For all you guys that don't want to hear more about gas turbines hit the "D"
key now.
Since Dale aked.
The answer to your question is almost the same as a recip engine.
The Ford gas turbine had variable geometry power turbine nozzles, that could
actually change the direction of air flow thru the power turbine to provide
braking action. Called simply "retard" Gassifier speed was held to I think
64%. Idle speed was 52% and design gassifier was 37500 RPM. We had a 10:1
or so internal gear reduction on the power turbine shaft so 3600 RPM was
design output shaft speed. The nozzles worked but not nearly as good
braking as a NTC 335 with a jake brake. Or anything with a jake for that
matter. It helped a little running down hill, but we did have less brake
life than conventional rigs. One interesting design feature was quite
revolutionary for its time was an investment cast compressor turbine wheel
made from a propriority ford alloy that was similar to Hast X. This was the
feature that was to make production costs more feasable, but provided many
problems with tip clearance to the shroud/nozzle. This engine was designed
to run at 1900 degrees F turbine inlet temperature, which was very hot for
its time of 1969 - 73. (gee I run my turbos almost that hot these days)
The programs demise can be attributed to tip clearance issues, and ceramic
regenerator core failures that were eventually traced back to a process
change the supplier implemented without telling Ford. (sound famaliar?) I
have always wanted to do a turbine vehicle, but never had the guts to do it.
Besides the altitude density thing gets to the rotor motor too. In Denver
on a 100 degree day, we were down 25% in power. No charge air cooling for
these babys.
OK guys anything further I'll take off line. Unless I hear differently.
BTW the ceramic regenerator core material and manufacturing process
eventually became a catalyst core producer. We believe it is the came
honeycomb shape. Our core was 3" thick and 36" in diameter with a solid
ceramic hub and an iron ring gear bonded on the outside diameter for driving
at 15 rpm. Hard to imagine without a model or photos of the engine. If
anyone is interested I have photos.
Rick
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