International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 03, March 2019, pp. 392–403, Article ID: IJMET_10_03_040
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
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A STUDY ON ALCOHOL ACID COMPOUND
MIXED WITH BIODIESEL AS ALTERNATIVE
BIOFUEL FOR DIESEL ENGINE
Chang Chun Xu and Haeng Muk Cho
Division of Mechanical and Automotive Engineering, Kongju National University (KUN)
275, Budae-dong, Cheonan-si, Chungcheongnam-do 331-717, South Korea
ABSTRACT
In order to reduce the harmful effects on the environment, researchers around the
world must find ways to reduce emissions. For this reason, the EU allows the use of
biofuel mixtures as fuel for internal combustion engines. Therefore, an alternative has
been made in this study. Since biodiesel is used in experiments for the effect of internal
combustion engines on emission concentrations, it shows uncertain results. Due to the
performance of biofuels, such as combustion delays, injection times, fuel types, etc.,
for this reason, researchers have tried to add some alcohol compounds to biofuels for
investigation. Because biodiesel type of biofuel material has some FAME (fatty acid
methyl ester), it has some effects, such as high density and low calorific value,
although it has better emissions and reduced lubricity compared to pure diesel. But if
biofuel additives and alcoholic acid compounds affect the biofuel diesel ratio and
diesel injection time on combustion, performance and emissions. In this paper,
emissions of CO, CO2, NOX and unburned hydrocarbons are measured.
Key words: Alcoholic Acid Compound, Internal combustion engine, Exhaust
emission, Performance and Biofuel.
Cite this Article: Chang Chun Xu, Haeng Muk Cho, A Study on Alcohol Acid
Compound Mixed with Biodiesel as Alternative Biofuel for Diesel Engine,
International Journal of Mechanical Engineering and Technology 10(3), 2019, pp.
392–403.
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1. INTRODUCTION
During the operation of internal combustion diesel engines, a large amount of fossil fuel is
consumed, so they pose a threat to the environment in terms of pollutant emissions. In the past
few decades, the depletion and volatility of fossil fuels has led to a global concentration of
energy to find and find alternative fuels. Biofuels are one of the liquid fuels that can be used
in diesel engine vehicles. Whether the biofuel initially produced is produced directly from
food crops by fermentation (eg bioethanol) or transesterification as biodiesel [1]. The second
method of biofuel power generation is produced from agricultural products and some waste
such as wood, straw, corn and specific biomass crops, thus avoiding global concerns about
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food prices and scarcity. Due to their source derivatives, the important role of using this
biofuel can replace the petroleum fuel of internal combustion engines. Since the main
advantages of biofuels are regenerability, emissions from combustion and biodegradability
[2].
The use of alcohol (ethanol, methanol) and its mixture with diesel is another current
research model. When mixed with diesel, the alcohol, especially ethanol, becomes a
hygroscopic mixture, causing the fuel injector to become clogged. The use of biodiesel in a
diesel-ethanol mixture results in no stratification, paving the way for a ternary fuel mixture
known as an alcohol-diesel-biodiesel mixture, and reports many work with alcohol-dieselbiodiesel fuel mixtures [1].
Due to the high viscosity, low volatility and flammable diesel properties, it is difficult to
prepare a homogeneous premixed diesel/air mixture prior to ignition. Thus conventional
diesel combustion processes are mixed controlled diffusion combustion, and high NOx and
particulate matter can be generated due to high temperatures and locally enriched regions that
can affect engine exhaust emissions. As with the researchers, it is important that the reduction
in NOX and soot emissions form a fairly uniform charge prior to ignition. Therefore, by
research, alcoholic acid compounds are widely used in various alcohol substitutes because of
their improved volatility and latent heat. Therefore, the mixture can be displayed in the engine
as ethanol - biodiesel - diesel and methanol - biodiesel - diesel. Even though various
literatures focus on the development of ternary mixtures as alternative materials, these have
several disadvantages, such as phase separation, reduced calorific value of mixtures with
higher ethanol concentrations, and unreliability in storage and transportation. And the use of a
mixture of biodiesel can add alcohol which is very useful for reducing the viscosity and
density of biodiesel, which is higher than standard mineral diesel. And when the fuel is a
diesel engine, the alcohol additive increases combustion efficiency and produces lower
exhaust emissions. Compared to pure diesel, the oxygen content of ethanol and methanol is
about 35% and 30% higher, and due to high oxygen and high carbon number, diesel engines
can help diesel engines achieve higher complete combustion, thereby reducing ignition delay.
