EDF Afterburner

[Neil1993]

So I saw this video a while back about a crazy Swedish guy who made an RC airplane with an afterburner. What I was curious about, is how much this could actually be used to increase thrust. I'm probably going to try simulating it in 2D on my own soon, but if anyone knows of a similar project, could you please point me in the right direction?

I'll keep you all apprised of my progress.

(here's the video)

[Nuke]

its pretty much a jet engine with an electric compressor.

[Neil1993]

its pretty much a jet engine with an electric compressor.

yeah. But the one in the video doesn't look like it would really get much thrust. I don't think the nozzle converges enough to make it much more than a showpiece.

[dharak1]

I watch flite test pretty often and have always been a fan, I liked the rocket planes they did a while back and figured I would take it one step higher and I took an airhogs titan, put two C6-5s on it and launched it. It went pretty far. My next step is putting some RC stuff on it so I can control the flight. Back to the afterburner, I wouldn't expect it to speed the plane up by much or even increase thrust. It did seem to get a bit of a speed boost in the video though so I'm probably wrong.

[MaverickSawyer]

The Italians experimented with this before WWII... Despite an ungodly jump in fuel consumption, there wasn't any speed benefit.

That said, it looks badass. DO. WANT. PLANS. NOW.

[Neil1993]

I watch flite test pretty often and have always been a fan, I liked the rocket planes they did a while back and figured I would take it one step higher and I took an airhogs titan, put two C6-5s on it and launched it. It went pretty far. My next step is putting some RC stuff on it so I can control the flight. Back to the afterburner, I wouldn't expect it to speed the plane up by much or even increase thrust. It did seem to get a bit of a speed boost in the video though so I'm probably wrong.

Cool experiment with the airhog!

I, personally, can't really tell if it gets a speed boost. There's nothing to create a frame of reference when he ignites the afterburner.

In the end, myself and some friends are hoping to use this concept to make a high speed RC plane. Maybe even one that can pass Mach 1, but that's still a long way off.

[Nuke]

yeah. But the one in the video doesn't look like it would really get much thrust. I don't think the nozzle converges enough to make it much more than a showpiece.

he mentioned that it was only like a 15% increase in thrust. it definitely does need a better nozzle. that would increase the combustion chamber pressure and facilitate better combustion. the fuel preheater is a nice touch. but i think id run it just to start the engine, then wrap the tube around the end of the nozzel, so after ignition engine exaust takes over the job of preheating. tazer for ignition was probibly also overkill, you could have probibly gotten away with an electric bbq igniter and save some weight (id build my own boost converter).

[Neil1993]

I just found this paper which helps with the calculation of the EDF's output parameters. This is a pretty good place to start my calculations

http://southamptonmac.org.uk/doc/RS_EDF_theory_and_Practice_v5.pdf

[Neil1993]

Using the previous calculation, I estimated an exhaust velocity of approximately 174 m/s coming from the EDF (assuming the plane has an airspeed of 25 m/s). I can use this to create the final simulation.

One last thing before I continue; I was considering using Butane, like the guy in the video. Would something else work better? Like maybe propane or methanol?

[Nuke]

butane kinda works because the fuel comes pressurized so you dont have to deal with much more than opening the valve. though the metal can doesn't help you in the weight department. you might be able to use liquid fuel with a atomizer nozzle. low pressure behind the nozzle might be enough to draw out the liquid on its own with the venturi effect. provide a bit of turbulent air to improve fuel mixing. you could eliminate the valve control at the expense of bleeding fuel at takeoff. you might also have a servo pinch the line closed (which would give you a small degree of throttle control on the burner).

preheating the fuel no matter what it is will definately aid in combustion. what i would do is have a 2 stage heater, stage one would just be a low value resistor (quarter watt carbon outta do fine) wrapped with metal tubing and apply heat shrink, then do a second stage using heat recovered from the nozzel, power the resistor as part of the startup procedure, then let the engine waste heat take over from there.

im also wondering if a tandem edf config would work, have a large edf up front and a smaller one in back, this should increase the pressure in the combustion chamber a little bit more, which combined with preheated fuel, will help your ignition. the whole thing needs to be in a sealed tube so that all the thrust goes out the tailpipe. all you need is some beer cans.

Edited September 29, 2014 by Nuke

[Neil1993]

butane kinda works because the fuel comes pressurized so you dont have to deal with much more than opening the valve. though the metal can doesn't help you in the weight department. you might be able to use liquid fuel with a atomizer nozzle. low pressure behind the nozzle might be enough to draw out the liquid on its own with the venturi effect. provide a bit of turbulent air to improve fuel mixing. you could eliminate the valve control at the expense of bleeding fuel at takeoff. you might also have a servo pinch the line closed (which would give you a small degree of throttle control on the burner).

preheating the fuel no matter what it is will definately aid in combustion. what i would do is have a 2 stage heater, stage one would just be a low value resistor (quarter watt carbon outta do fine) wrapped with metal tubing and apply heat shrink, then do a second stage using heat recovered from the nozzel, power the resistor as part of the startup procedure, then let the engine waste heat take over from there.

im also wondering if a tandem edf config would work, have a large edf up front and a smaller one in back, this should increase the pressure in the combustion chamber a little bit more, which combined with preheated fuel, will help your ignition. the whole thing needs to be in a sealed tube so that all the thrust goes out the tailpipe. all you need is some beer cans.

I'll get there eventually. First I need to do all the initial simulations. I might be able to do that tonight (if I can finish all my homework in time). Whatever the case, I'm not about to use beer cans for the combustion chamber. I'll try to get some aluminum or stainless steel.