Outflow control of a Francis turbine by UVP measurement
As part of the Smartgrid Interop project, the Cremhyg laboratory of Grenoble is interested in the flow around a torch in the outlet of a turbine for educational purposes, and if possible to detect the presence of a torch.
To do so, the Cremhyg possesses a TM4 CREMHYG setup and a UB-Lab X2 with 1MHz transducers.
TM4 CREMHYG allows the simulation of a waterfall into a hydroelectric production system using a Francis turbine, whose generator collects the energy.
The mean flow rate during the following measurements was about 80L/s, and the internal diameter of the tube was 232mm.
A portion of the tube, with a 232 mm internal diameter, made of PMMA material allows a visual observation of the torch. It is also there where the transducers were installed to do the acoustic measurements through the wall.
The torches can be cyclo-stationary, larger and induce the generation of microbubbles in suspension around the torch or finer and oscillating.
Here are two examples of evolution of the backscattered echo amplitude profile in one condition, and of evolution of the Doppler SNR in another condition. In both examples, we can see that the passage of the torch in the acoustic beam can be quite easily detected
And here is an example of the evolution of the radial velocity in front of the torch with a lot of bubbles in suspension:
It has been thus shown that the UVP (Ultrasonic Velocity Profiler) system UB-Lab X2 allows:
- the obtention of velocity profiles around the torch in conditions where there are microbubbles generated by the flow conditions. An artificial microbubbles injection in the circuit would allow measuring in the conditions where there is a lack of acoustic scatterers,
- the detection of the position of the torch and thus determine its oscillation period.