Investigations of the effects of spray characteristics on the flame pattern and combustion stability of a swirl-cup combustor

An experimental study on both spray and combustion were carried out in order to investigate the effects of gap of nozzle shroud on combustion stability and correlate the spray characteristics with some of combustion performances in a swirl-cup combustor, such as flame pattern, ignition and lean blow-out performances. The performances of ignition and lean blow-out were evaluated in a three-sector combustor in which only the middle dome is operated. Spray analyses were conducted on test sets in a quiescent open-air environment, with measurements of spray pattern by kerosene planar laser induced fluorescence (Kerosene-PLIF) and droplet size by Fraunhofer diffraction techniques. The optimum gap of nozzle shroud for ignition performance is obtained. Based on the droplets spatial distribution in the combustor with recognition of multi-phase nature of the ignition process, the phenomenon that the gap of nozzle shroud has a great impact on the ignition performance was analyzed. Meanwhile, one also analyzed the lean blow-out performance associated with the droplets spatial distribution. By tuning the fuel mixture from ignition condition to the near lean blow-out condition, one found that the lean blow-out performance is less sensitive to the gap of nozzle shroud. Furthermore, CFD simulation results of the flow field under the typical combustor operation conditions were presented and discussed to provide insight into the interaction between air streams from anti-carbon apertures and primary swirler.