Quantification of mixture composition, liquid-phase fraction and - temperature in transcritical sprays

Klima, Tobias C.; Peter, Andreas; Riess, Sebastian; Wensing, Michael; Braeuer, Andreas

doi:10.1016/j.supflu.2020.104777

Cited by 23 publications

(5 citation statements)

References 19 publications

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“…Details about this algorithm and its extension to compressible liquids are explained in the following paragraphs and shown in Eqs. (19), (20) and (21).…”

Section: The Volume-of-fluid Methods For Compressible Liquidsmentioning

confidence: 99%

“…Therefore, the interface may be subject to rapid growth of small surface instabilities and fast distortion, which can cause early breakup of very small droplets. Although some progress is being made towards new experimental techniques to capture the two-phase behavior in supercritical pressure environments [16][17][18][19], traditional methods relying on visual techniques (e.g., shadowgraphy) might suffer from scattering and refraction issues due to the presence of a cloud of small droplets submerged in a variable-density fluid. Numerical results of incompressible liquid round jets and planar sheets under conditions similar to those found at supercritical pressures support this reasoning [20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

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

Poblador-Ibanez,

Sirignano

2021

Preprint

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A two-phase, low-Mach-number flow solver is proposed for compressible liquid and gas with phase change.The interface is tracked using a split Volume-of-Fluid method, which solves the advection of the reference phase (i.e., liquid). This split advection method is generalized for the case where the liquid velocity is not divergence-free and both phases exchange mass across the interface, as happens at near-critical and supercritical pressure conditions. In this thermodynamic environment, the dissolution of lighter gas species into the liquid phase is enhanced and vaporization or condensation can occur simultaneously at different locations along the liquid-gas interface. A sharp interface is identified by using a Piecewise Linear Interface Construction (PLIC). Mass conservation to machine-error precision is achieved in the limit of incompressible liquid, but not with the liquid compressibility and mass exchange.The numerical cost of solving two-phase, supercritical flows is very high because: a) local phase equilibrium is imposed at each interface cell to determine the interface solution (e.g., temperature, composition); b) a complete thermodynamic model is used to obtain fluid properties everywhere; and c) phase-wise values for certain variables (i.e., velocity) are obtained via extrapolation techniques. Furthermore, the Volume-of-Fluid method and the PLIC add extra computational costs to any two-phase flow solver. To alleviate this numerical cost, the pressure Poisson equation (PPE) is split into a constant-coefficient implicit part and a variable-coefficient explicit part. Thus, a Fast Fourier Transform (FFT) method can be used for the PPE, which directly solves the continuity constraint to machine-error precision.Various validation tests are performed to show the accuracy and viability of the present approach. Then, the growth of surface instabilities in a binary system composed of liquid n-decane and gaseous oxygen at

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“…Details about this algorithm and its extension to compressible liquids are explained in the following paragraphs and shown in Eqs. (19), (20) and (21).…”

Section: The Volume-of-fluid Methods For Compressible Liquidsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Poblador-Ibanez,

Sirignano

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Therefore, the interface may experience a fast growth of small surface perturbations, resulting in the early breakup of small droplets and mixing enhancement. Despite some progress toward developing new experimental techniques for capturing two-phase behavior in supercritical pressure environments [28][29][30][31], traditional visual techniques (e.g., shadowgraphy or ballistic imaging) may suffer from scattering and refraction issues under the presence of a cloud of small droplets submerged in a variable-density fluid.…”

Section: Introductionmentioning

confidence: 99%

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

Poblador-Ibanez¹,

Sirignano²

2022

Preprint

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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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“…This mainly stems from the interaction between the injectant and the surrounding gas, see also [55]. For more details, the reader may refer to the works by Anitescu et al [6], Chehroudi [12], Klima et al [21], Oefelein [33], and therein included references. Additional observations have been reported in which the droplets undergo a gradual transition from subcritical evaporation to mixing regime at different pressure and temperature above the pure fuel critical point.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Simulation of a Turbulent Multi-component Two-phase Flow Involving Phase Change Processes Under Supercritical Conditions

Kuetemeier

Sadiki

2022

Fluid Mechanics and Its Applications

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The present paper aims at developing a generally valid, consistent numerical description of a turbulent multi-component two-phase flow that experiences processes that may occur under both subcritical and trans-critical or supercritical operating conditions. Within an appropriate LES methodology, focus is put on an Euler-Eulerian method that includes multi-component mixture properties along with phase change process. Thereby, the two-phase flow fluid is considered as multi-component mixtures in which the real fluid properties are accounted for by a composite Peng-Robinson (PR) equation of state (EoS), so that each phase is governed by its own PR EoS. The suggested numerical modelling approach is validated while simulating the disintegration of an elliptic jet of supercritical fluoroketone injected into a helium environment. Qualitative and quantitative analyses are carried out. The results show significant coupled effect of the turbulence and the thermodynamic on the jet disintegration along with the mixing processes. Especially, comparisons between the numerical predictions and available experimental data provided in terms of penetration length, fluoroketone density, and jet spreading angle outline good agreements that attest the performance of the proposed model at elevated pressures and temperatures. Further aspects of transcritical jet flow case as well as comparison with an Eulerian-Lagrangian approach which is extended to integrate the arising effects of vanishing surface tension in evolving sprays are left for future work.

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Quantification of mixture composition, liquid-phase fraction and - temperature in transcritical sprays

Cited by 23 publications

References 19 publications

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

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

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

Modeling and Simulation of a Turbulent Multi-component Two-phase Flow Involving Phase Change Processes Under Supercritical Conditions

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