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THE INFLUENCE OF ETHANOL ADDITIVES ON THEPERFORMANCE AND COMBUSTIONCHARACTERISTICS OF DIESEL ENGINESLü Xingcai a; Huang Zhen a; Zhang Wugao a; Li Degang aa School of Mechanical and Power Engineering, Shanghai Jiaotong University,Shanghai, People's Republic of China

Online Publication Date: 01 August 2004To cite this Article: Xingcai, Lü, Zhen, Huang, Wugao, Zhang and Degang, Li(2004) 'THE INFLUENCE OF ETHANOL ADDITIVES ON THE PERFORMANCEAND COMBUSTION CHARACTERISTICS OF DIESEL ENGINES', CombustionScience and Technology, 176:8, 1309 - 1329To link to this article: DOI: 10.1080/00102200490457510

URL: http://dx.doi.org/10.1080/00102200490457510

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THE INFLUENCE OFETHANOL ADDITIVESON THEPERFORMANCE ANDCOMBUSTIONCHARACTERISTICSOFDIESEL ENGINES

L�XINGCAI*, HUANG ZHEN, ZHANGWUGAO,ANDLIDEGANG

School of Mechanical and Power Engineering,ShanghaiJiaotong University,Shanghai, People’s Republic of China

The purpose of this paper is to experimentally investigate the engine pollutant

emissions and combustion characteristics of a diesel engine fueled with

ethanol=diesel blended fuel. The experiments were performed using various

proportions of ethanol=diesel blended fuels in a single-cylinder direct injection

(DI) diesel engine. The engine performance parameters and emissions were

measured and compared to those using the baseline diesel fuel. To gain insight

into the combustion characteristics of ethanol=diesel blends, the engine

combustion processes for blended fuels and diesel fuel were observed using an

engine video system (AVL 513). The results show that the brake specific fuel

consumption increased at overall engine operating conditions, but it is worth

noting that the brake thermal efficiency increased by up to 1–2.3% with 10

and 15% ethanol=diesel blended fuels. It is found that engines fueled with

ethanol=diesel blended fuels have higher emissions of total hydrocarbon

(THC), and lower emissions of CO, NOx, and smoke. The results also indicate

that the cetane number improver has a positive effect on CO and NOx

emissions, but a negative effect on THC emission. Based on the engine

combustion visualization and in-cylinder temperature field analysis by using

the primary color method, it is found that the ignition delay increased, the

Received 26 June 2003; accepted 5 February 2004.

This study was financially supported by the National Nature Science Foundation of

China—Ford Foundation (No. 50122166) and the Key Project of the National Nature

Science Foundation (No. 50136040). The authors wish to express their gratitude to Li Bing

and Yang Ronghua for their contributions to this paper.

*Address correspondence to [email protected]

Combust. Sci. andTech., 176: 1309^1329, 2004

Copyright#Taylor & Francis Inc.

ISSN: 0010-2203 print/1563-521X online

DOI: 10.1080/00102200490457510

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total combustion duration and the luminosity of the flame decreased, and the

peak combustion temperature decreased for ethanol=diesel blended fuels.

Keywords: diesel engine, ethanol=diesel blended fuel, emission, combustion

visualization, temperature field, primary color method

INTRODUCTION

The degradation of the global environment and foreseeable future

depletion of worldwide petrol reserves provides strong encouragement to

search for alternative fuels that are friendly to the environment bur can

be used forever. Ethanol is one of the ideal fuels for both diesel and

gasoline replacement in compression ignite (CI) or spark-ignition

engines; it has been used to fuel engines since the birth of the automotive

industry (Schuetzle et al., 2002).

The global oil crisis in the 1970s triggered the need to develop

alternative fuels in order to defend against the vulnerability to oil

shortages. In the mid-1970s, considerable attention has been focused on

ethanol fuels. The major advantages of ethanol as an engine fuel are as

follows: (1) Ethanol is a renewable energy source; it can be made from all

kinds of raw materials such as sugarcane, molasses, cassava, waste bio-

mass materials, sorghum, corn, barley, sugar beets, and soforth, using

already improved and demonstrated technologies. As a result, local

agriculture industries can be supported and framing incomes can be

enhanced. (2) Use of ethanol provides better energy security for many

developing countries.

Recently, ethanol has been used in gasoline engines worldwide.

