Large-eddy simulation of diesel spray atomization with phenomenological primary and secondary breakup models

Abstract

Diesel engines are internal combustion engines with auto-ignition of fuel spray atomization, and the control of fuel injection/fuel spray has a significant impact on the combustion process. Numerous optical measurements and numerical simulations of fuel sprays have been carried out. In spray simulation, breakup models are commonly used for the spray atomization process from the viewpoint of computational load. Numerical simulation of fuel sprays is heavily influenced by the breakup model. The model constants need to be adjusted based on the experimental conditions, such as nozzles used, injection pressure, ambient density and fuel, as well as computational settings, such as mesh size. Visualizing fuel sprays is crucial for adjusting the constants, but it increases worker efforts and man-hours in the development process for Diesel engine combustion research. The purpose of this study is to develop a simulation method which required no adjustment and small computational load. This study conducted simulations of spray atomization and dispersion using breakup models for Diesel sprays. To simulate the primary breakup process, the ITD (: Internal turbulence decay) model was used, and the MITAB (: Modified improved Taylor analogy breakup) model was used as the secondary breakup model. Results using the other breakup models, spray tip penetration by scattered light and droplet size distribution by SHSRP(: Super high spatial resolution photography) were evaluated. It was shown that the ITD and MITAB models are highly applicable and useful for general applications due to their high prediction accuracy and low dependence on mesh sizes.