Geared Turbojet Designs or Hardware?

[aim9xray]

With the emergent success of Pratt & Whitney's Geared TurboFan (GTF Family) the question occurs to me - was there a geared turbojet design that made it to hardware? Indeed - were there any geared turbojet designs put forward?

 

[GeorgeA]

Well, the objective of the GTF (and the ADP before it) is to decouple the fan from the core, so the fan can operate at a more efficient speed. Given that a turbojet doesn't have a bypass fan by definition, I'm not sure there'd be a benefit to having the forward stage decoupled.

 

[LowObservable]

To be correct, the idea is that both the fan and the turbine can operate at a more efficient speed, allowing for a smaller and higher-revving LP turbine and shaft.

 

[tartle]

The reason for gearing is to match the tip speed of of a relatively small tip diameter turbine with a large tip diameter prop or fan. Operating each at its optimum design condition would mean each is at a different rpm. One reason to slow a fan is to bring it back into transonic speed at tip ... or subsonic to reduce noise generation. Putting up bypass ratio will also cause the tip diam to grow on fan so further mismatching with the turbine. At the end of the WW2 there was a version of the RCA series that had a geared LP compressor... never built though the Clyde turboprop had a geared lp compressor as we discussed earlier in thread.
A turbojet design point for a compressor and its driving turbine are at similar diameters and velocities so the is no merit in gearing them.. extra weight for no gain and maybe a loss!