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Thread: Hunting for microknots

  1. #21

    Default Re: Hunting for microknots

    Figured I would share the pictures of the exhaust augmenters. The goal was to turn the exhaust pipe more horizontal, because the exhaust gases coming down and away from the belly is a source of drag. It's the same idea behind Conquest 1's exhaust pipes being brought closer to the fuselage. Like Conquest 1, the problem became how to do that without catching the fuselage on fire.

    Enter the Exhaust Augmenter/Ejector. Here's a link with a system diagram.
    http://croll.com/vacuum-systems/appl...ocessing/24-2/

    We cut the exhaust pipe and fabricated a new downstream pipe, with a diameter greater than the diameter of the exhaust.
    Click image for larger version. 

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    Click image for larger version. 

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    The idea is the exhaust goes into the downstream pipe with a very high velocity creating a low pressure area in the center.
    Click image for larger version. 

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    This "sucks" additional air from the cowling into the downstream pipe. The hot air from the turbo and the substantially cooler air from the cowling mix in the pipe and are ejected out the back.
    Click image for larger version. 

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    The chevrons are something we found on one of the speed record cars, Paul Bonhomme's Red Bull Racer, and the shrouds on the new high bypass turbine engines.
    Click image for larger version. 

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    They are primarily used to mitigate the sound, but they do that by promoting better mixing of the air inside and outside the exhaust (imagine two small vortices rolling along the diagonal edges of the chevrons), which suited our purposes since we were looking to cool the exhaust gases and keep the belly from catching on fire.

    Another thing we tried was copying the new Ford and Chevy pickups (you'll notice them if you know to look for them), they have a secondary cooling inlet to introduce cool air further down the pipe. So we incorporated that as well.
    Click image for larger version. 

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    I don't remember numbers but we saw very substantial reductions in temperatures on the belly (so much so it was cooler than the stock exhaust). The main draw back is they make it really frickin' loud in the cockpit.
    It's not a very flashy mod, since you really can't tell it's there from the outside, but it's another one of those things that adds up in the end.

    -Thomas
    "young" Thomas

  2. #22
    Join Date
    Sep 2009
    Location
    germany
    Posts
    35

    Default Re: Hunting for microknots

    I just want to say thank you for sharing all this technical stuff. I`m checking this post daily in the hope to find a new post.
    It would be great if you continue sharing this kind of Information. Im sure a lot of poeple like what you are writing!


    Best regards
    Franz

  3. #23
    Join Date
    Nov 2006
    Location
    Sao Paulo, Brazil
    Posts
    876

    Default Re: Hunting for microknots

    Quote Originally Posted by CubersWrist View Post
    Figured I would share the pictures of the exhaust augmenters. The goal was to turn the exhaust pipe more horizontal, because the exhaust gases coming down and away from the belly is a source of drag. It's the same idea behind Conquest 1's exhaust pipes being brought closer to the fuselage. Like Conquest 1, the problem became how to do that without catching the fuselage on fire.

    Enter the Exhaust Augmenter/Ejector. Here's a link with a system diagram.
    http://croll.com/vacuum-systems/appl...ocessing/24-2/

    We cut the exhaust pipe and fabricated a new downstream pipe, with a diameter greater than the diameter of the exhaust.
    Click image for larger version. 

Name:	IMG_4273.jpg 
Views:	130 
Size:	624.3 KB 
ID:	23342
    Click image for larger version. 

Name:	IMG_4261.jpg 
Views:	139 
Size:	991.2 KB 
ID:	23339
    The idea is the exhaust goes into the downstream pipe with a very high velocity creating a low pressure area in the center.
    Click image for larger version. 

Name:	IMG_4281.jpg 
Views:	145 
Size:	1.16 MB 
ID:	23340
    This "sucks" additional air from the cowling into the downstream pipe. The hot air from the turbo and the substantially cooler air from the cowling mix in the pipe and are ejected out the back.
    Click image for larger version. 

Name:	IMG_4288.jpg 
Views:	147 
Size:	633.7 KB 
ID:	23341
    The chevrons are something we found on one of the speed record cars, Paul Bonhomme's Red Bull Racer, and the shrouds on the new high bypass turbine engines.
    Click image for larger version. 

Name:	IMG_4276.jpg 
Views:	145 
Size:	1.13 MB 
ID:	23343
    They are primarily used to mitigate the sound, but they do that by promoting better mixing of the air inside and outside the exhaust (imagine two small vortices rolling along the diagonal edges of the chevrons), which suited our purposes since we were looking to cool the exhaust gases and keep the belly from catching on fire.

    Another thing we tried was copying the new Ford and Chevy pickups (you'll notice them if you know to look for them), they have a secondary cooling inlet to introduce cool air further down the pipe. So we incorporated that as well.
    Click image for larger version. 

Name:	IMG_4280.jpg 
Views:	196 
Size:	1.19 MB 
ID:	23344

    I don't remember numbers but we saw very substantial reductions in temperatures on the belly (so much so it was cooler than the stock exhaust). The main draw back is they make it really frickin' loud in the cockpit.
    It's not a very flashy mod, since you really can't tell it's there from the outside, but it's another one of those things that adds up in the end.

    -Thomas
    I have a couple of quick questions for you.
    Are you using an air pump to introduce the cool air?
    Do you have a venturi tube inside the pipe to improve suction and to prevent the exhaust pulses from interacting with the cold air inlets?
    On car smog equipment they use a simple check valve on the air injectors, although the back pressure from the cat-cons create most of this need.
    will you plumb the cold air lines to the front of the cowl to take advantage of higher ram air pressures? A NACA duct may work with no drag.

