Today's Message Index:
----------------------
1. 05:31 AM - Re: 914 fuel pumps (Jan de Jong)
2. 05:44 AM - mailing list (chris robinson)
3. 07:56 AM - 914 fuel pumps (Richard Holder)
4. 12:18 PM - Wrap 914 exhaust? ()
5. 01:03 PM - Re: Wrap 914 exhaust? (Gilles Thesee)
6. 01:03 PM - DOTH Sandtoft Sat. 4th (Paddy Clarke)
7. 02:10 PM - Re: DOTH Sandtoft Sat. 4th (R.C.Harrison)
8. 04:14 PM - Re: Wrap 914 exhaust? (SPurpura@aol.com)
9. 05:37 PM - Europa Club Events 2006 (Bbryanallsop@wmconnect.com)
Message 1
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Subject: | Re: 914 fuel pumps |
--> Europa-List message posted by: Jan de Jong <jan.de.jong@xs4all.nl>
For those not sick of the subject (as I am getting).
Series vs. parallel - a public effort at some quantification from Rotax
published data.
Page 50 of the 914 Installation Manual has a pressure-flow graph showing
a maximum flow rate of 120 l/h at zero pressure and a maximum pressure
of 1850 hPa at zero flow rate. The graph seems to be a redrawn copy of
the one in the Pierburg brochure for the E1F, pn 7.21440.78.0, with
stated rating of 95 l/h at 1 bar - thank you Gilles.
Whether the pump acts more like a "pressure source" (pressure little
dependent on flow) or "flow source" (flow little dependent on pressure)
depends on where it operates on this line. At low flow rates it acts
more like a "pressure source" at high flow rates more like a "flow source".
Estimating the maximum pressure that a pump must at least supply.
Page 9-5 of the 914 Operating Manual shows that sealevel airbox pressure
at 100% throttle is 1220 hPa, the boost above ISA pressure being 207 hPa.
Pages 10-1 and 10-2 of the 914 Operating Manual show that sealevel
manifold pressure at 100% throttle (some 40 hPa lower than the airbox
pressure) is maintained to an altitude of 4500 m where ISA pressure is
577 hPa, requiring an additional boost pressure of 477 hPa. Maximum
boost over ambient is then 207 + 477 = 684 hPa.
Page 9-5 of the 914 Operating Manual shows that sealevel airbox pressure
at 115% throttle is 1370 hPa, the boost above ISA pressure being 357 hPa.
Pages 10-1 and 10-2 of the 914 Operating Manual show that sealevel
manifold pressure at 115% throttle (some 50 hPa lower than the airbox
pressure) is maintained to an altitude of 2450 m where ISA pressure is
752 hPa, requiring an additional boost pressure of 261 hPa. Maximum
boost over ambient is 357 + 261 = 618 hPa.
It seems safe to assume a maximum boost pressure - airbox over ambient -
of 700 hPa.
Page 49 of the 914 Installation Manual specifies a maximum pressure loss
in the return line of 100 hPa.
Maybe the maximum pressure loss in the forward line (filters etc.) may
be put at 150 hPa.
Page 10-2 of the 914 Operating Manual states that fuel pressure should
be at least 150 hPa above airbox pressure (Installation Manual says
manifold pressure).
Not taken into account: hydrostatic difference and any ram tank pressure.
Pressure regulator assumptions:
It operates by adjusting its input pressure.
It adjust a restriction in the return line to set an operating point
(pressure, flow) for the pump(s).
The pressure drop from input to carburettor output lines is negligeable.
The maximum pressure a pump must be able to at least supply is then 700
+ 100 + 150 + 150 = 1100 hPa.
According to the pressure-flow graph it does this when regulated to a
flow rate of 90 l/h.
Even at the maximum fuel consumption of 36 l/h that makes for a 60%
return to the tank.
This is very close to the official Pierburg rating of 95 l/h at 1000 hPa.
