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.