Table 1 Properties of DME and other fuel.

Properties	DME	Diesel	Ultra lowsulfur diesel	Biodiesel (Palm Methyl ester)
Specific gravity	0.668	0.832	0.837	0.842
Flash point(^oF)	Flammable gas(Autoignition, 350^oC)	63.5	147	112
Viscosity at 40 ^oC (cSt)	0.225	2.482	2.5	5.150
Pour point(^oF)	unknown(b.p. at -23.6^oC)	-16.6	-0.4	12.0
Sulfur content(ppm)	0	350	13	31
Cetane number	55-60	46.8	49.7	62
Chemicalcompositions	C₂H₆O	C₁₀-C₂₀	C₁₀-C₂₀	Methyl ester mixture

Recently, the world has been faced with an energy crisis and environmental problem. The increment of crude oil price and the shrinkage of reservoir which are main problems due to the large fuel oil demand in the Asia Pacific region has led to the development of alternative fuel such as Fischer-Tropsch oil, biodiesel, methanol, an dimethyl ether. Dimethyl ether (DME), one of the promising alternative fuels produced in a large quantity through natural gas, coal, and biomass is known as a non-Freon propellant and coolant. It can also be used as an LPG substitute since to it is easily liquefied and its properties are comparable to propane and butane. DME is also considered as an alternative clean diesel fuel due to its high cetane number (>55) and the low emission of CO, NOx, and particulate material when combusted. The properties of DME and other fuel are shown in Table 1.