The data certainly suggests that there is something very amiss with your
test set up.
Why? How much data have you seen on CLOSED LOOP systems?
What goes out the pump goes in the pump. What goes around comes
around.
You do not seem to be developing anything like the pressure that one
would
expect for the rpm. Bill's data seems much more as one would expect.
Bill's data was taken by an OPEN LOOP SYSTEM!!!!!!!!!!!!!!!!!!!!!!
Any pressure on the outlet side is not reflected on the inlet side.
If you want to characterize the pump performance, the attached figure
shows about a minimum complexity setup. Also if you want to measure
the flow resistance of the block or radiator just put it in the circuit
in
place
of the valve. The reservoir will minimize heating with the increased
thermal
mass, and the system will be self priming .
Also the amount and pressure of water flow that we are dealing with is
not all that power hungry. the attached curve shows the theoretical
pumping power required at 60 gpm and 20 psid is less tha 3/4 hp
50 percent efficiency should be possible with a good pump
Vance
The figure you spoke of was missing. In its place was a prop thrust curve.
Here is the second jpg you sent which seems relevant.
Much of the heat is due to the inefficiency of the belt drive
I am sure. Side loads on bearings etc. etc.
If you are not doing anything on Wednesday come on over to the
hangar and witness the test.
Paul Lamar
Closed loop - open loop - the pump should put out useful pressure, and
you seemed to be developing only heat - which is one of the reasons why
that sort of loop
is not generally used for characterizing pump performance. The picture
loss\was
apparently" mouse miss" and hopefully this will be the right one/ Vance
The pump is also doing what it is supposed to be doing. 75 gallons
per minute is 75 gallons per minute!!!!!!!!!!!!!!
I am surprised at you Vance. I am sure you damn well know as well as I damn well know
that that tank will NOT provide any more pressure to the pump
or work any better than a 1.5 inch pipe of the same height
Open loop or closed loop. Did you get a C in hydraulics 101? :)
Looks impressive as hell to the naive laymen of course.
I'll tell you what. You build it and I will hook it to my system and test
it.
Paul Lamar
Paul,
I got an A in hydraulics. Your loop can generate useful data, but only if you have it pressurized so that you can accurately read the negative (with respect to system pressure) pump inlet pressure. Then the delta-P across the pump can be determined by the difference between the two readings.
You already did one test with the system pressurized, and the pump stagnant pressure (valve closed) was more-or-less in line with results I got, taking into account the different RPM.
A possible complication in comparing results may be incorporated in the tolerances on the water pump. You indicated in an earlier message that you were going for closer tolerances between the pump housing and the impeller, to increase performance. This may have an effect on the heating that you are experiencing. I really don't think it is side-load on the bearings or inefficiency in the belt drives. You are dumping energy into a very small system, with the pump acting as a dynamometer brake.
Bill Schertz
KIS Cruiser # 4045
I am sure you did Bill and you are not the object of my ire:)
Possibly.
But this prototype pump I would not ship to anybody.
A screwed up on the angle of the ramp so the impeller does not
match perfectly to the ramp. I intend machining some aluminum
slugs and thereby determine the exact proper angle by trial
and error. I have used clay in the pump and assembled it to
determine the exact clearance. It does not match by about
.040 on one end of the ramp and near zero on the other end
of the ramp. This is with no gasket. I used RTV to assemble
the pump for the test so I imagine that added a bit more
clearance.
Also there is a bit more clearance around the outside of the impeller.
I did not expect much from this particular pump and was blown away when
I started to see these high flow numbers. It could be the straight
shot into the inlet side of the pump that is causing it to work
so well.
The pump pulley actually get hotter than the pump body so I suspect
a lot of heat is coming from the bearings and the belts.
I now have the proper positive and negative pressure gage and
will rerun all the tests using that gage on the inlet. I will also run one or
two at a lower pump RPM so we can correlate better with your data.
I will also see if I can borrow a five HP mill and run some tests
at higher RPM's.
Paul Lamar
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