Interpreting diffusion flame structure by simultaneous mixture fraction and temperature measurements using optical and acoustic signals from laser-induced plasmas

2020 ◽  
Author(s):  
Wendong Wu ◽  
Richard L. Axelbaum
Keyword(s):  
Diffusion Flame ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Acoustic Signals ◽  
Temperature Measurements

Finite Element Volume Analysis of Propane Preheated Air Flame Passing Through a Minichannel

2014 ◽  
Author(s):  
Masoud Darbandi ◽  
Majid Ghafourizadeh ◽  
Gerry E. Schneider
Keyword(s):  
Finite Element ◽  
Radiation Effects ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Current Method ◽  
Reacting Flow ◽  
Wall Functions ◽  
Flamelet Model ◽  
Combustion Modeling ◽  
Detailed Kinetics

A hybrid finite-element-volume FEV method is extended to simulate turbulent non-premixed propane air preheated flame in a minichannel. We use a detailed kinetics scheme, i.e. GRI mechanism 3.0, and the flamelet model to perform the combustion modeling. The turbulence-chemistry interaction is taken into account in this flamelet modeling using presumed shape probability density functions PDFs. Considering an upwind-biased physics for the current reacting flow, we implement the physical influence upwinding scheme PIS to estimate the cell-face mixture fraction variance in this study. To close the turbulence closure, we employ the two-equation standard κ-ε turbulence model incorporated with suitable wall functions. Supposing an optically thin limit, it needs to take into account radiation effects of the most important radiating species in the current modeling. Despite facing with so many flame instabilities in such small size configuration, the current method performs suitably with proper convergence, and the encountered instabilities are damped out automatically. Comparing with the experimental measurements, the current extended method accurately predicts the flame structure in the minichannel configuration.

scholarly journals Observations on Jet-Flame Blowout

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
N. J. Moore ◽  
J. L. McCraw ◽  
K. M. Lyons
Keyword(s):  
Reaction Zone ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Leading Edge ◽  
Transient Behavior ◽  
Turbulent Flames ◽  
Ignition Source ◽  
Jet Flame ◽  
Physically Based ◽  
Air Diffusion

The mechanisms that cause jet-flame blowout, particularly in the presence of air coflow, are not completely understood. This work examines the role of fuel velocity and air coflow in the blowout phenomenon by examining the transient behavior of the reaction zoneat blowout. The results of video imaging of a lifted methane-air diffusion flame at near blowout conditions are presented. Two types of experiments are described. In the first investigation, a flame is established and stabilized at a known, predetermined downstream location with a constant coflow velocity, and then the fuel velocity is subsequently increased to cause blowout. In the other, an ignition source is used to maintain flame burning near blowout and the subsequent transient behavior to blowout upon removal of the ignition source is characterized. Data from both types of experiments are collected at various coflow and jet velocities. Images are used to ascertain the changes in the leading edge of the reaction zone prior to flame extinction that help to develop a physically-based model to describe jet-flame blowout. The data report that a consistent predictor of blowout is the prior disappearance of the axially oriented flame branch. This is witnessed despite a turbulent flames' inherent variable behavior. Interpretations are also made in the light of analytical mixture fraction expressions from the literature that support the notion that flame blowout occurs when the leading edge reaches the vicinity of the lean-limit contour, which coincides approximately with the conditions for loss of the axially oriented flame structure.

Theoretical and numerical analysis of a spreading opposed-flow diffusion flame

2009 ◽  
Vol 465 (2110) ◽  
pp. 3209-3238 ◽  
Author(s):  
Yang Long ◽  
Indrek S. Wichman
Keyword(s):  
Heat Flux ◽  
Solid Fuel ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Leading Edge ◽  
Species Distributions ◽  
Variable Density ◽  
Simulation Code ◽  
Total Enthalpy ◽  
Numerical Predictions

