Very Accurate Analytical Calculation of the Discharge Coefficients of Critical Venturi Nozzles with Laminar Boundary Layer

摘要

The discharge coefficient of a critical Venturi nozzle was derived theoretically by taking the flow distribution in the core flow and the laminar boundary layer into consideration. The equation obtained was confirmed by measurements using a constant volume tank system and series connections of two critical nozzles. All nozzles were machined by super- accurate lathes; therefore, the relationship between the Reynolds number and the discharge coefficient was measured very accurately on similar nozzles. The coincidence of the theoretical and measured discharge coefficients is better than 0.04 at Reynolds numbers larger than the smallest extreme of the measurements, that is, 10~4. Some effort was excerted to decrease the difference.