Smart Fluidic Meters for Simultaneous Measurement of Fluid Flowrate, Reynolds Number, Density and Viscosity

Abstract

The potential of simple fluidic circuits, based on oscillators and laminar resistance, for the smart metering of fluids is examined. If fluid properties are unknown a single fluidic oscillator is only capable of volumetric metering if it has a constant Strouhal number, which is often not the case. With known viscosity, flowrate and density can be determined by measuring both frequency and the pressure drop across a meter with variable Strouhal number. A fluidic oscillator in parallel with a laminar resistance is known to have a significantly extended flow range, but it is shown to be unable to measure flowrate, density and viscosity. This is, however, achieved by placing a further oscillator in series, forming a two meter by-pass system. This is shown to have potential both as a Reynolds number meter, by measuring two frequencies, or with the additional measurement of a pressure drop, as a smart system simultaneously measuring flowrate, density and viscosity. Two target type fluidic oscillators and a laminar resistance are built and calibrated experimentally using air. These are then combined to form a two meter by-pass system which is again tested with air. The tests confirm the operation of the system both as a Re meter and for simultaneous measurement of flowrate and gas properties. The options in designing the system including component matching are briefly discussed and the potential of the technology for application at the micro-scale is highlighted.