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蒸汽在过冷水中浸没射流凝结技术因其高效换热特性被广泛应用于陆地和海洋场景下的电力和核工业等许多工业领域中,但蒸汽凝结过程中汽液相界面变化会产生压力振荡。本文对起伏条件下不稳定射流的压力振荡特性进行了实验研究,获得了不同起伏参数对压力振荡特性的影响。结果表明,相比于静止条件下,不稳定射流在起伏运动下的压力振荡主频与压力振荡平均幅值更大,并且压力振荡主频和压力振荡平均幅值随着起伏幅值的增大而增大,随着起伏周期的增大而减小;起伏最大加速度幅度随着起伏周期的减小和起伏幅值的增大而增大,斯特劳哈尔数随着起伏最大附加加速度的增大而增大。 相似文献
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文章从原理及应用等方面介绍了研究材料在高温高压下物理结构变化的一种实验方法。借助该方法,可以比较方便地研究在100GPa-1000GPa压力下及几个电子伏特温度下材料的特性及内部结构变化情况。 相似文献
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人体成分无创光谱检测过程中,测量条件特别是探头压力造成的组织形变在一定程度上影响光谱测量结果。利用物理模型与仿真方法,定量分析了探头接触压力作用下皮肤组织应变,及光学参数与漫反射光谱变化。首先,在多层皮肤组织物理复合模型基础上,结合生物组织固液两相组成特性,定量分析了压力作用下各层皮肤组织形变大小以及成分变化。该模型将皮肤力学模型简化为固态弹性结构及包含于其中的牛顿流体,利用有限元方法,分别模拟不同压力作用下多层皮肤组织应变大小及时间特性,并根据各层组织体积及水含量变化,定量计算其散射系数及吸收系数改变。然后,利用Monte Carlo方法模拟压力作用前后光在组织中传输过程,定量分析了探头压力对漫反射光谱中所包含人体成分检测有效信息的影响。实验结果表明,在光纤探头接触压力作用下,人体皮肤组织中真皮层厚度变小,自由水体积减小,引起散射特性及光子传输路径改变,使得漫反射光谱中所包含的有效光谱信息下降。该研究结果为优化人体漫反射光谱测量策略,提高测量准确性以及重复性提供了参考。 相似文献
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《工程热物理学报》2021,42(5):1213-1223
为了研究水泵水轮机无叶区压力脉动特性,对某一电站水泵水轮机模型进行了试验,得到不同导叶开度下"S"特性及压力脉动特性。同时,利用ANSYS CFX对水泵水轮机19mm活动导叶开度下的不同工况进行了全流道非定常数值模拟,并分析了四种典型工况下水泵水轮机无叶区的压力脉动和内部流动。结果表明:水轮机工况P01,叶片吸力面附近流动分离较弱,无叶区的压力脉动较小;飞逸工况P05,流动分离加剧,形成了明显的旋涡,压力脉动较大;制动区工况P07,发生了明显的旋转失速,且频率为0.7f_n,流动呈现明显的不对称性,各流道的流量相差较大,压力脉动进一步增大;小流量工况P09,旋转失速消失,流动具有明显的对称性,压力脉动较小。该研究可为水泵水轮机的优化设计提供参考。 相似文献
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在高压、高应变率加载条件下,孪晶变形对材料的塑性变形具有重要的贡献,而目前孪晶对金属材料的动态屈服强度、冲击响应等的影响还没有被充分揭示.为此,本文考虑孪晶变形和晶粒碎化,针对铍(Be)材料在高应变率加载下的动态力学响应发展了含孪晶的热弹-黏塑性晶体塑性模型.经过和实验结果的对比,发现该模型可以更准确地预测Be材料在动态加载下,尤其是高压动态加载下的屈服强度.进一步,基于该塑性模型研究了Be材料在冲击加载下的准弹性卸载行为,结果表明剪切波速随着压力和剪应变的变化而发生变化是材料产生准弹性卸载现象的主要原因.此外,研究了冲击波卸载过程中Be材料孪晶的演化过程,发现Be材料卸载过程中也伴随着孪晶的产生. 相似文献
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Naofumi Ohtsu Akiko Nomura Masaoki Oku Toetsu Shishido Kazuaki Wagatsuma 《Applied Surface Science》2008,254(17):5336-5341
Oxidation behaviors of NiAl, Ni3Al, and FeAl under oxygen atmosphere at low pressures were studied by X-ray photoelectron spectroscopy (XPS). Clean surfaces of these aluminides were prepared by fracturing in an ultra high vacuum, and then the fractured surfaces were oxidized by exposing to high-purity oxygen at pressures up to 1.3 Pa without exposing to air. The oxides formed on NiAl and FeAl surfaces were Al2O3, whereas the oxide on Ni3Al was NiAl2O4. Aluminum, nickel, and iron on clean surfaces were oxidized even at a pressure of 1.3 × 10−6 Pa. The oxidation evolves with an increase in the pressure of oxygen, and further oxidation of aluminum occurs prior to that of nickel or iron. The oxidation behaviors under such oxygen atmosphere were similar to those of the aluminides oxidized in air, and these behaviors could be predicted from thermodynamic consideration. 相似文献
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Several spiral groove gas film face seals (SGFS) with different layouts are compared quantitatively to analyze their merits and faults and application behaviors. In addition, a parametric study on downstream mode SGFS is conducted to determine its optimal parameters under certain working conditions. In the computation of gas film pressure on the face, finite element method (FEM) is applied to adapt to complicated geometrical boundary. 相似文献
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Several spiral groove gas film face seals (SGFS) with different layouts are compared quantitatively to analyze their merits and faults and application behaviors. In addition, a parametric study on downstream mode SGFS is conducted to determine its optimal parameters under certain working conditions. In the computation of gas film pressure on the face, finite element method (FEM) is applied to adapt to complicated geometrical boundary. 相似文献
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Ming QiuK.M. Liew 《Physics letters. A》2011,375(23):2234-2238
Carrying on first-principles, the deformation effects on negative differential resistance (NDR) and rectifying behaviors of two cumulenic monatomic rings connected by polyyne and sandwiched between two Au electrodes are investigated. Interestingly, the number of obvious NDR whose peak-to-valley ratios increase from 1.24 to 5.16 is more than three and reverse rectification ratios also climb up from 1.42 to 7.89 with deformations increasing. Analysis of transmission spectra and frontier orbitals reveals that the response of different levels and resonant peaks, and transfer of the extended states to localized states of frontier orbital resonances under biases are responsible for these phenomena. Our works present a potential route to develop a multi-functional pressure device which has multi-peaks of NDR and rectifying behaviors. 相似文献
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The high pressure behaviors and electronic properties of (C6H6)n@SWCNT peapod structure with the different encapsulation densities are studied by the DFT calculation. The weak van der Waals interaction and electronic orbital hybridization interaction between the host and guest molecules are exhibited in the pressure lower and higher than 3 GPa, respectively. The encapsulation density of C6H6 molecules plays an important role in the structural deformation, the bonding behaviors, and the electronic orbital hybridization interaction of the considered four hybrid systems under the pressures. 相似文献
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