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Hi Steve,
Good info; I appreciate it. If it will at least transfer faster than the fuel is burned, that might satisfy me. IIRC, the Facet pumps are designed for continuous duty, so that really shouldn't be too big a problem (there are H-series Lycs flying on RV's with just 2 Facets; no mechanical pump).
I've considered using a modified selector from a dual tank truck, but I've got 2 aux tanks in addition to the stock pair. My present plan is to use Van's 3-input selector to feed the transfer pump, & leave the main to feed the fuel pumps.
I've also thought about T'ing the transfer line into the main tank's supply line, but that's bad news when the Facet sucks the selected aux tank dry.
I believe that Todd Bartrim is just returning his fuel through a small heat exchanger to the inlet of the pump. That idea is tempting, too.
The really tempting idea is to simply regulate the pumps using a pressure sensor & a PWM power supply.....
On a different subject: have you considered using your programing skills to expand/modify your 'copilot' software a bit? I just saw a 7" screen 'netbook' running Windoze CE on ComputerGeeks for $80. A/D converter chips are really cheap now, & with your skillset, a PDA based engine monitor using off-the-shelf sensors should be easy. (hint hint) .
Charlie
On 6/4/2010 12:24 AM, Steven W. Boese wrote:
Charlie,
I initially set my fuel system up with a Facet low pressure transfer pump tee'd into the return line. This system required that the Facet pump run 50% of the time in order to keep the fuel tanks balanced. Others have done this successfully. I didn't like having to run the Facet pump this much and eventually went to a duplex valve of my own design and eliminated the transfer pump altogether. In my case, I had the return flow from the engine turning 90 degrees inside the tee where the transfer flow was added. Having the return flow straight through the tee and the transfer flow joining from the side may have worked better, but I didn't try this.
Steve Boese
RV6A, 1986 13B NA, RD1A, EC2
________________________________________
From: Rotary motors in aircraft [flyrotary@lancaironline.net] On Behalf Of Charlie England [ceengland@bellsouth.net]
Sent: Thursday, June 03, 2010 8:58 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: high/low pressure pumps question
Hi Ed, thanks for the info. Yours was actually the only photo I could
find during a quick search. I'm guessing that the regulator will be
bypassing 6 or 8 times the amount of fuel the engine consumes, so that
would seem to be at least twice the volume the Facet is capable of
pumping. If no one has plowed this ground yet, I suppose that some
experimentation is in order.
Charlie
On 6/3/2010 6:31 PM, Ed Anderson wrote:
Hi Charlie,
All my pumps, but the Facet, are on the forward face of the Firewall,
so can’t help you there.
Regarding “T” the Facet pump, Pressure will generally overwhelm
volume, you can think of a large mass of slow moving fluid as being
effectively a stationary pool of liquid (taking it to the extreme of
no motion), so a higher pressure fluid would simply squirt into the
larger volume liquid similar to as it if were a large tank). Yes, if
the larger mass were moving at a much higher velocity, it might in
effect offer a shearing force across the opening to the facet pump and
have detrimental effect (possibly) – but I doubt you are going to have
that kind of fluid velocity in your return line.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
<http://members.cox.net/rogersda/rotary/configs.htm>
http://www.rotaryaviation.com/Rotorhead%20Truth.htm
------------------------------------------------------------------------
*From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
*On Behalf Of *Charlie England
*Sent:* Thursday, June 03, 2010 5:22 PM
*To:* Rotary motors in aircraft
*Subject:* [FlyRotary] high/low pressure pumps question
A couple of questions:
Have any of you RV-x builders considered putting your pumps on the aft
side of the spar, to keep the cabin& engine compartment 'clean'? It
looks like it would be possible, by using the existing holes for wire
in the center section (RV-7). If not, are you just putting them under
the center cover between the seats& raising it up a bit?
Also, how about running the transfer (Facet) pump's output line T-d
into the main pump's return line? There should be minimal pressure,
but will the high pressure pump's much larger volume overwhelm the
modest Facet transfer pump? (Or, maybe venturi effect would eliminate
the need for a Facet....)
Thanks,
Charlie
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