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Post by racket on Apr 1, 2017 17:10:09 GMT -5
Hi Tony
Yep , I can relate to your restrictions on rocket fuel , when I was a kid some 50 plus years ago I use to buy my bulk gunpowder chemicals at the local hardware store , can't these days , I'd probably have the "men in black" knocking on my door :-(
LOL, Bruce Simpson in NZ did have them "knocking" some years ago when he started talking about low cost guided pulse jets he could make that cost a fraction of "mil spec" .
Thankfully the DIY gas turbine community has been spared this harassment .............so far :-)
There is another alternative to our current scenario of the single large engine with bleed air , and that is using a smaller DIY turbo based engine feeding a larger turbo for a 2 shaft engine that supplies compressed air , I've been helping another Member with similar setups for some time, he's been using Garrett turbos for which theres plenty of comp and turb maps for me to find suitable matches .
Cheers John
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CH3NO2
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Post by CH3NO2 on Apr 1, 2017 18:24:16 GMT -5
I'll contact Precision Turbo Monday for the compressor and turbine performance maps. From the information gathered from their catalog of 2000+HP turbos they have a range of inducer/exducer area ratios.
GEN3 Pro Mod 98 = 14.8% PT101 = 21.1% PT106 = 11.9%
Without knowing the maps or how they would apply to a specific application, would it be correct to say the PT101 likely has a better compressor/turbine match for turbojet propulsion applications?
If the application is for bleeding out air from the compressor, and it's not intended for propulsion, if/how/why does the area ratio requirement change?
Thanks John!
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CH3NO2
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Post by CH3NO2 on Apr 1, 2017 18:27:21 GMT -5
Ah yes... I remember the Bruce Simpson event. I was following that a while back.
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Post by racket on Apr 1, 2017 20:14:36 GMT -5
Hi Tony
Generally with a large turbo on an IC engine, especially a SI type engine, there'll be a wastegate fitted somewhere between engine and turbo to prevent overboosting the engine , whereas a big CI diesel will often have a freefloating turbo without wastegate which generally means a longer spoolup time but less backpressure on the engine so better fuel efficiency which is more important than having the vehicle accelerate a tad faster .
The different compressor sizes on Precision turbos could run the same turb wheel but different scroll A/Rs , smaller A/R with smaller comp inducer so that the gas velocity thru the scroll throat is optimal for that particular setup.
But because you want to bleed off a lotta air you need to go with the larger flow comp wheel so that as a percentage your bleed is less , this should make it a bit easier to accomplish .
The 106 mm exducered turb wheel that Anders and I use with our 98 mm inducered comps is only ~17% bigger , his latest engine has them both the same size , my 12/118 engine has a large negative difference ...............things can be fudged ;-)
Cheers John
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CH3NO2
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Post by CH3NO2 on Apr 3, 2017 10:43:56 GMT -5
I just got off the phone with Precision Turbo... they don't have compressor maps. For any of their products.
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CH3NO2
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Post by CH3NO2 on Apr 3, 2017 16:28:38 GMT -5
OK, I just got off the phone with CompTurbo.com. They dont have turbine maps but they do have compressor maps. They emailed me these. The pressure is in the right range for my application and the mass flow is very high. It's even available as an oil-less turbo! Just oil up through the grease fittings once in a while and keep it cool with water. This feature can eliminate a lot of headache. Their website has tables with many wheel options. Including stainless steel housings and V-bands all the way around. Very nice. Comp Turbo Tables
Comp Turbo HousingsI'm thinking the 6498106 CT6X ceramic oil-less turbo. 98mm compressor inducer with a 106mm turbine exducer. What do you think? The nice thing is they have so many options available one of them is bound to make a good fit. PS - Their turbines are made of Inconel 713. PPS - They can drill and tap a RPM sensor into the compressor housing if they are sent a sensor to install.
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Post by racket on Apr 3, 2017 23:32:51 GMT -5
Hi Tony
Those Comp Turbo map flows seem a tad more than what is normal for the sized inducers , also some of their other info is "hyped" , I'm always a bit wary of whats portrayed by people trying to sell me a product.
Their turb scroll A/Rs are also a bit small , understandable considering the type and sized turbine wheel they're using , its smaller than the other brands, which might make it more difficult to get your highest temp gases out , they are competition turbos and would always have a wastegate in their system somewhere
As for using turbos with ball bearings vs "brass" , I'm not a great fan of "balls" , they offer us turbine builders no benefits over "brass" , sure they advertise faster spoolups, but we're already spooled up when idling , and the windage losses from balls at high rpm tend to balance out the frictional losses from the "brass" , virtually all of the heavy duty industrial turbos use "brass", then theres the matter of cost , those high speed "balls" probably cost 10 times what "brass" does , so we end up paying more for a turbo without any benefits other than maybe slightly easy starting due to the lower friction of balls at low speeds , a decent sized starter nullifies that benefit .
