Paul wrote:

Tracy Crook wrote:

Paul Lamar wrote:

A turbo compressor map is a close analogy to a centrifugal pump
and restricting the flow causes cavitation at lower RPM. This is easy
to prove. Drive the pump from your variable speed lathe with a ball
valve on the output. PL

Tracy Crook wrote:

Lets define cavitation.  Cavitation in a water pump is when the water
flashes to steam on the low pressure surface of the impeller.  In no way can
this be compared to a turbo compressor because air don't boil :-)  Our
friends at Racing Beat have already established that the threshold of
cavitation for the stock Mazda pump is about 7000 rpm.  That would take a
pretty fast lathe.

Not if you chucked a shaft with a  bigger V belt pulley in there :-).

I have approximated the lathe experiment by cranking up
the pressure on the limit switch of my water well pump (I live in the
sticks) to keep it running when the pressure is at maximum and the flow is
zero. It doesn't cavitate.   Most people who have lived around these pumps
are familiar with the churning sound they make when cavitating.  It WILL
cavitate when the pressure is very low (i.e., the storage tank is empty) and
will continue to do so until it gets a good head of pressure (more
restriction on the outlet).

Tracy Crook
rws@altavista.net
www.rotaryaviation.com

So when there is no flow and the tank is empty it does not make
the same noise? So I guess it is stalled at that point.

This too is an open loop system.

Paul Lamar

 
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