4721 Investigation of Knock Characteristics and Its Control Using a Rapid Compression/Expansion Machine

Abstract

A Rapid Compression/Expansion Machine (RCEM) was established to investigate knock characteristics in spark-ignition (SI) combustion. The effects of SI timing and compression ratio were experimentally investigated using the RCEM. High compression ratio and advanced SI timing lead to strong knock. The knock intensity was drastically decreased with a hydrogen injection into near the end of combustion chamber. The scale of knock intensity reduction was higher when the hydrogen injection timing was adjusted close in SI timing. And the knock intensity was lower with larger hydrogen injection quantity under the condition of the SI timing near TDC ; however, it oppositely increased with increase in hydrogen quantity under the SI timing relatively earlier due to excessive flame propagation of the hydrogen included unburned mixture.