Entropy Analysis of Microscopic Diffusion Phenomena in Diesel Sprays(<Special Issue>Recent Combustion Technology in Internal Combustion Engines)

Rapid mixing of fuel and air is an essential factor in improving combustion and emissions of diesel engines, and it is important to know the relationship between the microscopic structure of the heterogeneous distribution of fuel clouds and the local turbulence structure. This paper investigates local diffusion phenomena in sprays with focusing on scales of fuel cloud and eddies based on a newly developed entropy method. The results show that the diffusion intensity is the highest in the vicinity of the nozzle exit, and the heterogeneity scale is the smallest here. The heterogeneity scale increases gradually along the spray axis towards the downstream, with smaller size scales in the large clouds. In the downstream region, small-scale structures diffuse and become unclear, while large scale structures clearly remain. The paper details the microscopic structure of the heterogeneity in diesel sprays, and it demonstrates availability of the entropy method.