The estimated pressure being the maximum required it follows that a
single pump operates to the left of the 90 l/h and 1100 hPa coordinate,
where it works much as a "flow source": flow little dependent on pressure.
It is interesting to see in the pressure-flow graph of page 50 of the
914 Installation Manual what are the effects of putting two pumps in
series and in parallel.
Series:
Say the one-pump operating point is 1100 hPa / 90 l/h.
Now double the graph in the horizontal direction - each flow rate
generating twice the pressure.
If the pressure regulator does nothing the line through the origin and
1100 hPa / 90 l/h finds a new combined operating point at about 1320 hPa
/ 109 l/h.
As the regulator regulates back to see 1100 hPa the combined operating
point then becomes about 1100 hPa / 111 l/h.
Note: the selected rightmost operating point is the worst case for the
series connection.
Parallel:
Say the one-pump operating point is 1100 hPa / 90 l/h.
Now double the graph in the vertical direction - each pressure
generating twice the flow rate.
If the pressure regulator does nothing the line through the origin and
1100 hPa / 90 l/h finds a new combined operating point at about 1350 hPa
/ 116 l/h.
As the regulator regulates back to 1100 hPa the combined operating point
then becomes about 1100 hPa / 180 l/h.
Note: the selected rightmost operating point is the best case for the
parallel connection.
Conclusion:
In the parallel setup the second pump causes a large extra flow to get
rid of. Switching it on and off causes larger pressure and flow changes
for the regulator to cope with.
In the series setup the main effect is that the second pump relieves the
first from half its load. Switching causes smaller changes.
The series setup actually saves some electric power too. Because the 2
pumps share the pressure between them, they each operate at 550 hPa in
the example (if identical - in practice one will do most of the work,
the other only a little). In the parallel case each pump supplies the
full 1100 hPa.
The graph on page 82 in the 914 Installation Manual (likely also redrawn
from the Pierburg text) suggests a (maximum) savings of about 1 A for
both pumps together.
Cheers,
Jan de Jong
Message 2
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--> Europa-List message posted by: "chris robinson" <crownwoodkitchens@hotmail.com>
Could you please delete this email address form your mailing list. I am
using this as the works email and need to keep it clear.
Can you please let me know if you can do this
Many Thanks
Chris
Message 3
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--> Europa-List message posted by: Richard Holder <rholder@avnet.co.uk>
Jan de Jong wrote:
a whole bunch of stuff about series and parallel pumps.
But everyone is getting confused here. The parallel/series
discussion is not about flow or pressure, it is about
redundancy.
Thus the MOST important thing is that in the event of any
one problem, fuel can still flow to the engine. Both pumps
are only used together for take-off and landing, so for
most of the flight it is the single pump that does all the
work.
The problems can be a pump failure, a pump blockage, a
non-return valve blockage, a pipe blockage, a t-piece
blockage, a filter blockage (and others !). The set-up
should be such that any one "problem' as defined above can
be avoided (bypassed) by the use of the different options.
There is no guarantee that you will get to your
destination if (say) a in-line filter blocks up, but you
will have power.
Ideally any by-product of the initial problem (debris ...)
will not affect the alternative fuel supply.
Now the 914 seems to use two pumps with impellers of a
type that cannot have fuel sucked or blown through them
unless the pump is running. This is not true of the
mechanical pump or the electric pump used on a 912/S.
So (for the 914) a parallel system does not need
non-return valves except as a belt, braces and piece of
string option; as one pump running cannot recirculate
through the other.
On the other hand a series (for the pumps) must have a
pipe bypassing each pump in case it fails, and these two
pipes need a non-return valve in them.
So parallel is :
Tank--ILF--- -- pump --
selector---tpc tpc --- engine
Tank--ILF--- -- pump --
So series is :
T---ILF--- -- NRV -- -- NRV --
sel -- tpc tpc ---tpc tpc
-- eng
T---ILF--- -- pump -- -- pump -
But that diagram may not come out how I want ! In all
cases Y-pieces are better than T-pieces.
