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The use of alcohol as a supplemental fuel for a medium-speed diesel engine was investigated using a two-cylinder, two-stroke test engine. Both stabilized and unstabilized emulsions of methanol-in-diesel fuel and ethanol-in-diesel fuel were tested. Also, anhydrous ethanol/diesel fuel solutions were evaluated. Maximum alcohol content of the emulsions and solutions was limited by engine knocking due to a reduction in fuel cetane number. Engine power and thermal efficiency were slightly below baseline diesel fuel levels in the high and mid-speed ranges, but were somewhat improved at low speeds during tests of the unstabilized emulsions and the ethanol solutions. However, thermal efficiency of the stabilized emulsions fell below baseline levels at virtually all conditions.

Interest in alternative diesel fuels has led to consideration of various types of poor ignition quality products, such as a broad cut fuel or a synthetic fuel/DF-2 blend. Attempts were made to expand the cetane number tolerance limit of an EMD 567B medium-speed diesel engine through staged injection to permit operation on such fuels. A small portion of the fuel was injected early in the cycle to act as a pilot for the main fuel charge. Both pilot and main charges were the same fuel. Knocking was eliminated on fuels with cetane numbers as low as 17 at the standard 16:1 compression ratio. Attempts to operate on methanol at 20:1 failed, but such operation may be feasible with further modifications.