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Field test on temperature field and thermal stress for prestressed concrete box-girder bridge

Baoguo CHEN, Rui DING, Junjie ZHENG, Shibiao ZHANG

《结构与土木工程前沿（英文）》 2009年第3卷第2期页码 158-164 doi: 10.1007/s11709-009-0002-9

摘要： A field test was conducted to investigate the distribution of temperature field and the variation of thermal stress for a prestressed concrete (PC) box-girder bridge. The change of hydration heat temperature consists of four periods: temperature rising period, constant temperature period, rapid temperature fall period and slow temperature fall period. The peak value of hydration heat temperature increases with the increasing casting temperature of concrete; the relation between them is approximately linear. According to field tests, the thermal stress incurred by hydration heat may induce temperature cracks on the PC box-girder. Furthermore, the nonlinear distribution of temperature gradient and the fluctuation of thermal stress induced by exposure to sunlight were also obtained based on continuous in-situ monitoring. Such results show that the prevailing Chinese Code (2004) is insufficient since it does not take into account the temperature gradient of the bottom slab. Finally, some preventive measures against temperature cracks were proposed based on related studies. The conclusions can provide valuable reference for the design and construction of PC box-girder bridges.

关键词： box-girder bridge field test hydration heat temperature field temperature gradient thermal stress

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Study on the measurement of temperature field using laser holographic interferometry

Jinrong ZHU, Suyi HUANG, Wei LV, Huaichun ZHOU

《能源前沿（英文）》 2011年第5卷第1期页码 120-124 doi: 10.1007/s11708-010-0107-9

摘要： The temperature field of an axisymmetric ethylene diffusion flame is measured using laser holographic interferometry. Temperature field inversion is completed with the aid of components distribution divided from numerical simulation of combustion and air components assumption. Error analysis of key steps is conducted using the theoretical formula of interference temperature measurement and characteristic structure of fringes obtained from optical simulation. Based on the calculation and analysis, air components assumption will not cause significant error in the low temperature region but will result in high error in the high temperature region. Moreover, the small error in environmental temperature measurement transfer to a high temperature range will expand more than tenfold. Results of temperature measurement using air components assumption relative to combustion simulation require the greatest amendment amounting to seven percent.

关键词： temperature field flame error analysis holographic interferometry

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Temperature field simulation of laser homogenizing equipment

Juanjuan WANG, Yunshan WANG, Fudong ZHU

《机械工程前沿（英文）》 2009年第4卷第1期页码 49-52 doi: 10.1007/s11465-009-0005-1

摘要： The laser homogenizing equipment was devised using the ring scanning principle. Its working principle is explained. A laser scanning ring facula is obtained when the laser beam goes through the equipment’s optical system rotating with high-frequency. The scanning ring facula’s mathematic model is established based on the temperature field’s superposing principle. The ring facula’s light intensity distribution and temperature distribution characteristics are achieved by simulating its temperature field. By studying the effect of parameters on the temperature field, the best parameter can be found. Results show that favorable temperature distribution characteristics can be attained by choosing appropriate parameters, and even the thermal effect can be realized by utilizing the circumference power compensating for the heat exchange lost in the horizontal direction. The uniform hardness layer and better process quality can be attained using the ring facula optimized for metal laser heat treatment.

关键词： laser homogenizing technology laser scanning ring facula temperature field

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NiBO (B = Mn or Co) catalysts for NH-SCR of NO at low-temperature in microwave field

《环境科学与工程前沿（英文）》 2023年第17卷第8期 doi: 10.1007/s11783-023-1696-y

摘要：

● Microwave-assisted catalytic NH₃-SCR reaction over spinel oxides is carried out.

