mixture). The performance and emission characteristics are
measured at compression ratios of 16, 17 and18 by varying the load and
maintaining the speed constant at 1500 rpm. From the study results it has
been found that better results are obtained at a compression ratio of 18. At
this best compression ratio the performance and emission characteristics of
biodiesel mixture is compared with BD 25 and Diesel Fuel (DF). It is
observed that the use of additive have improved the performance and emission
characteristics of biodiesel mixture and can be used as a substitute for diesel.
Key words: Alternate fuel, BD25, Biodiesel mixture, Variable Compression
Ratio and DEE
Cite this Article: Abraham, B. C. and Sathyajith, S. The Performance of
Biodiesel Mixtures in a VCR Engine. International Journal of Advanced
Research in Engineering and Technology, 6(8), 2015, pp. 32-41.
http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=6&IType=8
_____________________________________________________________________

The Performance of Biodiesel Mixtures in a VCR Engine
1. INTRODUCTION
The need for air quality improvements to cater latest pollution norms and the current
cost of crude oil demands the use of alternative fuels for automobiles/IC engines. The
past and the present day civilization are closely interwoven with energy and future;
our existence will be even more dependent upon it. The conventional sources of
energy are being depleted at a faster pace and the world is heading towards a global
crisis. The greatest task today is exploiting the non-conventional energy resources for
power generation.
The transesterification of low quality crude jatropha oil to biodiesel using
modified natural zeolite as a solid catalyst can be done and the effects of various
factors consist of the reaction time, molar ratio of methanol to oil, reaction
temperature, mass ratio of catalyst to oil and catalyst reusability can be
investigated[1]. Also Calcined sodium silicate can be used to rapidly catalyze the
transesterification of rapeseed and Jatropha oils to biodiesel under microwave
irradiation. By using calcinated sodium silicate biodiesel yields of 95.8% and 92.8%
were achieved from rapeseed and Jatropha oils, respectively [2]. The performance of a
diesel engine operated with Jatropha and Palm biodiesel blends at high idling
conditions HC and CO emissions of both blends decreases, however, NOx emissions
increases compared to pure diesel fuel [3]. Also when an emulsified fuel containing
10% and 15% water by volume, prepared from a diesel blend with 10% Jatropha
biodiesel (JB10) the combustion characteristics of a10.3 kW, single cylinder, 4-stroke,
water cooled, direct injection (DI) diesel engine showed considerable improvement
[4]. The effect of blending ratio and compression ratio on a diesel engine performance
using the different blends (B10, B20, B30, andB50) and normal diesel fuel (B0)
shows considerable improvement in performance and emission characteristics. The
compression ratio used varies from 16 to 18 [5].
2. EXPERIMENTAL SETUP AND PROCEDURES
In this experimental study the variable compression ratio engine was run with three
different fuels; diesel, BD25 ((25 % jatropha biodiesel + 75 % diesel)and BDM
(Biodiesel Mixture; DEE 5%, Jatropha biodiesel 25%, 3 ml raw rubber seed oil + 5%
rubber seed oil biodiesel) at different compression ratios varying from 16 to 18. The
chosen fuel for the study was biodiesel mixture (BDM). From the test the best
compression ratio for the chosen fuel was found out. Then the results were compared
with the diesel and jatropha biodiesel at that compression ratio.
2.1 Experimental Setup
The study was conducted in the laboratory on an advanced fully computerized
experimental engine test rig comprising of a single cylinder, water cooled, four stroke,
and VCR (variable compression ratio) diesel engine. “Figure 1” shows a single
cylinder, four stroke, VCR diesel engine connected to eddy current type dynamometer
for loading. The compression ratio can be changed only after stopping the engine. A
locknut arrangement is provided on the top of the cylinder head to change the clearance
volume thereby changing the compression ratio. The setup is provided with necessary
instruments for combustion pressure and crank-angle measurements. These signals are
interfaced to computer through engine indicator for Pθ − PV diagrams. Provision is also
made for interfacing airflow, fuel flow, temperatures and load measurement. The set up
consists of a standalone panel box consisting of air box, two fuel tanks for duel fuel test,
manometer, fuel measuring unit with sensors and fuel module, transmitters for air and

