brayton
New Member
Joined: July 2018
Posts: 9
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Post by brayton on Jul 30, 2018 8:15:03 GMT -5
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brayton
New Member
Joined: July 2018
Posts: 9
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Post by brayton on Jul 30, 2018 19:06:41 GMT -5
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Post by racket on Jul 30, 2018 19:37:20 GMT -5
Hi John
Yep , single stage centrif comp on latter 250 engines, but boreless and titanium so that it can produce a 7::1 PR at very high tip speeds.
LOL, its always "interesting" how certified engines give worse fuel burn rates than new engines looking for development funding , its very hard to fudge the "numbers" with a turbine , you get caught out very quickly .
Turbine engines need a PR of >6-7 :1 to start getting reasonable competitive fuel burn rates to an IC engine without the need for some form of heat exchanger , with heat exchanger then a 3.5 :1 PR is OK .
The colder air at altitude certainly helps a turbine engine, the compressor wheel "works better" , allowing its turb stage/s an easier time of it and providing more energy to the freepower stage/s, but that also applies to the turbocharger on an IC engine , its comp will work better as well , so I'm not 100% sure of any advantage for the turbine engine, it'll depend on how the engines are configured , whether or not they're flat rated etc etc .....
Cheers John
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Post by finiteparts on Aug 8, 2018 22:26:52 GMT -5
Hi John, As I mentioned in this post, jetandturbineowners.proboards.com/post/16526Cummins is the manufacturer of the axial turbo-compound systems on the Volvo and Detroit Diesel engines. Cummins has been working on turbo-compounding diesel engines since the early 1980's (SAE 810073 and SAE 830505 technical papers are examples of this work). If you look at both of those papers you will see that the early power turbines that Cummins used were radial inflow, just like what was later used on the Scania DTC11 01 engines (1991 production) and then continued into the 12L DT12 HD engines in late 1999. In fact, Scania has a history of working with Cummins, for example their jointly developed HPI fuel system that changed diesel injection for all their future engines. I have always supposed that the Scania radial power turbine was made for them by Holset, but I have never been able to confirm this. Caterpillar did a good bit of work on turbo-compounding in the late 1980's (SAE 870300 and SAE 860072 technical papers document this work). They achieved 5.5% reductions in SFC and I am not sure why they never really got off the ground with their axial turbo-compound power turbine systems. They had introduced a ball bearing "high efficiency turbo" and the power turbine was also supported on two ball bearings, so potentially, with the 1980's technology, the ball bearings didn't offer the service life that is demanded in over the road trucks. All of these (and others like John Deer(2002), Hino(1988), DAF (1990), Isuzu(2002)) have explored the use of turbo-compound systems in various applications. Almost all of these use hydrodynamic clutchs to isolate the power turbine from the crankshaft torsional vibrations. The hydrodynamic clutch is designed to have around a 2% slip to reduce the torsional vibrations that are stepped up as they travel backwards through the gear reduction. For a diesel, the only other de-coupling device that I have seen used to transmit the majority of power through is a mechanical disk clutch on a real early application. If you are saying that you want to eliminate the hydrodynamic clutch due to complexity and weight on a diesel engine, then I would say that is not a good idea. But I think you are saying that you want to eliminate it for a gas turbine application. I think you could maybe by welding the case, but it would still be heavy...maybe you could find some matching gears used in other parts of the engine gear train to cobble together something to replace it. The reason you are seeing these systems come and go is due to emissions regulations. With the advent of the common rail injection system, the turbochargers could be used with a higher engine pressure ratio and the exhaust pressure could be driven up. This helped the EGR system flow over wider engine operating ranges. Additionally, the cost of more electronic controls dropped and thus controlling the engine systems became more manageable, so controlling a boosted, EGR diesel was more achievable and cost effective. This made turbo-compounding more desirable for the manufacturers to meet the then current emissions regulations. But as emission regulations get tighter and controlling the soot emissions comes into play, the need for exhaust after treatment surfaces. The increased exhaust back pressure due to DPFs, SCRs, ASCs and DOCs hanging of the tailpipe means that there is less pressure ratio left for the power turbine. The power turbine output is small relative to the overall engine power and when it is reduced further by the exhaust clap-trap, the cost of adding it in is just not feasible. Now don't get me wrong...I am a fan of the emissions reduction, especially the particulate reduction. When you see that the particulate sizes are on a sub-micron level and thus can pass through the blood air barrier in your lungs, it is really not good. Soot often forms poly-cyclic aromatic hydrocarbons (PAH) and since these flat rings can squeeze in between the proteins in the human DNA, they are very carcinogenic. In fact, PAHs are what labs use to induce cancer in lab rats...think about that the next time you char something on the grill or get behind a smokey old truck. Unfortunately, I haven't been able to get the DD15 power turbine assembly apart because I can't find a suitable gear puller. When I do, I will post more pictures and info. - Chris
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Post by finiteparts on Aug 8, 2018 22:45:57 GMT -5
Also, I have noticed that little engine on eBay. It looks like a really nice and simple set-up...unfortunately, that is way too much money for me to bid on. My Rotax 503 is putting out 50 hp at almost 97 lbm and burns 6.8 gallons per hour. So I would be more than happy to have 100 hp at 40 lbm even if it took my fuel consumption up to 14.7 gph. With a 5 gallon limit on the ultralights, I would just fly shorter, 20 mins vs 44 mins...but it would be WAY more fun! Especially with a near 50 lbm reduction in gross weight!
