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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.

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.

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.

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.

The experimental study has been carried out on a diesel engine dual-fueled by wood-pyrolysis gas and biodiesel fuel. Wood-pyrolysis gas was simulated by a low-calorie mixed gas (LCG), which consists of hydrogen, methane and inert gas. Effects of LCG/biodiesel ratio, biodiesel injection-timing, and gas-fuel composition were examined. Obtained results show that under a constant-torque condition, an increase in gas fuel consumption causes a decrease in a brake thermal efficiency due to a decrease in combustion efficiency and specific heat ratio. Also, NOx emission in exhaust gas is decreased by increase in gas fuel consumption under the low load condition, while it shows no change under the relatively high load condition. In addition, an early injection of biodiesel is effective to reduce carbon monoxide emission due to increase in combustion pressure and temperature.

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.

The performance of Diesel Particulate Filter(DPF) using biodiesel fuel was evaluated in a vehicle road test and in a diesel engine bench rig. The DPF used for the tests was made of SiC honeycomb which had a soot filtering efficiency close to 100%. The DPF/diesel engine system used was not configured for continuous regeneration. Regeneration was completed by batch heating with electric power. From the result of vehicle road test, the distance between regeneration for the vehicle fueled with biodiesel fuel was longer than that fueled with petro-diesel fuel. This gain in distance was greater than what was expected from the soot reduction because of the biodiesel fuel characteristics. This observation was further investigated in diesel engine bench rig with the DPF using several biodiesel fuels with different degree of purity.

This paper describes two topics. One is a study of the effects of refining process of biodiesel fuel on fuel properties, diesel engine performance and exhaust emissions. The second topic is a study to clarify the influences of plant oil sources for biodiesel production on combustion and emission characteristics. Plant oils or used cooking oils are reacted with methanol and a lye catalyst: KOH, to produce fatty acid methyl ester: unwashed-biodiesel. Washing the unwashed-biodiesel by water and dying processes are necessary in order to improve its fuel properties. Experiments were carried out on a single-cylinder, 4-stroke-cycle, DI diesel engine and various unwashed-, washed- and refined-biodiesel fuels derived from new or used cooking oil. From the result, it was found that the unwashed-biodiesel occurred unstable engine operation. And there was few difference in engine performance and emissions between biodiesel fuel from new and used cooking oil at same plant oil source.

This study derives regression equations for predicting the cetane number of biodiesel fuels based on chemical analysis data. For conducting the regression analysis, 34 fuel samples with a wide variety of ignition qualities were made by mixing five kinds of biodiesels and five kinds of fatty acid methyl ester (FAME) reagents. The relationship between the cetane number, measured in a constant-volume combustion chamber, and fuel properties such as iodine value, saponification number, and boiling point, was investigated. Based on the results, four regression equations were proposed and their accuracies were compared. The results show that the regression equation based on fuel composition gives a cetane number with high accuracy, whereas it can be only be approximately predicted from the iodine value.

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.

In our first study[1], we reported that the self-regeneration of DPF is enabled by the function of residual potassium methoxide (CH3OK) as catalyst, contained in biodiesel fuel that is collected in the DPF at lower engine loads[1]. In the present report, exhaust emission characteristics after using DPF were investigated by continuous measurement of exhaust gas. The results show that the self-regeneration of DPF occurs when engine loads change from lower to higher, and at the same time, methanol concentration in exhaust gas reaches to a higher peak. This peak is higher than when self-regeneration does not take place. The higher concentration of methanol is reduced by repeating the self-regeneration. The SOF content in PM is reduced by DPF at both high and low engine load, which is a characteristic that was not seen with gas oil.

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.

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.

Biodiesel fuel (Fatty acid methyl esters: FAME) have lower volatility than petro-diesel fuel due to the larger molecular size of FAME. Recent studies report that the distillation temperature of biodiesel fuel can be lowered by the cross-metathesis reaction with short-chain olefin using ruthenium catalyst. In this study, the effect of cross-metathesis reaction conditions on the distillation characteristics of reformulated biodiesel fuel is investigated to reveal the reaction conditions for fitting the distillation curve of biodiesel fuels to that of petro-diesel fuel. Furthermore, the reactivity of typical biodiesel fuels such as RME (rapeseed oil), SME (soybean oil), and WME (waste cooking oil) for cross-metathesis reaction were examined to reveal the reaction conditions appropriate for their fatty-acid compositions.

Oxy-fuel combustion (OFC), in which fuel is burnt with pure oxygen, is a promising method by which to establish a CO2 recovery system from engine exhaust. The ideal exhaust gas for OFC consists of only CO2 and H2O at a stoichiometric mixture ratio, which can be easily separated by cooling the exhaust. In OFC, exhaust gas recirculation (EGR) is applied in order to avoid an extreme increase of the combustion temperature by increasing the heat capacity. In the present study, in order to improve the OFC of a natural-gas spark-ignited engine, the effect of the operating conditions on the combustion characteristics was investigated using a rapid compression and expansion machine. The effects of the compression ratio, ignition timing, and CO2 concentration in the mixture were examined while keeping the fuel-oxygen mixture at the stoichiometric ratio.