One way to develop an understanding of soot formation and oxidation processes that occur during direct injection and combustion in an internal combustion engine is to image the natural luminosity from soot over time. Imaging is possible when there is optical access to the combustion chamber. After the images are acquired, the next challenge is to properly interpret the luminous distributions that have been captured on the images. A major focus of this paper is to provide guidance on interpretation of experimental images of soot luminosity by explaining how radiation from soot is predicted to change as it is transmitted through the combustion chamber and to the imaging. The interpretations are only limited by the scope of the models that have been developed for this purpose.
The end-goal of imaging radiation from soot is to estimate the amount of soot that is present. The method selected for making such estimates is to model the combustion and sooting events with computational fluid dynamics (CFD), post-process the CFD results to generate 3D distributions of the soot-radiation field, model the transformation of the 3D distribution to a 2D distribution that is representative of luminosity captured by the camera, derive a relationship between the projected 2D luminosity and the amount of CFD-predicted in-cylinder soot, and finally, apply that relationship to experimental images thus giving an estimate of actual amount of in- cylinder soot that is present. Model descriptions, how the models are implemented and results of their application are included in this paper.
