Search Results

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.

Flame propagation at elevated pressures for propane, butane and autogas (20% propane and 80% butane by mass) were investigated. Flame arrival time was measured using ionization probes installed along the wall of a cylindrical combustion chamber. Flame radius was also measured using a laser schlieren technique. Results showed that the flame front speed decreased with increasing initial pressure, and the initial pressure effect on maximum flame front speed was correlated by the relationship Sf = 175·pi-0.15 (for Φ=1.0). Characteristics of flame front speed between propane, butane and autogas were very similar, whereas at fuel-rich conditions flame front speed of butane and autogas were higher than that of propane. A thermodynamic model to predict flame radius and speed as a function of time was derived and tested using measured pressure-time curves.

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.

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.

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.

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.

Remarkable progress has been made in recent years on pressure measuring techniques and apparatuses, yet they seem not necessarily successful in achieving accurate pressure diagrams at the high frequency range. The primary cause of difficulty lies in the occurrence of undesirable vibrations in the connecting passages which diminishes the accuracy of pressure diagrams. In order to prevent such vibration, the authors have attempted to increase the natural frequency in the connecting passages by enclosing heat resisting silicon oil, to analyse the frequency characteristics of the passages, and to ensure the propriety of the analysis through comparison with experiments. As a result, it is proved that the natural frequency of the silicon oil enclosed passage increases twice as high as that of the passage filled with working gas.

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.