Numerical Modeling of Stationary But Developing Premixed Turbulent Flames

2006 ◽  
Author(s):  
Pratap Sathiah ◽  
Andrei N. Lipatnikov
Keyword(s):  
Bluff Body ◽  
Burning Velocity ◽  
Rectangular Channel ◽  
Turbulent Flame ◽  
Flame Stabilization ◽  
Turbulent Flames ◽  
Turbulent Diffusivity ◽  
Flame Thickness ◽  
Premixed Turbulent Flames ◽  
Premixed Turbulent Flame

A typical stationary premixed turbulent flame is the developing flame, as indicated by the growth of mean flame thickness with distance from flame-stabilization point. The goal of this work is to assess the importance of modeling flame development for RANS simulations of confined stationary premixed turbulent flames. For this purpose, submodels for developing turbulent diffusivity and developing turbulent burning velocity, which were early suggested by our group (FSC model) and validated for expanding spherical flames [4], have been incorporated into the so-called Zimont model of premixed turbulent combustion and have been implemented into the CFD package Fluent 6.2. The code has been run to simulate a stationary premixed turbulent flame stabilized behind a triangular bluff body in a rectangular channel using both the original and extended models. Results of these simulations show that the mean temperature and velocity fields in the flame are markedly affected by the development of turbulent diffusivity and burning velocity.

Further development of the three-region model of a premixed turbulent flame I. Turbulent diffusion dominated region 2

1979 ◽  
Vol 368 (1733) ◽  
pp. 267-282 ◽  
Keyword(s):  
Turbulence Intensity ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Turbulent Energy ◽  
Variable Density ◽  
Turbulent Flames ◽  
Laminar Burning Velocity ◽  
Advection Term ◽  
Set Up ◽  
Premixed Turbulent Flame

A study of the balance equation for turbulent kinetic energy of a premixed turbulent flame has been carried out. Various parameters constituting each term have either been measured or have been calculated from previously measured values. Propane and hydrogen were used as fuels, and the turbulence intensity of the approach flow was varied. Thus, an energy balance of turbulence in a flame has been set up. These results show that increase in both approach turbulence intensity and laminar burning velocity reduce the ratio of production/dissipation in a flame. Thus the stabilizing influence of laminar burning velocity is fully confirmed. The turbulent convection term is found to remain substantially unaltered. The advection term, on the other hand, changes from a loss to a gain in the turbulent energy of the flame. Finally, it is shown that significant differences exist between a flame and a non-reactive variable density axisymmetric jet. These conclusions make the study of turbulent flames unique in that theories that do not accommodate their special features should either be modified or abandoned.

Measurement of Temperature Profile in Non-Premixed Turbulent Flame of Lean LPG/Air Mixture

2008 ◽  
Author(s):  
Hayder Abed Dhahad
Keyword(s):  
Temperature Profile ◽  
Turbulent Flame ◽  
Turbulent Flames ◽  
Maximum Temperature ◽  
Simple Type ◽  
Temperature Profiles ◽  
Bunsen Burner ◽  
Perforated Plates ◽  
Premixed Turbulent Flames ◽  
Premixed Turbulent Flame

The current research was carried out on the topic of non-Premixed turbulent flames. The temperature profile of non-premixed turbulent flame of lean L P G- Air mixture (φ = 0.66) were obtained. A simple type of Bunsen burner with two different inside diameter and having two different perforated plates was designed in order to achieve turbulent flow. The temperature was obtained at the two diameters and different positions for perforated plates. The temperature profiles were obtained by using a fine thermocouple at height (3mm) above the burner mouth. The maximum temperature for all cases was found at flame adge, and start decreasing for both sides.

Flame Patterns and Combustion Intensity Behind Rifled Bluff-Body Frustums

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Kuo C. San ◽  
Yu Z. Huang ◽  
Shun C. Yen
Keyword(s):  
Bluff Body ◽  
Flow Behavior ◽  
Turbulent Flame ◽  
Flame Temperature ◽  
Flame Length ◽  
Turbulent Flames ◽  
Temperature Profiles ◽  
Lifted Flames ◽  
Direct Color ◽  
Jet Nozzle

Rifled fillisters were milled on cannular frustums to modulate flow behavior and to increase the turbulence intensity (TI). The TI and combustion intensity were compared in four configurations of frustums—unrifled, inner-rifled, outer-rifled, and two-faced rifled. The flame patterns and flame lengths were observed and measured by direct-color photography. The temperature profiles and (total) combustion intensity were detected and calculated with an R-type thermocouple. Three flame patterns (jet, flickering, and lifted flames) were defined behind the pure-jet nozzle. Four flame patterns (jet, flickering, bubble, and turbulent flames) were observed behind the unrifled frustum. The bluff-body frustum changes the lifted flame to turbulent flame due to a high T.I at high central-fuel velocity (uc). The experimental data showed that the grooved rifles improved the air-propane mixing, which then improved the combustion intensity. The rifled mechanism intensified the swirling effect and then the flame-temperature profiles were more uniform than those behind the pure-jet nozzle. The increased TI also resulted in the shortest flame length behind the two-faced rifled frustum and increased the total combustion intensity.

