Experimental-theoretical investigations of the pressure pipeline at the Zagorsk water-storage power plant

Conclusions

• 1. Oscillations due to low-frequency sources of excitation beneath the impeller in the draft tube develop in long pipelines of water-storage power plants.

• 2. For the Zagorsk water-storage power plant with a long (790 m) and flexible pipeline, the natural frequency of the first type of the system's oscillation is many times lower than the predominant frequency of the lowest-frequency component of the spectrum of pressure fluctuations beneath the impeller (0.24–0.25)f_re. For a shorter and stiffer pipeline, the system would approach resonance.

• 3. The dynamic properties of the system depend on the opening of the guide apparatus: for small openings, the natural frequency approaches f₁=(C/4)L; with large openings, it approaches f₂=(C/2)L.

• 4. When the unit is operating in the stationary mode, the hydrodynamic loads on the pipe lining do not exceed 0.05 MPa; this corresponds to an additional stress of 0.07 MPa in the lining and vibrational displacements of 0.183 mm (when C=780 m/sec), i.e., not more than 0.06 of the radius of the pipeline; when C=965 m/sec, the vibrational displacements do not exceed 0.08 mm.

• 5. The loads on the pipeline supports do not exceed 0.36 tons on any one pile.