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Aeroelastic deformation and load reduction of bending-torsion coupled wind turbine blades
Shaojun Du,Jingwei Zhou,Fengming Li 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.5
Wind turbine blades are adjusted in real-time according to the wind conditions and blade deformations to improve power generation efficiency. It is necessary to predict and reduce the aeroelastic deformations of wind turbine blades. In this paper, the equivalent model of the blade is established by the finite element method (FEM), and the aerodynamic load of the blade is evaluated based on the blade element momentum (BEM) theory. The aeroelastic coupling model is established, in which the bending-torsion coupling effect of the blade is taken into account. The steady and dynamic aeroelastic deformations are calculated. The influences of the blade section's shear centre position and the blade's sweepback design on the deformations are analyzed. The novel approaches of reducing the twist angle of the blade by changing the shear centre position and sweepback of the blade are presented and proven to be feasible.
Shaojun Bai,Chunlong Li,Xiangyu Fu,Jian Liu,Shuming Wen 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.61 No.-
The interaction between sulfide-ion species and smithsonite surfaces in the absence with and without ammonia liquor was investigated. The results of zeta potential and sulfide ion adsorption indicated that NH3·H2O addition promoted the transfer of sulfur in the pulp solutions onto the smithsonite surfaces. Time-of-flight secondary ion mass spectrometry and X-ray photo-electron spectroscopy analysis indicated that the zinc sulfide species was composed of zinc monosulfide and zinc polysulfide and was reinforced by NH3·H2O addition. The distribution ratio of polysulfide in the whole S species increased. The results shed light on reinforcement of the smithsonite sulfidation mechanism with ammonia liquor addition.
Sensitivity Experiments of the Local Wildland Fire with WRF-Fire Module
Lai Shaojun,Chen Haishan,He Fen,Wu Weijie 한국기상학회 2020 Asia-Pacific Journal of Atmospheric Sciences Vol.56 No.4
In this paper, it is discussed the performance of theWeather Research and Forecasting (WRF) model coupled with a wildland firebehavior module (WRF-Fire model) by the observational data collected in an experiment with a low-intensity prescribed fire (LIPF) conducted in the New Jersey Pine Barrens (NJPB) on March 6, 2012. The sensitivity experiments of theWRF-Fire model are carried out to investigate the interactions between the wildland fire and the atmospheric planetary boundary layer. The twoway WRF-Fire model conofigured with fire and large eddy simulation (LES) mode is used to explore the fire characteristics of perimeter shape, intensity, spread direction and external factors ofwind speed, and to discuss how these external parameters affect the fire, and the interactions between the atmosphere and fire. Results show that the sensitive experiments can provide the meteorological elements close to observations, such as the temperatures, winds and turbulent kinetic energy near the surface in the vicinity of the fire. The simulations also can reproduce the fire spread shape and speed, fire intensity, and heat flux released from fire. From the view of energy, the heat flux feed back to the atmospheric model and heat the air near the surface, which will induce strong thermal and dynamic instability causing strong horizontal convergence and updraft, and form the fire-induced convective boundary layer. The updraft will be tilted downstream of the fire area based on the height of the ambient winds. Due to the effect of the this updrafts, the particles and heat from the fuel combustion can be transported to the downwind and lateral regions of the fire area. Meanwhile, there is a downdraft flow with higher momentum nearby the fire line transporting fresh oxygen to the near surface, which will increase winds behind the fire line, accelerate the rate of spread (ROS) and make the fire spread to a larger area. Ultimately, a fire-induced climate is established.
Liang Shaojun,Zhang Manhong,Zhu Hanming,Yue Song 한국물리학회 2023 Current Applied Physics Vol.49 No.-
Energy filtering effect has been demonstrated an effective strategy to enhance the electrical transport properties and reduce the thermal conductivity of thermoelectric materials. However, to realize the energy filtering effect is so challenging, needing delicate design for specific system, which requires appropriate nano inclusions to well disperse in the pristine matrix and proper interface to produce potential energy barrier. Herein, we report a possible strategy to magnify the energy filtering effect in Cu-doped p-type CuxBi0.5Sb1.5Te3 films prepared by intermittent magnetron co-sputtering technique. Due to the simultaneous optimization of the electrical conductivity and Seebeck coefficient with appreciable magnitude, the power factor shows a 564% enhancement for x = 0.015 in comparison with that of the undoped film. This enhancement is presumably due to a modulable energy filtering effect in the sandwich-structured film system, which provides a potential application for other thermoelectric materials.
Broadband Stacked Patch Antenna with Low VSWR and Low Cross-Polarization
Zhongbao Wang,Shaojun Fang,Shiqiang Fu 한국전자통신연구원 2010 ETRI Journal Vol.32 No.4
A low cross-polarization broadband stacked patch antenna is proposed. By means of the stacked patch configuration and probe-fed strip feed technique, the VSWR 1.2:1 bandwidth of the patch antenna is enhanced to 22% from 804 MHz to 1,002 MHz, which outperforms the other available patch antennas (<10%). Furthermore, the antenna has a cross-polarization level of less than –20 dB and a gain level of about 9 dBi across the operating bandwidth. Simulation results are compared with the measurements, and a good agreement is observed.
Jinming Xu,Shaojun Xie,Binfeng Zhang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4
For grid-connected LCL-filtered inverters, dual-loop current control with an inner-loop active damping (AD) based on capacitor current feedback is generally used for the sake of current quality. However, existing studies on capacitor current feedback AD with a control delay do not reveal the mathematical relation among the dual-loop stability, capacitor current feedback factor, delay time and LCL parameters. The robustness was not investigated through mathematical derivations. Thus, this paper aims to provide a systematic study of dual-loop current control in a digitally-controlled inverter. At first, the stable region of the inner-loop AD is derived. Then, the dual-loop stability and robustness are analyzed by mathematical derivations when the inner-loop AD is stable and unstable. Robust design principles for the inner-loop AD feedback factor and the outer-loop current controller are derived. Most importantly, ensuring the stability of the inner-loop AD is critical for achieving high robustness against a large grid impedance. Then, several improved approaches are proposed and synthesized. The limitations and benefits of all of the approaches are identified to help engineers apply capacitor current feedback AD in practice.
Kunshan Xu,Shaojun Xie 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5
The rapid and correct isolation of faulty submodules (SMs) is of great importance for improving the reliability of modular multilevel converters (MMCs). Therefore, a fast diagnosis method containing fault detection and fault location determination was presented in this paper. An improved incremental predictive model of arm current was proposed to detect failures, and the multi-step prediction method was used to eliminate the negative impact of disturbances. Moreover, a control method was proposed to strengthen the fault characteristics to rapidly locate faulty arms and faulty SMs by detecting the variation rate of the SM capacitor voltage. The proposed method can rapidly and easily locate faulty SMs under different load conditions without the need for additional sensors. The experimental results have validated the effectiveness of the proposed method by using a single-phase MMC with four SMs per arm.