Combustion and Emissions Characteristics of Minimally Processed Methanol in a Diesel Engine Without Ignition Assist 940326

Mixtures of methanol, water and heavier alcohols, simulating “raw’ methanol at various levels of processing, were tested in a constant volume combustion apparatus (CVCA) and in a single-cylinder, direct-injection diesel engine. The ignition characteristics determined in the CVCA indicated that the heavier alcohols have beneficial effects on the auto-ignition quality of the fuels, as compared to pure methanol. Water, at up up to 10 percent by volume, has little effect on the ignition quality. In all cases, however, the cetane numbers of the alcohol mixtures were very low.

The same fuels were tested in a single cylinder engine, set-up in a configuration similar to current two-valve DI engines, except that the compression ratio was increased to 19:1. Pure methanol and five different blends of alcohols and water were tested in the engine at five different speed-load conditions. The engine was operated at conditions simulating turbocharging with no intercooling, so that the inlet air temperatures were in the range of 120-145° C. It was possible to achieve auto-ignition on all of the fuels at all five test conditions. The smoke emissions were very low on all fuels at all operating conditions. In addition, the hydrocarbon and nitric oxide emissions were equivalent to the corresponding data for diesel fuel at high load, and higher than the diesel fuel data at light load. There were no systematic differences between the fuels or with neat methanol so that it appears that both the water and the heavier alcohols have little impact on the combustion of the methanol.