Materials Today: Proceedings xxx (xxxx) xxx

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Materials Today: Proceedings

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Performance and emission behaviour of diesel and blends of watermelon

seed oil biodiesel in direct injection diesel engine
M.A. Asokan, S. Senthur Prabu ⇑, Vaigandla Sai Akhil, P. Sai Bhuvan, Yedam Bhuvan Reddy
School of Mechanical Engineering, Vellore Institute of Technology (VIT), Vellore, India

a r t i c l e i n f o a b s t r a c t

Article history: Internal combustion (IC) engines increase the growth of our society and civilization. This research focuses
Received 26 October 2020 to investigate the emission, combustion and performance behaviour of single cylinder DI diesel engine
Received in revised form 5 December 2020 fuelled by diesel/watermelon seed oil biodiesel (WMB) blends. The oil from watermelon seed was con-
Accepted 10 December 2020
verted into biodiesel (methyl-ester) through Trans-esterification process. The watermelon seed biodiesel
Available online xxxx
was blended with at different proportions to diesel fuel at 20, 30 and 40%. Among the blends B20 gave
better performance, improved CO and HC emission in all aspects except NOx emission. The BSFC of
Keywords:
B20 is 0.275 kg/kWh and BTE is 32.5% at full load these are on par with diesel. Therefore, B20 of water-
Watermelon seed oil
Diesel engine
melon seed oil biodiesel as a best alternative fuel in coming years.
Biodiesel Ó 2021 Elsevier Ltd. All rights reserved.
Transesterification Selection and peer-review under responsibility of the scientific committee of the International Confer-
Emission ence on Advances in Materials Research – 2019.

1. Introduction causes nozzle clogging due to high viscosity results in poor

atomization where further ends in incomplete combustion. Not
The demand of fuel rise and depletion of petroleum products limited to the above problem high oxides of nitrogen due to
assisted to find alternate fuel for the replacement of diesel. In addi- the more presence of O2, carbon deposition on cylinder walls,
tion to that moving near to a reduced carbon economy, the devel- formation of gum due to cold flow properties. But these prob-
opment countries fixed a target to meet the 20% demand of energy lems can be eliminated by a technique called transesterification
from renewable sources in an ecological manner [1]. Especially in process. Transesterification is the most followed way for produc-
the transportation sector, the employ of diesel fuel in the public tion of biodiesel from various vegetable oils and fats. After trans-
transport vehicles like trains, trucks, buses etc. as well as in the esterification process, the biodiesel holds the qualities primarily
farm equipment’s. Alongside, the burning of diesel leads to release as same as to diesel, thus it can be mixed homogenously to
of CO2 (environmental pollution) is confined in the atmosphere any extent [3]. Though, the production cost of the biodiesel is
results in global warming (rise in earth’s temperature) [2]. In this the main limitation that practically affects large scale of biodie-
view the researcher’s taken efforts over the decades to lower the sel production. As distinguished, the biodiesel has greater value
CO2 emission from IC engines to reduce air pollution is to make of cetane number (CN) than diesel fuel. This higher CN intern
use of renewable sources especially biofuels. Biofuels are derived improves the combustion quality of biodiesel by reducing the
from biomass materials (i.e. biological organic residue) or various ignition time. Therefore, the biodiesel utilization in diesel engi-
kinds of energy-generating crop. Every biofuels are unique and nes has a major potential to resolve the problems of air pollution
containing their own characteristics. The important benefits of bio- in the atmosphere [4].
masses are renewable, non-toxic, biodegradable, reduce the emis- The emission behavior of a diesel engine is directly proportional
sion of greenhouse gas and low-level of pollution rate (CO, HC to the injected fuel scorching in the combustion chamber [5]. Wan
unburnt, smoke opacity), etc. Although there are some limitations Ghazali et al. [6] stated that the biodiesel is conceived as a renew-
of using the biofuel (biodiesel) in a diesel engine with no change able fuel. It can be derived from different non-edible and edible
oils, animal fats and waste resources (ASTM D6751 and EN14214-
standards). The utilization of non-edible sources for biodiesel like
⇑ Corresponding author. cotton seed, rubber seed, waste cooking oil, Karanja, algae etc. will
E-mail address: senthurprabu.s@vit.ac.in (S. Senthur Prabu).

https://doi.org/10.1016/j.matpr.2020.12.469
2214-7853/Ó 2021 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of the International Conference on Advances in Materials Research – 2019.

