International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
Engine performance and emissions of a diesel engine
operating on jojoba methyl ester with exhaust gas
recirculation at 1600 rpm
H. E. SALEH, Waled Saleh Muhammad
Mechanical Power Department, Faculty of Engineering,
Omer El-Mokhtar University, Libya, P.O. Box 919
~55% with increase of bsfc less than 5%. While the
optimal level of EGR rate should be used is less
than 12% at full load as engine economy worsens
as more than 11% increase in bsfc and the
reduction in NO x was 33%.
Keywords: Diesel engine, Jojoba methyl ester,
Nitrogenous oxides, Exhaust gas recirculation
1. Introduction
Concerns about energy conservation and
environmental protection are placing increasingly
rigorous demands on internal combustion engines
for improved fuel efficiency and used renewable
fuels. There is also a need to reduce carbon dioxide
( CO 2 ) emissions to prevent global warming.
Diesel engine had found wider and wider
application as it has good fuel economy and lower
emissions of carbon dioxides. However, the
harmful effects on human health and environment
brought by its pollutant emissions are causing great
concern. As a result, various methods for reducing
the tailpipe emissions from diesel engine vehicles
challenges posed by increasingly stringent
legislations from the Environmental Protection
Agency (EPA) [1].
jojoba ranks high as the vast area of the Egyptian
deserts can be used for production the seeds are
used to produce the jojoba fuel [9-12].
Several problems, however, have impaired the
widespread use of biodiesel. They are related to the
economics and properties of biodiesel. Some
researchers reported that the most detrimental
parameter in the use of vegetable oil as fuel is its
higher viscosity [13-14]. The high viscosity will
lead to blockage of fuel lines, filters, high nozzle
valve opening pressures and poor atomization. The
problems of high fuel viscosity can be overcome by
using esters, blending and heating. The methyl
esters of vegetable oils, which are produced by
combining methanol with the vegetable oil [15],
these fuels tend to burn cleaner, perform
comparably to conventional diesel fuel, and
combust similarly to diesel fuel. It is generally
recognized that biodiesel has lower emissions, with
ISSN: 2231-5381
Abstract
The aim of this study mainly was to quantify the
efficiency of exhaust gas recirculation (EGR) when
using Jojoba Methyl Ester (JME) fuel in a fully
instrumented, two-cylinder, naturally aspirated,
four-stroke direct injection diesel engine. The tests
were made in two sections. Firstly, the measured
performance and exhaust emissions of the diesel
engine operating with diesel fuel and JME are
determined and compared. Secondly, tests were
performed at 1600 rpm and loads to investigate the
EGR effect on engine performance and exhaust
emissions including nitrogenous oxides (NOx),
carbon monoxide (CO), unburned hydrocarbons
(HC) and exhaust gas temperatures. Also, effect of
cooled EGR with high ratio at full load on engine
performance and emissions was examined. The
results showed that EGR is an effective technique
for reducing NO x emissions with JME fuel
especially in light duty diesel engines. With the
application of EGR method, the CO and HC
concentration in the engine-out emissions
increased. Large EGR rate (25%~40%) can be used
at 25%load for high NO x reduction was 50%
are being researched. Technologies like exhaust gas
recirculation (EGR), soot traps and exhaust gas
aftertreatment are essential to cater to the
The interest to renewable energy sources for energy
production is not new. Several studies have been
conducted to qualify various oil and their blends
from plants and vegetables as alternative renewable
energy sources. This renewable source of fuel may
also help in reducing the net production of CO 2
from combustion sources and our dependence on
fossil fuels. Often the vegetable oils investigated
for their suitability as biodiesel are those which
occur abundantly in the country of testing.
