Electric Hybrid Turbine

[cudabean]

I've been thinking about this idea for a couple of years and started to accumulate materials to conduct some experiments, but other things have taken priority.

The idea is to create a high-bypass axial-flow turbofan engine that uses electricity to rotate the compressor. Then you rig the turbine(s) with generators. Other features--no stators, just counter-rotating stages for compressors and turbines. Advantages of multi-spool turbines can be realized without the complexity of multiple spools operating concentrically.
Another idea is to have the electric motor or generator exist at the outside, i.e. have magnets be located at the tips of the fan blades and have the coils (which are stationary) be located in the engine casing. I'm thinking of using coreless coils (typical electric motors use wire wrapped around a ferous core. Coreless motors also use a coil, but the coil is wrapped around a light non-conductor).

Here are the advantages:
1. No stators--you counter-rotate succesive stages.
2. No variable pitch required. Instead pressure sensors adjust power to each compressor stage according to its need.
3. Simplicity.
4. Ability to easily control the engine's operation via computer.

Here are some challenges:
1. Need to avoid heating permanent magnets due to Curie point. Possible solution might be to use electromagnets in the turbine.
2. Coils for neighboring stages would likely interfere with each other.
3. Not sure if the electric motors can be easily made within the space limitations that are powerful enough to suit the engine's needs. Same applies to the turbine generator.

Marlin

[skyfrog]

Other features--no stators, just counter-rotating stages for compressors and turbines. Advantages of multi-spool turbines can be realized without the complexity of multiple spools operating concentrically.

Hi Marlin,

Could you sketch some drawings to illustrate your idea, as a picture is worth a thousand words.

In short, I do not understand the whole idea by simply reading :-(

[cudabean]

Could you sketch some drawings to illustrate your idea, as a picture is worth a thousand words.

Sure Horace, be happy to. Check back in about six hours (I should have time to put something up).

Marlin

[cudabean]

Here's a diagram of what I'm talking about. Each stage is mounted on a stationary central spindle and rotates on it's own set of bearings.

Does that clear up what I'm talking about Horace?

Marlin

[El-Kablooey]

huh, definately different! You will certainly need a VERY good cooling system for the turbine though.

[Johansson]

Have you thought about how the compressor stage bearings should be fitted? With counter rotating stages close to each other it will be tricky to fit bearings the normal way, but perhaps a single shaft running through the entire engine could work. Each compressor wheel gets a single bearing inside it so when spinning it is the outer race that moves and the inner is fixed.

Another way of doing it is of course by using electro-magnetic bearings since it is an electrical turbine. A bit more work though... *smile*

The coil will surely have to endure much stress if it is meant to sit on the outside of the turbine wheel, both heat and centrifugal forces affecting it. A very interesting project though!

//Anders

[Zippiot]

So as it spins it creates electricity?
Wicked idea would save space on starters, especially if it can be fitted to r/c sized turbines.
What if you incorperate a type of generatore between each stage? So as they counter-rotate they generate buttloads of electricity (you can never have too much).

[El-Kablooey]

So as it spins it creates electricity?
Wicked idea would save space on starters, especially if it can be fitted to r/c sized turbines.
What if you incorperate a type of generatore between each stage? So as they counter-rotate they generate buttloads of electricity (you can never have too much).

because it would use more electricity than it generated.

[cudabean]

Another way of doing it is of course by using electro-magnetic bearings since it is an electrical turbine. A bit more work though... *smile*

Yes, magnetic bearings would be neat. If feasible, it would eliminate the need for an oil system.

The coil will surely have to endure much stress if it is meant to sit on the outside of the turbine wheel, both heat and centrifugal forces affecting it. A very interesting project though!

Actually, the coil is stationary and the magnets are in motion. But the magnets will suffer the effects of heat and centrifugal force which will be substantial.

Marlin

[pezman]

Kind of a cool idea. Not sure that you'd need permanent magnets on the compressors -- you should be able to get motive force using field coils alone. I think even the generator back by the turbine can be self-exciting.

Also, maybe putting the motors in the center would be better. As you get more and more stages, the center axis should get larger since more compression=less volume. It seems that you could use some of this increase in shaft diameter to keep the electronics at each stage progressively farther away from the ever increasing heat.

[skyfrog]

Here's a diagram of what I'm talking about. Each stage is mounted on a stationary central spindle and rotates on it's own set of bearings.

Does that clear up what I'm talking about Horace?

Marlin

Hi Marlin,

Thanks, now it's clearer for my perception your idea. I do hope any new innovative ideas can be gone into practice and get some advantages over old designs.

The power needed to drive the compressors are from electrical this might works however it subject to mechanical energy conversion losses, while for the conventional design there is no such problems. Here's a analog of such losses : conventional design is like face to face deal in the market, the seller gets exactly the same amount of money from the buyer. While for electrical systems buyer pay through PayXXX, seller get noticable smaller amount of payment that is the loss.

No stator is another problem, between stages we do need stators to guide the air in correct angle before enter next stage. It's all for better efficiency in compression.

[NickC]

yeah, the efficiency would be a big problem. you lose so much energy converting the kinetic to electric and then electric back to kinetic.