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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.

Hydrogen can be produced by electrolyzation with renewable electricity and the combustion products of hydrogen mixture include no CO, CO2 and hydrocarbons. In this study, engine performance with hydrogen / diesel dual fuel (hydrogen DDF) operation in a multi-cylinder diesel engine is investigated due to clarify advantages and disadvantages of hydrogen DDF operation. Hydrogen DDF operation under several brake power conditions are evaluated by changing a rate of hydrogen to total input energy (H2 rate). As H2 rate is increased, an amount of diesel fuel is decreased to keep a given torque constant. When the hydrogen DDF engine is operated with EGR, Exhaust gas components including carbon are improved or suppressed to same level as conventional diesel combustion. In addition, brake thermal efficiency is improved to 40% by increase in H2 rate that advances combustion phasing under higher power condition. On the other hand, NOx emission is much higher than one of conventional diesel engine.

Hydrogen can be produced by electrolyzation with renewable electricity and reduce the combustion products from hydrogen mixture don't include CO, CO2 and unburned hydrocarbon components. We focused on these characteristics of hydrogen and high thermal efficiency of diesel engine and acquired the performance of hydrogen diesel dual fuel (DDF) engine. We changed proportion of hydrogen to total input energy and studied basic combustion and exhaust gas emission performance of hydrogen DDF operation. In addition, we studied the effects of advancement of diesel fuel injection timing and EGR on combustion behavior and improvement of NOx emission. Especially, EGR improved NOx emission from hydrogen DDF operation drastically without a decrease in thermal efficiency. Under hydrogen DDF operation with EGR, diesel fuel injection timing was advanced for stable combustion and it inhibited the degradation of thermal efficiency.

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.

Isopentanol is an advanced biofuel that can be produced by micro-organisms through genetically engineered metabolic pathways. Compared to the more frequently studied ethanol, isopentanol's molecular structure has a longer carbon chain and includes a methyl branch. Its volumetric energy density is over 30% higher than ethanol, and it is less hygroscopic. Some fundamental combustion properties of isopentanol in an HCCI engine have been characterized in a recent study by Yang and Dec (SAE 2010-01-2164). They found that for typical HCCI operating conditions, isopentanol lacks two-stage ignition properties, yet it has a higher HCCI reactivity than gasoline. The amount of intermediate temperature heat release (ITHR) is an important fuel property, and having sufficient ITHR is critical for HCCI operation without knock at high loads using intake-pressure boosting. Isopentanol shows considerable ITHR, and the amount of ITHR increases with boost, similar to gasoline.

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.

It is thought that the synthetic gas, including hydrogen and carbon monoxide, has a potential to be an alternative fuel for internal combustion engines, because a heating value of the synthetic gas is higher than one of hydrogen or natural gas. A purpose of this study is to acquire stable auto-ignition and combustion of the synthetic gas which is supposed to be applied into a direct-injection compression ignition engine. In this study, the effects of ambient gas temperatures and oxygen concentrations on auto-ignition characteristics of the synthetic gas with changing percentage of hydrogen (H2) or carbon monoxide (CO) concentrations in the synthetic gas. An electronically-controlled, hydraulically-actuated gas injector was used to control a precise injection timing and period of gaseous fuels, and the experiments were conducted in an optically accessible, constant-volume combustion chamber under simulated quiescent diesel engine conditions.

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.

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.

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.

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.