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Post by turboron on Jun 18, 2020 19:46:34 GMT -5
Scott, is it feasible to plumb a cyclonic separator into the vent line. The oil vapor enters tangentially near the bottom on the can. As the mixture swirls around the oil goes out the bottom back to the oil tank while the vapor goes out the top to the exhaust housing to mix with the exhaust gas stream. These can be cheap sheetmetal units.
Thanks, Ron
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jetric
Veteran Member
Joined: December 2014
Posts: 149 
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Post by jetric on Jun 18, 2020 22:46:02 GMT -5
Hi John/Scott, Don't know if you are both doing this to annoy me but it seems to me that you are hell bent on demeriting my afterburner design. Let me get a few things straight here, When i drew up the design back in 2003 i had no idea that there was a technical paper on this type of afterburner!! there wasn't even any of these chat groups for DIY gas turbines, it took me three years of trial and error with different design changes to come to the final successful layout which included some seriously pissed off neighbours!! So Scott your quote 'So I can now see where our 7 degree AB "cone angle" and 8x1mm holes come from' is utter bullshit!! the cone angles where designed like that to prevent any shockwaves resonating inside the afterburner (like on a two stroke expansion chamber) and to prevent the afterburner screech from being excessive due to unstable combustion (then i would of had to use screech liners) and the so called '7 degree angle' was used to slowly increase the velocity of the gasses to reduce losses (didnt even know it was 7 degrees) as for the 8x1 holes that was just the area of the bore of the fuel feed pipe divided up into a number of holes because my smallest drill bit was 1mm. I put a lot of work and effort into that afterburner design that I have never received any credit for!! and to have someone say that I had ripped the design off hurts me a lot! Well done John! yet another thing you have contradicted me on, this is similar to me saying that you have ripped the design for your engines from a model turbojet engine!! Scott, I feel conned and betrayed after your visit when I demonstrated my engine on the kart and explained the systems on the engine and how they work and also showed you my brothers kart and the engine I built for it, then to have you put a quote up like this and also on a previous post thanking Andy/John for there help but no thanks for me! I have made a lot of advancements for the turbocharger based DIY engine that I will not receive any accreditation for or reveal now due to certain events in the past, for one thing Scott I could of gave you some plans of a proven design that would of made your flame tube/combustion chamber a third of it's current size. Also I was going to offer a rotor balancing service to the group as I have a brand new Dawe dynamic balancing machine that was new old stock from the MOD, But why should I do any of this now. Richard S. Many thanks for the link John, very interesting (and I imagine impossible to find on the internet)! So I can now see where our 7 degree AB "cone angle" and 8x1mm holes come from!! I am intending to ride the Jetbike in about 2 weeks time on a UK Dragstrip, weather dependent. My main concern about having another fire half way down the strip and kissing goodbye to the bike, means I have started on my leak fixing exercise - which has involved dropping the combustor down. Unfortunately as everything is so packed in (or maybe because I "designed" it without considering serviceability!!) this has meant stripping almost the entire bike down and removing all the pumps. The combustor is now out and having looked inside it with a torch, the flame tube looks in good condition. The turbine blades on the turbo also look the familiar dry "white" colour.  The AB tube mounts to turbo on bolted flange, I didn't have a new stainless gasket so re-used the old one in conjunction with JB Weld "Extreme Heat" Metallic Paste. I intend to use the same on the combustor joint (with new SS gasket). I will also be routing the oil tank breather into the compressor entry to avoid all the oil mist. I am aiming for the bike to have no leaks at all and no smoke or vapour around the engine, also making any problem easier to spot during startup etc!! Cheers Scott |
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Post by racket on Jun 19, 2020 1:02:02 GMT -5
Hi Richard
Hang on a second here , you're way off the mark .
Firstly I had no idea how you came by your A/B design........as you well know , afterburners are not my thing , I like shaft horsepower .
Secondly I've known about, and had a copy of the AiResearch Paper for a very long time , it was distributed around the old Yahoo DIY Gas Turbines Group , originally I think by Mike Early , a Garrett aero engineer in Phoenix who had contacts with the turbo division there, I corresponded with Mike on a number of issues.