As for the combustion effect, carbon monoxide and carbon dioxide emissions can be reduced
due to high oxygen [3].
Alcohol is a liquid fuel that can be used in internal combustion engines [1]. The alcohol as
a fuel additive can be combined with a proportion of petroleum-based diesel, biodiesel and
diesel/biodiesel fuel mixtures to provide combustion as a fuel. At the same time, research on
the application of alcohol/diesel/biodiesel fuel mixtures has been carried out in the literature.
It has been pointed out that the viscosity and surface tension of the fuel and the alcohol as
additives are reduced while improving atomization and increasing the oxygen content. On the
other hand, low calorific value and cetane number, poor ignition quality, miscibility of the
alcohol and its own stability problems can limit the use in diesel engines. Alcohol is used as
an additive component of the fuel mixture in important processes to address fuel source
problems. In previous studies, methanol and ethanol as lower alcohols have been studied as
alternative fuels for diesel engines in the literature. Butanol and pentanol are good fuel
additives or attractive alternative fuels for diesel engines [3]. They have many advantages
over lower alcohols, such as higher cetane number and calorific value, and lower heat of
vaporization. Therefore, recent research on the use of butanol and pentanol in diesel engines
has increased [2].
Butanol, also known as n-butanol, n-butanol or butanol, is an alcohol that is available
from renewable sources. It is colorless and transparent and immiscible with water. Butanol
has a moderate non-permanent odor. It has been used as a solvent in the fields of plastics,
cosmetics, coatings and foods, mainly for the production of isobutyl acetate. In addition, it
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can be added to materials used for rust and abrasion. Butanol is a toxic alcohol. It tends to
burn. The calorific value of butanol is lower than that of diesel, and the heat in diesel can be
as high as 40%. In addition, the properties of butanol are very close to diesel fuel[3].
Pentanol is also known as n-pentanol, n-pentanol or pentanol. It can be made from
renewable raw materials. Pentaerythritol has a higher cetane number and energy content than
other alcohols. Up to 45% can be used by adding diesel fuel[8].
Worldwide, there are many studies on the analysis of engine performance, combustion
and exhaust emissions characteristics of diesel engines using different fuels (eg biodiesel,
diesel, biodiesel/diesel blends, alcohol/biodiesel/diesel blends, etc.). On the other hand, the
number of studies on the use of butanol and pentanol in diesel engines is limited[8].
So some of these studies were summarized follow below: Zhu et al. [11] analyzed the
emission and combustion characteristics of a four-cylinder four-stroke diesel engine fueled by
a waste cooking oil biodiesel-pentanol mixture. They detected the onset of fuel combustion
and removed the maximum exothermic crank angle from top dead center. As the proportion of
pentanol in the fuel mixture increased, the pressure and heat release rate in the cylinder
increased. Although the hydrocarbon (HC) and CO emissions of the fuel mixture have
improved, NOx emissions are more severe. Atmanli et al. [12] used n-butanol and crude
rapeseed, soybean, sunflower, corn, olive and hazelnut oil to make a vegetable oilmicroemulsification of a diesel fuel mixture. 70% diesel fuel, 20% vegetable oil and 10% nbutanol mixture are fully loaded in a four-cylinder four-stroke turbocharged direct injection
diesel engine with various engine speeds. The experimental results show that braking torque,
braking power, braking thermal efficiency (BTE), braking average effective pressure
(BMEP), exhaust gas temperature (EGT), HC and CO reduction, and braking ratio fuel
consumption (BSFC), NO and CO increase compared to diesel fuel.Imdadul et al. [13]
analyzed the addition of 10%, 15% and 20% of Tamani oil biodiesel and pentanol to diesel
fuel and examined the engine performance of a single-cylinder water-cooled diesel engine
operating with test fuel and Exhaust emissions. According to B20 fuel, BSFC values, smoke
opacity, CO, HC and CO2 emissions of alcohol blended fuels decreased by 8.7, 21.2, 33.1,
43, 45 and 2.5%, respectively. However, thermal efficiency, braking power and NO emissions
increased by 15%, 10.4% and 4.4%, respectively. Imdadul et al. [14] produced biodiesel from
Tamani oil by transesterification and mixed 15% and 20% by volume with conventional
