Electrical resistance tomography coupled with differential pressure measurement to determine phase hold-ups in gas–liquid–solid outer loop bubble column

Radial variation of the gas hold-ups and mean hold-ups are investigated in a 90 mm outer loop bubble column using electrical resistance tomography (ERT) with two axial locations (Plane 1 and Plane 2). In all the experiments, air is used as the gas phase, tap water as liquid phase, and polypropylene particles as solid phase where the superficial gas velocity is varied from 0.02 to 0.25 m/s. The effect of operating conditions, solid concentration on mean hold-ups and radial gas hold-ups distribution is discussed. Gas hold-ups and solid hold-ups results using ERT are in very good agreement with conventional estimation and correlations obtained using pressure transmitter methods. Meanwhile, the results show that the gas hold-ups in the centre region increase constantly with an increase in the superficial gas velocity, namely there is a maximum hold-up at the centre of cross-section. But, solid hold-ups distribution is very homogeneous for high gas velocity. According to the visible image, the gas–liquid flow behaviours are obtained for gas–liquid–solid outer loop bubble column. Furthermore, the results also indicate that ERT is a very powerful tool for diagnosing the ‘inside’ flow behaviour of gas–liquid–solid three phase bubble column.     

氢气实际气体对螺旋槽干气密封性能的影响

干气密封常应用于较高的气体压力。在干气密封的研究、设计和应用过程中,一般将气体处理为理想气体。但高压作用下,气体行为明显不同于理想气体。以螺旋槽干气密封应用于氢气为例,采用氢气的实际气体方程对螺旋槽窄槽理论的气膜压力控制方程进行修正,并加以求解,获得了实际气体行为对干气密封的影响规律。结果表明,实际气体行为对密封的泄漏率有明显影响,而对端面气膜压力和端面开启力影响不大。     

将安全设计引入站点范围气体传输系统

气体产业和设备公司发展了许多不同的方式来确保气体传输的安全。本文介绍了气柜、具有净化机制的特殊源系统以及监控设备（包括警报器、阀关闭装置、限流器和气体检测器）。为了正确地认知何种危险会与气体维护相关,同时避免鲁莽所致的交叉使用（例如将氧化剂的系统误用于易燃物）,对于气瓶和设备的合理标记也同样重要。本文关注于作为一个站点范围内气体传输系统一部分的气体安全设备。有关的材质、选择标准、基本的注意事项以及其他问题都在下文关于安全和气体纯化的内容中予以讨论。     

基于有限差分法对不同润滑介质下静压气体轴颈轴承性能研究

利用有限差分方法编写一套可以用于分析动静压气体轴承性能的计算程序,并通过已有算例和试验验证本程序计算结果的可靠性。对不同润滑介质下静压轴颈轴承气体消耗量进行研究发现,不同分子量润滑介质下气体消耗量随偏心率变化表现出不同的变化规律,小分子润滑介质下气体消耗量与偏心率成正比,而大分子润滑介质下气体消耗量与偏心率成反比,并且此规律与节流小孔类型无关,小孔节流轴颈轴承气体消耗量大于环面节流类型轴颈轴承。相同供气压力和偏心率情况下,小分子润滑介质小孔节流轴颈轴承承载能力比环面节流类型轴承承载能力小,大分子润滑介质下正好相反。本程序方法为后来对俄罗斯油—气混合低温氦透平膨胀机气体轴承端改造奠定了理论基础。     

