Ignition Delay and Emissions Characteristics of a Methanol-Diesel Fueled Engine at Low Charge Temperatures

An experimental study was performed to determine the effects of intake air and intake charge temperature on emissions and combustion performance of a diesel engine using air atomized methanol fumigation and diesel fuel injection. A single cylinder, air cooled, naturally aspired direct injection type diesel engine was used in the investigation. Inlet charge temperature was varied over a range of 25°C to -5°C by heating and/or cooling inducted air.

Decreasing inlet charge temperature reduced peak cylinder pressure and increased ignition delay period at a given methanol energy fraction supplied to the engine. Engine thermal efficiency, though it was higher than that experienced with neat diesel fuel over most of the alcohol energy fractions range, decreased as the inlet charge temperature was reduced. Increasing inlet charge temperature for a given methanol fumigation rate increased smoke emitted by the engine, but even with these increased values, the levels of smoke emitted by the engine were significantly lower than those emitted by neat diesel fuel at identical engine operating conditions. NO_x emissions decreased as the fraction of methanol energy supplied to the engine increased. At a given methanol energy supply rate, reducing inlet charge temperature resulted in lower NO_x; the effect was more significant at zero and sub-zero temperatures.