A gas turbine engine augmentor includes an inter-liner cavity including an axially extending annular gap separating augmentor and tailpipe liners. A purge flow cavity is in fluid communication with a fan bypass duct and with the cavity. An ejector in fluid communication with the bypass duct includes an ejector nozzle positioned and aimed to direct an ejector nozzle flow from inside the ejector nozzle across the cavity. The purge flow cavity may be bifurcated into forward and aft purge flow cavities which are in fluid communication with the ejector and inter-liner cavity respectively. An annular dividing wall having ejector metering apertures may be disposed between the forward purge flow cavity and an ejector plenum of the ejector. An annular trapped vortex cavity pilot may be located upstream of the annular gap. The aft purge flow cavity may be outwardly bounded by a seal having purge metering apertures disposed therethrough.