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Innovated Inertia Control of DFIG with Dynamic Rotor Speed Recovery

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CSEE Journal of Power and Energy Systems 2022年第5期8卷 1417-1427页

作者： Huanjing lao Li Zhang Tong Zhao Liang Zou School of Electrical Engineering Shandong UniversityJinan 250061China

High wind power penetration(WPP)is challenging system frequency *** a countermeasure,virtual inertia controls are introduced,utilizing kinetic energy(KE)stored in wind turbine generators(WTGs)for frequency *** restoration,generation efficiency of WTGs will be degraded after inertia *** counter this issue,we propose an inertia control scheme of a doubly fed induction generator(DFIG),aiming at achieving dynamic inertia recovery regarding both KE and DC link *** asymmetrical droop control,referred to as the rate of change of frequency(RoCoF),is proposed for KE *** upper boundary of droop gain is extended to give full play to converters and is revised,considering the system frequency state,to counter positive feedback issues induced by reversible gain regulation,which is restricted by KE to ensure stable operations as *** inertial DC energy needed to cooperate with KE control regarding countering small fluctuations,is improved with an orderly recovery *** studies are conducted under dynamic wind conditions and the results indicate that with our proposed scheme,the ability of dynamic inertia recovery can be obtained,bringing DFIG higher generation efficiency and more adequate operation margin for sustained ***,the inertial frequency response and fluctuation suppression ability is well maintained.

关键词： Doubly fed induction generator(DFIG) dynamic rotor speed recovery frequency regulation generation efficiency high wind power penetration.

Two New Amides from the Roots of Acorus Tatarinowii Schott

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Chinese Chemical Letters 1997年第1期8卷 35-36页

作者： Wang, MF lao, an Wang, HC ACAD SINICA SHANGHAI INST MAT MEDSHANGHAI 200031PEOPLES R CHINA

Two new amides, tataramide A (1) and tataramide B (2), were isolated from the roots of Acorus tatarinowii Schott. Their structures were determined by spectroscopic methods.

关键词： Two New Amides from the Roots of Acorus Tatarinowii Schott

Water Responsive Fabrics with Artificial Leaf Stomata

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Advanced Fiber Materials 2023年第3期5卷 1076-1087页

作者： Lihong lao Hedan Bai Jintu Fan Department of Fiber Science&Apparel Design Cornell UniversityIthacaNY 14853USA Present Address:Department of Materials Science and Engineering University of Illinois Urbana-ChampaignUrbanaIL 61801USA Sibley School of Mechanical and Aerospace Engineering Cornell UniversityIthacaNY 14853USA Present Address:Querrey Simpson Institute for Bioelectronics Northwestern UniversityEvanstonIL 60208USA School of Fashion and Textiles Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina

Due to fiber swelling,textile fabrics containing hygroscopic fibers tend to decrease pore size under wet or increasing humid-ity and moisture conditions,the reverse being ***,for personal thermal regulation and comfort,the opposite is desirable,namely,increasing the fabric pore size under increasing humid and sweating conditions for enhanced ventila-tion and cooling,and a decreased pore size under cold and dry conditions for heat *** paper describes a novel approach to create such an unconventional fabric by emulating the structure of the plant leaf stomata by designing a water responsive polymer system in which the fabric pores increase in size when wet and decrease in size when *** new fabric increases its moisture permeability over 50%under wet *** a water responsive fabric can find various applications including smart functional clothing and sportswear.

关键词： Breathable fabric Fabric pores Hydrogel Leaf stomata Water responsive

Atomistic Evolution of Hf_(2)S/γ′Interfaces in a Hf‑containing Ni‑based Single‑Crystal Superalloy

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Acta Metallurgica Sinica(English Letters) 2023年第6期36卷 1038-1046页

作者： Zhezhu lao Xingpu Zhang Jiangwei Wang Jixue Li School of Materials Science and Engineering Zhejiang UniversityHangzhou 310027China Wenzhou Key Laboratory of Novel Optoelectronic and Nano Materials Institute of WenzhouZhejiang UniversityWenzhou 325006China

