1. INTERNATIONALMechanical Engineering and Technology (IJMET), ISSN 0976 –
International Journal of JOURNAL OF MECHANICAL ENGINEERING
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME
AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 4, Issue 1, January- February (2013), pp. 233-241 IJMET
© IAEME: www.iaeme.com/ijmet.asp
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EFFECT OF INJECTOR OPENING PRESSURE ON PERFORMANCE,
COMBUSTION AND EMISSION CHARACTERISTICS OF C.I. ENGINE
FUELLED WITH PALM OIL METHYL ESTER
Sanjay Patil
Automobile Engineering, Guru Nanak Dev Engineering College, Bidar, India,
ABSTRACT
This paper presents the development of computer simulation framework for prediction
of performance, combustion and emission characteristics of compression ignition engine
fuelled with palm oil methyl ester at different injector opening pressures. In present work, a
simulation model is developed using double wiebe’s function to predict the performance of
compression ignition engine. During analysis, the effect of change in injector opening
pressure from 200 bar to 220 and 240 bar on engine performance, combustion and emission
parameters is predicted. The engine performance is improved at injector opening pressure of
220 bar as compared to rated injector opening pressure of 200 bar. Variation of injector
opening pressure to 240 resulted in inferior engine performance, combustion and emission
characteristics. Highest brake thermal efficiency is observed when fuel injected at 220 bar
injector opening pressure. The simulation results where brake thermal efficiency is highest
are compared with that of experimental results and it is observed that simulated results are in
closer approximation with experimental results.
Key words: Simulation, straight vegetable oil, biodiesel, compression ignition engine, palm
oil methyl ester.
1. INTRODUCTION
The limited resources of fossil fuels, increasing prices of crude oil and environmental
concerns have been prompted for the search of an alternative fuel to diesel oil. Among
possible alternate fuels biodiesel has very high potential as it can be derived from plant
species. The engine performance depends on fuel properties like viscosity, cetane number
etc; engine parameters like combustion chamber geometry, compression ratio; injection
parameters like fuel injection timing (FIT), injector opening pressure (IOP), rate of fuel
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2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME
injection, number of nozzle holes, diameter of nozzle holes, etc. Variation in IOP changes the
fuel spray pattern, droplet size and droplet penetration causes the rate of evaporation, mixing
of fuel air, etc, resulting variation in engine performance, combustion and emission
characteristics. Venkanna B.K.et.al [1] conducted experimental investigations on constant
speed diesel engine. Engine is fuelled with blend of honne oil and diesel at different IOP.
Increase in IOP from 200 bar to 240 bar, resulted improvement in brake thermal efficiency
(BTE) and NOx emissions and decrease in CO, HC, SO emissions. Further increase in IOP to
260 bar resulted in inferior engine performance due to disturbance in fuel injection pattern. S.
Satish kumar et.al [2] observed significant improvement in engine performance with blend of
40% karanj oil and 60% diesel at injection pressure of 170 bar as compared to injection
pressure of 200 bar. Puhan Sukuamr et.al [3] have conducted performance test on diesel
engine fuelled with linseed methyl ester (LOME) and found that engine performance with
LOME was inferior compared to diesel due to its lower calorific value. They also conducted
investigations at different injection pressure 200 bar and 240 bar. At injector opening
pressure of 240 bar, BTE was higher and carbon monoxide emission was lower as compared
to preset IOP of 200 bar. GVNSR Ratnakara Rao et. al [4] used a four stroke single cylinder
diesel engine fuelled with diesel to investigate optimum injection pressure and timing. The
highest BTE was obtained at 200 bar IOP and 11° btdc. However there was slight increase in
frictional power at this condition. The experimental investigation for estimation of engine
performance is costly and timing consuming process. Hence a simulation model can be
developed to use as a tool to predict the engine performance at lower cost. Also the model
can be used to study the effect of change in engine operating parameters on engine
performance, combustion and emission characteristics. A.S. Ramadhas et.al [5] developed
theoretical zero-dimensional model having single wiebe function with assumed adjustable
parameters to predict the results. Rubber seed oil is considered for investigation.
