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Modification of premixed combustion in shear layers by grid turbulence

MU Kejin, WANG Yue, ZHANG Zhedian, NIE Chaoqun

《能源前沿（英文）》 2007年第1卷第2期页码 245-250 doi: 10.1007/s11708-007-0034-6

摘要： The influence of grid turbulence on the shear layer of a jet and the premixed flames embedded in it was investigated in the present study. The velocity field of the jet was measured by using hot-wire anemometry. It was found that grid turbulence reduced turbulence intensities in the shear layer and suppressed low frequency fluctuation. Moreover, the energy contained in small-scale fluctuation was increased and turbulence became homogeneous. The results indicate that grid turbulence inhibits the formation of a large-scale coherent structure in the shear layer. Flame temperature was measured by using a compensated fine-wire thermocouple. It was found that grid turbulence reduced low frequency fluctuation of the flame fronts, increased the small-scale wrinkles and elevated the mean temperature of the flame zone. The results show that grid turbulence can enhance and stabilize premixed flames in shear flow.

关键词： homogeneous fine-wire thermocouple temperature hot-wire anemometry premixed

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Process improvement in laser hot wire cladding for martensitic stainless steel based on the Taguchi method

Zilin HUANG,Gang WANG,Shaopeng WEI,Changhong LI,Yiming RONG

《机械工程前沿（英文）》 2016年第11卷第3期页码 242-249 doi: 10.1007/s11465-016-0397-7

摘要：

Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved by using a quantitative method. In this work, volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers. Laser deposition experiments with FV520B, one of martensitic stainless steels, were designed by using the Taguchi method. Four process variables, namely, laser power (P), scanning speed (V_s), wire feed rate (V_f), and wire current (I), were optimized based on the analysis of signal-to-noise (S/N) ratio. Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method. A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks, which resulted in a good metallurgical bonding interface.

关键词： process optimization Taguchi method signal-to-noise (S/N) ratio volumetric defect ratio laser hot wire cladding

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Elevated temperature creep model of parallel wire strands

《结构与土木工程前沿（英文）》页码 1060-1071 doi: 10.1007/s11709-023-0981-y

摘要： Parallel wire strands (PWSs), which are widely used in prestressed steel structures, are typically in high-stress states. Under fire conditions, significant creep effects occur, reducing the prestress and influencing the mechanical behavior of PWSs. As there is no existing approach to analyze their creep behavior, this study experimentally investigated the elevated temperature creep model of PWSs. A charge-coupled camera system was incorporated to accurately obtain the deformation of the specimen during the elevated temperature creep test. It was concluded that the temperature level had a more significant effect on the creep strain than the stress level, and 450 °C was the key segment point where the creep rate varied significantly. By comparing the elevated temperature creep test results for PWSs and steel strands, it was found that the creep strain of PWSs was lower than that of steel strands at the same temperature and stress levels. The parameters in the general empirical formula, the Bailey–Norton model, and the composite time-hardening model were fitted based on the experimental results. By evaluating the accuracy and form of the models, the composite time-hardening model, which can simultaneously consider temperature, stress, and time, is recommended for use in the fire-resistance design of pre-tensioned structures with PWSs.

关键词： parallel wire strands experimental study elevated temperature creep model

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Preconcentration of trace elements by adsorption onto a niobium wire for electrothermal atomization atomic

Satoshi KANECO, Hiroaki KITANAGA, Hideyuki KATSUMATA, Tohru SUZUKI

《化学科学与工程前沿（英文）》 2012年第6卷第4期页码 432-435 doi: 10.1007/s11705-012-1219-z

摘要： In the present work, a new preconcentration method of trace elements by adsorption onto a niobium wire has been developed for electrothermal atomization atomic absorption spectrometry (ETAAS) with a tungsten tube atomizer. Detection limits (pg·mL ) by this method combined with ETAAS were 45 for bismuth, 7.0 for cadmium, 20 for copper, 1.3 for gold, 36 for lead, 65 for manganese, 9.5 for rhodium and 19 for silver.

关键词： preconcentration adsorption onto niobium wire electrothermal atomization atomic absorption spectrometry tungsten tube atomizer trace elements

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

《化学科学与工程前沿（英文）》页码 1672-1680 doi: 10.1007/s11705-022-2205-8

摘要： 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 30.02–77.29 μm, and that of hydrophobic wire mesh is 41.76–237.37 μm. 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.

关键词： stainless steel wire mesh computational fluid dynamics surface wettability liquid film impacting

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A hot future for cool materials

《能源前沿（英文）》 2023年第17卷第4期页码 447-449 doi: 10.1007/s11708-022-0854-4

摘要： The widespread need to pump heat necessitates improvements that will increase energy efficiency and, more generally, reduce environmental impact. As discussed at the recent Calorics 2022 Conference, heat-pump devices based on caloric materials offer an intriguing alternative to gas combustion and vapor compression.

