The Effects of DTBP on the Pollutant of Diesel Engine
R N Li
*
, H Ding and Z Wang
School of Automotive and Traffic Engineer, Jiangsu University, Zhenjiang, 212013,
China
Abstract. Methanol and biodiesel, which are two of the oxygenated alternative fuels of
diesel, have the potential to reduce diesel engine emission. However, if methanol is blended
into biodiesel with a large proportion, the cetane number of the blend will be decreased a lot.
A cetane number improver - Di-Tert-Butyl Peroxide (DTBP) with the mass proportion of
0.25%, 0.50%, 0.75% was added into methanol/biodiesel blend with 15% methanol (BM15).
The engine bench test of the blend was finished in a 186FA type single-cylinder diesel engine
without any change, to investigate the effect of DTBP on the engine pollutant. It is revealed
that at the rated mode, DTBP can effective reduce NOx, CO and HC emissions, however the
exhaust smoke is increased a little.
1. Introduction
Energy shortage and environmental pollution are important issues facing the world, and even worse
in China. In 2016, China’s oil dependency on international oil market has already broken through
58%. It is estimated that this number will be near to 69% by the year 2020. More than a half of total
amount of fossil oil has been consumed by engines in China.
Methanol and biodiesel, both oxygenated fuels, are two of the promising alternative fuels. As an
alcohol fuel, potential resources of methanol are huge in China. Methanol is mainly produced from
coal, especially by the low-grade high-sulfur coal and recycling coke oven gas. China is abundant in
coal resources, but relatively less in fossil oil. Coal to methanol, which is with simple production
process and low cost, is a mature technology in chemical industry of China. Wang et al [1] studied
the reliability of diesel engine fueled with B5 biodiesel for 1000h, the result shows that B5 biodiesel
can be used in diesel engine, and the engine performance changes little. Özener’s [2] study also
shows that biodiesel could be used in diesel engine without any modification, and emission pollutant
can be reduced. As a kind of clean green energy, biodiesel has been got widespread attention and
become an important alternative fuel of diesel [3-5].
However, the cetane number of methanol is 5. When methanol is blended with a large proportion,
the cetane number of the blend will be decreased rapidly. The cetane number improvers can shorten
the ignition delay period and accelerate the combustion speed of the engine. 2,4-Di-tert-butylphenol
（DTBP） is a kind of cetane number improver which is most commonly used organic peroxide.
Liang etc.[6] added DTBP to diesel and studied the emissions of diesel engine. The study shows that
the diesel engine has the best comprehensive emission data when the mixed volume fraction of
DTBP to diesel is 0.3%.
308
Li, R., Ding, H. and Wang, Z.
The Effects of DTBP on the Pollutant of Diesel Engine.
In Proceedings of the International Workshop on Environmental Management, Science and Engineering (IWEMSE 2018), pages 308-312
ISBN: 978-989-758-344-5
Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

In this paper, DTBP was chosen to added into methanol/biodiesel blend, and the physical and
chemical properties of the blend were tested. A bench test was carried out on a direct injection diesel
engine and the pollutant of diesel engine were analyzed.
2. Material and methods
2.1. Fuel preparation
Referring to the existing research and through the test for methanol blending ratio, in this study, the
blending ration of methanol is 15%, and it is named as BM15. According to the researches [7, 8],
DTBP(C
8
H1
8
O
2
) can increase the cetane number of diesel fuel 6.5-8 by adding 1% (wt). In the test,
DTBP is added into BM15 with the ratio of 0.25%, 0.50% and 0.75%, named as BM15+DTBP0.25,
BM15+DTBP0.50 and BM15+DTBP0.75. The cetane number and LHV (lower heat value) of the
blends are calculated according to Kay’s mixing role. And the main properties of the fuels are listed
in table 1.
Table 1. Physical-chemical properties of the fuels.
Parameters DTBP BM15 BM15+DTBP0.25 BM15+DTBP0.50 BM15+DTBP0.75
Cetane numbe
r
- 43.25 44.38-44.75 46.00-44.75 47.63-44.75
Oxygen content (wt
%)
21.92 16.87 16.88 16.89 16.90
LHV (MJ·k
g
-1
) 32.67 34.74 34.74 34.73 34.73
Density (g·cm
-3
at
20°C)
0.80 0.86 0.86 0.86 0.86
Kinetic viscosity
(m
m
2
·s
-1
at 40°C)
3.32 3.22 3.22 3.22 3.22
2.2. Test apparatus and method
The engine bench test was carried out on 186FA diesel engine. The 186FA is a four strokes, air
cooled, direct injection, single-cylinder diesel engine, and the engine specifications are listed in table
2. The engine was operated at 3000 r/min with 10%, 25%, 50%, 75% and 100% load particularly.
The injection timing and fuel injection quantity of the engine were unchanged. During the
experiment, the pollutant concentration were recorded.
A type FGA4100 exhaust gas analyzer of was utilized to measure NOx, CO and THC
concentration online. The precision of exhaust gas analyzer for NOx, CO, and THC concentrations
was <4%, <5%, and <4%, respectively. The exhaust smoke was detected by a FBY-201 bosch smoke
meter.
Table 2. Engine specifications of 186FA.
Type
Direct-injected, 4 stokes,
ai
r
-cooled, natural aspiration
Number of cylinders 1
Cylinder bore(mm)×stroke(mm) 86×72
Displacement(L) 0.418
Compression ratio 19
Rated power(kW) / speed(r/min) 5.9/3000
Nozzle number × orifice diameter(mm) 5×0.20
Injection advanced angle (°CA BTDC) 12
Combustion chambe
r
ω type
The Effects of DTBP on the Pollutant of Diesel Engine
309

