Turbulent lifted flames in a vitiated coflow investigated using joint PDF calculations

RANS modelling of a lifted H2/N2 flame using an unsteady flamelet progress variable approach with presumed PDF

“…The numerical set-up is very similar to the carefully chosen one considered by Cao et al [21], also in a RANS framework (with transported PDF modelling in that case). Starting at the fuel injector exit, the computational domain -50D-long (in axial direction) and 20D-wide (in radial direction), with D = 4.57mm the injector diameter -is a half-plane of the 2D axisymmetric geometry considered.…”

“…For R < r < 1.88R, both profiles are connected with an exponential decay U = α+β. exp −γr 2 , with γ ≈ 480000, leading to a similar profile as used in [21]. This axial mean velocity profile is normalised with U norm such that the correct experimental bulk velocity of 107m/s is imposed at the injector exit (i.e.…”

“…The Reynolds stress profiles are specified as u 2 = u u (axial), v 2 = v v (radial) and w 2 = v 2 (azimuthal). The turbulent shear stress is specified in a similar way as in [21] such that u v = ρ uv u v , with ρ uv = 0.4(r/R) for r ≤ R and ρ uv = 0.4 for r > R. Finally, the turbulent dissipation profile is specified by supposing that the dissipation term is equal to the production term in the turbulent kinetic energy transport equation:…”

“…The inlet profiles are specified in such a way that the fluctuating axial and radial velocity profiles, u and v , are similar to the experimental profiles used in [21], where the influence of the inlet boundary conditions was carefully studied. In this RANS framework, the influence of the wall flows on the inner and outer sides of the fuel nozzle are simply accounted for at the injector exit by specifying the turbulent profiles for mean velocity components, Reynolds stresses and turbulent dissipation.…”

“…In order to deal with realistic conditions while involving a small number of chemical species, we consider a steady lifted H 2 /N 2 turbulent jet flame in a coflow of hot products at atmospheric pressure (the vitiated co-flow burner developed by Dibble and co-workers), first measured at Berkeley university by Cabra et al [16,17] and later at Sydney university at different operating conditions [18,19]. This flame has mainly been modelled in a RANS framework using transported PDF methods with different mixing models [16,[20][21][22][23][24][25][26][27][28]. A first CMC calculation of this flame was reported in [29].…”