DOI: 10.1615/ICHMT.2012.ProcSevIntSympTurbHeatTransfPal
ISBN Print: 978-1-56700-302-4
ISSN: 2377-2816
RANS investigation of hysteresis of vortex breakdown in the cold model of a swirl burner
摘要
The phenomenon of hysteresis detected in strongly swirling premixed flames when transiting from an attached long flame to a short lifted flame and vice versa (Hübner et al. 2003; Tummers et al. 2008) is investigated in a cold regime by RANS modelling. In contrast to most computational studies of swirling flows in model-combustors, the present flow is unconfined, thus posing additional challenge to computer modelling. The results obtained for a high-swirl number (the ratio of the tangential to bulk axial velocity, N, up to 2.8), high-flow-rates with the elliptic-relaxation eddy-viscosity model (ζ − f, Hanjalic et al. 2004) show encouraging agreement with the experimental results of Hübner (2010) for regimes on both sides of the stability limit when increasing and decreasing flow rates at a constant rotation speed. Moreover, the computations confirm the experimental findings that two regimes, corresponding to "long" and "short" flames can be realized even in a nonreacting situation at precisely the same conditions (flow rates and rotation rates) depending on from which regime (stable or unstable) the overlapping region is approached. The study is aimed at testing the capabilities of some advanced eddy-viscosity models in detecting the vortex breakdown and its hysteresis.