Re: [alfa] re fuel pump pressure

[bearbvd@xxxxxxxxxxxxxx (Greg Hermann)]

At 8:56 AM 10/26/03, giuliakev@domain.elided wrote:
>The only pumps that can add the incoming pressure would be non positive
>displacement pumps such as a centrifugal type.  Most fuel pumps are
>piston, or rotary gear/vane type.  If these have 2 psi at the intake, and
>are designed to deliver 2psi at the out let, they deliver 2 psi at the out
>let.  If they are centrifugal pumps the intake pressure will add with the
>outlet pressure.
>
>Kevin, Orem Utah

Absolutely incorrect, Kevin. Any pump, regardless of whether centrifugal or
positive displacement, will ADD its pressure to the inlet pressure. Only
way to avoid this would be if the pump incorporates a relief valve on the
discharge side which is referenced to atmospheric pressure rather than the
inlet pressure--which is VERY rare !!

A MUCH more important issue for ANY type of pump (fuel, coolant, oil, or
otherwise !!) is its NPSH (Net Positive Suction Head) requirement at any
give set of operating conditions !

Greg
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