1. Special Issue: ICCEMME-2021
International J of Engine Research
1–12
Ó IMechE 2022
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DOI: 10.1177/14680874221132963
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Comparative study on the effect of
nanoparticles in ternary fuel blends
on combustion, performance, and
emissions characteristics of diesel
engine
Michael G Bidir1
, Millerjothi Narayanan Kalamegam1
, Muyiwa S
Adaramola2
, Ftwi Y Hagos3
and Ramesh Chandra Singh4
Abstract
Literature indicated that pure biodiesel is not suitable as a stand-alone fuel for compression ignition engines due to tech-
nical and operational conditions. Biodiesel is being utilized as a blended fuel with diesel. The main drawbacks of biodiesel
blends are the formation of higher NOx emissions and brake-specific energy consumption due to the lower calorific
value of the fuel. Hence, there are efforts to improve the fuel by the incorporation of nanoparticles. The objective of the
current manuscript is toexperimentally investigate the effect of adding 50 mg per liter (mg/L) graphene nanoparticles and
5% and 15% ethanol mixed to form ternary blended fuel on the combustion, performance and emissions in diesel engine.
In the present work, a single-cylinder, four-stroke, water-cooled naturally aspirated DI diesel engine capable of develop-
ing 3.5 kW at 1500 rpm was used for the study. The fuel samples are K20, K15E5, K5E15, K15E5GNP50, and
K5E15GNP50, where ‘‘K,’’ ‘‘E,’’ and ‘‘GNP’’ stand for biodiesel, ethanol, and graphene nanoparticle, respectively and the
corresponding number indicate percentage in the overall blend. The result showed that nanoparticles added to ternary
fuel blends improve the engine performance meaningfully, and the brake thermal efficiency higher by 2.03% compared to
K20 biodiesel blend. K15E5GNP50 blends resulted in an appreciable reduction in CO, UHC, NOx and smoke levels
compared to that of other blends. The maximum reduction in NOx and CO level was found to be about 21% compared
to neat diesel. Also, the maximum reduction in smoke level was detected to be about 50%, mainly at full-load conditions.
It is concluded that graphene nanoparticle-enhanced blends of K15E5GNP50 has improved engine performance and
emissions characteristics.
Keywords
Graphene nanoparticle, ternary blends, combustion, performance, emissions
Date received: 9 December 2021; accepted: 22 September 2022
Introduction
The growing concern toward pollution from the com-
bustion of petroleum-derived fuels has attracted many
researchers to investigate the prospect of utilizing sus-
tainable energy sources as a supplementary fuel to die-
sel.1–3
Reduction of engine exhaust discharges is a
crucial study area in engine research with the growing
worry on ecological safety and to meet emissions stan-
dards set limits by legislators and policymakers. With
the use of fossil fuels for transportation sector increas-
ing at an alarming rate, increasing the share of biofuels
as blends with diesel will have huge impact in the reduc-
tion of pollutant emissions.
1
School of Mechanical and Industrial Engineering, EiT-M, Mekelle
University, Mekelle, Ethiopia
2
Department of Environmental Science and Natural Resource
Management, Norwegian University of Life Sciences, Norway
3
Department of Mechanical and Industrial Engineering, College of
Engineering, Sultan Qaboos University, Muscat, Oman
4
Department of Mechanical Engineering, Delhi Technological University,
Delhi, India
Corresponding authors:
Michael G Bidir, School of Mechanical and Industrial Engineering, EiT-M,
Mekelle University, P.O. Box 231, Mekelle, Ethiopia.
Email: michael.gebreyesus@mu.edu.et
Ftwi Y Hagos, Department of Mechanical and Industrial Engineering,
College of Engineering, Sultan Qaboos University, P.O. Box 50, Al-khoud
Sultanate of Oman, Muscat P.C. 123, Oman.
Email: f.hagos@squ.edu.om
2. Biodiesel is utilized in diesel engines either as a
stand-alone fuel or blended with other renewable or
conventional fuels without or with minor engine modi-
fications. Nonetheless, ethanol can not be utilized as
the sole fuel in diesel engines, and it ought to be mixed
with neat diesel or biodiesel fuel in the presence of an
emulsifier. The addition of ethanol has mutually
encouraging and adverse consequences on the engine
hardware. From one perspective, it can advance the
cold flow properties, like cloud point and pour point.
