Guy,
You are part right, but they are not air bubbles, they are steam bubbles.
At the speed of the eye of the impellor increases, the pressure decreases
below the saturation point. The fluid flashes to steam in the eye, the pump
losses suction. The entire cycle of cavitation happens very fast. In an
instant the steam bubble moves out of the eye, the pressure is greater, it
condenses to fluid again (this condensing action is what is heard when you
can hear a pump cavitate), the pump regains flow, the pressure in the eye
decreases and the entire cycle is started again.
----- Original Message -----
From "Guy Weller" <guy at weller-lakes.freeserve.co.uk>
To: <spridgets@autox.team.net>
Sent: Sunday, September 30, 2001 8:51 AM
Subject: Re: Lets get this straight - Re: "Oil Pressure" & "old" overheating
problem
> Daniel,
> I am sure you are right.
>
> Someone mentioned "Cavatation" (sp?) which is the effect caused when
> the quantity of air bubbles generated by the impeller running at high
> speed begin to reduce its efficiency in pumping water. There is an
> optimum speed for the water pump to work at its best. Spin too fast
> and it pumps less water!
>
> Early A series probably only rarely ran at over 3500rpm. With
> development to higher rpm the larger pully was needed to keep the pump
> running at the optimum speed during normal use.
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