Therefore, soybean oil is of primary interest as
biodiesel source in the United States while many
European countries are concerned with rapeseed
oil, and countries with tropical climate prefer to
utilize coconut oil, hazelnut or palm oil [2-4]. Other
vegetable oils, including sunflower, rubber, etc.,
have also been investigated. Furthermore, other
sources of biodiesel studied include animal fats,
salmon oil and or waste cooking oils [5-8]. In the
search for a viable vegetable oil as fuel for Egypt,
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International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
in 2 hours. In addition, these studies concentrated
on measuring the ignition delay period of JME and
JME-gas oil blends at different conditions in shock
tube. It was found that JME liquid and its blend
with light diesel fuel exhibit shorter ignition delay
than light diesel fuel.
An experimental investigation has been carried out
to examine for the first time the performance and
combustion noise of an indirect injection diesel
engine running with new fuel derived from pure
jojoba oil, JME, and its blends with gas oil [10]. A
Ricardo E6 compression swirl diesel engine was
fully instrumented for the measurement of
combustion pressure and its rise rate and other
operating parameters. Test parameters included the
percentage of JME in the blend, engine speed, load,
injection timing and engine compression ratio.
Results showed that the new fuel derived from
jojoba is generally comparable and good
replacement to gas oil in diesel engine at most
engine operating conditions, in terms of
performance parameters and combustion noise
produced. Also, with the same test rig, JME was
investigated as a pilot fuel as a way to improve the
performance of dual fuel engine running on natural
gas or liquefied petroleum gas at part load [11-12].
Results showed that using the JME fuel with its
improved properties has improved the dual fuel
engine performance, reduced the combustion noise
and extended knocking limits.
An experimental evaluation of using jojoba oil as
an alternate diesel engine fuel has been conducted
by Bawady et. al [19]. Measurements of jojoba oil
chemical and physical properties have indicated a
good potential of using jojoba oil as an alternative
diesel engine fuel. Experimental measurements of
different performance parameters of a single
cylinder, naturally aspirated, direct injection diesel
engine have been performed using gas oil and
blends of gas oil with jojoba oil. Measurements of
engine performance parameters at different load
conditions over the engine speed range have
generally indicated a negligible loss of engine
power, a slight increase in brake specific fuel
consumption and a reduction in soot emission using
blends of jojoba oil with gas oil as compared to gas
oil. The reduction in engine soot emission has been
observed to increase with the increase of jojoba oil
percentage in the fuel blend.
Heat flux mapping and metal temperature
distribution was carried out using a single cylinder,
naturally aspirated, indirect injection four-stroke
diesel engine, Since heat fluxes and metal
temperatures in the combustion chamber
component parts play a paramount role in engine
reliability and life time [16]. Results at variable
loads and speeds were taken with JME and were
compared with those obtained with gas oil. It was
found that the heat flux level and gas face metal
the exception of nitrogen oxides ( NO x ), than
conventional petroleum fuel.
Many studies have been working on Jojoba as a
promising vegetable oil fuel for diesel engines for
many years [9-12]. During this time, many tests
have been performed on neat jojoba and Jojoba
Methyl Ester (JME). These studies showed that this
fuel is a very good gas oil substitute and offered the
same product guarantees for JME as for gas oil due
to the fact that the physiochemical properties of
JME are close to those of gas oil. An increase in the
emissions of nitrogenous oxides ( NO x ) at all
operating conditions have been observed by [16].
The objective of this work was to quantify the
efficiency of exhaust gas recirculation (EGR) when
using JME as a renewable fuel. In this paper, all
experiments described here were performed on a
direct injection diesel engine in first to compare
diesel fuel and JME fuel in terms of engine
performance and exhaust emissions at various
speeds under full load and the second to investigate
the effect of various EGR rates with JME fuel for
NO x reduction. Also, effect of cooled EGR with
high ratio at full load on engine performance and
emissions was examined. EGR effects on engine
performance, engine emissions, exhaust gas
temperature, combustion quality and fuel economy
for both high and low load engine operating
conditions at 1600 rpm were investigated.
