----- Original Message -----

From: Al Gietzen

To: Rotary motors in aircraft

Sent: Thursday, October 21, 2004 9:56 AM

Subject: [FlyRotary] Core pressure drop

Subject: [FlyRotary] Re: nylon EWP's

 

The curves that start at zero and rise as the square of the flow with data points are measured flow rates through an 'individual' radiator core [measured both cores, they behaved the same]. I will be running the cores in parallel, so the curve near the 'real rad test' is a calculated curve that is the sum of two individual cores.

 

I then plumbed the two evaporator cores into the flow loop, and got a single point with pressure drop and flow rate for the two in parallel. Here is the plumbing setup. You have to look hard to see that they really are plumbed in parallel, but they are.

 

Bill Schertz

Bill;

What’s the i.d. on the aluminum tube and fittings going in and out of the core, and the connecting line?  It looks like the flow velocities there would be quite high when you get to about 10 or more gpm per core.  What did you estimate for that contribution to the pressure drop.

 

Al

 

 

 

KIS Cruiser # 4045

----- Original Message -----

From: Al Gietzen

To: Rotary motors in aircraft

Sent: Wednesday, October 20, 2004 11:35 PM

Subject: [FlyRotary] Re: nylon EWP's

 

Bill;

 

Good stuff.

The flow curve shown for my dyno run,  http://members.cox.net/alg3/Dynamometer%20test%20report.htm

 is pumping through the engine and through the large radiator of the facility.  I think the pump on my 20B is geared about 1:1 with the e-shaft.  For the same RPMs, my data correlate reasonably well with yours at 0 backpressure across the radiator.

 

Are the core drops for evaporator cores?  What is the “Real rad test” data point on the chart?  Ron Davis Racing gave me a pressure drop of 2.25 psi at 20 gpm for the rad I got from them.  Griffin did not provide any pressure drop data on the rad they made for me that goes in the wing root, but based on the configuration I’m sure it is higher.  I’m guessing that my two rads in parallel will get me out close to 40 gpm at 5600 rpm, which is pretty much on my design point.

 

Now if I just knew what the actual air-side flow was going to be . . .

 

Al

 

Subject: [FlyRotary] Re: nylon EWP's

 

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 -----

From: Al Gietzen

To: Rotary motors in aircraft

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.