Calculation of a Premixed Swirl Combustor Using the PDF Method

1997 ◽  
Author(s):  
A. T. Hsu ◽  
M. S. Anand ◽  
M. K. Razdan
Keyword(s):  
Ad Hoc ◽  
Turbulent Flame ◽  
Reaction Rates ◽  
Turbulent Flames ◽  
Swirl Combustor ◽  
Turbulent Flame Speed ◽  
Premixed Turbulent Flames ◽  
Low Emission ◽  
Design Calculations ◽  
Complex Chemistry

The evolution probability density function (PDF) method provides a framework for the simulation of both diffusion and premixed turbulent flames. With this method, the chemical reaction rates are treated without approximation. In contrast, the conventional Reynolds-average methods need to model the mean reaction rates in turbulent flame calculations. In addition, conventional methods require special models for premixed flames that are developed under restrictive assumptions and rely on ad hoc expressions for the rate of reaction progress. The present work demonstrates the capability of the PDF method in realistic combustor design calculations. A lean premixed flame swirl combustor is simulated using the scalar PDF method, and the results are compared with experimental data. It is shown that the PDF method can correctly predict the turbulent flame speed and location of the flame. The ability of the PDF method to handle finite-rate complex chemistry of any number of reaction steps makes it an ideal candidate for emissions predictions in low emission combustor designs.

scholarly journals Effect of Stretch on Local Burning Velocity of Premixed Turbulent Flames

2007 ◽  
Vol 2 (2) ◽  
pp. 268-280 ◽  
Author(s):  
Masaya NAKAHARA ◽  
Hiroyuki KIDO ◽  
Takamori SHIRASUNA ◽  
Koichi HIRATA
Keyword(s):  
Burning Velocity ◽  
Turbulent Flames ◽  
Premixed Turbulent Flames ◽  
Local Burning

Fuel Variation Effects in Propagation and Stabilization of Turbulent Counter-Flow Premixed Flames

2018 ◽  
Author(s):  
Ehsan Abbasi-Atibeh ◽  
Sandeep Jella ◽  
Jeffrey M. Bergthorson
Keyword(s):  
High Speed ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Mass Diffusion ◽  
Flame Stabilization ◽  
Turbulent Flames ◽  
Flame Speed ◽  
Flame Surface ◽  
Differential Diffusion ◽  
Turbulent Flame Speed

Sensitivity to stretch and differential diffusion of chemical species are known to influence premixed flame propagation, even in the turbulent environment where mass diffusion can be greatly enhanced. In this context, it is convenient to characterize flames by their Lewis number (Le), a ratio of thermal-to-mass diffusion. The work reported in this paper describes a study of flame stabilization characteristics when the Le is varied. The test data is comprised of Le ≪ 1 (Hydrogen), Le ≈ 1 (Methane), and Le > 1 (Propane) flames stabilized at various turbulence levels. The experiments were carried out in a Hot exhaust Opposed-flow Turbulent Flame Rig (HOTFR), which consists of two axially-opposed, symmetric turbulent round jets. The stagnation plane between the two jets allows the aerodynamic stabilization of a flame, and clearly identifies fuel influences on turbulent flames. Furthermore, high-speed Particle Image Velocimetry (PIV), using oil droplet seeding, allowed simultaneous recordings of velocity (mean and rms) and flame surface position. These experiments, along with data processing tools developed through this study, illustrated that in the mixtures with Le ≪ 1, turbulent flame speed increases considerably compared to the laminar flame speed due to differential diffusion effects, where higher burning rates compensate for the steepening average velocity gradient, and keeps these flames almost stationary as bulk flow velocity increases. These experiments are suitable for validating the ability of turbulent combustion models to predict lifted, aerodynamically-stabilized flames. In the final part of this paper, we model the three fuels at two turbulence intensities using the FGM model in a RANS context. Computations reveal that the qualitative flame stabilization trends reproduce the effects of turbulence intensity, however, more accurate predictions are required to capture the influences of fuel variations and differential diffusion.

412 Influence of Markstein Number on Local Burning Velocity of Premixed Turbulent Flames

2005 ◽  
Vol 2005.58 (0) ◽  
pp. 145-146
Author(s):  
Masaya NAKAHARA ◽  
Hiroyuki KIDO ◽  
Kenshiro NAKASHIMA ◽  
Hideaki TAKAMOTO ◽  
Koichi HIRATA
Keyword(s):  
Burning Velocity ◽  
Turbulent Flames ◽  
Premixed Turbulent Flames ◽  
Markstein Number ◽  
Local Burning

A two-eddy theory of premixed turbulent flame propagation

1981 ◽  
Vol 301 (1457) ◽  
pp. 1-25 ◽  
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Experimental Measurements ◽  
Laminar Burning Velocity ◽  
Turbulent Reynolds Number ◽  
Theoretical Predictions ◽  
Premixed Turbulent Flame ◽  
Turbulent Burning Velocity

Available experimental data on the turbulent burning velocity of premixed gases are surveyed. There is discussion of the accuracy of experimental measurements and the means of ascertaining relevant turbulent parameters. Results are presented in the form of the variation of the ratio of turbulent to laminar burning velocities with the ratio of r.m.s. turbulent velocity to laminar burning velocity, for different ranges of turbulent Reynolds number. A two-eddy theory of burning is developed and the theoretical predictions of this approach, as well as those of others, are compared with experimentally measured values.

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