Variation of Knocking Characteristics with the Chamber Wall Temperature in a Spark-Ignition Engine

This study aims to clarify the importance of chamber wall temperature in the knocking characteristics of a spark-ignition engine. To vary the chamber wall temperature, two procedures were used, one is to change the coolant temperature and the other is to raise the exhaust valve surface temperature by substituting a ceramic surface layer for the original steel layer. Although the coolant temperature change had no influence on the flame propagation process, it fairly affected the knocking process, such as mean knock intensity and mean knock occurrence timing. This is caused by both the change of bulk mixture temperature of the end gas and the temperature uniformity within the end gas region. Cycle-by-cycle based knocking behaviour can also be influenced by the coolant temperature, which is considered to be based on the temperature uniformity in the whole chamber region. Exhaust valve surface temperature change did not affect any knocking characteristics. It suggests the importance of the wall temperature in the end gas region.