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1.
超临界机组高温合金管氧化膜剥落问题是困扰机组安全与经济运行的难题,严重制约了机组蒸汽参数和效率的提高。特别是,在超临界机组采用给水加氧处理方式(OT)后,奥氏体不锈钢管内壁氧化膜大面积剥落事故屡见不鲜,尤以TP347H合金管为甚。本文总结了近年来国内外针对超临界机组合金管氧化膜研究的进展及相关成果,首先介绍了超临界蒸汽环境中合金管氧化机理和原子迁移机制,综述了铁素体和奥氏体合金表面氧化膜的形貌特征,分析了蒸汽溶氧对氧化膜生长速率、形貌和缺陷的影响。氧化膜完整性是决定合金抗腐蚀性能的重要因素,但在机组运行过程中氧化膜应力破坏了氧化膜完整性。进一步总结了国内外氧化膜应力和剥落研究的数值分析及实验研究情况,为我国超临界机组氧化膜剥落故障诊断研究提供参考。 相似文献
2.
针对传统图像分割算法难以分割噪声污染严重的混凝土坝面细小裂缝图片的问题,结合大津阈值算法和区域生长算法提出一种新的裂缝分割算法。该算法通过一个滑动的窗口遍历整幅灰度图并计算窗口内的局部大津阈值,遍历过程中将所有灰度值在局部阈值以上的窗口中心像素点作为区域生长种子点,设计生长阈值,生长完成后得到分割结果。运用该算法、基于全局的大津阈值等经典分割算法对四幅存在光照不均、污渍覆盖等噪声污染的裂缝图片进行分割。结果表明,所提算法的分割结果中背景噪声最少,误差最小。通过连通域分析去除剩余的背景噪声,可实现对裂缝的精确识别分割,为自动化检测坝面裂缝奠定基础。 相似文献
3.
Guishang Pei Junyi Xiang Qingyun Huang Xuewei Lv 《Journal of the American Ceramic Society》2022,105(10):6359-6369
A double pyrovanadate CaMgV2O7 sample was synthesized via a facile solid-state route under an air atmosphere. The nonequilibrium formation pathways of the CaMgV2O7 were investigated via powder X-ray diffraction. A multistep reactions path (metavanadates–pyrovanadates–double pyrovanadate CaMgV2O7) was proposed to describe the formation of the CaMgV2O7 considering the thermodynamic and kinetic factors. The cell unit parameters of the CaMgV2O7 sample indicated the crystallization according to a monoclinic system with space group P12/c1(14), and the lattice parameters of a = 6.756 Å, b = 14.495 Å, c = 11.253 Å, β = 99.12, and V = 108.806 Å3. X-ray photoelectron spectroscopy also confirmed the +5 oxidation state vanadium in CaMgV2O7. The endothermic effects at 1033 and 1143 K were related to the incongruent melting and liquidus temperatures of CaMgV2O7, respectively. The comprehensive thermodynamic properties of CaMgV2O7 were established in both low- and high-temperature regions, utilizing a physical property measurement system and multi-high-temperature calorimetry (96 lines). The heat capacity (200 J mol K−1) and entropy (198 J mol K−1) at 298.15 K were computed based on the low-temperature heat capacity values, and the enthalpy of formation at 298.15 K was also estimated. The fitted high-temperature capacity can be used to obtain the changes in the enthalpy, entropy, and Gibbs free energy. This study is part of building a reliable thermodynamic database of the CaO–MgO–V2O5 system. 相似文献
4.
为进一步掌握中国石油和天然气探明地质储量增长趋势,分析了2010—2019年中国新增石油和天然气探明地质储量分布和变化特征。结果表明:2010—2019年,中国新增石油探明地质储量主要分布在鄂尔多斯盆地、渤海湾盆地、准噶尔盆地等地区,以中浅层—中深层为主;新增天然气探明地质储量主要分布在鄂尔多斯盆地、四川盆地、塔里木盆地、东海陆架盆地等地区,以中深层—超深层为主。石油和天然气储量品质变差,丰度变低,埋深变大。中国新增油气探明储量的增长,主要集中在岩性地层油气藏、非常规油气藏、深层油气藏等领域。 相似文献
5.
