Search Results

Dimethyl Ether (DME) is one of the major candidates for the next generation fuel for compression ignition (CI) engines. It has good self-ignitability and would not produce particulate, even at rich conditions. DME has proved to be able to apply to ordinary diesel engines with minimal modifications, but its combustion characteristics are not completely understood. In this study, the behavior of a DME spray and combustion process of a direct injection CI engine fueled with DME was investigated by combustion observation and in-cylinder gas sampling. To distinguish evaporated and non-evaporated zones of a spray, direct and schlieren imaging were carried out. The sampled gas from a DME spray was analyzed by gas chromatography, and the major intermediate product histories during ignition period were analyzed.

This research investigated the performance and emissions of a direct injection (DI) Diesel engine operated on 100% butane liquid petroleum gas (LPG). The LPG has a low cetane number, therefore di-tertiary-butyl peroxide (DTBP) and aliphatic hydrocarbon (AHC) were added to the LPG (100% butane) to enhance cetane number. With the cetane improver, stable Diesel engine operation over a wide range of the engine loads was possible. By changing the concentration of DTBP and AHC several different LPG blended fuels were obtained. In-cylinder visualization was also used in this research to check the combustion behavior. LPG and only AHC blended fuel showed NOX emission increased compared to Diesel fuel operation. Experimental result showed that the thermal efficiency of LPG powered Diesel engine was comparable to Diesel fuel operation. Exhaust emissions measurements showed that NOX and smoke could be considerably reduced with the blend of LPG, DTBP and AHC.

Based on the knowledge that cavitation in a nozzle enhances the atomization of fuel spray, fuel modification is conducted by blending Dimethyl Ether (DME). Because the boiling point of DME is -24.8°C, it may easily take place during the cavitation in an injection nozzle. Furthermore, there is a soot reduction effect caused by the oxygenated fuels. The oxygen content in the DME is 34.8%, which accelerates soot reduction in the combustion chamber. The experimental results are compared with those of DiMethoxyMethan (Methylal: DMM), a blend of gas-oil. The ignition temperatures of DME and DMM are 235°C and 236°C, the boiling temperatures of DME and DMM are -24.8°C and 42.1°C, and the oxygen contents of DME and DMM are 34.8% and 42.1%, respectively. In addition to the oxygenated fuel, a propane blend of gas-oil was also used as a blended fuel in order to examine the effects of the boiling point and oxygen content of the fuel.

In this study, a homogeneous mixture of natural-gas and air was used in a compression ignition engine to reduce NOx emissions and improve thermal efficiency. In order to control ignition timing and combustion, a small amount of DME was mixed with the natural-gas. Engine performance and the exhaust characteristics were investigated experimentally. Results show the following: the engine can run over quite a large load range if a certain amount of DME is added into natural-gas. By optimizing the proportion of DME to natural-gas, NOx emissions can be lowered to near zero levels if the mixture is lean enough. Thermal efficiency is higher than that obtained with normal diesel fuel operation.

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.