Gasohol improves the octane rating and engine thermal efficiency and

reduces the exhaust emissions dramatically (Poulopoulos et al., 2001). In

the 1980s, some research efforts investigated ethanol used in diesel

engines (Eugene et al., 1984). The main obstacles of ethanol used in CI

engines are listed as follows:

1. Ethanol has limited solubility in diesel fuel. Phase separation and

water tolerance in ethanol=diesel blended fuel are crucial problems.

2. Ethanol fuel has an extremely low cetane number, whereas diesel

engines prefer a high-cetane-number fuel that autoignites easily and

gives small ignition delay.

3. The dynamic viscosity of ethanol is much lower than that of the diesel

fuel, so lubricity is a potential concern of ethanol=diesel blended fuel.

1310 L. XINGCAI ET AL.

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There are several techniques involving ethanol=diesel dual fuel

operation: (1) neat ethanol fuels were used in CI engines by using a Sonex

Combustion System (Lu and Pouring, 1996), (2) dual separated injection

system is used for each fuel, displacing up to 90% of diesel fuel demand,

(3) ethanol is added to the intake air charge by means of a carburetor or a

control valve, and (4) ethanol=diesel blended fuels mix two fuels prior to

injection.

In recent years, with the development of technology, a number of

researchers have investigated ethanol=diesel blended fuels used in CI

engines (Abu-Qudais et al., 2000; Ajav et al., 1998, 1999). Particularly,

AAE Technology Corporation (Rae, 2002), Pure Energy Corporation

(Ahamed, 2002), Akzo Nobel Surface Chemistry (Lofvenberg, 2002), and

Lubrizol Corporation (Corkwell et al., 2002) have developed and pro-

duced a low-cost additive that makes it possible to blend ethanol with

diesel to get a stable and clear fuel. Subsequently, the ethanol=diesel

blended fuel can be used in diesel engines. However, there are few studies

on engine combustion characteristics for ethanol=diesel blended fuel.

Due to aforementioned background, the purpose of this paper is to

evaluate the effects of ethanol=diesel blended fuels and the cetane number

improver on engine emissions, performance parameters, and combustion

characteristics. Toward this end, an experimental study was performed

on a single-cylinder direct injection (DI) diesel engine fueled with various

proportions of ethanol=diesel blended fuels.

FUEL-BLENDINGPROCEDURE

Usually, the blending of ethanol and diesel fuel is limited to essentially

anhydrous ethanol because ethanol is not soluble or has very limited

solubility in the diesel fuel. The solubility of the ethanol=diesel mixture is

dependent on the hydrocarbon composition of the diesel fuel, wax con-

tent, and ambient temperature. This solubility is also dependent on the

water content of the blend fuels. Phase separation is a crucial issue for

ethanol=diesel blended fuels, so that the solubilizer in indispensable in

blended fuel.

Commercial diesel fuel and analysis-grade anhydrous ethanol (99.7%

purity) were used in this test. The blended fuels were formed by blending

together the three components: diesel fuel, ethanol, and solubilizer. The

blending protocol was first to blend the solubilizer (1.5% v=v for all

ethanol=diesel blended fuels) into the ethanol and then blend this mixture

INFLUENCE OF ETHANOL ADDITIVES ON DIESEL ENGINES 1311

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into the diesel fuel. For example, 15% ethanol=diesel blended fuel (E15-D)

contains 1.5% solubilizer, 15% anhydrous ethanol, and 83.5% diesel fuel

by volume. To investigate the effects of cetane number (CN) of blended

fuel on engine performance and emissions, 0.2% CN improver was added

into 15% ethanol=diesel blended fuel (E15-DþCN improver) and

compared to the 15% ethanol=diesel blended fuel without CN improver

(E15-D).

The presence of ethanol generates different physicochemical mod-

ifications of the fossil fuel, notably reductions of the CN, lower heat

content, viscosity, flash point, pour point, and so forth. These mod-

ifications changed the spray evaporation properties, combustion perfor-

mance, and engine-out emissions. Therefore, some basic properties of

ethanol=diesel blended fuels were measured, and the lower heat values of

blended fuels were calculated. The fuel density was measured by

weighting a known volume of oil; the oil viscosity was measured by using

a dynamic viscometer. The measurement principle consisted of measuring

the time needed for a known volume of oil to drop from a viscometer.

The flash point was measured by using a close-up method, and the sur-

face tensions of fuels were measured by a surface tensiometer. The oil

density, surface tension, and dynamic viscosity were measured at 20�C,

all the measurements were repeated at least three times, and the average

results are shown in Table 1.

