Mass transfer enhancement and hydrodynamic performance with wire mesh coupling solid particles in bubble column reactor

It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on bubble motion and gas-liquid mass transfer process in a bubble column.Particle image velocimetry(PIV)technology was employed to analyze the flow field and bubble motion behavior,and dynamic oxygen absorption technology was used to measure the gas-liquid volumetric mass transfer coefficient(kLa).The effect of embedding wire mesh,adding solid particles,and wire mesh coupling solid particles on the flow characteristic and kLa were analyzed and compared.The results show that the gas-liquid interface area increases by 33%-72%when using the wire mesh coupling solid particles strategy compared to the gas-liquid two-phase flow,which is superior to the other two strengthening methods.Compared with the system without reinforcement,kLa in the bubble column increased by 0.5-1.8 times with wire mesh coupling solid particles method,which is higher than the sum of kLa increases with inserting wire mesh and adding particles,and the coupling reinforcement mechanism for affecting gas-liquid mass transfer process was discussed to provide a new idea for enhancing gas-liquid mass transfer.

Mechanical property of cylindrical sandwich shell with gradient core of entangled wire mesh

To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components,the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed in this paper.Firstly,the gradient cores of entangled wire mesh in the axial and radial directions were prepared by using an in-house Numerical Control weaving machine,and the metallurgical connection between skin sheets and the gradient core was performed using vacuum brazing.Secondly,to investigate the mechanical properties of cylindrical sandwich shells with axial or radial gradient cores,quasi-static and dynamic mechanical experiments were carried out.The primary evaluations of mechanical properties include secant stiffness,natural frequency,Specific Energy Absorption(SEA),vibration acceleration level,and so on.The results suggest that the vibration-attenuation performance of the sandwich shell is remarkable when the high-density core layer is at the end of the shell or abuts the inner skin.The axial gradient material has almost no influence on the vibration frequencies of the shell,whereas the vibration frequencies increase dramatically when the high-density core layer approaches the skin.Moreover,compared to the conventional sandwich shells,the proposed functional grading cylindrical sandwich shell exhibits more potential in mass reduction,stiffness designing,and energy dissipation.

Effect of wire mesh interlayer in explosive cladding of dissimilar grade aluminum plates

Explosive cladding of Al 5052–Al 1100 plate, interfaced with a stainless steel wire mesh interlayer, is attempted. Loading ratio and standoff distance were varied. An increase in loading ratio (R) and standoff distance (S) enhances the plate velocity (Vp), dynamic bend angle (β) and pressure developed (P). The interface morphology of the explosive clads confirms strong metallurgical bond between the wire mesh and aluminum plates. Further, a smooth transition from straight to undulating interlayered topography is witnessed. The introduction of a wire mesh, as interlayer, leads to an improvement in mechanical strength with a slender reduction in overall corrosion resistance of the “explosive clads”.

Performance evaluation of the incorporation of different wire meshes in between perforated current collectors and membrane electrode assembly on the Passive Direct methanol fuel cell

Passive Direct methanol fuel cells(DMFC)are more suitable for charging small capacity electronic devices.In passive DMFC,the fuel and oxidant are supplied by diffusion and natural convection process on the anode and cathode sides respectively.Current collectors(CC)play a vital importance in fuel cell performance.This paper presents the combined impact of perforated and wire mesh current collectors(WMCC)on passive DMFC performance.Three types of open ratios of perforated current collectors(PCC),such as 45.40%,55.40%and 63.40%and two types of wire mesh current collectors with open ratios of 38.70%and 45.40%were chosen for the experimental work.A combination of TaguchiL9 rule is considered.A combination of three PCC and two WMCC on both anode and cathode was used.Methanol concentration was varied from 1 mol·L^(-1)-5 mol·L^(-1)for nine combinations of PCC and WMCC.From the experimental results,it is noticed that the combination of PCC and WMCC with an open ratio of 55.40%and 38.70%incorporated passive DMFC produced peak power density at 5 mol·L^(-1)of methanol concentration.The passive DMFC performance was evaluated in terms of maximum power density and maximum current density.The combined current collectors of PCC and WMCC open ratios of 55.40%+38.70%have more stable voltage than single PCC of open ratio 63.40%at 4 mol·L^(-1)of methanol concentration.

