I hope there is someone out there who can tell me if I have what I need.

I did some rudimentary pressure and flow tests on this home made waterpump
that is designed to bolt directly on the e-shaft.

Zero flow pressure, starting at 1065 rpm was 2.5 psi, increasing as rpm
squared up to 80 psi at 6000 rpm.

Flow rate with a 2.25 foot lift required on the intake side, zero back
pressure, starting at 1065 rpm was 15 gpm, increasing linearly up to 40 gpm
at 2520 rpm.  Almost no increase in flow rate above that up to 6000 rpm.
However, at 3840 rpm, restricting the output until there was a 20 psi back
pressure did not change the flow rate.

Previous testing with only a 8 inch lift at 2600 rpm resulted in 50 gpm.

It looks to me like, with that much lift, I am intake limited.  On an

engine,

there will be no lift, and the system will be under pressure so I will give
it a try.

I need expert guidance here--what am I overlooking?

Thanks

Bob Darrah

What do you think Jeff?

Paul Lamar

Jeff Spitzer wrote:

This looks like a classic case of inlet cavitation.  The results indicate
that the flow is cavitating when 40 GPM is attained with 2' lift and 50 GPM
with 8" lift.  This is a pretty steep curve where reducing the lift a
little less than 1 psi gave an additional 25% flow.  I don't think anything
is mysterious here.  I think the pump could be improved.  I'm a little
worried about the statement that "the system will be under pressure"
implying that this will help.  It would help if the coolant were not also
hotter.  Maybe the pressure increase is greater than the lowering of the
vapor pressure due to temp and maybe not.  I would not choose to run a
system where slightly higher temps or lower system pressures would push me
off such a steep cliff of dropping flow rate leading to even higher temps
and even less flow etc, etc until boil over.

Jeff Spitzer

 
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