The addition of ethanol in the base fuel blends results
in reducing fuel density, kinematic viscosity, calorific
value, and flashpoint of the mixed blend.4–6
Thus, mix-
ing ethanol with biodiesel blends is favorable for better
engine performance and has several benefits like reduc-
ing exhaust discharges, reduced lubrication oil utiliza-
tion, and practically equivalent efficiency compared to
diesel-powered engines.7
However, the mixing of etha-
nol has some drawbacks such as stability problems,
inferior physicochemical properties, and the need for
additives to stay stable.8,9
Some of the efforts to mini-
mize these drawbacks being researched currently are
addition of nanoparticles, use of chemical surfactants,
use of biodiesel as surfactant and different emulsifica-
tion techniques.
Many types of research have been investigated to
explore the effects of enhancing biodiesel/diesel blends
with mixes of ethanol and methanol by adding nano-
particles (NPs). It is the most effective method of
upgrading the engine’s performance qualities. The
addition of NPs in blended fuel results in bunches of
accumulation at the fuel’s lower part because of their
relative volume and mass; thus, scattering the NPs par-
ticles consistently throughout the blend is a massive
job. Such deposit, accumulation, and grouping issues
can be solved by utilizing NPs with magnitude ranging
from 1 to 100nm, which is effectively dispersible in the
fuel mix.10,11
According to the review work by the same
authors, the NPs most commonly used as nano-
additives for enhancement of physico-chemical proper-
ties and performance of blended fuels are metallic oxi-
des and their combinations.12
The exhaust discharge and performance qualities of
a diesel engine driven with methanol-diesel and metallic
NPs additives were analyzed by Khorramshokouh
et al.13
It was observed that the CO discharge was
expanded while the ash release and BSFC (brake spe-
cific fuel consumption) were moderated. Bash14
has
studied the effect of mixing CNT (carbon nanotubes)
to biodiesel combined blend on the engine’s exhaust
discharge and performance features. It was noticed that
the brake thermal efficiency (BTE) was enhanced by
3.6%, whereas the ash and NOx discharges were les-
sened by 49% and 33%, respectively.
The impact of incorporating CNT with diesel-
biodiesel-ethanol mixes on diesel engine’s exhaust dis-
charge and performance attributes was experimentally
investigated by Heydari-Maleney et al.15
It was
reported that the BTE, power, and torque increased by
about 16%, 16%, and 14%, respectively. The BSFC
and engine gas temperature were lessened by about
12% and 2%, respectively. Besides, UHC, CO, and
ash’s engine exhaust releases were essentially decreased
by about 32%, 6%, and 7%, respectively. The incor-
poration of nanographene oxide to diesel-biodiesel
mixes and the effect on the engine’s exhaust discharge
and performance attributes were examined by Hoseini
et al.16
The report revealed that the rate of pressure rise
(RPR), highest pressure, and highest heat release were
improved by about 5%, 6%, and 5%, respectively. The
brake power was improved by 16%, while the BSFC
was reduced by 15%. The UHC and CO emissions were
reduced by 28% and 18%, respectively. In contrast, the
NOx emission has increased by 8%. Similarly, the
effects of adding Al2O3 (Alumina) NPs to diesel-biodie-
sel-ethanol mixes on the test engine’s exhaust dis-
charges and performance were examined by Venu and
Madhavan.17
The results showed that the highest pres-
sure, ignition delay (ID), and the degree of heat
removal were all reduced. In addition to that, there was
an appreciable reduction in NOx, UHC, CO emissions.
From the literature survey made, it was observed
that a considerable amount of work had been done on
the use of blends added to NPs; nonetheless, the inves-
tigation on diesel engine operation the addition of
nanoparticles into the ternary mix on combustion, per-
formance, and exhaust emission attributes have not
been assessed broadly. Even though GNP is getting
more attention in the fuels research due to its unique
nature of having two dimensional with sp2-carbons
and carbon being a combustible material that can
enhance the blended fuel calorific value, there are lim-
ited research in the literature. Therefore, the objective
of the current manuscript is to experimentally investi-
gate of the effect of adding 50 mg per liter (mg/L) gra-
phene nanoparticles and 5% and 15% ethanol mixed
to form ternary blended fuel on the combustion, per-
formance and emissions in diesel engine.
Materials and methods
Base fuels
The main ingredients for the preparation of test fuel
samples to be utilized for the investigation on CI test
engines are fossil-based diesel, karanja biodiesel, etha-
nol, and GNP. Fossil-based diesel is maintained at 80%
for all the fuels samples; biofuels cover the remaining
20% share of the blend. Two different samples are pre-
pared by considering 5% and 15% biodiesel. Ethanol
was supplemented in 5% and 15% by volume by reduc-
ing the share of biodiesel by an equivalent amount in
the K20 blend, and the mixtures are symbolized by
K15E5 and K5E15, respectively. The thermophysical
properties of the base fuels, namely fossil-based diesel,
keranja biodiesel, and ethanol, are provided in Table 1.
