Abstract
The assessment of the remaining useful life due to fatigue in Francis turbine runners implies complex measurements with strain gauges that have to be installed in a submerged and rotating structure, which is excited with high pressure pulsations and strong turbulent flows. Furthermore, the conditioning, storage and transmission of these signals to the stationary frame involves complicated technical solutions. In order to avoid such complex and expensive measurements, in this paper we explore the feasibility of obtaining the strain on the runner with stationary sensors, which can be easily installed and used for a continuous monitoring of the machine. Based on the experimental strain tests performed in a Francis turbine unit, strain on the runner blade is correlated with relevant indicators obtained with stationary sensors. The correlation within indicators is obtained considering linear regression models and improved with artificial intelligence techniques.
Highlights
Due to the massive entrance of Renewable Energies in the electrical grid, Hydraulic turbines have to work in off design conditions for a long period of time
The assessment of the remaining useful life due to fatigue in Francis turbine runners implies complex measurements with strain gauges that have to be installed in a submerged and rotating structure, which is excited with high pressure pulsations and strong turbulent flows
In order to avoid such complex and expensive measurements, in this paper we explore the feasibility of obtaining the strain on the runner with stationary sensors, which can be installed and used for a continuous monitoring of the machine
Summary
Due to the massive entrance of Renewable Energies in the electrical grid, Hydraulic turbines have to work in off design conditions for a long period of time. Recent cases in prototypes show the importance of considering and analyze the effects of fatigue in the lifetime of the unit (see for example [2,3]) This involves the determination of static and dynamic stresses on the critical points or stress hotspots of the runner for the different operating conditions[4]. Numerical simulation is a cheaper and faster option, experimental measurements may be the only reliable method for this purpose in the present Another approach could be to indirectly estimate strain & stresses on the runner based on other sensors on the stationary part or in the rotating shaft, as such sensors are much easier to install and to use.
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