# Turbo Charger Jet?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by death31313, Mar 29, 2010.

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1. Mar 29, 2010

### death31313

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I've been looking for jet engines to power an aircraft I've been trying to design and I stumbled accross multiple sets of plans for turning two turbochargers into a turbo jet engine. now im sure you have all probibly seen them and could probibly give me some answers. first I would like to ask, If constructed from quality parts, could a turbocharger jet work in an aircraft? Whats the reliability like? how much thrust do they put out? I'm Know they aren't ideal but would they work? thoughts and advice are welcome as always.

Last edited: Mar 29, 2010
2. Mar 29, 2010

### Bart

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Well, for sake of discussion, suppose one of those units would work fabulously, for $5 total cost. But, you'd still be stuck with the fact that fuel/air ratio needs to be something like ~13-14:1 to burn properly. The more air sucked & blown through the pipe, the more you gotta pay for gas. Such turbines suck a LOT of air, so to keep burning you gotta buy and carry aloft a LOT of gas, at ~ 6 lbs./gallon and ~$6/gallon. What you save in engine weight you'll generally wind up carrying in extra fuel, heavy and expensive. So, the uber-light \$5 engine might mean the plane is not so light and cheap, after all.

I'm exaggerating for effect, obviously, to make a point about life-cycle cost and efficiency.

Thoughts?

3. Mar 30, 2010

### Lucrum

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It's an interesting idea. But I'm inclined to think reality will (as usual) get in the way. While simple in theory, in practice a reliable and controllable turbine engine is fairly complex. It's one thing to have a novelty running on your driveway and a whole other to get one reliably working in the confines of an airframe. What about engine driven accessories? How do you drive them? What about over speed protection and fuel control?

Truth be known I'm as big a dreamer as anyone here. And I'd love to see someone with the turbine knowledge, machining capabilities and of course MONEY successfully put something like this together.

But I have my doubts.

4. Mar 30, 2010

### Dan Thomas

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Turbochargers typically generate only low pressures, perhaps no more than 20 or 25 psi. The compressor of a jet generates as much as 350 psi. More squeeze means more power, so a turbo isn't going to give much at all. Turbos are small-diameter centrifugal compressors that have to spin at terrific speeds to do their jobs. Most turbine engines have considerable larger compressor diameters and still have to spin at terrific speeds.

Dan

5. Mar 30, 2010

### death31313

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the basics behind how a turbocharger Jet works is there are two turbos these are conected by piping wich serves as the combustion chamber. the blades of these turbos are attached by some sort of rod. One turbo takes in air compresses it in the combustion chamber and a spark plug ignites a fuel mixed with the compressed air. The ignition of this fuel causes a increse in pressure and sends that pressure out through the other turbo wich spins that turboes blades there by spining the blades of the intake turbo and the cycle repeats. they are throtialible by regulating the amount of fuel intake these jets have become somewhat popular with jet enthusiasts and has even been built on an episode of Junkyard Wars, but as far as I know, no one has put one on an airplane. I supose I should have described the turbocharger jet engine a little better for those who didn't know what i was talking about. (please excuse the spelling in this post, the computer im using has no spell check)

6. Mar 30, 2010

### Sir Joab

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I've seen these things too, but I think they generally only use 1 turbocharger. A turbocharger on a car has a turbine through which the engine's exhaust flows which in turn drives the intake turbine which compresses the fuel/air mixture and forces it into the engine. A turbocharger-jet simply replaces the automotive engine with a combustion chamber.

My personal doubt about it's viability would be the engine's power-to-weight ratio. Here's a video of a very nice engine on youtube, but notice that the operator stops the engine from rolling on it's stand at full power by bracing his foot against it while sitting on a rolling chair...

I personally have been intrigued at the idea of building a plane powered by a Pulsejet... but that's another story.

7. Mar 30, 2010

### Dana

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Turbocharger jets are popular ("popular" being relative, of course) among hobbyists, bur as a curiosity, nothing more. Oh, some may have stuck them on bicycles or go-karts, but that's about it. Most car turbochargers are quite small compared to even the smallest jet engines. About 30 years ago I read in Aviation Week that Garrett was working with a jet adapted from a large truck turbocharger for drone applications, but I don't know what came of it.

Also they're heavy... turbos typically have bodies made of cast iron, not the stainless steel and Inconel of an aircraft turbine engine.

If you want to build a jet engine for its own sake, go for it. If you want an engine for a practical airplane, look elsewhere.

-Dana

8. Mar 30, 2010

### Dan Thomas

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It doesn't increase pressure. It increases volume and velocity, which actually cause a drop in pressure. If the pressure rose, it would backfire through the compressor and stop the engine.

