CFD Simulation of Confined Non-Premixed Flames

2012 ◽  
Author(s):  
Tanaji M. Dabade ◽  
Xianchang Li ◽  
Daniel Chen ◽  
Helen Lou ◽  
Christopher Martin ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Flame Structure ◽  
Combustion Process ◽  
Premixed Combustion ◽  
Flame Height ◽  
Combustion Model ◽  
Ansys Fluent ◽  
Innovative Strategies ◽  
Precise Control ◽  
Fuel Jet

Material processing furnaces are the key component of the manufacturing industries. The burners used in these furnaces require precise control over the flame structure such as flame shape, height, and width. This study mainly focused on the simulation of the flame structure with Computational Fluid Dynamics (CFD) approach. ANSYS Fluent 13.0 was used to predict the flame characteristics in an enclosed cylinder. Non-premixed combustion model was applied to this combustion phenomenon. To control the flame structure, a micro jet at the centre of the burner is introduced. The effect on flame parameters with varying flow rates of micro jet, fuel jet and co-flow jet is examined. This study confirms the experimental study by Sinha et al. [1], which concluded that an air micro jet at the center of a non-premixed flame can control the flame height and luminosity. Moreover, this paper visualizes the thermo chemistry and transport phenomenon of non-premixed combustion process. Emissions from the combustion are monitored for different boundary conditions. This study shows that innovative strategies can be developed for the precise control over the different types of flames with the help of numerical modeling.

scholarly journals Influence of the chemical mechanism in the frame of diesel-like CFD reacting spray simulations using a presumed PDF flamelet-based combustion model

2017 ◽  
Author(s):  
Eduardo Javier Pérez-Sánchez ◽  
Francisco Payri ◽  
José María García-Oliver ◽  
Ricardo Novella
Keyword(s):  
Cfd Simulation ◽  
Flame Structure ◽  
Research Work ◽  
Combustion Process ◽  
Chemical Mechanism ◽  
Combustion Model ◽  
Key Species ◽  
Spatial Coordinates ◽  
Lift Off ◽  
Presumed Pdf

The ability of a computational fluid dynamics (CFD) simulation to reproduce the diesel-like reacting spray ignitionprocess and its corresponding flame structure strongly depends on both the fidelity of the chemical mechanismfor reproducing the oxidation of the fuel and also on how the turbulence-chemistry interaction (TCI) is modeled.Therefore, investigating the performance of different chemical mechanisms not only in perfect stirred reactors butdirectly in the diesel-like spray itself is of great interest in order to evaluate their suitability for being further appliedto CFD engine simulations.This research work focuses on applying a presumed probability density function (PDF) unsteady flamelet combustionmodel to the well-known spray A from the Engine Combustion Network (ECN), using three chemical mechanismswidely accepted by the scientific community as a way to figure out the influence of chemistry in the keycharacteristics of the combustion process in the frame of diesel-like spray simulations. Results confirm that in spiteof providing all of them correct trends for ignition delays (ID) and lift-off lengths (LOL), when comparing with experimentalresults, the structure of the flame presents noticeable differences, especially in the low and intermediatetemperatures and high equivalence ratio regions. Consequently, the selection of the chemical mechanism has animpact on the zones of influence of key species as observed in both spatial coordinates and also in the equivalenceratio-temperature maps. These differences are expected to be relevant considering the implications when couplingpollutant emissions models. The analysis of temperature and oxygen concentration parametric studies evidenceshow the observed differences are consistent and moderately dependent on the ambient conditions.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4746

CFD Simulation of a Hydrogen Reformer Furnace

2010 ◽  
Author(s):  
Dezhi Zheng ◽  
Bin Wu ◽  
Jeff Fleitz ◽  
Robert Trajkovski ◽  
Chenn Q. Zhou
Keyword(s):  
Flue Gas ◽  
Hot Spots ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Combustion Process ◽  
Premature Aging ◽  
Premixed Combustion ◽  
Combustion Model ◽  
Design Requirement ◽  
Chemical Systems

A hydrogen reformer furnace is a combustion chamber which is used to supply heat for the catalytic process that converts natural gas into hydrogen. The reforming reaction that happens inside the catalyst tubes is endothermic, requiring high levels of heat input. The combustion process in the hydrogen reformer furnace provides the heat to maintain the chemical reaction inside the catalyst tubes. Temperature control of the catalyst tubes is a fundamental design requirement of the hydrogen reformer furnace, as the temperature should be maintained in the range which could maximize catalyst reactivity while minimizing any damage to the catalyst pipes. As the furnace has two complicated chemical systems, the heat effect inside the tubes has been simplified by estimating the heat flux based on industry operation. Utilizing the multiphase and non-premixed combustion model using CFD (Computational Fluid Dynamic), the temperature and velocity distribution in the hydrogen reformer furnace have been investigated. Results show that parts of the catalyst tubes are overheated causing hot spots which could lead to premature aging of the pipes. Both the location of burners and maldistribution of the hot flue gas have a great impact on this issue.

