but specifically configured for removing the steam from the combustor after the steam has cooled the secondary injectors without mixing with the combustion gases in a closed cycle in this embodiment jacket 38 is sealingly joined to fuel outlets 46 around outlet holes 40 and therefore sealingly surrounds internal conduit 36 for preventing discharge of the steam into the combustor only the fuel and air mixture 24 is discharged into the conductor in this way steam 32 may be circulated through the secondary injectors for cooling the injectors and then returned to steam generator 34 in a closed loop for reuse if desired any one of the several secondary fuel injectors such as injector 48 may include a plurality of ribs or turbulators 50 disposed inside jacket 38 on the inner side outer surface or both of conduit 36 for increasing heat transfer and cooling of both conduit 36 and jacket 38 turbulators 50 trip the steam flow to enhance convection and thereby enhance cooling effectiveness fig5 illustrates yet another embodiment of one of the secondary fuel injectors 52 which again include fuel conduits 36 extending through corresponding jackets 38 the jackets include outlets 40 sealingly joined with fuel outlets 46 of inner conduit 36 in a manner identical to that illustrated in fig4 but the fuel injectors extend completely across the individual combustor can 16 in an independent and crossing.