Dan

Last edited: Mar 30, 2010
9. Mar 30, 2010

### Bart

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I hope you and your neighbors and all your dogs like noise. Lots of noise. To get adequate thrust outta that tiny little exhaust port, the narrow thrust column has to be uber-fast. Uber-fast = uber-noisy, shear between the thrust column and the surrounding air being what it is.

This is exactly opposite the direction of jet engine development since the mid-1950s. Everybody else wants a much larger diameter and therefore more efficient thrust column,with less shear and therefore less noise.

Personally, I like the silence of the YO-3, uber-quiet 6 blade fan driven by muffled recip engine. Scale that down and sneak up on the wildlife.

10. Mar 30, 2010

### death31313

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you all have valid points and it was pretty much what I was expecting to hear. they would probably work on a very, very light airplane (possibly a PPG) it could work in theory. i would still like to build one just for the coolness factor though.

11. Apr 1, 2010

### Von Richter

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I built a few jet engines out of the model 61 and 71 turbos and got as much as 150# thrust, but it was quite a bulky mess. I've been looking for a ducted fan that I could use with one of my ultra lightweight V6 160# 250HP @ 7200 RPM 2 cycle converted outboard engines. At 3# thrust per HP that would rate 750# thrust per engine. That would result in 1500# thrust with a scale size F-15 or Phantom F-4. What a ride, ehhh?

12. Apr 2, 2010

### sohosh

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i too have been loking into these and i think that a pulse jet is a beter jet to experiment with, but i would only have these pupies as a secondary propulsion.​

here are some links to some basic rigs!!!

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13. Apr 3, 2010

### Sir Joab

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Though I've never been big fan of the Lockwood style pulsejets. Their simplicity is undeniable, but they have to intake in the opposite direction as the direction of flight, so the faster you go the less thrust you'll have.

On the other hand, the type with valves (like on the V1 "Buzz Bomb") have longevity issues. The "reed" type valves can only take so many cycles, especially at the temperatures they reach. I've always been curious about how well it would work if someone were to build a pulsejet using automotive "poppet" valves...

14. Apr 3, 2010

### Lucrum

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There are a number of valveless pulse jets configurations.
Fuel consumption is supposedly atrocious though.

15. Apr 4, 2010

### Bart

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Dick Schreder of sailplane kit fame had a pulsejet-driven propeller he was working on about 25 years ago. Equivalent to 50 hp on 8 lbs.

The hub and prop were hollow, with the combustion chamber in the hub and the expanding combustion gases going out through nozzles at the prop tips. This was clever, since the long lever arm of the prop meant the tip had the most leverage to rotate the prop, the speed of which was pretty compatible with the exhaust gas velocity. Fuel came in via hollow bearing shaft at the hub, cooling the bearings in the process.

A Ford Model A magneto was self-generated by rotation of the prop, with a simple ignition system as the spark plug(s) were into the hub, which assy. rotated past the contacts: Hub = rotor cap.

NOISE was a major problem, and I don't think Dick ever sorted that out. Also the usual problems of valving, and I have no idea how he dealt with that, but a V-1 type pulse jet buzz bomb flapper valve may have caused a lot of the noise. Wrote to him about it, got no reply. Perhaps some sort of valveless system alluded to in one of the posts above would have worked. Who knows?

One can imagine prop tip nozzles which impinge on the tip vortices in favorable way, to increase thrust efficiency while reducing noise and vortices.

Dick Schreder got sick and later died. He told us he'd not patented the idea, for fear that the 17 year lifespan of his patent would run out, so he carefully documented his work with the idea of deferring the patent statute of limitations until his design was perfected. I don't know what happened with this.

The idea has great merit: Very light prop, no torsional stresses, application of torque energy input where is does most good (tip) rather than at the point of least torque (hub). Think: wrench vs. screwdriver.

With such a light prop, you could put them pretty much anywhere on the airplane, free of the need for major (heavy) structure.

16. Apr 4, 2010

### ARP

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Bart,

Many years ago ( more than 25) I remember seeing a jet propeller in the aeronautical section of the London Science Museum. The air intake was at the hub with combustion in the hollow blade and the exhaust went out at the tip. I think the concept is very old so I do not think Dick Schreder could have got a patent on the invention. He may have refined the device and improved on it but not the original inventor. Many ideas do get rediscovered but "prior art" would fail any patent application.

Tony

17. Apr 5, 2010

### Bart

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Thanks, Tony, that makes sense.

Still, the idea is fascinating, given apparent compatibility between rotational tip speed and nozzle exhaust speed, and the advantage of putting the energy at the tip, where it has most leverage.

Alas, if only this thing could be made quiet, fuel efficient, and cheap....

Maybe jet the exhaust out through a narrow slot, Coanda lip, etc. right where it would offset the pesky tip vortex.

18. Apr 5, 2010

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