scholarly journals Influence of Eddy-Generation Mechanism on the Characteristic of On-Source Fire Whirl

2019 ◽  
Vol 9 (19) ◽  
pp. 3989 ◽  
Author(s):  
Cheng Wang ◽  
Anthony Chun Yin Yuen ◽  
Qing Nian Chan ◽  
Timothy Bo Yuan Chen ◽  
Qian Chen ◽  
...  
Keyword(s):  
Flame Structure ◽  
Flame Temperature ◽  
Combustion Process ◽  
Flame Height ◽  
Reacting Flow ◽  
Detailed Chemistry ◽  
Eddy Generation ◽  
Fire Whirl ◽  
Generation Mechanisms ◽  
The Impact

This paper numerically examines the characterisation of fire whirl formulated under various entrainment conditions in an enclosed configuration. The numerical framework, integrating large eddy simulation and detailed chemistry, is constructed to assess the whirling flame behaviours. The proposed model constraints the convoluted coupling effects, e.g., the interrelation between combustion, flow dynamics and radiative feedback, thus focuses on assessing the impact on flame structure and flow behaviour solely attribute to the eddy-generation mechanisms. The baseline model is validated well against the experimental data. The data of the comparison case, with the introduction of additional flow channelling slit, is subsequently generated for comparison. The result suggests that, with the intensified circulation, the generated fire whirl increased by 9.42 % in peak flame temperature, 84.38 % in visible flame height, 6.81 % in axial velocity, and 46.14 % in velocity dominant region. The fire whirl core radius of the comparison case was well constrained within all monitored heights, whereas that of the baseline tended to disperse at 0.5   m height-above-burner. This study demonstrates that amplified eddy generation via the additional flow channelling slit enhances the mixing of all reactant species and intensifies the combustion process, resulting in an elongated and converging whirling core of the reacting flow.

Development and Validation of an Ignition Model for SI Engines

2006 ◽  
Author(s):  
Stefania Falfari ◽  
Gian Marco Bianchi
Keyword(s):  
Cfd Simulation ◽  
Combustion Process ◽  
Three Dimensional ◽  
Electrical Energy ◽  
Combustion Model ◽  
Test Case ◽  
Ignition Process ◽  
Mean Flow ◽  
Flame Kernel ◽  
Si Engines

In SI engines the ignition process strongly affects the combustion process. Its accurate modelling becomes a key issue for a design-oriented CFD simulation of the combustion process. Different approaches to simulate ignition have been proposed. The common base is decoupling the physics related to the very first ignition phase when a plasma is formed from that of the development of the flame kernel. The critical point of ignition models is related to the capability of representing the effect of ignition system characteristics, the criterion used for flame deposit and the initialisation of the combustion model. This paper aims to present and validates extensively an ignition model suited for CFD calculation of premixed combustion. The ignition model implemented in a customized version of the Kiva 3 code is coupled with ECFM Flamelet combustion model. The ignition model simulates the plasma/kernel expansion based on a lump evaluation of main ignition processes (i.e., breakdown, arc-phase and glow phase). A double switch criterion based on physical and numerical consideration is used to switch to the main combustion model. The Herweg and Maly experimental test case has been used to check the model capability. In particular, two different ignition systems having different amount of electrical energy released during spark discharge are considered. Comparisons with experimental results allowed testing the model with respect to its capability to reproduce the effects of mixture equivalence ratio, mean flow, turbulence and spark energy on flame kernel development as never done before in three-dimensional RANS CFD combustion modelling of premixed flames.

Aspect Ratio Effects of Elliptic Co-Flow on Turbulent Jet Flame Structures

2002 ◽  
Author(s):  
Ahsan R. Choudhuri ◽  
Sayela P. Luna ◽  
S. R. Gollahalli
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Flame Structure ◽  
Major Axis ◽  
Combustion Characteristics ◽  
Flame Height ◽  
Pollutant Emission ◽  
Jet Flame ◽  
Fuel Jet ◽  
Emission Flame

