scholarly journals Turbulent flame-vortex dynamics of bluff-body premixed flames

2021 ◽  
Vol 223 ◽  
pp. 28-41
Author(s):  
Marissa K. Geikie ◽  
Cal J. Rising ◽  
Anthony J. Morales ◽  
Kareem A. Ahmed
Keyword(s):  
Vortex Dynamics ◽  
Bluff Body ◽  
Turbulent Flame ◽  
Premixed Flames

SOOT DISTRIBUTION IN TURBULENT BLUFF BODY NEAR WAKE NON PREMIXED FLAMES

2018 ◽  
Author(s):  
Suzane Nascimento ◽  
Juan Jose Cruz Villanueva ◽  
Luís Fernando Figueira da Silva
Keyword(s):  
Bluff Body ◽  
Premixed Flames ◽  
Near Wake ◽  
Soot Distribution

scholarly journals Modelling of a Bluff-Body Stabilised Premixed Flames Close to Blow-Off

Computation ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 43
Author(s):  
Shokri Amzin ◽  
Mohd Fairus Mohd Yasin
Keyword(s):  
Bluff Body ◽  
Fluid Dynamic ◽  
Premixed Flames ◽  
Pollutant Emissions ◽  
Moment Closure ◽  
Recirculation Region ◽  
Scalar Dissipation ◽  
Average Error ◽  
Conditional Moment ◽  
Lean Premixed

As emission legislation becomes more stringent, the modelling of turbulent lean premixed combustion is becoming an essential tool for designing efficient and environmentally friendly combustion systems. However, to predict emissions, reliable predictive models are required. Among the promising methods capable of predicting pollutant emissions with a long chemical time scale, such as nitrogen oxides (NOx), is conditional moment closure (CMC). However, the practical application of this method to turbulent premixed flames depends on the precision of the conditional scalar dissipation rate,. In this study, an alternative closure for this term is implemented in the RANS-CMC method. The method is validated against the velocity, temperature, and gas composition measurements of lean premixed flames close to blow-off, within the limit of computational fluid dynamic (CFD) capability. Acceptable agreement is achieved between the predicted and measured values near the burner, with an average error of 15%. The model reproduces the flame characteristics; some discrepancies are found within the recirculation region due to significant turbulence intensity.

Time and Space Series Analysis of Spectral Radiation Intensities for a Partially Premixed Turbulent Flame

2003 ◽  
Author(s):  
Yuan Zheng ◽  
Jay P. Gore
Keyword(s):  
Single Point ◽  
Turbulent Flame ◽  
Premixed Flames ◽  
Model Parameters ◽  
Time And Space ◽  
Spectral Radiation ◽  
Series Analysis ◽  
Partially Premixed Flames ◽  
Partially Premixed ◽  
Premixed Turbulent Flame

A recently developed technique called time and space series analysis was used to calculate the mean and fluctuating spectral radiation intensities leaving diametric and chord-like paths in turbulent partially premixed flames. A standard flame (Flame D) from Sandia Workshop on Turbulent Non-premixed Flames was selected to allow an evaluation of the radiation calculations at least at the single point statistics level. Measurements of spectral radiation intensities using a fast infrared array spectrometer provide an evaluation of the computations and also allow estimation of the length and time scales of scalar fluctuations, which appear as model parameters in the time and space series analysis modeling.

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.

scholarly journals Dynamics of lean premixed flames stabilized on a meso-scale bluff-body in an unconfined flow field

2018 ◽  
Vol 13 (6) ◽  
pp. 48 ◽  
Author(s):  
Yu Jeong Kim ◽  
Bok Jik Lee ◽  
Hong G. Im
Keyword(s):  
Bluff Body ◽  
Proper Time ◽  
Premixed Flames ◽  
Narrow Channel ◽  
Flame Stabilization ◽  
Inflow Velocity ◽  
Lean Premixed Flames ◽  
Lean Premixed ◽  
The Mean ◽  
Meso Scale

Two-dimensional direct numerical simulations were conducted to investigate the dynamics of lean premixed flames stabilized on a meso-scale bluff-body in hydrogen-air and syngas-air mixtures. To eliminate the flow confinement effect due to the narrow channel, a larger domain size at twenty times the bluff-body dimension was used in the new simulations. Flame/flow dynamics were examined as the mean inflow velocity is incrementally raised until blow-off occurs. As the mean inflow velocity is increased, several distinct modes in the flame shape and fluctuation patterns were observed. In contrast to our previous study with a narrow channel, the onset of local extinction was observed during the asymmetric vortex shedding mode. Consequently, the flame stabilization and blow-off behavior was found to be dictated by the combined effects of the hot product gas pocket entrained into the extinction zone and the ability to auto-ignite the mixture within the given residence time corresponding to the lateral flame fluctuations. A proper time scale analysis is attempted to characterize the flame blow-off mechanism, which turns out to be consistent with the classic theory of Zukoski and Marble.

Computation of 3D Turbulent Not-Premixed Reacting Flows Using an Implicit Unstructured Solver

2000 ◽  
Author(s):  
P. Adami ◽  
F. Martelli
Keyword(s):  
Bluff Body ◽  
Cfd Simulation ◽  
Turbulent Flame ◽  
Steady State Solution ◽  
Reacting Flows ◽  
Tvd Scheme ◽  
Reacting Flow ◽  
Riemann Solver ◽  
Turbulent Reactive Flows ◽  
Volume Method

A 3D CFD simulation of turbulent reactive flows is discussed. The original compressible version of the solver HybFlow designed for turbine rows investigation is here applied for low speed burning flow. A conserved scalar approach is considered to simulate the turbulent reacting flow field of non-premixed flames. The spatial discretization is based on an upwind finite volume method for unstructured grids using the Roe’s Riemann solver with a non-linear TVD scheme. The steady state solution is computed by means of an implicit relaxed Newton method. The linear solver is GMRES coupled with an ILU(0) preconditioning scheme. The turbulence chemistry interaction is described using a presumed β-PDF Flamelet approach. Two test applications are here presented to verify the methodology characteristics for a pilot-jet turbulent flame and a bluff-body stabilized flame both using CH4. A model combustor supplied with propane is also briefly shown as an example of application to a more realistic configuration.

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