超超临界汽轮机叶片热应力分析

针对超超临界机组高温环境下工作的叶片的安全性需要,采用了目前在工程领域广泛应用的CFD和FEA计算理论与方法,以实际汽轮机叶片的热应力求解过程为例,从其CFD求解叶型表面对流换热系数开始,说明了采用插值程序将CFD结果插值到有限元模型的过程以及该叶片在启动过程中的温度场和应力场求解方法。对汽轮机叶片的热应力分析规范提出了建议,该规范对汽轮机叶片与轮缘进行全面的强度分析和评估是可行的。     

基于双向流固耦合的汽油机排气歧管热应力分析

联合AVL-Fire与ABAQUS软件,对一台汽油机排气歧管进行温度场、热应力分析.首先利用AVL-Fire对排气歧管做内外流场CFD分析,得到排气歧管内外表面的热边界条件,即流体温度及换热系数;然后把热边界条件映射到有限元面单元,并通过有限元技术与排气歧管实体单元相耦合,通过ABAQUS算出排气歧管温度场,并把壁面温度场返回作为下一轮CFD计算的边界条件,再重复前一轮计算.如此反复,直至符合精度要求,最后计算热应力.     

起动过程涡轮叶片瞬态温度场的准稳态处理研究

考虑燃气涡轮发动机起动过程涡轮叶片与高温燃气的对流换热及叶片内部的热传导,通过瞬态流热 耦合计算和准稳态处理两种方法对涡轮叶片换热特性进行了研究,分析了叶片热惯性带来的温度滞后效应, 探索了一种对发动机起动过程进行准稳态处理的数值模拟方法,实现了对涡轮叶片瞬态温度场的快速求解。采用商业化软件ANSYS CFX 2019 R2对涡轮叶片分别进行流热耦合和非定常数值计算,结合外换热程序 “NPUSTAN7Z”求解叶片型线上的换热系数,并对叶片表面网格节点按照“K-近邻算法”进行三维数据插值, 得到计算涡轮叶片非稳态导热的第三类边界条件。分析涡轮叶片的瞬态温度场,发现起动过程中金属叶片 的热惯性导致其温升慢于来流的温升,其内部存在一定的纵向温度梯度和横向温度梯度,中弦滞后 > 前缘滞 后 >尾缘滞后,叶片中下部温度滞后 > 叶片上部滞后。通过对比瞬态耦合计算与准稳态计算的结果,认为准 稳态的方法可以快速准确地求解发动机起动过程涡轮叶片的瞬态温度场。     

转炉炉衬温度场的有限元分析

炉衬耐火材料的损坏与热负载引起的温度热应力有关,炉衬温度场是求解其热应力的基础,由于结构上的原因,用实测的方法很难得到炉衬的温度场。应用有限元数值计算软件,对转炉炉衬的温度场进行了数值模拟,仿真结果对进一步分析炉衬材料的热应力提供了坚实的理论基础。     

高压给水加热器管板单元的有限元分析

高压给水加热器管板上换热管呈正三角形排布.采用ANSYS通用有限元软件,对任意三根管子围成的单元进行分析.首先计算单元上的瞬态温度场,然后将节点温度作为载荷求解模型热应力;还有热载荷和机械载荷同时作用时的应力.得出布管区的管板温度能够在短时间内达到平衡;在管板与管子连接处热应力影响较大;耦合后应力主要受热应力影响,且随...     

汽机阀壳瞬态温度场及应力场仿真分析

采用结构分析有限元方法,对某型汽轮机阀壳冷态启动工况下的温度场、热应力场及综合应力场进行了分析计算,得出了关键点处详细的温度场及其对应的热应力场的变化规律,并估算了关键点处阀壳疲劳寿命.分析过程中采用CFD软件对阀壳内部流质速度场进行了仿真模拟.     

燃气流温度场不均匀性的影响

2005年6月号报道，由燃气流温度场不均匀性引起的热应力和腐蚀增加将导致燃气轮机叶片的加速破坏。 燃气轮机内的燃气流温度场通常具有径向和周向的不均匀性，与高压涡轮前的平均值比较，温度还可以提高约60～80℃。当在燃气不包含腐蚀性杂质的良好条件下，燃气温度的提高反映在第一级导向器中产生的热应力大小上。     

CFD在涡轮排气管增压器流场分析中的应用

本文借助三维数值模拟软件Numeca,建立了涡轮排气管增压器涡轮机的网格模型,对涡轮排气管增压器(即增压器与排气管集成)的涡轮及排气歧管内部流场分布情况进行了稳态模拟.结果表明:涡轮排气管各进出口的总压差分布不均,以2#进口进气时总压损失最大,此外,对涡轮内部流场及温度场也进行了分析,流场及温度场整体分布比较均匀,流场局部还存在一定的改善空间.可见,CFD技术对于优化涡轮增压器涡轮及排气管的设计,改善增压器性能具有很好的指导意义.     

