schrambo
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Joined: November 2016
Posts: 7 
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Post by schrambo on Nov 24, 2016 17:15:53 GMT -5
Hey guys, Just joined up and thought I would introduce myself - my name is Mitch and in my not-spare time I am a commissioning engineer for Siemens medium industrial gas turbines (SGT800 ~50MW) in Australia. Because I am a nerd I have decided I want to build my own mess-around DIY turbine with the ultimate aim of automating the control system just to prove I can! (I am lucky in that I might be able to score some free industrial controls from work  Incidentally if anyone has any questions Re: logic/control of large GT's I am more than happy to share (so long as its not protected IP!). So far I have got lucky and tracked down a cheap 4LGZ truck turbo I jumped on when it came up on ebay. Plan to spend some time cleaning it up a bit while I ponder the maths of the combustion chamber etc. In my mind there would be more with regard to turbo specification for oil flow rates/pressures floating around the internet but seems that either my turbo is too old (70's vintage) or this is not generally availiable. Can anyone recommend some trial and error methodology or rules of thumb for oil flow? Other than that I plan to keep it as simple as possible until I can wrap my head around it - I will continue to update this thread as I progress. Some great and crazy projects on here by the way - I love it! Cheers, M |
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Post by racket on Nov 24, 2016 18:31:29 GMT -5
Hi Mitch Welcome to the Group :-) Whereabout in Oz are you ?? Have a look here for some RoTs jetandturbineowners.proboards.com/thread/680/diy-turbines Its possible to get an engine working without having the actual turbo specs , some simple measuring of wheel sizes and scroll A/Rs will provide an idea of flows and if they parts are a reasonable match for making a GT . Looking forward to hearing more Cheers John |
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Post by jetjeff on Nov 25, 2016 9:04:31 GMT -5
Hi Mitch,
Yeah, welcome to this forum. It helps being a little 'off axis' when diving in to this hobby.
Regards
Jeff
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schrambo
New Member
Joined: November 2016
Posts: 7
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Post by schrambo on Nov 30, 2016 17:25:44 GMT -5
Hi Mitch Welcome to the Group :-) Whereabout in Oz are you ?? Have a look here for some RoTs jetandturbineowners.proboards.com/thread/680/diy-turbines Its possible to get an engine working without having the actual turbo specs , some simple measuring of wheel sizes and scroll A/Rs will provide an idea of flows and if they parts are a reasonable match for making a GT . Looking forward to hearing more Cheers John Hey John, I'm a Melbourne man, at least when I am not away with work! Funnily enough they dont seem to put GT's for industry in the nicest places... Will sadly be spending next week in Karratha WA sweating and overhauling. I wish they considered my hobbies before sending me to do my job! I am about to head off to strip down and rebuild my turbo to give a nice (clean) start point. Will be investigating what leftover steel I can salvage to make the fabrication easier so hopefully I get lucky in the scrap pile. Thanks for the reading material - I have been through and seen a few "rules of thumb" floating around the internet but its nice to understand the background mechanics. Will post some before and afters of the turbo and some drawings of my plans soon!  |
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schrambo
New Member
Joined: November 2016
Posts: 7
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Post by schrambo on Nov 30, 2016 17:26:51 GMT -5
Hi Mitch, Yeah, welcome to this forum. It helps being a little 'off axis' when diving in to this hobby. Regards Jeff I prefer to think that it's everyone elses axes that are off! haha Cheers, M |
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Post by racket on Nov 30, 2016 17:58:36 GMT -5
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schrambo
New Member
Joined: November 2016
Posts: 7
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Post by schrambo on Dec 1, 2016 6:32:29 GMT -5
So day one of messing with the turbo was a reasonable success. I will spare the details - it was mostly elbow grease - and let the pics speak. The one interesting thing was I removed the inlet volute, blasted and powder coated it to make it look a bit more neat. The finish wasnt as perfect as I had hoped due to me not knowing that aluminium retains a lot of gas and needs to be heat-soaked prior to spraying so it can off gas (hence the small bubbles). I have decided that if she spins up and runs well she will earn herself a new paint job in a more snassy colour Mechanically I think I got pretty lucky, especially considering the age. The shafts only have very very minimal play in them and when spinning it up with compressed air it seems solid as a rock. For now I will avoid stripping any further as I fear I may do more harm than good in pressing the impeller off the turbine/shaft combo. If she runs rough I will consider a re-build/re-bush in the future. Tomorrow will be spent doing some mathematics and if it all checks out trying to source some steel (what fun!) I will keep this post updated M Before:   |
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Post by racket on Dec 2, 2016 17:50:08 GMT -5
Hi Mitch
She's looking ready to be transformed into a GT.
Generally theres a reasonable amount of radial play in our shafts due to the requirement for very generous clearance both ID and OD of the bush bearings , as long as the comp wheel can't contact the scroll housing when forced from side to side , she's OK , axially endfloat is a few thou of an inch , the whole rotor floats in a sea of oil so that the rotor dynamics can be accommodated and controlled .
Did you get any wheel dimensions whilst you had her apart ??