关键词： magnetocaloric electrocaloric mechanocaloric elastocaloric barocaloric

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Experimental study on wire breakage detection by acoustic emission

Limin SUN, Ji QIAN

《结构与土木工程前沿（英文）》 2011年第5卷第4期页码 503-509 doi: 10.1007/s11709-011-0132-8

摘要： This paper experimentally investigated wire breakage detection in a steel cable by acoustic emission (AE) waveform. In the experiments, the attenuation laws of waveform amplitudes were discussed based on stress wave propagation in the wire, which was generated by kNocking and wire breakage. Then the wave velocity was calculated based on the reach time of the stress wave from each sensor. Finally, based on the waveform attenuation laws and the linear position method, the amplitude and energy of the source were confirmed through the measured waveform to identify the source category. The experimental results illustrated that the stress wave from different sources has a different frequency spectrum, and the amplitude attenuation factor varied with the stress wave frequency; high frequency waves had a greater attenuation factor. Compared with the other source, the wire breakage source contained a much higher energy, and thus, the wire breakage signal can be distinguished from the other source by comparing the non-attenuation energy at the source position.

关键词： acoustic emission (AE) waveform wire breakage attenuation factor wave velocity

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游离磨料多股线线锯切割实验研究

王金生,姚春燕,彭伟,金鑫, 陈世杰

《中国工程科学》 2012年第14卷第11期页码 94-98

摘要：

游离磨料线锯切割是将磨浆中的磨粒通过一定速度的细钢丝线带入切割区域，达到去除工件材料的目的。多股线由多根细金属线绕制而成，表面具有很多凹槽，与钢丝线光滑表面相比，可以输送更多的磨粒进入切割区域，从而提高切割效率。应用0.25 mm的多股线和0.25 mm的钢丝线对光学玻璃K9进行切割对比实验，结果表明，在相同工艺条件下，多股线的切割效率和表面粗糙度均优于钢丝线，但切缝宽度大于钢丝线。

关键词：线锯游离磨料加工切割效率

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

Pravin Kumar Venkat Rao PADALU; Yogendra SINGH

《结构与土木工程前沿（英文）》 2022年第16卷第4期页码 478-505 doi: 10.1007/s11709-022-0817-1

摘要： 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.

关键词： unreinforced masonry seismic in-plane and out-of-plane forces pier analysis finite element modelling splint and bandage technique with wire mesh

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Wheel tracking methods to evaluate moisture sensitivity of hot-mix asphalt mixtures

Jie HAN,Harihar Shiwakoti

《结构与土木工程前沿（英文）》 2016年第10卷第1期页码 30-43 doi: 10.1007/s11709-016-0318-1

摘要： Existing test methods to determine moisture sensitivity in hot-mix asphalt (HMA) mixtures are time consuming and inconsistent. This research focused on wheel tracking devices to evaluate moisture sensitivity. The Asphalt Pavement Analyzer (APA) and the Hamburg Wheel Tracking Device (HWTD) were used for this research. Compacted cylindrical samples were fabricated using a Superpave Gyratory compactor. This study selected two most commonly used mixtures, SM-12.5A with PG 64-22 binder in overlay projects and SM-19A mixtures with PG 64-22 binder for major modification projects at Kansas Department of Transportation. Test results show that APA tests could induce stripping in most samples without any anti-stripping agent, which could be identified visually. However, APA results did not indicate any stripping inflection point while the HWTD results showed stripping inflection points, which are important to identify stripping potential of mixtures. The APA results show that wet tests are severe at lower temperatures. The HWTD results show improvement in the performance using anti-stripping agents at later stage. The HWTD test is more effective as a rapid test method in case of determining moisture sensitivity. Laboratory results from this study should be verified and correlated with field performance.

关键词： hot-mix asphalt moisture sensitivity rutting wheel tracking test

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Survey of thermal comfort in residential buildings under natural conditions in hot humid and cold wet

Changhai PENG

《结构与土木工程前沿（英文）》 2010年第4卷第4期页码 503-511 doi: 10.1007/s11709-010-0095-1

摘要： Comfort standards (ISO 7730, ASHRAE 55) specify the exact physical criteria for producing acceptable thermal environments, such as temperature, air movement, and humidity limits. These, however, are often difficult to comply with, particularly in hot humid and cold wet seasons in Nanjing, China. Changing expectations of comfort is important in evaluating comfort, since naturally conditioned buildings in Nanjing are not typically air-conditioned. For this objective, a field study was conducted during the summer of 2000 and the winter of 2001. A total of 600 participants each answered a subjective questionnaire. Analyzing these field data shows that in natural conditions, the influence of gender and age on people’s thermal sensations is insignificant compared with six main variables. In addition, people’s thermal discomfort rapidly increases along with growth in relative humidity. Further, the variation of people’s hot or cold sensations is in proportion to that of air movement, and the effect in winter is greater than that in summer. The range of acceptable temperatures in hot humid and cold wet Nanjing is between 14.14°C and 29.42°C.

