ID 262

Validation of a New Turbulence-Induced Lagrangian Primary Breakup Model for Diesel Spray Atomization

 

Abstract:

Accurate modeling of liquid atomization is essential for predictive diesel engine simulations, but current limitations in our understanding of the governing physics and a general lack of detailed quantitative measurements have prevented significant advances. Although the classic Kelvin-Helmholtz model of aerodynamicallydriven jet breakup (primary breakup) has been widely employed in engine CFD codes for the last three decades, the model is not generally predictive. This lack of predictive capability points to the likelihood of an incorrect physical basis for the model formulation. As such, there have been more recent spray-model development efforts that incorporate additional sources of jet instability and breakup, including nozzle-generated turbulence and cavitation (e.g., KH-ACT and Huh-Gosman models), but predictive capabilities have remained elusive. Detailed atomization measurements taken over a wide span of engine-relevant operating conditions are urgently needed to both confirm appropriate physical formulation of models and to accurately validate their predictions. In addition, as diesel engines increasingly operate under low-temperature combustion (LTC) conditions, where ambient densities and aerodynamic forces are much lower than under conventional diesel conditions, further consideration of physical model formulation is needed. In previous work, we introduced a new primary atomization modeling approach premised on experimental measurements by the Faeth group, which demonstrate that breakup is governed by nozzle-generated turbulence under low ambient density conditions. In this new modeling approach, termed the KH-Faeth model, two different primary breakup models are combined to allow the hybrid breakup modeling approach, i.e. Kelvin- Helmholtz instability breakup mechanism and turbulence-induced breakup are competed via dominant breakup rate evaluation. In the current work, we implement this hybrid KH-Faeth model within the open-source CFD framework OpenFOAM and validate the model against detailed drop sizing measurements stemming from recent collaborative experiments between Georgia Tech and Argonne National Laboratory.