烟气粉尘脱硫气桥检测系统的研究

研究烟气粉尘脱硫检测系统的气桥传感器 .计算由于烟气含硫化合物及粉尘浓度动态的变化引起的桥臂气阻的变化 ,阐述非线性气阻的平衡条件和不平衡的信号输出 .文章讨论应用气桥原理制造检测元件及气桥和温度传感器的关系 .最后介绍烟气脱硫及除尘在工业环境治理中的应用 .

在数纸机上非线性气桥的检测原理及其应用

八十年代初,我国先后引进英国的Mark——6C 型及日本的NK——3ED 型数纸机,广州、南京、重庆等地开展了研制工作.近三年来结合洋为中用的原则,有所创新,初见成效,已有不同型号的数纸机问世,填补了我国数纸机生产的空白.本文阐述在数纸机上非线性气桥的检测原理,用数字仿真及实验数据的计算程序.计算气桥不平衡输出值及平衡条件,还介绍了气桥在数纸机上应用的情况.

千米桥潜山凝析气藏低密度水包油压井液研究

大港油田千米桥潜山常压凝析气藏已进入中期开采阶段,由于使用的水基压井液密度均大于1.0g/cm3,洗井时经常有压井液漏失,对储集层损害严重,严重降低产能.室内岩心研究表明,在净压力作用下,储集层的压力敏感性较强,气体流速敏感性损害程度很弱,地层水损害程度中偏严重.在模拟储集层高温条件下,对现场使用的压井液损害储集层的情况进行评价,结果显示对渗透率小于10mD的气层渗透率的损害平均为53%,这主要是压井液的滤液进入岩心的细小孔喉引起水锁伤害所致.根据不同伤害机理理研制出一种效果较好的低密度(0.84～0.90g/cm3)水包油压井液,抗温168℃,抗水、油污染容量10%,渗透率恢复值平均为90.06%,最低在87.6%以上.

排气门阀桥开裂失效分析

某商用车管状气门阀桥在车削加工过程中多件出现开裂现象,裂纹分布在侧孔端面、中间孔端面及阀桥管壁。对其中一件开裂阀桥,进行化学成分分析、显微形貌分析、金相分析、SEM分析,同时结合阀桥热锻成型工艺、机械加工工艺、热处理工艺,认为该桥热锻成坯料后未及时去应力退火,在后续热处理(淬火+回火)过程中由于碳析出增加了内部组织应力,最终在车削时受外应力最终导致开裂。

千米桥潜山排水采气试验

本文主要介绍了两种排水采气工艺的原理、特点和适用性;根据其适用性优选千米桥潜山断块的适用单井;进行论证和证明。

气马达变向运动时死区问题的解决方法

传统的电磁比例滑阀控制气马达的转速和转向时,在换向过程中,气量逐渐减小直至为零。在气量为零期间即死区,气马达处于失控状态,影响轴的目标位置。采用计算机系统控制的气H-桥后,通过气马达的流量和方向不再是机械联系而是软件控制,可消除滑阀固有的机械死区,实现气马达平稳运转和换向的使用要求。

疏水化、疏水作用、疏水影响和异相凝聚及其在矿物加工中的重要性

有关固体界面性质以及表面改性和表面性质测量等知识都是与矿物加工密切相关的。在本文中,叙述了固体表面的润湿性及影响表面润湿性的因素,对润湿现象做了一些解释,叙述了一些模型的建立。在矿物加工中,固体表面适当的疏水性是需要的,一般是通过表面活性剂吸附来实现其表面疏水化。在极性和非极性药剂吸附的能量平衡中,除了极性基与固体表面作用外,吸附在固体表面上的非极性基的缔合作用也是相当重要的。近年来,广泛的研究工作都是集中在水溶液中疏水固体表面之间的长距离引力作用。从现在提出的结果可以发现,附着在固体表面上的纳米气泡发生碰撞和兼并,形成了气桥,而这个气桥的毛细管力在固体表面之间产生了长距离引力作用。在疏水颗粒与大气泡碰撞时,也就是在浮选条件下,纳米气泡对颗粒向气泡固着起着决定作用。浮选过程中的流体力学也起着重要作用。

InP/InGaAs Heterojunction Bipolar Transistor with Base μ-Bridge and Emitter Air-Bridge

An InP-based single-heterojunction bipolar transistor （SHBT） with base μ-bndge and emitter air-bridge is reported. Because those bridges reduce parasitic capacitance greatly, the cutoff frequency fT of the 2μm ×12.5μm InP SHBT without de-embedding reaches 178GHz. It is critical in high-speed low power applications,such as OEIC receivers and analog-to-digital converters.