2. Jojoba seed oil extraction and biodiesel
production
The jojoba shrub was grown in Africa and also
grown in the Sonora Desert at the south of the
USA. El-Moogy [17] has collected a considerable
amount of data about jojoba and its cultivation for
investment in Egypt and he termed the oil as "green
gold". The term "green gold" stems from the fact
that the seeds are used to produce oil while the
residue can be used as fodder or solid fuel implying
that there is no waste. Each acre which
accommodates 900-1000 shrubs can produce about
540-600 kg of seeds when the plant is four years
old; but the production increases gradually till it
reaches 1350-1500 kg when the plant is ten years
old. Jojoba seeds contain 50% of its weight as oil,
so the Egyptian acre can produce 270-300 kg of oil
after four years but will increase to 675-750 kg of
oil after ten years of cultivation. The viscosity of
jojoba raw oil is high and thus warrants treatment
of oil before it becomes a viable engine fuel.
Abdel Kader [18] synthesized the jojoba oil in the
laboratory and showed that methyl ester formation
was 60% to 65% complete at respective molar
ratios of methanol/jojoba oil 4.6:1. The alkaline
catalyst used was (NaOH) and was added with a
percentage of 1% which proved to produce
0
maximum yield. At 60 C, 65% JME was produced
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International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
particulate reduction to supply nearly particle-free
exhaust gas.
temperature in the cylinder liner and head with
JME were higher than those with gas oil.
4. Experimental equipment
The experiments were carried out on a twocylinder, water cooled, four-stroke, direct injection
diesel engine. It was necessary to make some of
modifications in the engine since the original
engine had not EGR. It was necessary to connect
the exhaust manifold with the air intake manifold,
with an EGR valve at this connection. The
experimental set up is shown schematically in Fig.1
and comprises a hydraulic dynamometer, a pressure
tank, a diesel particulate bag filter, a heat
exchanger, an EGR valve, a liquid and gas fuel
metering systems, and an exhaust gases analysis
system. The engine specifications are given in
Table 1. It was necessary to connect the exhaust
manifold with the air intake manifold, with a
pressure tank, bag filter, a heat exchanger and an
EGR valve at this connection. The bag filter is used
for particulate reduction and supply of clean gas for
EGR. The pressure tank is used for reduction of
exhaust pressure pulse and the heat exchanger is
used as an exhaust cooler for cooling exhaust gas
by water flow. An EGR valve was installed in this
connection that enabled manual to control the flow
rate of EGR to the intake manifold to attain various
EGR ratios. The EGR mass rate is the ratio
between recirculated exhaust mass flow and the
total mass flow allowed to pass into the engine.
3. Mechanism of NO x formation and EGR
technique
Oxides of nitrogen are formed during combustion
when localized temperatures in the combustion
chamber exceed the critical temperature that
molecules of oxygen and nitrogen combine.
Oxygen interacts at the boundary surface between
the air and fuel. This boundary surface is where
combustion takes place. Due to burning of the fuel
droplets, the localized temperature in the vicinity of
the fuel droplets exceeds the limit at which
NO x are formed. In general, high amounts of
oxygen and high temperatures will result in high
levels of NO x formation and these conditions are
always present in the combustion chamber of diesel
engines. Since diesel engines always run at a lean
air-fuel mixture and at high compression ratios
[20].
EGR rate (%)
(
m.EGR
) 100
m.Air m.Fuel
The flow rate of air into the engine was measured
using a laminar flow element. The laminar flow
element was a honeycomb-like structure, which
provides for a certain pressure drop across itself for
a certain volumetric flow rate of air. This pressure
drop was measured using an inclined manometer.
The flow rate of EGR into the engine was
measured with a sharp edge orifice mounted on a
pipe connected to the pressure tank. An inclined
manometer was used to measure the pressure drop
across the orifice. The fuel consumption is
measured by a fuel meter. The air temperature,
exhaust gas temperature were measured using type
K thermocouples and the CO, HC and NO x levels
were obtained with a testo 350 gas analyzer was
used to measure engine exhaust pollutant
emissions. Pressure gauges were fitted to measure
the pressure of EGR, inlet mixer and fresh intake
air. A full set of readings was taken for each data
point recorded thus the EGR rate can be calculated
based
on
the
above
data.
