Received-SPF: none
 receiver=logan.com; client-ip=67.15.10.31; envelope-from=bob@bob-white.com
Date: Mon, 14 Feb 2005 13:44:19 -0700
From: Bob White <bob@bob-white.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: More on Header Tanks,  Venting & Pressure Reg
 Position
Message-Id: <20050214134419.0d6949f8.bob@bob-white.com>
In-Reply-To: <list-728667@logan.com>
References: <list-728667@logan.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit


The volume of the gasoline in the vapor state will be much greater than 
the volume in the liquid state.  So if you shutdown the engine with 
nothing but liquid from the tank to the fuel rail, then convert only the 
fuel in the  fuel rail to vapor, it may push the liquid all the way back 
thru the fuel pump.  The regulator and fuel pump may act as one way 
valves which would help, but I'm not sure I would want to depend on it 
for an hour or two while the heat soak is taking place.  Or, assume the 
reverse flow doesn't occur.  Then the pressure in the fuel rail and the 
lines leading up to it will increase to the vapor pressure of the 
gasoline at whatever temperature it soaks to.

The further the regulator is from the fuel rail, the less well it will 
regulate.

Bob White

On Mon, 14 Feb 2005 14:15:32 -0500
Ernest Christley <echristl@cisco.com> wrote:

> 
> Problem: Hot start.  This would be the biggest problem.  Park the 
> plane 
> on a hot day, and residual heat in the engine will boil the fuel in 
> the 
> hose that is firewall forward, and push fluid back up through the 
> regulator.
> Solution:  Hit the cold start button on the EC2.  Mixture full rich. 
> If 
> it doesn't crank in a few turns, hit the cold start button on the EC2.
>  
> (What a hack, using the cold start button for a hot start)  The point 
> it 
> to clear out the hot, pressurized fumes.  If the engine will run on 
> the 
> fumes, then when it does catch, expect it to run way lean and rough 
> for 
> thirty seconds until the fumes get blown through.  There shouldn't be 
> much fumes there.  Only the line under the cowl will be heated.  As 
> the 
> fuel warms then boils, it will push the rest of the gas back toward 
> the 
> fuel regulator, locking the fumes in to the high part of the system 
> which just also happens to be the hottest (the Delta sits about 
> 9degree 
> nose high on the ground).  As the fumes expand and move down the fuel 
> line, it'll eventually reach the firewall penetration.  Notice the 
> dogleg in the fuel line on the passenger side of the firewall, from 
> low 
> to high.  The fumes will have to push the fuel down the dogleg and all
> 
> the way back to the fuel tank to cause the pumps to vapor lock, all 
> the 
> while being cooled by the aluminum line.  Since trapped gases are a 
> fairly decent insulator and any hot liquid gas would rise to the top, 
> I'd expect they'd only reach an inch or so behind the firewall.  A hot
> 
> start will only be a problem till it uses up the fumes that can occupy
> 
> the 2ft of 1/4" tube in front of the firewall.
> 
> 
> Ding! Ding!
> Class is now in session.  I have my pen and paper in hand, ready to 
> take 
> notes.
> 


-- 
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (soon)