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-   -   Air driven turbine for generator and flywheel? (http://www.physicsforums.com/showthread.php?t=206100)

 stilbo Dec26-07 08:57 PM

Air driven turbine for generator and flywheel?

Hello... new to forum....

I am looking into design of a forced air turbine that will drive a generator and flywheel. The flywheel would be utilized for short periods of zero air supply and as an energy resevoir to maintain revs at an optimum level.

Dimensions: Turbine/AC generator/flywheel = approximately 450 mm dia. x 900 mm hgt.

Air feed : Volume? = velocity = 100 Kph; inlet area = 1800 mm x 600 mm reduced to a variable orfice/nozzle (?) at turbine inlet. I'm also curious as to what the force of this pressurized stream would be. I'm not familiar with the calculations to derive CFM from my aformentioned dimensional constraints but I would guess that they would need to be determined in order to carry out the following work.

Generator : synchronous-type alternating current (ac) generator that rotates at high speeds up to 10,000 rpm. Will need to produce 500 V and power output of 30 kw. Rotor weight would be approximately 15 -18 Kg. I may be able to source this generator "off the shelf".

Flywheel : Should be of sufficient mass to sustain rotor at 3,000 rpm for 5- 25 minutes.
Weight = ?

There will be a DC start up motor for the flywheel at start.

I guess my primary question is what type of turbine am I looking for?

I'd like to orient this assembly in a vertical stack.

Oh..... would magnetic bearings help efficiency? Would this magnetic levitation create a great deal of parasitic loss to output?

I won't need a lot of torque (hopefully) as that is what I propose as the flywheel's function, i.e. : a damper for torque loads and to maintain some rpm. But I do want to sustain rpm via air flow.

Would a multi vane, multi stage turbine somewhat akin to a power plant steam generator on a small scale be the ideal design?

My background is in applied high energy physics and I remember that turbo molecular pumps had a very high efficiency, granted, at ultra low inlet densities. I tend to think of these little guys because they were compact, vertical, multi stage units....

Thanks!

Ron S.

 greatglory Nov29-08 12:55 AM

Re: Air driven turbine for generator and flywheel?

I read your post with interest earlier this year and have since bought the domain name flywheelgenerator.com My design is very rudimentary using as it were a model airplane ramjet to spin the turbine. The ram jet would be powered by methane gas from chickens, cows, people and pets. As I figure it this system could produce increasing amounts of energy indefinately as the methane would be a constant feed into the ram jet, spinning the flywheel faster and faster until the limit of the flywheel was reached. The ultimate limiting factor being the tolerances of the system.

http://api.ning.com/files/z23LVafEV*...425&height=313

Think of it as if the ram jet were a thruster on a space craft. Especially if the flywheel is suspended in a magnetic vacuum thereby eliminating most friction. If my elementary physics is correct the flywheel will keep accelerating if the "burn" is constant, remember we are in a "space-like vacuum." The end result is that a very small ram jet can ultimately spin the Tocomack flywheel generator with ease. It may take years to get it up to speed but the tocomack will give out before either the supply of methane or a properly maintained system of ram jets.

 Rossco Jun18-09 04:50 PM

Re: Air driven turbine for generator and flywheel?

Generator Speeds are defined by the frequency. Standard 60hz Single Phase Alternator, meaning one that generates 1 cycle per revolution would turn at 3600 RPM. Most large generators have multiple phases so that a single revolution will produce 2 or more power cycles. So a 2 phase alternator would need to turn at 1800 RPM. With recent interest in this, I have found that typical Air Motors do not have a high RPM range anyway. Hope this steers your calculations a bit. It would be really cool if the Di Pietro Air Motor was available, but it looks like he is going to keep it from us so that he maximizes profit, but its worth a look at Engineair in Australia. Dynatek of Calgary Alberta is the world leader in compressed gas storage and sell vessels capable of 5000 psi and is working on getting to 10000 psi - pretty impressive ! (I've toured the plant with interest in H2 storage for a past transportation initiative). A typical small vessel capable of 5000 psi would run about \$2500 which is pretty reasonable - these are aluminum wrapped in carbon fiber. Now all you need is a manifold, valves, pressure transducer, micro controller, regulator to throttle the output air to the air motor, and a compressor to complete the package.

 Bob S Jun18-09 05:55 PM

Re: Air driven turbine for generator and flywheel?

Ron-
If you have a forced air velocity of 100 kph = 27.8 meters per sec, and an inlet area of 1.8 meters x 0.6 meters, the air wind power is
Pw = (1/2)ρAv3 = 15,000 watts, where
ρ=air density = 1.29 Kg/m3
A= area = 1.8 x 0.6 = 1.08 m2
v=27.8 m/sec

I would be surprised if you can get more than 5,000 watts out of this if the air is not pressurized (p = 1 bar).
Bob S

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 Integral Jun18-09 08:36 PM

Re: Air driven turbine for generator and flywheel?

note that the OP (Ron) has not been active for 18months.