A computer simulation model based on First law of thermodynamics can be
developed using double wiebe function to take account of heat released during premixed and
diffusive phase of combustion separately and to predict the engine performance, combustion
and emission characteristics at different injector opening pressures. This paper presents
theoretical investigation on effect of variation of IOP on performance, combustion and
emission characteristics of diesel engine fuelled with palm oil methyl ester (POME). During
analysis, IOP is changed from 200 bar to 240 bar in a step of 20 bar.
2. MATHEMATICAL MODELING
2.1. Energy balance equation
According to the first law of thermodynamics for the closed system the energy
balance equation is
du dQr dw (1)
m = −
dθ dθ dθ
du dQr dw
where dθ is rate of change of internal energy,dθ
is rate of heat released and dθ
is rate
of work done.
Upon simplification by considering ideal gas law and rate of heat transfer we get
equation (1) as
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3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME
dT 1 dQr hc A(T − Tw ) RT dV (2)
= − −
dθ mcv dθ mcv cvV dθ
Where hc A(T − Tw ) the convective heat transfer between gases and cylinder wall and hc is
heat transfer coefficient computed by Hohenberg equation [6]. Range-kutta fourth order
algorithm is used to solve the above equation (2) for temperature and pressure at every crank
angle.
2.2 Cylinder volume at any crank angle
The slider crank angle formula is used to find the cylinder volume at any crank angle
[7].
 r 1 − cos θ 1  L 
2 
V (θ ) = Vdisp  − +  2  − sin θ 
2 (3)
 r −1

2 2  S 

where r = compression ratio, L = length of connecting rod and S= stroke length.
2.3 Combustion Process
dQr Qp θ 
m p −1
 θ  
mp
= 6.908 mp   exp − 6.908  +
dθ θd θ   θ  
 p   p  (4)
Qd θ 
md −1  θ 
md

6.908 md 
θ 
 exp − 6.908  
θp  θ  
 d    p  
The heat release rate is computed with equation (4). The parameters θ p & θd represent
the duration, mp & m d are shape factors and Qp and Qd represent the integrated energy release
for premixed and diffusion combustion phases respectively. Adjustable parameters are
obtained with established correlation model such that the simulated heat release profile
matches closely with experimental data. The amount of heat released in premixed phase is
50% of heat release due to the amount of fuel injected during ignition delay period is
assumed.
2.4 Ignition delay
An empirical formula, developed by Hardenberg and Hase [8] is used for predicting
Ignition delay in crank angle degrees.
  1 1  21.2  
0.63
(5)
ID = (0.36 + 0.22Cm )expEA  −   
  RT 17190 P −12.4  
 
where I ID = ignition delay period and EA is apparent activation energy.
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4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME
2. 5 Gas properties calculation
The gaseous mixture properties like internal energy, enthalpy, specific heats at
constant pressure and constant volume are obtained based on the chemical composition of the
reactant mixture, pressure and temperature [7].
2.6 Friction losses
Total friction loss calculated by the equation given below [9].
C m ∗ 1000 2 (6)
FP = C + 1.44 + 0.4(C m )
B
where FP is total friction power loss and C is a constant, which depends on the engine type,
C=75kPa for direct injection engine.
2. 7 NOx formation
NOx formation has been predicted using procedure explained by Turns [10]. The
following equation is used for computation of nitric oxide.
0 .5
d [NO ]  k p Po  (7)
= 2k1 f   [N 2 ][O2 ]0.5
dt  RT 
 u 
 −39370  − ∆G oT 
   
T (k )   RT 
where k1 f = 1.82 ∗ 1014 e  and o
k pP = e  u 
[N 2 ] and [O2 ] are equilibrium nitrogen and oxygen concentrations in moles.
[N 2 ] = 0.21∗ P
RuT
[O2 ] = 0.79 ∗ P
RuT
2.8 Soot formation prediction
The following equation has been used for prediction of soot [11].
