Abstract
Keywords - Diesel, engine, Piston, Slap, Wavelet.
Abstract - The knock generated by the movement of piston near the TDC is an important source of engine noise. It is no easy to identify and measure the contribution of this knock to global engine noise, because the piston generates an impulsive excitation and the response of the system, fundamentally the engine block, depends on its natural frequency. In others words, the loudspeaker is the engine block, thus the frequency of the noise is highly dependent on engine block behavior.
A way to analyze the problem is by using accelerometers located on the cylinder wall inside engine cover. Then it is possible to decompose the vibration signal in two components: One low-frequency component due to combustion and one high-frequency due to the piston slap.
This paper shows the results obtained in a research work about the behavior of different piston configurations in order to analyze the influence on the noise generated at the TDC.
For each piston configuration, two simultaneous measurements have been carried out: the cylinder wall acceleration and the radiated noise register by using microphones near of engine. The paper includes the methodology of signal analysis and a comparison between the results obtained with both types of measurements.