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EXPERIMENTAL ANALYSIS OF EMISSIONS AND
PERFORMANCE CHARACTERISTICS OF LPG FUELED SI
ENGINE AT VARIABLE COMPRESSION RATIOS
1
S M LAWANKAR, 2Dr.L.P.DHAMANDE, 3ALBELA H.PUNDKAR
1Assist.
Prof ,Government College of Engineering, Amravati
of Engineering andTechnology,Dhamangaon
3 Research Scholar, Government College of Engineering, Amravati
1,2,3Department of Mechanical Engineering,
2Principal,College
[email protected]
ABSTRACT-Alternative fuels for both spark ignition (SI) and compression ignition (CI) engines have become
very important owing to increased environmental protection concern, the need to reduce dependency on
petroleum and even socioeconomic aspects. The investigations have been concentrated on decreasing fuel
consumption by using alternative fuels and on lowering the concentration of toxic components in combustion
products. Realizing the gravity of the problem, steps are being taken to introduce better technologies, better fuel
quality, shift to environment friendly fuels. Alternative fuels like LPG, CNG, hydrogen etc has emerged as a
solution to depleting crude oil resources as well as to the deteriorating urban air quality problem. As a gaseous
fuel, gains from LPG have already been established in terms of low emissions of carbon monoxide,
hydrocarbon. Air-fuel ratio, operating cylinder pressure ignition timing and compression ratio are some of the
parameters that need to be analyzed and optimally exploited for better engine performance and reduced
emissions. In the present Study evaluates the performance and emission characteristics of a single cylinder,4 stroke, water-cooled, LPG fueled spark ignition engine at different compression ratio. The results obtained
show that the engine running on an LPG fuel system delivered a substantial improvement in power and torque
in a high-load condition. Conversion of the engine using LPG as fuel showed an average reduction of CO and
HC exhaust gas emissions in comparison to the original fuel.
Key words- Liquefied petroleum gas, emissions and performance characteristics, compression ratios, speed,
Spark ignition engine
1. INTRODUCTION
Oil reserve all over the world is depleting at an
alarming rate. In addition, the deteriorating quality of
air we breathe is becoming another great public
concern. Emissions of sulfur dioxide, hydrocarbons,
carbon monoxide, nitrogen oxides, lead, etc. have
stimulated scientists to find ways to reduce these
emissions because of their impact on human health
and ecological imbalance. These factors along with
the oil crisis in the 1970s have led scientists and
researchers to search for clean and environmentally
friendly alternatives to the conventional fuels used to
power internal combustion engines. Various
alternative fuels suited for spark ignition (SI) engines
can be classified as synthetic gasoline, alcohols, and
gaseous fuels according to the studies conducted by
Thring (1983) and Prausnitz et al., (1987). Gaseous
fuels in general are promising alternative fuels due to
their low cost, high octane number, high calorific
values, and lower polluting exhaust emissions (Badr
et al., 1989; Richard Stone, 1989; Beer, 2002).
During the last decade, gaseous fuels such as
liquefied natural gas (LNG) and liquefied petroleum
gas (LPG) have been widely used in commercial
vehicles, and promising results have been obtained in
terms of the fuel economy and exhaust emissions.
These results have also been confirmed by different
published works of Yamin (2002) and Johnson
(2003). Existing literatures of Bayraktar (2003),
Dagaut et al., (2003), and Selim (2004) on the use of
gaseous fuels as engine fuel have obtained for a
limited number of specific engines running at specific
conditions. For these reasons, in the present study,
detailed experimental investigations of a LPG fuelled
SI engine for a wide range of operating conditions
and at different compression ratios have been carried
out and compared with the gasoline. The
characteristic properties of LPG are compared with
gasoline in Table 1.
Table1Comparative Properties of LPG,Gasoline[3][4]
Sr.
No
1
2
3
4
Characteristics of
fuels
Chemical structure
Mole Weight
Octane number
Lower heating value
(MJ/Kg)
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LP
G
C3
H
588
Gasoline
C7H17/C4
to
114C12
110
46.
