Slide 1

Luiza Bondar, Andreas Class(*), Jan ten Thije Boonkkamp, Ronald Rook, Bob Mattheij Laminar flame edge dynamics A level set approach (*) Institute for Nuclear and Energy Technologies, Forschungszentrum Karlsruhe, Germany Slide 2 Combustion noise low NOx emission combustion noise perturbed gas velocity (acoustic perturbation) Laminar premixed flames Slide 3 Combustion noise velocity heat release rate Transfer function Slide 4 Flame Transfer Function (TF) To date the time delay in the flame TF is not yet fully understood experimental data by Viktor Kornilov Combustion noise Slide 5 variation of the flame front area variation of burning velocity due to flame curvature and flow strain effect of the flame on the flow near rim phenomena (movement of the flame edge) study their contribution to flame TF understand the TF behaviour separate different physical phenomena that occur in flame acoustics interaction Slide 6 G-equation model unburnt gas GG 0 flame front G=G 0 G-equation flame is a thin layer (flame front) flame is attached at the burner rim Fundamental assumptions area heat release transfer function Slide 7 G-equation model analytical models ( Ducruix (2000), Fleifil (1996) ) flame attachment no feedback of the flame on the flow very long flames burning velocity with constant direction TF first order system, no time delay Slide 8 G-equation model Detailed analytical study on the Bunsen flame dynamics analytic solutions for the transient positions of the flame front (perturbed and unperturbed situations) qualitative information on the stabilisation time dependence of the boundary conditions on the flow speed and on the laminar burning speed extension of previous theoretical models: improvement of flame description close to the burner rim improvement of the flame transfer function Bondar(2005, 2006) results: Slide 9 G-equation model /Comparison with experiments real boiler situationattached flame edge trajectory flame flowflameflow V.Kornilov (2006) Slide 10 oscillating ring (attached flame) oscillating jet (real boiler situation) no feed back on the flow yes flame attachment theoretical model oscillating ring oscillating jet effect G-equation model /Comparison with experiments theoretical model (attached flame) extend the G-equation model to account for the flame edge dynamics Slide 11 G-equation model /Extension 1) motion of the flame edge - controlled by : heat loss & variations in the flame stretch 2) in 2D the flame front becomes an open curve the classical level set method can not be applied directly Problems Solutions 1)motion of the flame edge (*) extended unified model of flames as gasdynamics discontinuities, by A.G. Class, Y. Bronner and B.J. Matkowsky ) a)normal to the flame front use extended model for (*) b)along the flame front new model S E =c(T edge -T extinction ) 2) extended the level set method (for dynamic open curves with moving ends) SLSL Slide 12 G-equation model /Extension the flame front C is defined by C={x| G(x)=0 and F(x)0 F0 G F G-equation model /Extension 90 o F G C F>0 F0 G