Hunting for microknots

[Desertdawg]

Re: Hunting for microknots

Paint teaser!
[ATTACH=CONFIG]23325[/ATTACH]

Can't wait to see her. I'll be by with some Section 3 decals :-)

[Fence Sence]

Re: Hunting for microknots

Must be getting close to September. The smell of fresh paint. Ahhhhh.

[CubersWrist]

Re: Hunting for microknots

This thread is one of the most informative and educational. Thank you for the updates.

I’m glad to hear it. I’ve learned a lot over the last couple years and trying to pass that along.

Again if you have questions about any of the speed mods(sport, unlimited, whatever) or how they work feel free to ask.

We got a lot of work to do once the painting is done. The plenum is going to be improved to fit around the new intake tube, going to keep tweaking the exhaust augmenters (which I don’t think I’ve posted about before?), and spray bars have always been a bit of a mess (nozzles and tubes going everywhere) so trying to make that cleaner too.

[GRNDP51]

Re: Hunting for microknots

I’m glad to hear it. I’ve learned a lot over the last couple years and trying to pass that along.

Again if you have questions about any of the speed mods(sport, unlimited, whatever) or how they work feel free to ask.

We got a lot of work to do once the painting is done. The plenum is going to be improved to fit around the new intake tube, going to keep tweaking the exhaust augmenters (which I don’t think I’ve posted about before?), and spray bars have always been a bit of a mess (nozzles and tubes going everywhere) so trying to make that cleaner too.

What’s the idea for the plenum? Grove’s looks pretty nice

[CubersWrist]

Re: Hunting for microknots

What’s the idea for the plenum? Grove’s looks pretty nice

He has a Lycoming which has less “stuff” on the top of the engine. I think this helps a lot with getting air to the cylinders and for getting the plenum to fit cleanly. The Lycoming also has some convenient flanges to be used in mounting the plenum. We narrowed the plenum last year when we changed the intake tube. We had all this empty space inside the plenum where the intake tubes usd to be and it was causing a lot of turbulence and messing with the cylinder temps. So we had to scratch the brackets we were using to mount the plenum. What we had worked it just wasn’t ideal given the time crunch.

As for this year we still have a time crunch but it’s more refinement rather than making something new, so hopefully it won’t be so much work. As for the specifics of what we will change, we’re focusing on making the transitions between the inlets and diffuser sections smoother (rule of thumb for diffusers is a 7deg expanding cone, much more than that and you risk air separation and turbulence inside the plenum which does bad things for cooling)

[CubersWrist]

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/applications/chemical-processing/24-2/

We cut the exhaust pipe and fabricated a new downstream pipe, with a diameter greater than the diameter of the exhaust.


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

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.

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.

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.


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

[glider69]

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. I´m sure a lot of poeple like what you are writing!


Best regards
Franz

[Bob]

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/applications/chemical-processing/24-2/

We cut the exhaust pipe and fabricated a new downstream pipe, with a diameter greater than the diameter of the exhaust.
[ATTACH=CONFIG]23342[/ATTACH]
[ATTACH=CONFIG]23339[/ATTACH]
The idea is the exhaust goes into the downstream pipe with a very high velocity creating a low pressure area in the center.
[ATTACH=CONFIG]23340[/ATTACH]
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.
[ATTACH=CONFIG]23341[/ATTACH]
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.
[ATTACH=CONFIG]23343[/ATTACH]
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.
[ATTACH=CONFIG]23344[/ATTACH]

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.

[CubersWrist]

Re: Hunting for microknots

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.

[Bob]

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.

[CubersWrist]

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.

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.

[rchevyman]

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.

[RAD2LTR]

Re: Hunting for microknots

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

[CubersWrist]

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.

[CubersWrist]

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