X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from EXHUB003-2.exch003intermedia.net ([207.5.74.29] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTPS id 3816959 for flyrotary@lancaironline.net; Tue, 18 Aug 2009 12:01:44 -0400 Received-SPF: none receiver=logan.com; client-ip=207.5.74.29; envelope-from=jwhaley@datacast.com Received: from EXVMBX003-5.exch003intermedia.net ([207.5.74.45]) by EXHUB003-2.exch003intermedia.net ([207.5.74.29]) with mapi; Tue, 18 Aug 2009 09:01:08 -0700 From: Jeff Whaley To: Rotary motors in aircraft Date: Tue, 18 Aug 2009 09:01:06 -0700 Subject: RE: [FlyRotary] Swirl pots ... coolant and dish soap. Thread-Topic: [FlyRotary] Swirl pots ... coolant and dish soap. Thread-Index: AcogGB143YbLc11QQs2YbF/zBgEI0gABGOWQ Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_C03ABB0A7362B84BB53D544B3C305E0E0140E9BEE678EXVMBX0035e_" MIME-Version: 1.0 --_000_C03ABB0A7362B84BB53D544B3C305E0E0140E9BEE678EXVMBX0035e_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable I believe adding dish soap or water wetter is supposed to reduce surface te= nsion between coolant and block. What is the measured net benefit of either additive? 1%-5% improved cooling= ? Jeff From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Beh= alf Of Lynn Hanover Sent: Tuesday, August 18, 2009 11:24 AM To: Rotary motors in aircraft Subject: [FlyRotary] Swirl pots Ed has all of the smarts on this. So pay attention when he writes anything. And now the Larch..................... I hate to see a rotary engine go down the drain because the engine overheat= ed on the first start. And a lot of them do die that way. The water pump is= installed at the top of the engine, and will use any excuse to cavitate an= d stop pumping coolant. It has no head on it. Pump talk for water pressure = caused by the weight of water above the pump. So a very small amount of air= behind the pump will stop it. I have a Shrader valve on my make up tank, and charge the system to relief = pressure before starting the engine. In the olden days, that center iron had a flat spot with some kind of fat s= ensor stuck in it with two nice threaded holes along side. That hole got a = flat plate with a Shrader valve sans core installed. A nice metal cap on th= e valve body kept the coolant inside. On a new fill up, you take that cap o= ff and pour in coolant until it came out of the Shrader valve with no bubbl= es. Then put the cap back on. Fast, simple, cheap. I should have removed the restrictor from the drawing before posting it. It= begs for comment. It is probably of no value in an aircraft application. Here is my thinking on that piece of the system, backed up by observation = only and no technical understanding or evidence. On my flow bench I see a vena contracta around all exposed tube ends, (like= the raw end of the shop vac hose) that reduces the effective diameter of t= he hose. The air making a 180 degree turn around the end of the tube imping= es on air flowing into the tube at any angle less than 180 into the tube. S= o the CFM you would calculate for the tube diameter and pressure will be ab= out half of the calculated flow when tested. The smaller the tube diameter the more profound the effect. Now look into t= he tank on a radiator and notice the flattened tubes sticking up from the f= lat tank floor. Any vena contracta going on in there? And it is in a liquid, way worse than flowing air. While raising the pressure around the end of the tube, flow does not improv= e as an exact function of pressure. Or, doubling the pressure does not doub= le the flow. And now more bad news. The same construction at the outlet end= of the tubes creates another interesting condition, where high velocity fl= ow from the raw tube end, creates a high pressure differential between the = flow and coolant at rest in the tank, that caused the low speed coolant to = constrict the flow exiting the tube. You can see this on a humid day when a= war bird revs up for take off. The vapor rings from the prop tips are comp= ressed inward and stay closely attached to the fuselage. Or, a vena contrac= ta observable in broad daylight. I deduce from this that there is a considerable restriction involved in for= cing coolant through a radiator. I am not alone in this thinking. Notice that the lower radiator hoses on ca= rs have a spiral of wire installed to prevent the collapse of the hose at h= igh engine speed. Even with the use of modern higher pressure caps now comm= on. Notice also that the lower hoses are larger in diameter than the upper= hoses. So, the radiator, like the power valve or restrictor in a Freon system, whe= re a restriction of some sort is required to generate a pressure differenti= al. Unlike a Freon system that pressure differential is of no value in our = cooling systems. So, the radiator(s) are the biggest restrictor in the loop, and the lowest = system pressure is likely to be found between the radiator(s) and the pump = inlet. When that pressure drops below local air pressure the lower hose would collapse if it were not for the wire inside, your 22 p= ound pressure cap be damned. So, the restrictor, limits the pressure differential across the radiator, a= nd helps prevent pump cavitation that shortens the vanes on the pump and re= nders it ineffective. When you are shifting at 9,600 RPM and miss the shift= , (the rev chips are 9,600s) or the driver selects 1st instead of 3rd succe= ssfully (easy with dog rings) and the revs go to the moon, then the restric= tor is a help. For airplanes, not so much.................Sorry for any confusion. Lynn E. Hanover --_000_C03ABB0A7362B84BB53D544B3C305E0E0140E9BEE678EXVMBX0035e_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

I believe adding dish soap or water wetter is supposed to re= duce surface tension between coolant and block.

