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To control natural-gas HCCI combustion, internal exhaust gas recirculation (EGR) by exhaust valve reopening (EVRO) during the induction stroke was applied to a single-cylinder test engine. The results demonstrate that combustion phasing can be controlled successfully by adjusting the EGR ratio, and so improvement of thermal efficiency and reduction in unburned exhaust emissions are feasible. In addition, the results of the EVRO method were compared to those of intake-valve pilot opening (IVPO) during the exhaust stroke. It was shown that EVRO is more useful than IVPO as a heat-recovery method for HCCI combustion.

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.

To clarify the microcrystal structure of soot particulate in the combustion chamber, we examined sampling methods which freeze the reaction of sample specimens from the combustion chamber and collected the soot particulates on microgrids. We investigated the microcrystal structure with a high resolution transmission electron microscope. The results were: the particle size distribution and the microcrystal structure of the soot particulates is little different for the cooled freezing method and room temperature sampling. The typical layer plane structure which characterizes graphite carbon is not observed in the exhaust of diesel engines, but some particulates display a somewhat similar layer plane structure. The structure of soot particulate is a turbostratic structure as the electron diffraction patterns show polycrystals. The soot particulates in the combustion chamber is similar to exhaust soot particulates.

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 blending of dimethyl carbonate (DMC), which contains 53% of oxygen, in diesel fuel is very effective to suppress the formation of exhaust particulates, however, the mechanism of the suppression has not been made clear. In this study, the comparison on the performance of gas oil and DMC mixture was achieved. The effect of the oxygen in DMC molecule has to suppress the formation of particulates was monitored by way of using thermal cracking analyzer under various conditions.

Since there is a trade-off relationship between NOx and particulates in exhaust gas emitted from a diesel engine, simultaneous reduction of the amounts of NOx and particulates in a combustion chamber is difficult. However, the amount of particulates produced in the combustion process could be reduced in a state of almost complete combustion, and the amount of NOx produced during the combustion process could be reduced by the use of a catalyst and reducing agent in the exhaust process. It has been demonstrated that the use of ethanol as a reducing agent on a silver-base catalyst in the presence of oxygen is an effective means for reducing NOx, although the mechanism of the reduction has not been elucidated. Therefore, in the present study, an NOx-reduction apparatus was conducted, and model experiments on NOx reduction were carried out in an atmosphere simulating exhaust gas emitted from a diesel engine and at the same catalyst temperature as that in a combustion chamber.

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 paper presents results of experiments to reduce smoke emitted from direct Injection diesel engines by strong turbulence generated during the combustion process. The turbulence was created by jets of burned gas from an auxiliary chamber installed in the cylinder head. Strong turbulence, which was induced late in the combustion period, enhanced the mixing of air with unburned fuel and soot, resulting in a remarkable reduction of smoke and particulate; NOx did not show any increase with this system, and thermal efficiency was improved at high loads. The paper also shows that the combination of EGR and water injection with this system effectively reduces the both smoke and NOx.

Copper ion-exchanged ZSM-5 zeolite catalyst, which reduces nitrogen oxides (NOx) in the presence of oxygen and hydrocarbons, was applied to actual diesel engine exhaust. Copper ion-exchanged ZSM-5 zeolite effectively reduced NOx by 25% in normal engine operation, and by 80% when hydrocarbons in the exhaust were increased. Water in the exhaust gas decreased the NOx reduction efficiency, but oxygen and sulfur appeared to have only a small effect. Maximum NOx reduction was observed at 400°C irrespective of hydrocarbon species, and did not decrease with space velocity up to values of 20,000 1/h. THE PURPOSE of this paper is to evaluate the possibilities and problems in catalytic reduction of NOx in actual diesel engine exhaust. Here, a copper ion-exchanged ZSM-5 zeolite (Cu-Z) catalyst was applied to diesel engine exhaust to examine the dependency of the NOx reduction efficiency on temperature and space velocity. The effects of oxygen, water and hydrocarbons were also examined.

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.

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.

This study focuses on deposit formation in a diesel engine fueled with straight vegetable oil (SVO) and its effects on engine performance and exhaust emissions. First, two-dimensional thickness distributions of the carbon deposits on the cylinder head were measured by a laser displacement meter after continuous engine operation on gas oil blended with SVO at 25%. The obtained results show that the carbon deposit thickness rapidly increases with SVO-blended fuel and reaches a higher level than with just gas oil. Second, the effects of fuel injector deposits on engine performance and emissions were examined. A small diesel engine was continuously operated by alternating between SVO and gas oil. Gas oil was injected for 1 hour before and after 6 hours of SVO operation to prevent the accumulation of SVO deposits inside the nozzle holes, and the process was repeated.

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 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.

Exhaust Particulate emitted from diesel engines is a serious problem form the point of view of the environment and energy saving. Exhaust particulate is consist of dry soot and SOF (soluble organic fraction). To clarify the formation process of SOF in the combustion chamber of diesel engines, first lower temperature column condensed method was investigated. The gas from combustion chamber was collected to the sampling column using this method, and the cracked as well as the condensation polymerized components were analyzed with gas chromatography. The sampling condition of the low temperature column condensation method are length of condensation column 600mm, cooling temperature 198K, and dilution ratio 5. The diesel fuel injected into the combustion chamber, first cracks into lower boiling point hydrocarbons, this is followed by dehydrogenation and formation of benzene ring compounds through condensation polymerization. This is followed by the formation of PAH.