diesel fuel. Butanol and pentanol in a ratio of 15% and 20% were added to the mixed fuel. All
test fuels are placed in a single cylinder four stroke direct injection diesel engine. It was
finally determined that adding alcohol would reduce BSFC values, increase braking power,
NO and CO2 emissions, and reduce CO and HC emissions compared to B15 and B20
fuels.Ibrahim [15] studied the effects of 10% and 20% butanol addition in biodiesel-diesel
fuel mixtures on engine performance, exhaust emissions and combustion characteristics of
single-cylinder diesel engines. During the course of the study, the addition of up to 20%
butanol resulted in certain changes in engine performance, exhaust emissions and combustion
characteristics. On the other hand, they found that it was necessary to optimize the diesel
engine using butanol, and the change in fuel type had no significant effect on the combustion
period.Wei et al. [16] found that the addition of pentanol and fuzzy increase NOx emissions,
and increased braking power, reducing CO and HC emissions.Mehta et al. [17] reported that
by adding n-butanol to the mixture, HC emissions increased while CO and smoke emissions
decreased.Kumar and Saravanan [18] comprehensively reviewed the use of higher alcohols in
diesel engine applications. They point out that the replacement of diesel fuel in whole or in
part with higher alcohols in compression-ignition engines has been found to be generally
successful because higher alcohols reduce conditioning emissions and increase
efficiency.Yilmaz et al. [19] studied the effects of adding 5%, 10% and 20% butanol to waste
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cooking oil biodiesel on the performance and emission characteristics of indirect injection
diesel engines. Compared to biodiesel fuels, it was determined that EGT and NOx emissions
decreased with the addition of butanol, but CO and HC emissions increased. In addition, the
fuel mixture has a higher BSFC value than diesel fuel.Ozer [20] compares the engine
performance and exhaust emissions of diesel engines for diesel engines by adding 3, 5, 8 and
10% butanol to diesel at different engine loads. The results indicate that the BSFC increases
due to an increase in the proportion of butanol in the fuel mixture. Although thermal
efficiency and EGT are reduced. It has also been found that CO, NOx and smoke opacity are
reduced, although CO2 and HC emissions are increased.Li et al. [21] have different emissions
and combustion characteristics for single-cylinder direct-injection diesel engines under
various engine loads and constant speeds of 1600 rpm, adding the effect of adding pentanol to
biodiesel and diesel fuel. As a result of the experiment, a 40% diesel-30% biodiesel-30%
pentanol mixture exhibited better combustion and emissions data as well as engine
performance.Keskin et al. [22] tested diesel engine fuel with two different fuel mixtures. This
shows that the use of a fuel mixture reduces engine torque and power values compared to
conventional diesel fuel. In addition, they showed a slight increase in NOx emissions, but
smoke opacity, CO and HC emissions decreased by 87.5%, 87.01% and 57.14%,
respectively.Sahin et al. [23] studied the effect of n-butanol injection into diesel engine intake
on engine performance and exhaust emissions under different engine loads. Therefore, in
terms of engine characteristics, 2% n-butanol injection will be the optimum mixing ratio, and
NOx emissions will be reduced by 0.58%, 0.31% and 17.38%, respectively. On the other
hand, they show that the thermal efficiency increases by 1.01%.Tosun et al. [24] conducted
experiments by adding 20% alcohol by volume to biodiesel produced from scrub oil. Engine
power was found to increase by 2.4%, 10%, and 12.8% compared to biodiesel in experiments
with methanol, ethanol, and butanol, and 26.36%, 20.85%, and 18.91, respectively, compared
to diesel fuel. %. Compared with biodiesel, the engine torque values of methanol, ethanol and
butanol blends increased by 1.2%, 3.4% and 6.1%, respectively, and were reduced by 20.53%,
18.81% and 16.67%, respectively, compared to diesel fuel. In addition, as the alcohol mixture
is discharged, CO emissions are reduced and NOx emissions are increased. Atmanli [25]
prepares a fuel mixture such as 50% diesel + 50% biodiesel, 40% diesel + 40% biodiesel +
20% different alcohol, and naturally inhales in a four cylinder at a constant engine speed of
1800 rpm. Testing and various engine loads are performed in indirect injection diesel engines.