Biju Cherian Abraham and S. Sathyajith
fuel flow measurements, process indicator and engine indicator. Rotameters are
provided for cooling water and calorimeter water flow measurement. ‘K’ type
thermocouples are used to measure the corresponding temperatures.
Figure 1 Experimental setup
Engine Performance Analysis software package “Engine Test Express V 5.76” is
used for line performance evaluation. The specifications of the engine and
dynamometer are given in “Table 1”.
Table 1 Engine and Dynamometer Specification
Engine specification Dynamometer Specification
Make Legion Brothers Type Eddy current
No. of Cylinder Single Make Power Mag
Cubic Capacity 553 cc Load Measurement method Strain Gauge
Cooling Water Max. Speed 1500 rev/min
Fuel Diesel HP 5 HP
Speed 1400–1500 rpm Coupling Type Direct
HP 5 HP Cooling Air
Starting Crank Type Eddy current
Lubrication Forced
The exhaust gases were sampled from exhaust line through a specially designed
arrangement for diverting the exhaust to sampling line without increasing the back
pressure and was then analysed using a portable gas analyzer (make –AVL digas 444).
The gas analyzer measures carbon monoxide (CO), carbon dioxide (CO2),
hydrocarbons (HC), oxygen (O2) and nitrogen oxide emissions (NOx).
2.2 Fuel Used
All the biodiesel are procured from Southern Biotechnology Pvt Ltd, Chennai. The
fuels used in the study are diesel, Jatropha biodiesel, Rubber seed oil biodiesel,
Rubber seed oil. In addition an additive DEE (di-ethyl ether) is used to improve the
properties of biodiesel. There are three combinations of fuel used in the study; BD0
(Pure diesel), BD25 (25% jatropha biodiesel) & biodiesel mixture BDM (DEE 5%,
Jatropha biodiesel 25%, 3 ml raw rubber seed oil + 5% rubber seed oil biodiesel.).
“Table 2” shows the various properties of fuel used for the study. In this study main
focus is given to BDM (biodiesel mixture).

Table 2 Properties of fuels
Properties Jatropha biodiesel
Biodiesel
mixture
Diesel
Density, g/ml 0.865 0.88 0.841
Viscosity @ 40 °C, cSt 5.2 5.6 4.5
Calorific Value, MJ/kg 39.2 40.0 42.0
Flash point, °C 175 160 50
Cloud point, °C 13 12 9
2.3 Experimental procedures
Initially the engine was started at no load condition for a compression ratio of 16. The
experiment was carried out by maintaining the speed constant at 1500 rpm and varying
the load. A self governing mechanism was used for adjusting speed. All the performance
and emission characteristics of the three fuel proportions were recorded before shifting to
next compression ratio. The same procedure was conducted for compression ratios 17 &
18. From the base results it has been found that the better results for BDM (biodiesel
mixtures) is obtained for a compression ratio of 18. The final results of BDM were
compared with BD 25 & Diesel at CR 18. The performance of the engine at different
loads and settings was evaluated in terms of SFC, BTE, volumetric efficiency,
mechanical efficiency and emissions of carbon monoxide, carbon dioxide, un-burnt
hydrocarbon, oxygen, and nitrogen oxides. The SFC is evaluated by the software on the
basis of fuel flow and brake power. Similarly, BTE is also evaluated by software.
3. RESULTS AND DISCUSSIONS
3.1 Performance
3.1.1 Average cylinder pressure
In a compression-ignition engine, the peak cylinder pressure depends on the burned
fuel fraction during the premixed burning phase, i.e. the initial stage of combustion.
The variations in the cylinder pressure with crank angle for all the blends at different
engine operating conditions are shown in “Figure 2”. It is clear that the peak pressure
increases as the engine load increases.
Figure 2 Average cylinder pressure Vs Crank Angle (Load = 0 Kg & 9 Kg)
0
20
40
60
80
-500 0 500
Averagecylinderpressure
(bar)
Crank Angle (deg CA)
Average cylinder pressure (bar) VS
Crank Angle (deg CA) 9kg
DIESEL
BD 25%
BDM
0
10
20
30
40
50
60
-500 0 500
Averagecylinderpressure,
Bar
Crank angle degree CA
Average cylinder pressure (Bar)VS
Crank angle(deg CA) 0 kg
DIESEL
BD 25%
BDM

