Vacuum chamber suppression of gas-explosion propagation in a tunnel

To control and reduce the harm of a gas explosion, a new method is proposed for suppressing gas-explosion propagation in a tunnel by using a vacuum chamber. We studied the suppression effect on gas explosions by placing a vacuum chamber at dif-ferent positions along the tunnel. The results indicate that: 1) the vacuum chamber can absorb the explosion wave and explosion energy as much as possible at the beginning of the gas explosion, and; 2) when the vacuum chamber is used the closer it is to the ignition source the more significant the suppression effect. In addition, by using the vacuum chamber: 1) the flame propagation velocity decreases from ultrasonic to subsonic; 2) the flame propagation distance is remarkably shortened; 3) the maximum peak value of overpressure (pm) decreases from 0.34 to 0.17 MPa or less, and; 4) the impulse of the blast wave (I) decreases from 20 to 8 kPa·s or less.

Analysis of vacuum chamber suppressing gas explosion

In order to suppress the harm of gas explosion,the current study researched on the body of vacuum chamber.The previous studies verifed that it could obviously lower the explosion overpressure by reasonably arranging vacuum chamber on pipe.That is to say,the vacuum chamber has the effect of absorbing wave and energy.To further deeply analyze the vacuum chamber suppressing gas explosion,this research designed the L-type pipe of gas explosion,and compared the experimental results of gas explosion with vacuum chamber and without vacuum chamber.Besides,using the gas chromatograph,this study also investigated the gas compositions in the pipe before and after explosion.The results show that:(1)without vacuum chamber,the maximum value of explosion overpressure is 0.22 MPa,with60 ms duration,and after explosion,the concentration of oxygen drops to 12.07%,but the concentration of carbon monoxide increases to 4392.3 10à6,and the concentration of carbon dioxide goes up to7.848%,which can make the persons in danger suffocate and die;(2)with vacuum chamber,explosion overpressure drops to 0.18 MPa,with 20 ms duration or less,and after explosion,the concentration of oxygen still remains 12.07%,but the concentration of methane is 7.83%,however the concentration of carbon monoxide is only 727.24 10à6,and the concentration of carbon dioxide is only 1.219%,at the this moment the concentration ratio of toxic gas drops by more than 83%in comparison to be that without vacuum chamber.Consequently,the vacuum chamber can guarantee that most methane does not take part in chemical reaction,and timely quenches the deflagration reaction of gas and oxygen.Because of the two points mentioned above,it reduces the explosion energy,and lowers that the overpressure of blast wave impacts and damages on the persons and facilities,and also decreases the consumption of oxygen and the production of the toxic gas.Therefore,it is safe to conclude that the vacuum chamber not only absorbs wave and energy,but also prevents and suppresses explosion.

New Materials for Vacuum Chambers in High Energy Physics

Vacuum chambers must fulfil ultra-high vacuum requirements while withstanding thermo-mechanical loads. This is particularly true in high energy particle accelerator where interactions of particles with matter may induce thermal load, material activation, background… The choice of the material of the vacuum chamber is crucial for the final application. Metals such as stainless steel, copper and aluminium are usually used. Even with outstanding mechanical and physical properties, beryllium is used for very specific applications because of its cost and toxicity.Ceramics such as alumina are usually used for fast magnet vacuum chambers. With the next generation of high energy physics accelerator generation such as CLIC and TLEP, the problematic of high cyclic thermal load induced by synchrotron radiation is raised. This paper aims at defining some figures of merit of different materials with respect to several load scenarios and presents briefly their vacuum compatibility.

