A critical flow venturi with either a movable centerbody or a fixed replaceable centerbody is provided for fluid flow measuring or fluid flow control by changing the critical flow rate area of the venturi. The critical flow venturi and its associated centerbody may be used with a wide variety of fluids including liquids, gases and mixtures thereof. A critical flow venturi with easily exchangeable centerbodies can conveniently provide a range of discrete high capacity calibration grade flow rates near atmospheric pressure. The discharge coefficient for each critical flow venturi may be accurately determined analytically to potentially eliminate the need for experimental calibrations. For pressurized applications, a remotely actuated centerbody may be preferred. The movable centerbody may be contoured to achieve unique flow characteristics, such as a linear change in critical flow rate in response to changes in the longitudinal position of the centerbody relative to the throat of the venturi. Alternatively, a movable centerbody may provide a uniform critical flow rate with changing fluid conditions such as temperature, pressure and composition upstream from the venturi.
Kendricks A. Behring, II