The use of DEE as an additive improved the cetane number of biodiesel and
biodiesel mixtures also it is an excellent ignition enhancer and has low ignition
temperature thereby reducing the ignition delay.
3.1.2 Brake Thermal Efficiency
The variation of brake thermal efficiency with respect to brake power is shown in
“Figure 3”. It can be seen that for all the fuel samples the brake thermal efficiency
increases with brake power. It is seen that BTE is higher for biodiesel blends and
biodiesel mixtures when compared to diesel. The reasons for this improvement of
Brake thermal efficiency is better combustion and better lubricity of biodiesel. The
maximum brake thermal efficiency is obtained at a compression ratio of 18, due to the
superior combustion and better intermixing of the fuel. Also the use of the additive
DEE in biodiesel mixture has improved the calorific value and oxygen content of the
fuel which in turn increases the brake thermal efficiency.
3.1.3 Specific fuel consumption
SFC is an important parameter that reflects how good the engine performance is. The
variation of SFC with BP for different fuels is shown in “Figure 4”. Generally the SFC
decreases with increase in load due to fact that the ratio of increase in brake power is
more as compared to increase in fuel consumption. SFC is more for biodiesel mixture
and BD 25 due to lower calorific value of the biodiesel. For biodiesel mixture SFC is
close to diesel because DEE in the mixture has improved the calorific value of the fuel.
Figure 3 Brake Thermal Efficiency Vs BP
Figure 4 Specific fuel consumption Vs BP
0
10
20
30
40
0 2 4
Br.Thr.ɳ,%
BP, KW
Br.Thr.ɳ VS BP
DIESEL
BD 25%
BDM
0
0.2
0.4
0.6
0.8
0 2 4
SFC,KG/KWhr
BP,KW
SFC VS BP
DIESEL
BD 25%
BDM

3.1.4 Volumetric Efficiency
The volumetric efficiency of the diesel engine mainly depends upon the combustion
chamber temperature. “Figure 5” shows the variation of volumetric efficiency with
brake power. It is clear that for jatropha biodiesel blend the volumetric efficiency is
very low. The increase in availability of oxygen reduces the air intake. Biodiesel
mixture has higher volumetric efficiency when compared to biodiesel blend.
Figure 5 Volumetric Efficiency Vs BP
Figure 6 Mechanical Efficiency Vs BP
The reason is that DEE in biodiesel mixture decreases the combustion temperature
thereby decreasing the intake air temperature but the efficiency is lower when
compared to diesel.
3.1.5 Mechanical Efficiency
It has been observed that as the BP increases, mechanical efficiency for all the blends are
also increases in a steady rate. Biodiesel mixture has higher mechanical efficiency when
compared to BD 25 and diesel. The reason is that the presence of rubber seed oil in the
mixture increases the lubricating property of the fuel thereby reducing the frictional
power. “Figure 6” shows the variation of mechanical efficiency with brake power.
3.2 Emission
3.2.1 CO Emission
CO emissions are mainly due to incomplete combustion of fuel and it is produced
most readily from petroleum oils, which contain no oxygen in their molecular
structure. “Figure 7” shows the variation of CO emission with brake power. It is seen
75
80
85
90
0 2 4
Vol.ɳ
BP, KW
Vol.ɳ VS BP
DIESEL
BD 25%
BDM
0
20
40
60
80
0 2 4
Mech.ɳ,%
BP, KW
Mech.ɳ Vs BP
DIESEL
BD 25%
BDM

