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DME as a fuel for compression ignition (diesel) engines has been actively studied for about ten years due to its characteristically low pollution and reputation as a “smokeless fuel”. During this time, the practical application is taking shape based on necessary tasks such as analysis of injection and combustion, engine performance, and development of experimental vehicles. At this moment, standardization of DME as a fuel was started under ISO in 2007. There are concerns regarding the impurities in DME regarding the mixing during production and distribution as well as their effect on additives for lubricity and odor. In this report, the effect of DME fuel impurities on performance of a DME powered diesel engine was investigated. The platform was a DME engine with common-rail fuel injection and was evaluated under partial load stable mode and Japanese transient mode (JE05) testing parameters.

The tasks to improve diesel emissions and fuel consumption must be accomplished with urgency. However, due to the trade-off relationship between NOx emissions, soot emissions and fuel consumption, clean diesel combustion should be achieved by both innovative combustion and fuel technologies. The objective of this study is to extend the clean diesel combustion operating range (Engine-out emission: NOx ≺ 0.2 g/kWh, Soot ≺ 0.02 g/kWh). In this study, performance of a single-cylinder test engine equipped with a hydraulic valve actuation system and an ultra-high pressure fuel injection system was investigated. Also evaluated, were the effects of fuel properties such as auto-ignitability, volatility and aromatic hydrocarbon components, on combustion performance. The results show that applying a high EGR (Exhaust gas recirculation) rate can significantly reduce NOx emission with an increase in soot emission.

It has been clarified that diesel fuel properties have a great effect on the exhaust emissions and fuel consumption of a conventional diesel combustion regime. And as other diesel combustion regimes are applied in order to improve exhaust emissions and fuel consumption, it can be supposed that the fuel properties also have significant effects. The purpose of this study is to propose the optimum diesel fuel properties for a premixed compression ignition (PCI) combustion regime. In this paper, the effect of the auto-ignitability of diesel fuels on exhaust emissions and fuel consumption was evaluated using a heavy-duty single-cylinder test engine. In all experiments, fuels were injected using an electronically controlled, common-rail diesel fuel injector, and most experiments were conducted under high EGR conditions in order to reduce NOx emissions.

The performance of a medium duty DME truck was evaluated by field tests and engine bench tests. The DME vehicle was given a public license plate on October 2004, after which running tests were continued on public roads and a test course. The DME vehicle could run the whole distance, about 500 km, without refueling. The average diesel equivalent fuel consumption of the fully loaded DME truck was 5.75 km/l, running at 80 km/h on public highways. Remedying several malfunctions that occurred in the power-train subsystems enhanced the vehicle performance and operation. The DME vehicle accumulated 13,000 km as of August, 2006 with no observed durability trouble of the fuel injection pump. Disassembly and inspection of the fuel injectors after 7,700 km operation revealed a few differences in the nozzle tip and the needle compared to diesel fuel operation. However, the injectors were used again after cleanup.

In this study, diesel exhaust emission characteristics were investigated as GTL (Gas To Liquid) fuel was applied to a heavy-duty diesel truck which had been developed to match a Japanese new long-term exhaust emission regulation (NOx < 2.0 g/kWh, PM < 0.027 g/kWh). The results in this study show that although the test vehicle has advanced technologies (e.g. high pressure fuel injection, oxidation catalyst, and urea-SCR aftertreatment system, etc.) which are applied to reduce diesel emissions, the neat GTL fuel has a great advantage to reduce particulate matter emissions and poly aromatic hydrocarbons. And regarding nano-size PM emissions, nuclei mode particles emitted during idling are significantly decreased by using the GTL fuel.

Biodiesel fuel has attracted much attention as a carbon neutral fuel because it is made from vegetable oil. Especially in Southeast Asia, there are numerous biofuel resources, such as palm oil and coconut oil, and it is desirable to utilize these for CO2 reduction. In this paper, we evaluate the properties of biodiesel fuel and biodiesel blended diesel oil. The low temperature performance of palm oil methyl ester (PME) is poor and it affects low temperature performance, even if the PME blending rate is low. The oxidation stability is a very important property of biodiesel fuel because degraded biodiesel fuel produces organic acids and polymeric substances. PME contains mainly saturated fatty acids methyl esters, so the oxidation stability is better than other fats and oils. When containing antioxidants such as beta carotene, biodiesel's oxidation stability is improved.

In this study, measurement methods of aldehydes and volatile organic compounds (VOCs) from off-road engine have been investigated. Also, their emission characteristics have been evaluated. By using high-performance liquid chromatograph (HPLC), aldehydes could be measured with small variation. Major aldehydes from off-road engine are formaldehyde and acetaldehyde. Total aldehydes emission is not necessarily low compared to THC emission. The emission characteristics of aldehydes are similar to that of CO, THC and PM. For VOCs sampling, sampling tube with absorbent was better than sampling bag because some kinds of VOCs tend to become absorbed on the sampling bag. Except for 1,3-butadiene, VOCs could be measured with small variation by using gas chromatography-mass spectrometer (GC-MS). Benzene, toluene and xylene were major species found in VOCs. The emission characteristics of VOCs were also similar to ones of CO, THC and PM.