Please cite this article as: M.A. Asokan, S. Senthur Prabu, V. Sai Akhil et al., Performance and emission behaviour of diesel and blends of watermelon seed oil
biodiesel in direct injection diesel engine, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.12.469
M.A. Asokan, S. Senthur Prabu, V. Sai Akhil et al. Materials Today: Proceedings xxx (xxxx) xxx

Nomenclature

Nomenclature Percentage B30 30% Water melon seed oil biodiesel (WMB) + 70% Diesel
D100 100% Diesel B40 40% Water melon seed oil biodiesel (WMB) + 60% Diesel
B20 20% Water melon seed oil biodiesel (WMB) + 80% Diesel B100 100% water melon seed oil biodiesel

reduce the cost of source material. Whereas edible feedstock used 2. Materials and methods
for the production of biodiesel like sunflower, rice bran, coconut,
rapeseed, corn, soybean etc. as a mass production process. But it The watermelon seeds acquired should first be dried at a tem-
will be directly associated to food scarcity. Kennedy et al. [7] the perature of about 50 °C. After that, the dried seeds were crushed
biodiesel was developed from water melon seed oil and showed and extracted the oil in hexane employing Soxhlet. The fuel gener-
higher CN and resistance to heat but very poor cold flow ability ated from watermelon seeds has low volatility as well as high vis-
than diesel. I.e. the combustion process inside the engine cylinder cosity. These difficulties can thus be solved by changing these seed
behaved a dynamic role in the emissions from the engine output. oils into biodiesel, the efficiency and properties of which are
The authors therefore concluded that watermelon seed oil biodie- almost identical to those of diesel. There are some approaches like
sel has proven to be one of the better combustion engine alterna- Dilution (blending), Pyrolysis (cracking), Transesterification and
tive fuels. Asokan et al. [8] studied the performance of diesel micro-emulsification that would typically be used to transform
engine, emission and combustion features fuelled with diesel/ oil to biodiesel. Among these processes, the transesterification
bio-diesel blends of watermelon and papaya seed oil and reported approach is more effective due to the high yield, low cost and short
that the combustion and performance properties of B20 is very reaction time.
nearby to diesel. In comparison to the characteristics of the B20 Transesterification is the technique of transforming oil or fat
blend emission, the emission of HC, CO and smoke is 23.8 percent, into biodiesel by cracking of molecules in to ethyl or methyl esters
27.27 percent and 8.3 percent lower for B20 than for diesel, relative with alcohol + catalyst with a by-product glycerol. The equation
to diesel. Also, the authors found that the higher CN of biodiesels illustrates (Fig. 1) the transesterification of watermelon seed oil
resulted in a smaller ignition delay as compared to diesel fuel. in to biodiesel.
Senthur Prabu et al. [9] inspected the effect of additives in DI Transesterification process was carried out in a conical flask
diesel engine on emission, combustion and performance behaviour (1000 ml) equipped with an agitator and thermometer. H2SO4
of diesel/preheated palm oil blends and stated that the blend PO20 and KOH are used as catalysts during transesterification reaction.
is the utmost superior blend of all other palm oil blends. The fuel Primarily, the methoxide (KOH and methanol) solution was pre-
additives like 20% n-butanol (vol.) and 2000 ppm of BHT were pared (5% vol.) in the existence of H2SO4 in an isolated bottle. This
added to the mixture PO20 to further improve the emissions of methoxide mixture is transferred in the conical flask containing
PO20. After addition of the additives the authors concluded that watermelon seed oil. Methanol to oil ratio 16:1 (molar ratio) was
the BTE and BSFC of PO20 + BHT blend is 5.1% and 11.4% greater maintained for effective transformation of tri-glycerides to di-
compared to diesel fuel. Alongside the emission CO of blend glycerides of the oil and heated to 60 °C for an hour at 700 rpm.
PO20 + n-butanol indicates 37.5% lower as well as the emission After the reaction period, the watermelon seed oil mixture was
NOx is 1.9% higher compared to diesel fuel. In addition to that moved to separating funnel and for 4 h it is allowed to settle the
the EGT and smoke is found to be 3.1% and 13% lesser than diesel. glycerin in the separating funnel at the bottom. Finally, the glycer-
Cheng et al. [10] studied the impact of biodiesel in DI diesel engine ine from the bottom is removed from the funnel and the water-
on NOx emissions and stated that the presence of fuel bound O2 in melon seed biodiesel leftovers in the separating funnel then it is
biodiesel generates more NOx emission during combustion. Sev- washed using the running water. Then the biodiesel was collected,
eral researchers explored the same issue and proposed various the yield was obtained up to 90%. Biodiesel was mixed with diesel
techniques to mitigate the NOx. For controlling the NOx, various
strategies are proposed towards reducing the in-cylinder tempera-
ture and pressure as well as a high peak heat release rate. For ex.
EGR is a common way employed for attaining reduced in-
cylinder temperature thereby controlling the emission NOx.
The novelty of this research work is to investigate the emission
and performance characteristic of single cylinder, four stroke, DI
diesel engine (1500 rpm) fuelled with watermelon biodiesel
(B100), diesel (B0) along with different blends WMB/diesel (B20,
B30, B40) at altered loads. Graphs of performance and emissions
of WMB have plotted.
Fig. 1. Transesterification chemistry.

