Experiments on Cylinder Pressure Pulsation and Distribution in a Swirl-Chamber-Type Automotive Diesel Engine: Idling Knocking Noise Induced by Non-Uniformly Distributed Cylinder Pressure Pulsation

The generation mechanism of the knocking-like, characteristic engine noise in a swirl-chamber-type, automotive engine was investigated.

This characteristic engine noise was particularly dominant in cold weather and at idling conditions.

It was found that in cold weather, cylinder pressure pulsations of significant amplitude can be induced in the main chamber by the cavity resonance of the swirl chamber and throat, but the pulsations distribute non-uniformly on the piston top surfaces.

Collisons between the pistons and the cylinder liners were induced by the pulsating, non-uniformly distributed cylinder pressure, therefore engine structure noise was generated.