Design and analysis of a bisected wheel-based cable climbing robot

To inspect inner wires of the cylindrical cables on a cable-stayed bridge, a new bisected wheel-based cable climbing robot is designed. The simple structure and the moving mode are described and the static features of the robot are analyzed. A cable with a diameter of 139 mm is selected as an example to calculate the design parameters of the robot. For safety energysaving landing in the case of electrical system failure, an electric damper based on back electromotive force and a gas damper with a slider-crank mechanism are introduced to exhaust the energy generated by gravity when the robot is slipping down along the cables. A simplified mathematical model is analyzed and the landing velocity is simulated. For the present design, the robot can climb up a cable with diameters varying from 65 to 205 mm with payloads below 3.5 kg. Several climbing experiments performed on real cables confirm that the proposed robot meets the demands of inspection.

谨防现代“弄臣”

继《苍天在上》“火爆”荧屏后,电视连续剧《宰相刘罗锅》又风靡大江南北,深受观众喜爱。戏中,乾隆皇帝和大臣和坤有段对话很耐人寻味。乾隆问:“你愿意当忠臣,还是愿意当奸臣?”“我既不愿当忠臣,也不愿意当奸臣”,和坤答。“为什么?”“当忠臣往往被奸臣害死,当奸臣最后也没有好下场”。和坤回答得很妙。 “那么你要当什么样的臣子?”乾隆进一步问。 “我愿当个弄臣,就是想万岁所想,伺候好万岁的吃喝玩乐,万岁想啥我就千啥,一切都听万岁爷的。” 和坤的回答正中乾隆下怀,使他发出了会心的微笑。

A Comparative Assessment of Aerodynamic Models for Buffeting and Flutter of Long-Span Bridges

Wind-induced vibrations commonly represent the leading criterion in the design of long-span bridges. The aerodynamic forces in bridge aerodynamics are mainly based on the quasi-steady and linear unsteady theory. This paper aims to investigate different formulations of self-excited and buffeting forces in the time domain by comparing the dynamic response of a multi-span cable-stayed bridge during the critical erection condition. The bridge is selected to represent a typical reference object with a bluff con- crete box girder for large river crossings. The models are viewed from a perspective of model complexity, comparing the influence of the aerodynamic properties implied in the aerodynamic models, such as aerodynamic damping and stiffness, fluid memory in the buffeting and self-excited forces, aerodynamic nonlinearity, and aerodynamic coupling on the bridge response. The selected models are studied for a windspeed range that is typical for the construction stage for two levels of turbulence intensity. Furthermore, a simplified method for the computation of buffeting forces including the aerodynamic admittance is presented, in which rational approximation is avoided. The critical flutter velocities are also compared for the selected models under laminar flow.

Aerodynamic stability of cable-supported bridges using CFRP cables

To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge, its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable’s cross-sectional area should be deter-mined by the principle of equivalent axial stiffness.

Parameter optimization for improved aerodynamic performance of louver-type wind barrier for train-bridge system

To improve the safety of trains running in an undesirable wind environment,a novel louver-type wind barrier is proposed and further studied in this research using a scaled wind tunnel simulation with 1:40 scale models.Based on the aerodynamic performance of the train-bridge system,the parameters of the louver-type wind barrier are optimized.Compared to the case without a wind barrier,it is apparent that the wind barrier improves the running safety of trains,since the maximum reduction of the moment coefficient of the train reaches 58%using the louver-type wind barrier,larger than that achieved with conventional wind barriers(fence-type and grid-type).A louver-type wind barrier has more blade layers,and the rotation angle of the adjustable blade of the louver-type wind barrier is 90–180°(which induces the flow towards the deck surface),which is more favorable for the aerodynamic performance of the train.Comparing the 60°,90°and 120°wind fairings of the louver-type wind barrier blade,the blunt fairing is disadvantageous to the operational safety of the train.

Experimental study on aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds

In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measurements of two typical sections, one train-head section and one train-body section, at the windward and leeward tracks were conducted under the smooth and turbulence flows with wind attack angles between-6° and 6°, and the corresponding aerodynamic force coefficients were also calculated using the integral method. The experimental results indicate that the track position affects the mean aerodynamic characteristics of the vehicle, especially for the train-body section. The fluctuating pressure coefficients at the leeward track are more significantly affected by the bridge interference compared to those at the windward track. The effect of turbulence on the train-head section is less than that on the train-body section. Additionally, the mean aerodynamic force coefficients are almost negatively correlated to wind attack angles, which is more prominent for vehicles at the leeward track. Moreover, the lateral force plays a critical role in determining the corresponding overturning moment, especially on the train-body section.

