|
Message
Okay,
A year or so ago I posted a graph of measured 13-B
water pump performance. I am enclosing it again with this post. Several points
to be made:
1. The water pump is on the engine, so the pressure
indicated on the Y axis is the pressure that is left over to push the water
through the radiator cores.
2. The measurements were made with 3 different size
pulleys, to vary the water pump speed.
3. At no flow, the pressure on the Y axis is the
maximum pressure that the pump can supply. At zero pressure, max flow, all the
available head pressure from the pump is taken up by the pressure drop through
the block, and there is no more pressure to force water through the
radiator.
4. Looking at the charts, you can see that at a
flow of 20 gpm, the pressure drop across the core is 5 psi, at 33 gpm the drop
across the core is 8.5 psi, and at 44 gpm, the drop across the core is 19
psi.
At a later date, Barny located the full flow (no
pressure) and zero flow (max pressure) points for the Meziere pump. Dead
head pressure was 10 psi, and full flow was ~55gpm. These numbers did NOT have
the pressure drop across the core included. Tomorrow I will forward a
graph with this information overlayed on this chart.
Based on these TESTS, and the CLAIMED
performance (by the manufacturer) of the EWP, I calculate that you can get ~
20gpm max through an engine core combination. If you need more you will start to
have heat extraction problems.
Bill Schertz
KIS Cruiser # 4045
-- Original Message -----
Sent: Wednesday, October 20, 2004 1:45
PM
Subject: [FlyRotary] Re: nylon
EWP's
Subject:
[FlyRotary] nylon EWP's
I'd like
to hear some more comments about nylon vs. AL EWP's. should I be
satisfied with "well, Leon uses them" and ask no
more? the nylon pumps seem light enough, 2 lbs., that they could be
supported simply by their rubber hoses, which should make a good
vibration damper. (I don't really know who Leon is, although I get
the impression his word rates right up there with Tracy's) the nylon ones
only push 20 gpm, whereas the AL claim 37 gpm. I
have no idea what my 20B will require. I would be using 2 in
series.
Two in series may
not give much more flow than one; depending on the back pressure vs the
pressure at which those flows are based. If those pumps are rated flow at 0
pressure, it is likely that even the AL one is
marginal.
I’ve done the
math on the 20B. The flow requirements depends on the cooling system
design (obviously); but if you were to design for a sort of optimum system
for an aircraft, you’d like to have 20 – 30 F temp drop around the loop when
you are running about 85% power, say, 220 HP. So for a 50/50 EG/water
mix, and 25F delta T; that says 39.5 gpm. For pure water the number is
28.5 gpm
The only real
data I have on my pump is from the dyno runs. That showed 43 gpm at
5000; 48 at 6000. That is without a thermostat, and on a large
capacity system with presumably relatively low back pressure. 25-30%
less with a thermostat. Unfortunately, I don’t know what it is on the
airplane.
|