+
1
86-94
43.500
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Heat
of 426 307
5
Vapourization(KJ/Kg
6
Boiling Point (K)
231 468
)
8
Stoichiometric
15. 14.7
Density
at 507
9
737
air/fuel ratio
7
298K,kg/m3
10
Autoignition
771 531
o
11
Specific
Gravity
temperature
K 60° 0.8 0.72-0.78
F/60°
50.4 0.42
12
Flame Speed(m/s)
About 55% of the LPG processed
from natural gas
6
purification. The other 45% comes from crude oil
refining. LPG is derived from petroleum. LPG is
typically a mixture of several gases in varying
proportions. Major constituent gases are propane
(C3H8) and butane (C4H10), with minor quantities of
propane (C3H6), various butanes (C4H8), iso-butane,
and small amounts of ethane (C2H6). The composition
of commercial LPG is quite variable. Being a gas at
normal temperature and pressure LPG mixes readily
with air in any proportion[1].LPG and other gaseous
fuels have common properties that provide them
some advantages and disadvantages relative to the
gasoline.LPG with lower density and Stoichiometric
fuel-air ratio than other fuels,LPG can produce
specific fuel consumption and engine emissions.
Morever LPG can be used at high compression ratio
due to its high octane number and as consequence of
this property, engine performance, that is power and
thermal efficiency will be improved. However the
Autoignition temperature of LPG is higher than
others fuels so it is necessary provide high intake
pressure and temperature to ignite it. The properties
of LPG make it becoming a fuel for SI engine. The
most important drawback of LPG is that it reduces
the engine volumetric efficiency and hence the fresh
charge mass, which is mainly because of its rising
inlet temperature and entering the intake system in
the gaseous state[2][3]. In the present paper, the
experimental and emission results obtained for
gasoline and LPG are compared and conclusions and
recommendations are given.
2. EXPERIMENTAL
SET-UP
Figure 1 Experimental set up
cavity in piston combustion chamber ,four-stroke
spark ignition naturally aspirated engine with a
maximum rated power output of 2 kW at 1500
rev/min has a displacement of 661cc.For the purpose
the provision is made to conduct the experiment at
different compression ratio and with different fuels.
The detail specifications of the engine are listed in
Table 2. The test rig used in this work mainly
consists of the engine, direct current (DC)
dynamometer and AVL Di-Gas 5-gas analyzer. The
exhaust tailpipe from the engine was held by an
extended arm and the probe of the gas analyzer
was inserted into the exhaust tailpipe. AVL Di-Gas
analyzer probe was positioned at the exhaust
tailpipe for emission measurement. The analyzer
has the capability of sampling various exhaust
products such as hydrocarbon (HC), carbon
monoxide (CO), and carbon dioxide (CO2) with
the option of oxygen (O2), oxides of nitrogen
(NOx) and air-fuel ratio(λ). Even though it was
possible to vary the engine speed, in this study,
however, it was run at a constant speed of 1500
rev/min, Since the spark ignition engine is equipped
with a carburetor, it has to be added with an adaptor
for bi-fueling purpose when running with gaseous
fuel of
LPG
and gasoline. Throughout the
experiments the air control valve was fully opened. A
manometer was used to measure the air flow
rate, and the Air box was also installed to reduce the
air flow fluctuations into the engine. Since the
experiment was conducted at a constant speed of
1500 rev/min, it was necessary to calculate the
amount of LPG injected and Gasoline supplied into
the engine. This amount was calculated with
weighing machine and glass burette respectively.
Provision was also made for the measurement of
exhaust gas temperature, engine body temperature,
water inlet and outlet temperature, thermocouples are
to be used. A non contact type digital tachometer is
use for the measurement of speed of the engine. Load
bank is provided to give load to engine. The test rig
enables the study of engine performance involving
brake power, thermal efficiency, volumetric
efficiency, fuel consumption, and air-fuel ratio.
Table 2. Test Engine Specifications
Items
Make
Bore
Stroke
No. Of Cylinder
Engine type
Specifications
Kirloskar
87.5 mm
110 mm
1
4-stroke Spark ignition Engine
Displacement
cooling
starting
maximum Power
661cc
water cooling
Auto starting
2kW @ 1500 rpm
The experimental Set-up is as shown in
figure1..Basically. The engine used in the study is
a single cylinder, water cooled with a dog dish
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4. Brake specific energy consumption (BSEC)
= BSFC x C.V……….. (kJ/kW hr)
5. Actual air volume (Va)
= Cd x Ax sqrt(2x g x ∆Hw x (ρwater/ρair)) x 60
Theoretical volume of air = π
6.
xn
× d2×Lx K
4
7. Brake thermal Efficiency =
BP x 100
Mf x Calorific Value
8. Volumetric Efficiency ηv =
Vax100
Vs
5.
