ashpowers
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Post by ashpowers on Apr 19, 2012 16:59:47 GMT -5
Fist full rendering of the engine. 18 hours for this to build...
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Post by Johansson on Apr 20, 2012 0:10:29 GMT -5
Damn!
Will there be a slip joint on the exhaust pipe section inside the combustor liner? Might see some warpage there since it is the only combustor wall that gets hot.
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Post by turbochris on Apr 20, 2012 7:49:32 GMT -5
Is there any way to get Solidworks to just start the thing up and go ahead and spin/expand/make power/blow up? (I know I'd fail test) I don't know any of this new CAD stuff. I'm too busy repairing machines torn up by others who "think" they know it. I can write M code one line at a time, but unless we're making washers it would take me years to find the numbers let alone input them..... I bet Garry's Mod for Half Life could make a running jet engine.
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ashpowers
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Post by ashpowers on Apr 20, 2012 14:18:27 GMT -5
Solidworks doesn't have a means to model the bratyon cycle so no go on telling solidworks to crank her up. However, what Solidworks has been able to show is not only flow velocities and trajectories, but it has also acted to double-check the thermo calcs produced in the spreadsheet I wrote a few years back for this engine. You can't simulate the entire cycle but you can break it all down into stages and get a pretty accurate model of what will occur in the real engine. I'm looking forward to checking the CFD analyses for the combustor. I've held off on doing that as the combustor is one of the most complex models and it is going to take some serious processing time. Any any alterations to the combustor's design isn't exactly the easiest thing to do. As for the bearing arrangement, I've spent some time working up an initial idea. Here's the details: 1) Radial labyrinth seal behind compressor wheel to limit P2 pressure from building up and creating increased forward axial loads on the bearings. 2) Some air will bleed past the seal and be collected into an annular ring just inward of the labyrinth seal and delivered to and through the bearing housing via 5 feed ports. 3) Two annular chambers are machined into the front and rear of the bearing housing with a series of 15 radial ports connecting into the bearing tube to deliver cooling air to the bearings. 4) The bearing tube is supported by 4 0.070" viton orings with a ~0.0025" radial clearance to the bearing tube. Two delivery ports will feed a fuel/oil mixture to these two annular gaps to act as a hydrostatic damping system to reduce rotating harmonics of the 66KRPM rotating group. 5) A small volume of this fuel/oil mix is carried through the wall of the bearing tube through two small ports to feed fuel/oil into the cooling air stream at a perpendicular angle to atomize the lubricant. 6) The cooling air and fuel/oil mix will converge at the middle of the bearing set and be collected and routed out of the bearing housing via the large radial center port. This will be collected outside of the engine and passed through a de-aeration chamber to seperate the air and fuel/oil mix where the liquid will be returned back to the fuel tank. 7) There is also a series of 20 small air cooling ports through the rear bearing plate just outward (radially) of the outside diameter of the bearing housing. These ports will feed P2 air into the air space between the turbine's heat shield and the rear bearing plate to keep the temp of the rear bearing plate at a minimum. -- Additionally, with the fuel/oil mixture flowing around the bearing tube there will be an additional cooling effect to keep the bearings happy.
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ashpowers
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Posts: 207
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Post by ashpowers on Apr 21, 2012 12:22:02 GMT -5
The jet pipe still needs some resolving. I'm actually considering to modify the jetpipe and NGV top plate (the one that the jetpipe attaches to) by adding a ring to the o.d. of the jetpipe at the NGV end. This ring being just enough to carve a piston ring type seal seat. The NGV top ring will be modified by adding a sleeve for the jetpipe's sealing ring assembly to slide into, with a bit of room once fitted to allow for thermal expansion of the jet pipe without loading against the NGV top ring. And finally, the back end of the jetpipe will be TIG welded to the outlet flange and become a permanent component of the outer casing. This would be the quick and easy method, but I could flange the back end of the jetpipe such that its flange fits between the main casing's rear flange and the freepower turbine duct's flange. I will undoubtedly go the latter route.......