Numerical Analysis on Wood Pyrolysis in Pre-Vacuum Chamber

In the previous experimental work, a new technology system for wood pyrolysis was developed to aim at mitigating climate change, global warming, and energy crisis as well as enhancing low electrification in rural areas in developing countries. The new technology system equipped with a pre-vacuum chamber requires low cost and less maintenance. However, large wood pyrolysis in the pre-vacuum chamber is rather complicated. To obtain a good understanding of the previous experimental results, a numerical analysis taking account of heat-mass transfer and chemical reaction is carried out. Two-step general reaction model is proposed for the numerical analysis. The first stage is volatile and char formation from the wood pieces and the second state is decomposition of the volatile to five species including vapor of tar. In this analysis, chemical formulae of the volatile and the tar are successfully identified hypothetically. The results obtained by this numerical analysis can explain the experimental results reasonably and provide useful information about time evolution of volatile formation, temperature change in pre-vacuum chamber with time, and species mole concentration decomposed from the volatile.

Wood Pyrolysis in Pre-Vacuum Chamber

Climate change, global warming, and energy crisis are critical issues to be solved urgently in a global framework. Alternative energy and renewable energy technologies must be quickly developed to be substituted for fossil fuels like oil, gases, and coal. USA, UE, and Japan invested huge budgets to develop biomass renewable energy technology. Their target is to develop a commercial base large-scaled plant. On the other hand, in developing countries, especially in rural areas, people who can access electricity is still less than 70%, To decelerate or prevent global warming and improve electrification in rural areas, a new technology for wood pyrolysis, which requires low manufacturing cost and less maintenance, and of which gases are directly applicable to the gas engine generator, is developed in a laboratory scale. This paper reports the performance of this new plant and effects of several parameters on the performance. It is concluded that the new technology is quite feasible in rural areas, and upgrading of the plant is easily possible.

Effects of Secondary Chamber on Gas Yield by Pre-Vacuum Chamber Pyrolysis of Rubber Wood

Global warming awareness criticizes further usage of fossil fuels and insists promotion of renewable energy usage. Additionally, many people in rural areas of developing countries cannot access electricity. To solve this sort of energy crisis including global warming, current authors developed a proto-type of a pyrolysis plant equipped with a prevacuum chamber, which can be used to produce combustible gases for an engine generator in rural areas where people cannot access electricity. The plant is simple and easily maintained in consideration of special conditions that a rural area can receive very few maintenance service, technical assistance, and supply of spare parts. However, gas yield obtained by the proto-type of plant was around 20 wt% of feedstock. One way to enhance gas yield from this proto-type of plant is to utilize reaction of secondary tar cracking. This research work aims to examine possibility of gas yield enhancement keeping a simple structure of the proto-type of plant and using a simple technique of secondary tar cracking. Two tar cracking methods are examined: one is homogeneous tar cracking and the other is heterogeneous tar cracking using catalysis. In the homogeneous tar cracking, pyrolysis gases must be heated up to 650oC to 700oC and in the heterogeneous tar cracking, wood char is used as catalysis, because wood char is byproduct of pyrolysis. It is concluded that the homogeneous tar cracking is quite unlikely in the secondary chamber, but on the other hand, heterogeneous tar cracking using wood char can produce 30 wt% of gas yield from 1 kg of feedstock.

Measurement and Analysis of Movement of BPM Vacuum Chamber for HLS

The beam horizontal orbit at Hefei Light Source(HLS)was drifting all along while the storage ring was operating.To study this phenomenon,the displacement and the temperature variation of the BPM chamber were measured.By analyzing the measurement results,the main reason that explained the drifting phenomenon was found. The vacuum chamber following the dipole magnets was heated by the synchrotron light,which caused the increasing of the chamber surface temperature.The variation of the chamber temperature was the main reason why the BPM chamber held the horizontal displacement.To suppress the orbit drifting,a compensation method of BPM movement was proposed and its experimental results were given.

