An LES model with finite-rate phase change and subgrid spray based on a thermodynamically consistent four-equation multiphase model

TL;DR

This paper introduces a thermodynamically consistent LES model for multiphase flows with finite-rate phase change and subgrid spray, validated against experimental data for engine spray conditions.

Contribution

It develops a new four-equation multiphase model with a phase-confined spray model and thermodynamically bounded phase change, improving computational efficiency and predictive accuracy.

Findings

Model shows excellent agreement with ECN Spray A experimental data.

The four-equation model reduces computational cost compared to non-equilibrium models.

The phase-confined spray model accurately predicts subgrid interfacial surface area.

Abstract

In this work, an LES model with finite-rate phase change and subgrid spray based on a high-resolution numerical scheme for multiphase multi-component simulations which satisfies interface equilibrium and phase immiscibility conditions is proposed. The multiphase model is based on a robust implementation of the four-equation multiphase model which assumes a strict subgrid equilibrium of pressure, temperature, and velocity. Critically, the equilibrium assumptions of the four-equation model provide large computational savings compared to modeling the full non-equilibrium multiphase system. To obtain predictive capabilities with these restrictive equilibrium assumptions, a new phase-confined form of the Eulerian $\Sigma$ spray model is proposed to predict subgrid interfacial surface area while avoiding unphysical leakage across interfaces. Additionally, an improved finite rate phase change model which is thermodynamically bounded by the equilibration of the Gibbs-free energy is coupled with the $\Sigma$ equation to model complex phase change regimes. The full modeling framework is validated using the Engine Combustion Network (ECN) Spray A case in non-evaporating and evaporating conditions and shows excellent agreement with experimental measurements.