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ashpowers
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Post by ashpowers on Apr 27, 2012 21:54:41 GMT -5
This project has reaped some good attention this week. A few good steps achieved! 1) Ordered and received the 6" X 6" X 1/4" plate of PEEK (polyetheretherketone). This plastic has some pretty amazing properties. High-Strength High-Temperature PEEK Temperature Range: -20° to 480° F Tensile Strength: Excellent Impact Strength: Good Low friction Good electrical insulator Machine with carbide tooling Hardness: Rockwell R126 Comparable to Victrex, PEEK (polyetheretherketone) maintains its shape and offers greater tensile strength in a wider temperature range than PTFE. Meets UL 94V0, except film, which meets UL 94VTM0 for flammability. Rectangular bars, sheets, and tan rods are FDA compliant. Perfect for a radial labyrinth seal application. 2) Received the Naichi 7204B angular contact bearings, 20mmX47mmX14mm, brass cage, C3 Disassembled one of them today - machined an arbor to fit into the i.d. of the inner race - mounted in a vice with the bearing about 1/8" above the vice. While rotating the outer race and heating with a small propane torch, expanded outer ring until it dropped out. Ordered 60 SiN3 ceramic balls to pack inbetween these races, full complement, no cage. 3) Spent some time last Friday google searching for companies that specialize in overhaul services for the allison C series engines. After a few phone calls, got in touch with a company that mainstreams these engines. Spoke with a sales rep about the project, who passed me on to the head tech in the shop, where we engaged in a 45-minute conversation about the project, shaft dynamics, seals, and so on and on.. .... and also him divulging in the quantity of TBO'd parts they still have "in the back room" of the shop. Well, I got an email this afternoon from the master tech telling me he has found (4) of the #8 bearings from the C20 engine - all still having service hours on them and the best of all, having my name on them as well. FREEBIES - just paid shipping to get them here and them babies are all mine. 4) Last weekend I pulled out the text I purchased a few years back at the beginnings of this project - "Ducted Fan Design" by Piolenc & Wright. It is a text that provides both the theory as well as math required to optimally design a ducted fan of any size, for any aplication. After re-reading the nuts and bolts of it and further researching airfoil lift theory, I discovered the original Lifting-Line Theory; the first and-still-used-today complete model of airfoil lift. Ironically, the concept of airfoil lift has been something I've understood since the days I was building and flying model airplanes in my single-digit years of age..... at least, so I thought, LOL! At this time in my life, be it previous tinkering and education or be it by the level of motivation I have for this project, (probably both), I spent about 3 hours studying the line-lift theory, non-stop, understanding entirely both the theory and how the maths expose the sheer beautiful simplicity of the model, and stepped away from it a changed man... =) This weekend's entertainment will consist of the development of an Excel spreadsheet that will be used to calculate the most efficient propeller and duct design for this application as well as allow entry of many different airfoil section characteristic tables for further analyses. I will be able to construct a spreadsheet that will be capable of very quickly and accurately provide not just the performance curves of a rotor/duct design, but also produce the very blueprint of the rotor and duct on the same stroke......... amazing what you can do with a little math! ;-) 5) Got a notification today that the Radial NGV section is complete and shipped! Overall - today was a great day for the TV94 TurboShaft project. BTW, if you look at this forum long enough and then go take a leak, you'll see horizontal bands of blue color in the toilet water. ;-) What IS up with all the ORANGE? Using this forum is making me piss blue! =)
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Post by racket on Apr 27, 2012 23:33:34 GMT -5
Hi Ash
Projects moving along quickly .................nice when it does that :-)
Sounds like you've found a "sympathetic" contact for the Allison bits , look after him .
Cheers John
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ashpowers
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Post by ashpowers on Apr 28, 2012 0:51:38 GMT -5
Hi John, Yep, forward progress is always good... especially considering I started this project in 2008 and have had to shelve it for many years while growing my business. But I've also grown a good bit as well over that time... which I think is working well for me in this project... I've had many conversations about the turbine projects I've done over the years and one common question is "why". Originally it was just a simple desire to make one, something I had since reading the encyclopedia collection my parents bought when I was about 10.... and the section detailing jet engines just captivated me. It wasn't until AFTER the T04 TurboJet Scooter project that I found myself using the knowledge I had gained about thermodynamics, compressors, combustion, and turbines in a number of different aspects of my business and product development. It had positive influence on other aspects of my life of which I was unable to forsee.... and once again, this project is already railed down that same path, offering the opportunity to learn more. Now I know where it leads, and let the good times roll.
