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-   -   a couple printed ideas (https://vansairforce.net/community/showthread.php?t=147771)

rv7charlie 07-11-2018 09:27 PM

Try moving the start of the flair farther downstream, so the max area isn't achieved until it touches the face of the core. Also, 'invert' the transitions from round to square in the corners. Then re-run the analysis.

Then for grins, move the round section so it's centered on the face, with symetrical flairs to the edges, and re-run.

Charlie

Steve Melton 07-11-2018 09:34 PM

Quote:

Originally Posted by rv7charlie (Post 1272861)
Try moving the start of the flair farther downstream, so the max area isn't achieved until it touches the face of the core. Also, 'invert' the transitions from round to square in the corners. Then re-run the analysis.

Then for grins, move the round section so it's centered on the face, with symetrical flairs to the edges, and re-run.

Charlie

thx for the help on this. Charlie wants the inlet shifted to pilot's side to clear a cable and maybe space limited vertically so I'm trying to make it compact. I plan to recontour and add an internal vane.

rv7charlie 07-11-2018 09:43 PM

Sorry; my posts are purely about diffuser efficiency. The requesters may have specific needs when it comes to duct positioning.

If installation needs allow it, and you try the shape changes, you *might* not need the turning vane.

edit: duh; two Charlies; missed that it was another Charlie that requested the design

Steve Melton 07-11-2018 09:50 PM

Quote:

Originally Posted by rv7charlie (Post 1272864)
Sorry; my posts are purely about diffuser efficiency. The requesters may have specific needs when it comes to duct positioning.

If installation needs allow it, and you try the shape changes, you *might* not need the turning vane.

appreciate the help, really. BTW the area ratio on this = 2. if we had the room we could make an efficient diffuser.

rv7charlie 07-11-2018 10:17 PM

If you're talking inlet/core area ratio, the K&W ratios go beyond 3-1 with fairly short duct length. The example in the book has a rectangular inlet the same width as the core, with a flair on only one side. Very similar to the offset inlet in your drawing.

I initially found the info on shapes somewhat counter-intuitive, but there was test data demonstrating the efficiency.

Steve, check your PMs in a few minutes for more info.

Charlie

Zuldarin 07-12-2018 08:14 AM

Quote:

Originally Posted by Steve Melton (Post 1272856)
ABS may be able to survive on the firewall if it was trapped by fiberglass.

Just a data point for you Steve. I printed up an ABS oil cooler inlet shroud for my firewall mounted oil cooler last year. I flew it all summer including to Oshkosh and it had zero degradation that I could detect. On the flip side I also printed up an outlet duct and the radiant heat from the exhaust caused a slight bit of warping on that one so I removed it. Neither of these were reinforced by fiberglass at the time. The inlet duct is protected from exhaust radiant heat so the only heat I had to worry about was the ambient temps under the cowl and the temperature of the oil cooler itself. Neither of those were high enough to cause the plastic to soften.

This year when I replace my oil cooler I printed up a new inlet duct and put a couple of layers of carbon fiber over the duct for added security.

Chkaharyer99 07-12-2018 08:37 AM

Quote:

Originally Posted by Zuldarin (Post 1272946)
Just a data point for you Steve. I printed up an ABS oil cooler inlet shroud for my firewall mounted oil cooler last year. I flew it all summer including to Oshkosh and it had zero degradation that I could detect. On the flip side I also printed up an outlet duct and the radiant heat from the exhaust caused a slight bit of warping on that one so I removed it. Neither of these were reinforced by fiberglass at the time. The inlet duct is protected from exhaust radiant heat so the only heat I had to worry about was the ambient temps under the cowl and the temperature of the oil cooler itself. Neither of those were high enough to cause the plastic to soften.

This year when I replace my oil cooler I printed up a new inlet duct and put a couple of layers of carbon fiber over the duct for added security.

Darin,

Will you put the carbon fiber on the inside or outside or both inside and outside.

Zuldarin 07-12-2018 09:24 AM

Quote:

Originally Posted by Chkaharyer99 (Post 1272953)
Darin,

Will you put the carbon fiber on the inside or outside or both inside and outside.

I wrapped it on the outside. Its only there for structural support. I also inserted a 1" metal ring at the top so the hose clamp that holds the air ducting in place doesn't compress the glass/plastic if it gets too warm.


Chkaharyer99 07-12-2018 01:06 PM

Quote:

Originally Posted by Zuldarin (Post 1272961)
I wrapped it on the outside. Its only there for structural support. I also inserted a 1" metal ring at the top so the hose clamp that holds the air ducting in place doesn't compress the glass/plastic if it gets too warm.


Thank you. I was going to ask more questions but looked here ( www.darinanderson.com ) and saw your process. Nice work. Thanks again.

Steve Melton 07-12-2018 05:36 PM

a short vane inside has better distribution. should not be too difficult to construct.










no vane version, same mass flow



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