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《工程热物理学报》2015,(12)
以单级蜗壳式离心泵为研究对象,基于RANS进行了全流场的非定常数值计算,探讨了叶轮的非定常流动特征,重点分析了叶轮出口沿轴向变化的圆周面流域内各节点的压力分布特性。结果表明:在叶片压力面及叶片后缘尾迹区发生了剧烈的湍流脉动现象;不同工况下叶轮出口圆周方向的压力系数C_p均在隔舌附近产生极值;额定工况Q/Q_N=1时,叶轮出口圆周方向的压力系数C_p呈稳定周期性分布,随着工况的改变,压力系数C_p沿蜗壳周向分布不均匀性增加;小流量工况下叶轮流域内发生了明显的流动分离现象,流道内产生了较大尺度的分离涡,破坏了叶轮出口圆周方向压力系数C_p的周期性分布特性;叶轮出口圆周压力系数C_p沿中截面两侧的流域内几乎对称分布;在Q/Q_N=0.2小流量工况下,压力脉动频谱图低频段内出现了较多复杂的激励信号,认为这与流域内的分离涡结构具有一定关联。 相似文献
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多翼离心风机的三维数值分析 总被引:14,自引:1,他引:13
本文对一前弯多翼离心风机的内流场进行了三维数值分析。结果显示蜗壳内部的最大压力沿着轴线方向分布在不同的圆周位置,叶轮内部蜗舌上游区域存在着进口旋涡,蜗舌附近存在着明显的从叶片出口到进口的逆向回流,蜗舌间隙中存在着间隙涡,本文同时给出了一些典型位置上的速度和静压沿轴向的分布曲线,为验证本计算方法的可靠性,计算的流量和压力特性曲线和实验结果进行了比较,吻合良好。 相似文献
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切线泵整机多相位定常流动数值模拟 总被引:6,自引:2,他引:4
本文对一单级切线泵在设计工况进行了多相位定常流动数值模拟,分析了由于叶轮与蜗壳相对位置的变化引起的泵的扬程、叶轮流道内的质量流量、速度场、压力场的变化规律。计算表明,切线泵内流场非常复杂,整机多相位定常流动数值模拟的结果实际上是泵内流场非定常特性在定常计算中的反映,其内部流动呈周期性变化,叶轮流道在不同的位置流动情况差别很大。本次计算为进一步提高切线泵性能、减少水力损失提供了一定的理论依据。 相似文献
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开式和闭式离心泵进口回流的研究 总被引:6,自引:1,他引:5
利用毕托管对闭式和开式不同叶顶间隙的离心泵叶轮进口流场进行了动态测试,另外对开式叶轮吸入盖上的静压分布也进行了动态测试,并对叶轮流道内流场进行了可视化观察,弄清了小流量工况下叶片间的回流分布情况及上述不同叶轮对回流发生的影响及其原因。 相似文献
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离心叶轮内部三维湍流流场的数值分析 总被引:7,自引:0,他引:7
本文应用k-ε湍流模型在贴体曲线坐标系下结合SIMPLEC算法对Ghost离心叶轮内的湍流流场进行了求解。作者采用速度的阶变物理分量作为求解变量,在非交错网格上对单元体的界面流通量作特殊插值,以抑制不合理的波动压力场。计算结果与实测值吻合良好,揭示了叶轮出口的"射流-尾迹"结构和二次流分布规律,并对流动过程和出口流场进行了分析。 相似文献
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Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs. 相似文献
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S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
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A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output. 相似文献
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The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper. 相似文献
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We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed. 相似文献
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Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell. 相似文献
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A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques. 相似文献
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Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing. 相似文献
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Yepeng Guan 《中国光学快报(英文版)》2008,6(6)
Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate. 相似文献