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The boiling point curve of fatty acid methyl esters (FAME), or biodiesel fuel, can be adapted to that of diesel fuel by breaking FAME down into a low-molecular structure using a cross-metathesis reaction with a short-chain olefin. Reformulated FAME by a metathesis reaction consists mainly of medium-chain olefins and fatty acid methyl esters. In the present study, the engine performance and exhaust emissions from reformulated FAME were investigated through engine bench tests. Surrogate fuels made from typical chemical components of reformulated FAME were used to clarify the effects of respective components upon combustion. Surrogate fuels were made by mixing 1-decene, 1-tetradecene, methyl laurate, methyl palmitate, and methyl oleate to simulate the boiling point, oxygen mass concentration, and calorific value of reformed biodiesel of waste cooking oil methyl ester (WME). A single-cylinder diesel engine equipped with common-rail-type injection system was used.

Biodiesel fuel can be used in diesel engines with no major modification, but there are some issues derived from the properties of the fuel. Engine oil dilution is a major issue caused by lower volatility and low oxidation stability in biodiesel fuel. The purpose of this study was to clarify the influence of oil dilution by biodiesel fuel on oxidative degradation characteristics, including the acid value (AV), carbon residue (CR), and kinematic viscosity of diesel engine lubricant oil. Degradation assessment was carried out on lubricant oil during operation of a small diesel engine generator, as well as an oxidative acceleration test using a mixture of biodiesel and lubricant oil. It was found that the kinematic viscosity decreased to 23% from its initial value, the dilution rate increased almost linearly, amounting to 2.8 mass-% after 102 hours of engine operation, and deterioration was greater in JASO DH-1 grade lubricant oil mixed with biodiesel than in JASO DH-2.

“Drop-in” biofuels have a high potential as an alternative to petro-fuels. Because drop-in biofuels are hydrocarbon fuel, there are no issues related to poor oxidation stability such as in FAME. Diesel fuel which is named “SoladieselRD” is liquid bio-hydrocarbon and is the hydro-treated oil of micro-algal triglyceride. In this study, the engine performance and exhaust emission characteristics using SoladieselRD were investigated and compared with those using petro-diesel fuel (gas oil). A test was conducted using a single-cylinder, water-cooled, direct-injection diesel engine with a common-rail type high-pressure injection system. From the experimental results, it was clear that the ignition delay of SoladieselRD is shorter than that of petro-diesel, and the trade-off relationship between PM and NOx emissions by SoladieselRD was better than that of gas oil.

The main aim of this study is to investigate the effect of NO and NO2 on the combustion characteristics such as pressure development and combustion phasing in natural gas HCCI engine. A secondary aim is to demonstrate a method of obtaining a significant sensitizing effect on methane oxidation reaction from small amounts of NOx. Experiments were conducted using a rapid compression-expansion machine that was constructed from a single-cylinder diesel engine. First, the sensitizing effect of NO and NO2 on the HCCI combustion of natural gas was investigated in a case where NOx was uniformly mixed into a charge. Obtained results show that the auto-ignition timing is significantly advanced and an acute heat release is promoted by adding either NO or NO2.

The objective of this study was to obtain an improved understanding of the effects of the simultaneous use of cold flow improver (CFI) and antioxidant on the cold flow properties, oxidation stability and diesel exhaust emissions of various biodiesels and biodiesel blends. Cold flow properties were evaluated by assessing the cloud point (CP) and pour point (PP) values, as well as from the results of the cold soak filtration test (CSFT). Oxidation stability was also determined by measuring the peroxide induction period (IP). The neat biodiesels (B100) derived from soybean oil(SME), Jatropha curcus oil(JME), rice bran oil(RBME), palm oil(PME) and waste cooking oil(WME), and biodiesel blends with JIS No.2 diesel fuel were tested. A CFI and antioxidant specially designed for use in biodiesel fuels were employed during the work. The experimental data demonstrated that the addition of antioxidant had no effect on either the CP or PP values.

