scholarly journals Numerical Investigation of an OxyfuelNon-Premixed CombustionUsing a Hybrid Eulerian Stochastic Field/Flamelet Progress Variable Approach: Effects of H2/CO2Enrichment and Reynolds Number

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3158 ◽  
Author(s):  
Rihab Mahmoud ◽  
Mehdi Jangi ◽  
Benoit Fiorina ◽  
Michael Pfitzner ◽  
Amsini Sadiki
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Combustion Model ◽  
Stochastic Field ◽  
Suggested Approach ◽  
Jet Flame ◽  
Progress Variable ◽  
Variable Approach ◽  
Novel Approach

In the present paper, the behaviour of an oxy-fuel non-premixed jet flame is numerically investigated by using a novel approach which combines a transported joint scalar probability density function (T-PDF) following the Eulerian Stochastic Field methodology (ESF) and a Flamelet Progress Variable (FPV) turbulent combustion model under consideration of detailed chemical reaction mechanism. This hybrid ESF/FPV approach overcomes the limitations of the presumed- probability density function (P-PDF) based FPV modelling along with the solving of associated additional modelled transport equations while rendering the T-PDF computationally less demanding. In Reynolds Averaged Navier-Stokes (RANS) context, the suggested approach is first validated by assessing its general prediction capability in reproducing the flame and flow properties of a simple piloted jet flame configuration known as Sandia Flame D. Second, its feasibility in capturing CO2addition effect on the flame behaviour is demonstrated while studying a non-premixed oxy-flame configuration. This consists of an oxy-methane flame characterized by a high CO2 amount in the oxidizer and a significant content of H2 in the fuel stream, making it challenging for combustion modelling. Comparisons of numerical results with experimental data show that the complete model reproduces the major properties of the flame cases investigated and allows achieving the best agreement for the temperature and different species mass fractions once compared to the classical presumed PDF approach.

scholarly journals Combustion Characteristics of a Non-Premixed Oxy-Flame Applying a Hybrid Filtered Eulerian Stochastic Field/Flamelet Progress Variable Approach

2019 ◽  
Vol 9 (7) ◽  
pp. 1320 ◽  
Author(s):  
Rihab Mahmoud ◽  
Mehdi Jangi ◽  
Florian Ries ◽  
Benoit Fiorina ◽  
Johannes Janicka ◽  
...  
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Combustion Characteristics ◽  
Combustion Model ◽  
Structure Stability ◽  
Stochastic Field ◽  
Jet Flame ◽  
Progress Variable ◽  
The Impact

The oxidation of methane under oxy-fuel combustion conditions with carbon capture is attractive and deserves huge interest towards reducing CO2 and NOx emissions. The current paper reports on the predictions and analysis of combustion characteristics of a turbulent oxy-methane non-premixed flame operating under highly diluted conditions of CO2 and H2 in oxidizer and fuel streams, respectively. These are achieved by applying a novel, well-designed numerical combustion model. The latter consists of a large eddy simulation (LES) extension of a recently suggested hybrid model in Reynolds averaging-based numerical simulation (RANS) context by the authors. It combines a transported joint scalar probability density function (T-PDF) following the Eulerian Stochastic Field methodology (ESF) on the one hand, and a flamelet progress variable (FPV) turbulent combustion model under consideration of detailed chemical reaction mechanism on the other hand. This novel hybrid ESF/FPV approach removes the weaknesses of the presumed-probability density function (P-PDF)-based FPV modeling, along with the solving of associated additional modeled transport equations while rendering the T-PDF computationally less affordable. First, the prediction capability of the LES hybrid ESF/FPV was appraised on the well-known air-piloted methane jet flame (Sandia Flame D). Then, it was assessed in analyzing the combustion properties of a non-premixed oxy-flame and in capturing the CO2 dilution effect on the oxy-fuel flame behavior. To this end, the so-called oxy-flame B3, already numerically investigated in a RANS context, was analyzed. Comparisons with experimental data in terms of temperature, scalar distributions, and scatter plots agree satisfactorily. Finally, the impact of generating the FPV chemistry table under condition of unity Lewis number, even with CO2 dilution, was investigated on the general prediction of the oxy-fuel flame structure, stability and emissions. In particular, it turns out that 68% molar percentage of CO2 leads to 0.39% of CO formation near the burner fuel nozzle and 0.62% at 10 dfuel above the nozzle.

scholarly journals Analysis and flamelet modelling for spray combustion

2008 ◽  
Vol 612 ◽  
pp. 45-79 ◽  
Author(s):  
YUYA BABA ◽  
RYOICHI KUROSE
Keyword(s):  
Conservation Equation ◽  
Spray Combustion ◽  
Combustion Model ◽  
Flamelet Model ◽  
Jet Flame ◽  
Total Enthalpy ◽  
Progress Variable ◽  
Combustion Models ◽  
Spray Flame ◽  
Variable Approach

The validity of a steady-flamelet model and a flamelet/progress-variable approach for gaseous and spray combustion is investigated by a two-dimensional direct numerical simulation (DNS) of gaseous and spray jet flames, and the combustion characteristics are analysed. A modified flamelet/progress-variable approach, in which total enthalpy rather than product mass fraction is chosen as a progress variable, is also examined. DNS with an Arrhenius formation, in which the chemical reaction is directly solved in the physical flow field, is performed as a reference to validate the combustion models. The results show that the diffusion flame is dominant in the gaseous diffusion jet flame, whereas diffusion and premixed flames coexist in the spray jet flame. The characteristics of the spray flame change from premixed–diffusion coexistent to diffusion-dominant downstream. Comparisons among the results from DNS with various combustion models show the modified flamelet/progress-variable approach to be superior to the other combustion models, particularly for the spray flame. Where the behaviour of the gaseous total enthalpy is strongly affected by the energy transfer (i.e. heat transfer and mass transfer) from the dispersed droplet, and this effect can be accounted for only by solving the conservation equation of the total enthalpy. However, even the DNS with the modified flamelet/progress-variable approach tends to underestimate the gaseous temperature in the central region of the spray jet flame. To increase the prediction accuracy, a combustion model for the partially premixed flame for the spray flame is necessary.

Simulation of the Influence of Air Preheat Combustion on the Temperature of Propane Turbulent Flame Using Probability Density Function Approach and Eddy Dissipation Model

2013 ◽  
Vol 871 ◽  
pp. 95-100
Author(s):  
Elwina ◽  
Yunardi ◽  
Yazid Bindar ◽  
Syukran
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Turbulence Model ◽  
Turbulent Flame ◽  
Flame Temperature ◽  
Temperature Fields ◽  
Combustion Model ◽  
Dissipation Model ◽  
Pdf Model

This paper presents results obtained from the application of a computational fluid dynamics (CFD) code Fluent 6.3 to modelling of temperature in propane flames with air preheat. The study focuses on investigating the effect of air preheat temperature on the temperature of the flame. A standard k-ε turbulence model in combination with the Probability Density Function (PDF) model for Non Premix Combustion model and Eddy Dissipation Model (EDM) are utilized to represent the flow and temperature fields of the flame being investigated, respectively. The results of calculations are compared with experimental data of propane flame taken from literature. The results of the study showed that the combination of the standard k-ε turbulence model and PDF model is more capable of producing reasonable predictions of temperature, particularly in axial profile and rich fuel area of all two flames compared with those of EDM model. Both experimental works and numerical simulation showed that increasing the temperature of the combustion air significantly increases the flame temperature.

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