Pore-scale visualization of gas trapping in porous media by X-ray CT scanning

Entrapment of the non-wetting phase in porous media has been observed in a variety of fields such as petroleum engineering, geological storage of carbon dioxide, and remediation of ground water. We investigated gas trapping in porous media from a microscopic point of view. High-resolution, three-dimensional images of pore structure and trapped gas bubbles in Berea sandstones were obtained using a micro-focused X-ray CT scanner. We used vertical and horizontal Berea sandstone cores, 8 mm in diameter and 15 mm long. Based on the three-dimensional image analysis, the statistical distribution of the trapped gas volume was estimated. Trapped bubbles have a pore-network scale size and distribute over several pores. In the case of the vertical core, the porosity fluctuates along the flow direction due to the layered structure. The residual gas saturation also fluctuates with porosity along the flow direction. The higher gas saturation in porous layers at the end of gas injection results in a higher trapped gas saturation compared to dense layers. On the other hand, in dense layers the gas saturation at the end of gas injection is almost the same as residual gas saturation. Therefore, most of the gas injected into the dense layers would be trapped. In the case of the horizontal core, the gas saturation at the irreducible water condition is lower than that for the vertical core, because the injected gas selectively passes through the more permeable layers. However, the residual gas saturation is 29.2% for the horizontal core, which is comparable with that for the vertical core (30.9%). Finally, the effect of capillary number on stability of trapped gas bubbles has been estimated. Trapped gas bubbles are stable against the increased flow rate up to a capillary number of 1.0×10^?5.     

AN ALL-FIBER GAS SENSING SYSTEM USING HOLLOW-CORE PHOTONIC BANDGAP FIBER AS GAS CELL

An all-fiber compact gas sensing system using a hollow-core photonic bandgap fiber (HC-PBF) as a gas cell is proposed in this paper. Compared with the present reported microstructured optical-fiber gas cells, the HC-PBF gas cell proposed here has relatively lower transmission loss and much simpler construction. The total transmission loss through the HC-PBF gas cell is demonstrated experimentally to be as low as 1.5 dB and the time taken for gas to get into the 90-cm-cell, under the free diffusion condition, is approximately 11 min. Combining the HC-PBF gas cell with a tunable fiber laser, an all-fiber gas sensing system is developed. The properties of the proposed system are demonstrated experimentally by detection of carbon monoxide (CO) and acetylene (C₂H₂). Approximately linear relationships between the system responses and the concentrations of the detected gases are experimentally demonstrated. The minimal detectable concentration of CO of 300 ppm and C₂H₂ of 5 ppm are also achieved respectively by the experiments.     

示踪法测量气体流量的试验研究

以空气作为被测流体,以CO作为示踪气体,在直径为0.300m的90°弯曲管道内对示踪法测量气体流量进行了试验研究。结果表明,多点释放/多点取样比单点释放/单点取样时,取样点处示踪气体的浓度测量偏差小。释放点位于弯头上游7D～13D(D为管道直径)、取样点位于弯头下游10D～14D处,流量计算值(示踪法)与测量值(涡轮流量计)的相对误差在-2.15%～1.69%的范围内,释放点与取样点的位置越远,示踪法测量流量的相对误差越小。示踪气体的释放量需要与管道输送气体流量相匹配。对于含有脏污介质的大口径管道工业气体输送过程中的流量计,采用示踪法进行在线校准,是一种简单有效的校准方法。     

基于自聚焦透镜的吸收型光纤气体传感器气室设计

基于气体分子红外吸收光谱的原理,设计了基于自聚焦透镜的透射式气室结构。利用自聚焦透镜作为光纤准直透镜和聚焦透镜,应用于透射型气室,并提出了在透射式气室中将多对自聚焦透镜组串联用以增加吸收光程的方法,用该方法可以明显提高气室的检测灵敏度。基于自聚焦透镜的透射式气室成功地应用于基于谐波检测技术的吸收型光纤气体传感器系统中,获得较好的检测效果。     

转炉炼钢煤气回收利用自动控制系统的研究与应用

针对某炼钢厂的转炉炼钢煤气回收系统进行深入研究,设计构建基于西门子S7-300的自动控制系统。该文深入了解煤气回收工艺流程和回收条件,构建以S7-300为主站、采用Profi-bus进行数据通信、以西门子WinCC系统进行监控的转炉炼钢煤气回收自动控制系统。并在以上基础上以S7-300为主站通过Profibus-DP与变频器从站进行数据通信,用变频器对加压机风进行变频调速,采用煤气回流控制实现恒压供气。     

