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Exhaust gas recirculation (EGR) is widely used in diesel engines to reduce nitrogen oxide (NOx) emissions. However, a lacquer is formed on the EGR valve or EGR cooler due to particulate matter and other components present in diesel exhaust, causing serious problems. In this study, the mechanism of lacquer deposition is investigated using attenuated total reflection Fourier transform infrared spectrometry (ATR-FTIR) and scanning electron microscopy (SEM). Deposition of temperature-dependent lacquers was evaluated by varying the temperature of a diamond prism between 80 and 120 °C in an ATR-FTIR spectrometer integrated into a custom-built sample line, which branched off from the exhaust pipe of a diesel engine. Lacquers were deposited on the diamond prism at 100 °C or less, while no lacquer was deposited at 120 °C. Time-dependent ATR-FTIR spectra were obtained for approximately 2 h from the beginning of the experiment.

Improvement of thermal efficiency is an important problem for internal combustion engines. Fuel reforming with dehydrogenation reaction by exhaust heat is one of the measures to increase thermal efficiency using hydrogen mixed SI combustion. For this kind engine system, hydrous ethanol has a good potential. Furthermore, when the hydrous ethanol inject to combustion chamber directory, high compression combustion can be achieved by its large amount of latent heat. Therefore, fuel lubricity is an important check point for the hydrous ethanol reforming engine systems. In this study, effect of water concentrations within ethanol on the hydrous ethanol fuel lubricity has been evaluated using HFRR (High-Frequency Reciprocating Rig) test method. Wear scar diameter on 100 % of ethanol was around 700 μm which was a little better than gasoline lubricity. When the water concentration within ethanol was increased, the wear scar diameters were decreasing around 330 μm.

Dimethyl ether (DME) is an oxygenated fuel with the molecular formula CH₃OCH₃, economically produced from various energy sources, such as natural gas, coal and biomass. It has gained prominence as a substitute for diesel fuel in Japan and in other Asian countries, from the viewpoint of both energy diversification and environmental protection. The greatest advantage of DME is that it emits practically no particulate matter when used in compression ignition (CI) engine. However, one of the drawbacks of DME CI engine is the increase carbon monoxide (CO) emission in high-load and high exhaust gas circulation (EGR) regime. In this study, we have investigated the CO formation characteristics of DME CI combustion based on chemical kinetics.

The methodology of lubricity evaluation for DME fuel was established by special modified HFRR (High-Frequency Reciprocating Rig) such as Multi-Pressure/Temperature HFRR (MPT-HFRR). The obtained results were summarized as follows: The HFRR method is adaptable with DME fuel. There is no effect of the test pressure (up to 1.8 MPa) and the test temperature (up to 100°C) of MPT-HFRR on wear scar diameter. The results with MPT-HFRR can be applied at the sliding parts of the injection needle and the fuel supply pump's plungers which are secured lubricity by the boundary lubrication mode mainly and the mixed lubrication mode partially. Using the fatty-acid-based lubricity improver in amounts of approximately 100 ppm, the lubricity of DME, which has a lack of self-lubricity, is ensured as same as the diesel fuel equivalent level. There is a big deviation of measured wear scar diameter when the LI concentration is not enough.

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.

Hydrogen produced from regenerative sources has the potential to be a sustainable substitute for fossil fuels. A hydrogen internal combustion engine has good combustion characteristics, such as higher flame propagation velocity, shorter quenching distance, and higher thermal conductivity compared with hydrocarbon fuel. However, storing hydrogen is problematic since the energy density is low. Hydrogen can be chemically stored as a hydrocarbon fuel. In particular, an organic hydride can easily generate hydrogen through use of a catalyst. Additionally, it has an advantage in hydrogen transportation due to its liquid form at room temperature and pressure. We examined the application of an organic hydride in a spark ignition (SI) engine. We used methylcyclohexane (MCH) as an organic hydride from which hydrogen and toluene (TOL) can be reformed. First, the theoretical thermal efficiency was examined when hydrogen and TOL were supplied to an SI engine.

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.