关键词： Microwave field Spinel oxides NO_x Selective catalytic reduction

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新型PB-PSOI器件表面电场和温度分布模型研究

孙伟锋,高珊,陆生礼,陈军宁

《中国工程科学》 2009年第11卷第11期页码 82-87

摘要：

根据泊松方程和热扩散方程提出了新型PB-PSOI 器件漂移区的二维表面电场分布模型和温度分布模型，模型计算结果与Medici模拟结果相一致。根据所提出的模型，重点研究了埋氧化层厚度及长度对漂移区表面电场分布和温度分布的影响，最后给出了PB-PSOI 器件的埋氧化层厚度和长度的优化设计方法。

关键词： PB-PSOI 表面电场温度分布埋氧化层

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Modeling the gas flow in a cyclone separator at different temperature and pressure

Gujun WAN, Guogang SUN, Cuizhi GAO, Ruiqian DONG, Ying ZHENG, Mingxian SHI

《化学科学与工程前沿（英文）》 2010年第4卷第4期页码 498-505 doi: 10.1007/s11705-010-0502-0

摘要： The gas flow field in a cyclone separator, operated within a temperature range of 293 K – 1373 K and a pressure range of 0.1 – 6.5 MPa, has been simulated using a modified Reynolds-stress model (RSM) on commercial software platform FLUENT 6.1. The computational results show that the temperature and pressure significantly influence the gas velocity vectors, especially on their tangential component, in the cyclone. The tangential velocity decreases with an increase in temperature and increases with an increase in pressure. This tendency of the decrease or increase, however, reduces gradually when the temperature is above 1000 K or the pressure goes beyond 1.0 MPa. The temperature and pressure have a relatively weak influence on the axial velocity profiles. The outer downward flow rate increases with a temperature increase, whereas it decreases with a pressure increase. The centripetal radial velocity is strong in the region of 0 – 0.25 below the vortex finder entrance, which is named as a short-cut flow zone in this study. Based on the simulation results, a set of correlations was developed to calculate the combined effects of temperature and pressure on the tangential velocity, the downward flow rate in the cyclone and the centripetal radial velocity in the short-cut flow region underneath the vortex finder.

关键词： cyclone separator high temperature high pressure flow field numerical simulation

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Field measurements on microclimate in residential community in Guangzhou, China

Zhuolun CHEN, Lihua ZHAO, Qinglin MENG, Changshan WANG, Yongchao ZHAI, Fei WANG,

《结构与土木工程前沿（英文）》 2009年第3卷第4期页码 462-468 doi: 10.1007/s11709-009-0066-6

摘要： Taking a certain housing in Guangzhou as an example, we conduct the field measurement of the microclimate at fixed points for air temperature, relative humidity, black globe temperature and wind speed, etc. We investigate the effects of manmade lake, shade of trees and ground surface character on outdoor thermal environment, and make a quantitative analysis on the weighting position of the landscape design factors in design behavior. The study intends to explore a method to improve the thermal environment of residential quarters by changing the corresponding factors.

关键词： microclimate outdoor thermal environment air temperature black globe temperature wind speed

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典型高温地热系统——羊八井热田基本特征

多吉

《中国工程科学》 2003年第5卷第1期页码 42-47

摘要：

羊八井热田是属于陆陆碰撞板缘非火山型高温地热田。热田是由3个不同能的热储层构成，即浅层、深部第一和第二热储层，实质上它们属同一个水力系统，是一个完整的地热系统的不同部位。浅层热储由第四系松散沉积物及部分基岩风化壳构成，其埋深在地表以下180～280 m，热储温度130～173℃，水质类型为C1^--HCO₃^--Na⁺型水，属深部热流体与冷水混合的产物，流体以液相为主。深部热储由变质杂岩体中的滑离断层系构造空间构成，属基岩裂隙型脉状或带状热储，其中深部第一热储埋深为950～1 350 m，最高温度259.6 ℃；深部第二热储位于1 850 m深，热储最高温度可达329.8 ℃，深部热流体水质类型均属C1^--Na⁺ 型，气体组份中CO₂占主导地位。

关键词：高温地热热储层成因羊八井西藏

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Full-scale site evaluation of ventilation expressway embankments underlain by warm permafrost along the Gonghe−Yushu Expressway

