Piston engine with a ducted fan unit ?

[First time Juke]

I was wondering and having wondered it before...could it work..to have big piston engine running a 1 meter dia fan pushing a jet like aeroplane 600 mph ?

Technique or transmission here !



Could it work ?

[rampking]

Re: Piston engine with a ducted fan unit ?

It used an unusual setup of one Isotta-Fraschini radial piston engine to power a variable pitch ducted fan.

[First time Juke]

Re: Piston engine with a ducted fan unit ?

But that is not legal for racing is it ?

That has jet propulsion as well ???

http://en.wikipedia.org/wiki/Ducted_fan

[First time Juke]

Re: Piston engine with a ducted fan unit ?

This goes 260 mph with 650 hp..side by side trainer.

http://en.wikipedia.org/wiki/RFB_Fantrainer

Entire forward fuselage is before the fan unit ???

[First time Juke]

Re: Piston engine with a ducted fan unit ?

Oh man..they claim here 556 kmh ( 345 mph ) at 420 shp;

http://www.flugzeuginfo.net/acdata_php/acdata_fantrainer_en.php

http://www.youtube.com/watch?v=KkFZsz260cI

[First time Juke]

Re: Piston engine with a ducted fan unit ?

Here is one too;

http://www.fraseraerotechnologycompany.com/Rohr_2-175_Fan_Jet.html

[First time Juke]

Re: Piston engine with a ducted fan unit ?

I have nearly ludicrous speed reaching jet concept/design...I wonder if a two stage fan unit to really accelarate the airflow could be arranged for it in a 90% scale model ?

More about my mach 3.6 rocket interceptor here; http://max3fan.blogspot.fi/

[First time Juke]

Re: Piston engine with a ducted fan unit ?

Looks a bit different today.

[MIKE NIXON]

Re: Piston engine with a ducted fan unit ?

We looked at this back in the '80's.
With the engine (3,000 HP V-12) behind the fan you have major issues with the engine in the duct and how to shroud it. That brings engine access to the party. The pressure air in the duct give you a big increase in HP due to the ram effect. The drag is cooling the engine. A boiler system like Stelitto and Gost would work best. Exhaust would add to the thrust. Now add the aircraft and tanks holding 200 gal of fuel, water and ADI. Use a varible outlet to max the thrust and a varible pitch fan to complicate things and control the RPM of the engine.
The other choice would be to have the engine fwd of the fan with side inlets. Then the fan would need it own support bearings front and back as the engines are designed to pull not push. The bearing suport for the prop shaft is not going tro handle the load. However that make the engine access and changes easy.
I suppose you will want a cockpit and all that stuff.
Anyway I think its great that you are thinking out of the box. You and those like you are the future of this world.

[J.A.W.]

Re: Piston engine with a ducted fan unit ?

This Napier '500 mph' design 'from back in the day' may be of interest..

[..as is the Sabre vs R-2800 installation comparison..]

https://www.flightglobal.com/pdfarchive/view/1946/1946%20-%201443.html

[First time Juke]

Re: Piston engine with a ducted fan unit ?

This developed would be the only propeller driven mach 1.0+ contender with some ramjet thrust.

[GeoffS]

Re: Piston engine with a ducted fan unit ?

It's not clear from the diagram that your duct design would work well (i.e. no intake diffuser and the sharp bends in the downstream nozzle section).

I've always wondered if if would be possible to design a supersonic ducted fan without any fuel used outside the engine (i.e. nothing like the Campini-Caproni or MIG I-250).

You would need a normal-shock intake with a pretty large diffuser section to slow the free-stream velocity enough that the velocity at the fan face would be slow enough that the fan could accelerate the flow (i.e. add enough energy) still keeping the exit velocity subsonic. Add a convergent nozzle (maybe a convergent/divergent to maximize the efficiency?) at the exit to accelerate the flow back to supersonic.

I haven't done any calculations to see:

1. How large diameter would the exit of the diffuser have to be to decelerate the airflow enough.
2. What are the thermodynamics of the fan adding energy? (i.e. velocity, pressure, temperature) - maybe the input flow doesn't have to be as slow as I'm thinking of if we're adding enough energy in pressure and temperature.
3. What are the losses in practical diffuser/nozzle ducts?

The first item might kill the whole thing if the fan/fuselage cross-section would need to be too large...

Cheers,

Geoff S.

[First time Juke]

Re: Piston engine with a ducted fan unit ?

It's not clear from the diagram that your duct design would work well (i.e. no intake diffuser and the sharp bends in the downstream nozzle section).

I've always wondered if if would be possible to design a supersonic ducted fan without any fuel used outside the engine (i.e. nothing like the Campini-Caproni or MIG I-250).

You would need a normal-shock intake with a pretty large diffuser section to slow the free-stream velocity enough that the velocity at the fan face would be slow enough that the fan could accelerate the flow (i.e. add enough energy) still keeping the exit velocity subsonic. Add a convergent nozzle (maybe a convergent/divergent to maximize the efficiency?) at the exit to accelerate the flow back to supersonic.

I haven't done any calculations to see:

1. How large diameter would the exit of the diffuser have to be to decelerate the airflow enough.
2. What are the thermodynamics of the fan adding energy? (i.e. velocity, pressure, temperature) - maybe the input flow doesn't have to be as slow as I'm thinking of if we're adding enough energy in pressure and temperature.
3. What are the losses in practical diffuser/nozzle ducts?

The first item might kill the whole thing if the fan/fuselage cross-section would need to be too large...

Cheers,

Geoff S.

Hello Geoff !

It might need some nozzles yes etc, but the whole point is that a ram jet cannot operate at zero air speed...thus the fans would provide the airflow when the plane is stationary...once the craft gets moving and the ram is lit the fan blades are closed to zero aoa ( 5-7 blades for instance ).

Any better ?

rgds,

Juke

PS: Below the 1/72 scale model of the GM-1 stealth fighter..next step might be the fan inserted bigger model of it.

[GeoffS]

Re: Piston engine with a ducted fan unit ?

I'm actually talking about a system with no fuel burned downstream of the compressor/fan.
All the propulsion would come from energy added directly by the fan.

My gut tells me there's a thermodynamic reason it's impractical, but I haven't done the math...

You're basically talking about a simplified version of a hybrid turbojet/ramjet (like the J-58), with the fan taking the place of the turbojet: i.e. http://www.aerospaceweb.org/question...on/q0175.shtml

[GeoffS]

Re: Piston engine with a ducted fan unit ?

I'm actually talking about a system with no fuel burned downstream of the compressor/fan.
All the propulsion would come from energy added directly by the fan.

No surprise, it's actually been discussed a bit:

http://www.rcgroups.com/forums/showthread.php?t=999275

http://digital.library.unt.edu/ark:/67531/metadc58446/

(this paper uses a turbojet to drive the fan, but they discuss the fan thermodynamics)

http://www.flightglobal.com/pdfarchive/view/1950/1950%20-%201387.html

(this has some data on the power required to go supersonic: 5,000 to 10,000 HP at 50,000 ft).

http://books.google.com/books?id=YcAjcSSP4HMC&lpg=PA24&ots=WucLf1WEIT&dq=supersonic%20ducted%20fan&pg=PA24#v=onepage&q=supersonic%20ducted%20fan&f=false