ISSN: 2231-5381
Recently, exhaust gas recirculation, has received
attention as a potential solution. Research work
results showed that EGR is one of the most
effective methods used in modern engines for
reducing NO x emissions [21,22]. There are two
types of EGR; internal and external. Internal EGR
uses variable valve timings or other devices to
retain a certain fraction of exhaust from a preceding
cycle. External EGR uses piping to route the
exhaust gas to the intake system, where it is
inducted into the succeeding cycles and it is used in
this study. External EGR has emerged as the
preferred type of EGR for heavy-duty diesel
engines and that due to external EGR can be cooled
and that improves fuel economy and engine
performance. EGR reduces NO x because EGR
gases contain much lower concentrations of oxygen
as compared to ambient air. As a result, EGR gas
slows down the rate of combustion as there is less
oxygen in the cylinder to combust with the fuel. In
addition to having low levels of oxygen, EGR gas
also has a higher heat capacity than ambient air.
This aids in slowing down combustion because
more heat can be absorbed in an air-fuel mixture
that contains EGR gases.
While EGR is effective in reducing NOx, it also has
adverse effects on the engine efficiency and may
cause pollution of lubricating oil and corrosion of
inlet manifold and moving parts as exhaust gas
contains a lot of particulate matter. Some simple
algorithms for adjusting EGR with engine power
have been explored in the past to minimize its
impact on the engine thermal efficiency [23]. In
this paper diesel particular filter adopted for diesel
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International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
Fig. 1 Schematic of the experimental test rig
Table 1 Specification of the engine used.
MODEL
112M- Helwan
Type
4-stroke direct injection
Cooling
Water cooling
Number of cylinder
2
Diameters of cylinder (mm)
112
Stroke length (mm)
115
3
2266
Capacity ( cm )
Compression ratio
Rated speed (rpm)
Max. power at 1500 rpm (HP)
16.4
1500
26
1600 rpm. The engine evaluation at 1600 rpm-25%
load, this is a low- load condition for highway
operation. 1600 rpm-full load to represent heavy
load operation. Table 2 shows the JME fuel with its
improved properties versus diesel fuel [12]. Three
runs of tests were performed under identical
conditions to check for the repeatability of all
results and the experimental error is evaluated
according to Ref. [25]. The maximum uncertainty
in any quantity is in the range 1.5-5.5%.
5. Experimental results and discussion
The experimental results are given in two
sections. The first section compares diesel fuel and
JME fuel in terms of engine performance and
exhaust emissions at various speeds under full load.
The second section investigates the effect of
various EGR rate with JME fuel on the engine
emissions, exhaust gas temperatures and engine
fuel economy and combustion quality under
various conditions. The tests and data collection
were performed at two different engine loads at
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International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
Table 2 shows the properties of the JME fuel versus diesel fuel [12].
Properties
JME
0
0.866
Density @ 15 C
0
19.2
Kinematic viscosity @ 40 C (cSt)
1.6–7.0
Flash point
Calorific value (kj/kg)
Cetane number
Water content % by mass
Carbon residue % by mass
Ash content % by mass
Min. 55
44300
46
0.1
0.1
0.01
61
47380
63.5
0.5
0.5
0.002
JME fuel was higher combustion chamber
temperature as indicated from measured exhaust
gas temperature, as shown in Fig. 3. The NO x
concentration with JME fuel is higher than that
with diesel fuel and that is may be due to the higher
calorific value of JME. As shown in Fig. 3, at N=
1200 rpm, the increase of approximately 16% in
the NO x emissions with JME than that with diesel
fuel and about 14% at N= 1600 rpm.