2 International J of Engine Research 00(0)
3. Assessment of graphene nanoparticle (GNP)
Table 2 shows the specification of the GNP used in the
current study. An ultra-pure extremely high surface
area graphene with high thermal conductivity and
mechanical strength produced through modified
hummer’s technique done with a registered process
with several points of quality checks. The GNP was
evaluated via FT-IR spectroscopy, as represented in
Figure 1. FTIR integrity of hexagonal building on
clean graphene was established in the presence of peaks
at 1540–1697 cm21
illuminating the presence of carbon
double bonding (C=C), which may take part in setting
up a different remarkable line association among GNP
and Biodiesel-diesel-ethanol blends.
The XRD analysis of synthesized GNPs shown in
Figure 2 was used to examine the completely clear
setup of the GNP pieces. The outcomes exposed that it
has a working band for extra oxygen-holding (–OH, –
COOH) created throughout the oxidation of graphite.
In addition, the crystal measurement (t) was evaluated
by Scherrer method, where the GNP crystal measure-
ment was demonstrated to be 0.34 nm. The two tests
confirm that GNP incorporation to the ternary mixes
can deliver more dynamic species for the duration of
the burning process, like –OH, –COOH functional
groups, which speeds up the ignition interaction and
buzz oxidation of residue. Similarly, the thermogravi-
metric analysis (TGA) of GNP has indicated that
nearly 60%(w/w) of the specimen is decayed at about
’ 200°C. This sensible low disintegration temperature
of GNP additionally increases atomized fuel drop’s
degree of dissipation, causing reduced start ignition
delay (ID) and boosting the combustion process. The
considerable thermal decay in GNP ascribes to the
release of extra oxygen functional groups for efficient
combustion of the fuel.18–21
The GNP was arranged through synthetic oxidation
manufactured by the improved Hummers’ approach at
Addnano Technologies. Transmission electron micro-
scopy (TEM) of the GNP as shown in Figure 3 acclaims
mean particle sizes of 100. It can be noticed that the
GNP involves single-or complex graphene sheets. It is
acknowledged from the TEM assessment that it can be
understood that the presence of the GNPs is shallow,
and it additionally exhibits the evolution of the lattice
segment.
Preparation of nanoparticle incorporated ternary
fuels
There are different types of blending and incorporation
of nanoparticles in fuels namely stirring, splashing,
Table 1. Property of the base fuels.
Properties Diesel KBD Ethanol Test method
Calorific value, MJ/kg 43.6 39.132 27.53 ASTM D240
Cetane index 50 52.8 8 ASTM D976
Flash point, °C 58 181 — ASTM D93
Density at 15°C, gm/mL 830 889 780.15 ASTM D1298
Sulfur content, % by mass 48 — — ASTM D129
K. Viscosity at 40°C, cSt 2.51 5.71 1.072 ASTM D445
Table 2. GPN specifications.
Parameters Specifications
Purity . 99%
Average thickness (z) 0.8–1.6 nm
Average lateral dimension (X &Y) 1 mm
Number of layers 1–3
Surface area 200–700 m2
/g
Bulk density 0.0006 g/cc
Chemical formula C
Physical form Fluffy, very light powder
Color Black powder
Figure 1. FTIR analysis of synthesized GNPs.
Figure 2. XRD analysis of synthesized GNPs.
Bidir et al. 3
4. inline blending and ultrasonication. Ultrasonication is
the most common method used for the preparation of
nanoparticle incorporated fuels.22
The incorporation of
GNP prepares two more fuel samples. A mass of 50 g/L
of GNP was incorporated, and K15E5GPN50 and
K5E15GPN50 denote the blends. The ternary fuel was
processed using a magnetic stirrer and a Hielscher-
made ultrasonicator (UP400St) emulsifiers shown in
Figure 4(a) and (b). The magnetic stirrer first uniformly
blends the GNP before it is subjected to ultrasonica-
tion. The setting used for the ultrasonic emulsifier is
10% cycle, 60% amplitude, and emulsification time for
5 min.23
The blend temperature was steadily controlled
not to surpass 40°C with an infrared thermometer, and
an ice bath was used to maintain the temperature
within the needed range. Table 3 shows the physico-
chemical properties of the blends. Every fuel sample
was tested for each of the properties several times, and
then the mean value was taken. It can be seen that the
addition of karanja biodiesel (K20, K15E5, and
K5E15) on diesel has slightly reduced the calorific value
and increased the kinematic viscosities of the blend. At
the same time, the addition of ethanol on the blend has
further decreased the calorific value and changed the
course of the kinematic viscosity. The addition of GNP
has started improving the calorific value and the kine-
matic viscosity marginally. Flashpoint of the karanja
biodiesel was much higher than diesel fuel, which is
positive in terms of transportation and handling.