Parallel has less components, and I am a great believer in
the KISS principle. Even with the NRVs the parallel has
less components.
These components are very reliable (they are approved for
aviation) so it is really best not to go too far into the
what-if solutions as most of the compound problems will
never occur. Or might even occur because of additional
complexity.
KISS :-)
Richard ducking head beneath parapet !
Message 4
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Subject: | Wrap 914 exhaust? |
--> Europa-List message posted by: <rparigor@suffolk.lib.ny.us>
Is anyone wrapping the exhaust of 914?
Comments?
Thx.
Ron Parigoris
Message 5
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Subject: | Re: Wrap 914 exhaust? |
--> Europa-List message posted by: Gilles Thesee <Gilles.Thesee@ac-grenoble.fr>
rparigor@suffolk.lib.ny.us a crit :
>--> Europa-List message posted by: <rparigor@suffolk.lib.ny.us>
>
>Is anyone wrapping the exhaust of 914?
>
>Comments?
>
>
>
Hi Ron and all,
No direct experience, we only wrapped the turbo, to prevent radiating
too much heat inside the engine compartment.
Our kit manufacturer, Dyn Aero, once wrapped the 912 exhausts. They
experienced numerous pipe failures due to corrosion, so they
discontinued wrapping.
Considering that the 914 exhaust generates much more heat than normally
aspirated engines, we had the pipes ceramic coated (1200C grade). After
about 60 hours, the coating seems to hold, except some scaling on one or
two places.
FWIW
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
Message 6
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Subject: | DOTH Sandtoft Sat. 4th |
--> Europa-List message posted by: Paddy Clarke <paddyclarke@lineone.net>
Hi Folks,
Unless anyone has any better suggestions, how about a DOTH to
Sandtoft, 1200ish on Saturday?
Good food - voucher in Flyer.
Cheers, Paddy
Paddy Clarke
Europa XS - 404 G-KIMM
Message 7
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Subject: | DOTH Sandtoft Sat. 4th |
--> Europa-List message posted by: "R.C.Harrison" <ptag.dev@tiscali.co.uk>
Hi! Paddy
Would have met you there but have prospective house purchasers to tour
on Saturday and Sunday who don't respect my flying hours !!!!
Yes good food and the voucher makes it a good venue, It's local to Mike
Parkin he may meet you over land !
Make sure you have Doncaster/Sheffield Robin Hood details (was
Finningly RAF)otherwise you may infringe ! (their frequency is 126.22)
Regards
Bob H G-PTAG Europa MK1/Jabiru 3300
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Paddy
Clarke
Sent: 02 March 2006 21:00
Subject: Europa-List: DOTH Sandtoft Sat. 4th
--> Europa-List message posted by: Paddy Clarke
<paddyclarke@lineone.net>
Hi Folks,
Unless anyone has any better suggestions, how about a DOTH to
Sandtoft, 1200ish on Saturday?
Good food - voucher in Flyer.
Cheers, Paddy
Paddy Clarke
Europa XS - 404 G-KIMM
Message 8
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Subject: | Re: Wrap 914 exhaust? |
--> Europa-List message posted by: SPurpura@aol.com
I wrapped the front stbd pipe with 1/16" x 1" ceramic (tape,no adhesive)
where it passes near the oil lines only.
Message 9
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Subject: | Europa Club Events 2006 |
--> Europa-List message posted by: Bbryanallsop@wmconnect.com
Hi Folks,
I am compiling the program of events for this year. Many trips are already in
the diary, but there be something of which we have not been advised.
The British program is quite busy throughout the summer, with the exemption
of July, but we are not aware of much Europa Club activity elsewhere.
If you have anything in mind that you would like to be included, please
advise me as soon as possible.
Best regards.......Bryan Allsop
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