The evolution of interfacial structures of needle-like sulfides in a Hf-containing Ni-based single-crystal superalloy has been studied with a combination of the state-of-the-art spherical aberration-corrected scanning transmission electron microscope and three-dimensional electron diffraction *** Hf_(2)S precipitates possess an ABACBC stacking sequence with layered structure of *** Hf_(2)S/γ′interfaces exhibit different types of metastable interfacial structures,including the sharp interface with segregated Hf atom columns,the one with indistinct transition region and the one with ordered transition *** metastable structures represent the different stages of Hf_(2)S growth during the aging process,based on which a sequential layer-by-layer growth mechanism of Hf_(2)S is proposed.

关键词： Ni-based single-crystal superalloy HHf_(2)S precipitate Atomic structure Interfacial segregation

Evolution Behaviors of Oxides in Severely Plastic Deformed Region of AISI 52100 Steel during Dry Sliding Wear

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Journal of Materials Science & Technology 2017年第4期33卷 330-337页

作者： Yuanxia lao Hao Du Tianying Xiong Yuan Wang Key Laboratory of Radiation Physics and Technology Ministry of EducationInstitute of Nuclear Science and TechnologySichuan University Division of Surface Engineering of Materials Institute of Metal ResearchChinese Academy of Sciences

Under dry sliding wear, the evolution of oxides in severely plastic deformed（SPD） regions of metals has a great impact on the wear behaviors. To study the evolution behaviors of oxides in the SPD region, an SPD region was prefabricated on the surface of AISI 52100 steel by supersonic fine particle bombarding（SFPB） treatment. Dry sliding wear tests were carried out on both of the SFPB-treated and original *** volume loss of the SPBF-treated samples were compared with those of the original samples at different loads. Microstructure, element composition and oxides distribution in the SPD region were characterized by scanning electron microscopy（SEM）, transmission electron microscopy（TEM） and an electron probe microanalysis（EPMA）. The results show that the evolution behaviors of the oxides in the SPD region change significantly with the load. Under low loads, oxides are usually formed on the contact surface. It inhibits adhesive wear on the steel. However, under high loads, oxides are apt to distribute along the cracks in the subsurface layer. The internal oxidation along the cracks can accelerate the cracks propagation, resulting in severe delamination wear on the steel.

关键词： Sliding wear Plastic deformation Oxides Defects Steel

Forced Responses on a Radial Turbine with Nozzle Guide Vanes

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Journal of Thermal Science 2014年第2期23卷 138-144页

作者： LIU Yixiong YANG Ce MA Chaochen lao DaZhong School of Mechanical Engineering Beijing Institute of Technology

Radial turbines with nozzle guide vanes are widely used in various size ***,due to the interferences with guide vanes,the blades of impellers are exposed to intense unsteady aerodynamic excitations,which cause blade vibrations and lead to high cycle failures(HCF).Moreover,the harmonic resonance in some frequency regions are unavoidable due to the wide operation *** to achieve a detail insight into vibration characteristics of radial flow turbine,a numerical method based on fluid structure interaction(FSI) is ***,the unsteady aerodynamic loads are determined by computational fluid dynamics(CFD).And the fluctuating pressures are transformed from time domain to frequency domain by fast Fourier-transform(FFT).Then,the entire rotor model is adopted to analyze frequencies and mode shapes considering mistuning in finite element(FE) ***,harmonic analyses,applying the pressure fluctuation from CFD,are conducted to investigate the impeller vibration behavior and blade forced response in frequency *** prediction of the vibration dynamic stress shows acceptable agreement to the blade actual damage in consistent tendency.

