A frame for a heat engine, the frame including an inner wall extended from an inlet end to an outlet end, the inner wall forming at least in part a core flowpath, the inner wall comprising a plenum formed between an outer portion of the inner wall and an inner portion of the inner wall, wherein a cavity is formed inward of the inner portion of the inner wall, and wherein the inner wall includes a first plenum opening providing fluid communication between the cavity and the plenum, and wherein the inner wall comprises a second plenum opening providing fluid communication between the plenum and the core flowpath.