Simulation of Fracture Process of Lightweight Aggregate Concrete Based on Digital Image Processing Technology

The mechanical properties and failure mechanism of lightweight aggregate concrete(LWAC)is a hot topic in the engineering field,and the relationship between its microstructure and macroscopic mechanical properties is also a frontier research topic in the academic field.In this study,the image processing technology is used to establish a micro-structure model of lightweight aggregate concrete.Through the information extraction and processing of the section image of actual light aggregate concrete specimens,the mesostructural model of light aggregate concrete with real aggregate characteristics is established.The numerical simulation of uniaxial tensile test,uniaxial compression test and three-point bending test of lightweight aggregate concrete are carried out using a new finite element method-the base force element method respectively.Firstly,the image processing technology is used to produce beam specimens,uniaxial compression specimens and uniaxial tensile specimens of light aggregate concrete,which can better simulate the aggregate shape and random distribution of real light aggregate concrete.Secondly,the three-point bending test is numerically simulated.Thirdly,the uniaxial compression specimen generated by image processing technology is numerically simulated.Fourth,the uniaxial tensile specimen generated by image processing technology is numerically simulated.The mechanical behavior and damage mode of the specimen during loading were analyzed.The results of numerical simulation are compared and analyzed with those of relevant experiments.The feasibility and correctness of the micromodel established in this study for analyzing the micromechanics of lightweight aggregate concrete materials are verified.Image processing technology has a broad application prospect in the field of concrete mesoscopic damage analysis.

Hybrid Simulation of ±500 kV HVDC Power Transmission Project Based on Advanced Digital Power System Simulator

In order to effectively imitate the dynamic operation characteristics of the HVDC （high voltage direct current） power transmission system at a real ±500kV HVDC transmission project, the electromechanical-electromagnetic transient hybrid simulation was carried out based on advanced digital power system simulator （ADPSS）. In the simulation analysis, the built hybrid model＇s dynamic response outputs under three different fault conditions are considered, and by comparing with the selected fault recording waveforms, the validities of the simulation waveforms are estimated qualitatively. It can be ascertained that the hybrid simulation model has the ability to describe the HVDC system＇s dynamic change trends well under some special fault conditions.

POWER FLOW ANALYSIS AND APPLICATION SIMULATION OF ELECTROMAGNETIC CONTINUOUSLY VARIABLE TRANSMISSION

With the structure of two air gaps and two rotors, the electromagnetic continuously variable transmission（EMCVT） is a novel power-split continuously variable transmission（CVT）. There are two kinds of power flowing through the EMCVT, one is mechanical power and the other is electric power. In the mean time, there are three power ports in the EMCVT, one is the outer rotor named mechanical power port and the other two are the inner rotor and the stator named electric power ports. The mechanical power port is connected to the driving wheels through the final gear and the electric ports are connected to the batteries through the transducers. The two kinds of power are coupled on the outer rotor of the EMCVT. The EMCVT can be equipped on the conventional vehicle being regarded as the CVT and it also can be equipped on the hybrid electric vehicle（HEV） as the multi-energy sources assembly. The power flows of these two kinds of applications are analysed. The back electromotive force（EMF） equations are illatively studied and so the dynamic mathematic model is theorized. In order to certify the feasibility of the above theories, three simulations are carried out in allusion to the above two kinds of mentioned applications of the EMCVT and a five speed automatic transmission（AT） vehicle. The simulation results illustrate that the efficiency of the EMCVT vehicles is higher than that of the AT vehicle owed to the optimized operation area of the engine. Hence the fuel consumption of the EMCVT vehicles is knock-down.

Some of Advances on the Error Analysis in the Frequency Domain for a Digital Simulation Model

This paper surveys a number of recent advances in the error analysis in the frequency domain for a digital simulation model. It is emphasized to discuss the errors in characteristic roots and transfer funcnon of the digital simulation model, the frequency domain errors of the data transfers between thesimulation submodels, and some compensation methods for the errors. Some of the questions to be answered are also presented.

