Effect of injection pressure on the emission characteristics of a diesel engine using diesel

1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 6, Issue 1, January (2015), pp. 27-34 © IAEME
27
EFFECT OF INJECTION PRESSURE ON THE EMISSION
CHARACTERISTICS OF A DIESEL ENGINE USING
DIESEL-RICE BRAN BIODIESEL BLENDS
Dr G Venkata Subbaiah
Mechanical Engineering Department, MVSR Engineering College, Nadergul, Hyderabad, India
ABSTRACT
Biodiesel as alternative fuel has been widely studied due to its merits such as lower sulfur,
lower aromatic hydrocarbon and higher oxygen content. Rice bran oil is extracted from the germ and
inner husk of the rice and is not a common source of edible oil. The aim of this paper is to study the
effect of injection pressure on the emission characteristics of a single cylinder diesel engine using
diesel and the blends of diesel and rice bran biodiesel, B10 (90% diesel + 10% rice bran biodiesel),
B20 (80% diesel + 20% rice bran biodiesel) and B30 (70% diesel + 30% rice bran biodiesel). The
injection pressure is varied from 180 bar to 240 bar with an interval of 20 bar. The exhaust gas
emissions such as carbon monoxide (CO), hydrocarbon (HC), oxides of nitrogen (NOx), carbon
dioxide (CO2) and smoke opacity are measured at the rated power and speed at different injection
pressures. It is observed that the minimum CO, HC and smoke emissions are recorded at 220 bar.
The NOx, emissions are increased and CO2 emissions decreased with the injection pressure. The
optimum injection pressure is 220 bar and the blend is B20 with respect to emissions.
Keywords: Diesel engine, injection pressure, emissions, rice bran biodiesel
1. INTRODUCTION
Compression ignition engines are employed particularly in the field of heavy transportation
and agriculture on account of their higher thermal efficiency and durability. The diesel engines are
the major contributors of oxides of nitrogen and particulate emissions [1]. Rice Bran Oil (RBO) is
extracted from the germ and inner husk (called bran) of the rice. Rice bran is mostly oily inner layer
of rice grain which is heated to produce RBO [2]. RBO is not a common source of edible oil
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compared to other traditional cereal or seed sources such as corn, cotton, sunflower or soybean. .
Until recently, rice bran was used mostly as animal feed and the most of the oil production is used
for industrial applications. One of the best ways for the potential utilization of RBO is the production
of biodiesel [3]. In recent years the efforts have been made by several researchers for the
compatibility of pure rice bran oil in diesel engines [4,5].
D. Harshavardhan reported that the performance of a diesel engine in terms of brake thermal
efficiency and brake specific fuel consumption improved; HC and NOx emissions were reduced by
the use of rice bran biodiesel blends [6]. Perminderjit Singh and Randeep Singh investigated the
effect of compression ratio in a direct injection diesel engine running on different blends of rice bran
biodiesel and ethanol. The blends when used as fuel resulted in reduced CO, HC and increased NOx
emissions [7]. Syed Shakier and M. C. Navindgi found that the performance of the blend RB20 gave
the results nearer to the diesel fuel and CO, HC, CO2, HC, smoke & NOx emissions of this blend
were less than that of diesel [8]. This literature reveals that the rice bran biodiesel can be used as an
alternate fuel for a diesel engine.
The researchers [9-11] studied the effect of injection pressure on the emission characteristics
of a diesel engine using diesel and diesel-jatropha biodiesel blends. The injection pressure was varied
from 160 to 240 bar and observed that the BTE, EGT, NOx, CO2 and O2 emissions increased & bsfc,
CO. HC and smoke emissions reduced with the injection pressure. The optimum injection pressure
was 200 to 220 bar. The effect of injection pressure on the emission characteristics of a diesel engine
using pomgamia pinnata blends with diesel reported that CO, HC and smoke emissions reduced but
NOx emissions increased with injection pressure [12-14]. The effect of injection pressure on the
emission characteristics of a diesel engine is studied by using different biodiesels such as biodiesel
from waste cooking oil, chicken fat rubber seed oil, soybean etc. It is reported that Co, CO2, HC
emissions reduced and NOx emissions reduced with injection pressure and the optimum injection
pressure was in the range of 200-210 bar [15-17].
The above literature reveals that the injection pressure has an influence on the emission
characteristics of a diesel engine using different biodiesels. There is little literature found on the
study of effect of injection pressure on the emission characteristics of a diesel engine using rice bran
biodiesel. Hence the objective of this paper is to investigate the effect of injection pressure on the
emission characteristics of a direct diesel engine using diesel and rice bran biodiesel blends.
2. MATERIALS & METHODS
In the present study the fuels used are conventional diesel fuel and rice bran biodiesel. The
diesel fuel was purchased from the Bharat Petroleum pump outlet, Nandyal, Andhra Pradesh and the
rice bran oil biodiesel (RBD) was supplied by Gaiatech Fuels Pvt. Ltd; Hyderabad, India. The fuel
properties of diesel and rice bran biodiesel such as density, viscosity, calorific value, net heating
value, auto-ignition temperature, pour point, cetane number, iodine number, acid value and oxygen
content are measured and observed that they are in the standard limits of diesel engine fuels. The
schematic diagram of the engine test rig is shown in Fig1.The set up consists of diesel engine,
electrical alternator, fuel tank, fuel burette, exhaust gas analyzer and a smoke meter.