Modeling of Liquid Level and Bubble Behavior in Vacuum Chamber of RH Process

In the Ruhrstahl-Heraeus （RH） refining process, liquid steel flow pattern in a ladle is controlled by the fluid flow behavior in the vacuum chamber. Potassium chloride solution and NaOH solution saturated with CO2 were respectively used as a tracer to investigate the liquid and gas flow behaviors in the vacuum chamber. Principal compo nent and comparative analysis were made to show the factors controlling mixing and circulation flow rate. The liquid level and bubble behavior in the vacuum chamber greatly affect fluid flow in RH process. Experiments were performed to investigate the effects of liquid steel level, gas flow rate, bubble residence time, and gas injection mode on mixing, decarburization, and void fraction. The results indicate that the mixing process can be divided into three regions： the flow rate affected zone, the concentration gradient-affected zone, and their combination. The liquid steel level in the vacuum chamber of 300 mm is a critical point in the decarburization transition. For liquid level lower than 300 mm, liquid steel circulation controls decarburization, while for liquid level higher than 300mm, bubble behavior is the main controlling factor. During the RH process, it is recommended to use the concentrated bubble injection mode for low gas flow rates and the uniform bubble injection mode for high gas flow rates.

Study of eddy current power loss in an RCS vacuum chamber

In a Rapid Cycling Synchrotron （RCS）, power loss due to an eddy current on the metal vacuum chamber would cause heating of the vacuum chamber. It is important to study the effect for estimating eddy current induced power loss and temperature growth. Analytical formulas for eddy current power loss for various types of vacuum chambers are derived for dipole and quadrupole repeetively. By using the prototype of dipole of CSNS/RCS, an experiment was done to test the analytical formula. The derived formulas were applied to calculating the eddy current power loss on some special structures of an RCS vacuum chamber.

Effects of water vapor in high vacuum chamber on the properties of HfO_2 films

The influence of water vapor content in high vacuum chamber during the coating process on physical properties of HfO2 films was investigated. Coatings were deposited on BK7 substrates by electron beam evaporation and photoelectric maximum control method. An in situ residual gas analyzer （RGA） was used to monitor the residual gas composition in the vacuum chamber. The optical properties, microstructure, absorption and laser-induced damage threshold （LIDT） of the samples were characterized by Lambda 900 spectrophotometer, X-ray diffraction （XRD）, surface thermal lensing （STL） technique and 1064-nm Qswitched pulsed laser at a pulse duration of 12 ns respectively. It was found that a cold trap is an effective equipment to suppress water vapor in the vacuum chamber during the pumping process, and the coatings deposited in the vacuum atmosphere with relatively low water vapor composition show higher refractive index and smaller grain size. Meanwhile, the higher LIDT value is corresponding to lower absorbance.

车灯反光镜真空镀铝层脱落形成机理及对策

文章先从真空镀铝的基本原理分析镀铝层脱落的形成机理,然后从结构设计、底涂、硅油、蒸发舟的参数、注塑件表面品质、外部环境等角度探讨真空镀铝层脱落的一系列影响因素和相关对策,并从在线检测和试验的角度,提出真空镀铝品质的评价方法,最后基于某一项目实践验证对策和评价方法的有效性。

高真空环境模拟卧式超长综合试验平台

文章设计了一套高真空环境模拟卧式超长综合试验平台,包括真空腔体、抽真空系统、热模拟系统、冷却水循环系统、控制及数据采集系统以及其他辅助保证系统等。该环境模拟系统主要是为全系统模拟真空环境试验提供条件保障,满足试验过程中关键技术指标的验证要求以及关键设备可以在清晰成像距离范围内实现对目标运动轨迹的标定,为后续项目研发和改进提供技术和测试数据支撑。

基于滑移流模型的真空容器内羽流流场数值仿真

预示真空容器内羽流的力、热分布规律是制定大型真空羽流试验方案、提升试验环境模拟有效性的关键前提之一。针对“嫦娥七号”飞跃器点火试验,利用考虑H_(2)O与CO_(2)吸附的滑移流计算流体力学(CFD)方法,对真空容器内羽流流场压力、温度及气体组分时空分布的初期变化进行了仿真计算。结果表明,流场整体温度与H_(2)O组分质量分数均随时间推移呈急剧上升后平稳下降趋势,而压力则随时间推移呈波动上升趋势。基于该结论提出了试验优化建议。该方法为真空容器内羽流流场仿真提供了新思路,可为后续相关试验方案设计提供支撑。