Flashpoints of other blends were very low; therefore,
modified blends showed relatively lower flash points
than K20.
Experimental setup
The engine used in the current investigation is a
variable compression ratio (VCR) Kirloskar made, a
Figure 3. SEM analysis of synthesized GNPs: (a) 40,000x magnification and (b)10,000x maginification.
Figure 4. Stirring (a) and ultrasonication (b) processes during
the sample preparation.
Table 3. Properties of the ternary and nanoparticle incorporated ternary fuel samples.
Parameters D100 K20 K15E5 K5E15 K15E5GPN50 K5E15GPN50 Test method
Calorific value, MJ/kg 43.60 41.20 41.05 40.70 41.10 40.90 ASTM D240
Cetane index 50.0 51.3 49.0 45.0 50.1 48.5 ASTM D976
Flash point, °C 58 65 47 9 15 11 ASTM D93
Density at 15°C, g/ml 830 831 830 827 831 829 ASTM D1298
Sulfur content, % by mass 48 0.01 0.01 0.054 0.017 0.026 ASTM D129
K. Viscosity at 40°C, cSt 2.51 3.03 3.01 2.28 2.88 2.46 ASTM D445
4 International J of Engine Research 00(0)
5. naturally-aspirated single-cylinder diesel engine. The
photographic view and accompanying schematic dia-
gram of the entire experimental setup are shown in
Figure 5(a) and (b).
The engine was attached with an eddy current type
dynamometer to change load and control engine speed
through the engine control unit module, as shown in
Figure 5(a). The compression ratio of the VCR engine
was fixed at 18:1. The test engine was furnished with
fundamental devices for in-cylinder pressure (piezo sen-
sor ranging 5000psi with low noise cable) and crank
angle encoding (TDC pulse resolution of 1 rpm). The
pressure transducer generates an electric charge pro-
portional to the pressure, and the charge is amplified to
generate output as a voltage proportional to the charge
produced. The phasing of the in-cylinder pressure to
the crank angle is done with the help of the crank angle
encoder that establishes the top dead center of the
cylinder Indicators were connected to data acquisition
and computing systems (combustion analyzer) for the
pressure-volume (P-V) and pressure-crank angle degree
(P-u) logging.
Three readings were taken for each fuel blend sam-
ple, and the average values were noted, and the study’s
standard deviation and uncertainty analysis were deter-
mined. The engine is coupled to a five-gas analyzer and
smoke meter (Figure 5(a)). Labview software is used as
an interface between the computer and the engine sen-
sors (air and fuel flow, temperatures, and load measure-
ment sensors). The experimental process is divided into
two phases. In the first phase, the base fuels with no
nanoparticle added (pure diesel, K20, K15E5, and
K5E15) are used to run the engine, whereas, in the sec-
ond phase, nano-additive fuels are used (K15E5GPN50
and K5E15GPN50). Emission and performance data
for non-nano-additive fuels are recorded under the
steady-state condition of the engine. Initially, the engine
was permitted to run with neat diesel as base fuel and
then fueled with all types of biodiesel blends without
and with GNPs. The engine was operated between no-
load to and 100% load (0–12 kg) with a difference of
3 kg at constant speed 1500rpm. Table 4 shows the
technical specification of the engine used in the current
investigation.
Result and discussions
The based diesel fuel (D100), diesel-biodiesel blended
fuel (K20), blended diesel-biodiesel-ethanol fuels
(K15E15 and K5E15), and the nano-enhanced blended
diesel-biodiesel-ethanol fuels (K15E5GPN50 and
Figure 5. Experimental engine setup (a) and its schematic layout (b).
Table 4. Technical specifications of the diesel engine.24
Description Specifications
Model CRDI VCR Engine Test 244
Engine type Make Kirloskar, single-cylinder, 4-stroke,
water-cooled, naturally aspirated, VCR
diesel engine
Bore dia. (mm) 87.5
Cylinder volume
(cc)
661.45
Max. rated power 3.5 kW at 1500 rpm
Engine speed
(rpm)
1500
Compression
ratio
18:1
No. of injectors 1
Injection timing 23° bTDC
Valve timing Inlet valve opens (IVO): 4.5° bTDCInlet
valve closes (IVC): 144.5° bTDCExhaust
valve opens (EVO): 144.5° aTDCExhaust
valve closes (EVC): 4.5° aTDC
Fuel injection
pressure (bar)
270
Injector angle 15° with vertical
Dynamometer
type and arm
length (mm)
Eddy-current water-cooled, 185
Bidir et al. 5
6. K5E15GNP50) were all investigated for the combus-
tion, performance, and emissions on an instrumented
single-cylinder compression ignition engine with its spe-
cification discussed in the methodology section (Section
2.3). The combustion parameters evaluated are the in-
cylinder pressure, mean gas temperature (MGT), and
mass fraction burnt (MFB) are plotted against crank
angle position. Whereas the engine performance para-
meters considered in the current study are the BTE,
BSFC and EGT plotted against the brake power (BP).
