System and method for measuring the filling level of a fluid container by means of acoustic waves

An acoustic wave measurement system for measuring the fill level of a tank, said tank storing a first single-phase fluid having first physical properties and a second single-phase fluid having second physical properties, said first physical properties comprising a first density ρ1 and said second physical properties comprising a second density ρ2 strictly lower than the first density ρ1 so that the single-phase fluids are vertically superimposed in the tank, the first single-phase fluid being located in the lower part of the tank, the second single-phase fluid being located in the upper part of the tank, said first single-phase fluid and said second single-phase fluid being separated by a substantially horizontal interface, said tank comprising an envelope extending longitudinally along an axis X10, the envelope comprising an inner face in contact with the single-phase fluids and an outer face, the envelope comprising a cylindrical median portion, wherein the measurement system comprises:

• at least three transducers configured to be positioned at different vertical heights on the outer face of the cylindrical portion of the envelope,
• each transducer being configured, on the one hand, to emit, upon receiving a first electric signal, an incident acoustic wave to the outer face of a wall of the envelope and, on the other hand, to emit a second electric signal, upon receiving a reflected acoustic wave, corresponding to the reflection of the incident acoustic wave on the inner face of said wall, the reflected acoustic wave having passed only through the wall of the envelope, the second electric signal being a function of the difference in acoustic energy between the incident acoustic wave and the reflected acoustic wave,
• at least one calculation member configured to determine, from the electric signals and physical properties of the single-phase fluids, the presence of the first single-phase fluid at each vertical height of the transducers and to deduce the fill level therefrom.