EXPERIMENTAL SYSTEM

A single-cylinder DI diesel engine was employed in this study; the engine

specifications are shown in Table 2 and the experimental system is shown

Table 1. Physical and chemical properties of ethanol, diesel fuel, and blended fuels

Abbrev.

Density

� 103 kg=m3

Surface

tension

mN=m

Flash

point

(�C)

Viscosity

(cP)

Lower

heat value

(MJ=kg)

Diesel 0.841 32.3 78 3.35 42.5

5% Ethanol=diesel E5-D 0.833 30.8 17 3.23 41.1

10% Ethanol=diesel E10-D 0.831 30 16 3.05 40.3

15% Ethanol=diesel E15-D 0.829 29.3 15.5 2.79 39.5

20% Ethanol=diesel E20-D 0.828 29 15 2.49 38.7

Ethanol 0.789 27 13–14 1.20 26.8


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in Figure 1. The engine was coupled to an electrical generator through

which load was applied by increasing the field voltage. The engine per-

formance and emissions at various loads under different engine speeds

(2200 and 1760 rpm) using ethanol=diesel blended fuels and diesel fuel

were investigated. The measured parameters including engine speed,

torque, fuel consumption, exhaust temperature, oil temperature, BOSCH

smoke number, carbon monoxide (CO), oxides of nitrogen (NOx), and

total hydrocarbon (THC). To gain the same rated power output of dif-

ferent blended fuels, the injection duration was adjusted for each tested

fuel, but the start of injection was kept constant at each measuring point

for all tested fuels.

Exhaust emissions taken at the exhaust pipe were sampled using an

AVL CEB gas analyzer, which measures concentrations of CO, NOx, and

Table 2. Specifications of the test engine

Bore� stroke 100 (mm)� 115 (mm) Displacement 0.9 (l)

Compression ratio 17.5:1 Injector open

pressure

18.1MPa

Rated power (kW) 12.1 kW=2200 rpm Advanced angle

of injector open

20�CA BTDC

Max torque 58.9Nm=1760 rpm Nozzle number

orifice diameter

4� 0.32 (mm)

Figure 1. Schematic diagram of the experimental system.


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HC emissions. At each measuring point, the average value 3min after the

engine operated stably was used as the measured results. The air flux at

each operating condition was measured by an AVL airflow meter. An

AVL gravimetric fuel flow meter was used for fuel consumption mea-

surement; a BOSCH smoke meter was used to measure the smoke

emissions. Both the smoke number and fuel consumption at each oper-

ating were measured at least three times, and the average value was used

as the experimental result.

RESULTS ANDDISCUSSION

The engine output was calculated using the following formula:

Pe ¼M� n

9549ð1Þ

The brake specific fuel consumption (BSFC, g=k W�h) was computed as

BSFC ¼ 1000� _MMf

Peð2Þ

The brake thermal efficiency can be calculated as follows:

Ze ¼3:6� 103 � Pe

_MMf �Hu

ð3Þ

where Pe is the brake power (kW), M is torque ðN �mÞ, n is engine speed

(rpm), _MMf is fuel flow rate (kg=h), and Hu is lower heating value.

Brake Specific Fuel Consumption

Figure 2 shows the relationship between BSFC and various engine loads

at 2200 and 1760 rpm for different blended fuels and diesel fuel. The

BSFC shows a decrease with an increase in engine load, but a slight

increase after 75% load at 1760 rpm. It is evident that the BSFC of

ethanol=diesel blended fuels increases with the increase of ethanol con-

tent in blended fuel. This is due to the fact that the lower heat value of

ethanol is about two-thirds that of diesel fuel. The second explanation,


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which has been offered for the remarkable increase at lower load under

2200 rpm, is the incomplete combustion due to the prolonged ignition

delay of ethanol=diesel blended fuels. Moreover, it is found that there is

no distinct effect of the CN improver on BSFC.

BrakeThermal Efficiency

The engine brake thermal efficiency (BTE) of diesel engine fueled with

blended fuels and diesel fuel are shown in Figure 3. It indicates that the

BTE improved at medium and large loads at 2200 rpm. Particularly, the

Figure 2. BSFC versus engine load for ethonal=diesel blended fuels and neat diesel.


