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Cavitating Venturis

Cavitating Venturis or Nozzles allow a liquid flowrate to be fixed or locked.  This flowrate is not dependent on downstream process conditions or fluctuations.  In function, this is similar to a Sonic Nozzle's velocity shockwave used with gases. A Sonic Nozzle's flowrate is adjusted with inlet pressure and is not sensitive to downstream conditions.  The Cavitating Venturi, however, uses the liquid's vapor pressure point to limit or lock the flow.  The throat of a Cavitating Venturi is sized such that the differential pressure generated from the inlet section to the throat reduces the liquid's absolute pressure to its vapor pressure point and it starts to vaporize or boil.  These vapor bubbles begin to physically block the throat passageway.  This prevents any additional increase in flowrate.  If the inlet pressure is increased, this also raises the throat pressure, taking the liquid at the throat out of its vapor pressure point range.  Additional flow may now pass through the Venturi which in-turn generates a higher differential pressure.  This decreases the throat pressure to the vapor pressure point again and a new higher fixed flowrate is found.