Spark knock pressure oscillations can be detected by a cylinder pressure transducer or by an accelerometer mounted on the engine block. Accelerometer-based detection is lower cost but is affected by extraneous mechanical vibrations and the frequency response of the engine block and accelerometer. The knock oscillation frequency changes during the expansion stroke because the chamber geometry is changing due to the piston motion and the burned gases are cooling. Spectrogram analysis shows the time-dependent frequency content of the pressure and acceleration signals, revealing characteristic signatures of knock and mechanical vibrations. Illustrative spectrograms are presented which yield physical insight into accelerometer-based knock detection.
Spectrogram Analysis of Accelerometer-Based Spark Knock Detection Waveforms
Sae Technical Papers
SAE Noise and Vibration Conference and Exposition ; 1997
1997-05-20
Conference paper
English
Pistons , Engine cylinders , Pressure , Knock
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