 − Esf 
 
dmsoot  RT 
(8)
= C BS ∗ φ ∗ m f ∗ P 0.5 ∗ e  u 
dt
where CBS is constant and Esf is the activation energy of the soot formation reaction.
3. SIMULATION
A thermodynamic model has been developed using First law of thermodynamics. The
molecular formula of diesel fuel is taken as C10H22 and for POME is approximated as
C19H34O2. Suitable correlations are established between adjustable parameters of double
wiebe’s function, relative air-fuel ratio and IOP engine operating conditions, so that the
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5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME
simulated in cylinder pressure matches closely with experimental results. A computer
program has been developed using MATLAB for numerical solution of the equations used in
the thermodynamic model (as described above). This model computes cylinder pressure,
combustion temperature, brake thermal efficiency, brake specific fuel consumption, exhaust
gas temperature and emissions like nitric oxide and soot density for neat POME (P100).
4. EXPERIMENTAL SETUP AND PROCEDURE
Experimental results with TV-1, stationary, single cylinder, water cooled, variable
compression ratio diesel engine developing 3.5 kW at 1500 rpm are used for model
validation. The engine is coupled to a water cooled eddy current dynamometer for loading.
Thermocouples are used for measurement of coolant and exhaust gas temperature. An air box
with water manometer is used to measure air flow rate and a burette is used to measure fuel
flow. The cylinder pressure data is recorded by using piezoelectric transducer. The technical
specifications of the engine and the fuel properties are given in “Table 1” and “Table 2”
respectively. The IOP is varied by changing the nozzle spring tension.
Table 1. Engine specifications Table 1. Fuel properties
Sl. Parameter Specification Properties Diesel POME
No (D0) (P100)
1 Type Four stroke direct injection Viscosity in cst 4.25 4.7
single cylinder VCR diesel (at 30°C)
engine Flash point(°C) 79 170
2 Software used Engine soft Fire point(°C) 85 200
3 IOP 200 bar Carbon residue (%) 0.1 0.62
4 Rated power 3.5 kW @1500 rpm Calorific 42000 36000
5 Cylinder diameter 87.5 mm value(kj/kg)
6 Stroke 110 mm Specific gravity 0.830 0.870
7 Compression ratio 17.5:1 (at 25°C)
8 Injection timing 23 degree before TDC
5. RESULTS AND DISCUSSION
5.1 Effect of injector opening pressure on
5.1.1 Performance Parameters
"Fig." 1, 2 and 3 shows variation of brake thermal efficiency, specific fuel
consumption and exhaust gas temperature with load at different injector opening pressures.
Improvement in brake thermal efficiency (BTE) and reduction in brake specific fuel
consumption (BSFC) and exhaust gas temperature (EGT) is observed with increase in IOP to
220 bar. Further increase in IOP to 240 bar resulted in reduction in BTE, increase in BSFC
and EGT as compared to preset IOP of 200 bar. This improvement in engine performance at
220 bar is due to improvement in combustion phenomenon because of reduction in fuel
droplet size, better mixing of fuel and air, etc. increase in IOP from 220 bar to 240 bar
resulted in deterioration of engine performance due to improper combustion.
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6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME
30
Brake Thermal Efficiency
0.46
Consumption (kg/kW-hr)
25 0.44
Brake Specific Fuel
0.42
20
0.4
(%)
15 P100 at 200 bar 0.38
P100 at 220 bar
10 P100 at 240 bar 0.36 P100 at 200 bar
0.34 P100 at 220 bar
5 P100 at 240 bar
0.32
0.3
0
0 25 50 75 100
0 25 50 75 100
Load (%) Load (%)
Figure 1. Variation of brake thermal efficiency Figure 2. Variation of brake specific fuel
at different injector opening pressure. consumption at different injector opening
pressure.
430
Exhaust Gas Temperature
380
P100 at 200 bar
330 P100 at 220 bar
(°C)
P100 at 240 bar
280
230
180
0 25 50 75 100
Load (%)
Figure 3. Variation of exhaust gas temperature
at different injector opening pressure.