Table 1 Table 2
Properties of WMB and diesel fuel. Engine specifications.

Properties WMB DIESEL Testing Procedure Make & Model Kirloskar (DI, water cooled) & TAF 1
Flash point °C 152 62 ASTM D93 Bore  Stroke (mm) 87.5  110 mm
Fire point °C 163 70 ASTM D93 Compression ratio 17.5:1
Kinematic Viscosity @ 40 °C (mm2/s) 5.65 2.75 ASTM D445 Connecting rod length & Vs 234 & 661 cm3
Calorific value (MJ/kg) 39.6 43.8 ASTM D240 Power & speed 5.2 kW & 1500 rpm
Density @ 20 °C (kg/m3) 890 830 ASTM D1298 Start of injection & pressure 24° bTDC & 21 MPa

2
M.A. Asokan, S. Senthur Prabu, V. Sai Akhil et al. Materials Today: Proceedings xxx (xxxx) xxx

Fig. 4. Brake specific fuel consumption Vs Load.

4.1. Performance analysis

4.1.1. Brake thermal efficiency

Fig. 2. Photographic view of engine setup.
The BTE of WMB/diesel blends at different load conditions are
showed in Fig. 3. The brake thermal efficiency increases propor-
to get different proportions of blends such as B100, B20, B30 and tionally with load for all the fuel blends. At full load operation,
B40. the BTE of B20, B30, B40, B100 and D100 are 32.5%, 31.75%,
From ASTM standards, the thermal and physical properties 30.1%, 29.5%and 33.4% respectively. It is observed that BTE of water
were examined and given in Table 1. WMB density is 1.1% more melon seed oil biodiesel blends slightly lesser than diesel fuel. The
compared to diesel and the diesel CV is more by 1.1% than that BTE of B20 showed very close diesel fuel among other blends
of WMB which intends that more quantity of WMB needs to be because of fuel physical characteristics almost in line with the die-
injected. Also, WMB has more kinematic viscosity than diesel. sel fuel. For B100 showed lower BTE than other tested fuel due to
Flash point of WMB is 152 °C i.e. fuels having more than 65 °C higher density, viscosity and lower heating values. Similar results
are safe for storage and handling. So, as safety aspect the biodiesel obtained by the researcher [11].
WMB is a better to diesel.
4.1.2. Brake specific fuel consumption
Fig. 4 shows the BSFC of WMB/diesel blends and diesel at 0 to
100% loads in the steps of 25%. The BSFC for all the tested fuels
3. Experimental setup are decreases with increasing loads up to 75% load and consumes
slightly more fuel at higher loads for all fuels. The BSFC records
The emission characteristics of watermelon biodiesel (B100), at 75% load for B20, B30, B40, B100 and D100 are 0.275, 0.28,
diesel (B0) along with different WMB/diesel (B20, B30, B40) blends 0.285, 0.295 and 0.255 kg/kWh respectively. It is witnessed from
at altered loads were studied in a constant speed (1500 rpm) 1- Fig. 4 that the BSFC of B20 shows lesser than other biodiesel blends
cylinder, 4-stroke diesel engine. A dynamometer is attached to and slightly higher than diesel fuel. Because of lower heating val-
