Crazy idea of the day; circular saw blade exducer turbine?

[parkland]

So this might be a totally stupid idea.
In fact, it probably is.

I ran across this thread :

www.model-engineer.co.uk/forums/postings.asp?th=50777

And this video :

www.youtube.com/watch?v=OVlh7KDxcdg

And got to thinking, for a free power turbine, or steam turbine, asides the size and dimension, and materials, isn't it a fair argument that they are essentially
just a spinning wheel designed to turn gas velocity into shaft power?

I noticed that this gentleman’s steam turbine looks very much the shape of a tiny circular saw blade.
And then my saw blade free power turbine idea was born.
Is it an abortion waiting to happen? lol.

What I was thinking, is that several blades would be stacked, riveted together along the outer edges, then the center pieces of some of the blades would be
milled out on a lathe, leaving only the middle blade with the metal totally intact, and the hole in the centre for mounting.

So say 9 blades were used, all 9 would be held temporarily together with a bolt, to hold them in place perfectly.
Then, some holes would be drilled close to the edge, all the way around. Maybe 8 holes?
Then, rivets would be installed in the holes, so now all 9 blades would be permanently attached.

From here, the bolt could be removed from the hole in all the blades, and the riveted together blades would be put on a lathe.
On the lathe, a tool would be used to cut out the centre pieces of 4 blades on each side, to reduce weight.
Enough room would be left to not cut the rivets or too close to the rivet holes.
Once all the middle sections of the blades are cut out to reduce weight, the middle blade is left with the centre in, to mount it to a shaft.

Does this idea hold any water?
You can get blades for really cheap, and they come in many sizes!
I imagine the metal is on the harder side as well.
The blade tips can have little carbides on them, so maybe the blades would have to be staggered a bit?

What you guys think?
Would saw blades take the heat of a gas producer, and have any type of efficiency?


Heres a video too lol

www.youtube.com/watch?v=K1DqyJnfaU8

[racket]

Hi

Why try making a turbine wheel when they can be purchased on Ebay for quite modest amounts

www.ebay.com/itm/ROLLS-ROYCE-ALLISON-250-GAS-TURBINE-TURBOSHAFT-ENGINE-2ND-STAGE-WHEEL-23073854-/321525394070?hash=item4adc682a96&vxp=mtr

www.ebay.com/itm/Turbina-turbine-Wheel-Allison-C-18-C18-/261841723047?pt=LH_DefaultDomain_101&hash=item3cf6fb9ea7

A home made wheel can work but you need to be careful about rpm/tip speeds as the loadings become horrendous once past 10,000 rpm and things can "fly off" unless well constructed.

Cheers
John

[parkland]

Apr 14, 2015 21:33:06 GMT -5 racket said:

Hi

Why try making a turbine wheel when they can be purchased on Ebay for quite modest amounts

www.ebay.com/itm/ROLLS-ROYCE-ALLISON-250-GAS-TURBINE-TURBOSHAFT-ENGINE-2ND-STAGE-WHEEL-23073854-/321525394070?hash=item4adc682a96&vxp=mtr

www.ebay.com/itm/Turbina-turbine-Wheel-Allison-C-18-C18-/261841723047?pt=LH_DefaultDomain_101&hash=item3cf6fb9ea7

A home made wheel can work but you need to be careful about rpm/tip speeds as the loadings become horrendous once past 10,000 rpm and things can "fly off" unless well constructed.

Cheers
John

Are those that you posted from ebay, not for axial engines?

Personally, I think the blade idea is stupid in a way, but on the plus side, at least they are balanced, designed to spin, and a shape that maybe could work, without bending or welding the metal on
a home made design. A flat piece if steel without bends or welds should be about as strong as something could be under strong centrifugal force I think... ?

[racket]

Hi

Yep , we use them for freepower wheels on our DIY engines .

Cheers
John

[parkland]

OK Since this thread already has something as crazy as a saw blade turbine in it, can I throw another whacky idea in?

I know this sounds insane,
OK, what about using the suction of a gas producer engine, and using the suction to suck air through a power turbine?
The turbine could be made from even plastic.

