Pressure pulsation and dynamic behavior analysis of an ultra-low head bidirectional rim-generator turbine with special emphasis on the gravity effect

Abstract

Tidal energy is an energy source that has the potential to be sustainable, and the development of this energy source relies on the use of rim-generators. In this study, the pressure pulsation characteristics and dynamic behavior of an ultra-low head bidirectional rim-generator turbine with a rated operating head to runner diameter ratio of 1:1 are analyzed using the acoustic fluid-structure interaction theory. The study places particular emphasis on the effect of gravity. Ten different operating conditions are simulated, and the impact of gravity and operating head on the turbine are thoroughly discussed. The findings indicate that gravity dominates the flow in the runner and has a significant impact on the pressure distribution. The operating head, on the other hand, has a limited impact on the frequency spectra of pressure pulsation and dynamic stress in the runner, but it does affect the dominant frequency of the pressure pulsation in the guide vanes and gap. The modal analysis combined with the dynamic stress analysis rules out the possibility of runner resonance. The methodology, which considers the effect of gravity on flow and structure, can enhance the understanding of the dynamic behavior of the rim-generator turbine, thus improve operation reliability.