Critical Thinking

EFFECT evaluation of previous research studies on different

EFFECT
OF VARIOUS NON-EDIBLE BIODIESEL BLENDS WITH DIESEL ON PERFORMANCE AND EMISSION OF
COMPRESSION IGNITION DIESEL ENGINE: A REVIEW

O.P.Jakhar1, Ashish
Kumar2

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1Associate
Professor, Govt. Engineering College, Bikaner, Rajasthan

2M.Tech.
Scholar, Govt. Engineering College, Bikaner, Rajasthan

 

ABSTRACT

In the automotive
sector direct injection compression ignition engines are used as a power generation
source. Increasing fuel prices and limited sources of fuels raised the
attention of researchers towards renewable energy sources such as biodiesel. In
addition to this, there is a requirement of a clean alternative fuel due to the
hazardous environmental impact of diesel emissions. The objective of this
review paper is to represent performance and emissions of various non-edible biofuels
which are named as second generation biodiesels with blends of diesel. This
paper analyzes performance parameters such as BTE, BSFC, BP and emissions of
HC, CO, CO2, NOX by comparative evaluation of previous
research studies on different biodiesel blends with diesel. The previous
research studies showed that different biodiesel feedstocks give different
results to compression ignition engine performance and emissions. Most
investigation has been shown that use of biodiesel with fossil diesel has many
advantages like enhancing engine performance, reduce emissions, lower engine
wear and lower fuel consumption over diesel fuel. The research study concluded
that biodiesel blends with diesel can be used in compression ignition engine as
a replacement of diesel fuel due to its renewable, non-noxious, biodegradable,
sustainable and eco-friendly characteristics.

Keywords:
Non-Edible Biodiesel, Transesterification, Compression Ignition Diesel Engine,
Emission.

I.     
INTRODUCTION

With
the rapid rise in world population and industrial growth, the world is
confronted with an alarming energy crisis. According to International Energy
Outlook 2017 between 2015 and 2040, world energy
consumption increases by 28%, with more than half of the increase attributed to
non-OECD Asia (including China and India). World energy consumption increases
from 575 quadrillion British thermal units (Btu) in 2015 to 663 quadrillion Btu
by 2030 and then to 736 quadrillion Btu by 2040. Not surprisingly, rate
of consumption of oil is higher than the production growth and this has
resulted in surge in petroleum fuel price. Oil
prices rise to $109/barrel (real 2016 dollars) in 2040. Total liquids
consumption increases from 191 quadrillion Btu in 2015 to 228 quadrillion Btu
in 2040, when it accounts for 31% of total world energy use. The transportation
sector remains the largest consumer of refined petroleum and other liquids as
their use for travel and freight services increases at a faster rate than their
use in other applications between 2015 and 2040. In India Oil consumption in 2014 stood at 3.8 million barrels per
day (mb/d), 40% of which is used in the transportation sector. Demand for
diesel has been particularly strong, now accounting for some 70% of road
transport fuel use 1,2.

Out of various energy conversion
devices, diesel engine has some outstanding characteristics, such as higher
thermal efficiencies, low specific fuel consumption, high compression ratio, utilization
of leaner air-fuel mixtures, reliability and low operating and maintenance cost
assures its utility in power generation, automobile sector, farm tech
machineries in agriculture, rail transport, military, telecommunication
generator sets, ships etc. Despite of having tremendous superiorities, diesel
engine emits large quantity of pollutants (NOx, CO2, CO, HC) which
causes serious health hazardous and environmental degradation. World energy related carbon dioxide (CO2)
emissions are projected to grow an average 0.6%/year between 2015 and 2040,
1.3%/year below the level from 1990 to 2015. Liquids related CO2
emissions grow an average 0.7%/year between 2015 and 2040. On the other hand, India is the third-largest country in
volume terms of CO2 emissions
in the world, behind only China and the United States 1,2. One of the main
reasons for global warming is the exhaust emissions generated from the
automotive vehicles. It has been also reported that, an increase in average
global temperature by 2 °C will result in death of hundreds of millions of
people. The reduction of CO2 emissions makes the most vital
contribution to global warming 3.

