FanJet Dreams for Canard Pushers

[JCP]

Has anybody considered using a surplus APU turbine as a "poor man's" FanJet ?

I'm not thinking about the APT/Innodyne Turbo-Prop configuration.

What's bouncing around my head is using 6000 RPM output of a T62-T32, or 8000 RPM output of a T62-16, to directly drive a smaller diameter multi-blade fan.

Lets say a 2.5 to 3 foot fan diameter to keep the blades just subsonic..

Various small helicopter designs have proven that these turbines are airworthy, and hundreds of thousands of hours use as APU's in commercial & military aircraft.

As with the various designs gearing down the turbine's 6000/8000 RPM output to more nominal propeller speeds, the fan will have to run at constant RPM.

Thus the fan would have to be adjustable pitch for throttle and starting.

With the light weight of the turbine itself, it could be located further aft,
downstream of fan.  

Exhaust thrust and heat would then add to the overall thrust.

Assuming a repackage of gearbox using CNC machining, to minimize cross section area in the duct.  A T62-16 has a right angle gearbox, which
may allowing the remoting of all accessory's outside the duct.

A pair of T62-16's as a twin ?

[Anonymous]

Has anybody considered using a surplus APU turbine as a "poor man's" FanJet ?

Bad idea. An APU is designed to run at one RPM and it does it quite well.

Jack

[Waiter]

I've got a 160hp T62 (from Ground Power Unit) sitting in my hangar that runs and makes real live jet noise.  

Only thing I need is a reduction drive to bring the 6000rpm down to 2500, and a variable pitch / constamt speed prop that can go from beta to feather.

The prop is the real hold up. If anyone has any ideas on a prop, it will move this project up on the priority list.


Waiter.

(I LIKE JP4)

[Glenn S.]

Waiter,   It has been done before so it may not be a bad idea after all. If memory serves me right, the Turbine Luscombe used a T-62, Bede Micro uses the T-62 for its turboprop conversion BD-5, and now you have several kit helicopter manufactures adapting them for use. NSI Aero has made gearboxes in the past to bolt up the geabox of the T-62 and has an electric prop that can feather. That alone has to be worth something when you touch down in your long and throw it into reverse. After all, if the Starship can do it ... I have owned several T-62 in the past and they are prety much bullet proof. I hope this doesn't cahnge the priority list
Regards
Glenn Saunders
N914VE

[dave]

  heres a question...
    if we even got the t-32 turbines./ apu etc...installed..with prop.
  In AN EZE...whers does the HUGE super hot exhaust point to.
     i have a friend who is tinkering with one...BUT on a RV,,,,the EXHAUST IS HUGE....on a million dollar Starship sure,,, buuut on a long?..HMMM
   its probably  WHY the cozy jet is a jet and not a t-prop,,,who knows?

[JonC]

  heres a question...
    if we even got the t-32 turbines./ apu etc...installed..with prop.
  In AN EZE...whers does the HUGE super hot exhaust point to.
     i have a friend who is tinkering with one...BUT on a RV,,,,the EXHAUST IS HUGE....on a million dollar Starship sure,,, buuut on a long?..HMMM
   its probably  WHY the cozy jet is a jet and not a t-prop,,,who knows?

Actually it probably comes down to the fact that there are not many turboprop pusher configurations out there.  I would love to have a turboprop just for the uniqueness factor, the engines are not really the issue, there are plenty of engines out there that can just have a prop thrown on and go.... if you can find an acceptable prop. In the few searches I did though, I could not find a prop that would fit the bill for the engines. Sure you could mount a fixed pitch prop to it, but in my mind the point of having a turboprop is having a constant speed prop with beta range.

One I was looking at was a Boeing 502-6, it is already geared to run 2750rpm on the output shaft... but, it only throws out 160hp, and weighs 200lbs, which is really not a great weight/power ratio for a turbine, but would help in a CG aspect since it will be closer to the weight of a o-320 than the lighter turbines.

You also have an Allison/Rolls Royce T-63, comes in at 136lbs, and throws out 300hp... but it has 6000rpm output shaft speed... so it needs a PSRU on it, which would probably bring it close to the weight of the 502-6 with almost twice the power.

As for the exhaust... just dump it out the bottom of the airplane. You dont have to have the exhaust stack extend very far past the airframe... just make sure you use some sort of heat sheilding on the fibreglass behind it. Don't want to postcure it at 1000+ degrees in flight.

Also... once you go to a turboprop, you are probably going to spend just as much for the setup as you would for a turbofan, and get about the same fuel burn, so why not go with the turbofan which has less moving parts, less overall cost, since both a turboprop engine and a turbofan will need hot section inspections done, but the turboprop will also need prop overhauls done.

[JCP]

1) APU turbine would run at constant speed, at original design speed.
"Throttle" would vary fan pitch, APU's fuel control system servo holds RPM constant. Throttle (fan pitch) has to limit upon max exhaust temperature.

2) From the pointy end going aft: Cockpit, Inlet Duct, Fan, Stator blades-Gearing-Auxiliaries, Turbine.  Hence Turbine (about 12" in diameter) is in center of exhaust duct, with exhaust aimed aft.

Somewhere I've read that a T63-T32 exhaust (running as originally designed) yields 40 lbs thrust.  May have been on a helicopter page...

Any idea of how much thrust heat of hot exhaust would add, if mixed with ducted fan air stream before exiting ?  A lot of energy in hot exhaust,  expanding ducted fan stream volume and thus increasing velocity.

John