具有温度场的冷却叶片振动特性计算方法研究

根据稳态热传导的相关理论,建立了透平冷却叶片温度场和热应力场的四面体三维有限元分析模型和方法,并在此基础上建立了透平冷却叶片振动特性三维有限元分析方法,开发了相关计算软件。对某航空发动机透平高压第1级冷却叶片在不同工作条件下的振动特性进行了计算分析,同时研究了热应力、温度场、转速等对叶片振动特性的影响,表明本文中所建立模型和方法是科学、合理和精确的,为开展透平冷却叶片的设计和振动安全性评价奠定了基础。     

燃气轮机涡轮后机匣温度场及应力分析

对某型燃气轮机涡轮后机匣加强筋发生断裂的事故进行了温度场和热应力的有限元分析计算,计算表明,涡轮后机匣表面突遇过冷而产生的巨大温度应力是造成加强筋断裂的根本原因。本文还对涡轮后机匣表面安装隔热附件后的情况进行了分析计算,计算表明,在遇到温度发生突变的不利情况下,隔热附件对涡轮后机匣能起到有效的保护作用。     

Effect of air flow rate distribution and flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration

This study investigates the effect of non-uniform distribution of the air inlet flow rate and change of air flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration. This study considers three patterns of air inlet flow rate in the transverse direction of each stack, and five patterns of air inlet flow rate in the stacking direction. The software package for simulation is reliable through an accuracy comparison, and it analyzes the current density, temperature, and thermal stress distribution of a SOFC stack with 20 layers. The results show that the progressively increasing profile of the air inlet flow rate along the x direction drops the cell thermal stress of a SOFC unit. Moreover, the non-uniform profile of air inlet flow rate in the stacking direction affects the position of the region with high thermal stress of the SOFC stack, and changing flow direction of the air obviously drops down the thermal stress without affecting the power generation of the SOFC stack.     

Simplified Thermoelastoplastic Models for Determination of Global and Local Stress in Coke Drums

Coke drums as major pressure vessels in delayed coking process experience cyclic thermal and mechanical loading during operation. The elastic-plastic behavior of coke drums including global and local (hot and cold spot) stress distribution has been analyzed using finite element analysis (FEA) method in our previous study. Here, instead of using FEA simulations, simplified theoretical models (STM) for global and local stress determination are developed. The global stress model is developed based on a single cladded shell element with temperature and pressure loading cycle. The local stress model is built on an axisymmetric circular cladded plate experiencing a non-uniform temperature distribution history. With the same input data, stress and strain values estimated by the STM are consistent with those from the FEA. An ease-of-use software package with built-in STMs is developed. It is the objective of this paper to show that STM can be a very time- and cost-saving analysis tool for general industrial users compared to professional commercial FEA software.     

高温太阳能吸热管在非均匀热流下的温度研究及结构优化

对腔式管状集热器在非均匀受热条件下进行温度场和热应力场的模拟.研究发现周向温差的不同造成吸热管的热变形分布不同,且吸热管后半段热变形最大;同时,太阳能辐射量随时间变化导致热流密度和吸热管壁面上的周向温差都在发生变化.鉴于此,分别从腔式集热器吸热管的结构、工作介质物性等方面入手以解决非均匀热流带来的形变问题.通过改变吸热...     

The effect of a nearby circular thermal inclusion on the irregular shape of a coated inhomogeneity with internal uniform hydrostatic thermal stresses

We show that under a uniform temperature change, a uniform hydrostatic residual thermal stress state can still be maintained inside a coated inhomogeneity of irregular shape despite its interaction with a nearby circular thermal inclusion. Our analysis indicates that the internal uniform hydrostatic thermal stress field inside the inhomogeneity, the constant mean stress within the coating and the constant hoop stress along the inhomogeneity-coating interface on the coating side are unaffected by the existence of the nearby circular thermal inclusion. In contrast, the irregular shape of the coated inhomogeneity is attributed solely to the presence of the circular thermal inclusion.     

Effect of inlet flow maldistribution on the thermal and electrical performance of a molten carbonate fuel cell unit

This study investigates the temperature and current density distributions in a molten carbonate fuel cell unit when the inlet flows of the anode gas and the cathode gas are mal-distributed in eight patterns. The two-dimensional simultaneous partial differential equations of mass, energy and electrochemistry are solved numerically. The results indicate that the maldistribution of anode and cathode gases dominates the current density field and the cell temperature field, respectively. Moreover, the non-uniform inlet flow slightly affects the mean temperature and mean current density, but worsens the distribution of temperature and current density for most maldistribution patterns. According to the results, the variations of the cell temperature in Pattern G and the current density in Pattern D are 12% and 37% greater than those in the uniform pattern when the deviation of the non-uniform profile is 0.25. Consequently, the effect of non-uniform inlet flow on the temperature and current density distribution on the cell plane is evident, and cannot be neglected.     

进口畸变下涡流发生器对压气机流场的影响

为研究进口总压畸变条件下涡流发生器对压气机流场的影响,建立单级轴流压气机模型,计算和分析了不同工况下的压气机内部流场.计算结果显示:在进口畸变条件下,压气机流场恶化,性能降低;使用涡流发生器后,可以有效改善静叶叶根附近的流场,控制叶片尾缘分离,降低沿叶高方向的压力波动,从而削弱进口畸变对效率的负面影响,改善出口压力场,...     

300MW直流炉顶棚进口集箱引出管系的改进

由于炉膛燃烧不理想导致水冷壁出口管的热偏差,使进入顶棚进口集箱的引入管的工质产生了较大的温差。这种热偏差在顶棚入口集箱形成了轴向壁温差,使顶棚入口集箱引出管座承受了附加的超过其工作温度下许用应力的热膨胀载荷,从而使刚度较大的集箱上层接管产生了较大的附加弯曲应力,最终导致了上层接管根部的永久性变形和角焊缝裂纹。分析这种应力产生的原因,在实际中对顶棚进口集箱引出管上层接管结构进行了改进,在运行中收到了很好的效果。     

On Effectiveness and Entropy Generation in Heat Exchanger

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