3. Results and discussion
3.1. NOx concentration
Figure 1 presents the NOx concentration of the diesel engine fueled with the fuels at 3000 r/min.
Figure 1 presents the effect of DTBP on NOx concentration. As can be seen, with the increase of
DTBP amount, the NOx concentration of the engine is reduced. When the engine is working at
3000r/min and Pe=0.57kW, and the addition of DTBP is 0.25%, 0.50% and 0.75% in BM15, the
volume concentration of NOx in exhaust gas is reduced by 2.59%, 7.58% and 10.2% compared with
that of BM15. This is because DTBP reduces the ignition delay period. Less mixture in the premixed
duration and the maximum pressure and temperature in the cylinder are reduced, resulting in the
reduction of NOx.
3.2. Smoke
Figure 2 is the smoke of the engine at 3000 r/min. It can be seen that with the increasing amount of
DTBP, the smoke of the engine is increased. When the engine is working at 3000r/min and
Pe=0.57kW, and the addition of DTBP is 0.25%, 0.50% and 0.75% in BM15, the exhaust smoke is
increased by 12.5%, 25% and 50% respectively compared with that of BM15. Study [9] has shown
that, OH has 3 times stronger ability than O to oxidize C2H2, and 20 times stronger than H. As C2H2
is the precursor of aromatic hydrocarbon, the oxidation reaction brakes the formation of aromatic
hydrocarbon, then reduces the amount of soot generated. In addition, OH also has strong oxidation of
the generated soot. All of the analysis above demonstrates that methanol has significant effect on the
inhibition of soot formation. When DTBP is added into BM15, the ignition delay period shortens.
Less mixture is in the premixed combustion period and more mixture is in the diffusion period,
making a little increase of soot.
Figure 1. NOx concentration. Figure 2. smoke number.
3.3. CO concentration
CO is an intermediate product of the fuel combustion and an product of incomplete combustion.
Figure 3 illustrates with the increasing amount of DTBP, the CO concentration is decreased
gradually. When the engine is working at 3000r/min and Pe=0.57kW, and the addition of DTBP is
0.25%, 0.50% and 0.75% in BM15, the volume concentration of CO in the exhaust is 0, 12.5%, and
25% lower than that of BM15. DTBP improves the ignitability of the blend and shortens the ignition
IWEMSE 2018 - International Workshop on Environmental Management, Science and Engineering
310

delay period. The low temperature and lean zone of the fuel spray is narrowed, accelerating the
combustion of CO. With the increase of engine load, the CO concentration is reduced first and then
increased a little at high load. When the engine fueled with BM15 at 25% load, the CO concentration
is increased a little compared with at 10% load.
3.4. HC concentration
HC is mainly produced by the mixture in the poor-oil area around the fuel spray, generated by the
incomplete combustion. As methanol has a low boiling point and high heat of vaporization, methanol
is easy to evaporate from the fuel droplet, and the evaporated methanol forms a low temperature,
lacking of oil area in the mixture [10, 11]. It is hard to combust completely for mixtures in such area,
and thus more HC can be formed. Figure 4 shows the HC concentration of the diesel engine. When
DTBP is added to BM15, the HC concentration of the engine is reduced. When the engine is working
at 3000r/min and Pe=0.57kW, and the addition of DTBP is 0.25%, 0.50% and 0.75% in BM15, the
volume concentration of HC in the exhaust is 5.0%,10.0%,20.0% lower than that of BM15.
Figure 3. CO concentration. Figure 4. HC concentration.
4. Conclusions
The cetane number improver (DTBP) was chosen to added into methanol/biodiesel blend, and the
physical and chemical properties of the blend were tested. The 186FA diesel engine bench test is
conducted at rated rotation to analyze the pollutant of the diesel engine using diesel, biodiesel and
methanol/biodiesel with or without DTBP. The results can be summarized as following:
(1) With the increase of DTBP amount, the NOx concentration of diesel engine is reduced, but soot is
increased a little.
(2) With the increasing amount of DTBP, the CO concentration is decreased gradually, and the HC
concentration of the engine is also reduced.
Acknowledgments
This study was financially supported by the National Natural Science Foundation of China under
Grant (No. 51776089), and the Project supported by the sixteenth undergraduate research project of
Jiangsu University(Y16A112).
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