Currently biodiesel is seen
as a solution of such problems and almost every country is preparing a policy
on production and use of biodiesel in its transport sector. Biodiesel is
mainly methyl ester of triglycerides prepared from animal fat and virgin or
used vegetable oils (both non-edible and edible) 4. It can be used in diesel
engines as a single fuel or as a diesel-biodiesel blend. Triglycerides being substance with high viscosity can be
converted to biodiesel with lower viscosity by transesterification reaction. Biodiesel
is one of the renewable, nontoxic and environmental friendly and sustainable
alternative biofuels that can be used in a diesel engine with little or no
modification in the engine 5,6. Combustion of biodiesel in engines leads to
lower smoke, carbon monoxide (CO), carbon-di-oxide (CO2) and hydro carbon
(HC) emissions, but higher nitrogen oxide (NOx) emission, keeping engine
efficiency unaffected or improved 7,8,9.
Among the biodiesel properties, kinematics, viscosity, density and heating
value are the most important parameters that affect the engine performance and
the emission characteristics 10. This review paper represents
performance and emission characteristics of a CI diesel engine using non-edible
biodiesel such as karanja, jathropha, castor, neem.

 

II. BIODIESEL FEEDSTOCKS

Biodiesel feed stock can be classified as first generation, second
generation and third generation 11. The
first generation sources include the edible food crops such as sunflower,
coconut, olive,

soybean, and rapeseed, while second generation are usually non edible
type and non-edible plant parts such as jatropha, karanja, neem, jojoba, linseed,
cottonseed, castor, thumba, trice husks, and palm fiber etc. Waste cooking oil,
animal fats and water oil as well as microalgae form the third generation kinds
of sources 12. Table 1 shows various properties of diesel and biodiesel
which are discussed in this paper.

 

Table 1 Comparison of
properties of biodiesel with diesel fuel 11-28.

Vegetable
oil
 

Density
(kg/m3)
 

Viscosity
at 40 0C (mm2/s)
 

Flash
point (0C)
 

Cloud
point
(0C)
 

Pour
point
(0C)
 

Cetane
number
 

Calorific
value
(MJ/kg)

Diesel

816–840

2.5–5.7

50–98

-10
to -5

-20
to 5

45–55

42–45.9

Karanja
(Pongamia pinnata )

876–890

4.37–9.60

163–187

13–15

-3
to 5.1

52–58

36–38

Jatropha
(Jatropha curcas)

864–880

3.7–5.8

163–238

5

46–55

38.5–42

Castor
(Ricinus communis)

932

15.069

182

38.6-39.1

Neem
(Azadirachta indica)

912–965

20.5–48.5

34-285

12

8

51

33.7–39.5

 

III. TRANSESTRIFICATION
REACTION

Vegetable oils cannot
be used in IC engine directly due to the higher viscosity, lower volatility and
higher polyunsaturated characteristics. Hence, it has been
recommended by many researchers to transesterify vegetable oils to reduce the high
viscosity of the oil 13. The most advanced and promising technology of biodiesel
production is transesterification of oils (triglycerides) with alcohol which
gives biodiesel (fatty acid alkyl esters, FAAE) as main product and glycerole as
byproduct. Transesterification, also called alcoholysis, is exchanging of
alcohol from an ester by another alcohol in a process similar to hydrolysis, except
that analcoholis used instead of water 14. Generally, in order for the reaction
to be completed in a shorter reaction time, a catalyst is used to enhance and improve
there action rate. Reaction temperature, reaction time, reaction pressure, ratio
of alcohol to oil, concentration and type of catalyst, mixing intensity and kind
of feedstock are among the most relevant operating variables affecting the transesterification
process. The inclusive transesterification reaction
can be deliberated by three consecutive and reversible Eqs. (1)–(3):

Triglyceride (TG) + ROH             Diglycerides (DG) + RCOOR1                                       (1)

Diglycerides (DG) + ROH            Monoglyceride (MG) + RCOOR2                                  (2)

