POSTER PAPER
International Journal of Recent Trends in Engineering, Vol. 1, No. 5, May 2009
Influence of Injection Timing on Performance
and Emission Characteristics of Naturally
Aspirated Twin Cylinder CIDI Engine Using
Bio-diesel Blend as Fuel
M. Pandian1, S.P. Sivapirakasam2 and M. Udayakumar3
1
Research scholar, Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli. 620015,
India. email: kalaipands@yahoo.com
2
Assistant Professor, Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli.
620015, India. email: spshivam@nitt.edu
3
Professor, Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli. 620015, India.
email: muday@nitt.edu
Abstract---Stringent emission norms and environment
degradation due to pollutants from the automotive vehicles
lead us to find the suitable alternative for the petro-diesel.
Among the alternatives the non-edible vegetable oil seems to
be most promising one. When the vegetable oil is used as
fuel in diesel engine, it does not cause any major problem if
used for a short period. However in the long run it causes
major problems such as injector coking, deposit build up in
the combustion chamber, piston ring sticking and engine oil
dilution. Hence vegetable oils are converted as biodiesels to
reduce viscosity. The transesterification process has proved
as one of the best method to achieve the same. It is evident
from the literature that the major problem on utilization of
blends of bio-diesel is the increase in NOx emission from
diesel engines. To reduce the NOx emission from the diesel
engines employing biodiesel blend as fuel, the injection
timing of fuel is altered by either addition or removal of
shims in the pump. The effect of changing the injection
timing on BSEC, Brake Thermal Efficiency, CO, HC and
NO emissions are studied at different injection timings such
as 18°, 21°, 24°, 27° and 30° CA bTDC. From the
experiments it is found that on retarding the injection to
18°CA bTDC from 24° CA bTDC, the original injection
timing, the NOx emission reduced to about 35% while
advancing to 30°CA bTDC, the NOx increased by 25%. The
BSEC, CO, HC have been found to increase by about 3%,
12.65% and 10% respectively on retarding to 18°CA bTDC
while decrease by 6.27%, 32%,and 14.44% respectively on
advancing the injection to 30° CA bTDC. The brake
thermal efficiency is reduced by 3.08% on retarding to
18°CA bTDC whereas it is improved by 5.09% on
advancing the injection timing to 30° CA bTDC.
Keywords: Injection timing, NOx emission, CIDI
engine, twin cylinder.
I. INTRODUCTION
Ever increasing prices of the petro-products,
stringent emission norms and fast depletion of fossil
fuel reserves forced to look for alternative fuels which
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should not only be sustainable but also environment
friendly. Of the several alternative fuels, non-edible
vegetable oil holds good promises as an eco-friendly
fuel. In India, there are several non-edible oil plants
such as jatropha, pongamia, neem, mahua, simarouba,
etc. Out of these plants, jatropha and pongamia have
shown good promise for biodiesel production [1]. Most
research works were reported on the performance and
emission test of diesel engine employing pongamia
biodiesel as fuel in different proportions without any
engine modifications and reported that smoke, HC, CO
emissions were found to be lower with higher BTE for
B10, B20 and B40 biodiesel blends[3] - [7]. However
in almost all the literature it was reported that NOx
emission was higher for biodiesel than diesel due to
higher oxygen content of the fuel [4] – [7].
Nevertheless, to improve the performance of the
engine researchers also employ engine modifications
such as alteration in fuel injection timing, injection
pressure, nozzle specification. Lot of work had been
done on alteration of injection timing for straight
vegetable oils and other fuels, few work has been
reported for biodiesel [8] – [13]. Therefore this paper
aims to study the influence of injection timing on the
performance and emission characteristics of the diesel
engine using biodiesel blend of B40 as fuel.
II. EXPERIMENTAL SETUP AND PROCEDURE OF
EXPERIMENTATION
The engine tests were conducted on four stroke twin
cylinder direct injection water cooled compression
ignition engine. The engine was always operated at its
rated speed of 1500 rev/min. The specification of the
engine is given in Table. 1
Pongamia bio-diesel and diesel were used to
prepare bio-diesel blend fuel. Pongamia biodiesel was
POSTER PAPER
International Journal of Recent Trends in Engineering, Vol. 1, No. 5, May 2009
obtained from M/s. Bannari Sugars (P) Ltd.,
Sathiyamangalam while diesel was purchased from a
commercial supplier.
TABLE 1:
TEST ENGINE SPECIFICATIONS
Parameters
Specification
Machine
supplier
Niyo Engineers, Pune
Make
Rocket Engineering Corporation,
Kohlapur, Maharashtra
Nozzle opening
pressure
200 bar
No. of cylinders
2
Fuel
H.S. Diesel
A series of experiments were conducted using biodiesel blend as fuel under varying load conditions at the
rated speed. The fuel blend was prepared just before
starting the experiment to ensure that the fuel mixture
was homogenous. The engine had an original injection
timing of 24° CA bTDC. The tests were carried out at
five different injection timing (18°, 21°, 24°, 27°, and 30°
CA bTDC) values with decreasing or increasing the
advance shim [9]. In each test, the values of time for 40
cc of fuel consumption, air flow rate, voltmeter, ammeter,
the ambient temperature and the exhaust gas temperature
were noted from the digital display. Also the values of
pollutants such as CO, HC, CO2, and NOx were recorded
during the tests. For notifying the exhaust emissions,
AVL 5 gas analyzer and AVL Smoke meter were used.