the diesel engine for variable loads from 0 to 100% with a rise of ues of water melon seed oil biodiesel consumes more quantity of
25% load. Engine specifications and schematic diagram are speci- fuel to produce respective power. This result is in concurring with
fied in Table 2 and Fig. 2. previous studies [12].
Emission characteristics of WMB/diesel blends from the engine
like NOx, CO, HC, smoke opacity, EGT and CO2 were found from 5- 4.2. Combustion analysis
gas analyser (AVL digas 444). The smoke opacity of WMB/diesel
fuel blends was found using smoke meter and EGT was estimated 4.2.1. Cylinder pressure
using thermocouple. The cylinder pressure of WMB/diesel blends at full load is
showed in Fig. 5. WMB and its diesel blends are showed similar
pressure trend was observed to diesel trend for throughout the
4. Results and discussions experimental conditions. The peak cylinder pressure observed
from the test for WMB blends are B20, B30, B40, B100 and D100
Using WMB/diesel blends (B100, B20, B30 and B40) the emis- are 63.22 bar, 61.94 bar, 60.44 bar, 58.66 bar and 66.04 bar occurs
sion and performance test was conducted in a DI 4-stroke diesel at 40, 40, 30, 30 and 20 aTDC respectively and it found that peak
engine and compared with diesel (D100). pressure for all the fuels registers very nearer TDC. Due to high
cylinder pressure leads higher cylinder temperature and increases
the evaporation and mixing of fuels takes very quickly in the com-
bustion chamber produces perfect combustion [13]. And it is
observed that peak cylinder pressures for water melon seed oil bio-
diesel and its diesel blended fuel are lesser than diesel because of
lesser calorific value of biodiesel [8].

4.3. Emission characteristics

4.3.1. CO emission
Incomplete combustion is the major reason for CO emissions
from IC engines. Larger CO emissions causes in poor power of the
engine. The CO emissions of WMB with different loads are demon-
Fig. 3. Brake thermal efficiency Vs Load. strated in Fig. 6. The CO emissions at zero to 75% load almost sim-
3
M.A. Asokan, S. Senthur Prabu, V. Sai Akhil et al. Materials Today: Proceedings xxx (xxxx) xxx

Fig. 5. Cylinder pressure Vs Crank angle for full load. Fig. 9. Smoke opacity Vs Load.

4.3.2. HC emission
Fig. 7 illustrates the WMB HC emissions and its diesel blends
with diesel fuel. HC increases gradually from 25% load to 100% load
for all the WMB/diesel blends. At full load for B20, B30, B40, B100
and D100 are 80 ppm, 65 ppm, 50 ppm, 40 ppm and 110 ppm was
observed respectively. It is clear that biodiesel fuel decrease in HC
emissions compare to diesel because oxygen contains in the bio-
diesel helps to complete combustion. The formation of HC emis-
sion may be various factors like engine operating and
environmental conditions and air–fuel mixture and fuel properties
are the reason for increasing HC emissions [14].
Fig. 6. Carbon monoxide (CO) Vs load.

