A Volume-of-Fluid method for variable-density, two-phase flows at supercritical pressure

Poblador-Ibanez, Jordi; Sirignano, William A.

doi:10.48550/arxiv.2103.01874

Cited by 1 publication

(14 citation statements)

References 70 publications

(156 reference statements)

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“…This section provides relevant details about the numerical method used in this work. For a detailed description of the numerical approach used to solve the governing equations and capture the liquid-gas interface, the reader is referred to Poblador-Ibanez and Sirignano [38]. The methodology is validated in the limit of incompressible, two-phase flows, while the extension to low-Mach-number, compressible, twophase flows at high pressures is verified with various benchmark tests.…”

Section: Methodsmentioning

confidence: 99%

“…A predictor-projection method with a first-order, explicit temporal integration is used to address the pressure-velocity coupling for low-Mach-number, two-phase flows. The method is outlined in Appendix B and relies on the split pressure-gradient technique for a fast and computationally efficient pressure update using an FFT or DFT solver [38,47]. Moreover, Appendix B presents the necessary extrapolations of fluid compressibilities and phase-wise velocities into a narrow band of cells across the interface.…”

Section: Methodsmentioning

confidence: 99%

“…The modeling of the interface as a contact discontinuity with negligible thickness and a sudden and sharp jump in fluid properties is a reasonable hypothesis for the specific part of the transcritical injection problem we discuss in this work. The various interface thermodynamic states as deformation and mixing occur are expected to be well below the mixture critical point as shown in Poblador-Ibanez and Sirignano [15,38]. The interface has a negligible thickness of the order of a few nanometers [17,18,20] compared to the fast growth of mass and thermal mixing regions on either side of the interface to the order of micrometers [15,21,22,27].…”

Section: Governing Equationsmentioning

confidence: 99%

“…However, as shown in Davis et al [21], the temperature jump across the interface is negligible when compared to the interface equilibrium temperature despite the small thermal conductivities involved. Further details regarding the validity of our approach are provided in Poblador-Ibanez and Sirignano [38].…”

Section: Governing Equationsmentioning

confidence: 99%

“…Nonetheless, high-pressure effects must be accounted for in detail to fully comprehend the injection process in engines operating at high pressures. Poblador-Ibanez and Sirignano [38] have proposed a physical and numerical model to analyze transcritical flows in the domain of two-phase coexistence. Realfluid effects, as well as mass and thermal mixing are also considered.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Temporal atomization of a transcritical liquid n-decane jet into oxygen

Poblador-Ibanez¹,

Sirignano²

2022

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The injection of liquid fuel at supercritical pressures is a relevant but overlooked topic in combustion. Typically, the role of two-phase dynamics is neglected under the assumption that the liquid will rapidly transition to a supercritical state. However, a transcritical domain exists where a sharp phase interface remains. This scenario is the common case in the early times of liquid fuel injection under real-engine conditions involving hydrocarbon fuels. Under such conditions, the dissolution of the oxidizer species into the liquid phase is accelerated due to local thermodynamic phase equilibrium (LTE) and vaporization or condensation can occur at multiple locations along the interface at the same time. Fluid properties vary strongly under species and thermal mixing, with liquid and gas mixtures becoming more similar near the interface. As a result of the combination of low, varying surface-tension force and gas-like liquid viscosities, small surface instabilities develop early.The mixing process, interface thermodynamics, and early deformation of a cool liquid n-decane jet surrounded by a hotter moving gas initially composed of pure oxygen are analyzed at various ambient pressures and gas velocities. For this purpose, a two-phase, low-Mach-number flow solver for variabledensity fluids is used. The interface is captured using a split Volume-of-Fluid method, generalized for the case where the liquid velocity is not divergence-free and both phases exchange mass across the interface.The importance of transcritical mixing effects over time for increasing pressures is shown. Initially, local deformation features appear that differ considerably from previous incompressible works. Then, the minimal surface-tension force is responsible for the generation of overlapping liquid layers in favor of the classical atomization into droplets. Thus, surface-area growth at transcritical conditions is mainly a consequence of gas-like deformations under shear rather than spray formation. Moreover, the interface can be easily perturbed in hotter regions submerged in the faster oxidizer stream under trigger events such as droplet or ligament impacts. Net mass exchange at high pressures limits the liquid-phase vaporization to small liquid structures.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%