The variation of carbon monoxide (CO)
emissions versus engine speed at full load is shown
in Fig. 4. The reduction in engine speed produced
higher CO in the exhaust and that due to the
increasing of the amount of fuel per stroke and
decreasing in swirl intensity within the cylinder
which causes poorer mixing since there is
insufficient oxygen to convert all carbon in the fuel
to carbon dioxide [28]. As shown in Fig 4, at low
speed, CO concentration with JME is slightly
higher than the diesel fuel and that due to the
higher viscosity of JME which causes poorer
atomization and distribution of the JME fuel air.
Also it has been shown by [29] that CO emissions
increased when the coconut oil amount increased in
the diesel fuel blends and that due to the poor spray
characteristics of coconut oil, poor mixing, and
consequently poor combustion because of coconut
oil has a viscosity of about 8 times as much as that
of diesel fuel. The author [29] has been
investigated the effect of coconut oil-diesel blends
using a single cylinder, direct-injection diesel
engine. At high speed, CO concentration with JME
is lower than that with diesel fuel that may be due
to the beneficial effect of JME as an oxygenated
fuel as mentioned before.
The variation of unburned hydrocarbons
(HC) emissions versus engine speed at full load is
shown in Fig 5. The reduction in engine speed
produced higher HC concentration due to poorer
mixing, since the fuel-air pocket can be mixed to
stoichiometric proportions and then diluted by
more air before autoignition occurs in that element
[28]. As a result there are contours for lean
equivalence ratios and when autoignition occurs
there is fuel and air mixed locally to proportions
less than the lean flammability limit. Thus this
ISSN: 2231-5381
Diesel
0.820
5.1 Comparison of performance and emissions
with JME and diesel fuel
5.1.1 Engine performance
The variation of engine speed on the brake
thermal efficiency (
th
) and the brake specific
fuel consumption (bsfc) with JME and diesel fuel at
full load is shown in Fig. 2. The experimental
results of both JME and diesel fuel indicate that the
brake thermal efficiency variations were in
harmony with the speed variations as the engine
speed increases the thermal efficiency increases for
both JME and diesel fuel. At low speeds, the
engine power and brake thermal efficiency with
JME are slightly higher than the diesel fuel. At high
speed, the engine output and efficiency with JME
were higher than that with diesel fuel. The bsfc
with JME is lower than that with diesel fuel by
8.2%, 9.8% at N = 1200 rpm and N = 1600 rpm
respectively. The main reason for the higher power
and efficiency or on the other hand, lower brake
specific fuel consumption may be explained by the
higher calorific value of JME [12,16]. Furthermore,
JME as an oxygenated fuel has a beneficial effect
on combustion, especially in fuel rich zones as
indicated by [26,27]. The author [26] found that the
power and the engine efficiency increased slightly
with indirect diesel engine running on the tobacco
methyl ester-diesel blends.
5.1.2 Engine Emissions
The
nitrogenous
oxides
( NO x ) concentration versus engine speed is
shown in Fig. 3. The results show that as the speed
decreases, NO x increases for both diesel fuel and
JME and that due to the reduction in engine speed
at full load increases the engine volumetric
efficiency, the maximum rate at which fuel is
discharged from the injector nozzle and the
quantity of fuel injected per stroke [28]. Increasing
in the amount of fuel injected leads to higher
cylinder temperatures which result in higher
NO x concentration. It would be expected that the
fuels with the highest in-cylinder temperature
levels would have the highest NO x [20]. Since
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International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
local fuel mixture does not burn and will increase
the HC concentration. Also, the percentage of heat
loss to the coolant is increasing with decreasing the
engine speed and that leads to higher HC
concentration in the exhaust gases. As shown in
Fig. 5, at low speeds, HC concentration with JME
is higher than the diesel fuel and there is no
appreciable difference between HC concentration
with JME and diesel fuel at high speed.