The paper concludes that the addition of propanol, butanol and pentanol increased CO
emissions by 39.95%, 38.83% and 12.60%, respectively, but NOx emissions were reduced.
Nanthagopal et al. [26] showed the effects of 1-pentanol and 1-butanol as additives and
chlorophyll biodiesel on diesel engine characteristics under different engine loads. They point
out that higher alcohol biodiesel blends have lower BTE and higher BSFC. Due to the cooling
effect of higher alcohols, NOx simultaneously reduces CO, HC and smoke emissions from all
higher alcohol blends. Babu and Anand [27] analyzed the performance, combustion and
exhaust emissions behavior of diesel engines operating on biodiesel/diesel/n-pentanol or nhexanol mixtures without engine modifications. They concluded that performance and
combustion performance can be improved by adding higher alcohols to the biodiesel/diesel
mixture. Among the higher alcohol blends, 85% biodiesel / 5% diesel / 10% pentanol fuel has
the smallest CO, HC and filtered smoke. Dhanaseharan et al. [28] studied the effects of waste
cooking oil biodiesel, diesel and n-pentanol ternary mixture on the combustion, performance
and emission characteristics of fixed direct injection diesel engines with and without exhaust
gas recirculation. It can be concluded that the ternary mixture produces less NOx and smoke
emissions, but HC and CO emissions are found to be higher. In addition, they improved the
BSFC after adding n-pentanol according to B50 fuel. Atmanli et al. [29] suggested that the
ternary mixture contains 10% n-butanol / 20% cotton oil / 70% diesel fuel to meet the engine's
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cold flow performance and provide satisfactory engine performance and emissions. Celebi
and Aydin [30] prepared a binary mixture of butanol/safflower oil biodiesel/diesel fuel,
including the volume basis of 5%, 10% and 20% butanol. They then performed a half load
and a constant speed test at 1500 rpm on a four-cylinder four-stroke direct-injection diesel
engine generator. The ternary mixture showed a reduction in emissions observed, with higher
BTE and BSFC recorded at 1.5% and 6%, respectively, compared to diesel fuel.
According to the various scholars' research above, most of the previous studies have
focused on (a) increasing the impact of alternative fuel concentrations; (b) using the same
percentage of different alternative fuels and (c) mixing the effects of different alternative
fuels. Biodiesel adds a small amount of alcohol with the same oxygen concentration (but
different fuels C, H and LHV). According to the author's knowledge and research, all of these
studies were carried out with a mixture of different carbon (C) and hydrogen (H) percentages,
different from the oxygen (O) content and the different low calorific value (LHV).
Differences in C, H, O, and LHV do not allow for the establishment of similar conditions to
compare engine performance and exhaust emissions during various fuel usage periods. Engine
performance and exhaust emissions are affected by many factors, including the C/H ratio of
the fuel, the oxygen content of the fuel, and the lower calorific value. In addition, under the
same operating conditions, there is still a lack of research on the effects of lower alcohols
(methanol and ethanol) and higher alcohols (butanol, pentanol and propanol) on the same
engine.
The effects of low-grade alcohols such as methanol and ethanol added to diesel, biodiesel
and diesel biodiesel blends on engine performance, exhaust emissions and combustion
characteristics were investigated. Research on diesel engines fueled with diesel, biodiesel or
diesel-biodiesel fuel blends with butanol and pentanol fuels has been limited, especially in
terms of the impact on fuel combustion characteristics and engine performance. Study engine
performance (such as torque, power, BSFC, BTE, etc.), exhaust single-cylinder, four-stroke,
water-cooled, direct-injection diesel engine emissions (such as CO, CO2, NOx, etc.) and
combustion behavior (such as in-cylinder pressure and Heat release rate).
