Freely propagating open premixed turbulent flames stabilized by swirl

Experimental study of premixed flames in intense isotropic turbulence*1, *2

“…The burner uses a slot type turbulence generator first developed by Videto et al [12]. The flames are stabilized by weak-swirl generated by air injection upstream of the exit [10]. The turbulence is shown to be isotropic and reaches a high level of 1.…”

“…Figure 3 shows U, u', v' and uv centerline profiles of the isothermal flow for case IV (Table 1). The mean centerline velocity U decreases linearly due to the effect of the swirl which induces centrifugal forces and causes the flow to diverge [10]. The azimuthal velocity component shows that the flow above the burner center is virtually swirl free as in the burner used for previous works [10,11].…”

“…The turbulence intensity should also be uniform across the flame brush. Our recently developed weak-swirl burner [10,11] which produces stable, adiabatic and almost planar flames satisfies many of these criteria and can be exploited for this purpose. The weak-swirl generates a divergent flow region where the flame is stabilized.…”

“…The exit rim of the burner is tapered at 450 to prevent the formation of a recirculation zone above the rim. The swirl number, S, given by Claypole and Syred [13] applies to this burner and its previous version [10] (Table 1). …”

“…Both unconditioned velocities (0.3 Jlm alumina seeds) and conditioned reactants velocities (silicone oil aerosol seeds) are measured. The LDA seeds are introduced downstream of the turbulence generator to prevent them from clogging the narrow slot Traversing technique and data reduction are the same as in [10]. The velocity spectra were analyzed by fast Fourier transform (FFl) directly from the LDA analog output with a 6KHz sampling rate.…”