Physics-based reduced-order modeling of flash-boiling sprays in the context of internal combustion engines

• Main Authors: Saha, Avijit, Deshmukh, Abhishek Y, Grenga, Temistocle, Pitsch, Heinz
• Format: Journal Article
• Language: English
• Published: 07-07-2023
• Subjects: Physics - Applied Physics; Physics - Fluid Dynamics
• DOI: 10.48550/arxiv.2307.03722

Flash-boiling injection is one of the most effective ways to accomplish
improved atomization compared to the high-pressure injection strategy. The tiny
droplets formed via flash-boiling lead to fast fuel-air mixing and can
subsequently improve combustion performance in engines. Most of the previous
studies related to the topic focused on modeling flash-boiling sprays using
three-dimensional (3D) computational fluid dynamics (CFD) techniques such as
direct numerical simulations (DNS), large-eddy simulations (LES), and
Reynolds-averaged Navier-Stokes (RANS) simulations. However, reduced order
models can have significant advantages for applications such as the design of
experiments, screening novel fuel candidates, and creating digital twins, for
instance, because of the lower computational cost. In this study, the
previously developed cross-sectionally averaged spray (CAS) model is thus
extended for use in simulations of flash-boiling sprays. The present CAS model
incorporates several physical submodels in flash-boiling sprays such as those
for air entrainment, drag, superheated droplet evaporation, flash-boiling
induced breakup, and aerodynamic breakup models. The CAS model is then applied
to different fuels to investigate macroscopic spray characteristics such as
liquid and vapor penetration lengths under flash-boiling conditions. It is
found that the newly developed CAS model captures the trends in global
flash-boiling spray characteristics reasonably well for different operating
conditions and fuels. Moreover, the CAS model is shown to be faster by up to
four orders of magnitude compared with simulations of 3D flash-boiling sprays.
The model can be useful for many practical applications as a reduced-order
flash-boiling model to perform low-cost computational representations of
higher-order complex phenomena.