3000
JME fuel
Diesel fuel
2000
Full load
400
1000
1200
1400
1600
1800
2000
Engine speed (rpm)
Fig. 4 Variation of CO emissions with engine speed
240
Brake thermal efficiency (%)
1000
bscf-JME
bsfc-Diesel
th
360
32
30
320
28
Full load
280
26
24
240
22
1000
JME fuel
Diesel fuel
180
1400
1600
1800
2000
Engine speed (rpm)
Fig. 2 Relation between the th and bsfc
with the engine speed
150
800
1000
Full load
120
1200
800
90
NOx-JME
Egt-JME
NOx-Diesel
Egt-Diesel
o
210
HC (ppm)
- JME
- Gas oil
th
34
bsfc (g/kw.hr)
1500
600
NOx (ppm)
60
30
600
400
0
400
1000
1200
1400
1600
1800
2000
Engine speed (rpm)
200
Exhaust gas temperature ( C)
CO (ppm)
2500
Full load
Fig 5 Variation of HC emissions with engine speed
0
1000
1200
1400
1600
1800
200
2000
Engine speed ( N ) rpm
Fig. 3 Variation of NOx emissions with
engine speed
Also, CO and HC emissions, exhaust gas
temperatures, combustion quality and fuel economy
are obtained for wide range of various EGR rates.
5.2.1 Effect of EGR on NO x emissions and fuel
consumption with JME
Figure 6 shows influence of the various EGR
rate on NO x emissions and fuel consumption
when the diesel engine was operated with JME at
1600 rpm-25% load and 1600 rpm-100% load. It is
shown that, EGR rates produced a corresponding
decrease in NO x emissions. As stated before; this
is caused mainly by exhaust gas dilution of fresh
ISSN: 2231-5381
5.2 Experimental study on diesel engine with
JME using EGR technique
In the above section have been observed a
decrease in the emissions of CO and HC in the
almost of the operating conditions but an increase
in the NO x emissions in all operating conditions
and the overall engine performance with JME was
equivalent to that of the conventional diesel fuel.
Thus, the aim in this section is to reduce
NO x emissions using JME as fuel. The
measurements of an experimental investigation of
the effect of various EGR rates on NO x reduction
with JME at different engine parameters are
presented and discussed in the present section.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
rate larger than 12% as shown in Fig. 6 (b) and this
may result in an excessive increase in bsfc up to
11%. At that level of EGR rate, the reduction in
NO x was 33%.
900
500
N = 1600 rpm
bsfc
400
600
300
450
Jojoba Methyl Ester
200
300
100
150
0
0
0
10
20
30
40
50
EGR rate (%)
(a)
900
500
N = 1600 rpm
400
600
300
450
200
300
Jojoba Methyl Ester
bsfc (g/kw.h)
NOx (ppm)
Full load
NOx
bsfc
750
100
150
0
0
0
5
10
15
20
EGR rate (%)
(b)
Fig. 6 Variation of NO x and bsfc with EGR rate at
N= 1600 rpm
5.2.2 Effect of EGR on HC and CO emissions
with JME
It is important to measure the quantity of HC
and CO emissions in the exhaust gases when the
diesel engine was operated with JME because it is
an indicator of the completeness of the combustion.
So, the effect of EGR rate on HC emissions can be
seen on Fig. 7 at different conditions. It is shown
that the HC concentration can be maintained when
increasing EGR rate reaches 15% under different
engine conditions. Unfortunately, HC emissions
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bsfc (g/kw.h)
NOx (ppm)
25% load
NOx
750
air which causes decrease of oxygen concentration
of in-cylinder combustible mixture and decrease of
in-cylinder maximum temperature. To optimize
NO x emissions reduction, EGR rate should be
increased gradually by an EGR valve from 0% to
the maximum allowable value according to
speed/load conditions.
