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Detection of the knock in diesel engines by using the Choi-Williams distribution

Abstract:

This paper focuses on the detection of knocking features in the combustion process based in time-frequency analysis using Choi-Williams distribution(CWD). The source data is the cylinder pressure from a Diesel engine. The resonances were carried out, the envelopes of each resonances were extracted and exponentially declining models were adapted. With the assumption that the expansion process is adiabatic, the volume and the temperature are related by a well-know expression. This implies a straightforward relationship between frequencies resonances and the volume of the combustion chamber. Time-variations of frequencies were extracted and the thermodynamic model was adapted. The adiabatic coefficient and initial crank angle at knocking combustion were also determined. The results showed that the two first resonances due to knock phenomena were detect about -0.11 radianer with a standard deviation of ± 0.08 radianer.