《结构与土木工程前沿（英文）》页码 1047-1059 doi: 10.1007/s11709-023-0034-6

摘要： Ventilation embankments, including those with forced ventilation, natural ventilation, and combination of these, were adopted for the construction of the Gonghe−Yushu Expressway in warm permafrost areas. To evaluate the actual thermal performance of ventilation embankment in the Qinghai−Tibet Plateau, four types of ventilation embankments were selected as objects, and their long-term thermal characteristics were analyzed based on monitoring data. It was found that: 1) under the strong scale effect of a wide embankment, the crushed-rock embankment (CRE) was warming up and the permafrost table was declining year by year. Meanwhile, the combined ventilated slab and CRE and ventilated ducts embankment can effectively decrease the ground temperature and raise permafrost table in the year with a colder winter; 2) transverse temperature difference caused by the shady–sunny slope effect existed in all the four embankments. However, it was weakened by the combined ventilated slab and CRE and the ventilated ducts embankment due to their stronger cooling effect; and 3) the pre-existing embankment had a remarkable thermal disturbance to the adjacent newly-built embankment, so a reasonable embankment spacing should be considered in practical engineering. These findings would provide a reference for construction of expressway embankments in permafrost regions.

关键词： warm permafrost expressway ventilation embankments temperature field

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Modelling autogenous expansion for magnesia concrete in arch dams

JIN Feng, LUO Xiaoqing, ZHANG Chuhan, ZHANG Guoxin

《结构与土木工程前沿（英文）》 2008年第2卷第3期页码 211-218 doi: 10.1007/s11709-008-0025-7

摘要： Magnesia Concrete is a kind of expansive concrete used in Chinese hydraulic engineering more and more widely. To evaluate the effects of autogenous expansion on the stresses of arch dams, a simple model of autogenous expansion for Magnesia Concrete in dam engineering is presented. This model is based on three assumptions: 1) the total amount of autogenous expansion of Magnesia Concrete is related only to the properties of materials and mixing of concrete; 2) the autogenous expansion of Magnesia Concrete is irreversible due to the irreversibility of hydration reaction of Magnesia in the concrete; 3) the autogenous expansion strain rates of Magnesia Concrete bear a relation between temperature and residual Magnesia per unit volume of concrete. The model is verified by some experimental data of autogenous expansion of Magnesia Concrete and field-measured data of an arch dam in China. Embedded into finite element arch dam simulation software, this model is employed to simulate the effects of autogenous expansion of Magnesia Concrete in hydraulic engineering.

关键词： field-measured irreversibility temperature irreversible element arch

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Influence of the field humiture environment on the mechanical properties of 316L stainless steel repaired

Lianzhong ZHANG, Dichen LI, Shenping YAN, Ruidong XIE, Hongliang QU

《机械工程前沿（英文）》 2018年第13卷第4期页码 513-519 doi: 10.1007/s11465-018-0503-0

摘要：

The mechanical properties of 316L stainless steel repaired with Fe314 under different temperatures and humidities without inert gas protection were studied. Results indicated favorable compatibility between Fe314 and 316L stainless steel. The average yield strength, tensile strength, and sectional contraction percentage were higher in repaired samples than in 316L stainless steel, whereas the elongation rate was slightly lower. The different conditions of humiture environment on the repair sample exerted minimal influence on tensile and yield strengths. The Fe314 cladding layer was mainly composed of equiaxed grains and mixed with randomly oriented columnar crystal and tiny pores or impurities in the tissue. Results indicated that the hardness value of Fe314 cladding layer under different humiture environments ranged within 419–451.1 HV_0.2. The field humiture environment also showed minimal impact on the average hardness of Fe314 cladding layers. Furthermore, 316L stainless steel can be repaired through laser cladding by using Fe314 powder without inert gas protection under different temperatures and humidity environments.

