内燃机零部件有限元计算中边界条件处理的研究

有限元方法已经成为内燃机零部件应力和变形计算的主要手段,但是目前在内燃机零部件有限元分析中采用的边界条件是否合理,有无必要采用更符合实际的边界条件?本文以曲轴为例,模拟实际状况,采用不同的边界条件进行了有限元计算。计算结果表明,边界条件处理对曲轴有限元分析结果影响很大。因此,为了提高内燃机零部件有限元计算结果的精度,非常有必要根据实际情况确定边界条件。     

柴油机气缸盖非稳定热负荷的有限元分析

本文提供了一个可适用于分析柴油机零部件非稳定温度场和准稳态热应力场的二维有限元计算程序。在利用实测温度历程反求缸内第三类边界条件的基础上,研究并提出了非稳定热负荷气缸盖的计算分析方法和边界条件的确定方法,揭示了柴油机起动工况下气缸内传热的一些规律。程序的应用及研究的结果对今后新机型开发、预估技术的发展及分析引进机型具有一定价值。本程序采用了空间域内有限元划分、时间域上有限差分网格划分、冷却水侧边界条件迭代求解的处理方法。     

柴油机机械-液压调速器耦合动力学特性分析

以计算多体系统动力学理论为指导,建立了柴油机机械-液压调速系统的耦合动力学分析模型.分析并正确添加了构件间的约束关系、模型的初始条件以及边界条件;在此基础上模拟调速器的工作过程并对其动态特性进行分析.结果表明该模型及求解过程的可行性和可靠性,为调速系统的性能和结构优化奠定了一定基础.文中的耦合建模和求解过程也可以应用于其它液机耦合设备.     

汽包水位的一种快速动态简化仿真模型

汽包水位是确定锅炉是否安全稳定运行的重要参数之一,建立汽包水位的动态模型并进行仿真,对研究锅炉的动态特性和确定控制策略具有重要意义.在分析已有文献对汽包建模和仿真方法的基础上,从汽包变工况下水位变化的机理出发,通过对汽包内工质相变过程进行更为合理的假设和简化,建立了汽包水位动态模型.利用所建模型对汽包的动态特性进行了仿真研究,结果不但证实了模型的有效性,并且可以满足更大范围的动态仿真要求,可以为各类汽包建模仿真做参考.     

柴油机液压调速器动力学建模研究

以计算多体系统动力学理论为指导,建立了柴油机液压调速系统的耦合动力学分析模型。分析并正确添加了构件间的约束关系、模型的初始条件以及边界条件,并以动力连杆为例构建其刚柔混合动力学模型;在此基础上模拟调速器的工作过程并对其动态特性进行分析。结果证明了该模型及求解过程的可行性,为调速系统的性能和结构优化奠定了一定基础。文中的耦合建模方法和求解过程也可以应用于其它液机耦合设备。     

基于Simulink S函数的动力循环回热器动态分布参数建模与仿真

回热器对提高以燃气轮机为代表的动力循环装置系统的效率具有非常重要的意义。本文介绍了一种回热器动态分布参数的建模与仿真的方法。这种方法的基本思路是,对回热器动态模型的偏微分方程,在空间方向利用差分进行人工离散,而时间方向利用Simulink S函数提供的求解器进行求解。这种方法的优点是可利用Simulink的多种求解方法进行求解,并且可直接用于系统仿真中。本文以某种类型的换热器为例,利用上述方法求解得到了该换热器在热源入口温度变化时的动态特性,结果表明本方法是非常有效的。     

水电站油系统虚拟现实技术应用研究

利用计算机虚拟现实技术实现了水电站油系统的三维建模及浏览.实现时,将整个油系统分解为较小的零部件进行静态建模,并利用虚拟技术及LOD节点进行分层次的动态集成,实现了油系统场景边浏览边装配的分精度显示,减少了内存需求,加快了浏览速度,可用于水电站辅助设备培训、教学等场合.     