- Chris
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Post by finiteparts on Aug 19, 2018 22:02:18 GMT -5
I just went through this post and fixed all my images. It would be nice if each poster would fix the images so that we can keep the value of the older posts.
- Chris
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Post by racket on Aug 19, 2018 22:33:10 GMT -5
Hi Chris
LOL, the only pics I have/had we're here on JATO , most of my build pics have now permanently disappeared for ever :-(
Cheers John
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Post by finiteparts on Aug 24, 2018 21:13:34 GMT -5
John, If they were posted on here, did you change the code from "postimg.org" to "postimg.cc" as suggested by Alain in this post, jetandturbineowners.proboards.com/post/22453If you just go into "Edit" then look at the BBCode, it is easy to replace the .org to .cc. - Chris
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Post by racket on Aug 25, 2018 1:31:49 GMT -5
Hi Chris
I'll give it a go and see what happens ..............LOL, I'm not very computer literate , I get by when things are working OK but when they don't I have to quickly admit defeat .
Cheers John
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Post by racket on Aug 25, 2018 2:53:45 GMT -5
Hi Chris
LOL, thanks for sorting me out :-) ................what a shit of a job .............but I think all the pics for the 12/118 build are back up , only another few hours to go checking the other builds ............bugger :-(
Cheers John
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Post by finiteparts on Aug 25, 2018 15:41:30 GMT -5
John that is awesome! Glad they were there and recoverable.
I agree...sort of a pain...
- Chris
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Post by racket on Aug 25, 2018 17:19:09 GMT -5
Hi Chris
Thanks again for explaining how to do it in layman's terms , the build threads sorta lack a vital ingredient without pics .
More checking/correcting today :-)
Cheers John
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Post by finiteparts on Sept 30, 2018 14:39:56 GMT -5
As a follow up to this post, jetandturbineowners.proboards.com/post/21759I ended up getting two more of these center sections (these were OR9810's...I have no idea how they compare to the OR9809) for ridiculously cheap! So cheap, it would have been wrong to not get them! Ha! So I will definitely put them to use. The first one had damage to the turbine and a few bent inducer tips on the compressor, so I figured that it would be good to take one apart and check out the internals. I figured that everyone might enjoy seeing the rotor, so I will add some pictures. Here you can see the rotor sitting beside an ST-50 rotor, which had been a relatively large rotor, till I got these. then a few of just the rotor.... Here is a comparison of the OR9809 compressor to the HT80 and TV94 compressor wheels... I haven't identified the compressor material, but it has a much stiffer sound...it makes a tight ping which makes me think it may be titanium...but it seems too light to be titanium, so that makes me think it is a milled, aluminum forging... Here are some shots of the bearings. As you can see from the pictures, the aft side of the thrust bearing has a much shallower ramp than the front surface, which almost appears flat. Also of note is the internal bore of the thrust bearing between the two faces. The thrust runner surfaces are precision ground flat and very, very accurate fit to the shaft. The bearings are of two different materials, one is brass while the other is a bronze. They are semi-floating style and you can see the radial groove that is held stationary by the c-clip, which has a tang on it bent back at 90 degrees to engage this slot. The bearing clearance is also very tight and it does feel like the rear clearance is larger than the forward bearing...but I will have to check that before I claim it as fact. I will have to try to measure it up before I set the clearances on whatever I find to use these on Finally, you can see the piston ring seal and the lack of a sharp edged oil slinger like the smaller turbos use. It is probable that the sharp edge is not needed due to the larger outer diameter that the slinger lip sits at. Also, note the smooth balance removal areas on the raised center area of the turbine wheel. All in all, this is a very beautiful built turbo and I can't believe I got them so cheap. Enjoy! Chris
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Post by racket on Oct 1, 2018 1:37:27 GMT -5
Hi Chris .
Nice bits , like the long shaft , plenty of room for the flametube length :-)
The comp was milled alloy on the one I measured up years ago , and is available from China .
Cheers John
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Post by finiteparts on Oct 6, 2018 23:40:22 GMT -5
Found a few specs on the turbo...very few mind you.
Max rotational speed = 57,000 rpm (corresponds to a compressor tip speed of 1670 ft/s) Max turbine inlet temp = 750 C ...this one is the disappointing one. 1350 F turbine inlet temperature is really low and I will try to do some quick calcs on rotor stress to see if this is somehow higher than our typical 713C cast wheels...if not, I will have to assume that it is some lower capability alloy.
~ Chris
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