Abstract:

Knocking characteristics were investigated by using engine bench tests for a combustion of DI-HCCI
(direct-injection homogeneous charge compression ignition) with blend fuels of ethanol and gasoline. Some
improvements were done to a traditional two-cylinder diesel engine in fuel supply system, ignition system, and
inlet and exhaust system. A knock model was established according to the engine bench tests and the cylinder
pressure signals to describe ethanol and gasoline HCCI combustion. Knock intensity (KI) was drawn from the
model and then was measured in the tests. The results show that the average KI and the knock probability
significantly decrease with the blending ratio of ethanol and gasoline, i.e. the percentage of ethanol increases,
while the knock starting phase retards. Knock boundaries also narrow down with high blending ratio, while the
upper and lower boundaries move towards each other. Those results could lead to the development of better
fuel injection strategies.