Li Yangjian

Bio: Li Yangjian is an academic researcher from Zhejiang University. The author has contributed to research in topics: Turbine & Maximum power principle. The author has an hindex of 3, co-authored 11 publications receiving 46 citations.

The Application of the Digital Controlled Hydraulic Cylinders Group in Pendulum Wave Energy

Abstract: Wave energy is one of the most important potential sustainable energy resources. To enhance the performance of the pendulum hydraulic wave energy converter (WEC) system in various wave conditions, this article proposes a digital controlled hydraulic cylinders group to replace the single traditional hydraulic cylinder in a hydraulic power take-off (PTO) system based on the concept of previous study. The cylinders group, whose structure is designed with high extendability, consists of several pairs of subsidiary cylinders. The extraction energy maximizing for pendulum WEC is theoretically analyzed in the frequency domain based on a linear wave assumption, which indicates demand for damping regulation. The proposed cylinders group is able to provide variable damping for the PTO system by changing its working area. So as to demonstrate the better performance of the proposed cylinders group compared with a single traditional hydraulic cylinder, a simulation in AMESim software and a fundamental semiphysical test have been carried out. Both results illustrated that the WEC was endowed with high performance by using cylinders group in various wave conditions. In addition, a transmission efficiency test indicated that the application of the cylinders group did not cause much more extra energy loss during the transmission process compared with the single traditional cylinder. The further study of cylinders group with more subsidiary cylinders and the control strategy remains to be conducted.

Improved Blade Design for Tidal Current Turbines

Abstract: The efficiency and reliability of blades are key indicators for a tidal current turbine (TCT). A traditional blade design is often an empirical design on hydrodynamics and structure, sequentially. A hydrofoil with a low lift–drag ratio is considered when the structural strength cannot satisfy requirements. However, efficiency is then sacrificed. A redundant design is generally adopted to protect from load uncertainty, but this increases blade weight and cost. In this paper, we present an improved blade design method to enhance the blade reliability of TCTs with relatively high efficiency for energy generation. An equivalent S–N curve model describing the relationship between axial load and cycle times and a simplified load spectrum including load caused by shear flow and turbulence are proposed for the first time for convenient lifetime estimation. A multi-objective genetic algorithm is used to optimize the chord length, twist angle, and thickness of the blade for the best match between lifetime and efficiency. This blade design method was conducted on a 4.4 m length blade of a 120 kW TCT. Comparisons between the original design and optimal designs indicate that the comprehensive performance in terms of the hydrodynamics, structure, and lifetime of the blade presented significant improvements with a small, acceptable efficiency loss. The results also provide more alternative blade solutions for developers as a reference.

Developement and verification of a performance based optimal design software for wind turbine blades

Abstract: In this research, we developed software for designing the optimum shape of multi-MW wind turbine blades and analyzing the performance, and it features aerodynamic shape design, performance analysis, pitch–torque analysis and shape optimization for wind turbine blades. In order to verify the accuracy of the performance analysis results of the software developed in this research, we chose the 5 MW blade, designed by NREL, as the comparison model and compared with the analysis results of well known commercial software (GH-Bladed). The calculated performance analysis results of GH-Bladed and our software were consistent in all values of CP in all λ ranges. Also, to confirm applicability of the optimum design module, the optimum design of the new 5 MW blade was performed using the initial design data of the comparison model and found that solidity was smaller in our design even though it produced the same output and efficiency. Through optimization of blade design, efficiency increased by 1% while the thrust coefficient decreased by 7.5%.