混合气体检测中纳米多孔膜晶振传感器的应用

就混合气体中某些成份含量的定性与定量检测问题,设计了纳米多孔膜晶振传感器与神经网络相结合的智能气体检测分析系统。该系统以纳米材料多孔膜附于石英晶振之上作为感应元件,传感器对不同气体产生不同的振荡频率,表现出较好的选择性,同时亦存在交叉敏感性问题。为此采用了具有GA—BP处理算法的神经网络,通过训练建立起最佳结构,解决混合气体检测中的交叉敏感难题,进而获得比较精确的辨识输出结果。实验结果表明,这是一种可行的混合气体测试分析方法。     

Techno-economic evaluation of reducing shielding gas consumption in GMAW whilst maintaining weld quality

A series of experimental trials have been conducted to investigate the effects of reducing the shielding gas consumption in gas metal arc welding (GMAW). A number of claims have been made as to potential shielding gas savings in the GMAW process when using gas-saving devices such as commercially available self-regulating valves. However, the literature and data available on weld quality obtained as a result of reducing the shielding gas flow rate is not readily available, so the thrust of this study is to present a new body of data to report on the technical and economic merits of controlling the shielding gas flow rate using (a) a conventional flow meter and (b) a ‘new to market’ self-regulating gas-saving device. It has been determined that, in a draft-free environment, the shielding gas flow rate can be reduced to 6?L/min without diminishing weld quality, although a lower flow rate was more susceptible to the effects of cross-drafts, and the weld quality level was compromised. In addition to the economic savings associated with reducing the shielding gas flow rate, there are several weld aspects that have been found to be influenced by the shielding gas flow rate including penetration, leg length, distortion and peak temperature, thus suggesting that the heat transfer efficiency is affected by the shielding gas flow rate. This significant finding supports the view that there is scope to increase the travel speed when implementing a lower flow rate and, consequently, enhance productivity.     

皮膜式煤气表传动机构的开发设计

这里结合皮膜式煤气表的常用传动机构的特点和煤气计量技术的发展，提出一种适用于皮膜式煤气表的新型端面齿轮转阀传动机构，并详细介绍其设计方法。     

Magneto-rheological accumulator for temperature compensation in hydropneumatic suspension systems

Hydro-pneumatic suspension systems consist of two fluids acting upon each other, usually gas over oil. In these systems, a compressible gas such as nitrogen is used as the springing medium, while a hydraulic fluid is used to convert the pressure to force. One of the problems associated with hydro-pneumatic systems is the effect of temperature change on the spring characteristics, which results in a variation in the spring rate and ride height. The important characteristics of a gas chamber filled with gas or air are to maintain the setting pressure, with very small variations, even for long strokes. This paper presents a magneto-rheological (MR) accumulator that can adjust the pressure of the gas chamber through the use of an MR device. To analyze the characteristics of the gas chamber, mathematical modeling based on the energy equation for a gas in a closed container is carried out. Further, a prototype of the MR device is designed and manufactured, and its performance is evaluated. The theoretical results are validated by conducting experiments in the laboratory environment. It is demonstrated that the MR accumulator can effectively compensate for the pressure variations caused by an increase in the gas temperature. Moreover, this research provides new information about the applicability of the MR accumulator to devices that use conventional accumulators.     

以制冷剂为工作介质的止推气体轴承静态特性分析*

针对离心式压缩机润滑问题,提出以R134a为润滑工质的动压气浮轴承,基于流体润滑的雷诺方程,从制冷剂与空气的流动对比出发,通过理论假设实现气体轴承的建模与分析,采用数值分析对气膜流场进行三维设计计算分析,得到动压止推轴承的气膜厚度分布、气膜压力分布、承载力、功率损耗等特性。结果表明:在相同的情况下以R134a为工质的气体轴承的承载力是空气的50%左右,两者的承载力都随着扇形瓦张角、转速的增大而增大,随倾斜面高度和节距比的增大而先增大后减小,随最小初始气膜厚度的增大而减小;在相同的情况下以R134a为工质的系统的功率损耗是空气的60%左右,两者系统的功率损耗受最小初始气膜厚度和速度的影响最大,转速越高、最小初始气膜厚度越小,两者的功率损耗越大。     

