Some Heat Release Aspects of Compression Igniting a Single-Cylinder DI Diesel on Neat Methanol 892055
Tests were performed on a single-cylinder direct-injection (DI) research diesel engine to evaluate the influence of methanol fuel on net heat release. The test program examined the use of a small pilot injection of methanol and intake-air heating as a means of compression igniting (CI) the main methanol injection. Heat-release characteristics calculated from pressure-time data and engine observations were compared between methanol and no. 2 diesel fuel.
It was found that using a small pilot approximately 20 deg CA BTDC and increasing the intake temperature to about 100 deg C gave very consistent ignition. Rate shaping of the main injection was necessary to avoid too fast initial combustion during the main injection. The maximum rate of premixed combustion was approximately half of normal diesel values, and the maximum rate of diffusion combustion was higher at low load but lower at high load for methanol.
Exhaust hydrocarbons were two to three times higher for methanol than for diesel fuel, whereas nitrogen oxides were approximately half and soot (measured as Bosch number) was almost absent using methanol. The indicated thermal efficiency for the two fuels was similar.