Single Cylinder Spark Ignition Engine Study of the Octane, Emissions, and Fuel Economy Characteristics of Methanol-Gasoline Blends 760377

A two phase test program was carried out on a single cylinder, fuel research engine (CFR) to determine the octane, emissions, and fuel economy characteristics of methanol-gasoline blends. The first phase of the work was an evaluation of the octane characteristics of methanol blended with unleaded gasoline. Blends ranging from 2% to 100% by volume methanol for four different base gasolines were knock rated. A simplified mathematical model of the results was developed to aid in comparing the effects of methanol on the octane ratings of the various base fuels. The results indicate that methanol can substantially increase both the Research and Motor Ratings of a relatively low octane unleaded gasoline. However, as the octane rating of the base gasoline is increased, the octane increase produced by the addition of methanol is reduced. For base fuels with Motor Ratings over 85 the addition of methanol has little effect on the Motor Octane rating. Comparisons and data for base fuels having Research Octane Numbers ranging from 81 RON to 98 RON are given.

The second phase of the test program was an evaluation of the emissions and fuel economy of a 10% by volume blend of methanol with two base fuels in the single cylinder engine. Clear Indolene and a 95 RON commercial gasoline were used for these tests. The results for the Indolene blend are presented since both fuels behaved in a similar manner. Where differences did exist appropriate comments are included. For the blends examined, the specific emissions (gm/ihp-hr) were changed very little by the addition of methanol when the engine was operating at equivalent spark, speed, and stoichiometry. Although the addition of methanol increased the ISFC, the thermal efficiency of the engine was not significantly changed.

General conclusions were that a blend of 10% methanol and gasoline demonstrated no significant change in the emissions or energy efficiency over the gasoline fueled engine when operated at equivalent conditions. Under some operating conditions, the addition of methanol could increase the octane rating of the base fuel. This increase could conceivably be enough to reduce knock problems in some vehicles.