Very simple pulse turbine

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krzys Mnich
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Very simple pulse turbine

Post by krzys Mnich » Thu Sep 10, 2009 12:14 pm

Hi,

this is so simple, that somebody must have tried it...
pultur.jpg
There's nothing but a simple vane rotor in a chamber. The rotor works as a rotary valve, then it forms closed combustion chambers, and at last it works as a primitive turbine.
One can't expect great efficiency, but the simplicity is amazing. On the other hand, I've made some calculations, and the theoretical efficiency proved to be surprisingly good, if the rotor has many blades - up to 25% for 100 blades at 10000rpm.
I could make some stupid mistake, however...

regards

krzys

Mike Everman
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Re: Very simple pulse turbine

Post by Mike Everman » Sat Sep 12, 2009 2:25 pm

Neat concept. Looks to me like the reaction to exhausting would make CCW torque, though.
Mike
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vturbine
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Re: Very simple pulse turbine

Post by vturbine » Sat Sep 12, 2009 8:29 pm

The low pressure area is outside of the chambers, so none of them will eject into the next chamber like the brown arrows show. Instead, almost all flow will follow the outside path. Also as Mike says there will be a reaction at each chamber to push the rotor counterclockwise, however there will also be clockwise friction at the vane edge if the gas flow is clockwise. It may not do much, therefore, or may as he says try to run counterclockwise -- which will not be possible, since the cycle is designed clockwise. Rotor end sealing will be difficult, as will an ignition source which remains stationary, and outside of the buckets -- since any axial protrusion would be cut off. There is no clear means of compression in the buckets prior to ignition...

On the other hand all of this negative theorizing might be totally incorrect! Or you may have ways to overcome any proposed difficulty. :D
No problem is too small or trivial if we can really do something about it.

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krzys Mnich
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Re: Very simple pulse turbine

Post by krzys Mnich » Sun Sep 13, 2009 8:10 am

vturbine wrote:The low pressure area is outside of the chambers, so none of them will eject into the next chamber like the brown arrows show. Instead, almost all flow will follow the outside path.
Yes, I suspected my stupid mistake.
The flow like the brown arrows can happen for the outer area much smaller than the vane area. That's true for the first few stages, but next the "leakage" must grow, due to the compressibility of the gas. Finally it will be several times bigger than the vane area, so you can expect nothing but the friction force there. Pity.

You can utilize the high pressure after the first few steps, by another turbine, or by pressure exchange, but that's no longer so simple.

regards

krzys

vturbine
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Re: Very simple pulse turbine

Post by vturbine » Sun Sep 13, 2009 11:56 pm

Yes, but what I theorized might not be true. There may be reasons outside of what anyone can anticipate that something might work.

Here's a contrary scenario. Spinning the rotor pressurizes the outer space.

Of course that might also fight against it working.

See, the only way to really know what happens is to build it and try it, and then observe what happens. It is not stupid, and you are not stupid, obviously. Even if it doesn't work. Because what you get out of that is a true understanding of why, and may also discover how to make some alternate idea work.

Unfortunately, this one is not so easy to build. The end seals probably need to be sliding seals and the method of injection and ignition worked out. Bearings and rotor milling will be required.

I would say that's the real problem, it's not actually constructionally simple, it is simple in design, which is different.

A Tesla disk turbine is a similar case of design simplicity, but constructional difficulty, despite the many who believe otherwise. A real working gas disk turbine must have dead true disks, controlled disk spacing, milled ports, star washers, rivets and precisely drilled holes and assembly, bearings, lubrication, seals, a combustion chamber, a nozzle and air induction, high temperature materials, and if efficiency is any concern, stages of additional disk rotors. In addition, multiples of the disks and associated components must be made, since rotors typically have 10 or 12 disk spaces.

Yes, the Tesla disk turbine can be described simply, but not so easily built.
No problem is too small or trivial if we can really do something about it.

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Ghrey
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Re: Very simple pulse turbine

Post by Ghrey » Tue Sep 15, 2009 1:15 am

You probably would not seals. Close .003 to .005 clearance on the closest approach would probably be fine, a minute cup in the end of the vein may be needed but I doubt it.

Also the enclosure would seem to need to spread slightly to the exhaust side, just slightly, expansion path and all...

The Major problem I see is that there is little or no compression of the charge so efficiency may be poor.

All speculation of corse, and likely wrong.


Reminds me of Wankel gone mad.

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