Thirdly, probably the earliest jetkart on a dragstrip was Chris Kruggs with afterburner based on the AiResearch design , his tank turbo allowed 70 mph in the 1/4 mile, ................hence my comments in the earlier email that "Most of our DIY afterburners are based on the AiResearch ramjet dump combustor used on their 1030 Low Cost Turbojet".............its a historical fact that this Paper has been used by a lot of guys I've dealt with over the decades .
Fourthly, I have never said you ripped your design off , but I'm happy to acknowledge the fact that I've "copied shamelessly" wherever I can , my ego doesn't demand recognition , I give my contributions freely .
Perhaps if you contributed more often to the Forum, Members would be enlightened as to your contributions to the advancement of DIY Turbo based jet engines, so get on the keyboard as often as you can and share your wisdom :-)
Regards
John
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Post by slittlewing on Jun 19, 2020 7:27:49 GMT -5
Thanks for the breather info/ideas Mark and Ron, the imbalance of dirt sticking to the comp makes sense! As for the swirl pot, I guess its an option but space is extremely limited! Maybe a small swirl pot filled with foam would work, it feels like the oil vapour is pretty fine (as it looks like smoke), so I'm not sure if the oil would stick to the walls otherwise? We have used these types of filters at work, made by a company called "DES-CASE"  I may try one of these as my first port of call in the hope that it does the job, if it fits! Link to catalog: www.descase.com/wp-content/uploads/2019/11/Des-Case-Catalog-1903.pdfRichard, I think its pretty clear that my short one sentence on the paper was not written to de-meriting/annoying/offending you in any way. I (wrongly) assumed that's where the 7deg angle and hole rules that had come from but clearly not - so apologies for that. You will notice that so far all I have made are a couple of fire up videos (your name is in the description here: www.youtube.com/watch?v=GP-WqlWp1_s&t=36s), and I have been waiting to produce a video on "how I built the jetbike" where I can thank this forum, John, Andy, you and your afterburner design in front of an audience who actually have technical interest rather than just the standard "cool it makes a noise and fire". You will see soon enough and you may be pleasantly surprised. As for your brothers kart, I consider it a work of art and remember the quality and lightness of the build - I concur with john that its a real shame you aren't posting more on here given your level of expertise. I have no claim on any of the "invention" of the engine in my project at all, except for the ECU which I think is a decent step forward as a small/light control system that could operate most of our engines. I also remember your combustor design and how you achieved the tiny chamber in a "easy to manufacture way", again this would be helpful to many on this forum if you chose to share it (its not my place to). In any case, I don't wish to argue with you or pollute this build thread. If you still feel annoyed then free to contact me directly... but I would greatly prefer it if you just came and visited me at home where we could fire up the bike and talk jet engines with a beer!  Cheers Scott |
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Post by turboron on Jun 19, 2020 9:34:03 GMT -5
Scott, the Desiccant breather should be a good choice for your application due to the short duration tests, runs, etc.
Thanks, Ron
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Post by slittlewing on Jun 19, 2020 10:14:36 GMT -5
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Post by turboron on Jun 19, 2020 15:03:48 GMT -5
Scott, I don't see how the oil/vapor mixture is separated with the bronze filter?
The only other experience that I have that is appropriate is a coalescing filter. The oil/vapor mixture enters in the bottom third of a long vertical tank of low diameter. This type of filter has a steel wool element in a basket that coalesces the oil which falls to the bottom of the tank and is drained. The vapor exits the top of the tank. My experience is with the larger sizes so I am not sure the minimum size available.