2. COMBUSTION CHARACTERISTICS
Usually, the following parameters are usually selected in the research process to analyze the
effects of alternative fuels on engine combustion characteristics and performance: in-cylinder
pressure, heat release rate (HRR), ignition delay (ID), combustion duration (DOC), coefficient
of variation ( COV)) Indicative mean effective pressure, brake specific fuel consumption
(BSFC) and brake thermal efficiency (BTE)[5].
The combustion process includes ignition delay (ID), uncontrolled combustion, controlled
combustion, and late combustion. During the ignition delay, fuel is injected into the
combustion chamber and evaporated by mixing with air. The ignition delay time is the time
span between the start of fuel injection and the start of fuel ignition[7]. In other words, the
ignition delay is the primary rate at which sudden pressure increases are observed. During this
time, the physical and chemical processes required to prepare the fuel for combustion work.
There is a temperature difference between the pressure of the fuel injected into the
combustion chamber and the temperature at which the temperature is increased during
compression. During the evaporation of the fuel, the temperature of the heat overflows the
temperature difference. The heat extracted during this transfer process, to some extent, slows
the increase in temperature and pressure within the cylinder. Other important parameters in
diesel engine combustion analysis are start of injection (SOI), start of combustion (SOC), end
of combustion (EOC), and combustion period (CP)[7].
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The ID is lowered due to an increase in the in-cylinder temperature due to an increase in
engine load. For DOC, an increase in load results in fuel injection duration, air/fuel mixture
formation, and increased fuel combustion [7]. Compared to diesel fuel, due to the alcohol, the
lower cetane number of the mixed fuel and the higher latent heat of vaporization cause a
decrease in the in-cylinder temperature and an increase in the ID. For DB, higher bulk
modulus and higher biodiesel viscosity result in earlier combustion onset and lower ID. There
are various reasons for using alcohol to reduce DOC in a blended fuel. First, the addition of
alcohol to the mixed fuel results in a higher HRR in the premixed combustion stage caused by
the longer ignition delay. Second, faster flame propagation of the alcohol can shorten the
DOC. Third, the oxygen content of the alcohol can reduce the pyrolysis process and enhance
oxidation during combustion, resulting in a shorter DOC.
For BTE, the higher or similar BTE of the blended fuel (although the BSFC is increased)
is due to lower fuel viscosity, improved fuel atomization and increased oxygen content, which
improves the combustion process that converts the chemical energy of the fuel into fuel[12].
Useful engine work increases the BTE compared to ULSD. Among all the alcohols tested,
methanol has the shortest chain and the lowest molecular weight, which results in easier
ignition and better combustion, thus resulting in the lowest BSFC and the highest BTE[13].
Furthermore, the lowest boiling point of methanol in the tested alcohol results in a reduction
in heat loss, thus resulting in a higher BTE. At lower loads, the lean fuel-air mixture produces
lower combustion, which reduces brake thermal efficiency. As the load increases, fuel
consumption increases to maintain a constant speed, which in turn increases the combustion
temperature, causing the brake thermal efficiency to increase until the maximum limit is
reached. After the maximum brake thermal efficiency is reached, incomplete combustion
occurs due to the rich fuel mixture and reduced air fraction, which in turn reduces the brake
thermal efficiency[5]. According to experiments, it was observed that the baking heat
efficiency of diesel fuel was lower than that of biodiesel and fuel mixture. The brake heat
efficiency in biodiesel is the highest. This may be due to the high oxygen content of the
pressure. Higher concentrations of oxygen in biodiesel increase the combustion temperature,
which in turn produces higher braking thermal efficiency than diesel. However, the addition
of 1-butanol reduces the brake heat efficiency by absorbing more heat generated due to high
heat of vaporization. As with higher mixtures, the brake thermal efficiency is lower than
biodiesel, but these values are higher or closer to the brake thermal efficiency of the diesel
engine. Due to the higher heat of vaporization, more heat is absorbed, which reduces the
thermal efficiency of braking. The addition of 1-butanol reduces the cetane number, which
reduces combustion efficiency, which is another reason to reduce the thermal efficiency of the
brake. For the remaining fuel, specific fuel consumption was found to be higher due to the
lower heating value. When 1-butanol is added to the diesel, the heat of vaporization increases.
