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圆管内变物性气体湍流阻力系数公式的理论推导 被引量:1
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作者 赵后剑 马安祥 +3 位作者 刘瑶 李晓伟 吴莘馨 牛风雷 《工程热物理学报》 EI CAS CSCD 北大核心 2021年第11期2960-2964,共5页
在气体湍流换热过程中,当壁面与主流流体存在较大换热温差时气体密度、黏度和导热系数等物性在换热截面内呈现剧烈变化。传统湍流阻力系数公式的推导过程均以常物性假定为前提,并未考虑变物性的影响。现有文献中考虑气体变物性效应的湍... 在气体湍流换热过程中,当壁面与主流流体存在较大换热温差时气体密度、黏度和导热系数等物性在换热截面内呈现剧烈变化。传统湍流阻力系数公式的推导过程均以常物性假定为前提,并未考虑变物性的影响。现有文献中考虑气体变物性效应的湍流阻力系数公式大多是采用拟合实验数据的方法获得。本文通过分析气体物性变化对壁面黏性尺度以及物性变化对无量纲速度分布中线性区和对数律区分界点的影响,给出了变物性气体湍流换热过程中无量纲速度的对数律分布公式。在速度分布公式的基础上推导出了变物性气体湍流阻力系数计算公式。所推导公式与经验关系式符合良好,且所推导公式对加热和冷却工况均适用。 展开更多
关键词 湍流 变物性气体 阻力系数 黏性底层 对数律层
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Optimization of HPVP-GTAW aluminum alloy process parameters for Al-Mg welded joints 被引量:1
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作者 欧阳瑞洁 从保强 +1 位作者 齐铂金 刘方军 《China Welding》 EI CAS 2014年第4期76-82,共7页
Optimization of hybrid ultrahigh frequency pulse variable polarity gas tungsten arc welding (HPVP-GTAW) process was carried out to obtain the optimum weld characteristics of 5AO6-HX4 aluminum-magnesium alloy sheets ... Optimization of hybrid ultrahigh frequency pulse variable polarity gas tungsten arc welding (HPVP-GTAW) process was carried out to obtain the optimum weld characteristics of 5AO6-HX4 aluminum-magnesium alloy sheets of 3 mm thickness. The square butt joints were produced by HPVP-GTA W process, the microstructure and mechanical properties were systematically investigated. It is observed that the process parameters influence the weld microstructure and mechanical properties significantly. Weld microstructure is mainly composed of grid a (A1) solid solution, with a large number of intermetallic ( Mg2Al3 ) precipitates distributed in the matrix. The amount of ~ ( Mg2Al3 ) precipitates has an obvious difference with different parameters. Compared with that of the base material, tensile strength of 5AO6-HX4 alloy welded joints has a certain reduction, as well as the elongation and reduction of area. The optimized welding process parameters for 5A06-HX4 alloy sheets are presented. 展开更多
关键词 ultrahigh frequency pulse current variable polarity gas tungsten arc welding aluminum alloy mechanical property
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