Rivista La Termotecnica - Accesso riservato soci CTI

Autore: G. Cantore, A. d'Adamo, S. Fontanesi

Collana: 2019, numero 05

Note:
Engine knock is emerging as the main limiting factor for modern spark-ignition (SI) engines, facing increasing thermal loads and seeking demanding
efficiency targets. To fulfill these requirements, the engine operating point must be moved as close as possible to the onset of abnormal combustion
events. The turbulent regime characterizing in-cylinder flows and SI combustion leads to serious fluctuations between consecutive engine cycles. This
forces the engine designer to further distance the target condition from its theoretical optimum, in order to prevent abnormal combustion to severely
damage the engine components just because of few individual heavy-knocking cycles. A RANS-based model is presented in this study, which is able to predict not only the ensemble average knock occurrence, poorly meaningful in such a stochastic event, but also a knock probability. The model allows to identify not only the regions where the average knock first occurs, but also where the first knock probability is more likely to be encountered, adding a relevant contribution to the consolidated “average knock” analysis of RANS approach.