that with increase in BP the CO emission is lower for both BD25 and biodiesel
mixtures due to complete combustion of fuel taking place because of the availability
of extra amount of oxygen. It is seen that the biodiesel mixture has more CO emission
when compared to BD25. The reason is that Biodiesel mixture contains 5% rubber
seed biodiesel which produces more CO than BD 25%. But when compared with
diesel CO emission is much lower for biodiesel mixture due to complete combustion
of fuel taking place.
3.2.2 HC Emission
It can be observed that HC emissions decrease with increase in blend proportion at a
constant load. “Figure 8” shows the variation of HC emission with brake power. The
trend can be attributed to the higher oxygen content of Jatropha biodiesel and
biodiesel mixtures due to which complete combustion takes place inside the cylinder.
Figure 7 CO emission Vs BP
Figure 8 HC emission Vs BP
The HC emission of the jatropha biodiesel (BD25) and biodiesel mixture is less
than that of diesel fuel due to higher cetane number and inherent presence of oxygen
in the molecular structure of the jatropha biodiesel. The biodiesel mixture has more
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0 2 4
CO.%Vol
BP, KW
CO Vs BP
DIESEL
BD 25%
BDM
0
5
10
15
20
25
30
35
0 2 4
HC,ppmHex
BP, KW
HC VS BP
DIESEL
BD 25%
BDM

CO2 emission when compared to BD25 due to the presence of rubber seed oil
biodiesel in the mixture.
3.2.3 CO2 Emission
The higher CO2 emission in the exhaust of internal combustion engine is indication of
better combustion of fuel. “Figure 9” shows the variation of CO2 emission with brake
power. It is observed that the CO2 emission of jatropha biodiesel and biodiesel
mixture is higher than that of diesel fuel due to complete combustion of fuel taking
place because of the extra availability of oxygen. Biodiesel mixture contains DEE
which improves the cetane number of fuel leading to complete combustion.
3.2.5 NOx Emission
The mean high temperature inside the combustion chamber and availability of oxygen
are the two factors responsible for NOx emission. “Figure 10” shows the variation of
NOx emission with brake power. The jatropha biodiesel produces slightly more NOx
than diesel due to increase in oxygen content because biodiesel contain many mono-
unsaturated and poly-unsaturated fatty acids. Biodiesel mixture has lower NOx
emission when compared to BD 25% and diesel. This is due to the effect of the
additive DEE which reduces the mean temperature inside the combustion chamber
thereby reducing NOx emission.
Figure 9 CO2 emission Vs BP
Figure 10 NOx emission Vs Brake Power
4. CONCLUSION
The following conclusions are drawn from the study.
0
1
2
3
4
5
0 2 4
CO2,%Vol
BP, KW
CO2 VS BP
DIESEL
BD 25%
BDM
0
100
200
300
0 2 4
NOx,ppmVol
BP, KW
NOx Vs BP
DIESEL
BD 25%
BDM

Peak cylinder pressure is lower for biodiesel mixtures at higher and lower loads
due to decrease in delay period. The high in-cylinder temperature existing during fuel
injection, biodiesel may undergo thermal cracking resulting in lighter compounds
leading to shorter ignition delay.
Brake thermal efficiency for biodiesel mixture is higher than diesel and BD 25.
The reasons for this improvement of Brake thermal efficiency is better combustion
and better lubricity of biodiesel.
SFC is higher for biodiesel mixture and BD25 when compared to diesel due to
lower calorific value. But it has seen that SFC for BDM is almost close to diesel when
compared to BD25. The reason is that DEE in the mixture plays an important role in
increasing the cetane number and calorific value of the fuel.
Volumetric efficiency is found to be lower for biodiesel mixture with DEE which
may be due to the effect of higher thermal efficiency leading to increase in the density
of air sucked in.
Mechanical efficiency is higher for biodiesel mixture which may be due to
increase in lubrication effect of fuel. The rubber seed oil in the mixture enhances the
lubricity of the fuel and decreases the frictional power.
CO, HC emission is lower for biodiesel mixture because it contains extra amount
of oxygen for complete combustion of fuel.
CO2 emission is higher for biodiesel mixture due to complete combustion of fuel
taking place. All the unburned HC and CO are converted to CO2.
NOx emission is slightly lower for biodiesel mixture because DEE in the fuel
provides a cooling effect which reduces the mean gas temperature inside the
combustion chamber thereby reducing NOx emission.
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and hydrogen from rapeseed and Jatropha oils with sodium silicate and Ni
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