Estimate the Ventilation Effect from Wire Mesh Screen Assisted Solar Chimney

In 1750s European houses, chimneys are used to remove smoke and dust particle from the fire place to the ambient. At present the applications of chimneys are extended for house ventilation, which is known as solar chimney assisted ventilation system. In this paper, the effect of wire mesh screen on chimney assisted ventilation system is studied and presented. Natural draft chimney integrated with solar heating system that is known as solar chimney, can be used for building ventilation. Number of research works had been conducted on different types of solar chimney to enhance the building ventilation performance. In this study a solar chimney model is designed and modified with wire mesh screens. An electric heating system is installed in the models to replace the solar absorber in the solar chimney. The airflow rates and the exit air temperatures are also measured and compared for normal chimney and modified chimneys under different heat loads. The performances of the chimneys are evaluated to determine the effects of wire mesh screen on the solar chimney. Experimental results indicated the solar chimney model with 0.64 mm × 0.64 mm pore size wire mesh screen at the exit is able to enhance velocity and the exit air temperature are about 54% and 41%, respectively. It has been concluded that the wire mesh screen has significant effect of model solar chimney and is able to enhance the performance.

Corrosion considerations in the capacity of welded wire mesh

Ground control in underground mines employs rock reinforcement and surface support to maintain the integrity of excavations for their anticipated working life.The performance of a ground support system,however,is more complex and relies on effective load distribution between reinforcement and surface support elements.Typically,failure of the ground support system is along its weakest link,often the surface support.Consequently,the degradation of any ground support element over time will compromise the structural integrity of the ground support system.Degradation of ground support can be due to multiple factors.This paper focuses on the role of corrosion in the long-term performance of mesh.It presents a comprehensive methodology for quantifying the impact of degradation on bolted welded wire mesh over time.This is an important aspect,as the mesh is often the first element that fails in a ground support system.This paper combines information from extensive field and laboratory studies on mesh corrosion with calibrated numerical models to capture the long-term performance of different bolting patterns under a range of corrosion environments.A series of three-dimensional(3D)distinct element models(DEM)were constructed to quantify the impact of different corrosion rate scenarios on the loading capacity,displacement,and failure mechanisms of bolted welded wire mesh in diamond and square bolting patterns.This work can contribute to the management of long-term hazards associated with corrosion of mesh in corrosive environments under non-seismic mining conditions.

Effect of wire mesh casing treatment on axial compressor performance and stability

In this paper,a kind of Wire Mesh Casing Treatment(WMCT)is proposed to improve the stable operating range of the compressor.In contrast to the traditional circumferential groove,as for WMCT,a layer of wire mesh is laid on the surface of the circumferential groove.Parametric studies were conducted on the low-speed axial flow compressor,including the groove width,axial location,and mesh count.The optimum axial location for WMCT is related to its groove width.A higher wire mesh count results in a smaller compressor stall margin improvement.Steady simulations were carried out to study the effect of WMCT on the flow structure of the compressor.The wire mesh in the WMCT has a certain flow resistance,which restricts the flow into and out of the groove.Due to the WMCT,the flow parameter in the tip region of the rotor is less sensitive to changes in the operating conditions of the compressor.The WMCT causes the rotor tip blade loading to shift backward,inhibiting the formation of spill forward of the leakage flow,and thus improving the stability of the compressor.The flow resistance on the groove surface is a new degree-of-freedom for the casing treatment designer.

Effect of silicon carbide and wire-mesh reinforcements in dissimilar grade aluminium explosive clad composites

Aluminium composites are inevitable in the manufacture of aircraft structural elements owing to less weight,superior corrosion resistance and higher specific properties.These composites reduce the weight of the aircraft,improve the fuel efficiency and enhance the maintenance duration.This study proposes the development of dissimilar grade aluminium(aluminium 1100-aluminium 5052)composites with different reinforcement’s viz.,stainless steel wire-mesh,silicon carbide(SiC)powders and SiC powder interspersed wire-mesh,by explosive cladding technique.Wire-mesh enhances the friction and restricts the movement of flyer plate to craft a defect free clad,while SiC particles form a band on the interface.Highest strength is obtained when SiC powder interspersed wire mesh is employed as reinforcement.The dissimilar aluminium explosive clad with SiC particle reinforcement results in lower strength,which is higher than that of the weaker parent alloy and that of the conventional dissimilar aluminium explosive clads without any reinforcement.