斯特林发动机配气活塞气体的作用效应

为了能够深入认识自由活塞斯特林发动机配气活塞的运动特性,对动力活塞固定不动时的配气活塞的气体作用效应进行了分析,并设计了配气活塞的单独运动实验,在此基础上提出了配气活塞固有频率的计算式。分析了工作腔压力波超前与滞后配气活塞位移两种情况下受到的气体力的作用情况,采用旋转矢量法阐述了气体力的作用机理。当压力波超前或滞后活塞位移小于90°时,认为一部分气体力发挥了气体弹簧的作用,使系统固有频率增大;当压力波超前或滞后活塞位移大于90°但小于180°时,认为一部分气体力发挥了惯性力的作用,使系统固有频率减小。热源温度越高,系统的固有频率越小。利用本实验室的一台自由活塞斯特林发动机进行实验,验证了上述气体力作用的效应与规律,且利用此理论计算了系统固有频率的准确性。     

西门子GUD1S.V94.3A燃气-蒸汽联合循环发电机组的应用与优化

为便于同行能更好地了解和掌握燃气轮机的基本情况,介绍了西门子V94.3A型燃气轮机基本结构与运行特性,总结了该燃机在我国运行中存在的一些突出问题,并提出了优化和改进的措施与方法,以便将燃机技术普及并成熟应用到发电厂.实践结果表明这种新型燃气-蒸汽联合循环发电机组发电技术,体现了其机组整体运行安全可靠、效率高、排放低、启...     

A high-pressure cell for kinetic studies on gas hydrates by powder x-ray diffraction

A new high-pressure-low-temperature cell was developed for in situ observations of gas hydrates by powder x-ray diffraction. The experimental setup allows investigating hydrate formation and dissociation as well as transformation processes between different hydrate crystal structures as a function of pressure, temperature, and feed gas composition. Due to a continuous gas flow, the composition of the gas phase is kept constant during the whole experiment. This is crucial for the formation of mixed hydrates formed from feed gas mixtures that contain one or more components in low concentrations. The pressure cell can be used in a pressure range between 0.1 and 4.0 MPa and a temperature range between 248 and 298 K. First results of time-resolved measurements of a mixed structure II CH(4) + iso-C(4)H(10) hydrate and a structure I CO(2) hydrate are presented.     

燃气热水器的分类研究

燃气是一种高效、环保、经济的能源,燃气热水器作为人们普遍使用的生活用具正在以前所未有的速度发展,本文对燃气热水器的知识和分类作了简单介绍。     

The technique of producing reference-standard gas by the flow-measuring method

The reference-standard gas-generating system used for the calibration of an air-pollution measuring instrument is described. By blending the pollutant gas and the diluent gas of known flow rates, the system can produce the mixed gas continuously. The concentration of the pollutant in the mixed gas is given as the ratio of the flow rates of each gas. The system is composed of a capillary flowmeter for the pollutant gas, a laminar flowmeter for the diluent gas and a mixing element. These componenta are placed in a constant-temperature bath. The following experiments on the problems of producing the standard gas were made:

1. (1) Calibration of the flowmeter by sonic nozzle.

2. (2) Verification of homogeneity of mixed gas.

3. (3) Comparison with the standard gas (in cylinder) prepared by the mass-measuring method.

The system makes possible production of mixed gases, of concentration from 0.1 to 1000 ppm for the pollutant gas (CO and NO) and with a stability of ±0.3%, during 24 h.     

光纤持气率计在气/水两相流中响应规律的实验研究

为考察现有光纤持气率计对气液两相流的响应特性,采用多相流标定装置对其进行测定,系统研究光纤持气率计在不同气/水配比条件下的响应规律。实验结果表明,光纤持气率探针在静水条件下以及在气/水总量为80m3/d的不同气/水配比情况下,持气率对气含量的响应均基本呈线性变化规律;当气/水总量低于45m3/d时,持气率对含水量响应不呈线性规律。