Regularities of Cylinder Pressure Oscillations and their Effects on the Combustion Process and Noise

CYLINDER PRESSURE OSCILLATIONS in Diesel engines are known to arise with the beginning of combustion. They excite resonant oscillations in the cylinder's bulk load, which generally have been considered unimportant for combustion noise or thermodynamic effects.

A new method of investigation has been developed by means of a proprietary computer program for the general analysis of acoustic signals (SIAN). Adapted to investigations of the cylinder-pressure signal it showed, that resonant oscillations dominate the entire high-frequency cylinder-pressure spectrum. These oscillations govern the annoying high frequent combustion noise as well as the combustion speed and, thus, the combustion process itself.