真空灭弧室内电弧形态演变研究

真空灭弧室内电弧形态演变会影响灭弧室内部各物理场的变化以及真空灭弧室的使用寿命。为了精确划分1个分闸周期内电弧形态的演变阶段并描述各阶段电弧形态特征,利用Labview平台的图像处理技术对高速相机采集到的电弧图像进行图像降噪、边缘加强处理,结合像素统计技术统计电弧上、下边缘像素点的坐标信息并计算电弧直径,采用阈值分割技术提取电弧纹理特征并统计电弧区域的像素个数。结果表明该方法可实现电弧形态特征的提取,提高了电弧演变各阶段时间划分的精度。该实验结果可作为后续动态仿真分析电弧烧蚀触头材料的数据支撑。

用于钙离子全光囚禁的离子囚禁装置研究

随着离子光钟技术的飞速发展,由离子光钟中用来囚禁离子的射频场带来的微运动效应对其性能的影响也越来越不可忽略。为彻底消除这一效应,提出了全光囚禁离子光钟的实验方案。针对这一实验方案,设计并搭建了用于钙离子全光囚禁的离子囚禁装置。该装置是采用刀片型离子阱设计,能够实现剩余力仅有10^(-20) N量级的高精度的杂散电场补偿;具备6 mm的通关孔径,很好满足了全光囚禁实验中偶极囚禁激光的通过需求;基于改良的螺旋谐振器设计搭建的射频系统能够实现在9.33(1)MHz较低射频频率下的稳定耦合;结合高达10^(-9) Pa的真空制备和装配导电玻窗的真空腔体,可以实现长时间的离子囚禁。为全光囚禁钙离子提供了实验基础,对光学囚禁离子光钟的实现具有重大意义。

BNCT02真空设计及仿真

BNCT02由两套加速器和5个治疗端组成,可实现2组癌症患者同时治疗。目前开工建设的是其中一套装置,由一台ECR离子源,一条低能传输线(LEBT),一台2.8 MeV射频四极加速器(RFQ),两条高能传输线(HEBT)、两个治疗端和一条临时调束线组成。文章首先介绍了BNCT02真空设计,利用Molflow软件计算了RFQ及HEBT不同状态下的压力分布,并与实测情况进行比对。然后,对HEBT区段异型真空盒形变、水冷真空盒温升进行模拟计算,并优化对应真空盒设计。目前整个装置已经稳定运行,真空系统满足设计要求。

基于氦气质谱法的动力电池包热管理模块密封性检测系统

根据动力电池包热管理模块密封性检测要求,提出一种基于氦气质谱法的动力电池包热管理模块密封性检测系统。为避免氦气泄露污染,先利用低氦进行大漏粗检,再利用氦气进行精检;通过氦气回收和氮气清扫等工艺,降低检测成本,提高检测可靠性;采用双真空箱交替工作模式,提高检测效率。经实验验证,最小检测漏率小于1.5×10^(-6)mbar·L/s,满足动力电池包热管理模块密封性检测要求。

电子束选区熔化真空箱体有限元分析与结构优化

为了保证电子束选区熔化设备真空箱体具有可靠的力学强度和合理的弹性变形量,对电子束选区熔化真空箱体开展有限元分析,根据箱体抽真空前后的弹性变形量,对原有箱体结构进行优化,最终提高产品的稳定性和经济性。

一起110kV变压器有载重瓦斯跳闸故障及分析

对某供电公司一起110kV变电站主变有载重瓦斯故障跳闸事故进行分析,通过现场变压器油气分析和电气试验,确定了有载开关的真空灭弧室应断未断是导致此次重瓦斯跳闸事故的原因。随后对有载开关吊芯进行解体检查,分析了真空灭弧室卡死的原因并还原了故障过程,最后提出了相应的预防措施。