The Effect of Normal Combustion and Knock on Casoline Engine Noise 891126
The paper describes investigation in origins of automotive gasoline noise with a wide range of combustion characteristics from normal to severe knock.
WITH NORMAL COMBUSTION the noise is due to impulsive oil pressures in the main bearings and a peak cylinder pressures control the emitted noise. The onset of knock produces almost instantaneous pressure rise from 0.5 up to 30 bar, which not only excites the engine structure at natural frequencies between 800 to 2000 Hz, but also excites the natural modes of the combustion chamber cavity resulting in large amplitude cylinder pressure oscillation and emitted noise in the frequency range from 6500 to 20000 Hz.
THE CLEAR DEFINITION of knock induced noise of the engine offers a simple method which can be employed for knock detection and control in a car, particularly that of high speed knock.