Thermo-Dynamical Analysis on Electricity-Generation Subsystem of CAES Power Plant

Besides pumped hydropower, Compressed Air Energy Storage (CAES) is the other solution for large energy storage capacity. It can balance fluctuations in supply and demand of electricity. CAES is essential part of smart power grids. Linked with the flow structure and dynamic characteristic of electricity generation subsystem and its components, a simulation model is proposed. Thermo-dynamical performance on off-design conditions have been analyzed with constant air mass flux and constant gas combustion temperature. Some simulation diagrams of curve are plotted too. The contrast of varied operation mode thermal performance is made between CAES power plant and simple gas turbine power plant.

Analysis of cooperation equilibrium of participants in power battery recycling chains considering information barrier

In the era of large-scale retirement of power batteries,there are information barriers and high recovery costs in their recycling.In view of this,in this study we constructed a tripartite evolutionary game model of the cooperation between power battery production and recycling enterprises and government participation.We analyzed the strategic choice of the three parties in the process of power battery recycling and simulated the influence of participants'willingness and information barriers on the strategic choices of the parties.The results showed that power battery production and recycling enterprises,and the government are affected by each other's willingness to participate at different degrees.The willingness of power battery manufacturers and recycling enterprises to cooperate with each other decreased with increases in information barriers.By analyzing the impact of information barrier on power battery recycling,some suggestions are put forward to provide decision-making reference for promoting the sustainable development of power battery industry.

Bubble dynamics properties of B-particles in a quasi-2D gas-solid fluidized bed:Computational particle fluid dynamics numerical simulation and post-processed by digital image analysis technique

Bubble dynamics properties play a crucial and significant role in the design and optimization of gas-solid fluidized beds.In this study,the bubble dynamics properties of four B-particles were investigated in a quasi-two-dimensional(quasi-2D)fluidized bed,including bubble equivalent diameter,bubble size distribution,average bubble density,bubble aspect ratio,bubble hold-up,bed expansion ratio,bubble radial position,and bubble velocity.The studies were performed by computational particle fluid dynamics(CPFD)numerical simulation and post-processed with digital image analysis(DIA)technique,at superficial gas velocities ranging from 2u_(mf) to 7u_(mf).The simulated results shown that the CPFD simulation combining with DIA technique post-processing could be used as a reliable method for simulating bubble dynamics properties in quasi-2D gas-solid fluidized beds.However,it seemed not desirable for the simulation of bubble motion near the air distributor at higher superficial gas velocity from the simulated average bubble density distribution.The superficial gas velocity significantly affected the bubble equivalent diameter and evolution,while it had little influence on bubble size distribution and bubble aspect ratio distribution for the same particles.Both time-averaged bubble hold-up and bed expansion ratio increased with the increase of superficial gas velocity.Two core-annular flow structures could be found in the fluidized bed for all cases.The average bubble rising velocity increased with the increasing bubble equivalent diameter.For bubble lateral movement,the smaller bubbles might be more susceptible,and superficial gas velocity had a little influence on the absolute lateral velocity of bubbles.The simulated results presented a valuable and novel approach for studying bubble dynamics properties.The comprehensive understanding of bubble dynamics behaviors in quasi-2D gas-solid fluidized beds would provide support in the design,operation,and optimization of gas-solid fluidized bed reactors.

Development of Simulated Testbed for Electrical Power Subsystem of a Certain Kind of Satellite

In order to testify and examine the ability and correctness of an expert system for diagnosing the faults in the electrical power system of a certain kind of satellite, the authors have developed a simulated testbed according to the operational principle of the electrical power system. This paper takes the solar battery array as an instance to introduce the designing principle of its hardware circuits, and presents the methods to design the interface and the software program of the single-chip microprocessor system. The software scheme of the upper computer is introduced at the end of this paper. It has been proved that this simulated system could effectively achieve the complete functions coupled with the simple design by using of various mature techniques in the fields of electronic circuits, single-chip microprocessor and numerical emulation.