  4. #24

    Default Re: Hunting for microknots

    Quote Originally Posted by Bob View Post
    I have a couple of quick questions for you.
    Are you using an air pump to introduce the cool air?
    Do you have a venturi tube inside the pipe to improve suction and to prevent the exhaust pulses from interacting with the cold air inlets?
    On car smog equipment they use a simple check valve on the air injectors, although the back pressure from the cat-cons create most of this need.
    will you plumb the cold air lines to the front of the cowl to take advantage of higher ram air pressures? A NACA duct may work with no drag.
    First it is worth noting that these are the 2016 augmenters. I'll get to the 2017 augmenters at the end (but they don't look as cool)

    We don't have a separate air pump or have separate cold air lines. We are using the ambient air in the low pressure area. Which works because it's all about temperature difference. That air gets cooled by the spray bars before picking up the heat from the cylinder fins. That air isn't "cold" per se, but it is a whole lot cooler than the air coming out of the turbo. So this also means we don't need to worry about any type of inlets or NACA ducts for the cooling lines.

    We didn't include a venturi or an expanding section in the augmenter though we did make a test piece with a big bellmouth, straight mixing section, and diverging section (looks like a small windtunnel), but we ran into several competing criteria.
    1. Augmenters efficiency improves when the ratio of mixing-section-cross-sectional-area to downpipe-cross-sectional-area
    increases.
    2. Open space. There isn't much of it down there.
    3. We don't want to slow or restrict the flow coming out of the turbo which would lead to an increase in back pressure.

    So our theory was if Area1*Velocity1=Area2*Velocity2 and we don't want the flow to slow down, then we didn't think we needed to expand the pipe (probably wouldn't have hurt though).

    For 2017 we simplified everything based on criteria 1 and 2. So now all we have is a straight pipe to maximize the area ratio, which did in fact improve the pressure difference above and below the engine.
    Click image for larger version. 

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    "young" Thomas

  5. #25
    Join Date
    Nov 2006
    Location
    Sao Paulo, Brazil
    Posts
    876

    Default Re: Hunting for microknots

    Last question for you.

    If you lose spark in a cylinder will the resulting dump of unburned air and fuel cause flame to enter the motor bay because of the open air inlet? The resulting explosion from the raw fuel could cause a big over pressure. And thank you for taking the time to discuss this with me. Its a real treat to see what you are doing.

  6. #26

    Default Re: Hunting for microknots

    Quote Originally Posted by Bob View Post
    Last question for you.

    If you lose spark in a cylinder will the resulting dump of unburned air and fuel cause flame to enter the motor bay because of the open air inlet? The resulting explosion from the raw fuel could cause a big over pressure. And thank you for taking the time to discuss this with me. Its a real treat to see what you are doing.
    You're welcome. Had to phone a friend on this one.
    "No, it will burn pre-turbo and there is enough flow to send it out the back of the augmenter."



    Also Andy sent me the data for the augmenters.
    exhaust temp at the exit dropped from 1300F to 600F, the belly temps dropped from 170F to 140F, and the pressure difference across the high and low pressure areas increased by 2 inH2O. So we are getting suction from the exhaust to help pull more air through the engine. This is great, because it is possible for air to spill out of the inlets (even to the point where air will enter the inlet, turn around and come back out). That's a ton of drag and hurts cooling.
    "young" Thomas

  7. #27
    Join Date
    Sep 2014
    Location
    Idaho
    Posts
    34

    Default Re: Hunting for microknots

    Nice work! I love seeing this stuff. Great idea on cooling the exhaust. I have been studying stuff like this recently. Cool to see someone using it.

  8. #28
    Join Date
    Nov 2004
    Location
    Napa Ca
    Posts
    1,134

    Default Re: Hunting for microknots

    Quote Originally Posted by CubersWrist View Post
    You're welcome. Had to phone a friend on this one.
    "No, it will burn pre-turbo and there is enough flow to send it out the back of the augmenter."



    Also Andy sent me the data for the augmenters.
    exhaust temp at the exit dropped from 1300F to 600F, the belly temps dropped from 170F to 140F, and the pressure difference across the high and low pressure areas increased by 2 inH2O. So we are getting suction from the exhaust to help pull more air through the engine. This is great, because it is possible for air to spill out of the inlets (even to the point where air will enter the inlet, turn around and come back out). That's a ton of drag and hurts cooling.
    Wow, those are some impressive numbers. Volumetric efficiency is a good thing, reversion is a bad thing. More VE and less reversion is more power and speed.

    Will

  9. #29

    Default Re: Hunting for microknots

    Doing some CAD this evening and needed to refer to some old pictures.
    During my digging I found this video from last year.
    https://photos.app.goo.gl/Lvd9rqshEFEuz7kA7

    Pretty this was the week before Reno when the race pistons (with a custom profile) were installed.
    "young" Thomas

  10. #30

    Default Re: Hunting for microknots

    Not sure this is going to work for those without fb but here is a teaser of the new paintscheme.
    https://www.facebook.com/14778132891...1893962705585/

    Screenshot just to be safe
    Click image for larger version. 

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    Last edited by CubersWrist; 08-03-2018 at 11:22 AM.
    "young" Thomas

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