Session: 04-01: Powertrain Diagnostics and Control Strategies

Paper Number: 139358

139358 - Characterization of Knocking Pressure Data From Two Closely Spaced Transducers: Effect of Transducer Mounting 

Abstract: 

In this study, pressure data acquired simultaneously from two different, closely spaced pressure transducers were compared to understand the quantification of knock intensity. The comparison between four different transducer models located in the same position showed very small changes in the power spectral density, suggesting that the transducer has a limited effect on the results. Simultaneous data were acquired pairwise using the four transducers and were analyzed in both the time and frequency domains. It was found that the mounting location significantly affected the results, which was shown to be the result of a small passage (l/d=1.5) between the transducer face and the cylinder wall that was formed due to the angle needed to mount the transducer. The passage produced a broadband disturbance in the frequency domain from 30-50 kHz; this affects the knocking results but largely does not affect the heat release analysis. A time-domain analysis was performed to  investigate biases that can affect the knock metrics. A moving-window cross correlation between the two signals, which eliminates any phase differences, showed that there was high correlation between the signals on a cycle-by-cycle basis. The knock intensity, characterized by the maximum amplitude of pressure oscillations, however showed poor correlation. The difference in the knock intensity was also evaluated using a ring-down magnitude method, which showed better comparison. Recommendations for, and assessment of the absolute quantification of knock intensity are provided.

Presenting Author: Andrea Caselli University of Pisa

Presenting Author Biography: Andrea Caselli studies for his PhD program at the University of Pisa, in Italy, under the supervision of Prof. Stefano Frigo. During the first two years of his doctorate, Andrea spent one year at the University of Wisconsin-Madison under the supervision of Prof. Jaal Ghandhi, working on knock-related studies with experimental data acquisition. In addition, Andrea's research is also focused on engine improvement. In particular, he is developing a CFD model for oil jet spray simulations for piston cooling purposes in collaboration with Asso Werke, which is a company that produces pistons for high-performance engines. The aim of the project is the prediction of the working temperature map of the solid to achieve an optimal thermo-structural design of the piston.

Authors:

Andrea Caselli University of Pisa
Stefano Frigo University of Pisa
Jaal Ghandhi University of Wisconsin-Madison