Lewis number effects on turbulent premixed flame structure

Conference · Tue Sep 01 04:00:00 EDT 1992

OSTI ID:6997720

Goix, P J ^[1]; Shepherd, I G ^[2]

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1. Centre National de la Recherche Scientifique (CNRS), 230 - Mont-Saint-Aignan (France). URA CORIA
2. Lawrence Berkeley Lab., CA (United States)

The influence of the Lewis number on turbulent flame front geometry is investigated in a premixed turbulent stagnation point flame. A laser tomography technique is used to obtain the flame shape, a fractal analysis of the multiscale flame edges is performed and the distribution of local flame front curvature is determined. Lean H[sub 2]/Air and C[sub 3]H[sub 8]/Air mixtures with similar burning rates were investigated with Lewis numbers of 0.33 and 1.85 respectively. At the conditions studied the laminar H[sub 2]/Air mixture is unstable and a cellular structure is observed. Turbulence in the reactant is generated by a perforated plate and the turbulent length scale (3mm) and intensity (7%) at the nozzle exit are fixed. The equivalence ratio is set so that the burning velocity is the same for all the cases. Results show clearly that the turbulent flame surface area is dependent on the Lewis number. For a Lewis number less than unity surface area production is observed. The shape of the flame front curvature distribution is not found to be very sensitive to the Lewis number. For the H[sub 2]/Air mixture the distribution is skewed toward the positive values indicating the presence of cusps while for the C[sub 3]H[sub 8]/Air mixture the distribution is more symmetrical. In both cases the average curvature is found to be zero, and if the local burning speed varies linearly with curvature, the local positive and negative burning velocity variations due to curvature will balance.

• Research Organization: Lawrence Berkeley Lab., CA (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6997720
• Report Number(s): LBL-32926; CONF-9210213--3; ON: DE93002571
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
AIR
ALKANES
BURNERS
DIAGNOSTIC TECHNIQUES
DIFFUSION
ELEMENTS
FLAMES
FLUIDS
FRACTALS
GAS BURNERS
GASES
GEOMETRY
HYDROCARBONS
HYDROGEN
LASERS
MATHEMATICS
NONMETALS
ORGANIC COMPOUNDS
PHOTOGRAPHY
PHYSICAL PROPERTIES
PROPANE
SURFACE AREA
SURFACE PROPERTIES
THERMAL DIFFUSIVITY
THERMODYNAMIC PROPERTIES
TOMOGRAPHY
TURBULENCE
ULTRAHIGH-SPEED PHOTOGRAPHY