As shown in Fig. 6, the bsfc is decreased or
the fuel economy is raised with increasing EGR
rate up to 5% at 25% load. Very important to note
this increase in fuel economy and reduction in
NO x emissions with EGR is obtained. This is due
to increase of engine thermal efficiency because of
unburnt hydrocarbons contained in the EGR would
possibly re-burn in the mixture, leading to lower
unburnt fuel in the exhaust [30]. Furthermore,
lower combustion temperatures with EGR reduced
heat loss to the walls. At 25% load, the maximum
reduction in NO x emissions with minimum in fuel
economy is obtained by increasing EGR rate to
15~20%. It has also been shown by [21] that at low
loads, the CO 2 and H 2 O concentrations in the
exhaust gas are low, since EGR routes exhaust gas
from preceding engine combustion cycles into the
combustion chamber for succeeding combustion
cycles. Because of this, the heat capacity of the
cylinder charge decreased. So, large EGR rate
(25% ~ 40%) can be used for high reduction
efficiency of NO x (50% ~ 55%) without obvious
increase of bsfc (less than 5%). Increasing of EGR
rate above 40%, the combustion of mixture
deteriorates. Since EGR in a diesel engine displaces
a unit of fresh air with an equal unit of burned
exhaust products, it not only alters A/F ratio, but
causes a dilution effect. By reducing the oxygen
concentration, the mixing time between the directinjected fuel and the fresh oxygen increases and
reduce the burn rate once diffusion combustion
starts, therefore, makes stable combustion more
difficult [21,28] to achieve and which indicates a
speed and power output decrease and bsfc increases
up to 17%.
At high load, the heat capacity increases
as the concentrations of CO 2 and H 2 O are
substantially higher. Both these molecules have
higher than air heat capacities and with H 2 O being
much higher than CO 2 at typical combustion
temperatures [28]. With the higher heat capacity of
the mixture, more energy is required to pre-heat the
incoming mixture, thus lowering the flame
temperature and deterioration in diffusion
combustion. Furthermore, at high load, the
temperature of the mixture of EGR and fresh air
increase, the cylinder trapped mass decrease and
that has a detrimental effect on the volumetric
efficiency [21]. So, it is difficult to employ EGR
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International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
Fig. 7 Variation of CO and HC emissions with
EGR rate at N=1600 rpm
5.2.3 Effect of EGR on exhaust gas temperature
with JME
The effect of EGR rate on the exhaust gas
temperatures under the different operating
conditions is presented in Fig. 8. As expected, the
exhaust
gas
temperatures
were
reduced
continuously with increasing EGR rate. As stated
before; Increasing EGR rate augments the amount
of inert gas in the combustion chamber, lowering
the burned gas temperature and therefore lowering
the NO x emissions. Since the composition of the
EGR of diesel engine varies with load. At 25% load
and N= 1600 rpm, there is a little of CO 2 and
H 2 O concentrations in exhaust gas, so large EGR
35%~40% can be used for significant reduction in
exhaust gas temperature about 42%~48% compared
with the baseline case (without EGR) as shown in
Fig. 8. At high load the heat capacity increases as
the concentrations of CO 2 and H 2 O are
substantially higher so low EGR rate 14%~17%
can be used for the same reduction in exhaust gas
temperature.
Full load
25% load
400
5000
300
600
N = 1600 rpm
CO
HC
4000
25% load
500
N = 1600 rpm
200
100
Jojoba methyl ester
400
Jojoba Methyl Ester
3000
300
2000
HC (ppm)
CO (ppm)
Exhaust gas temperature (0C)
500
increase rapidly with greater levels of EGR rate and
this mean that the combustion quality worsens with
the increase of EGR rate. Also, it can be observed
that HC emissions at 25% load are higher than that
at full load since the lighter load reduce turbulence
and fuel mixing to too lean an equivalence ratio.
This has a negative impact on the combustion
efficiency and therefore leads to higher HC
emissions.
Also, Fig. 7 shows engine-out CO emissions
versus EGR rate for speed/load cases as before. As
previously, data points have been shown that the
trend of CO emissions is similar to HC emissions
change under the different working conditions.
Increasing EGR rate above 15%, the CO emissions
increased rapidly. The CO production is most likely
due to an incomplete combustion caused by the
diluted mixture. Trade-off between HC, CO and
NO x concentrations with increasing EGR rate
because of reduction of HC and CO needs high
temperature and complete combustion, which
requires good fuel/air mixing and enough oxygen.
