A fundamental study of injection, spray, and combustion characteristics of hydrotreated vegetable oil under simulated diesel engine conditions :Doctoral Dissertation - Major: Machanical Engineering

A FUNDAMENTAL STUDY OF INJECTION, SPRAY, AND COMBUSTION

CHARACTERISTICS OF HYDROTREATED VEGETABLE OIL UNDER

SIMULATED DIESEL ENGINE CONDITIONS

VO TAN CHAU

A THESIS SUBMITTED IN FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE

OF DOCTOR OF ENGINEERING IN MECHANICAL ENGINEERING

FACULTY OF ENGINEERING

KING MONGKUT’S INSTITUTE OF TECHNOLOGY LADKRABANG

2017

KMITL-2017-EN-D-058-218

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COPYRIGHT 2017

FACULTY OF ENGINEERING

KING MONGKUT’S INSTITUTE OF TECHNOLOGY LADKRABANG

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Thesis title A Fundamental Study of Injection, Spray, and Combustion

Characteristics of Hydrotreated Vegetable Oil under Simulated

Diesel Engine Conditions

Student Mr. VO TAN CHAU

Student ID 56601360

Degree Doctor of engineering

Program Mechanical Engineering

Year 2017

Thesis Advisor Asst. Prof. Dr. Chinda Charoenphonphanich

Thesis Co-advisor Prof. Dr. Kosaka Hidenori

ABSTRACT

Fossil fuels have been the essential source of energy in the global development for

centuries. However, along with the continual rise in the fossil fuels consumption come

the pollution and the environmental degradation. Thus, attempts have been made to

mitigate the fossil fuels-related environmental impacts through the renewable and

more environmentally-friendly energy alternatives. Hydrotreated Vegetable Oil (HVO)

is seen as a modern paraffin based fuel promising to substitute petro-diesel. The

influences of physical/chemical properties of HVO to engine performance and

emissions formation have been investigated the feasibility through a sequence of

experiments before applying popularity on the market. This work concentrated on the

analysis of injection, spray, combustion and emission characteristics of HVO which are

considered as the most important featureson engine. These experiments were carried

out in the injection rate-Zeuch measurement system, constant volume combustion

chamber (CVCC), and rapid compression expansion machine (RCEM) respectively under

direct injection (DI) diesel engine conditions. The experimental fuels were the

commercial diesel fuel (B7), the neat HVO, the 10%, 20%, 30%, 50%, 80% HVO (by

mass fraction) blended with diesel fuel (B7). The results indicated that bulk modulus

of compressibility, injection delay, average injection rate, injection quantity were

inversely correlated to HVO fraction in blend. Adjusting injection duration was required

to obtain the injected fuel amount equally into combustion chamber. In addition, the

findings revealed the higher discharge coefficient with HVO as well as under higher

injection pressure. Regarding to spray evolution, slightly shorter in penetration length

during fully developed zone wasobserved with higher HVO fraction in blend.Thelarger

spray cone angle of HVO and its blends compared to diesel was caused by the

difference in viscosity, density, surface tension and the higher differential pressure.The

effectsof HVO’s fuel properties, variable oxygen concentrations and injection pressures

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were clearly revealed in results of combustion and emissions. The ignition delay, the

heat release rate, the flame temperature, the soot density-KL factor, the NOx and soot￾out emissions were decreased as increasing the HVO fraction in the blend. In addition,

the findings revealed the similar flame profiles in which the higher flame temperature

region and the darker KL density were concentrated around the spray flame upstream,

regardless of the HVO mixing ratio. Besides, the decrease in the O2 concentration

resulted in the lower heat release rate, integral heat release, flame temperature, KL

factor and NOx emissions but the longer ignition delay and higher soot concentration,

with the highest soot concentration observed under the 15% O2 environment.

Nevertheless, the higher pressure differential (i.e. between the injection pressure and

the ambient pressure) contributed to the shorter ignition delay, higher heat release

rate, early peak of the flame temperature, wider combustion area, faster soot oxidation

rate and higher NOx production.

Key words: Hydrotreated vegetable oil, DI-diesel combustion, NOx-soot emission,

Constant Volume Combustion Chamber, Zeuch-Injection Rate Method, Two Color

Method.