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3 Polish Maritime Research

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Simulation and experimental study of hydraulic cylinder in oscillating float-type wave energy converter

100%

Lai W. , Li D. , Xie Y.

2020

tom nr 2

30--38

Hydraulic cylinders play a vital role in the energy output (PTO) system of an oscillating float-type wave Energy converter, whose function is to convert the mechanical energy captured by the float from the waves into hydraulic energy. The performance of the hydraulic cylinder determines the conversion efficiency of mechanical energy to hydraulic energy in the system; therefore, it is necessary to study the working mechanism of the hydraulic cylinder. This paper takes a self-developed oscillating float-type wave energy converter as the research object, and studies the working mechanism of its hydraulic cylinder, and uses the linear analysis method to derive the critical self-excited vibration curve of the hydraulic cylinder. In addition, the effects of the external load, hydraulic cylinder load mass, stroke length, spring stiffness and piston area on the performance of the hydraulic cylinder were studied by AMESim simulation software. According to the simulation results, a physical model of the hydraulic cylinder is established. Finally, the physical model is tested in a hydrodynamic pool. The test results show that the hydraulic cylinder can stably and efficiently convert mechanical energy into hydraulic energy even under small waves, thus verifying the rationality of the hydraulic cylinder design.

Experimental study of a puncture warning system for a jack-up offshore platform

88%

Liu Z. , Li X. , Song Y. , Xie Y. , Li D.

Polish Maritime Research

2024

tom nr 3

61--70

During the operation of jack-up offshore platforms, the complex and variable seabed geological conditions involved can lead to serious accidents, such as pile leg punctures and platform tilt. The aim of this study is to introduce an early warning method for punctures that ensures the operational safety of these platforms. To accomplish this, a real-time monitoring and controlling system is designed using a programmable logic controller that shares data from sensors measuring displacement, tilt, and pressure. In addition, an experimental device is constructed to simulate a jack-up offshore platform in order to assess the safety response of the control system. The working state of the platform under different working conditions (puncture of one independent pile, same side or diagonal piles, and three-pile linkage) is evaluated by analysing the structural motion response, including platform tilt and foundation pressure. The findings reveal that the system developed in this study accurately detects the tilt condition of the offshore platform, and can ensure the operational safety of jack-up offshore platforms.

Study on the dynamic response of deep-sea trawlers in sea trials

75%

Xu Q. , Xie Y. , Cai H. , Gong X. , Li D. , Wei W. , Jia P.

2023

tom nr 1

25--32

The increasing use of automation in fishing vessels has improved trawling efficiency while directly affecting the fishing capacity and cost of fishing vessels. Among the various influencing factors, warp tension and warp length can be varied to automatically balance the retraction and release of warp control. We combined the two parameters and independently designed and developed the key equipment for fishing vessels—the warp dynamometer and meter counter—and control software. The accuracy of the warp tension and length measurements was improved. The designed equipment was applied to sea trials under different working conditions, and the test data records were exported. Next, filtered time-domain graphs of the required parameters were plotted through complex Fourier transform, first-order lowpass filtering, and inverse Fourier transform. The results of data processing using various parameters were compared and analysed to determine the variation trends of the parameters and verify the effects of their balance control. The results indicated that using an automatic balance control system that combines warp tension and warp length can be effective for the fishing operation of offshore double-deck trawlers. In addition, first-order low-pass filtering can be used to filter complex warp tension data. This study also determined the relationship between warp tension and experimental parameters such as warp length and ship speed during the release of control. After the balance control of warp tension and warp length, the net mouth area increased by 30.7% and 36.5%, respectively, and the fishing efficiency of the vessel improved considerably.