Cheers
John
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schrambo
New Member
Joined: November 2016
Posts: 7
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Post by schrambo on Dec 11, 2016 17:06:17 GMT -5
Hi Mitch She's looking ready to be transformed into a GT. Generally theres a reasonable amount of radial play in our shafts due to the requirement for very generous clearance both ID and OD of the bush bearings , as long as the comp wheel can't contact the scroll housing when forced from side to side , she's OK , axially endfloat is a few thou of an inch , the whole rotor floats in a sea of oil so that the rotor dynamics can be accommodated and controlled . Did you get any wheel dimensions whilst you had her apart ?? Cheers John Ahoy - sorry I ended up heading overseas for a while on customer visits! To the turbo... Thanks for the comments - there did seem to be some scoring marks on one of the volute covers from a (light) blade strike, but looking at the tolerances as they are I don't really see how this was possible - there is pretty good clearance and radial play is not enough to allow for that. I almost figure it occurred on first spin up or so and has been that way since manufacture. If I was an intelligent and sensible experimenter I would have got pictures of this... may pull them off again this evening and have a look. In the industrial GTs I am used to seeing much tighter tolerances, and generally we make use of abradeable seals in compressor stages so it is as efficient as possible. My bloody electronic verniers were out of battery of course (and cant be used manually) so with some rough measurements I have a 2" compressor inlet which, using the ROTs you kindly provided give a 6" diameter flame tube 12" long. Now I have selected the combustion chamber size based off the more common pipe size of 8" which will give a 1" airspace surrounding the flame tube. This is a little higher than I guess according to the info however for manufacturing ease will have to do! I am fortunate to have a brother-in-law that works for a pipeline company so I have worded him up to look out for some decent off-cuts for me. I can get the 6" piece from local metal dealers but 8" is starting to get more difficult to obtain. The next step I want to think about while I await my good fortune is the orientation of the chamber and flow redirection. I am fortunate that the volute covers for this turbo are held on by steel ring straps, which means I can position the compressor outlet and turbine inlet in any orientation 360 degrees. I was thinking of having the necessary 90 degree bend after the combustion chamber to maybe take a few degrees off the outlet temperature and save my turbine from melting prematurely (this is what I have seen on a lot of commercial units to bring the turbine inlet temperature to a tolerable level). I cant find much discussion on this however for the DIY ones however - something for me to ponder more... I suppose I should also consider the jet nozzle too, off to google! |
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Post by racket on Dec 11, 2016 18:00:55 GMT -5
Hi Mitch Yep , our clearances are "generous" , turbos can get a rough life so there has to be a bit more than strictly necessary . With a 2 inch inlet you could go down to a 4 inch dia FT if you are careful about the fuel delivery , Jetspecs recommends that bigger 6" dia due to the fact that some small turbos have limited pressure building capability due to the comp wheel design , the lower pressure/density needs more volume for combustion , but your older more conventional design should be OK. With larger inducered turbos Jetspecs will recommend less generous diameters , all we need is at least 3 inducer areas for the flametube cross sectional area , so in your case with a 2" inducer/3.14 sq inch area , we need ~9.5 sq ins or 3.5" ID , so 4" will be adequate, use your 6" for the outer can , 12 inches long will be plenty . Make your entry "straight in " to the turb scroll , a sharp 90 degree bend between combustor and scroll causes problems. Don't worry about jet nozzles until after you get the engine running with an open pipe with its ID the same diameter as the turb wheels exducer shroud ( bore of scroll) , we don't want steps in diameter as they produce losses . Can I suggest you get a copy of these books www.amazon.com/Turbochargers-HP49-Books-Spark-Ignition-Applications/dp/0895861356/ref=sr_1_1?s=books&ie=UTF8&qid=1481496996&sr=1-1&keywords=turbochargerswww.amazon.com/Turbo-High-Performance-Turbocharger-Systems-S/dp/1932494294/ref=sr_1_2?s=books&ie=UTF8&qid=1481497118&sr=1-2&keywords=turbochargersBoth will give you a good idea about what you're dealing with . Cheers John |
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schrambo
New Member
Joined: November 2016
Posts: 7
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Post by schrambo on Dec 20, 2016 20:33:30 GMT -5
Thanks for the book suggestions - I have them on the post-Christmas list. Looks like good coffee table reading but suspect the missus will disagree on that point. Straight in entry should be easy enough to arrange geometrically and gives a useful design constraint... I don't function well with too much freedom! Good news is my brother in law came through on piping (I'll throw some images up later) so the 6" is covered regardless as if I use it as flame tube or combustion chamber. Seems as per your suggestion it will be simpler in a lot of ways to stick to smaller sizing. Keep meaning to set aside some time to do some CAD mockups to get my head around a few things I want to implement - will hopefully get this in before Christmas also! Now that I have some final dimensions considered this should be interesting |
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schrambo
New Member
Joined: November 2016
Posts: 7
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Post by schrambo on Jan 12, 2017 4:37:26 GMT -5
Finally got around to doing some CAD modelling on what I want to put together!     NB: Flametueb holes are illustrative only and I have not calculated/measured them out yet. Tubing is arranged so just need to find some time to hit up the workshop in the next few weeks! Some more detailed posts to come - just wanted to keep this updated |
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Post by racket on Jan 12, 2017 15:17:13 GMT -5
Hi Mitch
Yep , those flametube holes need to be calculated correctly ...............LOL, big ones at the outlet end ;-)
Hopefully you get a few cool days to get into your workshop , theres been some hot days down your way , not much better here , haven't been in my shed for quite a while :-(
Cheers
John
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