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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.

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 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.

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.

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.

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.

In this study, engine performances and exhaust emissions characteristics of compression ignition engine fueled with GTL were investigated by comparison with diesel fuel. Diesel engine could be operated fueled with GTL without any special modify for the test engine. With the high cetane number of GTL, the ignition lag was shorter, and the combustion started earlier than that of diesel fuel. Brake thermal efficiency operated with GTL increased at middle load conditions due to incomplete combustion emission such as CO and THC were lower than that of diesel fuel operation. NOx emission with GTL was comparable to diesel fuel, and there was a little decrease at high load. With GTL, soot emission was lower than with diesel fuel at above middle load condition. It seemed to be a reason of soot reduction that there was little sulphur contained in GTL.

Recently, dimethyl ether (DME) has been attracting much attention as a clean alternative fuel, since the thermal efficiency of DME powered diesel engine is comparable to diesel fuel operation and soot free combustion can be achieved. In this experiment, the effect of ambient pressure on DME spray was investigated with observation of droplet size such as Sauter mean diameter (SMD) by the shadowgraph and image processing method. The higher ambient pressure obstructs the growth of DME spray, therefore faster breakup was occurred, and liquid column was thicker with increasing the ambient pressure. Then engine performances and exhaust emissions characteristics of DME diesel engine were investigated with various compression ratios. The minimum compression ratio for the easy start and stable operation was obtained at compression ratio of about 12.

To better understand the combustion characteristics of DME, emission intensities of DME combustion radicals from a pre-mixed burner flame were measured by a spectroscope and photomultiplier, Results were compared to other fuels, such as methane and butane. Large peaks in the band spectra from pre-mixed and diffusion DME flames were found near 310 nm, 430 nm, and 515 nm, arising from OH, CH and C2, respectively. The DME emission intensities decreased with increasing the equivalence ratio in this study. Notably, the relative decrease in the C2 band spectra peak was greater than that of the OH band. Comparing the pre-mixed DME and butane flames, the butane band spectra peaks were similar in shape, but much stronger than those for DME. However, it was remarkable that CH and C2 band spectra peaks decreased only slightly with increase in equivalence ratio compared to the DME case.

This paper deals with the process regarding how dehydrogenation of soot particles takes place. The measured carbon/hydrogen ratios plotted against mean-diameter of soots fall on a straight line passing through the origin. It is shown that in the course of soot particle growth CM ratio increases linearly with the particle diameter: D. This is an indication of the fact that the number of carbon grows in proportion to D3, whereas that of hydrogen is proportional to D2. It is there by concluded that hydrogen sit only on surface of soot particles.

The authors tried to use LP gas, mainly butane, as the main fuel of diesel engines to reduce soot and to maintain high thermal efficiency. LP gas was injected in the direction of the intake valve directly as a spray to prevent knocking and to preserve high charging efficiency. The newly developed electronic fuel injection provided accurate fuel control and injection timing. As a result, the dual-fuel operation produced high thermal efficiency almost identical to that of diesel engines. Soot in engine exhaust was almost negligible. Three quarters of maximum output was obtained with butane, and only small amount of gas oil for idling, in spite of an high compression ratio of 17 for gas engines. Increasing the proportion of gas oil resulted in maximum output from a diesel engine and almost no soot output.

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.

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.

This paper presents the result of a theoretical study on the effects of particle size distribution on the soot particle measurement method. The principal equations are rear-ranged into a concise form, and a wide variation of size distribution functions are introduced to calculate the effects. It was found that the mean extinction coefficient is very weakly dependent on the shape of size distribution functions and can be approximated to that for the Sauter mean diameter with insignificant error. The volumetric density of soot particles can be obtained by light transmittance measurement on a single wavelength, and this is affected only by the estimated value for the Sauter mean diameter. The error due to the estimation is under 5%. On the other hand, it was found that the light transmittance measurement is insufficient to obtain size distribution or the Sauter mean diameter of soot particles.

Detailed chemical kinetic model of hydrogen peroxide (H2O2) into diesel exhaust gas has been executed to investigate its effect on the removal of nitric oxide(NO) by changing exhaust gas temperature and H2O2 addition amount. Flux analysis has also been done to clarify which reaction mainly affects NO-to-NO2 conversion. From the results of this study, it is shown that the optimal temperature condition to maximize the removal of NO exists near at 500K for OH addition condition, while that for H2O2 addition exists near at 800K. It is also shown that temperature window for the removal of NO becomes widened as the initial temperature of the exhaust gas increases, and NO-to-NO2 conversion rate decreases in proportion to the concentration of hydrocarbon(HC), although that of the total NOx remains the same level regardless of HC concentration. Finally, it is shown that HO2 + NO → NO2 + OH is mainly responsible for NO-to-NO2 conversion.

The oxidation mechanism of DTBP (Di-tertiary-butyl peroxide) and its role in butane oxidation have been investigated, as it pertains to the development of an LPG DI diesel engine. Ignition delay contours were analyzed to investigate the role of DTBP (ϕ≈0.2 to the total oxygen) in butane oxidation. At higher pressure and lower temperature regions, it was apparent that the addition of DTBP significantly enhances the ignition delay of butane, whereas at lower pressures and higher temperatures, this effect diminishes. Results of this study showed that the role of DTBP to enhance the ignition delay of the base fuel is through rapid heat release, rather than by radicals produced by decomposition during the base fuel ignition delay. Formaldehyde is a principal species involved in reactions for heat release in the higher pressure lower temperature region, comparable to diesel engine operating conditions.

Using an extended bottom view piston having a quartz window, flame propagation observation and flame contour analysis were carried out to investigate the combustion characteristics of a heavy-duty type LPG lean burn engine. The swirl ratio and piston cavity configuration were varied to investigate their effects on combustion and engine performance. Gradual reduction of NOx but increased hydrocarbon emissions were measured for leaner mixtures compared to the stoichiometric operation. High swirl apparently accelerated the initial flame kernel development, as evidenced by a shorter crank angle interval from the spark ignition to the maximum cylinder pressure. The ‘D’ type cavity, with an increased squish area located below the intake valve, was shown to have the shortest burn duration among the piston cavities tested. The experimental flame propagation observation procedure was shown to be useful for the study of the combustion process in engines.