Numerical study of influence of molecular diffusion in the Mild combustion regime

2010 ◽  
Vol 14 (5) ◽  
pp. 747-774 ◽  
Author(s):  
Amir Mardani ◽  
Sadegh Tabejamaat ◽  
Mohsen Ghamari
Keyword(s):  
Molecular Diffusion ◽  
Numerical Study ◽  
Combustion Regime ◽  
Mild Combustion

scholarly journals Numerical study of flame structure in the mild combustion regime

2015 ◽  
Vol 19 (1) ◽  
pp. 21-34 ◽  
Author(s):  
Amir Mardani ◽  
Sadegh Tabejamaat
Keyword(s):  
Fuel Injection ◽  
Numerical Study ◽  
Flame Structure ◽  
Combustion Regime ◽  
Low Oxygen ◽  
Mixing Rate ◽  
Jet Flame ◽  
Reduced Mechanism ◽  
Mild Combustion ◽  
O2 Concentration

In this paper, turbulent non-premixed CH4+H2 jet flame issuing into a hot and diluted co-flow air is studied numerically. This flame is under condition of the moderate or intense low-oxygen dilution (MILD) combustion regime and related to published experimental data. The modelling is carried out using the EDC model to describe turbulence-chemistry interaction. The DRM-22 reduced mechanism and the GRI2.11 full mechanism are used to represent the chemical reactions of H2/methane jet flame. The flame structure for various O2 levels and jet Reynolds numbers are investigated. The results show that the flame entrainment increases by a decrease in O2 concentration at air side or jet Reynolds number. Local extinction is seen in the upstream and close to the fuel injection nozzle at the shear layer. It leads to the higher flame entertainment in MILD regime. The turbulence kinetic energy decay at centre line of jet decreases by an increase in O2 concentration at hot Co-flow. Also, increase in jet Reynolds or O2 level increases the mixing rate and rate of reactions.

Numerical study of the effect of turbulence on rate of reactions in the MILD combustion regime

2011 ◽  
Vol 15 (6) ◽  
pp. 753-772 ◽  
Author(s):  
Amir Mardani ◽  
Sadegh Tabejamaat ◽  
Mohammadreza Baig Mohammadi
Keyword(s):  
Numerical Study ◽  
Combustion Regime ◽  
Mild Combustion

Effects of hydrogen addition on structure and NO formation of highly CO-Rich syngas counterflow nonpremixed flames under MILD combustion regime

2021 ◽  
Vol 46 (17) ◽  
pp. 10518-10534
Author(s):  
Namsu Kim ◽  
Yongmo Kim ◽  
Mohammad Nazri Mohd Jaafar ◽  
Muhammad Roslan Rahim ◽  
Mazlan Said
Keyword(s):  
Combustion Regime ◽  
Nonpremixed Flames ◽  
Hydrogen Addition ◽  
No Formation ◽  
Mild Combustion

scholarly journals Numerical study of hydrogen mild combustion

2009 ◽  
Vol 13 (3) ◽  
pp. 59-67 ◽  
Author(s):  
Enrico Mollica ◽  
Eugenio Giacomazzi ◽  
Marco di
Keyword(s):  
Numerical Study ◽  
Fluid Dynamic ◽  
Thermal Gradients ◽  
Radiation Model ◽  
Dynamic Simulations ◽  
Mild Combustion ◽  
Preheating Temperature ◽  
Nitric Oxide Emissions ◽  
Gas Recirculation ◽  
Good Agreement

In this article a combustor burning hydrogen and air in mild regime is numerically studied by means of computational fluid dynamic simulations. All the numerical results show a good agreement with experimental data. It is seen that the flow configuration is characterized by strong exhaust gas recirculation with high air preheating temperature. As a consequence, the reaction zone is found to be characteristically broad and the temperature and concentrations fields are sufficiently homogeneous and uniform, leading to a strong abatement of nitric oxide emissions. It is also observed that the reduction of thermal gradients is achieved mainly through the extension of combustion in the whole volume of the combustion chamber, so that a flame front no longer exists ('flameless oxidation'). The effect of preheating, further dilution provided by inner recirculation and of radiation model for the present hydrogen/air mild burner are analyzed.

