Comprehensive numerical study of molecular diffusion effects and Eddy Dissipation Concept model in MILD combustion

2021 ◽  
Vol 46 (13) ◽  
pp. 9252-9265
Author(s):  
Amiratabak Azarinia ◽  
Hossein Mahdavy-Moghaddam
Keyword(s):  
Molecular Diffusion ◽  
Numerical Study ◽  
Concept Model ◽  
Mild Combustion ◽  
Diffusion Effects

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.

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.

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.

Numerical study of H 2 O addition effects on pulverized coal oxy-MILD combustion

2015 ◽  
Vol 138 ◽  
pp. 252-262 ◽  
Author(s):  
Yaojie Tu ◽  
Hao Liu ◽  
Kai Su ◽  
Sheng Chen ◽  
Zhaohui Liu ◽  
...  
Keyword(s):  
Numerical Study ◽  
Pulverized Coal ◽  
Mild Combustion

scholarly journals Assessment of chemical mechanism and chemical reaction sensitivity analysis for CH4/H2 flame under mild combustion environment

2020 ◽  
Vol 24 (3 Part B) ◽  
pp. 2101-2111
Author(s):  
Zhao Yang ◽  
Xiangsheng Li ◽  
Zhenlin Wang ◽  
Zhuangqi Wang
Keyword(s):  
Stokes Equations ◽  
Chemical Mechanism ◽  
Navier Stokes ◽  
Low Oxygen ◽  
Navier Stokes Equations ◽  
Chemical Mechanisms ◽  
Concept Model ◽  
Mild Combustion ◽  
Fluent Software ◽  
Combustion Environment

To analyze the performance of different chemical mechanisms on the prediction under moderate and intense low-oxygen dilution combustion environment, six different kinds of mechanisms were tested by solving the Reynolds averaged Navier- Stokes equations in a 2-D domain with the eddy dissipation concept model by FLUENT software. Temperature and the species concentration of OH, CO, and H2O were compared with the experiment data. The experiment results showed some similarities for each chemical mechanism as well as discrepancies. The comparison of CH4 oxidation route between the GRI2.11 and GRI3.0 mechanisms was made by Chemkin code. Reaction 95 and 147 were responsible for low temperature region for GRI2.11 mechanism at downstream area.

A Numerical Study of Turbulent Flow in Helical Static Mixers

2006 ◽  
Author(s):  
Ramin K. Rahmani ◽  
Anahita Ayasoufi ◽  
Theo G. Keith
Keyword(s):  
Turbulent Flow ◽  
Molecular Diffusion ◽  
Stokes Equations ◽  
Numerical Study ◽  
Critical Role ◽  
Three Dimensional ◽  
Turbulent Dispersion ◽  
Working Fluid ◽  
Static Mixer ◽  
Static Mixers

Many processing applications call for the addition of small quantities of chemicals to working fluid. Hence, fluid mixing plays a critical role in the success or failure of these processes. An optimal combination of turbulent dispersion down to eddies of the Kolmogoroff scale and molecular diffusion would yield fast mixing on a molecular scale which in turn favors the desired reactions. Helical static mixers can be used for those applications. The range of practical flow Reynolds numbers for these mixers in industry is usually from very small (Re ∼ 0) to moderate values (Re ∼ 5000). In this study, a helical static mixer is investigated numerically using Lagrangian methods to characterize mixer performance under turbulent flow regime conditions. A numerical simulation of turbulent flows in helical static mixers is employed. The model solves the three-dimensional, Reynolds-averaged Navier-Stokes equations, closed with the Spalart-Allmaras turbulence model, using a second-order-accurate finite-volume numerical method. Numerical simulations are carried out for a six-element mixer, and the computed results are analyzed to elucidate the complex, three-dimensional features of the flow. Using a variety of predictive tools, mixing results are obtained and the performance of static mixer under turbulent flow condition is studied.

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