The CO, UHC, NOx, and smoke opacity emissions
were compared among the fuels tested under the corre-
sponding load conditions. The findings are presented in
sections 3.1, 3.2, and 3.3.
Combustion characteristics in-cylinder pressure
The in-cylinder pressures versus the crank angle degree
of the five test fuels at full load condition are presented
in Figure 6, The graph is plotted for only 80°CA in the
vicinity of the TDC (from 320 to 400°CA) to show the
variation of the in-cylinder pressure of varied fuels. It
can be seen that the biodiesel blends with the addition
of 50 mg/L of graphene nanoparticles (K15E5GNP50
and K5E15GNP50) have shown marginally higher in-
cylinder pressure contrasted with the rest of the blended
test fuels. This is because of the associated impact of
GNP and fuel particles present in the fuel. The highest
in-cylinder pressure was recorded at 44.90 bar for
K15E5GNP50 and 44.52 bar for K5E15GNP50.
Moreover, incorporating GNP with K15E5 and
K5E15 fuel blends has sped up the ignition interaction,
prompting higher chamber pressure. This is because as
graphene nanoparticles possess a higher surface-to-
volume proportion, it enhances the process of high
thermal conductivity, leading to an increase in the max-
imum cylinder pressure.25,26
It was additionally
observed that the burning starts earlier for diesel-bio-
diesel-ethanol mixes than conventional diesel for the
fuel injection timing of 23° bTDC. Numerous investi-
gational studies have shown that the higher oxygen
content and improved cetane index of diesel-biodiesel-
ethanol blends prompt fuel atomization and vaporiza-
tion, which lessens the ignition period, resulting in
lower cylinder pressure.27,28
Mean gas temperature. The mean temperatures of burnt
and unburned gases of the mixture in the combustion
chamber of the engine cylinder during the combustion
cycle is named mean gas temperature (MGT). The
MGT provides information on the degree of response
throughout the burning of the fuel, and it is a necessary
parameter where its value is correlated to the adiabatic
flame temperature. The profile of MGT with respect to
crank angle for all test fuels with varying engine loads
is revealed in Figure 7. Similar to the pressure profile,
the graph is plotted for only 70°CA in the vicinity of
the TDC (from 350 to 420°CA) to show the variation.
It can be seen from the graph that MGT for D100,
K20, K15E5, K5E15, K15E5GNP50, and K5E15
GNP50 test fuels are 865.21°C, 799.80°C, 776.20°C,
766.32°C, 841.37°C, and 839.65°C, respectively at
about 15° CA aTDC. The highest MGT was reported
with the base fuel (Diesel), whereas it was observed that
K15E5GNP50 and K5E15GNP50 exhibited the highest
MGT compared to their blended test fuel counterparts.
This is because K15E5GNP50 and K5E15GNP50
mixes have a higher level of oxygen. Higher oxygen
content prompts a higher heat release rate, causing the
hotter environment created inside the combustion
chamber, increasing the maximum cycle temperature.29
The highest in-cylinder pressure is reached, although
the burning cycle is not complete. The ignition stays
dynamic in certain parts of the burning chamber for
more revolution of the crankshaft (crank angle
degree).29
Mass fraction burn (MFB). Mass fraction burn justifies
how fast the mixture responds to the process of com-
bustion. At the same time, the amount of mass fraction
burned gives detailed information about how much
quantity of the mixture burned in terms of percentage
Figure 7. Mean gas temperature versus crank angle degree
over 350°–420° CA duration.
Figure 6. In-cylinder pressure versus crank angle degree
(CAD) for different test fuels.