RESULT AND DISCUSSUION
a.
Performance characteristics
The brake thermal Efficiency of the engine is
gradually increasing with respective to increasing
the Power. However, the Brake Thermal efficiency
increases when the compression ratio increases.
When using Gasoline fuel the Efficiency values
slightly higher than the using LPG fuel. It is seen than
for compression ratio 9:1, 10:1 constant speed of
1500rpm the maximum values of efficiencies for
Gasoline are higher than that of LPG.
brake thermal efficiency(ηbth)%
16
14
12
10
8
Gasoline 9:1
6
LPG 9:1
4
Gasoline 10:1
2
LPG 10:1
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Load(kW)
From the graph ,volumetric efficiency increases with
load by increasing the compression ratio. Gasoline
having higher volumetric efficiency than LPG as it is
in gaseous state.
Volumetric Efficiency(ηv)%
3. TEST PROCEDURE
The experimentation work will be held on 4-stroke
single cylinder Spark ignition engine. The
experimental procedure will be carried as given
below1.
Before start the engine check all the
connections made properly or not.
2.
“ON” the LPG cylinder regulator. Before
start the engine ensure any leakages in the set up.
LPG supply to the engine is controlled by a
regulator or vaporizer. This converts the LPG into a
vapour. Put the LPG cylinder on weighing machine
for its consumption measurement
3.
The vapour is fed into a mixer located near
the intake manifold. Where it is mixed with filtered
air before being drawn into the combustion
chamber
4.
Make open the fuel supply valve while
during the operation of both fuel (LPG and Gasoline).
5.
While using gasoline as a fuel check that the
throttling is at WOT position of carburetor so as the
speed of the engine is regulated by governing
mechanism alone with no setting for throttling.
6.
Check that there should not be any air
bubbles in the fuel (gasoline) supply line.
7.
Initially start the engine and run it till reach
to steady state approximately for 15-20 min.
8.
Take the reading maintaining speed of the
engine constant 1500RPM and varying load from 0 to
2 kW in step of 200Wand vice versa at varying speed
condition.
9.
During the experimentation while varying
the load on engine, the speed was maintained
constant and the fluctuation in the speed should be in
a tolerable limit.
10.
Note down the Exhaust temperature, engine
cooling water inlet and outlet temperature and engine
body temperature, manometer reading, burette and
stop watch reading.
11.
Same procedure was repeated for another
fuel.
12.
Following the First reading, compression
ratio of the engine changed from 9:1 to 10:1 manually
by putting the slits at the base engine.
13.
Repeat the same procedure again. By doing
calculation and graphical representation results are to
be discussed.
4. DATA REDUCTION
L= Stroke length;
D= Bore Diameter;
K= Number of cylinders;
n= Revolutions per minute
Hw= Manometer Reading
1.
Compression ratio
= swept volume +clearance volume
Clearance volume
2. Swept volume = π/4 x D2 x L… (m3)
45
40
35
30
25
20
15
10
5
0
Gasoline 9:1
LPG 9:1
Gasoline 10:1
LPG 10:1
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Load in KW
3.
Brake specific fuel consumption
=Mf/BP……….( Kg/kW hr)
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250
900
Gasoline 9:1
LPG 9:1
Gasoline 10:1
LPG 10:1
200
150
100
50
800
HC Emissions (ppm)
Brake Specific Energy consumption
MJ/Kwhr)
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700
600
500
400
9:1 gasoline
300
9:1 LPG
200
10:1 Gasoline
100
10:1 LPG
0
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
2
Load kW
Load in KW
CO emissions- CO is produced when there is not
enough air in the combustion chamber. When the
fuel does not burn completely; the carbon in the fuel
will convert into CO. As it is seen in the compression
ratio increases, CO emissions also increase with
increasing load on engine. The maximum value of
CO2 emissions for LPG is considerable lower than for
the gasoline.
