DESTRUCTION OF LIQUID AND GASEOUS WASTE SURROGATES IN AN ACOUSTICALLYEXCITED DUMP COMBUSTOR

Destruction of gaseous and liquid waste surrogates is studied in a two -dimensional dump combustor configuration. Two different waste surroga tes are examined: sulfur hexafluoride, which is injected in the gaseou s phase and pyrolyzed at high temperatures, and acetonitrile, which is injected in the liquid phase and can be burned in the presence of hig h concentrations of oxidizing species. Waste surrogates are injected t hrough movable ceramic plugs into the recirculation zones within the d ump combustor cavity. The movable plugs allow the combustor cavity len gth to be altered, in turn exciting or damping various acoustic modes of the device. Strong coupling among the fluid mechanics, acoustics, a nd combustion/incineration processes are observed in this device; thes e processes are representative of dump combustors in general. Among th e important observations in this study is that waste destruction is st rongly affected by the flame and recirculation zone stability. When th e flame is perturbed by large vortical structures corresponding to low -frequency ''chugging'' oscillations, or when it is chaotically destab ilized (while acoustically quiet), the recirculation zones into which waste is injected can be destabilized, and DREs for the surrogate are reduced. When the flame is stabilized under conditions which are acous tically quiet, or when the flame is only slightly wrinkled or disturbe d, as under high-frequency mode conditions, the recirculation zones ar e stable and waste is usually destroyed well. Waste destruction itself , however, is also observed to affect recirculation zone and flame sta bility in addition to affecting the device's acoustic signature.