Abstract
Since the invention of spark ignition engines, knocking has been the limiting factor in the development of new engines with increased power density and improved efficiency. The mechanisms that lead to knocking combustion have been investigated in numerous research studies that have produced, to some extent, controversial theories. Even though it is very certain that knocking involves a detonation caused by self-ignition processes in the end-gas region, there is a great interest in growing the understanding of knocking phenomena and the associated multitude of combustion irregularities. This article gives an overview of the contemporary state of knowledge of knocking and other irregular combustion phenomena. In order to present the current understanding of knocking and combustion irregularities, historical knocking investigations, meaningful work on knocking in the last two decades of the previous century, and contemporary investigations are examined. In addition, this article discusses the information that remains unknown and the areas in which further research and development are necessary, so that today's questions about these phenomena can be answered in the future. For the purpose of describing and evaluating knocking and other combustion irregularities, not only experimental investigations will be employed, but also theoretical considerations.