Numerical studies of dynamic behavior of liquid film on single-layer wire mesh with different wettabilities

Droplet impacting on the stainless steel wire mesh is very common in chemical devices,like a rotating packed bed.Surface wettability of wire mesh significantly affects the liquid flow pattern and liquid dispersion performance.However,the effect of surface wettability on the impaction phenomena at microscale such as liquid film is still unknown.In this work,the dynamic behavior of liquid film on the surface of wire mesh was analyzed by computational fluid dynamics simulation.The dynamic behavior of liquid film on the surface of wire mesh can be divided into the following three steps:(1)spreading step;(2)shrinkage process;(3)stabilizing or disappearing step.Effects of surface wettability,as well as operating conditions,on wetting area and liquid film thickness were studied.Compared to the hydrophilic wire mesh,the final wetting area of hydrophobic wire mesh is zero in most cases.The average liquid film thickness on the surface of hydrophilic wire mesh is 30.02–77.29μm,and that of hydrophobic wire mesh is 41.76–237.37μm.This work provided a basic understanding of liquid film flow at microscale on the surface with various surface wettabilities,which can be guiding the packing optimization and design.

Seismic safety evaluation methodology for masonry building and retrofitting using splint and bandage technique with wire mesh

The paper presents a seismic safety assessment of unreinforced masonry(URM)building using two approaches.The first approach uses the‘Pier Analysis’method,based on the concept of equivalent lateral stiffness,where in-plane and out-of-plane actions are considered independently.The second approach is developed with the program SAP2000,where the linear response is evaluated using continuum‘finite element modelling’(FEM).Both methods are compared to evaluate the safety of wall piers and the differences in the outcomes under combined gravitational and lateral seismic forces.The analysis results showed that few wall elements are unsafe in in-plane and out-of-plane tension.It is also observed that the pier analysis method is conservative compared to FEM,but can be used as a simplified and quick tool in design offices for safety assessment,with reasonable accuracy.To safeguard the URM wall piers under lateral loads,a retrofitting technique is adopted by providing vertical and horizontal belts called splints and bandages,respectively,using welded wire mesh(WWM)reinforcement.The study using the‘Pier Analysis’shows that the lateral load capacity of unsafe URM piers can be enhanced up to 3.67 times and made safe using the applied retrofitting technique.Further,the retrofitting design methodology and recommendations for application procedures to on-site URM buildings are discussed in detail.

Comparison of mixed-mode forced-convection solar dryer with and without stainless wire mesh in solar collector

A mixed-mode forced-convection solar dryer(MMFCSD)is a device that utilizes both direct and indirect solar energy.The solar col-lector,which stores thermal energy for indirect solar uses,is an essential component of the dryer.Unfortunately,the thermal effi-ciency of this device is generally low.In this study,a technique was employed to improve the heat transfer of the solar collector in a MMFCSD.The technique involved adjusting the air flow pattern into a swirling flow to disturb the thermal boundary layer on the absorber plate under forced convection by using stainless wire mesh.The experiment was conducted under actual conditions and bananas were used as the drying sample.The experimental results of the thermal efficiency of the solar collector(ƞ_(solar))and the drying efficiency(ƞ_(drying))are presented.The results indicated that the air outlet temperature andƞsolar of the solar collector with stainless wire mesh were higher than the case without stainless wire mesh,reaching a maximum temperature of 46.22°C and 37.97°C,and average ƞ_(solar) of 0.26±0.02 and 0.14±0.01,respectively.The MMFCSD with stainless wire mesh had a higher ƞ_(drying) than the case without stain-less wire mesh,with values of 0.048±0.004 and 0.039±0.003,respectively,resulting in an~23.07%increase.This was attributed to the air swirling flow through the stainless wire mesh and the heat accumulation in the drying chamber,which led to an increase in the drying chamber temperature from 54.03°C to 63.60°C,an increase in the effective moisture diffusivity from 7.28×10^(-7) to 1.19×10^(-6) m^(2)/s and a decrease in the drying time of 5 h 30 min.However,further research is needed to investigate the quality of the dried sam-ples and their economic value.