Without a turbine map its hard to say if either the 98 or 106 comp will work , but 98 and 106 are both common inducer sizes and if we apply the usual flow numbers to them , then I'd still opt for the 106 , as the efficiency will be better when you're taking full bleed , this then makes it easier for the turb stage and its unknown characteristics.
A Garrett Gt6041 with a 106/141 mm comp wheel and a 1.47 A/R scroll housing on its 130/119 mm turb wheel would do the job .
Cheers John
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CH3NO2
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Post by CH3NO2 on Apr 4, 2017 1:11:18 GMT -5
Hi John, On their turbo scroll A/R, I noticed they were a bit on the low side and then I navigated to another part of their website and found their technology section. Turbine Description Does their turbine description make any sense? On the Garrett Gt6041, I would like to check it out but it doesn't show up on the turbosbygarrett website. Tony
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Post by racket on Apr 4, 2017 4:20:15 GMT -5
Hi Tony
LOL.............its a lot of hype :-( , a turbine wheel with the same inducer and exducer diameter is actually a few percentage point less efficient than a conventional one , also the hype about low exhaust gas velocity meaning more energy to the comp is crap , their lightweight turb wheel is simply a heavily clipped wheel with one less blade, the design might be useful for a drag race car which require a specific turbo arrangement , but as far as it being OK for a gas turbine conversion , not so good
More hype like the nice bullet comp nut , I've read scientific Papers on whether they give any improvement over just an ordinary nut , they don't .
Yeh , I think the GTX55 has sorta replaced it which is a shame as its not as suitable for what you want to do .
Cheers John
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CH3NO2
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Post by CH3NO2 on Apr 4, 2017 9:05:59 GMT -5
The Gt6041 out of production... That's a bummer. So far I havn't been able to find any other manufacturers that make a turbo in this size range. Any suggestions? There are other suppliers of "Gt6041 turbos" but if they are officially out of production they may simply be Chinese knock off's. Is this one from Turbonetics the best alternative? At least this one is in stock.
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CH3NO2
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Post by CH3NO2 on Apr 4, 2017 9:44:48 GMT -5
The CT-106 compressor looks fantastic but as you mentioned it has a suspiciously high mass flow rate. It did cross my mind but I don't have the experience to know what a believable mass flow rate is for a given inducer diameter. If you take a second look at the map you will see the surge line is ruler straight.... That doesn't look like a actual, real measurement. It suggests to me the surge line may be arbitrary and artificial. If the surge line is fabricated the rest of the map is questionable. IDK
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Post by racket on Apr 4, 2017 16:58:04 GMT -5
Hi Tony That Turbonetics map says its scaled off a 118 mm 50 Trim comp , the efficiency levels are too low , this is what the Garrett GT6041 56 Trim comp map looks like with its higher efficiencies www.himni-racing.com/turbochargers/turbo-compressor-turbine-maps/garrett-gt6041-compressor-map-gt60 , larger flow comps generally have higher efficiencies . There are a number of GT6041 turbos used on heavy duty diesels www.turbomaster.info/eng/catalogs/model.php?base=garrett&pagina=GT60 but they aren't 56Trim ,48 Trim seems more common with its 98 mm inducer 141 exducer............and yes, a lot of reputable brand turbos are made in China , and have been for a number of years, www.worldturbocharger.com/ have a range of industrial GT6041 bits that we've corresponded about over the years , I have a bearing kit here , and use their TV94 bearing kits which cost ~10% of buying locally even though the local ones are exactly the same ,............LOL, probably made on the same machines . Mass flow per unit area of inlet is pretty well fixed if we want good efficiency , the CT-106 was a tad too much for my "gut feeling" Cheers John
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CH3NO2
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Post by CH3NO2 on Apr 4, 2017 19:02:32 GMT -5
Once again, thank you for all the help and leads. The WorldTurbocharger.com link is a great resource.
BTW, I'm about half way through your "Fat Boy" thread. *Mind seriously blown.* Major props on your engineering talent, patience, persistence and fabrication skills. Unbelievable. Never seen an _individual_ pull off a complex technical build like that. Were you the director of engineering at a aerospace company? Professor of Mechanical Engineering? WOW!
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Post by racket on Apr 4, 2017 22:53:54 GMT -5
Hi Tony
LOL.............nope, nothing important, just a backyard tinkerer , left school at 16 , never had any formal engineering education , just picked up various "skills?" as I went through life, I often wish I did have something more formal , I might have been able to earn more than I did :-)
Yep , that turbo Site has lotsa goodies , we were interested in their GT6041 turb wheels at one time but they turned out to be for the "industrial" 98 mm inducered 48 Trim comp wheels , the turb inducer tip height was smaller than the one on the 56 Trim comp GT6041.
Glad you enjoyed my 12/118 build Thread , theres a few more builds of mine here on Site ............I just like making things :-)
Cheers John
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CH3NO2
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Post by CH3NO2 on Apr 5, 2017 5:00:55 GMT -5
That is too cool.
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