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Methanol-fueled diesels may be an attractive means of meeting future, more restrictive diesel particulate standards since methanol combustion forms very little soot. Unfortunately, methanol's autoignition temperature is high, and some means of improving its ignition is required. Therefore, we have investigated the use of dimethyl ether (DME), aspirated with the combustion air, to enhance the ignition of the injected methanol. A small, on-board catalytic reactor could be used to generate DME from the methanol fuel. This system requires minimal modifications to the engine design, and does not require use of an additive or fuel other than methanol. In this study, we measured maximum cylinder pressure and rate of pressure rise, ignition delay, emissions, and relative efficiencies for a single-cylinder, direct injection, high-speed diesel engine operated on both diesel fuel and methanol-DME.

Dimethyl ether has high vapor pressure and wide flammability limits, which make it an excellent fuel for cold starting methanol engines. We have investigated the catalytic dehydration of methanol to produce dimethyl ether on board methanol-fueled vehicles. We tested four methanol dehydration catalysts in a microcatalytic plug flow reactor and found that a fluorinated γ-alumina was very active and selective for methanol dehydration in the 250-350°C (482-662°F) temperature range. We also tested the fluorinated γ- alumina catalyst with a 15% gasoline/85% methanol mixture (M85) and found that the catalyst activity decreased in proportion to the gasoline content but that no catalyst deactivation occurred. Data from the catalyst testing were used to design an electrically-heated methanol dehydration reactor ‘that could be used on board a methanol fueled vehicle.