The Agency of Natural Resources and Energy, Ministry of Economy, Trade and Industry has conducted conformity tests of diesel fuel containing Fatty Acid Methyl Ester (FAME) to amend diesel fuel standards in Japan. The objective of the tests is to examine appropriate specifications of diesel fuel containing FAME for automotive use for existing vehicles in the Japanese market. The conformity testing includes verification of fuel system component compatibility, tail pipe emissions, and characterization of the reliability and durability of the engine system, including the fuel injection system. In designing the conformity tests, the maximum FAME concentration was 5%. Most of the new standards are essentially equivalent to EN14214, but the total acid number (TAN) of specific acids, and oxidation stability of the new standards for diesel fuel containing FAME, are different from EN14214.

In this study, a MPT-HFRR (Multi-Pressure/Temperature High-Frequency Reciprocating Rig) was manufactured based on a diesel fuel lubricity test apparatus. The MPT-HFRR was designed to be used for conventional test methods as well as for liquefied gas fuel tests. Lubricity tests performed on a calibration standard sample under both atmospheric pressure and high pressure produced essentially constant values, so it was determined that this apparatus could be used for assessing the lubricity of fuel. Using this apparatus, the improvement of lubricity due to the addition of a DME (Dimethyl Ether) fuel additive was investigated. It was found that when 50ppm or more of a fatty acid lubricity improver was added, the wear scar diameter converged to 400μm or less, and a value close to the measured result for Diesel fuel was obtained. The lubricity obtained was considered to be generally satisfactory.

The engine performance and exhaust characteristics of the DME-powered diesel engine with an injection system developed for DME were investigated. The injection pump is an inline type that can inject double amount of DME fuel compared to the base injection pump because the calorific value of DME is about half lower than that of diesel fuel. The effect of injection timing on engine performances such as thermal efficiency, engine torque, and exhaust characteristics were investigated. Maximum torque and power with DME could be achieved the same or greater level compared to diesel fuel operation. Considering over all engine performances, the best dynamic injection timings without EGR were -3, -3, -6 and -9 deg. ATDC in 1120, 1680, 2240 and 2800 rpm engine speeds respectively in this experiment.

In this study, advantages of GTL fueled DI diesel engine were observed, then, some cautionary areas, notably the aptitude for sealing materials, were investigated. Some advantages of using GTL as a diesel engine fuel include reduction of soot emission levels, power output and fuel consumption with GTL to conventional diesel fuel operation is equivalent, super-low sulfur content of GTL and its liquid state at normal temperature and pressure. However, there are some problems with putting GTL fuel on the market, such as lubricity, aptitude for sealing materials, high cetane index and high pour point. It is necessary to use additives to improve GTL's lubricity, and selecting the most appropriate type of lubricity improver is also important. The influence of GTL on the swelling properties of standard rubber materials seem basically the same, but it is necessary to notice on used rubbers.

For better understanding of the combustion characteristics in a direct injection dimethyl ether (DME) engine, the chemiluminescences of a burner flame and in-cylinder flame were analyzed using the spectroscopic method. The emission intensities of chemiluminescences were measured by a photomultiplier after passing through a monochrome-spectrometer. For the burner flame, line spectra were found nearby the wave length of 310 nm, 430 nm and 515 nm, arising from OH, CH and C2 radicals, respectively. For the in-cylinder flame, a strong continuous spectrum was found from 340 nm wave length to 550 nm. Line spectra were also detected nearby 310 nm, 395 nm and 430 nm, arising from OH, HCHO, and C2 radicals, respectively, partially overlapping with the continuous spectrum. Of these line spectra, 310 nm of OH radical did not overlapped with the continuous spectrum.

In this research, a test apparatus (VPT-HFRR) for evaluating lubricity was manufactured at an arbitrary pressure according to the lubricity test method (HFRR) for diesel fuel. The lubricity of LPG blended fuel (LBF) for diesel engines was examined using VPT-HFRR., This was a value close to that of diesel fuel, and when a suitable lubricity had been maintained, it was checked. Prototype trucks were manufactured and their durability was examined. After a run of 70,000km or more, no serious trouble had occurred, and when LBF was maintained at a suitable lubricity, it was checked.

Since dimethyl ether (DME) is a synthetic fuel, it is possible to make it from natural gas, coal and biomass. It is a low-emission, oxygenated fuel, which does not generate soot in the exhaust. Therefore, it has recently been identified as a possible replacement for diesel fuel. In Japan, the new short-term emissions regulations will be enforced beginning in 2003, and the long-term emissions regulations are scheduled to be enforced in 2005. In order to meet these more stringent emissions regulations, existing diesel engines would not be as widely used in the near future as they currently are. This will thus bring about a more widespread use of DME engines due to their low emissions potential. Moreover, when the modification of existing diesel engines into DME engines is available at a moderate cost, the wider use of DME engines can be expected. This study targeted development and application of DME engine technology for diesel engine retrofit, in a used diesel vehicle.