All the data were recorded after the engine attained
steady state. The experimental setup is shown in Fig. 1.
7.5 kW
Rated Power
Cylinder size
80 mm Bore & 110mm Stroke
Compression
ratio
17.5
Dynamometer
Alternator with Heater load
Injection timing
24°CA bTDC
The properties of blend fuel B40 were shown in Table2
with the properties of diesel for comparison.
TABLE 2:
PROPERTIES OF BLENDED FUEL AND DIESEL
Fig. 1.
Parameters
diesel
B40
Kinematic viscosity @ 40°C
(cSt)
2.6
3.85
Cetane No
50
51
Iodine Value
NA
41
Calorific Value (MJ/kg)
42.5
40.1
Specific Gravity @ 15° C
0.835
0.859
Flash point °C
68
81
III. RESULTS AND DISCUSSION
It was reported in many literature that NOx emission
was higher for Bio-diesel blend fuel while CO, HC
emissions were lower. One such measure to reduce the
NOx emission from diesel engine is to retard the fuel
injection timing. The fuel injection timing was adjusted
to study its impact on Brake Specific Energy
Consumption (BSEC), Brake Thermal Efficiency (BTE),
CO, HC and NOx for the blend fuel of B40 from a
Naturally Aspirated Twin cylinder CIDI engine.
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Experimental Setup
POSTER PAPER
International Journal of Recent Trends in Engineering, Vol. 1, No. 5, May 2009
B. Effect on brake thermal efficiency (BTE)
From the fig. 3, it was found that there was 5.07%
increase in brake thermal efficiency when injection
timing was advanced to 30°CA bTDC but about 3.08%
decrease while retarded to 18°CA bTDC. This was also
due to improved combustion when advancing the
injection timing and poor combustion while retarding.
C. Effect on NOx Emission
Fig. 4 showed that as load increased from 0% to 100%,
the NOx emission increased at different injection timings.
This is due to the fact that as the load increased to the
maximum value the fuel consumption with higher oxygen
content also proportionately increased which lead to the
higher NOx emission.
Fig. 2. Variation of BSEC vs. load
A. Effect on BSEC
From fig. 2 it is clearly seen that BSEC increased by
3.11% on advancing the injection timing to 30°CA bTDC
while reduced by 5% on retarding to 18°CA bTDC from
the original injection timing of 24° CA bTDC. Because of
advancing the injection of fuel to 30°CA bTDC, complete
combustion would have been taken place that results in
lesser BSEC. While retarding the injection to 18°CA
bTDC, combustion is incomplete that results in higher
BSEC.
Fig. 4. Variation of NOx Vs Injection timing.
It was also found that at each load the NOx emission
increased as the injection timing was advanced to 27° CA
bTDC and 30° CA bTDC from the original injection
timing of 24° CA bTDC whereas on retarded to 21° CA
bTDC and 18° CA bTDC the NOx emission was reduced.
Because:
i)
As the injection timing was advanced to 27° and
30° CA bTDC, mostly all the injected fuel is burnt before
TDC. i.e during the progress of the compression stroke.
Hence high peak temperature resulted which led to higher
NOx emission.
ii)
When the injection timing was retarded to 21°
and 18° CA bTDC, only part of the fuel burnt before
TDC and the remaining fuel burnt in early expansion
stroke resulting in less peak temperature. Hence NOx
emission lowered.
Fig.3. BTE Vs Load
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POSTER PAPER
International Journal of Recent Trends in Engineering, Vol. 1, No. 5, May 2009
D. Effect on CO emission
IV. CONCLUSIONS
Fig. 5 shows the variation of CO for various injection
timings at different loads. About 12.65 % increase in CO
emissions was observed on retardation while 32%
reduction was noticed on advancement of fuel injection.
On advancement the fuel blend had sufficient time to
undergo the combustion process whereas it had lesser
time on retardation.
The BSEC increased by 3.11% on advancing the
injection timing to 30° CA bTDC and got reduced by
6.27% while retarding the injection timing to 18° CA
bTDC. Also it was found that the brake thermal
efficiency (BTE) improved by 5% on advancing the fuel
injection and reduced by 3.08% during retardation. On
advancing the injection timing by 6° CA bTDC from the
original injection timing, the NOx emission increased by
25% while the NOx emission reduced by 35% when
retarded by 6° CA bTDC. The CO and HC emissions
were reduced by 32% and 14.44% respectively when
advancing the injection timing to 30°CA bTDC and
increased by 12.65% and 10% respectively on retardation
to 18°CA bTDC.
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Fig. 5
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