Hydroxyl radicals as an indicator of knocking combustion in the dual-fuel compression-ignition engine

The occurrence of knocking combustion is one of the basic problems of dual-fuel compression-ignition engines supplied with diesel oil and gaseous fuel. In order to detect this phenomenon and evaluate its intensity, several methods are commonly used, including the analysis of pressure of working medium in the combustion chamber of the engine or vibrations of certain engine components. This paper discusses the concept of using mass fraction of hydroxyl radicals as the indicator of the occurrence of knocking combustion. Current knowledge on the conditions of hydroxyl radical formation in the engine combustion chamber has been systematized and the results of research on this subject have been presented. Theoretical considerations are illustrated by exemplary results of simulation studies of the combustion process in a dual-fuel compression-ignition engine supplied with diesel oil and methane. The conclusions drawn may be useful for the development of dual-fuel engine control systems.