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BTE of 15% ethanol=diesel blended fuels with and without CN improver

increased from 37.2 to 39.5% at full load at 2200 rpm. The BTE for all

blended fuels improved about 1–1.5% (absolute) from low load to full

load at 1760 rpm.

These results show that the engine BTE can be enhanced remarkably

by means of adding ethanol to diesel fuel. This can be explained by the

following reasons:

1. The combustion is more complete in the fuel-rich zone due to the

oxygen content of ethanol, so that the combustion efficiency is

enhanced.

Figure 3. Brake thermal efficiency versus engine load for blended fuels and neat diesel.


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2. Evaporation properties of blended fuels may improve because the

boiling point of ethanol is lower than that of the diesel fuel.

3. Heat losses decrease in the cylinder due to the lower flame temperature

of ethanol fuel compared to that of diesel fuel.

Smoke Emission

Figure 4 illustrates smoke emission versus engine load for various ethanol

additions. It can be seen that smoke can be remarkably reduced with

ethanol addition to diesel fuel at large load. There was an average

reduction of the smoke number of above 50% at all loads under 2200 rpm

for the E15-D, E15-DþCN improver, and E20-D. The smoke number

decreases remarkably at relatively large loads under 1760 rpm for blended

fuels. Because smoke is mainly produced in the diffusive combustion

phase, obviously the addition of ethanol will supply more oxygen, which

leads to an improvement in diffusive combustion.

Gas Pollutant Emissions

According to the legislative test for gas pollutant emissions of a single-

cylinder diesel engine, an ‘‘8-mode test’’ was used for the measurements,

and the AVL CEB gas analyzer was used as the measuring device. The

weight factors and modes presented in Table 3; the results are shown in

Table 4.

It can be seen from Table 4 that both CO and NOx emissions, which

were measured using the 8-mode test, are reduced for ethanol=diesel

blended fuels compared to the diesel fuel, but THC increased dramati-

cally. When the CN improver was added to the ethanol=diesel blended

fuel, CO and NOx emissions were further reduced by up to 21 and 7%,

respectively, and THC increased by up to 50.5%. To get insight on the

effects of ethanol=diesel blended fuels and the CN improver on engine

emissions, the authors analyzed the emission characteristics at main

operating conditions.

CO emissions at various loads under different engine speeds are

presented in Figure 5. At rated speed, CO increased by up to 95.5 and

36.7% at 10 and 50% load with E15-D; it increased 58.7 and 24% at the

same load for E15-DþCN improver when compared to the diesel fuel.


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Figure 4. Relationship between smoke and ethanol contents in blended fuels and neat diesel.

Table 3. Weight factors and modes of the emission test

Mode no. 1 2 3 4 5 6 7 8

Speed Rated

speed

Rated

speed

Rated

speed

Rated

speed

Max

torque

Max

torque

Max

torque

Idle

Relative

power

100% 75% 50% 10% 100% 75% 50% 0

Factor 15% 15% 15% 15% 10% 10% 10% 10%


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Figure 5. CO emissions versus engine load with ethanol=diesel blended fuels and neat diesel.

Table 4. Engine emissions of blended fuels and comparison with the diesel fuel

CO NOx THC

Result

(g=kWh)

Changed

%

Result

(g=kWh)

Changed

%

Result

(g=kWh)

Changed

%

Diesel 5.32 — 10.04 — 0.97 —

E10-D 4.46 7 16.7% 9.81 7 2.3% 1.41 þ 45.4%

E15-D 5.01 7 5.8% 9.62 7 4.2% 1.37 þ 41.2%

E15-DþCN improver 4.22 7 21% 9.30 7 7% 1.46 þ 50.5%


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At higher load under rated speed, CO decreases significantly with an

increase of load for ethanol=diesel blended fuels. Moreover, at full load,

CO decreases slightly more for E10-D than for 15% ethanol=diesel blend

fuel with and without the CN improver.

At 1760 rpm, CO emissions at full load are very high. For

ethanol=diesel blended fuels, CO emissions slightly decrease at 75% load

and full load, and CO emissions of 15% ethanol=diesel blend fuel with

CN improver are lower than that of the blended fuel without CN

improver. In general, the following characteristics of CO emissions for

ethanol=diesel blended fuels can be obtained.

1. CO emissions are increased at low and medium loads, but reduced at

large and full loads when compared to the diesel fuel.

2. For blended fuel with CN improver, CO emissions are lower than that

of the blended fuel without CN improver at overall engine operating

conditions.

