A Soot Radiation Model for Diesel Sprays

Soot radiation has an important contribution to the overall heat losses in a combustion chamber of a DI diesel engine. The aim of this study was to develop a soot radiation model coupled to a soot formation/oxidation sub-model, which is also described in the paper. On the one hand, the soot radiation model is based on the available knowledge of the radiation of a soot cloud commonly used to apply the two-color method to diesel sprays. On the other hand, it was tuned and validated with experimental data: the optical thickness, KL, obtained from the laser extinction method, and the radiation intensity at two different wavelengths. Once the model was validated, the overall radiated power was calculated taking into account the radiation absorption caused by the spray itself. This power was compared to the one released by the spray combustion process, and the results were in agreement with other studies available in the literature. The soot radiation model was applied to a sample HSDI automotive diesel engine to calculate the percentage of radiation in the overall heat losses, and a prediction of around 10% was found for the simulated cases. As an additional but also important contribution of the work, some new knowledge about soot processes in diesel flames is gained.