5.1.2 Combustion Parameters
P100 at 200 bar 0.06
Net Heat Release Rate
70
P100 at 220 bar
0.05 P100 at 200
P100 at 240 bar
Peak Pressure (bar)
65
P100 at 220
(kJ/CA)
60 0.04
55 P100 at 240
50 0.03
45
40 0.02
35
30 0.01
25
20 0
0 25 50 75 100 165 185 205 225
Load (%) Crank Angle (CA)
Figure 4. Variation of peak pressure at Figure 5. Variation of heat release rate at
different injector opening pressure. different injector opening pressure.
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7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME
"Fig." 4 and 5 shows variation of peak pressure and net rate of heat release with change in injector
opening pressure. Increase in IOP from 200 bar to 220 resulted in higher peak pressure and increase in
net heat rate release (NHRR) during premixed phase of combustion. This may be due to better
atomization, quick evaporation of fuel and better mixing, etc. However, increase in IOP from 220 bar
to 240 bar resulted in lower peak pressure and less rate of heat release during premixed phase due to
unpredictable injection pattern. Further, increase in IOP from 220 bar to 240 bar resulted in lower
NHRR due to poor combustion. At very high injection pressures, injection of very small droplets
having lesser momentum might have experienced partial suffocation by its own products of
combustion due to loss of its relative velocity with air.
5.1.3 Emission Parameters
Oxides of Nitrogen (ppm)
1600
5.00E-07
P100 at 200 bar
1400 P100 at 200 bar 4.50E-07
P100 at 220 bar
Soot (gm/m^3)
P100 at 220 bar 4.00E-07
1200 P100 at 240 bar 3.50E-07 P100 at 240 bar
3.00E-07
1000 2.50E-07
2.00E-07
800
1.50E-07
600 1.00E-07
5.00E-08
400 0.00E+00
0 25 50 75 100 0 25 50 75 100
Load (%) Load (%)
Figure 6. Variation of oxides of nitrogen at Figure 7. Variation of soot density at different
different injector opening pressure. injector opening pressure.
"Fig." 6 and 7 shows variation of nitric oxide and soot density at different injector opening pressures.
It is found that increase in IOP resulted in increase in nitric oxide emissions. The soot density is
observed to be reduced from IOP of 200 bar to 220 bar and increased from IOP of 220 bar to 240 bar.
6. MODEL VALIDATION
30 70
Brake Thermal Efficiency (%)
65
Peak Pressure (bar)
25
60
20 55
50 P100 at 220_exp
15
P100 at 220_exp 45
P100 at 220_simu
10 P100 at 220_simu 40
35
5
30
0 25
0 25 50 75 100 0 25 50 75 100
Load (%) Load (%)
Figure 8. Compression of simulated and Figure 9. Compression of simulated and
experimental result of BTE. experimental result of peak pressure.
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8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME
Model is validated for brake thermal efficiency and peak pressure at IOP of 220 bar by
comparing with experimental results. From figures 8 & 9 it is observed that the simulated
results are closer to experimental results.
7. CONCLUSION
From the results of computer simulation model and experimental following conclusion are
drawn
• Improvement in BTE is observed at IOP of 220 bar as compared to IOP of 200 bar.
• Lower EGT at IOP of 220 bar and higher EGT at IOP of 240 bar is observed as
compared to IOP of 200 bar.
• Increase in IOP from 220 bar to 240 bar resulted in reduction in peak pressure and
maximum rate of heat release.
• Increase in nitric oxide emissions is observed with increase in IOP.
• Soot density is observed to be reduced from IOP of 200 bar to 220 bar.
• The simulation results are found to be in closer approximation with experimental
results.
8. ACKNOWLEDGEMENT
I would like to express my gratitude to my Guide Dr. M. M. Akarte, National Institute
of Industrial Engineering Mumbai- India for his valuable advice and guidance throughout this
work.
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