scholarly journals Analysis of a stagnation-point premixed flame influenced by inert spray, heat loss, and non-unity Lewis number

2013 ◽  
Vol 37 (3) ◽  
pp. 1333-1346 ◽  
Author(s):  
Shuhn-Shyurng Hou
Keyword(s):  
Stagnation Point ◽  
Heat Loss ◽  
Lewis Number ◽  
Premixed Flame

On the Stability of Planar Premixed Flames Under Nonadiabatic Conditions and Preferential Diffusion

2017 ◽  
Vol 9 (3) ◽  
Author(s):  
Eman Al-Sarairah ◽  
Bilal Al-Hasanat ◽  
Ahmed Hachicha
Keyword(s):  
Heat Loss ◽  
Numerical Study ◽  
Lewis Number ◽  
Premixed Flame ◽  
Constant Density ◽  
Damkohler Number ◽  
Damköhler Number ◽  
Number Ratio ◽  
Preferential Diffusion ◽  
The Stability

In this paper, we provide a numerical study of the stability analysis of a planar premixed flame. The interaction of preferential diffusion and heat loss for a planar premixed flame is investigated using a thermodiffusive (constant density) model. The flame is studied as a function of three nondimensional parameters, namely, Damköhler number (ratio of diffusion time to chemical time), Lewis number (ratio of thermal to species diffusivity), and heat loss. A maximum of four solutions are identified in some cases, two of which are stable. The behavior of the eigenvalues of the linearized system of stabilty is also discussed. For low Lewis number, the heat loss plays a major role in stabilizing the flame for some moderately high values of Damköhler number. The results show the effect of increasing or decreasing Lewis number on adiabatic and nonadiabatic flames temperature and reaction rate as well as the range of heat loss at which flames can survive.

Multiplicity of Premixed Flames Under the Effect of Heat Loss

2017 ◽  
Vol 9 (3) ◽  
Author(s):  
Eman Al-Sarairah ◽  
Chaouki Ghenai ◽  
Ahmed Hachicha
Keyword(s):  
Strain Rate ◽  
Heat Loss ◽  
Combustion Wave ◽  
Premixed Flames ◽  
Lewis Number ◽  
The Other ◽  
Premixed Flame ◽  
Two Dimensional ◽  
Combustion Waves ◽  
Loss Parameter

We investigate numerically the effect of heat loss and strain rate on the premixed flame edges encountered in a two-dimensional counterflow configuration for Lewis number higher than one. Under nonadiabatic conditions, multiple flame edges and multiple propagation speeds (positive and negative) are discussed. Different regions of multiple propagation speeds have been revealed ranging from two to four, depending on the value of the heat loss parameter and Damkohler number, which is inversely proportional to the strain rate. A combustion wave is modeled by connecting a strongly burning flame on one side of the burner to a weakly burning flame on the other side. These combustion waves are changing with increasing Dam number into flame edges with the fact that the strongly burning flame is the dominant.

Interaction of Lewis number and heat loss effects for a laminar premixed flame propagating in a channel

2008 ◽  
Vol 47 (1) ◽  
pp. 84-92 ◽  
Author(s):  
Subhadeep Chakraborty ◽  
Achintya Mukhopadhyay ◽  
Swarnendu Sen
Keyword(s):  
Heat Loss ◽  
Lewis Number ◽  
Premixed Flame

scholarly journals Extinction Limits of Nonadiabatic, Catalyst-Assisted Flames in Stagnation-Point Flow

2001 ◽  
Author(s):  
Stephen B. Margolis ◽  
Timothy J. Gardner
Keyword(s):  
Stagnation Point ◽  
Heat Loss ◽  
Heat Production ◽  
Fuel Efficiency ◽  
Premixed Flames ◽  
Stagnation Point Flow ◽  
Pollutant Formation ◽  
Flow Geometry ◽  
Parameter Ranges

Abstract Because combustion is essentially an Arrhenius process, premixed flames generally can only exist within certain parameter ranges, or extinction limits, that correspond to a rate of heat production that is sufficient to sustain the reaction in a given flow geometry. Nonetheless, it is frequently desirable to extend these limits, often for the purpose of increasing fuel efficiency and/or reducing the rate of formation of pollutant species. Another emerging motivation is to allow combustion to be sustained in relatively small volumes, which are characterized by larger surface-to-volume ratios, that would otherwise lead to extinguishing levels of heat loss. Surface catalysts are widely used to achieve such enhancements with respect to efficiency and pollutant formation, and we wish to now consider the role catalysts might play with respect to nonadiabatic flames.

scholarly journals Impact of Stretch and Heat Loss on Flame Stabilization in a Lean Premixed Flame approaching Blow-off

2018 ◽  
Vol 148 ◽  
pp. 250-257 ◽  
Author(s):  
Pier Carlo Nassini ◽  
Daniele Pampaloni ◽  
Antonio Andreini
Keyword(s):  
Heat Loss ◽  
Flame Stabilization ◽  
Premixed Flame ◽  
Lean Premixed

Numerical Simulation on the Instability of Cylindrically Expanding Premixed Flames With Radiative Heat Loss at Low Lewis Numbers

2011 ◽  
Author(s):  
Takafumi Kusakai ◽  
Satoshi Kadowaki
Keyword(s):  
Heat Loss ◽  
Thermal Instability ◽  
Radiative Heat ◽  
Premixed Flames ◽  
Lewis Number ◽  
Radiative Heat Loss ◽  
Low Gravity ◽  
Gravity Condition ◽  
Quenching Condition ◽  
Reactive Gases

The instability of cylindrically expanding premixed flames with radiative heat loss was studied by two-dimensional unsteady calculations of reactive gases, based on the diffusive-thermal model equation. When the Lewis number was unity, instability phenomena were not observed. When the Lewis number was sufficiently low, on the other hand, cellular-shaped fronts on adiabatic and non-adiabatic cylindrical flames were observed, which was due to diffusive-thermal instability. As radiative heat loss increased, the behavior of cellular fronts became more unstable. This indicated that the radiation promoted the unstable behavior of flame fronts at low Lewis numbers. When radiative heat loss was much large compared with the quenching condition of a planar flame, cylindrical flames were broken up and several small flames appeared. This was in qualitative agreement with the experimental results on the dynamic behavior of lean hydrogen-air premixed flames with radiative heat loss under the low gravity condition. Several small flames appeared on the grounds that large curvature of flame fronts was necessary to keep high temperature against radiative heat loss.

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