氦质谱技术在大亚湾核电站凝汽器管束泄漏检测中的应用

在电站凝汽器的故障中，管束泄漏占有相当大的比例，作者根据大亚湾核电站１号机凝汽器在商业运行前后数次管束检漏的经验，介绍氦质谱技术在电站凝汽器管束检漏中的实际应用。实践表明，氦质谱技术的特点是快速、精确、可靠。特别是对于拥有多台机组的大型电站，应用氦质谱技术可以大大提高凝汽器管束的检漏效率。     

氦质谱检漏技术在火电厂中的应用

针对火电厂中真空系统和发电机氢冷系统的泄漏问题，应用氦质谱检漏技术发现系统泄漏点，为检修提供依据，保证机组的安全、经济运行，从而取得良好的节能效益。文中还指出了氦质谱检漏仪在运用中应注意问题。     

大气比对法在民核取证模拟件氦质谱检漏试验中的应用

本文主要介绍了一种新型的氦质谱检漏方法——大气比对法在民核取证模拟件氦质谱检漏试验中的应用。此种方法既具有氦质谱探测器探头技术定位快速、准确的优点,同时又可以通过累积法实现精确定量,而且通过大气比对减少了参考漏孔的使用,缩短了校准时间。     

一起凝汽器漏真空案例分析及处理

针对火电厂中真空系统的泄漏问题,应用氦质谱检漏技术、结合现场实际状况,从凝汽器真空系统的运行、设计、各种参数等方面,通过采取运行方式调整、外部查漏、数据分析、系统停运等治理对策,解决了某发电公司2号机组凝汽器真空系统泄漏、严密性偏大等问题,提高了机组运行的安全性、经济性。     

氦质谱检漏技术及其在热电厂真空系统中的应用

针对机组真空严密性差的问题 ,采用氦质谱检漏技术查寻真空系统的可疑漏点 ,并进行了相应的消漏措施 ,从而收到良好的节能效益     

汽轮机真空系统的氦质谱检漏技术应用

汽轮机真空系统的严密性直接影响着机组的和安全运行。提出了应用氦质谱检漏技术进行凝汽机组真空的检漏方法，并通过多台大型机组具空系统的检漏实践取得了理想的实效。     

管子-管板焊缝氦质谱泄漏试验简介

管子-管板焊缝采用护罩技术进行氦质谱泄漏试验所需的设备、系统的连接、试验的操作流程和泄漏率的计算方法。本文是典型的护罩技术泄漏试验实例。     

Differential electrochemical mass spectroscopy: A pivotal technology for investigating lithium-ion batteries

锂离子电池的安全性问题在很大程度上限制了其在纯电动汽车、规模储能等领域的广泛应用。电池材料|电解质界面副反应所产生的可燃性气体是锂离子电池安全隐患的首要原因。微分电化学质谱是解析锂离子电池产气副反应机制的强有力研究技术。本文综述了微分电化学质谱的发展历程、工作原理、技术要点及其在锂离子电池安全性研究中的应用,并展望了微分电化学质谱在储能领域的机遇、挑战和策略。     

生物柴油若干应用技术问题及对策

在介绍生物柴油基本组成和特性的基础上,对生物柴油应用中的若干技术问题进行了分析,就解决生物柴油应用中的技术问题提出了对策.     

用于酸性析氧反应研究的原位表征技术

质子交换膜(PEM)水电解的阳极催化剂需要耐受强酸性环境以及析氧反应(OER)条件下的高氧化电位.为了加深对酸性介质中OER过程的理解以开发具有更好稳定性与更高活性的电催化剂,研究和发展原位表征技术显得尤为重要.该综述介绍了几种用于酸性OER研究的原位表征技术,包括:原位X射线光电子能谱技术、原位X射线吸收谱技术、原位X射线衍射/散射技术、原位电化学红外技术、原位电化学拉曼技术、原位电感耦合等离子体-质谱技术、微分电化学质谱/在线电化学质谱技术、电化学石英微晶天平技术.重点讨论了这些技术的原位装置设计以及它们在酸性OER研究领域的具体应用.最后总结了这些技术的特征,并指出用于酸性OER的原位表征技术的发展之有待解决的问题,即新技术的研发与原位技术间的联用、原位装置的改进及时空分辨率的提高.     

