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Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 06:34am 11 May 2008
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When I originally bought this turbo brand new, it was the largest variable vane turbo available in Australia. It was off a Nissan Patrol 4WD which has a fairly enormous four litre capacity engine,
Smaller versions of this same exact Garrett turbo, come on the mass produced Mercedes (small capacity) commercial turbo diesels (Sprinter and Vito commercial vans) and also on many (but not all) of the SAAB family of turbo cars.
Finding something smaller should be no problem at all.
But remember, you can close the vanes right off, or run the turbine almost completely shut, so it will then flow almost nothing at very high velocity. The impeller generates torque from every blade all the way around the rotor, unlike a Pelton wheel that works on only one bucket at a time.
As water is 874 times as dense as air, and even denser than hot expanded exhaust gas, the torque generated will be huge in comparison, even with the small diameter rotor.
Don't let the inlet and outlet size fool you. With the vanes almost fully closed against each other, the high velocity flow area onto the rotor can be made very small indeed. Down to twelve pin holes tangentially driving the eleven turbine blades.
As the vanes are opened, torque increases with mass flow. That is how these machines operate at very high efficiency over a wide flow/torque range. You only use as much water as you need to do the job. The vane lever is like a sort of "throttle", more flow equals more torque, but more water "fuel" is consumed.
With the vanes fully cosed, the turbine will stop, and so will flow.
Edited by Warpspeed 2008-05-12Cheers, Tony.
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 07:07am 11 May 2008
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MMmmmm, will have to put the lean on a few mates that are into the auto scene to find one of those Garret Turbos for me. What might a typical wrecker price be I wonder? As you say it seems easy enough with the power potential and efficiency high as well.
It's the pressure to flow ratio that is the big question for me. Same as Volts and Amps in an electrical device. I understand that the flow can be varied over a large range so I'm hoping this is all that is needed. The thing I keep thinking of is logging the turbines max potential where all I should be trying for it's max potential from my site. Yes the wicket gate will do that. Dam... another project.was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 08:30am 11 May 2008
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I have never priced one of these turbos secondhand, but a wild guess might be around $300 for a perfectly good one in fully working condition. But a problem turbo not in perfectly good condition, that needs a rebuild might be worth more like $80.
You do not need a prime turbo that is perfectly balanced to run at 100,000+ rpm, or has no oil leaks. As you are going to pack it with waterproof marine grease and run it at a maybe 1,500 rpm maximum, a perfectly good replacement turbo is definitely not needed.
Sometimes the vanes are jammed solid, which is another reason it may go very cheap. Dismantling it and digging out the crusty exhaust deposits will free the vanes up, and fully restore it to full functionality for mini hydro use,
Another cause for doubt is bearing wear. See if the shaft has any side play. Maybe 1mm or 2mm side play or wobble that you can easily see/feel would mean the bearings are essentially worn out. That would normally mean a full rebuild. But as long as the wheels do not actually scrape inside the housing, it will work fine for us !!! A great bargaining position if the rotors wobble.
These turbos run red hot or even white hot inside, the moving parts are made from very hard tough high temperature stainless steels that will never erode or oxidize (like engine exhaust valves). They certainly will never rust! But they can build up exhaust deposits that can sometimes jam the vane mechanism in high mileage engines. Although jammed solid, nothing is actually really damaged. There are a lot of closely fitting sliding parts inside that can easily jam the vane movement when filled with crusty exhaust grunge.
Best go around to a Mercedes commercial van wrecker and ask if they have any stuffed Garret VNT turbochargers that need a rebuild you can look at. Nissan 4WD or SAAB wreckers may be worth checking out too.
If the rotors turn freely, that is all you really need, if it pisses oil, the bearings are worn, or the vanes are stuck, you can live with that. Tell them you want to use it as a cut away demonstration turbo model for a trade school project or something, and he may possibly be really glad to get rid of a turbo he cannot sell to anyone else as a decent working replacement turbo.
Just wander around there, look really poor, and say you want to look at any REALLY CHEAP Garret VNT turbos in any condition, and see what they have to offer. As long as the wheels turn freely without scraping, that is all you really need.
But make absolutely sure it really has the movable vanes! All Garret VNT turbos have these vanes, but the majority of turbos out there do not. You can tell for sure by the location of the control lever.
Here is what you are looking for. The pencil shows the vane operating lever. Note that it is located right behind the turbine, and the lever shaft is PARALLEL with the turbine shaft. The toggle that moves the vans is shown by the biro.
Below is a typical "normal" turbo without the movable vanes THAT IS USELESS AS A MINI HYDRO. It has no vanes, but a flap valve to bypass the turbine. 99% of all turbos are like this so beware.
These have a similar looking control lever indicated by the pencil, but the lever shaft is AT RIGHT ANGLES to the turbine shaft. The internal flapper bypass valve is indicated by the biro.
Edited by Warpspeed 2008-05-12Cheers, Tony.
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 10:09am 11 May 2008
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Ah great Tony, that's a big help. A mate has one for me to look at this week so at least I can make like an expert knowing the key thing to look for.
With the rebuild for these things, the mate just had one done for $1,500 or $1,800, but just packing and putting in a set of bearings, is that something I could do at home or would it be like say a water pump and need pressing and special tools? They don't sound like they're designed for thebackshed operator.
Still, "What ever can't be fixed with a hammer is an electrical problem." Edited by Gill 2008-05-12was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 10:36am 11 May 2008
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The bearings are simple bronze sleeve bearings held into the main housing by circlips. You can buy these bearings as spare parts, or even turn up a pair on the lathe yourself at home from a solid lump of bearing bronze. They are nothing at all special.
A proper rebuild is a big job with disassembly, cleaning, inspection, replacing bearings and seals, rebalancing within very fine limits, and reassembly. It is expensive because of the time, parts, skill, and the specialized balancing equipment necessary to do the job properly to aerospace quality.
We are building a low rpm, cold running water turbine, not a 100,000+ rpm turbo that has to run red hot for years or hundreds of thousands of miles in a commercial vehicle.
Any old variable vane turbo can be pulled apart, cleaned out, greased, and it should I expect work fine as a mini hydro for years if not decades without attention. It would probably blow up in a week if used as a turbocharger, but that is not what we are using it for.
What makes turbos really special are the very high temperatures, and the extremely high Rpm at which they normally need to run.Cheers, Tony.
Just a quick question...Did anyone actualy make a hydro with one of these turbos?"Imagination is greater than knowledge" Albert Einstien
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 10:19am 06 Oct 2008
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Ken,
I have not seen any comment in any post to indicate someone has attempted one. Personally, I'm still keeping an eye out should one pass my way as it seems well worth a try, but no luck yet.
If you can get hold of one to try please let us know how it goes. was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
Hi Gill,
thanks for your reply. I've built a few hydros with turgo runners. The size of the runner in a turbo looks very small meaning high rpm and low torque. I guess this would be more of a xflow turbine and so subject to a whole different set of rules which I have no experience in. I'll admit to having thought about the possibility of using turbos myself but it looked to me that they would require a lot of water and the efficiency losses due to turbulence going through the vanes would make it unattractive. I look forward to being educated when someone actualy tries it. "Imagination is greater than knowledge" Albert Einstien
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 10:20am 08 Oct 2008
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Ken,
I can't agree with you there as when you get up to Snowy Hydro Scheme size they do not use Turgo or Pelton runners but turbines very much resembling those we see in vehicles. I think it is the very complex shape that precludes them from DIY manufacture and not inefficiency/turbulence. But as you say, it really needs to be tried before we can praise or condemn. was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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