Mixture fraction statistics in methane-oxygen turbulent combustion for space propulsion

Martínez-Sanchis, Daniel; Sternin, Andrej; Balbuena-Silvestre, Daniel; Haidn, Oskar

doi:10.1016/j.ast.2023.108355

Cited by 3 publications

(1 citation statement)

References 28 publications

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“…Recent research is mainly focused on the mixture fraction probability density function (PDF) modeling. [28][29][30] However, modeling the mixture fraction transport in the frame of Reynolds Average Navier-Stokes (RANS) has received little attention, although this is the most common approach followed industrially. In most extended solvers, several transport sources are often neglected or modeled with simple gradient assumptions.…”

Section: Introductionmentioning

confidence: 99%

Analysis of turbulent mixing in a methane–oxygen recessed injector for space propulsion

2023

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Turbulent mixing in a methane–oxygen recessed injector is studied using direct numerical simulations. The operating point is chosen to be fuel-rich and at high pressure to recreate a representative environment for space propulsion applications. The results are used to investigate the transport of the turbulent mixture fraction statistics and the validity of conventional transport models. It is observed that molecular diffusion is only relevant near the boundary layer of the injection recess cavity and at the recirculation zone. Moreover, turbulent mixing in the axial direction is negligible as radial turbulent diffusion dominates. Radial turbulent diffusion near injection is driven by Kelvin–Helmholtz Instabilities (KHI) manifesting at large scales in the order of the injector geometry. The dominance of this process over microscale mixing originates negative turbulent diffusion, which produces a mixture resegregation and the appearance of lean pockets far from the oxidizer injection plane. Gradient models display poor capabilities for the prediction of this sort of phenomena. Closure models for the turbulent mixing transport terms are proposed and evaluated. An anisotropic gradient model is devised, providing performance improvements within the recess cavity and the recirculation region. In addition, a novel filtered Reynolds-averaged Navier Stokes approach based on the mixing state is proposed. This new methodology shows excellent prediction capabilities in the regions dominated by KHI, accurately predicting negative turbulent diffusivity. The challenges associated with this model are commented on, and strategies to enable its application are proposed.

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Section: Introductionmentioning

confidence: 99%

Analysis of turbulent mixing in a methane–oxygen recessed injector for space propulsion

2023

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Impacts of hydrocarbons impurities on heat transfer deterioration

Nasser,

Martinez-Sanchis,

Haidn

et al. 2024

Applied Thermal Engineering

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Effects of injection recess in methane turbulent combustion for space propulsion

Martinez-Sanchis,

Sternin,

Haidn

et al. 2024

Physics of Fluids

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Direct numerical simulations (DNS) are conducted to analyze the effect of recess in the mixing and combustion performance of gaseous methane—oxygen injection systems. The recess length is varied from 0 to 2 injector diameters to analyze the sensitivity of various physical processes to this geometrical feature. It is found that the injection recess enhances the development of Kelvin–Helmholtz instabilities (KHI), due to the more consistent jet flow disposition at the injection plane, and the higher velocities. A Strouhal number StrR≈0.22, based on the injector diameter and on the average reacting jet velocity is found for all simulations. In addition, it is found that the enhancement of KHI acts as an injection of turbulent kinetic energy in the large scales, improving macroscale mixing and combustion performance. Finally, the normalized enhancements in combustion performance and averaged hydroxyl emissivity are found to be in good agreement with experimental results in a similar setup.

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Mixture fraction statistics in methane-oxygen turbulent combustion for space propulsion

Cited by 3 publications

References 28 publications

Analysis of turbulent mixing in a methane–oxygen recessed injector for space propulsion

Analysis of turbulent mixing in a methane–oxygen recessed injector for space propulsion

Impacts of hydrocarbons impurities on heat transfer deterioration

Effects of injection recess in methane turbulent combustion for space propulsion

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