Dimethyl ether (DME) has been attracting notable attention as a clean alternative fuel for diesel engines. The authors developed a medium duty DME truck, and investigated aspects of vehicle performance such as engine power, exhaust characteristics, fuel consumption, noise, in-vehicle systems, and so on. Results indicated that higher engine torque and power could be achieved with DME compared to diesel fuel operation of the base engine at any engine speed. Results also showed that emissions decreased dramatically, to 27% for NOx, 74% for HC, 95% for CO and 94% for PM (Particulate Matter) compared to maximum allowed Japanese 2003 emission regulations. The operating noise of the DME vehicle was slightly lower than the base vehicle with diesel fuel, because the combustion noise with DME was decreased compared to with diesel fuel operation. The DME vehicle was given a public license plate in October 2004, after which running test continued on public roads and on a test course.

In this report, trace levels of harmful substances, such as formaldehyde, acetaldehyde, SO2, benzene and so on, emitted from a DME fueled direct injection (DI) compression ignition (CI) engine were measured using a Fourier Transform Infrared (FTIR) emission analyzer. Results showed that the NO portion of NOx emissions with DME exceeded diesel fuel operation levels. DME fueling caused greater amounts of water than with diesel fuel operation. DME fueling was also associated with higher formaldehyde emissions than with diesel fuel operation. However, using an oxidation catalyst, formaldehyde could be decreased to a negligible level.

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.

Dimethyl ether (DME) holds promise as an alternative to diesel fuel. However, its physical properties are not similar to those of conventional diesel fuel. The P-V, bulk modulus and viscosity of DME are derived as a function of temperature and pressure. As a result, the Weber and Reynolds number of DME is very large as compared with that of diesel fuel. So, the spray characteristics of DME are not those of a liquid spray but similar to those of gas spray. The spray formation is strongly affected by the fuel flow in the nozzle. The Computational Fluid Dynamics (CFD) and experiments are examined to analyze the fuel flow in the nozzle. The DME physical properties make some difference to the flow in the nozzle, in comparison with those of diesel. As a CFD result, cavitation in the injection nozzle is more frequent with DME than with diesel oil. From experimental results, the temperature in the nozzle sac is higher with DME than with diesel oil.

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.

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.

Dimethyl ether(DME) is a promising new alternative fuel not only diesel fuel but also power generation, fuel cell and city gas. However, the physical properties are not similar to those of conventional diesel fuel. The P-v, bulk modulus and viscosity of DME are derived as a function of temperature and pressure. As a Result, the Weber and Reynolds number of DME is very large as compared with that of diesel fuel. So, the spray characteristics of DME is not the liquid spray but similar to that of gas spray. The spray formation is strongly affected by the fuel flow in the nozzle. The Computational Fluid Dynamics (CFD) and the experiments are examined to analyze the fuel flow in the nozzle. The DME physical properties make some difference of the flow in the nozzle, comparing with those of diesel. As a CFD result, cavitation in the injection nozzle is more frequent with DME than with diesel oil.

Characteristics of dimethyl ether spray formation were observed using schlieren photography, and the combustion characteristics and performance of a dimethyl ether-operated diesel engine were investigated. Accordingly, this paper describes the basic characteristics of engine performance and the potential for decreased exhaust emissions, as well as discussing problems concerning the practical application of dimethyl ether-operated diesel engines.

Experiments were conducted to operate a direct injection (DI) diesel engine by using Liquefied Petroleum Gas (LPG) as a main fuel. Aliphatic Hydrocarbon (AH), cetane enhancing additive and lubricating additive were also added to the LPG so that smooth operation was achieved with a wide range of engine loads. Since the lubricity of LPG is lower than the diesel fuel therefore lubricating additive was employed to enhance the lubricity of LPG blended fuel. Furthermore, prototype LPG diesel truck was developed in this work, and the mileage reached about 70,000 km without any major failure. Prototype truck has good starting, good drive-off, acceleration and braking characteristics.

In this study, lubricity improvers were added to three different GTL fuels, which were then quantified with a High Frequency Reciprocating Rig (HFRR) and compared with ultra low sulphur diesel fuel (ULS). Furthermore, the lubricity of mixtures of a GTL blended with ULS was also investigated. Two kinds of compounds were tested as lubricity improvers: unsaturated fatty acids (UFA-type) and partial UFA esters of glycerin (Ester-type). All GTL fuels showed less sensitivity to a lubricity additive than ULS did, but the ULS mixture had better than expected lubricity. Thus it was concluded that blending of GTLs with ULS can be regarded as one practical measure to sufficiently improve lubricity. HFRR tests performed under the same viscosity suggested that fuel composition had an important effect on its sensitivity to an additive, as well as viscosity.