Measurements of laminar burning velocity and Markstein number using high-speed chemiluminescence imaging

Laminar propagation of lean premixed flames ignited in stratified mixture

“…The unstretched values decrease as time increases, with a much larger values at early times than the values expected in a / = 0.6 homogeneous case, showing again the enhancement of combustion due to ignition in a richer mixture. For the three cases, the values decrease over time and tend to the same asymptotic value around 0.06 m/ s. This value seems to be smaller than the one extrapolated from experimental or numerical results [35][36][37]. Indeed, at present time, robust data at / = 0.6 in the homogeneous case are not available, mainly due to the high sensitivity of stretch for propane flames under such mixture conditions close to the flammability limit (/ = 0.55), which causes the flame to extinguish easily.…”

“…We can expect that u 0 n tends towards the fundamental burning velocity of the homogeneous flame at 0.6. However, we can notice that this value is much smaller (two times) than the expected value from the literature, around 0.13 m/s [38,[35][36][37]. This result is surprising and at our level of knowledge, we can only assume that this result is linked to our configuration of outward flame.…”

Extended LES-PaSR model for simulation of turbulent combustion

“…The reactive §ow equations are the balance equations of mass, momentum, and energy describing convection, di¨usion, and chemical reactions [1,46,10]. In LES [2], all variables are decomposed into resolved and unresolved (subgrid) components by a spatial ¦lter such that f = " f + f ′′ where " f = ρf /ρ is the Favre (or density) ¦ltered variable.…”

“…Large eddy simulation based combustion models [2,3] is a promising alternative [46] that can provide accurate data for improvement of combustion devices. The idea of LES is to compute the large (energetic) scales of the §ow, a¨ected by the boundary conditions, whilst modeling the small (less energetic) scales of the §ow.…”

“…The idea of LES is to compute the large (energetic) scales of the §ow, a¨ected by the boundary conditions, whilst modeling the small (less energetic) scales of the §ow. For nonreactive §ows, this translates into providing closure models for the subgrid transport terms [2,4], whilst for reacting §ows also the ¦ltered mixing and (highly nonlinear) reaction rate terms require closure modeling [46] as the reaction zone is not often well resolved on the grid. To overcome these di©culties, several methods have been developed, such as:…”