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  #31  
Old 05-01-2020, 08:38 AM
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agirard7a agirard7a is offline
 
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Location: Newport, RI
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Default Question

I like this design and idea. I have a question. Would it be better if it was a closed loop cycling air within the engine so not to have to remove the humidity from the ambient air constantly? Just a thought.
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  #32  
Old 05-01-2020, 06:17 PM
BillL BillL is offline
 
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Quote:
Originally Posted by agirard7a View Post
I like this design and idea. I have a question. Would it be better if it was a closed loop cycling air within the engine so not to have to remove the humidity from the ambient air constantly? Just a thought.
No - why?? Here is why.

1. The objective is to replace the air in the crankcase with dry (low dew point) air.
2. The mixture after shutdown in the crankcase measured as lbs water/lbs dry air is many times higher than ambient.
3. The run time to replace the crankcase air to a 99% certainty is the same in either case.

So, if the crankcase volume time is know for a particular system, then simply use a timer and then shut off the desiccant system.

Make sense?

Quote:
Originally Posted by dpansier View Post
Thanks for the data Bill, based on your description, I'm invisioning your doing the following.
Are you using a 120 volt blower?
I have used Duck Bill valves in the past and they may work well in this application as check valves.
Well, yes, basically Don, but the break pressure on check valves I could find was too high, so at the moment I have some 3-way valves. I would sure like to use a low opening pressure check valve with the configuration you showed. So Please, tell me more about this Duck Bill valve. I can imagine how it works, like the reed block on a 2-stroke engine or the back flow plates on the V-1 buzz bomb? But where can I get some?

The forward pressure of the aquarium pump is not very high so a valve must seal on it's own and not leak. A different design air pump could be needed to handle higher pressures. These are reliable and low cost.
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RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”

Last edited by BillL : 05-01-2020 at 06:29 PM.
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  #33  
Old 05-01-2020, 06:31 PM
PilotjohnS PilotjohnS is offline
 
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Location: Southwest
Posts: 1,119
Default Scuba dive shop

You might find a valve at a scuba dive shop. Some snorkels have these low pressure air valves.
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

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  #34  
Old 05-01-2020, 07:17 PM
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dpansier dpansier is offline
 
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Location: Green Bay, WI (GRB)
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Quote:
Originally Posted by BillL View Post


Well, yes, basically Don, but the break pressure on check valves I could find was too high, so at the moment I have some 3-way valves. I would sure like to use a low opening pressure check valve with the configuration you showed. So Please, tell me more about this Duck Bill valve. I can imagine how it works, like the reed block on a 2-stroke engine or the back flow plates on the V-1 buzz bomb? But where can I get some?

A Duckbill valve has an extremely low cracking pressure and seals very well against back flow. Most are made of Silicone rubber and are widely used in the medical and some food related applications.
Amazon has them listed for replacement parts for Breast pumps. Example here:

My experience has been with valves produced by Vernay, link here
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Green Bay, WI (GRB)
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Last edited by dpansier : 05-01-2020 at 07:23 PM. Reason: Additional info
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  #35  
Old 05-01-2020, 07:42 PM
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Pilot135pd Pilot135pd is offline
 
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Location: Vaca Moo Airport - TA37 in East TEXAS
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Quote:
Originally Posted by dpansier View Post
...Amazon has them listed for replacement parts for Breast pumps.
Now what kind of search where you doing when you found that out?
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  #36  
Old 05-01-2020, 08:30 PM
BillL BillL is offline
 
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Quote:
Originally Posted by dpansier View Post
A Duckbill valve has an extremely low cracking pressure and seals very well against back flow. Most are made of Silicone rubber and are widely used in the medical and some food related applications.
Amazon has them listed for replacement parts for Breast pumps. Example here:

My experience has been with valves produced by Vernay, link here
It sure looks like I have some more component development to do, and this looks very promising! Forward pressure drop, and cracking pressure along with back leak will all have to be measured to ensure the performance remains. I am also looking at a paper element inline fuel filter for the final control of contaminants getting into the engine. Thanks.

For short trips, less than a month, a battery powered purge design is also in the works. No drying action just a 3-5 min blast with a separate battery to prevent any condensation, same 5 min mechanical timer. Hook it up upon exiting the aircraft, store gear, gust locks, etc, then remove and restore the dipstick before leaving the ramp/hangar.
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Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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  #37  
Old 05-01-2020, 08:41 PM
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dpansier dpansier is offline
 
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Quote:
Originally Posted by BillL View Post
It sure looks like I have some more component development to do, and this looks very promising! Forward pressure drop, and cracking pressure along with back leak will all have to be measured to ensure the performance remains. I am also looking at a paper element inline fuel filter for the final control of contaminants getting into the engine. Thanks.
This valve would work down stream of the aquarium pump.
I have tested it with the small flow meter you listed and show 2 liters/ min flow with it inline, no flow reduction.
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  #38  
Old 05-02-2020, 09:00 AM
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Snowflake Snowflake is offline
 
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Default

Spitballing here but I wonder if a PCV (Positive Crankcase Ventilation) valve from a car would work? I remember replacing one in my Civic many years ago and I recall it didn't take much pressure to get it to move.
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  #39  
Old 05-02-2020, 09:11 AM
moosepileit moosepileit is offline
 
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Location: Floyds Knobs, IN
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How about a 2 min shot of shop air in the breather, dipstick open, postflight?

Can you flush enough saturated vapor with fresh air to make a difference?

Lots seem to open the dipstick.
Lots use Camguard.
Some use an air drying system.

In any of the cases, would a fresh air flush make a measureable difference?

Keep a closed loop cleaner, give longer between bakes for open and closed loop silica gel? Best if oil at or above 150/180/?
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  #40  
Old 05-02-2020, 12:42 PM
BillL BillL is offline
 
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Location: Central IL
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Quote:
Originally Posted by moosepileit View Post
How about a 2 min shot of shop air in the breather, dipstick open, postflight?

Can you flush enough saturated vapor with fresh air to make a difference?

Lots seem to open the dipstick.
Lots use Camguard.
Some use an air drying system.

In any of the cases, would a fresh air flush make a measureable difference?

Keep a closed loop cleaner, give longer between bakes for open and closed loop silica gel? Best if oil at or above 150/180/?
1. My calculation for a 4 gal crankcase cavity, assuming instant dilution for each cc entering, is it will take 145 liters of air to replace the interior volume to less than 1% of original content. A "fresh" air flush is the same as an ambient purge. (?)
2. The only purpose behind the "purge" is to prevent any possible condensation as the blow-by assumed to have dew point around 180F. I have been too lazy to do the combustion calculation for water density relative to dry air and compare to the steam tables.

So- IMO yes an air compressor blast would work. Must be filtered though. And - the only reason I can fathom for a continuous dry air system is the possibility for condensation that will take time to evaporate. In theory, assuming my calculations are correct, a 3 L/min dry air supply will reach 99% purge in 30 min but would leave it on for an hour.

Although the 3 min purge did yield ambient humidity in the exit stream at the end (and semi-validated the calculation), I have not tested the dry-30min-3L/m stage.
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RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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