scholarly journals Data-Driven Combustion Modeling for a Turbulent Flame Simulated With a Computationally Efficient Solver

2020 ◽  
Author(s):  
Mohsen Talei ◽  
Man-Ching Ma ◽  
Richard Sandberg
Keyword(s):  
Surface Density ◽  
Turbulence Modeling ◽  
Gene Expression Programming ◽  
Turbulent Flame ◽  
Reacting Flows ◽  
Flame Surface ◽  
Algebraic Models ◽  
Computationally Efficient ◽  
Flame Surface Density ◽  
Combustion Modeling

Abstract The use of machine learning (ML) for modeling is on the rise. In the age of big data, this technique has shown great potential to describe complex physical phenomena in the form of models. More recently, ML has frequently been used for turbulence modeling while the use of this technique for combustion modeling is still emerging. Gene expression programming (GEP) is one class of ML that can be used as a tool for symbolic regression and thus improve existing algebraic models using high-fidelity data. Direct numerical simulation (DNS) is a powerful candidate for producing the required data for training GEP models and validation. This paper therefore presents a highly efficient DNS solver known as HiPSTAR, originally developed for simulating non-reacting flows in particular in the context of turbo-machinery. This solver has been extended to simulate reacting flows. DNSs of two turbulent premixed jet flames with different Karlovitz numbers are performed to produce the required data for training. GEP is then used to develop algebraic flame surface density models in the context of large-eddy simulation (LES). The result of this work introduces new models which show excellent performance in prediction of the flame surface density for premixed flames featuring different Karlovitz numbers.

scholarly journals Effects of Turbulent Reynolds Number on the Performance of Algebraic Flame Surface Density Models for Large Eddy Simulation in the Thin Reaction Zones Regime: A Direct Numerical Simulation Analysis

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Mohit Katragadda ◽  
Nilanjan Chakraborty ◽  
R. S. Cant
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Fractal Dimension ◽  
Direct Numerical Simulation ◽  
Surface Density ◽  
Flame Surface ◽  
Algebraic Models ◽  
Flame Surface Density ◽  
Turbulent Reynolds Number ◽  
Reaction Zones

A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different turbulent Reynolds numbers has been used to assess the performance of algebraic flame surface density (FSD) models based on a fractal representation of the flame wrinkling factor. The turbulent Reynolds number Rethas been varied by modifying the Karlovitz number Ka and the Damköhler number Da independently of each other in such a way that the flames remain within the thin reaction zones regime. It has been found that the turbulent Reynolds number and the Karlovitz number both have a significant influence on the fractal dimension, which is found to increase with increasing Retand Ka before reaching an asymptotic value for large values of Retand Ka. A parameterisation of the fractal dimension is presented in which the effects of the Reynolds and the Karlovitz numbers are explicitly taken into account. By contrast, the inner cut-off scale normalised by the Zel’dovich flame thicknessηi/δzdoes not exhibit any significant dependence on Retfor the cases considered here. The performance of several algebraic FSD models has been assessed based on various criteria. Most of the algebraic models show a deterioration in performance with increasing the LES filter width.

Development of a RANS Premixed Turbulent Combustion Model Based on the Algebraic Flame Surface Density Concept

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Usman Allauddin ◽  
Michael Pfitzner
Keyword(s):  
Experimental Data ◽  
Surface Density ◽  
Turbulent Flame ◽  
Theoretical Models ◽  
Elevated Pressure ◽  
Navier Stokes ◽  
Combustion Model ◽  
Flame Surface ◽  
Flame Surface Density ◽  
Premixed Turbulent Combustion

Recently, a fractal-based algebraic flame surface density (FSD) premixed combustion model has been derived and validated in the context of large eddy simulation (LES). The fractal parameters in the model, namely the cut-off scales and the fractal dimension were derived using theoretical models, experimental and direct numerical simulation (DNS) databases. The model showed good performance in predicting the premixed turbulent flame propagation for low to high Reynold numbers (Re) in ambient as well as elevated pressure conditions. Several LES combustion models have a direct counterpart in the Reynolds-averaged Navier–Stokes (RANS) context. In this work, a RANS version of the aforementioned LES subgrid scale FSD combustion model is developed. The performance of the RANS model is compared with that of the original LES model and validated with the experimental data. It is found that the RANS version of the model shows similarly good agreement with the experimental data.

