Analysis of the independent components from images of transient reactive flows

This paper reports on the application of independent component analysis (ICA) to 2D images of combustion-related luminosity, acquired from two single-cylinder optically accessible engines: a Euro 5 Diesel and a port fuel injection spark ignition. Independent components (IC) are extracted from sets of luminosity images, and their coefficients are used to identify leading independent structures and to study the transient during a single cycle. In a single Diesel cycle, the independent components appear to be clearly separated and related to combustion events near the fuel jets and near the bowl walls: quantitative analysis of coefficient statistics confirms lower variability of the jet flames with respect to combustion near the chamber walls. The spark ignition analysis employs three ICs, which correspond to start of ignition, middle propagation and end of combustion. The developed procedure, including the ICA, is fast and reliable and can be prospectively applied to many different optical engine configurations.