While reading some of my gas turbine litterature I came upon a chapter concerning turbofan engines, one of the early versions had a combined freepower turbine/fan fitted downstream the gas producer.
Do anyone know if this has been attempted by anyone in the DIY community?
The problem is that the turbine blades nearest the hub get very hot while the fan blades further out are cooled by the air being sucked past them, but if the exhaust temps and revs were kept moderate it should be possible to make one that survives and possibly produce more thrust than the gas producer would have with an afterburner attached.
Anyone with turbine designing skills and an investment casting foundry willing to make one suitable for roughly 1kg/s mass flow? :-)
I've never come across anyone thats tried it , but at one time I did think about the 4th stage wheel with its labyrinth seal removed that then had a shrunk on axial comp type arrangement , the axial comp wheel needs to spin at relatively low speed otherwise the horsepower requirement gets too great , so the tensile loads on the turb blades will be reduced somewhat by the lowish rpm, whilst the shrunk on fan might have sufficient strength in itself if the mounting "band" is thick enough ............theres probably some rough drawings and numbers somewhere in my pile of papers .
I wonder if the 3D metal printing has come far enough to pull off such a project? If the wheel was printed in good quality stainless and the hot section had a coat of ceramics to keep the metal temps down it might perhaps work.