6 International J of Engine Research 00(0)
7. with respect to crank angle.30
With the help of mass
fraction data analysis, one can determine the combus-
tion time, including the start of combustion (SOC) and
end of combustion (EOC). The SOC in the combustion
process signifies the mass fraction burned as zero on
the curve and then increases exponentially, which indi-
cates the combustion process and end of combustion.31
Figure 8 shows the variation of mass fraction burned
with a crank angle for biodiesel blends with and with-
out graphene nanoparticles as additives for a total of
32° crankshafts rotational angles. The addition of GNP
50 in the blends of K15E5GNP50 and K5E15GNP50
biodiesel has reduced the total time of combustion as
compared with other blends of biodiesel. The total
combustion time for graphene added biodiesel blends
was 29°CA of average crankshaft rotation angle com-
pared with other biodiesel blends and 31°CA of the
average crankshaft rotation angle. 10% mass fraction
mixture of test fuel containing graphene 50 added
blends of biodiesel was burned after 4°CA (average)
crankshaft rotation angle after the SOC for GNP50
added biodiesel. Similarly, the 50% and 90% mass frac-
tion burnt were achieved after the SOC at 18°CA and
27°CA, respectively. The difference of mass fraction
burnt of the test fuel samples with and without GNP is
shown in Figure 8. The results explain that GNP into
the mixed fuel speedup the SOC and lessened the igni-
tion period. This can be attributed to the effect of the
GNP advance in the vaporization rate and rapid air-
fuel mixture formation improvement prompt a reduc-
tion in ID.
Performance characteristics
Brake specific fuel consumption (BSFC). The BSFC is mea-
sured as one of the crucial parameters for engine per-
formance studies as it does not comprise the calorific
value for its determination. The BSFC with respect to
the brake power plot is displayed in Figure 9. The
BSFC of all the fuels has decreased with the engine load
increased along the load spectrum. The BSFC for K20,
K15E5, K5E15, K15E5GNP50, and K5E15GNP50 are
recorded higher than neat diesel by about 7.32%,
10.56%, 10.99%, 6.12%, and 6.51%, respectively. It
was noticed that the BSFC of the test engine fueled
with diesel-biodiesel-ethanol mixes was higher than that
neat diesel at all test loads because of their lower heat-
ing value. It has been contingent that the GNP added
fuel tests improved the BSFC contrasted with the
blends without GNP. Despite the lower calorific value
of the GNP added fuels than pure diesel, the NPs are
predominant in energy utilization. The NPs supply
extra oxygen content, which improves the heat transfer
among the burnt and unburned fuel particles inside the
combustion chamber. Besides, it minimizes the impact
of the lower calorific value of the blends and has shown
relatively improved BSFC contrasted with the blends
without GNP.3
However, the BSFC was barely lower
for K15E5GNP50 and K5E15GNP50 contrasted with
K15E5 and K5E15 at full test loads.
Brake thermal efficiency. BTE assesses the productivity of
the test engine on how it changes the fuel’s chemical
energy into valuable work. It is measured by dividing
the engine’s brake power by the energy content supplied
to the engine. Figure 10 depicts the BTEs of the gra-
phene nanoparticles blends of Karanja biodiesel at dif-
ferent brake power. The analysis showed that the BTE
rises with an increase in test loads for all test fuels. It
can be seen that the BTE of the D100, K20, K15E5,
K5E15, K15E5GNP5, and K5E15GNP50 were found
to be about 31.58%, 30.97%, 30.11%, 29.96%,
31.61%, and 31.36%, respectively. BTE of the mix
K5E15GNP50 is higher than all blended test fuels at
full-load operating conditions. This increase in BTE is
because of the improvement in burning temperature
and in-cylinder pressure. In the case of K5E15, the BTE
is reduced by about 5.12% compared to GNP50 added
blends. This might be due to the higher ethanol mix
ratio resulting in lower calorific value and increased fuel
consumption of diesel-biodiesel-ethanol mixed fuels.3
Figure 8. Disparity of mass fraction burnt with respect to
crank angle.
Figure 9. variation of brake specific fuel consumption with
respect to brake power.
Bidir et al. 7
8. Exhaust gas temperature (EGT). The variation of exhaust
gas temperature against different brake power condi-
tions for various biodiesel blends is compared with die-
sel in Figure 11. It can be observed that the exhaust gas
temperature for D100, K20, K15E5, K5E15,
K15E5GPN50, and K5E15GPN50 are noted as
377.72°C, 370.85°C, 367.38°C, 366.36°C, 376.98°C, and
371.57°C, respectively at full-load. For the most part, it
tends to be seen from the figure that the incorporation
of GPN into ethanol-biodiesel-diesel blends increases
the EGT. As mentioned earlier, the incorporation of
GNP enhanced the combustion rate in the combustion
chamber. Besides, the main reason for the improved
fuel consumption of the GNP added fuels is the higher
cetane index and better surface area to volume propor-
tion. These elements give better response time among
the fuel and oxygen, subsequently increasing the burn-
ing rate and decreasing the fuel consumption, as
demonstrated in Figure 11.18
A further benefit of the
combination of GNP to the ternary fuel blends is that
it can reduce the rich fuel zone in the diffusion process
and increase the EGT.32
In addition, the improved
records of EGT are accomplished at GNP dosage of
50 mg/L, mainly for above 75% engine test loads.