scholarly journals The evolution equation for the flame surface density in turbulent premixed combustion

1994 ◽  
Vol 278 ◽  
pp. 1-31 ◽  
Author(s):  
Arnaud Trouvé ◽  
Thierry Poinsot
Keyword(s):  
Evolution Equation ◽  
Flame Propagation ◽  
Surface Density ◽  
Turbulent Flame ◽  
Premixed Combustion ◽  
Flame Surface ◽  
Turbulent Premixed Combustion ◽  
Flame Surface Density ◽  
Propagation Effects ◽  
Turbulent Premixed

One basic effect of turbulence in turbulent premixed combustion is for the fluctuating velocity field to wrinkle the flame and greatly increase its surface area. In the flamelet theory, this effect is described by the flame surface density. An exact evolution equation for the flame surface density, called the Σ-equation, may be written, where basic physical mechanisms like production by hydrodynamic straining and destruction by propagation effects are described explicitly. Direct numerical simulation (DNS) is used in this paper to estimate the different terms appearing in the Σ-equation. The numerical configuration corresponds to three-dimensional premixed flames in isotropic turbulent flow. The simulations are performed for various mixture Lewis numbers in order to modify the strength and nature of the flame-flow coupling. The DNS-based analysis provides much information relevant to flamelet models. In particular, the flame surface density, and the source and sink terms for the flame surface density, are resolved spatially across the turbulent flame brush. The geometry as well as the dynamics of the flame differ quite significantly from one end of the reaction zone to the other. For instance, contrary to the intuitive idea that flame propagation effects merely counteract the wrinkling due to the turbulence, the role of flame propagation is not constant across the turbulent brush and switches from flame surface production at the front to flame surface dissipation at the back. Direct comparisons with flamelet models are also performed. The Bray-Moss-Libby assumption that the flame surface density is proportional to the flamelet crossing frequency, a quantity that can be measured in experiments, is found to be valid. Major uncertainties remain, however, over an appropriate description of the flamelet crossing frequency. In comparison, the coherent flame model of Marble & Broadwell achieves closure at the level of the Σ-equation and provides a more promising physically based description of the flame surface dynamics. Some areas where the model needs improvement are identified.

104 Variation of flame surface density with flame propagation of spherically propagating premixed turbulent flame

2014 ◽  
Vol 2014.67 (0) ◽  
pp. _104-1_-_104-2_
Author(s):  
Tatsuya KAI ◽  
Yotaro WAKABAYASHI ◽  
Taiki TSUKAMOTO ◽  
Akira NOMO ◽  
Yukihide NAGANO ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Surface Density ◽  
Turbulent Flame ◽  
Flame Surface ◽  
Flame Surface Density ◽  
Premixed Turbulent Flame

scholarly journals A PrioriAssessment of Algebraic Flame Surface Density Models in the Context of Large Eddy Simulation for Nonunity Lewis Number Flames in the Thin Reaction Zones Regime

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Mohit Katragadda ◽  
Nilanjan Chakraborty ◽  
R. S. Cant
Keyword(s):  
Surface Density ◽  
Laminar Flame ◽  
Lewis Number ◽  
Algebraic Model ◽  
Flame Surface ◽  
Algebraic Models ◽  
Flame Surface Density ◽  
Eddy Simulation ◽  
Proposed Model ◽  
Reaction Zones

The performance of algebraic flame surface density (FSD) models has been assessed for flames with nonunity Lewis number (Le) in the thin reaction zones regime, using a direct numerical simulation (DNS) database of freely propagating turbulent premixed flames with Le ranging from 0.34 to 1.2. The focus is on algebraic FSD models based on a power-law approach, and the effects of Lewis number on the fractal dimensionDand inner cut-off scaleηihave been studied in detail. It has been found thatDis strongly affected by Lewis number and increases significantly with decreasing Le. By contrast,ηiremains close to the laminar flame thermal thickness for all values of Le considered here. A parameterisation ofDis proposed such that the effects of Lewis number are explicitly accounted for. The new parameterisation is used to propose a new algebraic model for FSD. The performance of the new model is assessed with respect to results for the generalised FSD obtained from explicitly LES-filtered DNS data. It has been found that the performance of the most existing models deteriorates with decreasing Lewis number, while the newly proposed model is found to perform as well or better than the most existing algebraic models for FSD.

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