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Misalignment analysis of journal bearing influenced by asymmetric deflection, based on a simple stepped shaft model
Zhen-peng He, Jun-hong Zhang, Wei-song Xie, Zhou-yu Li, Gui-chang Zhang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(9): 647-664.
https://doi.org/10.1631/jzus.A1200082
The effects of journal misalignment on a journal bearing caused by an asymmetric rotor structure are presented in this study. A new model considering the asymmetric deflection is applied. Also, the thermo-hydrodynamic of the oil film in the journal bearing and straightforward elasticity theory are considered in the analysis. Based on the structure stiffness equivalent characteristic, a simple stepped shaft can reflect the entire complex structure model. The existing lubrication model, which does not consider this angle component, is not very precise for journal bearings. Film pressure, misalignment angle, velocity field, oil leakage, and temperature field were calculated and compared in the journal bearing analysis. The results indicate that bearing performances are greatly affected by misalignment caused by the asymmetric structure. A simple stepped shaft can effectively represent a misaligned journal bearing in a rotor-bearing system.
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Containment of high-speed rotating disk fragments
Hai-jun Xuan, Lu-lu Liu, Yi-ming Feng, Qing He, Juan-juan Li
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(9): 665-673.
https://doi.org/10.1631/jzus.A1200047
Disk burst accidents sometimes happen in aeroengines. To avoid tragic consequences, aeroengine casings must have sufficient containment capability. Experiments and simulations need to be conducted to study the impact, distortion, and perforation caused by disk burst and which may give important clues to potential failure mechanisms. This paper presents some containment tests of high-speed rotating disk fragments, in which the original disks were burst into three equal fragments within a predetermined rotating speed range. The failure modes of the containment casing varied significantly with the thickness of the containment casing. Shearing, tearing, tensile fracture, and large plastic stretching deformation occurred in a thin-walled containment casing, while a thick-walled casing could contain disk fragments and withstand large plastic deformation. Numerical simulations were carried out to study the impact process and failure modes further. Good agreement was found between the results of the simulations and the tests.
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Impact of individual acid flue gas components on mercury capture by heat-treated activated carbon
Jian-ming Zheng, Jin-song Zhou, Zhong-yang Luo, Ke-fa Cen
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(9): 700-708.
https://doi.org/10.1631/jzus.A1200112
Elemental mercury capture on heat-treated activated carbon (TAC) was studied using a laboratory-scale fixed bed reactor. The capability of TAC to perform Hg0 capture under both N2 and baseline gas atmospheres was studied and the effects of common acid gas constituents were evaluated individually to avoid complications resulting from the coexistence of multiple components. The results suggest that surface functional groups (SFGs) on activated carbon (AC) are vital to Hg0 capture in the absence of acid gases. Meanwhile, the presence of acid gas components coupled with defective graphitic lattices on TAC plays an important role in effective Hg0 capture. The presence of HCl, NO2, and NO individually in basic gases markedly enhances Hg0 capture on TAC due to the heterogeneous oxidation of Hg0 on acidic sites created on the carbon surface and catalysis by the defective graphitic lattices on TAC. Similarly, the presence of SO2 improves Hg0 capture by about 20%. This improvement likely results from the deposition of sulfur groups on the AC surface and oxidation of the elemental mercury by SO2 due to catalysis on the carbon surface. Furthermore, O2 exhibits a synergistic effect on Hg0 oxidation and capture when acid gases are present in the flue gases.
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An improved technique for global daily sunshine duration estimation using satellite imagery
Muhammad Ali Shamim, Renji Remesan, Da-wei Han, Naeem Ejaz, Ayub Elahi
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2012, 13(9): 717-722.
https://doi.org/10.1631/jzus.A1100292
This paper presents an improved model for global sunshine duration estimation. The methodology incorporates geostationary satellite images by including snow cover information, sun and satellite angles and a trend correction factor for seasons, for the determination of cloud cover index. The effectiveness of the proposed methodology has been tested using Meteosat geostationary satellite images in the visible band with a temporal resolution of 1 h and spatial resolution of 2.5 km×2.5 km, for the Brue Catchment in the southwest of England. Validation results show a significant improvement in the estimation of global sunshine duration by the proposed method as compared to its predecessor (R2 is improved from 0.68 to 0.83, root mean squared error (RMSE) from 2.37 h/d to 1.19 h/d and the mean biased error (MBE) from 0.21 h/d to 0.08 h/d). Further studies are needed to test this method in other parts of the world with different climate and geographical conditions.
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7 articles
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