These conclusions are in similar correspondence with
those of Soudagar et al.25
and Nanthagopal et al.33
Emission characteristics CO emissions
The carbon monoxide (CO) is one of the significant
pollutants present in the diesel engine’s tailpipe. The
CO outflow rises because of the fuel’s inadequate com-
bustion, which might be because of engine load, speed,
fuel injection pressure, fuel injection timing, fuel atomi-
zation, and combustion chamber design. Figure 12 dis-
plays the graphic outline of the CO discharge of all test
fuels. At part-loads, the CO release with GNP applica-
tion is observed to be lower than those without GNP.
This is because, at part loads operations, the lower tem-
perature of the engine does not help for complete com-
bustion. But when the load increases, the combustion
improves, reducing CO discharge toward full load
operation, particularly GNP50 added blended biodiesel
fuel. About 13.79% and 20.69% reduction in CO emis-
sion are recorded for the case of K15E5GPN50 and
K5E15GPN50, respectively than neat diesel operation
at full-load conditions. The reduction in CO emission is
because adding the graphene nanoparticles in the
blends biodiesel blends improves the calorific value that
advances complete combustion and enhanced oxidation
of CO into CO2.
Unburned hydrocarbon (UHC). The UHC is formed
because of the deficiency in the ignition of the supplied
fuel to the combustion chamber. The variation of UHC
releases against load is shown in Figure 13. It shows
the decrease in UHC discharges when GNP is added to
the diesel-biodiesel-ethanol fuel mixes. For the K20 fuel
blend, it was seen that the discharges of UHCs were
more significant at higher load conditions showing an
increase of 6.45% compared to D100. At lower load
situations, the UHC discharges from the tested fuels
were fairly at their lower range. This is because of the
lower fuel admission and lean fuel mixture, weak burn-
ing, atomization, and higher viscosity.34
Nevertheless,
the UHCs discharge was decently lower toward the
average (50%) load. The UHCs discharge for
K15E5GNP50 and K5E15GPN50 was reduced by
25.93% and 32.00%, respectively compared to D100 at
full load conditions.
Figure 10. Disparity of brake thermal efficiency with respect
to brake power.
Figure 11. Disparity of exhaust gas temperature with respect
to brake power.
Figure 12. Disparity of carbon monoxide emission with
respect to engine load.
8 International J of Engine Research 00(0)
9. NOx emissions. Usually, the NOx release rises with a rise
in engine load. It can be justified because of how NOx
development is affected strikingly by the speed of fire
and lower propagation of heat with lean combinations
giving a more extended chance for NOx formation.7
In
addition, energy kinetics describes that the arrange-
ment of NOx is expanded essentially with expanding
fire temperature. Accordingly, NOx is expanded with
engine load increment. The disparity in NOx discharge
with engine load appears in Figure 14. The K5E15 dis-
played the least from all test fuels considered almost at
all test load conditions except at full load. At full load
operating conditions, the NOx emission has reduced by
6.50%, 8.05%, 6.50%, 1.24%, and 4.64% for K20,
K15E5, K5E15, K15E5GNP50, and K5E15GNP50
was, respectively as compared to D100. The conse-
quences of diesel-biodiesel-ethanol mixes display that
the NOx outflow is lesser than conventional diesel for
all test loads. This can be justified by adding ethanol to
karanja biodiesel lessens the cetane number of the test
fuel, whereas it builds the amount of oxygen, with a
base modification in burning heat content. The impact
of expanding oxygen content prompts a more stoichio-
metric air-fuel proportion, and the influences of cetane
number decrease and expanding heat content of eva-
poration which delivers a chilling effect.35,36
NOx for-
mation is principally subject to the duration of ignition,
the content of oxygen, and the temperature of the
flame.
Consequently, lessening the ignition length or fire
temperature brings about decreased NOx. It tends to
be seen that the NOx delivered from ethanol and GNPs
added fuels are amazingly lower at all loads. The blend
with a higher ethanol proportion in the mix shows a
better reduction in NOx concentration.