I know the air velocity is much lower, but there are places on the turbo map where maybe it would work?
First thought that comes to mind, is that the exhaust velocity is wasted, but then again, it isn't, as it's spinning the whole shaft, creating
suction.... I dunno.


Certainly it would be cheaper and easier to deal with cool air than hot.

[racket]

Hi

It has been tried , but power production is rather limited as the pressure drop available before other problems start to appear is minimal , also theres less velocity produced per psi of pressure change with cold air vs hot gases, its a thermodynamics thing .

Much better to get hold of a decent freepower wheel and obtain full value from your engine .

Cheers
John

[parkland]

Apr 16, 2015 16:42:54 GMT -5 racket said:

Hi

It has been tried , but power production is rather limited as the pressure drop available before other problems start to appear is minimal , also theres less velocity produced per psi of pressure change with cold air vs hot gases, its a thermodynamics thing .

Much better to get hold of a decent freepower wheel and obtain full value from your engine .

Cheers
John

Hmmm very interesting!
As always, thanks for your thoughts!

[Johansson]

The first turboshaft RC helicopter used a suction power turbine made out of plywood, it was Kurt Schreckling who made it. He has written a book about his turboshaft experiments during the "good old days" which is very interesting reading.

[britishrocket]

Hello,

Anders you always seem to get my old grey matter working, even if it doesn't work all that well! I have looked at the model engineer forum post before, and I always thought that the turbine design presented was similar to this:-






This is the turbine of the turbo pump from the British Beta Rocket Motor, built in the late 40s at RAE Farnborough. It was designed to run on steam generated by decomposing hydrogen peroxide over a silver nitrate catalyst pack. You can see the inlet guide vanes machined into the opposite half of the casing. The Beta was the first turbopump rocket engine built in the UK.

Carl.

[parkland]

So if a suction turbine works that good, albeit not as great as a pressure driven turbine, is there hope?
I mean how bad is the performance?

On a mobile vehicle, the housing and weight and oil requirements of a big power turbine are a lot.
If you took that weight savings, and used a larger gas producer, (or suction producer lol), maybe it would
actually make sense?
I mean, if the suction turbine is all plastic and aluminum, with minimal oiling requirements.....


Hmmmm

[parkland]

Maybe several of these on a shaft, with plastic or aluminum stators, as a suction turbine:

www.aliexpress.com/item/Machine-Part-Black-Plastic-15mm-Inner-Diameter-8-Impeller-Motor-Fan-Blade/32296669607.html

Heres a guy sucking (he guesses) 800 cfm through smaller ones lol

www.youtube.com/watch?v=lFBw87shYr0

[racket]

Hi

LOL...........I guess you'll just have to build it and let us know how it works out ;-)

Cheers
John

[Johansson]

By all means build one, I would love to see a full size suction freepower build!

The parts could even be 3D printed in nylon, just make sure to make everything sturdy enough so it won´t drop a blade into the engine.

[parkland]

I was in the garage thinking a MAF sensor might work as a vane protector in case small pieces start flying into the gas producer / suction producer.
It has that alignment metal grid that seems to flow air really well.

at 7.22$ for a nice looking fan with free shipping, I wouldn't custom build a thing lol.

I was trying to translate a German web page, and I think that it said draft inlet turbine could only be 50% as much power as exhaust gas.
But I couldn't tell if that meant for the same fuel.
An later there was something about water, maybe they were talking about water turbines for all I knew.

Does anyone know where to look for such specifics?

If it was 50% of the power for still the same fuel usage, that isn't so very great.
On the flip side, a lot of weight would be saved, and power to run a 2nd oil pump, or larger oil pump, is reduced.
Plus I imagine the lighter weight of the power turbine would have a peppier response as well.

For the weight and room saved, a larger turbo could be used for the engine, and extra fuel could be stored.
Maybe this would be a perfect application for a VVT based turbocharger, as the vanes could be adjusted to take as much of the exhaust energy as
possible and put it into the shaft. Adjust them so any back pressure on gas producer causes a stall, so that it is trying as hard as possible to SUCK. lol