基于弯曲叶片的氦气轴流压气机优化设计

针对高负荷氦气压气机中角区分离、叶顶泄漏严重带来的效率损失问题,以单级氦气压缩机为研究对象,利用CFD方法,分析了不同弯曲角度下氦气压气机内部的角区损失和叶顶泄漏损失,并优化了现有五级轴流氦气压气机。结果表明：叶片正弯会增加端区处的静压,减少角区分离,进而降低角区损失;对动叶而言,在设计攻角下正弯也会增加前缘损失;动叶叶顶反弯使泄漏流远离下一个叶片的压力面,而合适的反弯角度可以降低叶顶泄漏量;选取合适的弯曲角度使五级轴流压气机设计点效率提高1.85%。     

Experimental investigation on subcooling of liquid hydrogen by helium gas injection through evacuation

Subcooling is the process of bringing down the temperature of liquids lower than that of the boiling point of the corresponding vapor pressure. The performance of subcooling of cryogenic liquids mainly depends on the heat-inleak of the system, the helium injection mass flow rate, helium injection temperature, and helium injection nozzle pattern. This paper presents an alternative method, by making use of the least heat in the leakage of the liquid hydrogen storage container, which is quite possible because containers with excellent thermal insulation are commercially available nowadays. The process involved is rapid evacuation through gas ejectors, thus reducing the effect of temperature. The advantage and the process of evacuation leading to subcooling in a unique manner are the objective of this article. The experimental results are discussed in comparison with the thermophysical process involved in the subcooling operation. A comparative study is also carried out with the theoretical heat exchange process in which helium is used as a medium for the economy of the stated process. It is stated that the current process of subcooling through evacuation is superior to the conventional heat exchange process.     

Natural hydrogen and blend gas: a dynamic model of accumulation

Natural hydrogen is accumulating in the form of “blend gases”, with the association mainly of methane, nitrogen, and helium. The extreme variation of proportion between these four gas compounds is explained through a model of dynamic accumulation, where some compounds as helium are chemically inert in the reservoir, nitrogen almost inert, methane is altered into CO₂, and hydrogen is severely altered mainly in protons, and in a smaller degree in methane. All the gas compounds may also leak out of the reservoir, either through advection without any chemical fractionation, or through solubilization in water and diffusion, inducing a variable composition for the residual gas remaining in the accumulation.The model can explain the concomitance of high concentration of helium, clearly accumulated through geological time, with hydrogen, supposedly renewable in human time scales. With the best choice of parameters for the model, the ages of hydrogen accumulation known in the World are small, the hydrogen being diluted more and more in nitrogen and methane through geological time. Diffusive leakage through water appears negligeable compared to advective leakage and compared to hydrogen reactivity in the reservoir. The example of the hydrogen field of Bourakébougou would present an age of 500 years according to the model. Diffusive leakage through water solubilization has a small effect on gas composition. Advective leakage, even not fractionating, has a significant effect on accumulated gas composition, because of its mixing with active deep fluxes. During future production of natural hydrogen accumulations, it is predicted that the proportion of hydrogen should increase during production time, whereas the helium and nitrogen concentrations should decrease.     

Effect of helium xenon as working fluid on the compressor of power conversion unit of closed Brayton cycle HTGR power plant

Helium is one of the best coolants in closed Brayton cycle power plants as it has superior transport properties; however, the main shortcoming is its compression, which is very difficult to achieve. It leads to a higher number of compressor stages, means bigger mass and big size of the compressor, which create dynamic issues in a compressor of the power conversion unit. All the helium compressors ever constructed have a very high number of stages such as Oberhausen II type 50 MW and JAEA 300 MW, high and low pressure compressors have 25 and 35 stages respectively. In this paper thermodynamic traits of mixing helium with an inert gas xenon were presented. Helium xenon mixture up to the molecular weight of <40 g/mol not only increases heat transfer coefficient but also significantly increase the loading of the compressor. A 7% higher heat transfer coefficient can be achieved with 15 g/mol helium xenon mixture. Therefore, a 15 g/mol helium xenon mixture compressor was designed and its performance analysis conducted using Ansys CFX. It is found that the use of 15 g/mol helium xenon mixture greatly increases the blade loading, which gives a higher total outlet pressure ratio. The obtained results indicated that only 18.75% stages of helium xenon compressor can generate requisite outlet pressure. Hence, the use of helium xenon over pure helium is advantageous as it reduces size and cost of turbo compressor of HTGR power plant.     