基于动网格技术的CMT-WAAM熔池温度场与流场数值模拟

针对基于冷金属过渡(CMT)技术的镁合金摆动电弧增材制造(WAAM)过程,采用流体体积(VOF)法和动网格(DM)技术建立了分别考虑熔滴和熔池受力情况的三维瞬态数值模型,研究了熔滴过渡和熔池流动过程中的温度场和速度场变化.结果表明,相应试验结果验证了所建立数值模型的有效性,熔池和熔滴尺寸参数模拟的误差均在10%之内.在CMT-WAAM开始阶段,基板表面和焊丝在电弧热作用下熔化分别形成熔池和熔滴.在焊丝向熔池送进过程中,熔滴不断长大,并在表面张力作用下长成球形.熔滴金属的热量主要通过热传导的形式向熔池传递,熔池最高温度随着熔滴金属的过渡而升高,熔池最高温度可达2100.0K;随着焊丝的回抽,熔池最高温度降低至1763.6K.随着焊丝向熔池送进,熔滴的最大速度从1.87 m/s逐渐减小到1.07 m/s,而熔池的最大速度仅为0.87 m/s.当熔滴金属前端与熔池发生接触后,液态金属的最大速度可达到4.21 m/s;随着焊丝的机械回抽,液态金属的最大速度在1.69~4.90 m/s范围内波动.当熔滴与熔池接触发生短路时,熔滴金属从熔池表面流向熔池底部和熔池两侧,增强了对熔池底部和熔池两侧的搅拌作用,使得熔池体积增加;当熔滴从焊丝端部脱离后,熔池中液态金属从熔池底部流向熔池表面和熔池两侧,熔池温度和流体速度随之降低,从而减缓了熔池体积的增加.此外,熔池自由表面在摆动电弧作用下呈现波浪式变形.

Large-scale laboratory investigation of pillar-support interaction

Underground mine pillars provide natural stability to the mine area,allowing safe operations for workers and machinery.Extensive prior research has been conducted to understand pillar failure mechanics and design safe pillar layouts.However,limited studies(mostly based on empirical field observation and small-scale laboratory tests)have considered pillar-support interactions under monotonic loading conditions for the design of pillar-support systems.This study used a series of large-scale laboratory compression tests on porous limestone blocks to analyze rock and support behavior at a sufficiently large scale(specimens with edge length of 0.5 m)for incorporation of actual support elements,with consideration of different w/h ratios.Both unsupported and supported(grouted rebar rockbolt and wire mesh)tests were conducted,and the surface deformations of the specimens were monitored using three-dimensional(3D)digital image correlation(DIC).Rockbolts instrumented with distributed fiber optic strain sensors were used to study rockbolt strain distribution,load mobilization,and localized deformation at different w/h ratios.Both axial and bending strains were observed in the rockbolts,which became more prominent in the post-peak region of the stress-strain curve.

基于丝网传感器的两相流相场与浓度场同步测量方法

准确认识核反应堆燃料组件内交混行为对其优化设计与安全分析极为关键。丝网传感器可对流道截面进行高时空分辨率相分布成像,结合示踪剂质量平衡法已可实现燃料组件单相交混精细测量。但因缺乏两相下浓度场后处理算法,尚无法应用于两相交混研究。本文考虑到相同空泡份额下液相电导率对丝网敏感体的影响特性,提出了一种两相浓度反演算法,实现了两相流动空泡份额场、液相浓度场同步测量。基于电势场数值模拟与实验确认了算法的正确性与精确度。结果显示算法可适用于各类复杂的两相流工况,典型工况下两相浓度反演算法获得的浓度分布平均相对偏差为3.6%。基于本文实验结果表明,该算法计算获得的浓度矩阵平均相对偏差小于3%,进一步验证了同步测量方法的良好的适用性与精确度。

基于丝网传感器的棒束通道两相流实验研究

为研究压水堆棒束通道内气液两相流型特性及演变规律,基于双层丝网传感器(WMS)在常温常压下开展了3×3棒束通道内的空气-水两相流型测量实验,流型包含泡状流、泡-帽状流和弹状流。结果表明:常温常压下横向升力方向发生反转的临界气泡直径范围为4~5.8 mm。此外,对于泡状流,气相表观速度较低时,空泡份额呈现“壁峰”分布;气相表观速度较高时,呈现“中心峰”分布。对于泡-帽状流,相邻子通道内,帽状气泡交叉分布,并引发液相在相邻子通道间的大尺度交混,空泡份额呈现“中心峰”分布。对于弹状流,大尺寸气泡沿轴向发展会跨越子通道间隙并聚合为弹状气泡,空泡份额“中心峰”分布更为明显。将实验数据用以评价部分漂移流模型,其中Bestion漂移流模型因高估漂移速度,导致空泡份额预测结果偏小;Ozaki漂移流模型对空泡份额预测较为精准,其平均相对误差为9.8%。

