Numerical Modeling of Wear Damage in Seals of a Wave Energy Converter with Hydraulic Power Take-Off under Random Loads

Abstract

Understanding and managing the safety and reliability issues of ocean energy converters is a key factor in the development of viable technologies. The present article deals with wear in the high-pressure hydraulic power take-off machinery in a heaving-buoy wave energy converter. In this study, an abrasive wear model for such machinery is developed for the steady-state operation by considering the effects of sealed pressure, relative velocity, material properties, time-varying environmental conditions, and lubrication, with a focus on the piston ring. In particular, the dependence of the wear damage on the sea state condition is investigated. The dynamic parameter named instantaneous wear work rate (Load × Velocity) is numerically calculated in the time domain. An estimate of the average wear work rate in each sea state is computed on the basis of a wave scatter table (significant wave heights versus peak period). Long-term wear damage can then be accounted for by summing up the short-term wear damage multiplied with the occurrence probability of each sea state. Finally, the relative contribution of wear damage from different sea states is obtained.

KEY WORDS:

• Abrasive Wear
• Piston Rings
• Dynamic Modeling
• Wave Energy Converter
• Hydraulic Power Take-Off
• Irregular Wave
• Wear Work Rate
• Short-Term Damage
• Long-Term Damage

ACKNOWLEDGMENTS

The authors acknowledge the support of the Research Council of Norway through the Centre for Ships and Ocean Structures at the Norwegian University of Science and Technology in Trondheim, Norway.

Review led by Jack Poley