NOx emissions of the engine using different ethanol=diesel blended

fuels and diesel fuel at various operating conditions are shown in Figure 6.

Obviously, it can be seen that the general tendency of NOx emissions is

opposite to that of CO emissions. For an engine speed of 2200 rpm, NOx

emission of ethanol=diesel blended fuels reduced about 50–60% and 32–

35% at low load and medium load, respectively, but reduced a small

amount at 75% load. At full load, NOx is slightly higher for blended fuels

than that of diesel fuel. A similar tendency can be seen for an engine

speed of 1760 rpm. Furthermore, NOx emissions for blended fuel with

CN improver are slightly lower than blended fuel without CN improver

at overall engine operating conditions.

Figure 7 gives the effect of ethanol on THC production. It can be

found that with the introduction of ethanol in diesel, the THC emissions

increased at various engine conditions. For 15% ethanol=diesel blended

fuel with CN improver, the THC levels are higher than 15%

ethanol=diesel blended fuel without the CN improver. The increase of the

THC levels is a result of incomplete combustion of the blended fuel at

low load and medium load.

Comparing the CO emissions and NOx emissions for blended fuels at

various operating conditions from Figures 5 and 6, for a specific oper-

ating condition, it is of interest to note that the NOx emissions decrease

with the increase of CO emissions at low and medium loads, but NOx


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slightly increases with the decrease of CO at large and full loads. Another

interesting phenomenon is that the cetane improver has a positive effect

on CO and NOx emissions.

COMBUSTION IMAGES ANDANALYSIS

To understand the effects of ethanol on engine performance and emissions,

combustion behavior was observed by using direct photography. There is

Figure 6. NOx emissions versus engine load with ethanol=diesel blend fuels and neat diesel.


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no modification of engine parameters except for a new cylinder head,

which allows optical access to the combustion chamber by using an

endoscope-based measurement system. The measurement system is an

AVL EVS 513. Optical accessibility to the combustion chamber was

accomplished by an additional port through the cylinder head at an angle

of 56� to the horizontal, as seen in Figure 8. The combustion images of

15% ethanol=diesel blended fuels with and without CN improver and

diesel fuel under the same operating conditions are shown in Figure 9. The

combustion characteristics of blended fuels that can be seen from the

engine combustion processes are as follows:

Figure 7. THC emissions versus engine load with ethanol=diesel blend fuels and neat diesel.


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1. Ignition delay. The most apparent change of the combustion be-

havior when burning ethanol=diesel blended fuels is an increase in

the ignition delay time. At 12.2� CA before top dead center

(BTDC), the flame has developed everywhere in the combustion

chamber for neat diesel, but the combustion did not start until 9.8�

CA BTDC for E15-D and 11.8� CA BTDC for E15-DþCN im-

prover, respectively.

2. Combustion duration. It is evident from the figure that the combus-

tion duration for both ethanol=diesel blended fuels decreased. The

flame can be seen during 9.8�–3.8� CA BTDC for E15-D and

11.8�–2.2� CA BTDC for E15-DþCN improver, respectively. One

explanation for the decreased combustion duration is the larger pre-

mixed burn associated with the increase in ignition delay. The other

possible reason is the enhanced mixing resulting from the

‘‘microexplosion’’ of the blended fuels (Daly and Nag, 2001).

3. Luminosity. Combustion images revealed that the luminosity of the

flame decreased with the ethanol=diesel blended fuels relative to diesel

fuel. This means that the soot emission decreased when the engine was

fueled with ethanol=diesel blended fuels.

To understand the distribution of the temperature field in a cylinder,

the primary color method was used to calculate the temperature field for

ethanol=diesel blended fuel and neat diesel fuel.

Figure 8. Optical access through cylinder head.


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Figure

9.Flameim

ages

duringthecombustionprocess

forethanol=dieselblended

fuelsandneatdiesel.

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According to Planck, the total radiation from an object is (Xiaofang

and Zhou, 1997)

Iðl;TÞ ¼ elC1

l5 exp C2

lT � 1� �� ð4Þ

where C1 [Wm2] stands for Planck’s first constant; C2 [Km] is Planck’s

second constant; Iðl;TÞ½W=m2� is the intensity of monoradiation; T [K] is

absolute temperature; el, monoemissivity; and l, wavelength. Generally,

the monoemissivity of an object is a function of temperature and wave-

length:

el ¼ fðl;TÞ ð5Þ

Equations (5) and (6) tell us that the spectrum distribution of an object’s

radiation is a function of temperature and emissivity. The spectrum

distribution causes the visual ‘‘color’’ effect vision within the range of the

visible light. The color of the object depends on the spectrum distribution

of radiation. That is to say, the color of an object is the single-value

function of the object’s emissivity and temperature.

