ACOUSTIC ALTERATION IN A DUMP COMBUSTOR ARISING FROM HALON ADDITION

The effects of halogen injection on the acoustical characteristics of a two-dimensional dump combustor are studied. The dump combustor used is one whose acoustic modes have been well characterized in prior expe riments (Logan, et al., 1991). Experimental observations indicate that an increase in halon addition typically causes a slight reduction in the dominant acoustic frequency, then, at a critical percentage of hal on, a switch to a higher frequency mode. It is postulated that the add ition of halon into the premixed fuel and air causes a reduction in th e laminar flame speed and a subsequent increase in the effective time lag between velocity (or pressure) perturbations and periodic heat rel ease. This time lag is then found, through one-dimensional acoustic mo deling, to result in the possibility of a mode switch in the device, c onsistent with experimental observations.