Effect of helium xenon as working fluid on centrifugal compressor of power conversion unit of closed Brayton cycle power plant

Closed Brayton cycle (CBC) having single-shaft, centrifugal type compressor is considered as an efficient energy-conversion option associated for gas-cooled reactor (GCR) heat source. In terrestrial power plants and space power systems noble gases are considered as an efficient working fluid for most of the GCR's and CBC engines. The effectiveness of various noble gases as working fluid in closed cycle power plants for the power conversion units is of imperative concern. Although pure helium is relatively difficult to compress nonetheless it is measured as the best coolants for closed Brayton cycle power plants due to its better transport properties. Due to compression properties, its use resulted in the requirement of more mass, bigger size, higher cost and relatively more dynamic problems of rotatory machines in energy conversion system. The mixture of xenon with helium up to a molecular weight of <40 g/mol resulted in an increase of the coefficient of heat transfer as well as the significant increase in the loading of the compressor. Therefore, performance analysis is conducted for a novel design of helium xenon centrifugal compressor. The performance analysis is conducted with different molecular weight mixtures of helium xenon using similarity criteria. It is concluded that the use of helium xenon 40 g/mol is the optimum choice for space applications and 15 g/mol for closed Brayton cycle terrestrial power plants.     

氦气透平压气机组合弹性环密封试验研究

氦气透平压气机采用间冷回热方式的闭式循环,因此高低压压气机以及涡轮进排气口处的密封与外层压力壳间就形成了不同压力的腔室,针对其各不同温度和压力的腔室采用组合弹性环密封.为验证组合弹性环的密封效果,设计了密封试验器和与机组上的组合弹性环完全一致的密封试验件,并在密封试验台上分别采用氦气工质和空气工质进行了试验对比.试验结果表明,组合弹性环具有良好的密封效果,在低压压气机出口进口、高压压气机出口进口以及高压压气机出口涡轮出口3处密封的泄漏分别占设计流量的0.0322‰、0.1035‰、0.1282‰,与空气介质相比,当封前压力为0.6～1.0 MPa时,氦气的泄漏约为空气泄漏的2倍,当封前压力较低时(0.1～0.2 MPa),氦气与空气的泄漏比较接近.     

A reduced-scale experimental study of dispersion characteristics of hydrogen leakage in an underground parking garage

A medium-scale model (1/10) of an underground parking garage is designed and built to study the characteristics of the release and dispersion of hydrogen leaked from hydrogen fuel cell vehicles (HFCVs) in underground garages. Helium is used in place of hydrogen for safety reasons. The helium release experiments are conducted and the variations in helium concentrations at different locations and times in the garage model are obtained. The influence mechanisms of the leakage flow rate and nozzle diameter on the spatial and temporal distributions of the helium concentration are revealed. The experimental results show that the initial release rate of helium is the key factor affecting the distribution of helium concentrations. Both leakage flow rate and nozzle diameter have a significant influence on helium concentrations by affecting the initial release rate. If the release time is long enough, the helium concentrations will experience three stages during release, namely, rapid growth, slow growth and relatively stable. Furthermore, the beams of the garage can reduce the area on the ceiling where the hydrogen concentration exceeds the lower flammable limit (LFL). On the other hand, the beams can make it easier for local hydrogen concentrations to reach the LFL. This work can provide theoretical support for the design and construction of underground parking garages and the arrangement of hydrogen detectors.     

氦气流动特性的初步研究

使用计算流体力学方法,模拟了圆管内流动、圆柱绕流、孤立翼型、叶栅当量扩压器、平面叶栅,在氦气和空气两种工质下典型流场的流动。结果发现:在低马赫数下,雷诺数相同时,氦气和空气流场具有较大的相似性;氦气的运动粘性系数较大,其附面层发展较快,流速大,容易发生边界层分离;与空气相比,氦气总压损失系数大。由此得到启示:对于高温气冷堆氦气压气机的设计,要充分考虑氦气雷诺数小、流速大、容易发生分离的流动特性。并且给出了氦气流动特性的基本数据,可供进一步研究和工程使用。     

Simulation of gas species and temperature separation in the counter-flow Ranque–Hilsch vortex tube using the large eddy simulation technique

A computational fluid dynamic model is used to predict the species and temperature separation within a counter flow Ranque–Hilsch vortex tube. The large eddy simulation (LES) technique was employed for predicting the gas flow and temperature fields and the species mass fractions (nitrogen and helium) in the vortex tube. A vortex tube with a circumferential inlet stream of nitrogen–helium mixture and an axial (cold) outlet stream and a circumferential (hot) outlet stream was considered. The temporal evolutions of the axial, radial and azimuthal components of the velocity along with the temperature, pressure and mass density and species concentration fields within the vortex tube are simulated. Even though a large temperature separation was observed, only a very minimal gas separation occurred due to diffusion effects. Correlations between the fluctuating components of velocity, temperature and species mass fraction were calculated to understand the separation mechanism. The inner core flow was found to have large values of eddy heat flux and Reynold’s stresses. Simulations were carried out for varying amounts of cold outlet mass flow rates. Performance curves (temperature separation/gas separation versus cold outlet mass fraction) were obtained for a specific vortex tube with a given inlet mass flow rate.