What is the measured net benefit of either additive? 1%-5% i= mproved cooling?

Jeff

 

From: Rotary motors= in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Lynn Hano= ver
Sent: Tuesday, August 18, 2009 11:24 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Swirl pots

 

Ed has all of the smarts on this. So pay attention whe= n he writes anything.

 

And now the Larch.....................

 

I hate to see a rotary engine go down the drain becaus= e the engine overheated on the first start. And a lot of them do die that way. Th= e water pump is installed at the top of the engine, and will use any excuse t= o cavitate and stop pumping coolant. It has no head on it. Pump talk for water pressure caused by the weight of water above the pump. So a very smal= l amount of air behind the pump will stop it.

 

I have a Shrader valve on my make up tank, and charge = the system to relief pressure before starting the engine.

 

In the olden days, that center iron had a flat spot wi= th some kind of fat sensor stuck in it with two nice threaded holes along side= . That hole got a flat plate with a Shrader valve sans core installed. A nice metal cap on the valve body kept the coolant inside. On a new fill up, you = take that cap off and pour in coolant until it came out of the Shrader valve wit= h no bubbles. Then put the cap back on. Fast, simple,

cheap.  

 

I should have removed the restrictor from the drawing = before posting it. It begs for comment. It is probably of no value in an aircraft application.

 

Here is my thinking on that piece of the system, backe= d up  by observation only and no technical understanding or evidence.

 

On my flow bench I see a vena contracta around all exp= osed tube ends, (like the raw end of the shop vac hose) that reduces the effecti= ve diameter of the hose. The air making a 180 degree turn around the end of th= e tube impinges on air flowing into the tube at any angle less than 180 into = the tube. So the CFM you would calculate for the tube diameter and pressure wil= l be about half of the calculated flow when tested.

 

The smaller the tube diameter the more profound the ef= fect. Now look into the tank on a radiator and notice the flattened tubes stickin= g up from the flat tank floor. Any vena contracta going on in there?<= /p>

And it is in a liquid, way worse than flowing air.

 

While raising the pressure around the end of the tube, flow does not improve as an exact function of pressure. Or, doub= ling the pressure does not double the flow. And now more bad news. The same construction at the outlet end of the tubes creates another interesting condition, where high velocity flow from the raw tube end, crea= tes a high pressure differential between the flow and coolant at rest in the ta= nk, that caused the low speed coolant to constrict the flow exiting the tube. Y= ou can see this on a humid day when a war bird revs up for take off. The vapor rings from the prop tips are compressed inward and stay closely attached to= the fuselage. Or, a vena contracta observable in broad daylight. 

 

I deduce from this that there is a considerable restri= ction involved in forcing coolant through a radiator. 

 

I am not alone in this thinking. Notice that the lower radiator hoses on cars have a spiral of wire installed to prevent the colla= pse of the hose at high engine speed. Even with the use of modern higher pressu= re caps now common.  Notice also that the lower hoses are larger in diame= ter than the upper hoses.

 

So, the radiator, like the power valve or restrictor i= n a Freon system, where a restriction of some sort is required to generate a pressure differential. Unlike a Freon system that pressure differential is = of no value in our cooling systems.

 

So, the radiator(s) are the biggest restrictor in the = loop, and the lowest system pressure is likely to be found between the radiator(s= ) and the pump inlet. When that pressure drops below local air pressure<= /o:p>

the lower hose would collapse if it were not for = the wire inside, your 22 pound pressure cap be damned.

 

So, the restrictor, limits the pressure differential a= cross the radiator, and helps prevent pump cavitation that shortens the vanes on = the pump and renders it ineffective. When you are shifting at 9,600 RPM and mis= s the shift, (the rev chips are 9,600s) or the driver selects 1st instead of = 3rd successfully (easy with dog rings) and the revs go to the moon, then the restrictor is a help.  

 

For airplanes, not so much.................Sorry for a= ny confusion.

 

Lynn E. Hanover  

 

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