关键词： laser cladding repaired performance tensile strength temperature and humidity environment

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新疆煤田火区现状调查研究——小尺度区域热辐射信息分析

钟茂华,符泰然,胡忠斌

《中国工程科学》 2010年第12卷第1期页码 12-17

摘要：

开展煤田火区现状调查，研究其对区域气候变化、生态响应系统的影响是评估自然灾害研究中的重要方面。选择新疆部分煤田火区进行了实地考察，开展了小尺度区域热辐射信息分析，依据现场实测资料分析，给出煤田热隐患状态的适度评定。分析结果表明：小尺度区域热辐射测量方法可用于判别已灭煤田火区的灭火效果分析及新形成火区探测；对于正在燃烧的煤田火区可判断火区的范围并为灭火提供参考依据。

关键词：煤田火区热辐射信息温度小尺度热像仪

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预制拼装箱梁现浇横隔梁水化热分析与控制研究

陈扬,钟瑶,郑开启,沈斌,孟少平

《中国工程科学》 2013年第15卷第8期页码 99-103

摘要：

在节段预制拼装桥梁的墩顶节段，常常采用后浇横隔梁的方式来减轻吊装重量。后浇横隔梁在体量上属于大体积混凝土，混凝土水化热问题会引起一些部位拉应力过大，如控制措施不合理，往往会导致预制梁段在施工阶段的开裂。本文结合南京长江第四大桥的引桥工程，基于三维瞬态温度场理论，利用通用有限元程序ANSYS对墩顶梁段现浇块的水化热效应进行了数值仿真，研究箱梁水化热温度场和应力场的分布规律。分析结果表明，水化热引起的箱梁腹板外侧拉应力水平足以导致混凝土开裂，在水化热测试试验中也观测到了箱梁腹板外侧的纵向微裂缝，与分析相符。在研究水化热温度场和应力场分布规律的基础上，进行了控制水化热温度应力的措施研究，在实桥施工中证实是切实有效的。

关键词：混凝土箱梁水化热温度场应力场裂缝

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Numerical simulation of bituminous coal combustion in a full-scale tiny-oil ignition burner: influence of excess air ratio

Zhengqi LI, Chunlong LIU, Xiang ZHANG, Lingyan ZENG, Zhichao CHEN

《能源前沿（英文）》 2012年第6卷第3期页码 296-303 doi: 10.1007/s11708-012-0191-0

摘要： The progression of ignition was numerically simulated with the aim of realizing a full-scale tiny-oil ignition burner that is identical to the burner used in an 800 MWe utility boiler. The numerical simulations were conducted for four excess air ratios, 0.56, 0.75, 0.98 and 1.14 (corresponding to primary air velocities of 17, 23, 30 and 35 m/s, respectively), which were chosen because they had been used previously in practical experiments. The numerical simulations agreed well with the experimental results, which demonstrate the suitability of the model used in the calculations. The gas temperatures were high along the center line of the burner for the four excess air ratios. The flame spread to the burner wall and the high-temperature region was enlarged in the radial direction along the primary air flow direction. The O concentrations for the four excess air ratios were 0.5%, 1.1%, 0.9% and 3.0% at the exit of the second combustion chamber. The CO peak concentration was very high with values of 7.9%, 9.9%, 11.3% and 10.6% for the four excess air ratios at the exit of the second combustion chamber.

关键词： numerical simulation tiny-oil ignition burner pulverized coal temperature field

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Recent progress in electric-field assisted combustion: a brief review

《能源前沿（英文）》 2022年第16卷第6期页码 883-899 doi: 10.1007/s11708-021-0770-z

摘要： The control of combustion is a hot and classical topic. Among the combustion technologies, electric-field assisted combustion is an advanced techno-logy that enjoys major advantages such as fast response and low power consumption compared with thermal power. However, its fundamental principle and impacts on the flames are complicated due to the coupling between physics, chemistry, and electromagnetics. In the last two decades, tremendous efforts have been made to understand electric-field assisted combustion. New observations have been reported based on different combustion systems and improved diagnostics. The main impacts, including flame stabilization, emission reduction, and flame propagation, have been revealed by both simulative and experimental studies. These findings significantly facilitate the application of electric-field assisted combustion. This brief review is intended to provide a comprehensive overview of the recent progress of this combustion technology and further point out research opportunities worth investigation.

关键词： electric field combustion flame stabilization emission reduction flame propagation