This, in turn, can absorb more heat during combustion and result in a further increase in
specific fuel consumption at the same rating. This results in providing a greater amount of
fuel mixture to maintain the same braking power. Therefore, biodiesel blends consume more
fuel than diesel fuel.
At low engine loads, the combustion temperature is low, so incomplete combustion
occurs; on the other hand, under very high loads, the combustion temperature is high and the
fuel/air ratio is richer, but there is not enough time to mix the fuel and air, resulting in
incomplete combustion, BTE is reduced and BSFC is increased[20].
The exhaust gas temperature of diesel is lower than that of biodiesel. Diesel does not
contain oxygen and produces a lower exhaust gas temperature. Due to the higher density and
viscosity of biodiesel, poor atomization was observed in biodiesel combustion [23]. This in
turn leads to incomplete or delayed combustion. Therefore, even after the expansion, the
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combustion continues, which may raise the exhaust gas temperature. However, the 1-butanol
mixed test fuel showed a lower exhaust temperature than biodiesel and was higher than the
percentage of diesel. The heat of vaporization, oxygen content and viscosity (poor
atomization) can affect the temperature of the exhaust gas. The 1-butanol/diesel blend has a
higher oxygen content and is expected to have more heat inside the cylinder. However, due to
the higher heat of vaporization, more heat is absorbed and the temperature of the exhaust gas
is lower than the temperature of the biodiesel. As the engine load increases, more fuel is
injected into the cylinders for combustion, which causes the in-cylinder temperature to rise
and thus increase the EGT. As the engine load increases, more fuel is injected into the
cylinders for combustion, which causes the in-cylinder temperature to rise and thus increase
the EGT[20].
Figure 1 Brake thermal efficiency [3]
Figure 2 Brake Specific Fuel Consumption [3]
Figure 3 Exhaust Gas Temperature [3]
3. EMISSION CHARACTERISTICS
Figure 4 shows that NOX decreases roughly with increasing load, which is consistent with
other studies using diesel and DBE and diesel, DBu and DPe. Figure 4 also shows that all
blended fuels (except for DB under all loads, DBPe of 28.5 Nm) resulted in a lower NOx
reduction for all test loads than diesel fuel. At an average of five loadings, the NOX reductions
using the blended fuel were 19.3% (DBPr), 14.2% (DBM), 11.7% (DBPe), 4.7% (DBE) and
(DBBu), respectively, compared to diesel. There was an increase in NOX (5.8%). Although
the combustion temperature has a large influence on the formation of NOx, it can be found
from the above results that the length of the combustion duration (residence time) also has an
influence on the formation of NOx[27].
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Reductions in NOx have also been reported in studies using ethanol, butanol and pentanol,
and butanol and propanol. In addition, the increase in NOX using biodiesel has also been
reported in many of the studies mentioned in the review articles[21][23].
Figure 4 Variation of NOX with engine loads. [1]
Figure 5 shows the change in CO2 with engine load. It can be seen from Figure 5 that
under different engine loads, the behavior of CO2 is almost similar to that of BSFC. It was
also found that the lowest CO2 record was 199.5 Nm (which also had the lowest BSFC) and
the highest CO2 was observed at 28.5 Nm of all tested fuels (which also had the highest
BSFC). Figure 5 also shows that all blended fuels (except DB) can reduce CO2 compared to
diesel fuel. References report similar trends in reducing carbon dioxide with ethanol and
DBE. A slight increase was found in the reference and there was no significant CO2 effect.
Compared to diesel, pure biodiesel (up 5.63%), DB50 (up 2.77%) and DB20 and DB10
(same) were used. In addition, DB has the same CO2 compared to diesel (a slight increase of
1.4% compared to the test). It can be inferred that only DBM is effective in reducing CO 2 by
an order of 8.2% due to the lowest BSFC in all tested fuels. The effect of other blended fuels
on carbon dioxide is almost similar to that of diesel [1][3].