Three colors, which are independent of each other, are selected. They

are blended according to different proportions to cause different color

sensations. The wavelengths of the primary colors selected by Interna-

tional Commission on Illumination (CIE) are (Anquan et al., 2002)

lR ¼ 700:0 nm lG ¼ 546:1 nm lB ¼ 435:8 nm

The color of a spectral composition PðlÞ is specified by the following

three chromaticity coefficients:

R ¼Z780 nm

880 nm

rðlÞPðlÞdl

G ¼Z780 nm

880 nm

gðlÞPðlÞdl

B ¼Z780 nm

880 nm

bðlÞPðlÞdl

ð6Þ


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Where rðlÞ; gðlÞ, and bðlÞ are spectral tristimulus functions of a

1931 CIE [RGB] system standard observer. As a common object abides

by Planck’s law, its color coefficient can be found when it gives out

chromatic light at high temperature:

R ¼Z780 nm

880 nm

rðlÞelC1

l5 exp C2

lT � 1� �� dl

G ¼Z780 nm

880 nm

gðlÞelC1

l5 exp C2

lT � 1� �� dl

B ¼Z780 nm

880 nm

bðlÞelC1

l5 exp C2

lT � 1� �� dl

ð7Þ

The preceding formulas show that the color of the object caused by

the radiation of itself is decided by the object’s radiation spectrum. On

Figure 10. Comparison of the temperature for blended fuels and diesel fuel at 8.00 CA

BTDC at the same operating conditions.


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the other hand, the temperature and monoemissivity of the object can be

obtained by measuring the object’s color coefficient and applying the

least-squares method to solving the preceding equations. This is the

fundamental of temperature measurement based on primary colors.

Figure 10 presents the in-cylinder temperature field at the same crank

angle with the same working conditions. From the figure, it can be seen

that the pixels of the diesel combustion flame are mainly located between

2000 and 2500�C; the pixels of the E15-D flame are mainly located

between 1800 and 2100�C; and the temperature of E15-DþCN improver

is higher thanE15-D, but lower than that of diesel fuel, because the pixels of

the combustion flame are mainly located around 2000�C. From Figure 11,

it can be found that the maximum mean in-cylinder temperature of

ethanol=diesel blended fuels is much lower than that of diesel fuel, and

the rate of temperature increase along with the combustion history is

lower than that of diesel fuel.

CONCLUSIONS

This work was undertaken to study and compare the effects of etha-

nol=diesel blended fuels and CN improver on BSFC, BTE, exhaust

emissions (smoke number, CO, NOx, and THC), and combustion

Figure 11. The mean in-cylinder temperature for different fuels.


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characteristics in a single-cylinder diesel engine. The following conclu-

sions can be drawn from this study:

1. The BSFC of ethanol=diesel blended fuels increased for the reason

that the low heat value of ethanol is only two-thirds that of diesel.

However, the BTE of the engine fueled with ethanol=diesel blends

increased by up to 1–2.3% at medium and larger loads.

2. There was a remarkable decrease in engine smoke emission at overall

engine operating conditions when the diesel engine used ethanol=diesel

blended fuels.

3. The results of the 8-mode tests for ethanol=diesel blends and diesel

fuel show that CO emission decreased by 21 and 5.8%: NOx reduced 7

and 4.2% for 15% ethanol=diesel blended fuels with and without CN

improver, respectively; but THC increased significantly.

4. CO emissions increased at low and medium loads, but decreased at

large and full loads when the engine was fueled with ethanol=diesel

blended fuels. On the contrary, NOx emissions decreased at low and

medium loads, but increased at large and full loads. THC increased at

various loads under different engine speeds for blended fuels.

5. Typical characteristics of ethanol=diesel blended fuels include

increased ignition delay and decreased combustion duration and

luminous flame when observed using the engine video system.

6. Based on the analysis of the temperature field using the primary color

method, it was found that the maximum temperature of ethanol=diesel

blended fuels is much lower than that of diesel fuel.

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