玻璃纤维-钢丝网增强复合材料拉伸性能研究

采用真空辅助树脂灌注成型(VARI)工艺,双向编织玻璃纤维和矩形不锈钢钢丝网制备了10种不同丝径和孔间距的复合材料试件。研究了不同钢丝网参数对复合材料拉伸性能的影响,并结合数字图像相关技术揭示了其失效机制。研究结果表明,材料的变形在拉伸初始阶段受到钢丝网的约束,随着荷载的增加,试件被钢丝网分割为更多的应变单元,最后钢丝网和纤维发生相对滑移,一侧纤维发生断裂并向另一侧迅速撕裂开从而导致试件破坏,试件的失效全部为脆性失效。引入钢丝网显著提高了玻璃纤维-钢丝网增强复合材料的刚度、峰值荷载和极限应变等参数,相较于无钢丝网试件,极限荷载最大提升了61.18%,最大位移提升了37.17%;此外钢丝网在试件内表现出了良好的延性。研究结果为复合材料加固的工程应用提供了一定的参考。

Experimental testing of low-energy rockfall catch fence meshes

Flexible catch fences are widely used to protect infrastructure like railways, roads and buildings from rockfall damage. The wire meshes are the most critical components for catch fences as they dissipate most of the impact energy. Understanding their mechanical response is crucial for a catch fence design. This paper presents a new method for testing the wire meshes under rock impact. Wire meshes with different lengths can be used and the supporting cables can be readily installed in the tests. It is found that a smaller boulder causes more deformation localisation in the mesh. Longer mesh length makes the fence more flexible. Under the same impact condition, the longer mesh deforms more along the impact direction and shrinks more laterally. Supporting cables can reduce the lateral shrinkage of the mesh effectively. Most of the impact energy is dissipated by stretching of the wires.Wire breakage has not been observed.

基于无线Mesh接入服务技术的校园网设计与实现

无线Mesh网简称WMN,是一种新型的无线通信网络;这是一种高容量、高速率、多跳的分布式宽带无线网络.以某体育学院校园网工程为背景,对原有校园网进行分析,提出了全新的整体规划,包括各层交换机和路由器的配置、无线接入的配置等;设计中采用三层交换结构,即接入层、汇聚层和核心层,在各个层上采用相应的配置策略;新的设计提高了校园网数据交换速率和整体性能.

无线mesh网络中学习资源的最优复制策略

以移动学习中的课件点播为应用背景,提出了以连接代价最小的学习资源复制策略,将选择的最优资源预先复制到无线mesh网络(WMNs)中的骨干节点上,当学习者需要某一资源时,可通过Peer-to-Peer(P2P)方式,从最近的节点中获得所需学习资源,从而提高用户的连接速度和播放质量,同时缓解WMNs中网关节点的负载压力.针对所求问题是一个特殊的多维0-1背包问题,提出了一种改进的分布式遗传算法对问题进行了求解.仿真结果说明了改进算法的优越性.

船用洗涤塔除尘效率试验研究

针对船舶双燃料主机的废气除尘要求,综合成本、布置以及除尘效率需求,使用填料洗涤塔更加便捷。本文研究基于填料洗涤塔除尘效率的试验装置设计,通过引主机后的废气进入洗涤塔,使用离心泵抽取循环柜中的淡水在板式热交换器中进行换热后通过喷嘴喷淋至塔内,填料塔内设置规整填料、螺旋喷嘴喷淋、除雾器,使用滤纸烟度计测量该试验装置中洗涤塔在主机燃油和燃气模式下的除尘效率,设计两种不同的除尘结构试验装置,并在此基础上进行试验验证和对比,验证在不同喷淋水量、不同主机燃烧模式和不同除雾型式下的洗涤塔除尘效率,从而得到在燃油模式下更加适合应用的丝网除尘结构和适合的喷淋水量。