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排序方式: 共有176条查询结果,搜索用时 31 毫秒
1.
为了研究不同槽深下的周向槽对压气机稳定性的影响,由于带槽结构下的转子37失速类型仍是叶尖失速,但是带周向槽结构的主要失速因素是叶尖间隙的泄漏涡,且不同轴向位置的周向槽所造成的损失也是不同的。为解决上述问题,利用NUMECA软件和系统的数值模型对某跨音速压气机进行了数值仿真,对三类带周向槽结构的计算结果进行了分析,结果表明,设计中讨论最佳槽深应先给定效率损失要求,并且应以研究最佳槽位置的选择为主。对压气机周向槽处理机匣的设计,不一定要设计涉及整个叶片的处理机匣。对于跨音速压气机在叶尖泄漏涡严重的位置优化设计,可提高压气机稳定性能。 相似文献
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从经济和技术角度分析火电厂高温高压管道焊缝宜采用的坡口形式,并对各种坡口形式的焊条用量估算推导出经验公式. 相似文献
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为了提高重载数控机床静压转台的承载能力和油膜刚度,提出了一种具有多环形流道油腔和阻尼型封油边结构的新型静压油垫,并对其性能进行了研究.在对静压油垫结构优化设计的基础上,利用CFD(computationalfluid dynamics)数值仿真技术,采用二维轴对称流动模型对新型结构静压油垫的流场特性进行了仿真分析,得到了新型静压油垫的内部流场特性,计算出油垫的承载能力和油膜刚度,并与单腔体、单平面封油边结构的静压油垫进行了对比.研究表明:新型静压油垫能通过在阻尼流道和阻尼槽内形成紊流,增加流动液阻,实现压力增益,并可在阻尼槽处产生局部静压效应,从而使新型结构静压油垫的承载能力和油膜刚度较传统结构静压油垫有所提高;此外,采用CFD技术有助于对复杂结构的静压油垫进行优化设计与性能计算,从而提高设计效率和计算准确性. 相似文献
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《Current Opinion in Solid State & Materials Science》2016,20(5):231-239
Recent findings about the role of the grain boundary energy in complexion transitions are reviewed. Grain boundary energy distributions are most commonly evaluated using measurements of grain boundary thermal grooves. The measurements demonstrate that when a stable high temperature complexion co-exists with a metastable low temperature complexion, the stable complexion has a lower energy. It has also been found that the changes in the grain boundary energy lead to changes in the grain boundary character distribution. Finally, recent experimental observations are consistent with the theoretical prediction that higher energy grain boundaries transform at lower temperatures than relatively lower energy grain boundaries. To better control microstructures developed through grain growth, it is necessary to learn more about the mechanism and kinetics of complexion transitions. 相似文献
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Tianyang Chen Jinghu Ji Yonghong Fu Xiping Yang Hao Fu Lunan Fang 《Ceramics International》2021,47(16):23162-23180
The performance of mechanical seals can be improved by using multi-scale composite textures with spiral grooves and micro-dimples, but without a clear texture function mechanism, it is difficult to optimize the textures on the sealing surface. This research established a mathematical model based on the mass-conservative JFO cavitation boundary to analyze the mechanical seal performance of multi-scale composite micro-textures. We use the multi-grid method for numerical solutions, investigate the hydrodynamic lubrication characteristics of composite-textured mechanical seals, and inspect the coupling effect of micro-dimples and spiral grooves. We also analyzed the influence of the geometrical parameters of composite textures on the sealing performance and optimized the sealing surface textures using theoretical analysis. The numerical analysis showed that the multi-scale composite-textured mechanical seal produced a coupling effect between the micro-dimples and spiral grooves, which improved the lubrication of the sealing pair. Eventually, C/SiC mechanical seal bench tests confirmed the tribological improvement of composite textures compared with the un-textured seal under various sealing liquid pressures and rotation speeds. Through comparing the Stribeck curve, the multi-scale composite textured C/SiC mechanical seals have a lower and more stable friction torque than the un-textured. 相似文献
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Seung Ho Lee Young Bok Kang Wonsuk Jung Yousung Jung Soohyun Kim Hongseok Noh 《Nanoscale research letters》2013,8(1):487
While flow-induced voltage over a graphene layer has been reported, its origin remains unclear. In our previous study, we suggested different mechanisms for different experimental configurations: phonon dragging effect for the parallel alignment and an enhanced out-of-plane phonon mode for the perpendicular alignment (Appl. Phys. Lett. 102:063116, 2011). In order to further examine the origin of flow-induced voltage, we introduced a transverse flow component by integrating staggered herringbone grooves in the microchannel. We found that the flow-induced voltage decreased significantly in the presence of herringbone grooves in both parallel and perpendicular alignments. These results support our previous interpretation. 相似文献