Experimental and theoretical study of secondary acoustic instability of downward propagating flames: Higher modes and growth rates

Exploring a critical diameter for thermo-acoustic instability of downward propagating flames in tubes

“…This can be observed from the pressure fluctuations which are shown for two frequency ranges. More about higher modes can be learned from our earlier work [5].…”

“…The corrugated structure is due to parametric instability of flame front in the acoustic field [4] and is the cause of secondary instability [5]. This parametric instability has been studied analytically for planar flame [6] fronts and also extended to spherical flames [7] and triple flames [8].…”

“…For much stronger mixture, there is no transition to flat flame and initial curved flame directly transitions to secondary instability leading to "complete instability" of a flat flame in acoustic field [9]. Higher modes of parametric instability can be observed with even stronger mixtures [5]. Pressure coupling [10] [11] [12] and velocity coupling [13] has been proposed to understand the mechanism of instability and predict its growth rate.…”

“…Onset of primary instability [17] and parametric instability [18][19] has also been studied in downward propagating flames using laser irradiation technique which sheds light on turbulization mechanism of flat flame [20] [21]. Effect of Lewis number (Le) on primary [22] and secondary instability [5] [19] shows that lower Le mixtures are more prone to instability. Thermoacoustic instabilities were also studied in annular space [23] and Hele-Shaw cells [24] to understand effect of Markstein number.…”

A Lattice-Boltzmann study of premixed flames thermo-acoustic instabilities

“…In the present paper, we will apply the LB method to the problem of interaction with acoustics of premixed flames propagating in tubes (or in our case in 2D channels), which has been a classical problem since the work of Markstein [32] (see also [33,34]). Without acoustics, a flame propagating in a tube is submitted to the hydrodynamic Darrieus-Landau (DL) instability, leading to a cellular front for flames propagating downward.…”