4.3.3. Nitrogen oxides emission (NOx)

Fig. 8 shows WMB NOx emissions and its diesel blends with die-
sel fuel with respect to loads. During combustion stage NOx emis-
sion is a very hazardous pollutant that must be reduced. The main
reason for the production of NOx is because of peak combustion
temperature and longer combustion period and local oxygen con-
centration. At low loads biodiesel fuels are not burned properly
due to its physical property hence NOx emissions during this stage
low or almost same compare to diesel fuel. If the load increases
NOx also increases and at higher loads of biodiesel blends B20,
B30, B40, B100 and D100 are 1920 ppm, 1950 ppm, 1975 ppm,
1900 ppm and 1800 ppm are recorded. This trend is somewhat
higher than diesel (D100) where biofuel is an oxygenated and
Fig. 7. Hydrocarbon Vs Load. has smaller ignition delay; it is predictable that pure biofuel blends
will lead to better burning and hence higher NOx [13].

4.3.4. Smoke opacity

ilar for all the fuels and found very less, at full load, it is observed
Fig. 9 shows the difference in smoke opacity of WMB vs load.
that for B20, B30, B40, B100 and D100 are 0.184%, 0.155%, 0.15%,
Development of smoke mainly depends on the oxygen concentra-
0.145% and 0.201% respectively. It indicates that, increasing mea-
tion in the fuel if more oxygen available in the fuel causes drop
sure of biodiesel in the fuel decreasing the CO emission from the
in smoke, It is evident from Fig. 9, biodiesel fuels shows less smoke
engine and found that diesel fuel releases more CO compare to
compared to diesel fuel are 70%, 68%, 65%, 58.9% and 86.5% for B20,
other biodiesel blends, this is because of biodiesel contains oxygen
B30, B40, B100 and D100 respectively. The outcome indicates that
and leads to complete combustion [14].
a rise in smoke because of reduction in O2 [15].

5. Conclusion

In this experiment, using transesterification process WMB is

produced. Fuel properties of water melon seed oil biodiesel are
tested under standard condition and these values are matched
with standard biodiesel specification. WMB/diesel blends (B20,
B30, B40 and B100) successfully used as a source of fuel in DI diesel
engine. The results from experiment revels that BSFC of B20 blend
at higher load is low compare to other blends which is 0.275 kg/
kWh, which is almost nearer to diesel which is 0.255 kg/kWh, at
75% load condition BSFC for all fuels are significantly low compare
to higher loads. Brake thermal efficiency of B20 (32.5%) gives better
performance which is greater than other WMB blends and slightly
Fig. 8. Nitrogen oxides Vs Load. less than diesel (33.4%). The combustion characteristics of biodie-
4
M.A. Asokan, S. Senthur Prabu, V. Sai Akhil et al. Materials Today: Proceedings xxx (xxxx) xxx

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source of bio-diesel, J. Power Energy Eng. 3 (2015) 24–27.
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and emission characteristics of diesel engine fuelled with papaya and
Senthur Prabu: Writing - review & editing, Supervision. watermelon seed oil bio-diesel/diesel blends, Energy 145 (2018) 238–245.
Vaigandla Sai Akhil: Methodology, Project administration. [9] S. Senthur Prabu, M.A. Asokan, S. Prathiba, S. Ahmed, G. Puthean, Effect of
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Declaration of Competing Interest
Engine Res. 7 (4) (2006) 297–318.
[11] M.A. Asokan, S. Senthur Prabu, P.K.K. Bade, V.M. Nekkanti, S.S.G. Gutta,
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kapok oil methyl ester/diesel blends, Int J. Oil, Gas and Coal Technology 12 (1)
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