Dynamics of bluff-body-stabilized lean premixed syngas flames in a meso-scale channel

2017 ◽  
Vol 36 (1) ◽  
pp. 1569-1576 ◽  
Author(s):  
Bok Jik Lee ◽  
Hong G. Im
Keyword(s):  
Bluff Body ◽  
Lean Premixed ◽  
Meso Scale

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.

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.

Effects of preferential transport in turbulent bluff-body-stabilized lean premixed CH4/air flames

2012 ◽  
Vol 159 (8) ◽  
pp. 2563-2575 ◽  
Author(s):  
Robert S. Barlow ◽  
Matthew J. Dunn ◽  
Mark S. Sweeney ◽  
Simone Hochgreb
Keyword(s):  
Bluff Body ◽  
Lean Premixed ◽  
Preferential Transport

Explosive dynamics of bluff-body-stabilized lean premixed hydrogen flames at blow-off

2020 ◽  
Author(s):  
Yu Jeong Kim ◽  
Wonsik Song ◽  
Francisco E. Hernández Pérez ◽  
Hong G. Im
Keyword(s):  
Bluff Body ◽  
Lean Premixed

scholarly journals Emissions and Stability Characteristics of Flameholders for Lean-Premixed Combustion

1992 ◽  
Author(s):  
Jeffrey A. Lovett ◽  
Nesim Abuaf
Keyword(s):  
Bluff Body ◽  
Flame Temperature ◽  
Perforated Plate ◽  
Premixed Combustion ◽  
Flame Stability ◽  
Nox Emissions ◽  
Lean Premixed Combustion ◽  
Lean Premixed ◽  
The Stability ◽  
Lean Conditions

An experimental study was conducted to determine the NOx emissions and flame stability associated with various flameholders used to support lean-premixed combustion of natural gas at gas turbine conditions. Data were obtained for velocities of 6 to 24 m/s, initial temperatures of 533 to 650 K, and pressures of 3.4 to 13.6 atm. Bluff-body, perforated-plate, and swirl-stabilized flameholders were tested and compared. The results confirm that NOx emissions at ultra-lean conditions scale with the flame temperature and are essentially independent of flameholder geometry for typical combustor residence times. The stability behavior, however, was strongly affected by flameholder type, illustrating the influence of fluid mechanics on flame stability. The flame stability was related also to the dynamics produced by combustion instability. A swirl-stabilized flameholder demonstrated the best stability characteristics at the expense of flameholder pressure drop.

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