High accuracy volume flow rate measurement using vortex counting

Abstract

A prototype device for measuring the volumetric flow-rate by counting vortices has been designed and realized. It consists of a square-section pipe in which a two-dimensional bluff body and a strain gauge force sensor are placed. These two elements are separated from each other, unlike the majority of vortex apparatus currently available. The principle is based on the generation of a separated wake behind the bluff body. The volumetric flow-rate measurement is done by counting vortices using a flat plate placed in the wake and attached to the beam sensor. By optimizing the geometrical arrangement, the search for a significant signal has shown that it was possible to get a quasi-periodic signal, within a good range of flow rates so that its performances are well deduced. The repeatability of the value of the volume of fluid passed for every vortex shed is tested for a given flow and then the accuracy of the measuring device is determined. This quantity is the constant of the device and is called the digital volume (V p ). It has the dimension of a volume and varies with the confinement of the flow and with the Reynolds number. Therefore, a dimensionless quantity is introduced, the reduced digital volume (V r ) that takes into account the average speed in the contracted section downstream of the bluff body. The reduced digital volume is found to be independent of the confinement in a significant range of Reynolds numbers, which gives the device a good accuracy.

A new approach to detection of vortices using ultrasound

“…Different factors effect to the measurement uncertainty: Shape and position of the bluff body, position of the sensor, roughness of the inner surface of the pipeline, electronic signal processing etc. [7,14,17,21,25,27].…”

“…The highest number of them is based on the detection of pressure fluctuations near the bluff body (traditional, or conventional vortex flow meter). These pressure variations caused by separation of vortices, can be detected by different sensors: differential pressure sensors, piezoelectric sensors, capacitive sensors, thermo-resistance sensors, strain gauge force sensors etc [5,9,17,19,20,22,26]. Different shapes of the bluff body with different characteristic dimension (size), and different blockage ratio (relation between size of the bluff body and pipe diameter d/D) are considered [26,[30][31][32].…”

Numerical investigation of flow rate measure using vortex counting at low Reynolds number

“…The details of geometry are reported in a paper flow measurement by vortex shedding flow meter [8]. It consists of a square-section pipe in which a two-dimensional trapezoidal cylinder is placed Fig.1-a.…”