Studies of real-fluid supercritical simulation using the 3rd virial equation of state based on Boltzmann-weighted Full-dimensional potential

Abstract

Under extreme conditions such as supercritical combustion, real-fluid effects become significant, necessitating accurate and robust simulation methodologies for high-pressure environments. In this study, we propose a real-fluid simulation method, the BWF-Virial method, which integrates the Boltzmann-weighted Full-dimensional (BWF) potential into the virial equation of state (EoS) for physical properties and combustion characteristics simulations under high to ultra-high pressures. Based on the BWF potential model, the second and third virial coefficients, along with their corresponding thermodynamic and transport properties, are rigorously derived. These methods are subsequently integrated into the Cantera software package, establishing a comprehensive real-fluid simulation platform. The BWF-Virial method attains the accuracy of the third-order virial EoS, thereby offering a precise description of real-fluid behavior for various fuels. Its effectiveness has been validated through thermodynamic and transport property calculations across various species, with relative errors of 0.1%–10%. We further investigate zero-dimensional and one-dimensional combustion characteristics of supercritical methane and n-heptane. The BWF-Virial method demonstrates strong robustness and predictive accuracy in modeling combustion phenomena across a wide range of extreme operating conditions. Compared to the LJ-Virial method, it exhibits a 5%–20% difference, aligning more closely with experimental data and reinforcing its potential for high-fidelity supercritical combustion simulations.

Novelty and significance statement

The novelty of this research lies in the development of the BWF-Virial method for real-fluid supercritical simulations. Real-fluid effects are significantly amplified in non-ideal flows, such as supercritical fluids and plasmas. These flows are highly relevant to propulsion and energy conversion processes. Unfortunately, the real-fluid intermolecular interactions in the literature are mainly based on the Lennard-Jones potential, which reveals significant errors for physical properties and combustion simulations at high to ultra-high pressures, especially for polar and long-chain molecules. The BWF-Virial method can effectively overcome these limitations. It provides comprehensive and robust support in (i) the thermodynamic and transport property library establishment for polar and long-chain molecules, (ii) the reactive real-fluid combustion simulations, and (iii) the physical investigations of real-fluid impact on reactive flow simulations.