The Role of the Recirculating Gases at the Mild Combustion Regime Formation

2007 ◽  
Author(s):  
Y. Levy ◽  
V. Sherbaum ◽  
V. Erenburg
Keyword(s):  
Gas Turbine ◽  
Ignition Delay ◽  
Ignition Delay Time ◽  
Combustion Process ◽  
Combustion Regime ◽  
Reaction Products ◽  
Gas Turbine Combustor ◽  
Mild Combustion ◽  
Recirculation Rate ◽  
Co Emission

The present work is concerned with the thermodynamic and chemical kinetics of gas turbine combustor operating in the Moderate or Intense Low-oxygen Dilution (MILD) combustion regime. The objective of the present study is to evaluate analytically the effect of the recirculation rate of combustion products within the FLOXCOM gas turbine combustor on a number of combustion parameters, mainly on the ignition delay time, NOx and CO emission, minimum ignition temperature, rate of pollutant formation and the dilution rate. The study also refers to the mechanism of influence of the recirculation rate on these values. Combustion pressure and inlet air temperature are used as parameters. The gas turbine is fueled with methane. The analysis is mainly based on CHEMKIN simulations where the calculation scheme of the combustion process in the combustor is modeled by a combination of plug reactors and mixers. Due to the unique characteristics of gas turbines, inlet air temperature is directly linked to combustion pressure while assuming conventional adiabatic compression efficiencies. It is shown that free radicals, which are part of the reaction products and exists for only a short period of time within the recirculated gases, decrease ignition delay time. The importance of shortening the ignition delay is further highlighted because of the adverse effect oxygen dilution has on this parameter (dilution of the reactants by the reaction products). It was found that there is an optimal recirculation rate, which corresponds to maximum heat density. In addition, results indicate that CO emission values rise with the recirculation rate, however the NOX values are more complicated. NOX depends on recirculation rate when flame temperatures are kept held constant. The NOX emission increases and the CO emission decreases with compressor pressure ratio. The CO concentration that is evaluated in the combustion process is further reduced during last dilution stage. Finally, basic rules for design optimization of the combustor are drafted. These are based on conventional one-dimensional fluid and thermodynamic relations and on the CHEMKIN simulations.

Numerical study on a novel burner designed to improve MILD combustion behaviors at the oxygen enriched condition

2019 ◽  
Vol 152 ◽  
pp. 686-696 ◽  
Author(s):  
Yihao Xie ◽  
Yaojie Tu ◽  
Hu Jin ◽  
Congcong Luan ◽  
Zean Wang ◽  
...  
Keyword(s):  
Numerical Study ◽  
Mild Combustion ◽  
Combustion Behaviors

Numerical Study of Mass Dispersion in Laminar and Turbulent Flows Through a Pipeline

2002 ◽  
Author(s):  
Horacio Antonio Flo´rez Guzma´n
Keyword(s):  
Turbulent Flows ◽  
Molecular Diffusion ◽  
Numerical Study ◽  
Computer Code ◽  
Finite Difference Schemes ◽  
Entire Volume ◽  
Two Fluids ◽  
Mass Dispersion ◽  
Miscible Fluid ◽  
Domain Discretization

A computer code for solving the equations of mass diffusion has been developed and applied to study the molecular-level mixing between two fluids inside a pipe. First, one fluid occupies the entire volume within the pipe, and then a second miscible fluid is forced into the pipe, developing a mixing process through the interface between the fluids. This phenomenon occurs as the combination of molecular diffusion, variation of velocity over the cross-section and turbulence. The code developed for this study is based on the finite element method for domain discretization and standard finite difference schemes for temporal discretization. Comparison with experimental data shows that the code is able to reproduce the physical trends and gives good predictions for engineering applications. A grid independence analysis is presented for all computations.

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