关键词： radial turbine forced response modal analysis harmonic resonance

Non-axisymmetric Flow Characteristics in Centrifugal Compressor

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Journal of Thermal Science 2015年第4期24卷 313-322页

作者： WANG Leilei lao Dazhong LIU Yixiong YANG Ce School of Mechanical Engineering Beijing Institute of Technology College of Mechanical and Electrical Engineering Hebei University of Engineering

The flow field distribution in centrifugal compressor is significantly affected by the non-axisymmetric geometry structure of the *** experimental and numerical simulation methods were adopted in this work to study the compressor flow field distribution with different flow *** results show that the pressure distribution in volute is characterized by the circumferential non-uniform phenomenon and the pressure fluctuation on the high static pressure zone propagates reversely to upstream,which results in the non-axisymmetric flow inside the *** non-uniform level of pressure distribution in large flow condition is higher than that in small flow condition,its effect on the upstream flow field is also ***,the non-uniform circumferential pressure distribution in volute brings the non-axisymmetric flow at impeller *** different flow conditions,the circumferential variation of the absolute flow angle at impeller outlet is also ***,the non-axisymmetric flow characteristics in internal impeller can be also reflected by the distribution of the mass *** high static pressure region of the volute corresponds to the decrease of mass flow in upstream blade channel,while the low static pressure zone of the volute corresponds to the increase of the mass *** small flow condition,the mass flow difference in the blade channel is bigger than that in the large flow condition.

关键词： centrifugal impeller static pressure distortion non-axisymmetric flow mass flow blade loading

Probabilistic characterization of cyclic shear modulus reduction for normally to moderately over-consolidated clays

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Earthquake Engineering and Engineering Vibration 2016年第3期15卷 495-508页

作者： Iok-Tong Ng Ka-Veng Yuen Ngai-Kuan lao Dept.of Civil and Environmental Engineering Faculty of Science and Technology University of Macao

Evaluation of the cyclic shear modulus of soils is a crucial but challenging task for many geotechnical earthquake engineering and soil dynamic issues. Improper determination of this property unnecessarily drives up design and maintenance costs or even leads to the construction of unsafe structures. Due to the complexities involved in the direct measurement, empirical curves for estimating the cyclic shear modulus have been commonly adopted in practice for simplicity and economical considerations. However, a systematic and robust approach for formulating a reliable model and empirical curve for cyclic shear modulus prediction for clayey soils is still lacking. In this study, the Bayesian model class selection approach is utilized to identify the most significant soil parameters affecting the normalized cyclic shear modulus and a reliable predictive model for normally to moderately over-consolidated clays is proposed. Results show that the predictability and reliability of the proposed model out performs the well-known empirical models. Finally, a new design chart is established for practical usage.

关键词： Bayesian analysis cyclic shear modulus empirical model geotechnical earthquake engineering normally tomoderately over-consolidated clays

Heat Transfer Characteristics of Printed Circuit Heat Exchanger with Supercritical Carbon Dioxide and Molten Salt

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Journal of Thermal Science 2021年第3期30卷 880-891页

作者： lao Jiewei FU Qianmei WANG Weilong DING Jing LU Jianfeng School of Material Science and Engineering/School of Intelligent Systems Sun Yat-Sen UniversityGuangzhou 510006China

Molten salt and supercritical carbon dioxide(S-CO_(2))are important high temperature heat transfer media,but molten salt/S-CO_(2) heat exchanger has been seldom *** present paper,heat transfer in printed circuit heat exchanger(PCHE)with molten salt and S-CO_(2) is simulated and *** S-CO_(2) can be drove along passage wall by strong buoyancy force with large density difference,its heat transfer is enhanced by natural *** inlet region,natural convection weakens along flow direction with decreasing Richardson number,and the thermal boundary layer becomes thicker,so local heat transfer coefficient of S-CO_(2) significantly *** outlet region,turbulent kinetic energy gradually increases,and then heat transfer coefficient increases for turbulent heat transfer *** with transcritical CO_(2) with lower inlet temperature,local heat transfer coefficient of S-CO_(2) near inlet is lower for smaller Richardson number,while it will be higher for larger turbulent kinetic energy near *** of PCHE is mainly determined by the pressure drop in molten salt passage and the heat transfer resistance in S-CO_(2) *** molten salt passage width increases,molten salt pressure drop significantly decreases,and overall heat transfer coefficient slightly changes,so the comprehensive performance of PCHE is *** a result,PCHE unit with three semicircular passages and one semi-elliptic passage has better performance.

关键词： heat exchanger molten salt supercritical carbon dioxide numerical simulation