4
3.5
CO Emissions in % vol
Above figure indicate that the brake specific
energy consumption decreases as the load on the
engine increases. As it can be clearly seen from
this
figure,
LPG increases the specific fuel
consumption of the engine in comparison with
Gasoline. This graph shows BSEC of Gasoline and
LPG values are gradually decreasing with respective
increasing the Brake Power. Using Gasoline fuel
the BSEC consumption values slightly lower than
the using LPG fuel. Because of less Calorific value
of Gasoline.
b.
Exhaust Emissions Characteristics
CO2 emissions- From the Graph it is found that
as the compression ratio increases, Brake Power
and CO2 emission increase. When compared with
LPG
3
2.5
2
9:1 gasoline
1.5
9:1 LPG
1
10:1 Gasoline
10:1 LPG
0.5
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
,
Load kW
3
2.5
2
1.5
Gasoline 9:1
1
LPG 9:1
Gasoline 10:1
0.5
LPG 10:1
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Load kW
CO2 emission increases with incomplete combustion
of fuel and it is higher for gasoline when compared
with LPG.
HC Emissions- It is seen from the graph, it is found
that as the compression ratio increases, speed and
HC emission increase. Maximum HC emission for
LPG is less than that for Gasoline. HC emission
increases with incomplete combustion of fuel and
therefore it is higher for Gasoline when compared
with LPG.
NOx Emissions-From the graph is seen that values of
NOx emissions are more than that of gasoline and
increases with increase in load, compression ratio.
This is due to the increase in in-cylinder combustion
temperature. The formation of NOx is enhanced
in an environment of high temperature and high
oxygen concentration .Also the laminar burning
velocity of LPG is more than that of the gasoline is
about 0.46 m/s which reduces the combustion and
subsequently
the in-cylinder peak temperature
increases.
800
NOx Emission in PPM
CO2 Emissions in % vol
3.5
700
600
500
400
300
9:1 Gasoline
200
9:1 LPG
10:1 Gasoline
100
10:1 LPG
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Load kW
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Volumetric Efficiency ηv %
35
30
25
20
9:1 Gasoline
9:1 LPG
10:1 Gasoline
10:1 LPG
15
10
5
0
1400
1500
1600
1700
1800
Speed in RPM
CO emissions
emissions increases due to increasing
consumption at higher engine speed.
fuel
9:1 Gasoline
9:1 LPG
10:1 Gasoline
10:1 LPG
3.5
3
2.5
2
1.5
1
0.5
0
1400
1500
1600
1700
1800
CO2 emissions in % volume
Speed in rpm
9:1 Gasoline
9:1 LPG
10:1 Gasoline
10:1 LPG
3.5
3
2.5
2
1.5
1
0.5
0
1400
1500
1600
1700
Speed in rpm
1800
9:1 Gasoline
9:1 LPG
10:1 Gasoline
10:1 LPG
600
HC Emissions in ppm
c.
For Varying Speed Condition While
Maintaining The Constant load of 1kW.
From the graph ,it is found that Brake thermal
Efficiency is goes on decreasing as speed of the
engine increased. But the volumetric efficiency is
continuously goes on increasing with speed with
compression ratio. But LPG having less value of
efficiencies than that of Gasoline.
The graph shows the relationship of CO, CO2
emissions between LPG and Gasoline at varying
speed condition with increasing compression ratio.
The concentration of CO,CO2 emissions increases
with speed and their values are lower for LPG than
that of gasoline at same speed value. The CO2
500
400
300
200
100
0
1400
1500
1600
1700
1800
Speed (rpm)
Graph shows,HC exhaust decreases with increasing
the speed. At 1800 rpm. HC concentration form using
LPG is obviously higher than gasoline as CO2
emissions are lower for it because unburned LPG is
converted to the HC emissions , as volumetric
efficiency of LPG is less than gasoline, less air for
combustion is available .But NOx emissions are
more for LPG compared with gasoline.
6.
CONCLUSIONS
As compression ratio increases, brake thermal
efficiency increases, LPG have a higher octane rating
and hence the engine can run effectively at relatively
high compression ratios without knock. The CO
and HC emissions increase as the compression
ratio, speed, and load increase. In the case of
using LPG in SI engines, the burning rate of fuel
is increased, and thus, the combustion duration is
decreased. Therefore, the cylinder pressures and
temperatures predicted for LPG are higher compared
to gasoline. Combustion of gaseous fuels like LPG
occurs in a nearly uniform fuel air mixture
leading to a reduction in incomplete combustion.
