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During the 1980's, vegetable oils, microemulsions containing fatty alcohols as surfactants, and fatty esters have been extensively investigaed as alternative fuels to #2 diesel fuel (DF-2) used in farm tractors. Despite the importance of vegetable oils (mainly triglycerides) and fatty derivatives to the alternative fuel program, cetane numbers for pure triglycerides and many fatty derivatives were not reported. In the current study, estimated cetane numbers of these materials have been determined by use of a constant volume combustion bomb. Prior research has shown that this equipment can produce cetane numbers that correlate satisfactorily with engine cetane numbers as determied by ASTM D 613. The influence of chemical structure on ignition delay and cetane number was investigated. Evidence is presented that shows the current cetane number scale is not always suitable for these fatty materials. Suggestions are made as to what might be done to remedy this problem.

Four major coal fuel projects which were performed at Southwest Research Institute over the past ten years are reviewed. Beginning with the “Alternative Fuels for Highway Utilization” project in 1979, and the success of carbon-black/diesel fuel slurries, the development of the coal slurries is traced to the current technology. Most recently, full-scale locomotive engines have been operated on 50% coal in water slurries at thermal efficiencies approaching that of diesel fuel performance. The paper is concluded with a recommended engine design for coal slurries.