设计了一种基于阿基米德螺线的新型螺旋光子晶体光纤,该光纤以二氧化硅为基底材料,包层由24个螺旋臂组成,每个螺旋臂包含11个小空气孔,纤芯设有大空气孔,包层与纤芯中间的环形区域用于传输轨道角动量模式。该结构在1300~1800 nm波段上可支持22种轨道角动量模式稳定传输,在1550 nm波长下,有效折射率差最高可达2.89×10^(-3),色散系数最低可达66.4 ps/(nm·km),非线性系数最低可达2.17 W^(-1)·km^(-1),且1500~1600 nm波段上的色散值变化均小于15.15 ps/(nm·km)。此螺旋光子晶体光纤不仅结构简单,且具有低非线性、色散平坦的性能,为螺旋光子晶体光纤的设计提供了思路。 相似文献
6.
7.
Dong Yang Yuanyuan Zhang Xuping Wang Qian Li Jing-Feng Li 《Journal of the American Ceramic Society》2022,105(9):5555-5561
Similar to the canonical antiferroelectric (AFE) compound PbZrO3 in Pb(Zr,Ti)O3 solid-solutions, the presence of double hysteresis loops and that of electric field–induced phase transitions are important characteristics of NaNbO3 AFE materials; yet the phase transition behavior in the latter system is typically irreversible with the related mechanisms not fully understood. Here, we explore the phase transition mechanism of ferroelectric and AFE phases in NaNbO3 based on measurements of single crystals with different directions in conjunction with density-functional theory (DFT) calculations. The tilting and distortion behaviors of the [NbO6] octahedra are explained by DFT, and the ion displacement in the lattice is traced. The tilting and distortion behaviors of the [NbO6] octahedra with different orientations are compared. We confirm that the tilt and distortion of the [NbO6] octahedra along the [1 1 1] direction is the main reason to improve the stability of AFE phase. This conclusion is verified by the experimental characterizations of large-size NaNbO3 single crystals successfully obtained in this study. 相似文献
8.
《Journal of the European Ceramic Society》2022,42(14):6391-6403
We propose a multi-physics numerical model for a self-healing ceramic matrix mini-composite under tensile load. Crack averaged PDEs are proposed for the transport of oxygen and of all the chemical species involved in the healing process and studied in the dimensionless form to perform the most appropriate discretization choices concerning time integration, and boundary conditions. Concerning the fibres’ degradation, a slow crack growth model explicitly dependent on the environmental parameters is calibrated using a particular exact solution and integrated numerically in the general case. The tow failure results from the statistical distribution of the fibres’ initial strength, the slow crack growth kinetics, and the load transfer following fibres breakage. The lifetime prediction capabilities of the model, as well as the effect of temperature, spatial variation of the statistical distribution of fibres strength, and applied load, are investigated highlighting the influence of the diffusion/reaction processes (healing) on the fibre breakage scenarios. 相似文献
9.
根据涠洲10-3单点的结构特点,提出对其采用整体拆除的拆除思路。针对该单点整体吊装需求,借鉴钢桩吊装方案创新性地设计吊桩器吊装方案,借鉴隔水套管吊装方案创新性地设计套筒镗孔吊装方案。此外,还分别开展调平吊耳吊装方案、盲板吊装方案和吊耳吊装方案等3种吊装方案设计。通过对上述5种吊装方案的技术可行性分析,在综合考虑项目多方面因素后,涠洲10-3单点拆除项目最终选用吊耳吊装方案。在吊耳吊装方案应用实例中,分析吊点板式吊耳安装在套筒外侧的原因,论述所选用的吊点板式吊耳结构形式及其采用环形筋板的优点,并通过对该单点整体吊装强度的有限元分析,证明选用吊耳吊装方案设计的可行性。 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(66):28585-28604
Hydrogen transportation by pipelines gradually becomes a critical engineering route in the worldwide adaptation of hydrogen as a form of clean energy. However, due to the hydrogen embrittlement effect, the compatibility of linepipe steels and associated welds with hydrogen is a major concern when designing hydrogen-carrying pipelines. When hydrogen enters the steels, their ductility, fracture resistance, and fatigue properties can be adversely altered. This paper reviews the status of several demonstration projects for natural gas-hydrogen blending and pure hydrogen transportation, the pipeline materials used and their operating parameters. This paper also compares the current standards of materials specifications for hydrogen pipeline systems from different parts of the world. The hydrogen compatibility and tolerance of varying grades of linepipe steels and the relevant testing methods for assessing the compatibility are then discussed, and the conservatism or the inadequacies of the test conditions of the current standards are pointed out for future improvement. 相似文献