Figure 5 Variation of CO2 with engine loads [1]
In Figure 6, it can be seen that the effect of in-cylinder temperature rise and complete
combustion as a consequence of engine load rise (except 256.5 Nm) on CO emissions
reduction. At an average of five loadings, the CO reduction for all alternative fuels was DBM
(23.9%), DB (11.3%), DBPr and DBBu (6.4%), DBPe (3.5%) and DBE (0.4% only),
compared with diesel. Under low load, the lower combustion temperature (due to the higher
cooling potential caused by latent heat of evaporation) affects the oxygen content of the
blended fuel [29]. The effect of (complete combustion), which inhibits the CO oxidation
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process, resulting in increased CO emissions from diesel. However, as the engine load
increases, the effect of combustion temperature becomes weaker and the mixture can be seen
at higher test loads. The CO emissions of fuels are lower than the CO emissions of
ULSD[31].
Figure 6 Variation of CO with engine loads [1]
Figure 7 depicts that an increase in load results in a decrease in HC for all tested fuels. At
low engine loads, the combustion temperature is not sufficient to initiate complete
combustion, resulting in an increase in HC emissions for all tested fuels. However, at higher
loads, the combustion temperature is high enough to achieve more complete combustion,
resulting in a lower HC of all tested fuels.
Figure 7 shows that all blended fuels (regardless of ethanol of 85.5 Nm) can reduce HC
from 85.5 Nm to the highest engine load (256.5 Nm). The increase in HC at the lowest load of
a mixed fuel is similar to that of CO because the latent heat of vaporization of alcohol and
biodiesel is higher than that of ULSD, resulting in incomplete combustion [27]. However, the
effect of higher oxygen content in the blended fuel is the dominant factor for higher engine
loads (from 85.5 Nm to 256.5 Nm), which leads to more complete combustion and increased
unburned hydrocarbons at higher in-cylinder temperatures [30]. Some studies have also found
that when using alcohol mixtures (such as DBE, DBBu and DBPe and BPn), THC increases
at lower or even moderate loads and decreases at higher loads. In addition, other studies have
found that using DE and DBE, DBPe and diesel mixed with ethanol or methanol can improve
combustion quality compared to diesel fuel because of the higher oxygen content in the fuel
and lower THC [28]. Among the average of the five engine loads, HC was reduced by DBM
(24.3%), DBPe, DBPr and DB (12.3%) and DBE and DBBu (8.8%) compared to diesel fuel.
Figure 7 Variation of HC with engine loads [1]
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4. CONCLUSIONS
Recently, alternative fuels have become a prospect due to the rapid decline in fossil fuel
reserves, rising oil prices, stricter emission regulations, increasing pollution of traditional
fuels to the environment and concerns about energy security. These anxieties have led
scientists to study alternative fuels. One of the most important alternative fuel sources for
internal combustion engines is higher alcohols because of their environmental and economic
advantages. 1-butanol and n-pentanol are higher alcohols and can be prepared from renewable
feedstocks having a molecular structure of four and five carbons, respectively.
The addition of 1-butanol slightly reduced brake thermal efficiency compared to pure
biodiesel and reduced specific fuel consumption, exhaust gas temperature and emissions of all
test gases such as NOx, CO and HC. In this survey, fuel characteristics indicate that alcohol
treatment slightly reduced kinematic viscosity, density, calorific value, flash point and cetane
number. However, the addition of alcohol to the biodiesel/diesel fuel mixture can reasonably
improve low temperature performance. The 1-butanol and n-pentanol treated fuels have
elevated BSFC values and are on average higher than diesel fuels. And the results are
predicted due to the calorific value of the fuel sample. Most ternary mixtures have a lower
BTE than diesel fuel.
Compared to diesel fuel, the addition of n-pentanol and 1-butanol fuels significantly
reduced CO emissions while observing a reduction in CO2 emissions from the fuel mixture.
Due to the higher alcohol, the addition of n-pentanol is effective in reducing NOx
emissions. In addition, the smoke opacity of the alcohol treated fuel mixture is reduced on
average compared to diesel fuel.
ACKNOWLEDGMENT
This work was supported by the National Research Foundation of Korea(NRF) grant funded
by the Korea government(MSIT) (NRF-2019R1A2C1010557).
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