HIL Simulation of a Mixed Islanded Power Network with External DSP Regulator

The present paper deals with the development of a modular, flexible and structured block to block approach for the study of regulators by implementing the different blocks on a DSP （digital signal processor）. The proposed low-cost approach has been applied and validated by the implementation of an industrial regulator in a real time hardware-in-the-loop simulation of a mixed islanded power network including precise models of the hydraulic system. The studied network is constituted of three different types of electrical power generation systems and a consumer.

基于SimPowerSystems的电力系统仿真与潮流分析

叙述了用MATLAB软件中的SIMULINK以及SimPowerSystems工具箱进行简单电力系统仿真的基本过程,并利用Powergui对相应系统进行动态仿真和系统潮流分析.对位于不同节点类型处的负荷模型仿真系统进行了讨论,并给出了模型的实现方法.

基于Power World Simulator的地区电网静态安全稳定性分析

电力系统具有良好的稳定性是保证电网正常运行的关键,充分应用Power World Simulator电力系统仿真软件对我国西北某地区实际电网进行安全稳定性分析。根据给定的实际电网运行数据搭建电网模型并进行潮流计算,将潮流计算结果与静态安全理论相结合,对该地区电网模型进行N-1静态安全性分析。针对线路负载率过高以及节点母线电压越限的情况,提出解决措施以达到提高电网运行稳定性的目的。

Automatic Voltage Regulator Test of Three Gorges Right Bank Hydropower Station

Based on real-time digital simulations(RTDS),a laboratory environment similar to the real-time operation situation of the Three Gorges Hydropower Station is established.Then,the causes for the power fluctuation of the second generator by errors in the rotor rotating speed calculation are found,and the tuning method of the speed related parameters are given.The damping and reverse tuning characteristics of power system stabilizers(PSSs)in the digital automatic voltage regulator(AVR)are compared and investigated in the frequency range of 0.18-1.1 Hz.The efficiency of the proposed tuning method for ensuring power system stability is verified by RTDS.Finally,field tests show the validity of the laboratory test results.

Development of nuclear power plant real-time engineering simulator

A nuclear power plant real-time engineering simulator was developed based on general-purpose ther- mal-hydraulic system simulation code RELAP5. It mainly consists of three parts:improved thermal-hydraulic system simulation code RELAP5,control and protection system and human-machine interface. A normal transient of CHASHMA nuclear power plant turbine step load change from 100% to 90% of full power,was simulated by the en- gineering simulator as an application example. This paper presents structure and main features of the engineering simulator,and application results are shown and discussed.

System Simulation Science and Simulation System Technology

This paper mainly discusses the following problems: the important meaning and special function of simulation system; the definition, contents and relationship of system and system simulation science; the definition and technology of simulation system and its equipments; and systematic description and exploration in relation to the developing trend of system simulation science and simulation system technology.

Numerical Investigation on Power Outputs of a Wind Turbine Sited over Continuous Hilly Terrain

The location of wind turbines on a continuous hilly terrain has an influence on its power outputs.A CFDbased approach is developed to investigate the complex aerodynamic interference between two wind turbines and the hilly terrain.In this approach,a new three-dimensional model of hilly terrain is established to analyze its viscous effect,and a wind shear is modelled through logarithmic function.They are coupled into the aerodynamics of wind turbine based on“FLUENT”software.Then we apply the proposed method to the NREL Phase VI wind turbines and compare with an experiment in the atmospheric boundary layer(ABL)wind tunnel to validate its accuracy.The simulation also investigates the power outputs of wind turbines on the flat ground and the continuous hilly terrain by changing the location of the wind turbine related to the hilly terrain and the shape of the 1st hill.The results show that the wind turbine located on the top of the 2nd hill has the maximum power;and that when the wind turbine is located on the downstream of the hill,the stall zone should be avoided,and the power of the wind turbine located on the side of the hill is higher than that of the wind turbine located on the front and rear of the hilly terrain.