发动机零部件有限元技术应用的新进展

发动机零部件的设计是有限元技术最早的应用领域之一。有限元技术的应用提高了发动机零部件设计的可靠性,缩短了设计周期,大大推动了发动机工业的发展。本文从复杂零部件有限元网格生成技术（包括基于几何自动建立节点、单元模型和不基于几何直接建立节点、单元模型两方面）、复杂边界条件的确定和施加以及发动机零部件有限元分析的主要课题及特点等３方面概述了目前国内外发动机零部件有限元技术应用的新进展,同时总结了存在的主要问题,为今后更深入的研究应用提供参考。     

基于伪随机信号的链条锅炉动态特性辨识

有效的控制策略是提高工业锅炉运行经济性的重要保证,但是,控制系统的设计和优化升级都需要有合适的数学模型作为指导,对基于伪随机信号(PRBS)的工业锅炉动态特性辨识建模进行了比较深入的研究.着重讨论了PRBS信号参数的确定、数据的预处理,基于最小二乘的建模方法及模型的验证;以此为基础,还用MATLAB高级语言编写和开发了相应的辨识程序.结合某20 t/h链条工业锅炉的现场试验数据,利用该方法及其对应的程序对锅炉动态特性进行了建模,经验证,该辨识模型具有较高的可信度,可为锅炉控制系统设计和优化升级提供相应的理论基础和科学依据.     

内燃机曲轴动态设计技术研究

为探讨利用现代设计技术进行内燃机结构部件动态设计的方法和途径 ,本文以某大功率柴油机曲轴为例 ,结合CAD三维实体建模和有限元结构离散、模态分析、动响应计算、灵敏度分析、结构动力修改以及CAD二维工程布图等几方面内容 ,系统总结了利用现代设计技术对内燃机零部件进行动态设计的方法和流程。实例表明 ,利用本文的方法和技术 ,有效改善了结构的动态响应 ,提高了结构的可靠性和耐久性。本文针对内燃机曲轴动态设计的方法和流程 ,对其它机械产品的动态设计也具有参考价值。     

混流式水轮机转轮的刚强度分析

运用CFX软件对混流式转轮不同工况下的流场进行计算，得出作用在转轮上的压力。通过有限元软件把叶片的压力分布作为荷裁加载到转轮上．由此精确地计算变工况下的混流式转轮及叶片刚强度，确定出混流式转轮叶片上的应力和变形。     

An integrated reservoir-power system model for evaluating the impacts of wind integration on hydropower resources

Despite the potential for hydroelectric dams to help address challenges related to the variability and unpredictability of wind energy, at present there are few systems-based wind-hydro studies available in the scientific literature. This work represents an attempt to begin filling this gap through the development of a systems-based modeling framework for analysis of wind power integration and its impacts on hydropower resources. The model, which relies entirely on publicly available information, was developed to assess the effects of wind energy on hydroelectric dams in a power system typical of the Southeastern US (i.e., one in which hydropower makes up <10% of total system capacity). However, the model can easily reflect different power mixes; it can also be used to simulate reservoir releases at self-scheduled (profit maximizing) dams or ones operated in coordination with other generators to minimize total system costs. The modeling framework offers flexibility in setting: the level and geographical distribution of installed wind power capacity; reservoir management rules, and static or dynamic fuel prices for power plants. In addition, the model also includes an hourly ‘natural’ flow component designed expressly for the purpose of assessing changes in hourly river flow patterns that may occur as a consequence of wind power integration. Validation of the model shows it can accurately reproduce market price dynamics and dam storage and release patterns under current conditions. We also demonstrate the model's capability in assessing the impact of increased wind market penetration on the volumes of reserves and electricity sold by a hydroelectric dam.     

Modeling and design optimization of switched reluctance machine byboundary element analysis and simulation

Nonlinear boundary element analysis provides a more accurate and detailing tool for the design of switched reluctance machines than conventional equivalent-circuit methods. Design optimization through more detailed analysis and simulation can reduce development and prototyping costs and time to market. Firstly, magnetic field modeling of an industrial switched reluctance machine by the boundary element method is reported in this paper. Secondly, performance prediction and dynamic simulation of motor and control design are presented. Thirdly, magnetic forces that cause noise and vibration are studied, to include the effects of motor and control design variations on noise in the design process. Testing of such a motor in the NEMA 215-Frame size is carried out to verify the accuracy of modeling and simulation     

