scholarly journals A numerical study of turbulent flame speeds of curvature and strain G-equations in cellular flows

2013 ◽  
Vol 243 (1) ◽  
pp. 20-31 ◽  
Author(s):  
Yu-Yu Liu ◽  
Jack Xin ◽  
Yifeng Yu
Keyword(s):  
Numerical Study ◽  
Turbulent Flame ◽  
Cellular Flows

scholarly journals Numerical Study of a Turbulent Burner by Means of RANS and Detailed Chemistry

2019 ◽  
Vol 3 (2) ◽  
pp. 34
Author(s):  
Mohamed Hafid
Keyword(s):  
Schmidt Number ◽  
Numerical Study ◽  
Turbulent Flame ◽  
Navier Stokes ◽  
Turbulent Dissipation ◽  
Detailed Chemistry ◽  
Turbulent Schmidt Number ◽  
Complex Models ◽  
Pdf Model ◽  
Probability Density Function Pdf

The present paper shows a numerical study of the Co-flow turbulent flame configuration using the Reynolds Averaged Navier-Stokes (RANS) modelling with detailed chemistry. The presumed Probability Density Function (PDF) model combined with the k-Ɛ turbulence model is adopted. The GRI Mech-3.0 mechanism that involves 53 species and 325 reactions is used. The effect of the turbulent Schmidt number Sct and the C1ε constant in the turbulent dissipation transport equation is highlighted. Despite the simplicity of RANS approach compared to other complex models such as LES and DNS, the results show that this approach is still able to simulate the turbulent flame.

scholarly journals Numerical study of turbulent normal diffusion flame CH4-air stabilized by coaxial burner

2013 ◽  
Vol 17 (4) ◽  
pp. 1207-1219 ◽  
Author(s):  
Zouhair Riahi ◽  
Ali Mergheni ◽  
Jean-Charles Sautet ◽  
Ben Nasrallah
Keyword(s):  
Equivalence Ratio ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Turbulent Flame ◽  
Flame Structure ◽  
Premixed Combustion ◽  
Air Jet ◽  
Fuel Jet ◽  
Jet Velocity ◽  
Lift Off

The practical combustion systems such as combustion furnaces, gas turbine, engines, etc. employ non-premixed combustion due to its better flame stability, safety, and wide operating range as compared to premixed combustion. The present numerical study characterizes the turbulent flame of methane-air in a coaxial burner in order to determine the effect of airflow on the distribution of temperature, on gas consumption and on the emission of NOx. The results in this study are obtained by simulation on FLUENT code. The results demonstrate the influence of different parameters on the flame structure, temperature distribution and gas emissions, such as turbulence, fuel jet velocity, air jet velocity, equivalence ratio and mixture fraction. The lift-off height for a fixed fuel jet velocity is observed to increase monotonically with air jet velocity. Temperature and NOx emission decrease of important values with the equivalence ratio, it is maximum about the unity.

scholarly journals Sound generation by turbulent premixed flames

2018 ◽  
Vol 843 ◽  
pp. 29-52 ◽  
Author(s):  
Ali Haghiri ◽  
Mohsen Talei ◽  
Michael J. Brear ◽  
Evatt R. Hawkes
Keyword(s):  
Numerical Study ◽  
Turbulent Flame ◽  
Premixed Flames ◽  
Computational Cost ◽  
Turbulent Flames ◽  
Far Field ◽  
Turbulent Premixed Flames ◽  
Acoustic Sources ◽  
Field Sound ◽  
Turbulent Premixed

This paper presents a numerical study of the sound generated by turbulent, premixed flames. Direct numerical simulations (DNS) of two round jet flames with equivalence ratios of 0.7 and 1.0 are first carried out. Single-step chemistry is employed to reduce the computational cost, and care is taken to resolve both the near and far fields and to avoid noise reflections at the outflow boundaries. Several significant features of these two flames are noted. These include the monopolar nature of the sound from both flames, the stoichiometric flame being significantly louder than the lean flame, the observed frequency of peak acoustic spectral amplitude being consistent with prior experimental studies and the importance of so-called ‘flame annihilation’ events as acoustic sources. A simple model that relates these observed annihilation events to the far-field sound is then proposed, demonstrating a surprisingly high degree of correlation with the far-field sound from the DNS. This model is consistent with earlier works that view a premixed turbulent flame as a distribution of acoustic sources, and provides a physical explanation for the well-known monopolar content of the sound radiated by premixed turbulent flames.

scholarly journals A Numerical Prediction of Stabilized Turbulent Partially Premixed Flames Using Ammonia/Hydrogen Mixture

2021 ◽  
Vol 87 (3) ◽  
pp. 113-133
Author(s):  
Moataz Medhat ◽  
Mohamed Yehia ◽  
Adel Khalil ◽  
Miguel C. Franco ◽  
Rodolfo C. Rocha
Keyword(s):  
Radiation Effects ◽  
Equivalence Ratio ◽  
Numerical Study ◽  
Turbulent Flame ◽  
Clean Energy ◽  
Operating Conditions ◽  
Combustion Model ◽  
Hydrogen Mixture ◽  
Partially Premixed ◽  
No Emissions

The objective of this work is to computationally assess the performance of a carbon free ammonia-hydrogen mixture when burnt in a gas turbine like combustor. Recently, utilizing ammonia as an alternative carbon-free fuel for future power, industry applications and achieving clean energy attracted enormous interest. Pure ammonia oxidation is facing many challenges such as high NOx emissions, high ignition energy, slow reactivity and lower laminar flame speeds. Therefore, the use of ammonia/hydrogen mixture provides flame stability and increasing flame speed. In this manuscript a numerical study for a new swirl stabilized combustor for oxidizing ammonia/hydrogen mixture. Numerical two dimensional model simulations of a turbulent flame on Reynolds Averaged Navier Stokes (RANS) including a realizable k-e turbulent scheme with the aid of chemistry mechanism were performed under various conditions. Partially premixed combustion model with flame-let concept was selected and radiation effects are also considered. Validation for the predicted results showed a reasonable agreement when validated with the experimental data. The results discuss the influence of changing inlet pressure and equivalence ratio on the stability and the characteristics of unburnt NH3 and NO emissions. Results show that for constant operating conditions such as constant equivalence ratio of 0.8 that increasing hydrogen content resulted in increasing NO emission. Also, for constant ammonia/hydrogen concentrations, NO emissions increases with equivalence ratio then reduced at rich conditions and NH3 emissions are generally low. Equivalence ratio lower than 1.2 will be preferable to reduce the amount of unburnt NH3 formation.

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