Monoglyceride (MG) + ROH           glycerole
+ RCOOR3                                                   (3)

 

IV. ENGINE PERFORMANCE AND EMISSIONS

When selecting biodiesel its availability and economic aspects are
considered first. The characteristics of engine performance are then
considered. Brake power, brake thermal efficiency (BTE), and brake specific
fuel consumption (BSFC) are the performance indicators. Factors such as
air–fuel mixture, fuel injection pressure, fuel spray pattern, and fuel
properties affect performance. Biodiesel is an oxygenated fuel. Therefore, it
produces a complete combustion, provides excellent emission properties, and creates
less negative environmental effects. Different experimental investigations on
engine performance and emission characteristics using the reviewed non-edible
oil biodiesels are presented.

 

1.  Karanja Biodiesel

Karanja oil is obtained from the seeds
of Pongamia pinnata tree, native to the tropical and Asia which offers most
suitable climate for its growth. Each fruit of medium sized Karanja tree (18 m
height) contains 1–2 kidney shaped brownish red kernels with an oil content of 30
to 40%. The BSFC is increased with increasing proportion of Karanja oil in the
blend due to lower calorific value of Karanja oil 15. The brake thermal efficiency
of the higher Karanja oil blends is observed to be lower than that of diesel
fuel. Karanja oil blends emitted more CO and CO2 than the pure
diesel. Smoke opacity and NOx concentration are found to be lower
and higher respectively for lower Karanja oil blends compared to mineral diesel
at all loads. It is suggested that lower blends (up to 20%) of Karanja oil can
be used as alternate fuel to the mineral diesel supplies 16.

     Sureshkumar
et al. 17 observed an increase in BSFC up to B40 from the experiments
conducted on a single cylinder, four stroke, water cooled engine with various
blends of Pongamia pinnata methyl ester (PPME). This could be due to presence of
higher dissolved oxygen in the biodiesel that enables complete combustion. B20
blend emit less CO emission (~50% at 50% load) than diesel fuel.  A reduction of (~8.67%) NOX emission
is observed with B20 biodiesel blend as compared to diesel. Higher density, viscosity
and surface tension of the biodiesel lead to lower BTE (~ upto 6.49%). Chauhan et
al. 18 reported that except NOX emission (28.73%), the CO
(77.52%), HC (76.66%) and smoke emissions (36.5%) decreased significantly for
all biodiesel-diesel blends.

 

2.
Jatropha Biodiesel

Jatropha
name is derived from the Greek word; approximately it is about 170 species of
plants, shrubs and trees. Most of this species native belongs to America and
belongs to the Euphorbiaceae family. Jatropha curcas grows in tropical and
subtropical regions and also in sandy and saline soils. Its seed production under
cultivation is about 1.5–2.5 t per hectare, corresponding to oil yields of
500–720 l per hectare. Biodiesel from Jatropha is mainly initiated by Indian
government, because of its rich oil content (66.4%) 19 and it grows in
non-agricultural lands. Agarwal et al. observed higher BSFC than that of diesel
fuel 20. In addition to this the brake thermal efficiency of preheated
Jatropha oil is found to be slightly lower than that of diesel. While smoke
opacity, CO, CO2 and HC emissions of JOME are observed to be higher
compared to those of diesel fuel 21.

Ong et al. 22 study showed a slight
increase in torque and a clear improvement in power and BSFC for B10. The
reason for reduction in BSFC indicates the complete combustion for B10 and the
author concluded that the 10% blends produce the best engine performance
compared to other blends. Jindal et al. 23 observed that the BSFC decreased
at higher compression ratio (of 18). At these conditions, the BSFC and BTE
values are improved by about 10% and 8.9% respectively than that of standard
setting (17.5 CR and 210 bar injection pressure) of the engine. The HC 24, NOX
emissions and smoke opacity are lowered by 50%, 25% and 10% respectively. These
emission reductions are due to higher oxygen content, which helps in better
combustion of the fuel. The CO and CO2 emissions are increased by about 38% and
2% respectively. The increase in CO emission is attributed to the incomplete
energy conversion and poor diffusion flame combustion. It can be inferred from
these experimental investigations on Jatropha that there is slight decrease
(2–3.5% of BTE) in engine performance but with improved emission
characteristics.

