VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #631  
Old 07-11-2018, 10:17 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,449
Default

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
Reply With Quote
  #632  
Old 07-12-2018, 08:14 AM
Zuldarin's Avatar
Zuldarin Zuldarin is offline
 
Join Date: Mar 2013
Location: Snoqualmie, wa
Posts: 322
Default

Quote:
Originally Posted by Steve Melton View Post
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.
__________________
Darin
Snoqualmie WA
RV-9A Flying as of 03/2015
RV-10 Building - Fuselage
www.DarinAnderson.com
2018 donation sent!
Reply With Quote
  #633  
Old 07-12-2018, 08:37 AM
Chkaharyer99 Chkaharyer99 is offline
 
Join Date: Oct 2011
Location: Pilot Hill, CA
Posts: 829
Default

Quote:
Originally Posted by Zuldarin View Post
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.
__________________
Charlie
RV-8
Reply With Quote
  #634  
Old 07-12-2018, 09:24 AM
Zuldarin's Avatar
Zuldarin Zuldarin is offline
 
Join Date: Mar 2013
Location: Snoqualmie, wa
Posts: 322
Default

Quote:
Originally Posted by Chkaharyer99 View Post
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.

__________________
Darin
Snoqualmie WA
RV-9A Flying as of 03/2015
RV-10 Building - Fuselage
www.DarinAnderson.com
2018 donation sent!
Reply With Quote
  #635  
Old 07-12-2018, 01:06 PM
Chkaharyer99 Chkaharyer99 is offline
 
Join Date: Oct 2011
Location: Pilot Hill, CA
Posts: 829
Default

Quote:
Originally Posted by Zuldarin View Post
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.
__________________
Charlie
RV-8
Reply With Quote
  #636  
Old 07-12-2018, 05:36 PM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
 
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 1,903
Default

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










no vane version, same mass flow

__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 700+ for all

Simplicity is the art in design.

see Amanda Melton for www.rvplasticparts.com

Last edited by Steve Melton : 07-12-2018 at 05:50 PM.
Reply With Quote
  #637  
Old 07-12-2018, 07:07 PM
Chkaharyer99 Chkaharyer99 is offline
 
Join Date: Oct 2011
Location: Pilot Hill, CA
Posts: 829
Default

Quote:
Originally Posted by Steve Melton View Post
a short vane inside has better distribution. should not be too difficult to construct.










no vane version, same mass flow

Looks great Steve.
__________________
Charlie
RV-8
Reply With Quote
  #638  
Old 07-12-2018, 08:50 PM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
 
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 1,903
Default

I hit the button before I went to the airport tonight.

1/2 scale

and BTW, these always need a bulb at the hose connection end or they WILL become loose. I'll add that feature. this is now planned to be an internal layup first. then bond the internal vane secondly. seems that we are getting a plan together.

__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 700+ for all

Simplicity is the art in design.

see Amanda Melton for www.rvplasticparts.com

Last edited by Steve Melton : 07-13-2018 at 05:38 AM.
Reply With Quote
  #639  
Old 07-13-2018, 12:07 PM
Paragon Paragon is offline
 
Join Date: Jul 2014
Location: Cincinnati, OH
Posts: 57
Default

Steve,

I would not put too much effort into designing internal vanes and such, unless you are prepared to very carefully design a lot of them.

Your transition is so abrupt, I doubt you can fill the exit plane with a solid, unseparated flowfield. More likely, with a vane, you will move the separated areas around.

Several things to note:
1. The inlet will have a Pt (or Velocity) profile, the details of which depend on upstream duct shape, inlet conditions, etc. This profile would affect the results substantially.
2. If there is a heat exchanger at the exit plane, that represents a flow restriction that will be felt upstream, so the results of a CFD analysis could be affected by it's presence or lack thereof.

In order to obtain an unseparated profile at the exit of this transition, you would probably need a very carefully designed array of vanes in both directions, like a thrust reverser cascade in concept. Even there, if not well designed, taking into account the inlet profile, the result could be worse than no vanes at all.

I personally would leave out the vane.

Just my $0.02 worth.

-Paragon (CFD Guy)
Cincinnati, OH
Reply With Quote
  #640  
Old 07-13-2018, 03:51 PM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
 
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 1,903
Default

Quote:
Originally Posted by Paragon View Post
Steve,

I would not put too much effort into designing internal vanes and such, unless you are prepared to very carefully design a lot of them.

Your transition is so abrupt, I doubt you can fill the exit plane with a solid, unseparated flowfield. More likely, with a vane, you will move the separated areas around.

Several things to note:
1. The inlet will have a Pt (or Velocity) profile, the details of which depend on upstream duct shape, inlet conditions, etc. This profile would affect the results substantially.
2. If there is a heat exchanger at the exit plane, that represents a flow restriction that will be felt upstream, so the results of a CFD analysis could be affected by it's presence or lack thereof.

In order to obtain an unseparated profile at the exit of this transition, you would probably need a very carefully designed array of vanes in both directions, like a thrust reverser cascade in concept. Even there, if not well designed, taking into account the inlet profile, the result could be worse than no vanes at all.

I personally would leave out the vane.

Just my $0.02 worth.

-Paragon (CFD Guy)
Cincinnati, OH

I am not a CFD expert. I don't want an array of vanes. I am attempting to spread the flow and minimize the dead zone at the abrupt transition. the transition is to clear a prop cable, so it is needed. HX is mounted long side against the firewall, so a guide vane perpendicular to that direction should help even if the air profile is skewed to the backside of the inlet area.

Airflow Systems also uses a guide vane. they have experience with these.

__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 700+ for all

Simplicity is the art in design.

see Amanda Melton for www.rvplasticparts.com

Last edited by Steve Melton : 07-13-2018 at 04:20 PM.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 07:08 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.