Some Perspectives on Alcohol Utilization in a Compression Ignition Engine

This paper addresses some of the practical problems encountered in attempts to use the simple alcohols as alternate fuels in compression ignition (CI) engines for transportation. It is comprised of six sections: 1) the motivations for pursuit of the alcohols for transportation, 2) a brief review of several municipal buses trials in North American cities, 3) relevant literature which is cited to support a hypothesis, 4) the presentation of a hypothesis and solution, 5) some engine performance data to address an issue attendant to the proposed solution, and 6) conclusion. The solution proposes auto ignition of the fuel via intake air heating as a means to overcome the part load engine efficiency problems. However, in implementing this strategy for a direct injection engine, elevated noise has been observed for alcohol operation. This was concluded to be due to a very rapid pressure rise on ignition attendant to air preheating and the high compression ratio of this engine. A different engine with prechamber and glow plug was tested; the purpose was to determine if a continuously operating glow plug would encourage prompt ignition of the alcohol during injection and reduce the observed noise problem. The conclusion reached was that the prechamber itself appears to have solved the noise problem without an energized glow plug.