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. 2018 Jan 10;18(1):174.
doi: 10.3390/s18010174.

Feasibility of Detecting Natural Frequencies of Hydraulic Turbines While in Operation, Using Strain Gauges

David Valentín  1 , Alexandre Presas  2 , Matias Bossio  3 , Mònica Egusquiza  4 , Eduard Egusquiza  5 , Carme Valero  6
Affiliations

Feasibility of Detecting Natural Frequencies of Hydraulic Turbines While in Operation, Using Strain Gauges

David Valentín et al. Sensors (Basel). .

Abstract

Nowadays, hydropower plays an essential role in the energy market. Due to their fast response and regulation capacity, hydraulic turbines operate at off-design conditions with a high number of starts and stops. In this situation, dynamic loads and stresses over the structure are high, registering some failures over time, especially in the runner. Therefore, it is important to know the dynamic response of the runner while in operation, i.e., the natural frequencies, damping and mode shapes, in order to avoid resonance and fatigue problems. Detecting the natural frequencies of hydraulic turbine runners while in operation is challenging, because they are inaccessible structures strongly affected by their confinement in water. Strain gauges are used to measure the stresses of hydraulic turbine runners in operation during commissioning. However, in this paper, the feasibility of using them to detect the natural frequencies of hydraulic turbines runners while in operation is studied. For this purpose, a large Francis turbine runner (444 MW) was instrumented with several strain gauges at different positions. First, a complete experimental strain modal testing (SMT) of the runner in air was performed using the strain gauges and accelerometers. Then, the natural frequencies of the runner were estimated during operation by means of analyzing accurately transient events or rough operating conditions.

Keywords: hydraulic turbine; modal analysis; natural frequencies; strain gauges.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Pictures of the Francis turbine runner studied. (a) Picture during the installation of the strain gauges in the runner; (b) detail of the runner blades.
Figure 2
Figure 2
Detail of the strain gauges installed in the runner. (a) Strain gauges in the pressure side and band side; (b) strain gauges in the suction side and crown side; (c,d) detail of the epoxy resin covering the strain gauges.
Figure 3
Figure 3
Detail of the telemetry system installed in the rotating train of the Francis turbine. (a) Sketch of the telemetry system; (b) picture of the telemetry system installed in the hub of the runner; (c) rotating antenna at the tip of the shaft.
Figure 4
Figure 4
Detail of sensors available during the experimental modal analysis (EMA). (a) Sketch of the location of the accelerometers; (b) picture of the accelerometer located in the band outlet.
Figure 5
Figure 5
Time signal of the wicket gate opening, rotating speed and a strain gauge of the runner during the start-up of the machine.
Figure 6
Figure 6
Comparison of an averaged-spectrum analysis (left) and a joint time–frequency analysis using wavelets (right) of a strain gauge signal during deep part load (DPL) operation.
Figure 7
Figure 7
Frequency response function (FRF) in different points of the runner (0–250 Hz), as well as the operational deflection shape (ODS) of every runner mode shape associated with every natural frequency. Maximum displacement is colored red, and minimum displacement is colored blue. Videos of the mode shapes are found the Supplementary Materials section (S1 to S12).
Figure 8
Figure 8
FRFs (only the real part) of different strain gauges with the hammer as a reference (impact in blade 7).
Figure 9
Figure 9
Joint time–frequency plot of a strain-gauge signal (crown side, pressure side, blade 7) during the initial hit.
Figure 10
Figure 10
Joint time–frequency plot of a strain gauge signal (crown side, pressure side, blade 7) during DPL (18% of rated power).
Figure 11
Figure 11
Averaged-spectrum analysis of a strain-gauge signal (crown side, pressure side, blade 7) during (a) DPL (18% of rated power); and (b) best efficiency point (BEP) (90% of rated power).
Figure 12
Figure 12
Averaged-spectrum analysis of a different strain gauges during DPL (18% of rated power).
Figure 13
Figure 13
Joint time–frequency plot of a strain-gauge signal (crown side, pressure side, blade 7) during overload (OL) condition (107% of rated power).
See this image and copyright information in PMC

References

    1. International Energy Agency (IEA) Key World Energy Trends. Excerpt from: World Energy Balances. IEA; Paris, France: 2016.
    1. Huang X., Chamberland-Lauzon J., Oram C., Klopfer A., Ruchonnet N. Fatigue Analyses of the Prototype Francis Runners Based on Site Measurements and Simulations. IOP Conf. Ser.: Earth Environ. Sci. 2014;22:012014. doi: 10.1088/1755-1315/22/1/012014. - DOI
    1. Ohashi H. Case Study of Pump Failure Due to Rotor-Stator Interaction. Int. J. Rotat. Mach. 1994;1:53–60. doi: 10.1155/S1023621X94000059. - DOI
    1. Egusquiza E., Valero C., Huang X., Jou E., Guardo A., Rodriguez C. Failure investigation of a large pump-turbine runner. Eng. Fail. Anal. 2012;23:27–34. doi: 10.1016/j.engfailanal.2012.01.012. - DOI
    1. Trivedi C. A review on fluid structure interaction in hydraulic turbines: A focus on hydrodynamic damping. Eng. Fail. Anal. 2017;77:1–22. doi: 10.1016/j.engfailanal.2017.02.021. - DOI

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