Abstract: Difficulties in accommodating thermal growth in a combustor for providing hot gases of combustor to drive, for example, a turbine wheel (10) are avoided in a combustor construction, including a housing (36) defining a combustion chamber having a relatively narrow inlet (38), an enlarged combustion area (42) and a relatively narrow outlet (40) opposite of the inlet (38). A fuel injector (46) is disposed in the inlet (38) for injecting fuel (50) at least into the combustion area (42) and a plenum case (56) surrounds the housing (36) in generally spaced relation. The plenum case (56) is adapted to be connected to a source (62) of oxidant under pressure and is in fluid communication with the inlet (38) to provide oxidant thereto to support combustion of fuel in the combustion area (42). A conduit (44) extends from the outlet (40) to be connected to a turbine nozzle (16) and a diaphragm (122) is interposed and sealingly engages both the housing (36) and the plenum case (56) near the outlet (40).