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ashpowers
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Posts: 207
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Post by ashpowers on Apr 29, 2012 0:07:00 GMT -5
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Post by racket on Apr 29, 2012 20:38:41 GMT -5
Hi Ash
LOL, theres some heavy readin' there :-)
Cheers John
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ashpowers
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Post by ashpowers on Apr 30, 2012 11:00:04 GMT -5
Hi John
I spent nearly the entire weekend searching and reading so many documents regarding shaft dynamics - it took quite a bit of time to drill down through the internet to find good sources of info (isn't it always, LOL). I also found a company that has produced an Excel spreadsheet program that does EXACTLY what we need. The program is called XLRotor, Spreadsheets for Rotordynamic Analysis. It can be found at xlrotor.com
The trial version only allows 5 stations along the shaft which should be able to cover the model for our application. You should get your hands on a copy of this - it is a pretty amazing piece of software. Capable of analyzing every aspect of the rotational dynamics as well as a means to incorporate dampening and analyze the dynamics with that in place. I think this will be the key to helping resolve the issues you were seeing. Some of the example files that it comes with show some pretty amazing aspects of rotational dynamics with lots of visual plots and graphs of what occurs in the shafting.
The most damaging aspect of our engines to bearing life is likely a result of these shaft dynamics - at the kind of speeds these parts are rotating at, the various modes of shaft deflections will produce HUGE radial loads on the bearings if the dynamics are not analyzed and proper design and dampening put into place. Fortunately with this spreadsheet already in existence, it will dramatically reduce the amount of time I'll have to spend developing one of my own! =) FREEBIES are always nice!
-Ash
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ashpowers
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Post by ashpowers on May 5, 2012 19:09:29 GMT -5
Got some goodies in the mail yesterday! =) ..... and I got an email from a second company I spoke to about this project and they are also sending me 4 of these same bearings! I also received the SiN3 balls for the angular contact bearings and took a little time to put one of them together in a full complement arrangement - 13 balls total. I've been considering to arrange the bearings using two of the RR radial bearings and two of the angular contact bearings... Using the angular contact bearings directly behind the comp and directly in front of the turbine, with the two RR bearings mounted directly inboard of the AC bearings. Combining the axial load carrying capacity of the angular contact bearings with the radial load capacity of the RR bearings should produce a rolling element system that is pretty much bullet-proof. Ive spent most of the day today playing with XLRotor and have acquainted myself with its interface. Have produced some interesting response plots that explain a lot of the dynamics that can easily lead to self-destruction if not properly built. Still playing with it though - will have some nice screenshots soon once I've nailed things down.
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Post by racket on May 6, 2012 0:19:44 GMT -5
Hi Ash
A bit early for Christmas .................nice :-)
Cheers John
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ashpowers
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Post by ashpowers on May 6, 2012 8:32:49 GMT -5
XLRotor isn't going to work.. Too few station definitions... ..... seeking better solution......
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Post by racket on May 6, 2012 16:08:19 GMT -5
Hi Ash
Did the full compliment hybrid need to be "re expanded" to get all the balls in , does it hold together ??
I found the SiN balls are just so much smoother running than steel balls , I did some testing with FM-1 and found that even with 25 lbs of preload that it took 40 seconds for the rotor to spooldown from the 3,500 rpm that the leafblower produced with a cold engine .
After the engine had been "warmed" the blower produced 4,000 rpm and it took 65 seconds to come to a stop ................a finger flick of the comp took 18 seconds to come to a standstill.
When I shutoff the engines fuel at an idle of 25,000 rpm it took 93 seconds to come to a stop ..........them SiN balls are slippery :-)
Cheers John
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