Studies of Curvature Effects on Laminar Premixed Flames: Stationary Cylindrical Flames

Echekki, Tarek; Ferziger, Joel H.

doi:10.1080/00102209308907612

Cited by 8 publications

(3 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These observations suggested that the flame penetration lengths were not strongly affected by the tube bends. This observation was in good agreement with the results of Echekki and Ferziger (1992) in their investigation into curvature effects on laminar premixed flames. They reported that curvature alone did not alter the flame propagation rate except for curvatures located near the source.…”

Section: Flame Length Data Reductionsupporting

confidence: 90%

Empirically Derived Predicators of Natural Gas Flame Lengths in Circular Tubes

Harris

Warren²,

Raleigh

et al. 1999

HVAC&R Research

View full text Add to dashboard Cite

Flame lengths inside circular tubes, using an (in-shot) atmospheric burner design commonly found in gas-fired residential furnaces were visually observed for natural gas and air under various operating conditions. The flame length data were reduced into dimensionless flame lengths, which were shown to be linearly proportional to the Peclet number of the fuel and air mixture. The dimensionless flame length dependence reported does not scale according to the classical flame models: pre-mixed (laminar) flame or diffusion flame. Instead, the flame length dependence was found to scale with the fuel burn speed, gas/mixture properties (evaluated at the adiabatic flame temperature), and flow parameters. Currently, this is the only flame length study available for the standard atmospheric burner designs commonly used in residential heating products. The results and data reduction provide an easy method to compute flame length penetrations inside circular tubes for the burner geometry studied.

show abstract

Section: Flame Length Data Reductionsupporting

confidence: 90%

Empirically Derived Predicators of Natural Gas Flame Lengths in Circular Tubes

Harris

Warren²,

Raleigh

et al. 1999

HVAC&R Research

View full text Add to dashboard Cite

show abstract

“…The consumption speed of the flame at the centerline for the case of λ fh = 0 is higher compared to the laminar burning velocity of a corresponding planar flame. It is known that a negative curvature (flame concave towards the reactants) acts to increase the flame burning velocity [36,37], when the radius of curvature of the flame is comparable with the flame thickness. The values of S c,0 are slightly lower when heat exchange is allowed compared to the case with λ fh = 0, primarily because the flame becomes weaker as discussed before.…”

Section: Resultsmentioning

confidence: 99%

Two-dimensional simulations of steady perforated-plate stabilized premixed flames

Altay

Kedia²,

Speth

et al. 2010

Combustion Theory and Modelling

View full text Add to dashboard Cite

The objective of this work is to examine the impact of the operating conditions and the perforated-plate design on the steady, lean premixed flame characteristics. We perform two-dimensional simulations of laminar flames using a reduced chemical kinetics mechanism for methane-air combustion, consisting of 20 species and 79 reactions. We solve the heat conduction problem within the plate, allowing heat exchange between the gas mixture and the solid plate. The physical model is based on a zero-Mach-number formulation of the axisymmetric compressible conservation equations. The results suggest that the flame consumption speed, the flame structure, and the flame surface area depend significantly on the equivalence ratio, mean inlet velocity, the distance between the perforated-plate holes and the plate thermal conductivity. In the case of an adiabatic plate, a conical flame is formed, anchored near the corner of the hole. When the heat exchange between the mixture and the plate is finite, the flame acquires a Gaussian shape stabilizing at a stand-off distance, that grows with the plate conductivity. The flame tip is negatively curved; i.e. concave with respect to the reactants. Downstream of the plate, the flame base is positively curved; i.e. convex with respect to the reactants, stabilizing above a stagnation region established between neighboring holes. As the plate's thermal conductivity increases, the heat flux to the plate decreases, lowering its top surface temperature. As the equivalence ratio increases, the flame moves closer to the plate, raising its temperature, and lowering the flame stand-off distance. As the mean inlet velocity increases, the flame stabilizes further downstream, the flame tip becomes sharper, hence raising the burning rate at that location. The curvature of the flame base depends on the distance between the neighboring holes; and the flame there is characterized by high concentration of intermediates, like carbon monoxide.

show abstract

“…It can be seen that these solutions involving the confluent hypergeometric functions apply to a more general family of problems, that is, planar and axisymmetric edge flames in counterflow. Also note that these solutions resemble those describing stationary cylindrical premixed flames, Echekki & Ferziger (1993), and also involve confluent hypergeometric functions. Important properties of Kummer's functions M and U are dM…”

Section: Appendix the Stationary Solutionsmentioning

confidence: 66%

On the dynamics of the collapse of a diffusion-flame hole

Pantano

Pullin

2003

J. Fluid Mech.

View full text Add to dashboard Cite

The collapse dynamics of a diffusion-flame hole in the presence of a counterflow are studied. We construct unsteady solutions of the one-dimensional edge-flame model of Buckmaster (1996), in which heat and mass transverse losses are algebraic. The flame structure is determined in the classical limit of large activation energy. Solutions for both planar and axisymmetric strain geometry are considered for the particular case of unity Lewis number. It is shown that the final stage of the edge-flame collapse is determined by a dominant balance between the time rate of change of the mass fractions (and temperature) and diffusion, giving a self-similar structure in which the size of the edge-flame hole approaches zero, to leading (zeroth) order, as a 1 2 -power of time. This solution suggests an expansion of the full model equations in 1 2 -powers of time that allows detailed analysis of the effects of side losses and flow distribution in the edge-flame collapse process. It is found that side loss effects are apparent at the first order, whereas convection by the counterflow is first felt during collapse at the second order in the fractional-time expansion. Numerical integrations of the governing equations are found to verify the analytic results.

show abstract

Studies of Curvature Effects on Laminar Premixed Flames: Stationary Cylindrical Flames

Cited by 8 publications

References 18 publications

Empirically Derived Predicators of Natural Gas Flame Lengths in Circular Tubes

Empirically Derived Predicators of Natural Gas Flame Lengths in Circular Tubes

Two-dimensional simulations of steady perforated-plate stabilized premixed flames

On the dynamics of the collapse of a diffusion-flame hole

Contact Info

Product

Resources

About