关键词： thermal comfort naturally conditioned hot humid cold wet Nanjing

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Experimental research on the mechanical property of prestressing steel wire during and after heating

ZHENG Wenzhong, HU Qiong, ZHANG Haoyu

《结构与土木工程前沿（英文）》 2007年第1卷第2期页码 247-254 doi: 10.1007/s11709-007-0031-1

摘要： The mechanical property of prestressing steel wire during and after heating is the key factor in the design of fire resistance and after-fire damage evaluation of prestressed structures. Tensile experiment of 16 prestressing steel wires ( = 1770 N/mm, = 5 mm, low relaxation of stress) at high temperature and tensile experiment of 14 prestressed steel wires after heating are carried out. According to the experiment, the shapes of stress-strain curves of steel wire at high temperature go smooth and the mechanical property indexes of the steel wire such as strength, modulus of elasticity, etc., degenerate continuously as temperature increased. According to the experiment after heating, the mechanical property of steel wire varies little when the highest temperature that the steel wire has ever been heated to is lower than 300vH; while the stress-strain curves of steel wire become more ductile and the mechanical property indexes of the steel wire degenerate gradually when the highest temperature is higher than 300vH. By applying the theory of viscoelastic mechanics, stress-strain curves of steel wire at high temperatures without loading rate influence are obtained. The law of mechanical property indexes of the wire is presented. The mathematical models of the stress-strain relationship of the pre-stressed steel wire are established. All can serve as basic data for the analysis of fire resistance and after-fire damage evaluation of pre-stressed structures.

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A review on research and development of iron-based sorbents for removal of hydrogen sulfide from hot

Jianglong YU, Liping CHANG, Fan LI, Kechang XIE

《化学科学与工程前沿（英文）》 2010年第4卷第4期页码 529-535 doi: 10.1007/s11705-010-0519-4

摘要： In poly-generation and integrated gasification-combined cycle (IGCC) systems for clean energy conversion, it is essential to remove impurities such as sulfur species from hot coal gases prior to entering the subsequent units. This paper provides a comprehensive review on previous studies on high temperature removal of hydrogen sulfide from high temperature coal gases using iron-based sorbents. A two-step desulphurization process for hot coal gas cleanup is highlighted, which is integrated with direct production of elemental sulfur during regeneration of iron-based sorbents in the primary desulphurization step. Different kinetic modeling approaches for sulfidation and regeneration were compared. Limited research on activated carbon supported sorbents was also briefly summarized.

关键词： hot coal gas cleanup iron-based sorbents sulfidation regeneration sulphur recovery

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Desulfurization performance of iron-manganese-based sorbent for hot coal gas

Xiurong REN, Weiren BAO, Fan LI, Liping CHANG, Kechang XIE

《化学科学与工程前沿（英文）》 2010年第4卷第4期页码 429-434 doi: 10.1007/s11705-010-0504-y

摘要： A series of iron-manganese-based sorbents were prepared by co-precipitation and physical mixing method, and used for H S removal from hot coal gas. The sulfidation tests were carried out in a fixed-bed reactor with space velocity of 2000 h (STP). The results show that the suitable addition of manganese oxide in iron-based sorbent can decrease H S and COS concentration in exit before breakthrough due to its simultaneous reaction capability with H S and COS. Fe O and MnO are the initial active components in iron-manganese-based sorbent, and FeO and Fe are active components formed by reduction during sulfidation. The crystal phases of iron affect obviously their desulfurization capacity. The reducibility of sorbent changes with the content of MnO in sorbent. S7F3M and S3F7M have bigger sulfur capacities (32.68 and 32.30 gS/100 g total active component), while S5F5M has smaller sulfur capacity (21.92 gS/100 g total active component). S7F3M sorbent has stable sulfidation performance in three sulfidation-regeneration cycles and no apparent structure degradation. The sulfidation performance of iron- manganese-based sorbent is also related with its specific surface area and pore volume.

关键词： iron-manganese-based sorbent sulfidation performance regeneration hot coal gas

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Impingement of hollow cone spray on hot porous medium

ZHAO Zhiguo, XIE Maozhao

《能源前沿（英文）》 2008年第2卷第3期页码 273-278 doi: 10.1007/s11708-008-0048-8

摘要： To have a good understanding of the formation of homogenous mixture in a porous medium engine, the interaction between hollow cone spray and hot porous medium was studied numerically by using an improved version of KIVA-3V code. The improved KIVA-3V code is incorporated with an impingement model, heat transfer model and linearized instability sheet atomization (LISA) model to simulate the hollow cone spray. The reasonability of the impingement model and heat transfer model was validated. With a simple model to describe the structure of the porous medium, the interaction between hollow cone spray and hot porous medium was simulated under different ambient pressures and spray cone angles. Computational results show that the fuel spray could be divided into smaller ones, which provides conditions for the quick evaporation of fuel droplets and the mixing of fuel vapor with air. Differences in ambient pressure and spray cone angle affect the distribution of droplets in the porous medium.

关键词： improved version simple impingement atomization hollow