High energy demand and environmental pollution leads to seeking of new, renewable and clean energy as biofuel and biomass. These fuels are abundant in tropical areas and agricultural-economic-based countries. Among various crops which are used for biofuel, Jatropha Curcas L. Oil (JO) is more beneficial and attractive as it is non-edible which is not competitive with food demand. In agricultural sector, the biomass waste especially from rice production such as rice husk is a tremendous resource in Cambodia. The combination of the use of biomass from rice husk (RH) and Jatropha Cake (JC) from the JO production in the gasification can produce more energy for the electricity production especially in the remote and rural area. In previous research, some researchers have been investigated on the use of JO in blending ratio, heated-neat condition and dual fuel combustion of diesel and bio-digested biogas.

The suitability of caprylic (C8:0), lauric (C12:0), and palmitic (C16:0) acid 2-ethylhexyls derived from palm/coconut oil in diesel engine was evaluated. The pour point of each compound was approximately 40°C lower than that of the corresponding methyl ester due to the ethyl branch in the alcohol. All compounds possessed high oxidation stability, high lubricity, and a high cetane number. Engine bench test results demonstrated that 2-ethylhexyl laurate and palmitate result in shorter ignition delays compared to gas oil. The short ignition delays suppressed initial premix-like combustion. As a result, high brake thermal efficiency with low combustion noise was achieved. Furthermore, both laurate and palmitate produced less NOx emissions and less unburned gaseous emissions.

In this study, it was attempted to operate the 4-cycle multi cylinder natural gas engine introduced PCCI combustion system without electric heater for intake air heating. In experiment, by optimization of the compression ratio and in addition to the control of spark ignition timing, the engine could be operated using only intake air heating with coolant water. The results showed that the suppression of the auto-ignition timing variations among cylinders owing to the independent spark timing control of each cylinder leads to the improvement of engine output, fuel economy and exhaust emissions. Furthermore, this paper describes the engine starting and corresponding change of engine load on electric demand on generator. The stable operation could be achieved by using spark ignition, controlling of excess air ratio and intake air temperature during change the engine load from idle to rated power.

In this study, the influence of compression ratio on engine performance and variations of auto-ignition timing in each cylinder were evaluated in a 4-cycle multi-cylinder natural gas engine with PCCI combustion system. In experiment, the compression ratio was systematically changed from 19 to 25. From the result, it was clarified that an increase in compression ratio makes not only the improvement of engine output and fuel economy but also the reduction of NOx emission, even though the mechanical loss is increased. Simultaneously, the variation of auto-ignition timing in each cylinder can also be reduced.

A novel EGR (exhaust gas recirculation) method by means of the intake-valve pilot-opening has been demonstrated using a single-cylinder test engine, in order to control the combustion and to reduce the energy loss due to intake-gas pre-heating in a natural gas HCCI (homogeneous charge compression ignition) engine. The intake valve, together with the exhaust valve, is slightly opened at the beginning of the exhaust stroke. Then, part of the burnt gas, which has a high temperature, is introduced into the suction pipe backward, resulting in an increase in the intake-gas temperature. The EGR rate can be varied successfully up to about 40% by using the specially designed camshaft and the valve control device, which can delay the closing timing. The effect of the EGR rate on engine performance and emissions has been investigated under the condition that the temperature of the fresh mixture and the fuel consumption rate are kept constant.

To characterize the suitable conditions for a natural gas PCCI (premixed charge compression ignition) engine to provide both high efficiency and low emissions, an experimental study was demonstrated using a small-scale, single-cylinder engine. Engine tests were systematically carried out with various parameters, including compression ratio (18 to 22), intake-air temperature (160 to 220 °C) and engine speed (800 to 2400 rpm). It was shown that the maximum specific power can be improved in proportion to an engine speed up to 2400 rpm, while both the indicated thermal efficiency over 32% and the NOx emission below 100 ppm can be retained. However, an increase in engine speed extends the combustion duration especially under lean conditions, which decreases the indicated thermal efficiency.