Smoke opacity. Smoke opacity has been one of the basic
boundaries for the exhaust discharge inspection of die-
sel engines as it indicates the soluble organic part of the
particulate matter (PM) in the discharge. These particu-
lates are small nano-size matters consisting of sedi-
ments and UHC, which might be harmful whenever
breathed-in. Thus, it can be related to fuel’s tendency
to produce PM while burning. Figure 15 explains the
smoke opacity of the test fuel samples versus the engine
loads. K5E15GPN50 provided about 50.58% lessened
smoke opacity than the D100. It might be credited to
the earlier beginning of the burning of K5E15GPN50
because of its improved cetane number. Thus, the burn-
ing began earlier, permitting a further opportunity to
oxid sediments.37
Sediment development happens at the
early premixed burning stage when the air-fuel propor-
tion is stoichiometry. Hence, the higher oxygen extent
in K5E15GPN50 gave extra oxidation in the fuel-rich
regions and decreased the smoke opacity, particularly
at higher loads. K5E15, K15E5GPN50, and K15E5
additionally trailed the pattern of K5E15GPN50, and
they provided about 49.42%, 44.81%, and 44.67%
lower smoke opacity correspondingly as they are more
oxygenated than neat diesel. Also, K20 decreased
smoke opacity by about 24.21% compared to D100.
Hence, such oxygenated mixes reduced the possibility
of fuel-rich zones arrangement and helped lessen smoke
opacity.
Figure 14. Disparity of nitric oxide emission with respect to
engine load.
Figure 13. Disparity of unburned hydrocarbon emission with
respect to engine load.
Figure 15. Disparity of smoke opacity with respect to engine
load.
Bidir et al. 9
10. Conclusion
Experimental investigation into the effects of the add-
ing of GNP on combustion, performance, and emission
characteristics of ternary blends in the CIDE was con-
ducted with different fuel blends and concentration
ratios and at varying loads with 1500 rpm, a constant
speed. The appropriate inferences are drawn based on
the experimental results.
As per the test results, ethanol addition decreases the
density and kinematic viscosity of the ternary mixtures.
Besides, it reduces the heat content of the blends. The
decrease in the kinematic viscosity of the fuel as a result
of the addition of ethanol advances the spray outline of
the fuel and upgrades the nature of burning.
The 50 mg/L GNP incorporation to K15E5 and
K5E15 blends has enhanced in-cylinder pressure and
the combustion temperature. Hence, it accelerates the
process of combustion resulting in an improved rate of
pressure rise. Maximum in-cylinder pressure of
44.90 bar for K15E5GNP50 and 44.52 bar for
K5E15GNP50 was attained. While the blended fuel has
recorded an increase in EGT as compared to pure die-
sel, an addition of GNP has reversed the trend. On the
engine performance side, a reduction of 10.99% on the
BSFC and an improvement of about 5.22% on the
BTE were reported with the addition of GNP in the
blend.
The exhaust emission releases of CO, UHC NOx,
and smoke opacity were lessened significantly by about
20.69%, 25.93%, 4.64%, and 50.58%, respectively, at
full-load operating conditions compared to D100 when
GNP is added to the diesel-biodiesel-ethanol fuel
blends.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
article.
Funding
The author(s) disclosed receipt of the following financial sup-
port for the research, authorship, and/or publication of this
article: The author would like to recognize the MU-HU-
NMBU phase IV NoRAD project for the financial support
through a Ph.D. scholarship grant (EiT-M/Ph.D./007/09),
RTF-DCS fellowship grant (DCS/2019/000287), and DTU
for the technical support during the work presented in this
study.
ORCID iD
Ftwi Y Hagos https://orcid.org/0000-0002-8774-8577
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Appendix
Notation
ASTM American Society for Testing and
Materials
aTDC After topdead center
BP Brake power
BSFC Brake specific fuel consumption
bTDC Before top dead center
BTE Brake thermal efficiency
CA Crank Angle
CI Compression ignition
CNT Carbon nano tube
CO Carbon monoxide
EGT Exhaust gas temperature
EOC End of combustion
EVC Exhaust valve closes
EVO Exhaust valve opens
GNP graphene nanoparticle
ID Ignition delay
IVC Inlet valve closes
IVO Inlet valve opens
MFB Mass fraction burnt
Bidir et al. 11
12. MGT Mean gas temperature
NP Nanoparticle
NOx Nitrogen oxides
PM Particulate matter
rpm revolution per minute
RPR Rate of pressure rise
SEM Scanning electron microscope
SOC Start of combustion
TDC Top dead center
TEM Transmission electron microscopy
TGA Thermogravimetric analysis
XRD X-Ray diffraction
UHC Unburned hydrocarbon
VCR Variable compression ratio
12 International J of Engine Research 00(0)