Hydraulic Power Take-off and Buoy Geometries Charac-terisation for a Wave Energy Converter

In the past few decades, world energy consumption grew considerably. Regarding this fact, wave energy should not be discarded as a valid alternative for the production of electricity. Devices suitable to harness this kind of renewable energy source and turn it into electricity are not yet commercially competitive. The work described in this paper aims to contribute to this field of research. It is focused on the design and construction of robust, simple and affordable hydraulic Power Take-Off using hydraulic commercial components.

风电机组运行动态数字孪生建模及半物理仿真

面向数字孪生技术所提出的精准映射与实时仿真需求,针对大型风电机组复杂非线性运行特性,提出了一种多输入-多输出(multi-input multi-output,MIMO)有限差分域-混合半机理(finite difference domain-hybrid semi-mechanical,FDD-HSM)数字孪生建模方法,建立了含物理控制器的风电机组数字孪生半物理仿真系统。推导机组集成动态MIMO-FDD-HSM模型结构;定义可表征机组运行工况的有限差分回归向量,完成全工况下有限差分空间紧致凸划分、参数模型辨识以及非参数模型训练;联合物理控制器搭建风电机组数字孪生仿真系统,开展硬件在环实时仿真。结果表明:该仿真系统具有高精度、实时逼近能力。

动力电池铸铝箱体力学分析与优化

动力电池箱体承载着动力电池,其力学性能影响着结构安全,2020年颁布了《GB 38031-2020电动汽车用动力蓄电池安全要求》,其涉及的测试项目主要有振动、机械冲击、模拟碰撞、挤压几方面。对某动力电池箱体进行了初步的静力学及模态仿真分析,并改进了部分结构设计,最后依据国标中的力学测试要求,完成了对动力电池箱体的振动、机械冲击、模拟碰撞、挤压几项仿真分析,仿真结果显示该电池箱体能够满足新国标力学性能测试,最终该电池箱体也顺利通过了国家标准的强检测试。

基于交互式设计超材料建模与分析的MCR-WPT效率提升研究

超材料具有特殊的磁场调控能力,被广泛关注并应用于磁耦合谐振无线电能传输(MCR-WPT)领域,但寻求针对特定领域目标需求的超材料设计具有挑战性.目前,超材料的一般设计方法为S参数反演法和等效电路法,设计流程通常需要多次建模仿真得到目标参数,该过程较为繁琐耗时.对此,深入分析上述两种设计方法的特性并将二者结合,采用HFSS与MATLAB软件交互设计和优化用于MCR-WPT特性提升的超材料,有效简化了超材料的设计过程.以无线电能传输效率优化为目标设计方形和Koch两种超材料单元,分析对比两种单元的电磁特性.搭建工作频率为6.78 MHz的MCR-WPT系统实验平台,探究两种超材料对传输效率的影响.实验结果表明,方形超材料和Koch超材料分别实现了28.4%和24.6%的最大传输效率提升,证明了交互设计可以更简便地设计超材料并且用于无线电能传输系统传输效率的提升.

原位煤气化化学链燃烧发电系统的过程模拟

运用Aspen Plus软件构建了以Fe_(2)O_(3)/FeO为氧载体的600 MW原位煤气化化学链燃烧发电系统。基于系统的仿真结果,分别进行了能量、[火用]和[火用]成本分析。结果表明:原位煤气化化学链燃烧发电系统的净热效率为35.38%;系统中内部[火用]损失最大的组件为空气反应器,占原位煤气化化学链燃烧子系统组件总内部[火用]损失的28.39%;水汽系统总内部[火用]损失在整个系统中占比较小,仅为化学链燃烧子系统的14%;原位煤气化化学链燃烧发电系统中单位[火用]成本最大的组件为空气预热器,其值为3.88,再热器、省煤器和过热器的产品单位[火用]成本也较大。