Dimethyl Ether as a Methanol Ignition Improver: Substitution Requirements and Exhaust Emissions Impact

Methanol is one of the leading alternatives to diesel fuel and gasoline. In Diesel applications methanol's low cetane number has necessitated the use of glowplugs, spark plugs or expensive additives for ignition assistance.

This paper reports on the use of Dimethyl Ether (DME) as an ignition improver for neat methanol in a compression ignition engine. Gaseous DME was admitted to the intake air stream of a four stroke test engine operating on directly injected methanol. The amount of DME required to achieve stable operation over the load/speed range of the engine without the use of a glow plug was determined. DME's effect on ignition delay and rate of pressure rise is discussed. Exhaust emissions were measured and compared with operation on methanol with glow plug assisted ignition. Hydrocarbon emissions were reduced by a factor of 10 at light loads. Aldehyde emissions were also reduced.