Thank, Ron
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Post by pitciblackscotland on Jun 19, 2020 15:08:36 GMT -5
Hi Scott, no worries, yeah the vapour is like smoke but in time it will stick on the comp wheel. I ran my engine a couple of times and the comp had a good coating of oil. If you can find room on the bike that Desiccant breather may do the trick Cheers, Mark. |
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Post by racket on Jun 21, 2020 1:08:10 GMT -5
Hi Scott When you mentioned problems getting the A/B to light at any but low power settings I sent you the Link to the AiResearch unit to checkout the the "complexities" they encountered in producing their unit despite all of the help they had from Govt Agencies . They used "radial" injection of the fuel , but there were a lot of variables to getting the right distribution of fuel when gas mass flow rates/speeds were added into the mix , as the various graphs indicate. With your "axial" injection you will be encountering "similar??" variables that will influence the distribution/coverage and consequent ignition variables . During the construction of the GT6041 afterburner sprayer jetandturbineowners.proboards.com/thread/78/garrett-gt6041-powered-kart?page=9 ( half way down the page) I did some experimenting with hole orientation in respect to the "gas" flow from the leafblower and ended up having the holes staggered so that there was some radial component . I used 16 X 1 mm holes for a turbo flowing ~2.75 lbs/sec , nearly 3 times your air flow rate , so your fuel pressure drop across the 8 injection holes will be less, and possibly more prone to the fuel being blown "axially" backwards at higher power settings by the stronger faster gases exiting the exducer , at more moderate power settings there could also be a change in gas swirl angle exiting the exducer that affects the spray in a more positive manner allowing better ignition ..............a huge number of potential variable that are causing your problems.......................perhaps the addition of a single radial hole that sprays fuel to the stub pipe wall where it will flow rearwards to the spark plug is all thats required. Food for thought :-) Cheers John |
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Post by slittlewing on Jun 23, 2020 8:01:47 GMT -5
Cheers Ron/Mark, I was thinking the bronze sintered one could work in the same way a steel wool does (i.e. the mist is forced between the bronze elements and the fluid sticks to them), but the good news is that the smallest variant of the dessicant filter looks like it fits the bike. I am going to borrow an old and well-used one from work to try without shelling out for one, in the case it doesn't work! One other thing I noticed previously was that with higher oil pressures, there was much less misting/aeration, presumably because no air was getting in past the seals. So I may try upping my demand on the ECU and see if this helps too.
John you make a very good point... and the way you set out your holes is an excellent idea to get more even spray distribution in the tube (Wish I had thought of that before haha!!).... What you say about the fuel being more likely blown backwards rather than radially (at higher throttle) on mine makes perfect sense particularly with the drilling's pointed at the turbine, as does a suggested single radial drilling to squirt some fuel down the tube in the spark plug region. Unfortunately my injection ring is welded into the AB tube in 3 places and basically inaccessible now. I could drill through the outer tube into the ring and then seal up the outer tube hole with some weld if I needed to, but I think its probably not worth it on this machine... I was just wondering for future reference how to design an afterburner that would light at all throttles! It seems to be a common issue trying to light them at higher P2s. Obviously at the moment, if you were to do a timed run and the AB went out... you would need to completely throttle down, relight and throttle back up and the entire run would be scrap. Compared to just pressing the AB button off and on at max throttle to re-ignite. Maybe the saving grace is that once the AB tube is so hot that it "glows", it might self light without spark anyway!
I just read the rest of your kart build thread and saw the videos of your AB lighting, its got a much bluer flame than mine! Did you or smithy get it to light at higher P2's in the end? The spray patterns in these things must become some kind of invisible dark art, but if I was to make another I think I would be tempted to copy your offset drilling idea and maybe position the sparkplug bang in the middle of the length rather than near the diameter step change!