To date, the DME combustion mechanism has been investigated by in-cylinder gas sampling, numerical calculations and observation of combustion radicals. It has been possible to quantify the emission intensities of in-cylinder combustion using a monochromator, and to observe the emitting species as images by using band-pass filters. However, the complete band images were not observed since the broadband (thermal) intensity may be stronger than band spectra intensities. Emission intensities of DME combustion radicals from a pre-mixed burner flame have been measured using a spectroscope and photomultiplier. Results were compared to other fuels, such as n-butane and methane, then, in this study, to better understand the combustion characteristics of DME, emission intensities near CH bands of an actual DI diesel engine fueled with DME were measured, and band spectra emitted from the engine were defined. Near TDC, emission intensities did not vary with wavelength.

In this study, spray images of LPG Blended Fuels (LBF) for DI diesel engines were observed using a constant volume chamber at high ambient temperature and pressure, and the spray characteristics of the fuel were investigated. The LBF spray started to vaporize at the injector tip and the outer downstream regions of the spray, like diesel fuel, because of the high temperature at these areas. There were more vaporized areas compared to diesel fuel. Sufficient fuel injection volume and volatility of LBF resulted in good fuel-air mixture, then, THC emissions decreased compared to diesel fuel at high load engine test conditions. Butane spray image could not be observed at the injector tip. It seems that the high temperature of the injector tip caused the butane spray to vaporize rapidly. Spray tip penetration with LBF and butane were equal or greater than with diesel fuel. The high volatility of LBF and butane had no noticeable effect on spray penetration.

In order to reduce environmental disruption due to exhaust PM and NOx emissions from diesel engines of dimethyl ether (DME) has been proposed the use for the next generation vehicles, because the discharge of the atmospheric pollutants is less. In this study, DME is used to fuel a retrofit type diesel engine, and operational tests were carried out using a rotary distributor fuel injection pump. In this experiment, comparison and examination of the effects of fuel injection pressure, nozzle hole diameter, and injection timing. When using DME as an alternative fuel, the fuel temperature affects engine operation. And diameter of the injector nozzle hole and larger injection quantity is regarded as factors affecting the improvement in engine performance. In addition, for understanding the DME spray in the cylinder, DME was sprayed in a constant volume chamber where atmospheric temperature and pressure increased simultaneously, and the result is compared and examined with diesel fuel.

In this study, the main properties of two types of gas-to-liquid (GTL) fuels were investigated. Then, performance and emission characteristics of a compression ignition engine fueled with GTLs were investigated by comparison with diesel fuel. GTL1 was composed of 100% paraffin by volume, and GTL2 was composed of 99.8% paraffin and 0.2% aromatics by volume. Most GTL fuel properties were comparable to those of diesel fuel, while both fuels have a higher cetane number and lower sulphur. A diesel engine could be operated with GTL fueling without any special engine modifications. Our tests showed that with the high cetane number of GTLs, the ignition delay was shorter, and combustion started earlier than with diesel fuel. With GTL1 operation, THC and soot emissions were lower than with diesel fuel operation, and even lower with GTL2 fueling.

In order to remove the diesel particulate matter (PM) and nitrogen oxides (NOx) from diesel exhaust, the gas is passed through a corona discharge collector for PM and another corona discharge device for NOx oxidation. With the PM collector, PM is accumulated on the central electrode, after that, it is removed by incineration technique. NOx concentration is decreased by oxidation to HNO3. In this study, these corona discharge reactors were coupled for removal of PM and NOx in progression, and attempted to remove these emissions in a slipstream of 14 liters/min of an experimental diesel engine and an actual vehicle, respectively. In case of the experimental test engine, it is found that nearly 100% and 15% of the PM and NOx emissions were removed even at a low input power of 26W (1560 J/L specific energy deposition). In the vehicle tests 1) a PM removal rate of 60% is obtained at an input power of over 40W, 2) a NOx removal rate of 97% is obtained at an input power of over 100W.

Alternative fuels such as butane and DME have different properties including high vapor pressure, low viscosity, and low surface tension, compared to other conventional fuels. These properties may lead to different atomization characteristics such as liquid core breakup, droplet size distribution, and evaporation process. To investigate these effects, a method based on shadowgraph technique to take spray images for droplets and surrounding gas was tested and evaluated. Experiments were performed at low injection pressure for early stage direct injection. It could be concluded from the results that the proposed method could be used to investigate the structure of evaporating spray, and the vapor layer around the spray core could be correlated to the turbulent mixing length for both of butane and DME sprays by observing vapor and spray core.