Therefore, EGR can bring satisfactory results for
NO x reduction, but at the same time HC and CO
increase. From the emissions data presented above,
a better trade-off between HC, CO and
NO x emissions can be attained within a limited
EGR rate of 5% ~ 15%.
200
0
10
20
30
40
50
1000
EGR rate (%)
0
0
0
10
20
30
40
5000
600
CO
HC
4000
3000
Full load
N = 1600 rpm
ISSN: 2231-5381
500
400
Jojoba Methyl Ester
300
2000
200
1000
1. The brake power output with JME was higher
than that with diesel engine but NO x emissions
was higher with JME than those with diesel engine
at different conditions.
50
EGR rate (%)
(a)
CO (ppm)
Fig. 8 Variation of exhaust gas temperature with
EGR rate at N = 1600 rpm
6. Conclusions
In this paper, an experimental investigation
of the effect of exhaust gas recirculation on exhaust
emissions and performance in diesel engine
operating with JME. Tests were made at two loads
and 1600 rpm. Engine performance, exhaust
emissions, exhaust gas temperatures and
combustion quality were investigated. From the
study carried out the following conclusions may be
drawn:
100
HC (ppm)
0
100
0
0
0
5
10
15
20
EGR rate (%)
(b)
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Page 118
International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 3- June 2015
[9] Radwan M.S., Ismail M.A., Elfeky S.M.S.
and Abu-
Elyazeed O.S.M. “Jojoba methyl ester as a diesel fuel substitute:
Preparation and characterization” Applied Thermal Engineering,
volume 27, (2007).
[10] Selim M.Y.E., Radwan M.S., Elfeky S.M.S. “Combustion
of jojoba methyl ester in an indirect injection diesel engine”
Renewable Energy, 28, (2003).
[11]
Selim
M.Y.E.,
Radwan
M.S.,
and
Saleh
H.E.,
“Performance of Dual Fuel Engine Running on Jojoba Oil as
Pilot Fuel and CNG or LPG” ASME-JSME Thermal
Engineering, Summer Heat Transfer Conference, Canada,
(2007).
[12] Selim M.Y.E., Radwan M.S. and Saleh H.E. “Improving
the performance of dual fuel engines running on natural
gas/LPG by using pilot fuel derived from jojoba seeds”
Renewable Energy, volume 33, (2008).
[13] Ejim C.E., Fleck B.A., Amirfazli A. “Analytical study for
atomization of biodiesels and their blends in a typical injector:
surface tension and viscosity effects” Fuel, volume 86, (2007).
[14] Rakopoulos C.D., et. al. “Performance and emissions of bus
engine using blends of diesel fuel with bio-diesel of sunflower
or cottonseed oils derived from Greek feedstock” Fuel, 21 May,
(2007).
[15] Ayhan Demirbas “Biodiesel production from vegetable oils
via
catalytic
and
non-catalytic
supercritical
methanol
transesterification methods” Progress in Energy and Combustion
Science 31 (2005).
2. Increase in fuel economy with the reduction in
NO x emissions is obtained at EGR rate of 5%.
3. Large EGR rate (25%~40%) can be used at
25%load for high NO x reduction was 50% ~55%
with increase of bsfc less than 5%.
4. The optimal level of EGR rate should be used is
less than 12% at full load as engine economy
worsens as more than 11% increase in bsfc and the
reduction in NO x was 33%.
5. With the application of EGR method, the CO
and HC concentration in the engine-out emissions
increased.
6. The exhaust gas temperatures were reduced
continuously with increasing EGR rate. At 25%
load, large EGR 35%~40% can be used for
reduction in exhaust gas temperature about
42%~48% compared with the baseline case
(without EGR)
7. At high load, low EGR rate 14%~17% can be
used for reduction in exhaust gas temperature about
42%~48% compared with the baseline case
(without EGR).
8. For all operating conditions, a better trade-off
between HC, CO and NO x emissions can be
attained within a limited EGR rate of 5%~15%
with little economy penalty.
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