Cheers
Scott
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Post by racket on Jun 23, 2020 22:48:31 GMT -5
Hi Scott At high power settings we can have exhaust gases travelling at maybe 800+ ft/sec -550 MPH straight towards those jets of fuel exiting the spray ring holes , they haven't got a hope in hell of sufficiently dispersing radially in the half millisecond it takes for the gases to pass by the holes and be ejected into the main body of the A/B where the fuel/air mix is suppose to recirculate at the step and be ignited by the spark plug. The AiResearch A/B used radial injection from the wall into the gas stream, this guaranteed that there was always fuel being carried rearwards near the wall to empty into the recirculation zone for ignition . Smithy has been using "hot streak" on both the GT6041 and his RC jet dragster www.youtube.com/watch?v=1XqoYhSxKCg . I never had much luck getting the A/B to light when the 6 inch A/B was fitted, as me being me, wanted to try something different , but the 400 f/sec gas speed limit was being bumped up against in such a skinny pipe , once Smithy went to a bigger pipe combustion wasn't a problem. Hot streak has been used "forever" to light A/Bs of all sizes , you just need to be careful about making sure it shuts off properly . Your plug position isn't the problem, its having a combustable mix between the plug gap thats the problem , we need some fuel near the wall . Cheers John |
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Post by slittlewing on Jun 26, 2020 3:59:25 GMT -5
Thanks for the explanation and info John, I am not that familiar with hot streak but I understand its somehow injecting a long stream of liquid kero that passes through the turbine and then lights the AB? I had another thought.. I could drill a small 1mm hole in the feed tube to the "injection ring" (facing the turbine again) really close to the wall where it is welded in, quite easily on my AB. Could be worth a go at a later stage! So during the past couple of weeks I have been through a very long jobs list on the bike ahead of potential "test ride"... I pulled the combustor out of the bike which meant also taking all the pumps out and basically taking it back to a bare frame with the turbo sat in it! Many hours later its back in, sealed with new gasket and JB Weld "Extreme Heat" paste to the turbine flange. I have been over every single fluid connection, fitted bonded washers where possible instead of copper ones etc. I also fitted a new silicone air/boost hose between the turbo and combustor, oil had been seeping out of the combustor connection. I think my turbo being angled down at 20 degrees or so means some oil pools in the front of the bearing housing and spins off the compressor. As my hose connections are to plain un-swaged tube, I also put some silicone sealant in for good measure and it seems dry now. I also replaced the rubber hose from my turbo oil drain to tank with a silicone one. The dessicant breather fits and is on the bike for the next test  I also made one of the last outstanding parts, the "air filter" from a kitchen sieve. The aluminium bellmouth is bonded to a 3d printed collar that sits inside the compressor inlet and was glued in. With the compressor getting warm, the PLA had "shrunk" and on one of my static tests, the bellmouth fell out. I have no lathe and cant get an alu collar made, so I 3d printed another but this time designed it to have minimal surface contact with the compressor housing (just a few ribs) and also much thicker. I have bonded it in with "tiger seal" which I gather is pretty strong s**t! Will see how it goes!      The brakes on the bike have been piped up too. The last component that I am yet to make is the front fairing (where the headlight would be), for which I am still waiting for PLA to be available in the right colour from a specific manufacturer so I can print it. Cheers Scott |
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Post by slittlewing on Jun 28, 2020 11:47:12 GMT -5
Hi Chaps, Something to give you a little amusement... a video I did a few weeks back (but never got round to posting online) of the "Smoke Test"....  I have some really great news... I finally found somewhere local to me to take the bike for some testing, and finally performed a successful "shakedown" test and rode the bike!! I am getting hold of the footage from my friends and helpers and I will post a video up soon, absolutely over the moon with how reliably the bike performed. It had one oil leak from the turbo drain hose, which was rectified before running - otherwise everything went smoothly. I had working TOT until I afterburned (guess the AB spark is also killing the signal) and after a static "extended full throttle" test (seemed like more than a minute at 2 bar P2) the TOT got to 670 and was almost stable. I know the "safe limit" is supposed to be 650 but do you think I am OK to keep the current fuelling? Many thanks Scott |
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Post by racket on Jun 28, 2020 18:28:29 GMT -5
Hi Scott
Thats great news :-)
670C should be fine
Looking forward to video of the test ride
Cheers
John
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Post by slittlewing on Jul 2, 2020 15:53:54 GMT -5
Well after a fair bit of editing I finally got the "full quality" clips of the test ride today... A big thankyou to everyone for all their help to get to this point Hope this provides you with some laughs haha Cheers, Scott |
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