Numerical investigation of liquid jet breakup and droplet statistics with comparison to X-ray radiography

In direct injection engines, the jet primary and secondary breakup processes have a significant influence on the fuel/air mixture formation and drop-size distribution directly affecting the fuel conversion efficiency and combustion characteristics. In this work the disintegration process of turbulent liquid jets from a realistic diesel injector issuing into a still environment is investigated numerically using a coupled liquid/gas interface capturing technique and a high-fidelity DNS/LES approach. This study is aimed at assessing the influence of NJFCP aviation jet fuel mixtures on the disintegration and droplet-size spray characteristics at simulated diesel operating conditions. For this purpose, an unstructured unsplit Volume-of-Fluid method is employed in conjunction with a realistic diesel injector geometry to simulate the pulsed jet disintegration and breakup process. Flow and droplet PDF statistics are extracted to demonstrate the impact of physical properties (A2, C3 fuel) on the mixing behavior and droplet distribution. The simulations are compared against X-ray radiography volume fraction measurements from Argonne National Laboratory and also serve as numerical benchmarks for calibration of lower fidelity models.