A Novel Approach to the Improvement of the Hydropower Plants Protective Measures—Modelling and Numerical Analyses of the Semi-Pneumatic Surge Tank

Abstract

Adopting adequate operational and safety measures is a significant part of the investigation of transient processes of hydropower plants (HPPs), both throughout the design stage of prospective plants and throughout the planning stage of the HPPs envisaged for refurbishment/uprating. One of the surge tank (ST) types, insufficiently researched so far, with a potential positive techno-economical influence, is the semi-pneumatic surge tank (SPST). Since the detailed analyses of SPST have never been performed or published before, the SPSTs have been examined here by presenting theoretical considerations, a newly developed mathematical model and comprehensive numerical simulations. The aim is to improve the performance of the open-air variations of STs. Multiple numerical simulations for a specific case-study HPP have been performed with the conclusions about the peculiarities and benefits of the SPST implementation. Firstly, numerical results for the existing as-built surge tank and corresponding alternative SPST have been compared, in order to verify the developed model. Variations of the main SPST constructive parameters have been analyzed, with the aim to determine the sensitivity of particular influences on transient processes versus its geometry alterations. The conducted analyses show that the SPST application brings HPP transient behaviour improvement compared to open-air ST. Dimensions of the new surge tank with specific aeration orifice could be smaller than the ones previously defined: both the diameter of the optimized upper and lower chamber and the core could be decreased by 20% and 12.5%, respectively.

Keywords

• hydraulic transients
• optimal operation
• semi-pneumatic surge tanks
• water-mass oscillations
• water hammer
• mathematical modelling