When using Gasoline fuel the BSEC consumption
values slightly lower than the using LPG fuel.
Because the
calorific value of
Gasoline is
(43MJ/Kg)
less compared to the LPG
(46.1MJ/Kg).When load increase on the engine the
CO,HC and CO2 emissions
also increase.
However, these emissions higher for Gasoline when
compared with LPG.
7.
FUTURE SCOPE
The above set up is presently studied under the using
Liquefied Petroleum Gas (LPG) at variable
compression ratios on the single cylinder four
stroke spark-ignition engine, but the same set up
can be studied for compare Gasoline and LPG–
Gasoline blends for different percentage of LPG in
Gasoline at Higher compression ratios of the engine
say about 11:1,12:1. Nevertheless, LPG systems that
inject LPG into the inlet port in liquid state rather
than as a gas to improve the volumetric efficiency.
There is also scope for direct injection of liquid LPG
into the cylinder, in the manner of GDI engines, and
this would improve the performance of LPG fuelled
SI engine.
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8.
REFERENCES
U.S. Department of Energy “journal of
Energy Efficiency and Renewable Energy”August
2003.
2.
Fuel properties,”IANGV Emission Report “
31.03.2000
3.
Advancements in Automobile Technology,
Sunday, October 24, 2010.
4.
O.Badr,N.Alsayed and M. Manaf, college of
engineering united Arab in Emirates university,” A
parametric study on the lean misfiring and knocking
limits of gas fuelled spark ignition engines”, Applied
thermal Engineering Vol.18,No 7,pp 579-594,1998.
5.
Shinichi Goto*
Daeyup Lee,
Naoya
Harayama, Fumitaka Honjo, Hidekazu Honma,
Yoshitaka Wakao, Makihiko Mori,” Development of
LPG SI and CI Engines for Heavy Duty
Vehicles”Seoul 2000FISITA World Automotive
Congress
2000 A171 June 12-15, 2000, Seoul,
Korea
6.
Ki Hyung Lee, Chang Sik Lee, Jea Duk
Ryu And Gyung-Min Choi “analysis of combustion
and flame propagation characteristics of LPG and
gasoline fuels by laser deflection method”, KSME
International Journal Vol.16 No.7 , 2002, page(s): 873-1028
7.
G.H.Choi,J.H.Kim
Christian
Homeyer
University of Applied Science at Berlin, Berlin,
Germany” Effects of Different LPG Fuel Systems on
Performances of Variable Compression Ratio Single
Cylinder Engine” Paper no. ICEF2002-519 pp. 369375
8.
Jeaduk Ryu,
Ki
hyung Lee
“An
experimental study of the flame propagation and
combustion characteristics of LPG
fuel” Fuel
Volume 84, Issue 9, June 2005, Pages 1116-1127.
9.
M.A.Ceviz ,F.Yuksel, Department of
Mechanical Engineering, University of Ataturk,
Erzurum 25240, Turkey Rec.15 January 2005; acc.12
September 2005 “Cyclic variations on LPG and
gasoline fuelled lean burn SI Engine”, Renewable
Energy 31 (2006) 1950 – 1960.
10.
Orhan Durgun,Hakan Bayraktar, “Investigati
ng the effects of LPG on spark ignition engine
combustion and performance” Energy Conversion
and Management Volume 46, Issues 13-14, August
2005, Pages 2317-2333
11.
Seokhwan Lee, , Seungmook Oh, and Young
Choi” Performance and emission characteristics of an
SI engine operated with DME blended LPG
fuel”Fuel,Volume88, Pages 1009-1015.
12.
R. K. Mandloi, A.Rehman” Mechanical
Engineering Department Maulana Azad National
Institute of Technology, Bhopal.-462051,
India long term continuous use of Auto-LPG causes
thermal Pitting in automotive S. I. Engine Parts”
International Journal of Engineering Science and
Technology Vol. 2(10), 2010, 5907-5911
13.
N. Seshaiah, Professor of Mechanical Engg.,
M.I.T.S, Madanapalle, Angallu-517325, A.P, India
“Efficiency and exhaust gas analysis of variable
1.
compression ratio spark ignition engine fuelled with
alternative fuels” International Journal of Energy and
Environment Volume 1, Issue 5, 2010 pp.861-870
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