A computational study of pre-ignition to detonation transition in a one-dimensional chamber

Abstract

Regulations in CO2 emissions have led to the development of downsized, highly boosted and direct injection technologies that enhance power density and fuel consumption in Spark Ignition (SI) engines. Despite these enhancements, SI engines are prone to exhibit uncontrolled pre-ignition, whose occurrence, specially at low speed and high load, can trigger detonation development which is associated to violent peak pressures and pressure oscillations that can damage the engine. The uncontrolled combustion is a major challenge to overcome for the new generation of SI engines to be widely used. Here, we studied detonation development using high resolution direct numerical simulations of a closed one-dimensional combustion chamber. A highly reactive hydrogen-oxygen mixture with a detailed chemical reaction mechanism is used in this study. Unlike previous studies where bulk mixture properties were arbitrarily defined, we used results from engine simulations obtained with the CONVERGE software to set the initial bulk mixture properties. Depending on the initial conditions two different paths to detonation development were identified: 1) auto-ignition near the wall followed by detonation combustion and 2) transition of the initial propagating flame to detonation combustion mode through flame acceleration.