This article describes the macroscopic and microscopic features of flames spreading over solid-fuel surfaces by examining and comparing three models. The first model examines ignition and flame spread over a solid-fuel surface using a two-dimensional numerical simulation code. This model employs variable density, variable thermophysical properties and one-step global finite-rate chemistry. The second model, a macroscopic ‘field’ model, is solved in terms of the mixture fraction ( Z ) and total enthalpy ( H ) functions. Comparisons are made with numerical predictions for primitive quantities: temperature, species distributions and velocity fields; and derived quantities: heat flux, mass flux, mixture fraction, enthalpy function and flame stretch rate. The third model yields a ‘localized’ flame structure description near the flame attachment point. Theoretical formulas are produced for the quenching distance, the leading edge heat flux, and the flame structure, as characterized by reactivity, temperature field and species distributions. The analytical predictions are compared with numerical simulations to derive flame microstructure scaling parameters.

Flame structure of an axisymmetric hydrogen-air diffusion flame

1991 ◽  
Vol 23 (1) ◽  
pp. 567-573 ◽  
Author(s):  
Seishiro Fukutani ◽  
Nílson Kunioshi ◽  
Hiroshi Jinno
Keyword(s):  
Diffusion Flame ◽  
Flame Structure ◽  
Air Diffusion

Observation of Micro Premixed Flames Surrounded by High Temperature Burned Gas Flow

2011 ◽  
Author(s):  
Manabu Fuchihata ◽  
Tamio Ida ◽  
Kazunori Kuwana ◽  
Satoru Mizuno
Keyword(s):  
High Temperature ◽  
Diffusion Flame ◽  
Gas Flow ◽  
Flame Structure ◽  
Premixed Flames ◽  
Micro Scale ◽  
Diffusion Mixing

Flame structure of micro scale methane-air premixed flames is investigated experimentally. The flame is stabilized even on the burner whose diameter is 0.3 mm when it is with pilot flame. However, shape of the flame formed on the burner whose diameter is less than 1 mm is similar to micro diffusion flame. It is supposed that the flame formed on the burner whose diameter is submillimeter is dominated by the diffusion mixing of oxygen and methane from the premixture and heat and radicals from the pilot gas flow.

Impact of Combustion Models on Emissions Predictions From a Piloted Methane-Air Diffusion Flame

2019 ◽  
Author(s):  
Chitralkumar V. Naik ◽  
Hossam Elasrag ◽  
Rakesh Yadav ◽  
Ahad Validi ◽  
Ellen Meeks
Keyword(s):  
Mixture Fraction ◽  
Flame Structure ◽  
Direct Integration ◽  
Finite Rate ◽  
Modeling Approaches ◽  
Combustion Models ◽  
Eddy Simulation ◽  
Flamelet Generated Manifold ◽  
Simulation Results ◽  
Detailed Kinetics

Abstract Combustion models can have a significant impact on flame simulations. While solving finite rate chemistry typically yields more accurate predictions, they depend significantly on the detailed kinetics mechanism used. To demonstrate the effect, Large Eddy Simulation (LES) of Sandia Flame D [1] has been performed using various combustion models. Four different detailed kinetics mechanisms have been considered. They include DRM mechanism with 22 species, GRI-mech 2.11 with 49 species, GRI-mech 3.0 with 53 species [2], and Model Fuel Library (MFL) mechanism with 29 species [3]. In addition to the mechanisms, two modeling approaches considered are direct integration of finite rate kinetics (FR) and Flamelet Generated Manifold (FGM). The performance is compared between combinations of the mechanisms and combustion-modeling approaches for prediction of the flame structure and pollutants, including NO and CO. The mesh contains about half a million hexahedral cells and LES statistics were collected over ten flow throughs. Advanced solvers including dynamic cell clustering using the Chemkin-CFD solver in Fluent have been used for faster simulation time. Based on comparison of simulation results to the measurements at various axial and radial positions, we find that the results using the FGM approach were comparable to those using direct integration of FR chemistry, except for NO. In general, the simulation results are in good agreement with the experiment in terms of aerodynamics, mixture fraction and temperature profiles. However, kinetics mechanisms were found to have the most pronounced effect on emissions predictions. NO was especially more sensitive to the kinetics mechanism. Both versions of the GRI-mech fell short in predicting emissions. Overall, the MFL mechanism was found to yield the closest match with the data for flame structure, CO, and NO.

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