3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 6, Issue 1, January (2015), pp. 27-34 © IAEME
29
Figure 1. schematic diagram of experimental setup.
The specifications of the engine are given in the Table 1.
Table 1. Specifications of the Diesel Engine
Make Kirloskar model AV1
No. of Strokes per cycle 4
No. of Cylinders single
Combustion chamber position vertical
Cooling method Water cooled
Starting condition Cold start
Ignition technique Compression ignition
Bore (D) 80 mm
Stroke ( L ) 110 mm
Rated speed 1500 rpm
Rated power 5 hp (3.72 kW)
Compression ratio 16.5 : 1
Injection opening pressure 200 bar
The engine was connected to electrical dynamometer for measuring brake power. The
naturally aspirated engine was provided with water cooling system. The engine oil was provided
with a pressure feed system. The engine was first operated on diesel fuel with no load for about 15
minutes until the cooling water and lubricating oil temperatures reaches to 850
C at rated speed of
1500 rpm and the original injection pressure of 200 bar. The CO, HC, NOx, CO2 emissions were
measured with the help of AVL Digas 444 exhaust analyser and the smoke opacity was measured by
using AVL smoke meter 437C. The baseline parameters were obtained at rated load on the engine
with the diesel fuel (Diesel). After this, the diesel fuel was replaced by diesel-rice bran biodiesel
blends B10 (90% diesel and 10% rice bran biodiesel), B20 (80% diesel and 20% rice bran biodiesel)

4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 6, Issue 1, January (2015), pp. 27-34 © IAEME
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0
0.2
0.4
0.6
0.8
1
1.2
160 180 200 220 240 260
CarbonMonoxide(%vol)
Injection Pressure (bar)
Diesel
B10
B20
B30
and B30 (70% diesel and 30% rice bran biodiesel) one after the other and the emissions are
measured. The injection pressure was adjusted to and calibrated to 180bar, 220 bar and 240 bar in the
fuel injector and the same tests were conducted with diesel, B10, B20 and B30 at each of these
injection pressures. The results obtained for diesel-rice bran biodiesel blends at different injection
pressures were compared with the baseline parameters obtained during engine fuelled with diesel
fuel at rated speed of 1500 rpm.
3. RESULTS& DISCUSSIONS
The exhaust gas emissions measured for the diesel fuel and its blends with rice bran biodiesel
are demonstrated with the help of graphs and discussed as follows.
The variation of carbon monoxide emissions with injection pressure is shown in the Fig 2.
The CO emissions are decreasing for the blends B10 and B20 but increasing for the blend B30.
Carbon monoxide emission from a diesel engine mainly depends upon the physical and a chemical
property of the fuel. The bio diesel itself contains 11% of oxygen which helps for complete
combustion resulting in reduced CO emissions. The CO emissions decrease with injection pressure
up to 220 bar and recording the minimum values for all the fuel samples tested. The CO emissions of
B10, B20 and b30 are 16.92%, 40.12% and 29.98% respectively lower than that of diesel fuel at 220
bar injection pressure. The CO emissions are increasing when injection pressure is raised from 220
bar to 240 bar.
Figure 2. Variation of carbon monoxide emissions with injection pressure
The variation of hydrocarbon emissions for diesel fuel, B10, B20 and B30 is shown in the
Fig.3. The HC emissions are decreasing with the increasing percentage of rice bran biodiesel in the
blends. At the rated injection pressure of 200 bar, the HC emissions of B10, B20 and B30 are
respectively 7.07%, 19.19% and 23.23% lower than that of diesel fuel.. The presence of oxygen in
the fuel was thought to promote complete combustion that leads to lowering the HC emissions.
These reductions indicate more complete combustion of the fuel. The HC emissions of the blends
B10, B20 and B30 are decreasing with the injection pressure up to 220 bar. The minimum values are
observed at 220 bar injection pressure. The HC emissions for these blends are high at 240 bar
injection pressure which may be because of finer spry which reduces momentum of the droplets
resulting in less complete combustion.

