---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Thu 03/02/06: 9 ---------------------------------------------------------- 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 _____________________________________ Time: 05:31:13 AM PST US From: Jan de Jong Subject: Re: Europa-List: 914 fuel pumps --> Europa-List message posted by: Jan de Jong 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 _____________________________________ Time: 05:44:06 AM PST US From: "chris robinson" Subject: Europa-List: mailing list --> Europa-List message posted by: "chris robinson" 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 _____________________________________ Time: 07:56:18 AM PST US From: Richard Holder Subject: Europa-List: 914 fuel pumps --> Europa-List message posted by: Richard Holder 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 _____________________________________ Time: 12:18:00 PM PST US Subject: Europa-List: Wrap 914 exhaust? From: --> Europa-List message posted by: Is anyone wrapping the exhaust of 914? Comments? Thx. Ron Parigoris ________________________________ Message 5 _____________________________________ Time: 01:03:28 PM PST US From: Gilles Thesee Subject: Re: Europa-List: Wrap 914 exhaust? --> Europa-List message posted by: Gilles Thesee rparigor@suffolk.lib.ny.us a crit : >--> Europa-List message posted by: > >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 _____________________________________ Time: 01:03:28 PM PST US From: Paddy Clarke Subject: Europa-List: DOTH Sandtoft Sat. 4th --> Europa-List message posted by: Paddy Clarke 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 _____________________________________ Time: 02:10:03 PM PST US From: "R.C.Harrison" Subject: RE: Europa-List: DOTH Sandtoft Sat. 4th --> Europa-List message posted by: "R.C.Harrison" 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 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 _____________________________________ Time: 04:14:00 PM PST US From: SPurpura@aol.com Subject: Re: Europa-List: 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 _____________________________________ Time: 05:37:09 PM PST US From: Bbryanallsop@wmconnect.com Subject: Europa-List: 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