Real-time staggered PRF for in-line industrial fluids characterization

The rheology of a fluid flowing in an industrial pipe can be assessed by combining the pressure drop and the fluid velocity profile, which can be obtained non-invasively through a Pulsed Wave Doppler (PWD) ultrasound investigation. In PWD, the maximum detectable velocity is related to the Pulse Repetition Frequency (PRF), which, in turn, is limited by the maximum investigation depth. Unfortunately, high flow-rates flowing in large industrial pipes produce Doppler frequencies that easily exceed the Nyquist limit, thus resulting in aliased, corrupted measurements. Staggered PRF is a known technique that allows an extension of the Nyquist limit. The de-aliased velocity is recovered by combining the aliased velocities measured from different PRFs, generated with specific ratios. In this work, we extend the capabilities of an embedded ultrasound system for rheological characterization of industrial fluids (doi: 10.1109/ULTSYM.2015.0273) by implementing, in real-time, the staggered PRF method.