5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 6, Issue 1, January (2015), pp. 27-34 © IAEME
31
0
20
40
60
80
100
120
160 180 200 220 240 260
Hydrocarbons(ppm)
Injection Pressure (bar)
Diesel
B10
B20
B30
700
750
800
850
900
950
1000
160 180 200 220 240 260
Oxidesofnitrogen(ppm)
Injection Pressure (bar)
Diesel
B10
B20
B30
Figure 3. Variation of hydrocarbon emissions with injection pressure
The NOx emissions variation for diesel fuel, B10, B20 and B30 with injection pressure is
shown in the Fig 4. The NOx emissions increase with the increasing percentage of rice bran biodiesel
in the blends. It is due to the addition oxygen provided by the biodiesel for the formation of NOx
emissions. The NOx emissions of B10, B20 and B30 are respectively 1.485%, 3.54% and 5.62%
higher than that of diesel fuel at rated injection pressure of 200 bar. The NOx emissions increase
with injection pressure for all the fuels tested. As the injection pressure increases, the temperature of
combustion chamber increases and NOx formation is a strongly temperature dependent phenomenon.
Figure 4. Variation of Oxides of nitrogen emissions with injection pressure.
The variation of carbon dioxide emissions with injection pressure for diesel and its blends
with rice bran biodiesel are shown in the Fig 5. The CO2 emissions are increasing with the amount of
rice bran biodiesel in the blends. The CO2 emissions of B10, B20 and B30 are respectively 1.1%,
2.1% and 2.3% higher than that of diesel at 200 bar. The CO2 emissions are decreasing with the
injection pressure.

6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online), Volume 6, Issue 1, January (2015), pp. 27-34 © IAEME
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11
11.1
11.2
11.3
11.4
11.5
11.6
11.7
11.8
11.9
12
160 180 200 220 240 260
Carbondioxide(%vol)
Injection Pressure (bar)
Diesel
B10
B20
B30
Figure 5. Variation of carbon dioxide emissions with injection pressure
The variation of smoke opacity with injection pressure for diesel and diesel-rice bran
biodiesel blends is shown in the Fig 6. The smoke opacity is increasing with the addition of rice bran
biodiesel up to 20% to the diesel fuel. The smoke opacity of B10, B20 is respectively 1.91% and
4.05% lower than that of diesel at 200 bar. The smoke opacity of B30 is greater than that of B20 at
all injection pressures. The Smoke opacity is increasing with the injection pressure up to 220 bar and
increasing at 240 bar for all the fuels tested. The minimum smoke opacity is observed with B20 at
220 bar and it is 4.9% lower than that of diesel fuel at original injection pressure of 200 bar.
Figure 6. Variation of smoke opacity with injection pressure
4. CONCLUSION
The experimental study on the effect of injection pressure on emission characteristics of a
diesel engine is conducted by using diesel and its blends with rice bran biodiesel and the following
conclusions are drawn.
40
41
42
43
44
45
46
47
48
49
50
160 180 200 220 240 260
SmokeOpacity(%)
Injection Pressure (bar)
Diesel
B10
B20
B30

7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
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The CO and HC emissions are well reduced by increasing the injection pressure for all fuels
tested.
The NOx emissions are increasing with the increasing percentage of biodiesel in the blends
and also with injection pressure for all the fuels tested.
The smoke opacity is decreasing up to 220 bar but increasing at 240 bar for all the fuels.
The CO2 emissions are increasing with both the injection pressure and the percentage of rice
bra biodiesel in the blends.
The optimum fuel blend is B20 and the optimum injection pressure is 220 bar with respect to
the emissions.
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