The aspect ratio effects of elliptic co-flow on the structure of a turbulent propane diffusion flame from a circular tube have been presented. Pollutant emission, flame radiation, flame structure, and soot concentration have been measured. The fuel jet exit Reynolds number is 2700, and the exit Reynolds number for the co-flow is 4010 and 8025 based on the minor and major axis respectively. The results are compared with the measurements from the experiments in a circular co-flow, which is the baseline condition for the present study. The pollution characteristics and the structure of the flame in the elliptic co-flow are significantly different from those in the circular co-flow. The NO emission is higher and the CO emission is lower in the elliptic co-flow. Elliptic co-flow flame produces less soot than circular co-flow flame. The study shows that the elliptic co-flow aspect ratio has a controlling influence on various combustion characteristics. In general, it is seen that as the aspect ratio of the elliptic co-flow is increased from 2:1 to 4:1, the entrainment of air increases and thus the combustion characteristics are enhanced. Compared to 2:1 AR co-flow flames, the flames with 4:1 AR co-flow are more stable, have a lower flame height, produce more NO and less CO, the flame peak temperature is higher, are less sooty, and radiate less. Flame spectral measurements show that the 4:1 aspect ratio flames produce more OH, CH, C2 and H2O radicals in the near-burner region than the 2:1 co-flow flames as a result of higher fuel oxidation.

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.

Analysis of Flame Characteristic of Kerosene Pool Fire

2014 ◽  
Vol 875-877 ◽  
pp. 828-834 ◽  
Author(s):  
Guang Mei Shi ◽  
Ming Hai Li ◽  
Shao Quan Hu ◽  
Zhong Li Zhang
Keyword(s):  
Cfd Simulation ◽  
Flame Temperature ◽  
Simulation Software ◽  
Pool Fire ◽  
Flame Height ◽  
Hazard Evaluation ◽  
Combustion Model ◽  
Discrete Ordinates ◽  
Flow Equations ◽  
Fire Scenarios

Based on the computational fluid dynamics (CFD) simulation software and its parallel techniques, the standard k-ε turbulent flow equations with additional buoyancy-modified, the PDF(Probability Density Function) non-premixed combustion model, and the discrete ordinates (DO) radiation model were used to simulate the kerosene pool fire scenarios of various pool diameters in stagnant air and in a cross-wind. Based on these simulations, the relationships between the pool size and the flame height and flame temperature were obtained, as well as the effective law of the wind speed change on the fire tilt angle. The results presented in this paper are of great significance in the hazard evaluation of the thermal radiation of the pool fire.

A Comparative Study of Combustion Models for Spark Ignition Engines Based on Experimentation and CFD Simulation

2010 ◽  
Author(s):  
Raouf Mobasheri ◽  
M. Sadegh Shahrokhi-Dehkordi
Keyword(s):  
Comparative Study ◽  
Cfd Simulation ◽  
Combustion Process ◽  
Experimental Tests ◽  
Experimental Results ◽  
Nox Emission ◽  
Combustion Model ◽  
Spark Ignition Engines ◽  
Flamelet Model ◽  
Combustion Models

Computational fluid dynamics (CFD) is able to significantly reduce the number of experimental tests and measurements and lower the development time and costs. However some parameters which are needed for CFD calculation must be achieved experimentally. In this paper, a comparative study was carried out to clarify the effect of three different combustion models on the prediction capability of combustion process and NOx emission on a modified 4-cylinder MPFI SI engine. Validation of the combustion model has been performed through comparing simulation data with the experimental results and a satisfactory agreement between them has been achieved in terms of combustion parameters and NOx emission. The results show that, applying appropriate constants of each combustion model including Eddy break up model (Ebu), Probability density function (Pdf) and Coherent flamelet model (Cfm) causes the computational results to be in agreement with experimental results. Furthermore the results show that the nearest prediction in comparison with experimental results is by applying the Ebu model.

CFD Modeling of Flame Structures in a Gas Turbine Combustion Reactor: Velocity, Temperature, and Species Distribution

2017 ◽  
Vol 15 (4) ◽  
Author(s):  
Alireza Bahramian ◽  
Mozhdeh Maleki ◽  
Bijan Medi
Keyword(s):  
Temperature Profile ◽  
Gas Turbine ◽  
Cfd Simulation ◽  
Flame Structure ◽  
Combustion Process ◽  
Three Dimensional ◽  
Species Distributions ◽  
Kinetic Mechanism ◽  
Cfd Modeling ◽  
Laser Measurements

Abstract This paper presents the computational fluid dynamics (CFD) simulation of a gas turbine combustor with methane-air fuel at atmospheric pressure. The velocity fields, temperature profile and species distributions have been numerically studied. The mathematical combustion models, namely Eddy Dissipation Concept (EDC) model coupled with detailed kinetic mechanism, and Finite Rate/Eddy Dissipation (FR-ED) model coupled with a simple global kinetic mechanism, have been used in numerical analysis considering a two-step oxy-combustion reaction kinetics model. Moreover, a series of CFD results with consideration of EDC model have been obtained by two- and three-dimensional simulations. An error analysis showed that the 3-D simulation with EDC model can accurately predict the velocity components, temperature profile, and species distributions of the combustion process and allow detailed investigation of the flame structure. The CFD results are in agreement with the experimental data obtained from laser measurements.

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