X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from nm15-vm0.access.bullet.mail.mud.yahoo.com ([66.94.236.17] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with SMTP id 5112106 for flyrotary@lancaironline.net; Fri, 02 Sep 2011 15:21:59 -0400 Received-SPF: none receiver=logan.com; client-ip=66.94.236.17; envelope-from=ceengland@bellsouth.net Received: from [66.94.237.126] by nm15.access.bullet.mail.mud.yahoo.com with NNFMP; 02 Sep 2011 19:21:23 -0000 Received: from [66.94.237.117] by tm1.access.bullet.mail.mud.yahoo.com with NNFMP; 02 Sep 2011 19:21:23 -0000 Received: from [127.0.0.1] by omp1022.access.mail.mud.yahoo.com with NNFMP; 02 Sep 2011 19:21:23 -0000 X-Yahoo-Newman-Id: 600398.27582.bm@omp1022.access.mail.mud.yahoo.com Received: (qmail 2443 invoked from network); 2 Sep 2011 19:21:23 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bellsouth.net; s=s1024; t=1314991283; bh=TlxBLWgdvalSev0Pne+aMba6SzLKWdvEJel5GRCJ78c=; h=X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:Date:From:User-Agent:MIME-Version:To:Subject:References:In-Reply-To:Content-Type; b=ZSnQyetf4A22ehFigjm2HQs1aH7b5xpIxPFnpPRBln9/y3ZD024CdDW8Zqpk8hFJptkwhLXWF1SA6n6MlGsxKWc07p9NQRqJcweqgafY+JDZWURz45JNJPoDh8RJp480zG1DRbKtr8zM9/g8U2VFKjF/eGadKRB/GprXULSK0l8= X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: F.X_zH0VM1m15OElrEt5naGT4JI51x4TWUE_iCpavccEnlP FuUvz4_FcUuWMfv7sJ67dC8NZ0E7IdhOUuA8r0CTEInWKf3Wu8TlDJtuUmAX LsIME2QVqOuXJ6kwK5g4VB.uaa2LrCGJLwVOlpKHa2WNKAzFB8cIFYC80Agx 2AQEruwKdjnNhYT0jKN1DLPT8l6LiHx_mphv0x4fYVCWw16UYd0DKjRBtFPc GdEV.ap_Col9gRZ0DjgWsGxi_nhfQ5Pgj_Yc0ZTgLmBeWKU40ppZyRhbfSv0 TXqMod0dD5UeDNBUjnONM7zgAror06YBYZzjXO90YXJPn.qq0TOAg1GYtId9 qCurGKJLrelXAUvbM1QjxE4xCTghFu.wY_xbsCizJvvU_bi14ixi_yrDkGG4 zORApBK0HsUdTabzBBP1QxWsp3DyM7tixTfk0GtHXnMXA5rzsA1q7rTfub83 _KPMcu1k- X-Yahoo-SMTP: uXJ_6LOswBCr8InijhYErvjWlJuRkoKPGNeiuu7PA.5wcGoy Received: from [192.168.10.6] (ceengland@98.95.238.145 with plain) by smtp108.sbc.mail.bf1.yahoo.com with SMTP; 02 Sep 2011 12:21:22 -0700 PDT Message-ID: <4E612CB1.7010200@bellsouth.net> Date: Fri, 02 Sep 2011 14:21:21 -0500 From: Charlie England User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.20) Gecko/20110805 Thunderbird/3.1.12 MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: vapor lock References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------080909040705070800060003" This is a multi-part message in MIME format. --------------080909040705070800060003 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit I'd have to differ on a couple of points. If you must pump to the sump, then the vent can't 'go anywhere' unless you're willing to risk pumping fuel overboard. On a typical RV, it would require removing several dozen screws, the vent line and fuel line, and then removing the tank before I could remove the 6 or 8 screws that hold on the access plate to the tank. So, there is a bit of a maintenance issue for us. If not for that, I'd use in-tank pumps. For my application, the external sump would add more weight/complexity. To the implication that we would choose maintenance ease vs life risk: you have to be honest; *every* decision makes that choice. The safest G/a factory plane in the world uses bolt-on wings instead of a one-piece wing; a one-piece would be both lighter and safer. Charlie On 09/02/2011 01:04 PM, Al Wick wrote: > What fine work Steve. I love it when someone converts theory to facts. > You measured that all at sea level. Now just subtract 5.35 from all > your pressure numbers if you fly at 12k ft. You've now measured all of > the variables that affect vapor lock. Only remaining item is measuring > pressure at your pump inlet. You then can predict exactly how safe > your plane is without ever flying! How cool is that? > I use a submerged fuel pump for added safety. Two actually. Easy to > maintain, just remove the 6 screws that hold the pumps in place. So > there is zero significance to the argument of maintenance. Can't > imagine how anyone could claim maintenance is more important than life > risk anyway. I return all fuel to my 3 gallon sump. Vent can go > anywhere, you don't have to tie vent into main fuel vents. > Once again, nice work Steve. > -al wick > > ----- Original Message ----- > *From:* Steven W. Boese > *To:* Rotary motors in aircraft > *Sent:* Friday, September 02, 2011 12:04 AM > *Subject:* [FlyRotary] vapor lock > > For those concerned about the formation of vapor in a pressurized > fuel rail, I've attached a plot of data collected from local > samples of 100 LL avgas, 87 octane auto fuel with no ethanol, 91 > octane auto fuel with 10% ethanol, and tap water. The water was > measured just as a check on the method. > > The data would be considered more of a true vapor pressure rather > than a Reid vapor pressure due to the method used. > > The data indicates to me that if the fuel pressure in the fuel > rail is 35 psi as measured with a regular gauge referenced to the > atmosphere at sea level, the temperature of 100 LL or 91 octane > 10% ethanol in the rail would have to be in the neighborhood of > 240 deg F for it to form bubbles of vapor (boil). The sample of > 87 octane would require a temperature of about 215 deg F to form a > vapor phase. > > My take on this is it may be more productive to be concerned about > the fuel supply to the high pressure pumps rather than worrying > about "vapor lock" downstream of those pumps. This seems to be > the conclusion reached by the recent thread on this subject, > possibly now supported by actual data. Of course the data only > applies to the samples I obtained. > > The higher temperature tolerance of the auto fuel with ethanol > compared to the auto fuel without ethanol was surprising to me. > > But I only collect data --- it is up to an engineer to make sense > of it ;>) > > Steve Boese > RV6A, 1986 13B NA, RD1A, EC2 > > ------------------------------------------------------------------------ > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > --------------080909040705070800060003 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit I'd have to differ on a couple of points.