 

3. Castor
Biodiesel

Castor
oil is obtained from the seed of Ricinus communis plant which belongs to the
Euphorbiaceae family. This is native to south-eastern Mediterranean Basin,
India and Africa and it is widespread throughout all tropical regions of the
world. The oil yield is about 40–60% from the seeds that are rich in
triglycerides mainly ricinolein (greater than 85%) and also ricin, a water
soluble toxin with lesser concentrations. Panwar et al. 25 conducted
experiments and results showed that lower blends of biodiesel (up to B10) is
capable of reducing the BSFC (about 18.68% with B5 blend) and increasing BTE
(up to 3.54%) compared to that of diesel fuel. However addition of the
biodiesel more than 10% decreased brake thermal efficiency (about 7.74% for
B20) and increased BSFC. All the biodiesel blends (except B5) increased the
exhaust gas temperature and hence increase in NOX emissions. Decrease
in CO, HC emissions and increase in NOX emission are also observed
to be 37% (B30), 20.9% (B10), 52% (B30) and 11.31% (B30) respectively 26. Since
the performance characteristics of castor seed oil biodiesel is closer to that
of diesel fuel the author suggested using castor oil blends in CI engines in
rural area for meeting energy requirement in agricultural applications.

 

4. Neem
Biodiesel

The
neem tree (Azadirachta indica) is a tropical evergreen with a wide
adaptability, native to India and Burma. The neem
plant is a fast growing plant with long productive life span of 150–200 years,
its ability to survive on drought and poor soils at a very hot temperature of
44 0C and a low temperature of upto 4 0C, and its high
oil content of 39.7–60%. A mature neem tree produces 30–50 kg fruit every year.

Dhar et al. 27 evaluated the performance
and exhaust emission characteristics using diesel as the baseline fuel and
several blends of biodiesel from neem oil in single cylinder diesel engine. Increased
BTE and reduced BSFC were observed for all blends compared to pure diesel. At lower
engine loads, CO emissions for all biodiesel blends are close to pure diesel. At
higher engine loads, all the biodiesel blends except 50% blend show significant
reduction in CO emissions. Increase in the emission of NOX and
decrease in HC emission were observed in comparison with pure diesel for all biodiesel
fuelled engines.

Jayashri et al. 28 evaluated the
performance and emission characteristics of neem biodiesel using various blends
(B10, B20, B30) and observed that the BSFC for diesel as well as B10 blend is
less than B20 & B30 at all loads. An average increase in brake thermal
efficiency of B10 and B20 for all loads was noted to be 34% against diesel.
Average reduction in CO emissions for B10, B20, B30 was 26%, 22%, 5%
respectively. On an average HC emissions are reduced compared to that of diesel
by 17%, 10% and 9% for B10, B20, B30 respectively. On an average NOX
emissions are reduced compared to those of diesel by 21.875%, 8.375% and
18.875% for B10, B20, B30 respectively. It is concluded that B10 showed higher
performance and lower emissions than other blends and diesel.

 

V. CONCLUSION

This
paper provides a comprehensive literature review of performance, combustion and
emission characteristics of diesel engines fuelled with non edible biodiesel
and its blends as alternate fuels for diesel engines. Biodiesel produced from
non-edible oil resources can defy the use of edible oil for biodiesel
production. Therefore, its demand is growing steadily, and researchers are
looking for possible newer sources of non-edible oil. This review concludes
that non-edible oil is a promising source that can sustain biodiesel growth.

Several studies were carried out to
determine brake power output, BSFC, and BTE of an engine operating with
non-edible oil-based biodiesel. In most cases, jatropha biodiesel gave higher
BSFC but had better thermal efficiency than other biodiesels. Their brake power
and torque were closer to those of diesel fuel because of their calorific value.
Moreover, the low percentage of biodiesel blends (

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