Effect of Bluff-Body Shape on Stability of Hydrogen-Air Flame in Narrow Channel (original) (raw)
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Annales de Chimie - Science des Matériaux, 2021
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Gas turbines are expected to play a key role in the energy production scenario in the future, and the introduction of carbon-free fuels is fundamental for the development of a sustainable energy mix. The development of a reliable numerical model is thus fundamental in order to support the design changes required for the burners. This paper presents the results of a numerical investigation on a turbulent, diffusive, combustion test case, with the purpose of identifying the best compromise between accuracy and computational cost, in the perspective of the model application in real, more complex, geometries. Referring to a test case has two main advantages. First, a rather simple geometry can be considered, still retaining a few peculiar flow features, such as recirculation vortices and shear layers, which are typical of real applications. Second, the experimental setup is much more detailed than in the case of real turbines, allowing a thorough model validation to be performed. In thi...
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Experimental measurements of the temperature and chemical species mass concentrations are compared with predictions made by a commercial Computational Fluid Dynamics (CFD) package. The bluff body burner considered for this study is included in the library of test flames of the International Workshop on Measurement and Computation of Turbulent Non-premixed Flames (TNF). The unmixed bluff-body stabilised flame burner, which is representative of industrial designs, using a fuel of 1:1 volume ratio of methane and hydrogen was chosen. Four k-ε based turbulence models are examined. Four combustion models; the Eddy Break-Up model, the Adiabatic and Non-adiabatic Presumed Probability Density Function (PPDF) model, and the Laminar Flamelet model are studied. The benefits of the Laminar Flamelet model are illustrated with excellent results being obtained when it is used in conjunction with the Chen k-ε turbulence model. A detailed analysis comparing the merits of each of the modelling approaches is presented.
Stability Characteristics of a Turbulent Nonpremixed Conical Bluff Body Flame
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The thermal characteristics of turbulent non-premixed methane flames were investigated by four burner heads with the same exit diameter but different heights. The fuel flow rate was kept constant with an exit velocity of 15 m/s, while the co-flow air speed was increased from 0 to 7.6 m/s. The radial profiles of the temperature and flame visualizations were obtained to investigate the stability limits. The results evidenced that the air co-flow and the cone angle have essential roles in the stabilization of the flame: An increase in the cone angle and/or the co-flow speed deteriorated the stability of the flame, which eventually tended to blow off. As the cone angle was reduced, the flame was attached to the bluff body. However, when the cone angle is very small, it has no effect on stability. The mixing and entrainment processes were described by the statistical moments of the temperature fluctuations. It appears that the rise in temperature coincides with the intensified mixing, an...
Large Eddy Simulation of Bluff Body Stabilized Turbulent Premixed Flame
AbstrAct: A turbulent reacting flow in a channel with an obstacle was simulated computationally with large eddy simulation turbulence modeling and the Xi turbulent combustion model for premixed flame. The numerical model was implemented in the open source software OpenFoam. Both inert flow and reactive flow simulations were performed. In the inert flow, comparisons with velocity profile and recirculation vortex zone were performed as well as an analysis of the energy spectrum obtained numerically. The simulation with reacting flow considered a pre-mixture of propane (C 3 H 8) and air such that the equivalence ratio was equal to 0.65, with a theoretical adiabatic flame temperature of 1,800 K. The computational results were compared to experimental ones available in the literature. The equivalence ratio, inlet flow velocity, pressure, flame-holder shape and size, fuel type and turbulence intensity were taken from an experimental set up. The results shown in the present simulations are in good agreement with the experimental data.
47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, 2009
grids. Simulations with fine grids were able to predict the recirculation zone thickness correctly as observed in the experiments. Simulation results also show that the near-field wake behind the bluff body was dominated by the Von-Karman vortex shedding for the nonreacting case as well as the reacting case with EDC models, while a shear layer generated vortex sheet was observed for reacting flow cases with the LC models. The simulation results demonstrate that turbulence-chemistry interactions play a major role in predicting the blow-out conditions. LES predictions with the EDC model show that the blow-out occurs at 0.6 equivalence ratio as observed experimentally at a DeZubay number of ~10.
Calculations of a Turbulent Bluff-Body Stabilized Flame
The Joint velocity-turbulent frequency-composition Probability Density Function (JPDF) method implemented in a hybrid Finite Volume (FV)/particle algorithm is applied to a bluff-body stabilized flame. The in situ adaptive tabulation (ISAT) method is used to implement methane chemistry using an Augmented Reduced Mechanism (ARM). Numerically accurate results are obtained. Comparisons with experimental data are shown for: profiles of the mean and r.m.s. of mixture fraction; profiles of temperature and mean species mass fractions; and scatter plots of species mass fraction against mixture fraction. The JPDF calculations are in reasonable agreement with the experimental data.