If you must pump to the sump, then the vent can't 'go anywhere' unless you're willing to risk pumping fuel overboard.

On a typical RV, it would require removing several dozen screws, the vent line and fuel line, and then removing the tank before I could remove the 6 or 8 screws that hold on the access plate to the tank. So, there is a bit of a maintenance issue for us. If not for that, I'd use in-tank pumps. For my application, the external sump would add more weight/complexity.

To the implication that we would choose maintenance ease vs life risk: you have to be honest; *every* decision makes that choice. The safest G/a factory plane in the world uses bolt-on wings instead of a one-piece wing; a one-piece would be both lighter and safer.

Charlie



On 09/02/2011 01:04 PM, Al Wick wrote:
What fine work Steve. I love it when someone converts theory to facts. You measured that all at sea level. Now just subtract 5.35 from all your pressure numbers if you fly at 12k ft. You've now measured all of the variables that affect vapor lock. Only remaining item is measuring pressure at your pump inlet. You then can predict exactly how safe your plane is without ever flying! How cool is that?
 
I use a submerged fuel pump for added safety. Two actually. Easy to maintain, just remove the 6 screws that hold the pumps in place. So there is zero significance to the argument of maintenance. Can't imagine how anyone could claim maintenance is more important than life risk anyway. I return all fuel to my 3 gallon sump. Vent can go anywhere, you don't have to tie vent into main fuel vents.
 
Once again, nice work Steve.
 
-al wick
 
 
----- Original Message -----
Sent: Friday, September 02, 2011 12:04 AM
Subject: [FlyRotary] vapor lock

For those concerned about the formation of vapor in a pressurized fuel rail, I've attached a plot of data collected from local samples of 100 LL avgas, 87 octane auto fuel with no ethanol, 91 octane auto fuel with 10% ethanol, and tap water.  The water was measured just as a check on the method.

 

The data would be considered more of a true vapor pressure rather than a Reid vapor pressure due to the method used.

 

The data indicates to me that if the fuel pressure in the fuel rail is 35 psi as measured with a regular gauge referenced to the atmosphere at sea level, the temperature of 100 LL or 91 octane 10% ethanol in the rail would have to be in the neighborhood of 240 deg F for it to form bubbles of vapor (boil).  The sample of 87 octane would require a temperature of about 215 deg F to form a vapor phase.

 

My take on this is it may be more productive to be concerned about the fuel supply to the high pressure pumps rather than worrying about "vapor lock" downstream of those pumps.  This seems to be the conclusion reached by the recent thread on this subject, possibly now supported by actual data.  Of course the data only applies to the samples I obtained.

 

The higher temperature tolerance of the auto fuel with ethanol compared to the auto fuel without ethanol was surprising to me.

 

But I only collect data --- it is up to an engineer to make sense of it ;>)

 

Steve Boese
RV6A, 1986 13B NA, RD1A, EC2

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Homepage:  http://www.flyrotary.com/
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