Numerical Modeling of Transcritical and Supercritical Fuel Injections Using a Multi-Component Two-Phase Flow Model

Abstract

In the present numerical study, implicit large eddy simulations (LES) of non-reacting multi-components mixing processes of cryogenic nitrogen and n-dodecane fuel injections under transcritical and supercritical conditions are carried out, using a modified reacting flow solver, originally available in the open source software OpenFOAM®. To this end, the Peng-Robinson (PR) cubic equation of state (EOS) is considered and the solver is modified to account for the real-fluid thermodynamics. At high pressure conditions, the variable transport properties such as dynamic viscosity and thermal conductivity are accurately computed using the Chung transport model. To deal with the multicomponent species mixing, molar averaged homogeneous classical mixing rules are used. For the velocity–pressure coupling, a PIMPLE based compressible algorithm is employed. For both cryogenic and non-cryogenic fuel injections, qualitative and quantitative analyses are performed, and the results show significant effects of the chamber pressure on the mixing processes and entrainment rates. The capability of the proposed numerical model to handle multicomponent species mixing with real-fluid thermophysical properties is demonstrated, in both supercritical and transcritical regimes.

Assessment of an Open-Source Pressure-Based Real Fluid Model for Transcritical Jet Flows

“…For the time discretisation, the first order Euler scheme is used and as for both advection and diffusion, second order accurate Gauss limitedlinear schemes are adopted. Further details about the solver can be found in [19,26]. It should also be noted that the current approach does not consider phase change; but instead the adiabatic mixing temperature, also called frozen temperature, is calculated.…”

“…It has been therefore the main focus of many researchers to develop numerical strategies in order to achieve both stability and accuracy [7,[14][15][16][17][18]. This present study follows previous works carried out in [19] to simulate multicomponent mixture species spray mixing processes with real-fluid thermophysical properties on both cryogenic and non-cryogenic fuel injections. However, here the thermophysical models have been modified to incorporate more convenient mixing rules.…”

“…Here and for the remaining part of this work, the subscript "c" refers to the critical condition and ω i indicates the acentric factor of the species i. It should be noted that different mixing rules and combining rules are applied in [19] which are based on the linear blend Kay's rule. The critical properties used within the scope of this current study is summarized in Table 1.…”

“…Furthermore, the mixture properties indicated by the subscript "m" are evaluated following the combination rules detailed in [25]. This counts also among the modifications made to the model introduced in [19] where similar molar weighted averages based mixing rules as for the EOS are used. The thermal conductivity is evaluated following the same principle as for the dynamic viscosity and as given by Chung et al [25].…”

Towards Understanding the Structure of Subcritical and Transcritical Liquid–Gas Interfaces Using a Tabulated Real Fluid Modeling Approach

“…Interest in the behavior of supercritical fluids is not new, dating back to at least 1869 [13]. Over the past few decades, researchers have conducted several studies to better understand the dynamics of multiphase flows in this regime [5,6,[8][9][10][11][12][14][15][16].…”