射流动力学边界条件的研究

对于射流的动力学边界条件,学术界一直没有全面、系统地论述过。线性和非线性动力学边界条件之间存在相互对应的关联关系,即线性动力学边界条件应该通过对非线性动力学边界条件的线性化得到,而现有文献中并未明确。本文从动力学边界条件的普适性原始表达式入手,对平面液膜、圆射流和环状液膜气液交界面三维扰动瑞利和瑞利-泰勒表面波的线性动力学边界条件和一维扰动多级瑞利表面波的非线性动力学边界条件进行详细的推导。     

基于IFC标准的水电设备信息模型创建技术研究

鉴于IFC标准强大的信息整合和处理能力,且目前已被大多数软件所支持,基于IFC标准设计水电设备信息模型并开展实际应用,以高度集成设备各维度的信息,避免因数据的异构性而造成的信息共享困难。首先分析了IFC标准的信息表达方式及其现有的设备信息实体,阐述了扩充IFC标准中设备实体的方法,并将设备信息进行分类规整,在此基础上提出了水电设备信息模型框架,进而给出使用此框架创建设备信息模型的流程和设备信息模型的解析方案。该方法已应用于某水电设备管理系统的开发中,为水电设备信息管理提供了一种新的信息数据源。     

水轮机随动系统仿真模型的精细化研究

随着大型机组的投产,各电网对水电站调节系统的要求也更加严格,建立更能体现机组实际运行情况、稳定性能良好、对大小扰动均能很好适应的仿真模型就显得尤为重要。随动系统作为调速器的执行部分,其内部存在的非线性环节主要由机械因素导致,这些环节在进行仿真建模研究时不可忽略。分析了随动系统非线性环节的产生原因及表现形式,探讨了接力器反应时间常数的现场试验方法,在Matlab/Simulink环境中搭建了精细化的随动系统仿真模型,对一般线性模型及精细化模型同时进行导叶阶跃仿真试验,并通过实测试验与仿真试验的结果对比,验证了包含非线性因素的精细化模型的优越性和准确性。     

Simulation-based optimization of thermal systems

This paper considers the design and optimization of thermal systems on the basis of the mathematical and numerical modeling of the system. Many complexities are often encountered in practical thermal processes and systems, making the modeling challenging and involved. These include property variations, complicated regions, combined transport mechanisms, chemical reactions, and intricate boundary conditions. The paper briefly presents approaches that may be used to accurately simulate these systems. Validation of the numerical model is a particularly critical aspect and is discussed. It is important to couple the modeling with the system performance, design, control and optimization. This aspect, which has often been ignored in the literature, is considered in this paper. Design of thermal systems based on concurrent simulation and experimentation is also discussed in terms of dynamic data-driven optimization methods. Optimization of the system and of the operating conditions is needed to minimize costs and improve product quality and system performance. Different optimization strategies that are currently used for thermal systems are outlined, focusing on new and emerging strategies. Of particular interest is multi-objective optimization, since most thermal systems involve several important objective functions, such as heat transfer rate and pressure in electronic cooling systems. A few practical thermal systems are considered in greater detail to illustrate these approaches and to present typical simulation, design and optimization results.     

A novel method for modeling dynamic air-gap eccentricity insynchronous machines based on modified winding function theory

This paper presents the modeling of synchronous machines under eccentric rotors. The winding function theory accounting for all space harmonics and presented by earlier researchers has been modified to adopt a nonsymmetric air-gap for the calculation of machine winding inductances. The effect of dynamic air-gap eccentricity on the inductances of a salient-pole synchronous machine using the modified winding function approach (MWFA) has been discussed. The coupled magnetic circuits approach has been used for simulating the machine behavior under healthy and eccentric rotor conditions. The simulation results are in close agreement with the experimental results     

6110型柴油机机体组件的有限元分析

利用有限元分析技术对 6 110型柴油机的机体、缸盖、曲轴、主轴承盖、缸套、飞轮壳等柴油机主要零部件的组合部件进行了结构强度和刚度分析 ,获得了结构改进的依据。利用专业的三维造型软件Pro/Engineer建立了较为精确的机体、缸盖、曲轴、主轴承盖、缸套、飞轮壳等零件的三维模型 ;用试验方法获得边界条件 ,并用试验结果标定有限元计算模型 ,从而获得了较好的计算结果。