Superposability of unsteady aerodynamic loads on bridge deck sections

The 2-dimensional unsteady aerodynamic forces,in the context of both a thin airfoil where theory of potential flow is always applicable and a bluff bridge-deck section where separated flow is typically induced,are investigated from a point of view of whether or not they conform to the principle of linear superposition in situations of various structural motions and wind gusts.It is shown that some basic preconditions that lead to the linear superposability of the unsteady aerodynamic forces in cases of thin airfoil sections are no longer valid for a bluff section.Theoretical models of bridge aerodynamics such as the one related to flutter-buffeting analysis and those concerning aerodynamic admittance(AA)functions,however,necessitate implicitly this superposability.The contradiction revealed in this work may throw light on the perplexing problem of AA functions pertaining to the description of buffeting loads of bridge decks.Some existing theoretical AA models derived from flutter derivatives according to interrelations valid only for thin airfoil theories,which have been employed rather extensively in bridge aerodynamics,are demonstrated to be illogical.Finally,with full understanding of the preconditions of the applicability of linear superposability of the unsteady aerodynamic forces,suggestions in regard to experiment-based AA functions are presented.

Study of the aerostatic and aerodynamic stability of super long-span cable-stayed bridges

With the increase of span length, the bridge tends to be more flexible, and the wind stability be- comes an important problem for the design and construction of super long-span cable-stayed bridges. By taking a super long-span cable-stayed bridge with a main span of 1 400 m as example, the aerostatic and aerodynamic stability of the bridge are investigated by three-dimensional nonlinear aerostatic and aerodynamic stability analy- sis, and the results are compared with those of a suspension bridge with a main span of 1 385 m, and from the aspect of wind stability, the feasibility of using cable-stayed bridge in super long-span bridge with a main span above l 000 m is discussed. In addition, the influences of design parameters including the depth and width of the girder, the tower structure, the tower height-to-span ratio, the side-to-main span ratio, the auxiliary piers in the side span and the anchorage system of stay cables, etc on the aerostatic and aerodynamic stability of su- per long-span cable-stayed bridges are investigated numerically; the key design parameters are pointed out, and also their reasonable values are proposed.

Effects of wind barriers on the aerodynamic characteristics of bridge-train system for a road-rail same-story truss bridge

Wind barriers are commonly adopted to prevent the effects of wind on high-speed railway trains,but their wind-proofing effects are greatly affected by substructures.To investigate the effects of wind barriers on the aerodynamic characteristic of road-rail same-story truss bridge-train systems,wind tunnel experiments were carried out using a 1:50 scale model.Taking a wind barrier with a porosity of 30%as an example,the aerodynamic characteristics of the bridge train system under different wind barrier layouts(single-sided and double-sided),positions(inside and outside)and heights(2.5 m,3.0 m,3.5 m and 4.0 m)were tested.The results indicate that the downstream inside wind barrier has almost no effect on the aerodynamic characteristics of the train-bridge system,but the downstream outside wind barrier increases the drag coefficient of the bridge and reduces both the lift coefficient and drag coefficient of the train due to its effect on the trains wind pressure distribution,especially on the trains leeward surface.When the wind barriers are arranged on the outside,their effects on the drag coefficient of the bridge and shielding effect on the train are greater than when they are arranged on the inside.As the height of the wind barrier increases,the drag coefficient of the bridge also gradually increases,and the lift coefficient and drag coefficient of the train gradually decrease,but the degree of variation of the aerodynamic coefficient with the height is slightly different due to the different wind barrier layouts.When 3.0 m high double-sided wind barriers are arranged on the outside of the truss bridge,the drag coefficient of the bridge only increases by 12%,while the drag coefficient of the train decreases by 55%.

Study on effects of environmental temperature on dynamic characteristics of Taizhou Yangtze River Bridge

The dynamic characteristics of three-tower and two-span suspension bridge are analyzed at different global temperatures. An equivalent cable inner force method is proposed to consider temperature effects and to study the effects of environmental temperature on dynamic characteristics of Taizhou Yangtze River Bridge. The result demonstrates that the effects of temperature can not be neglected in static or dynamic analysis of Taizhou Yangtze River Bridge. The relationship between temperature and frequency is negative. The effects of temperature should be taken into account in experimental modal analysis of long-span bridges and damage identification.

Aerodynamic coefficient of vehicle-bridge system by wind tunnel test

The changes of three components of aerodynamic force were discussed with the attack angle conversion for three kinds of section models. Based on the project of Shanghai Yangtze River Bridge, the wind tunnel test was conducted to obtain its three components of aerodynamic force including 75 conditions of the construction stage, the bridge without vehicles and the bridge with vehicles from - 12 degrees to ＋ 12 degrees. For the bridge with vehicles, the drag force coefficient and the absolute value of both lift coefficient and moment coefficient were decreased by the vehicles. The test resuh shows that the bridge railing and vehicles have much influence on the three components of aerodynamic force of the vehicle-bridge system for Shanghai Yangtze River Bridge.