共查询到20条相似文献,搜索用时 11 毫秒
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Uk-Hee Jung Sung Kim Sang-Ho Yang Jin-Hyuk Kim Young-Seok Choi 《Journal of Mechanical Science and Technology》2016,30(11):4961-4969
A tunnel fire is very dangerous to drivers because of generated poisonous gases. For dealing with this hazardous situation, ventilation systems for smoke control are installed so that drivers can be safely evacuated from the site of the fire. An air curtain system is one of these ventilation systems, and such a system in a tunnel generates an air wall to block the passage of poisonous gases. In this study, airflow discharge patterns of air curtain systems were analyzed using Computational fluid dynamics (CFD), with two design parameters—to predict the ability of the air curtain to block the contaminated adverse air-flow in the tunnel. The considered two design parameters were the installed angle of the slit nozzle (NA) and the discharged air velocity at the slit nozzle outlet (NV). The tunnel geometry for the CFD analysis was a two-lane type with a tunnel length of 100 m and an elliptical cross section. The height of the tunnel was approximately 7.3 m and the height of the installed air curtain was about 4.9 m from the road surface. In this study, the heat release rates of the fire, the distance from the fire site, and the temperature of the working fluid were respectively assumed to about 20 MW, 50 m and 473 K, on the basis of the NFPA 502. The CFD analysis demonstrated that an NA of 0 deg could not block the adverse air flow due to a realistic tunnel inlet-outlet static pressure difference (ΔPS). An NA of 20 deg was required to effectively block the adverse flow. The blocking failure first formed at the sidewall of the tunnel, and it proceeded toward the center of the tunnel cross section when the adverse wind was strong. That aspect of the blocking failure was judged to be due to the fact that the tunnel cross section is elliptical. Anyway, when the tunnel ΔPS was increased, that showed the need for a high NV. 相似文献
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D.F.G. Hampson 《Wear》1975,34(3):399-407
A review of the background to selecting and testing reciprocating air compressor lubricants as regards their carbon forming tendencies is given in this paper. The results of field trials of a synthetic hydrocarbon type oil and the role played by the volatility of this lubricant in reducing carbon deposits are discussed. 相似文献
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An analysis of force distribution in shear spinning of cone 总被引:1,自引:0,他引:1
Ming-Der Chen Ray-Quan Hsu Kuang-Hua Fuh 《International Journal of Mechanical Sciences》2005,47(6):902-921
An analytic model for calculation of shear spinning force incorporate factor of over-roll (press down) of the blank is derived. The effects of blank thickness, roller nose radius, mandrel revolution and roller feed on the spinning force are discussed. Results obtained from calculation were compared with the experiment and other theoretical predictions. It is found that the present findings yield optimum results. 相似文献
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Ki Yong Lee Andrew Lock Anthony Hamins 《Journal of Mechanical Science and Technology》2011,25(8):2035-2041
A set of experiments has been conducted on a medium-scale propane fueled pool fire acoustically forced in order to facilitate
repeatable measurements defining the flame’s transient behavior. The fuel flow was slightly perturbed at the pool fire’s natural
frequency by a sine waveform driven with a loudspeaker which was installed under the burner. As a result of the perturbation,
the puffing behavior of the pool fire and the fire shape were modified. As the magnitude of the sine wave was increased larger
perturbations were clearly observed, based on the measurement of the radiative heat flux and image analysis. Temperature and
soot volume fractions were measured along the center line and throughout a slice of the flame. The soot volume fractions in
the flame region are in good agreement with the data of other researchers. The reproducibility of these measurements was established
through several experiments. The acoustically driven flame provides the possibility of more repeatable measurements of the
transient behavior of these pool fires. 相似文献
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Su-Hwan Yun Min-Ho Kwak Dong-Ho Lee Hyeok-Bin Kwon Tae-Hwan Ko 《Journal of Mechanical Science and Technology》2010,24(7):1433-1440
When a train travels through tunnel at a high speed, large pressure variations are produced on the train surface by pressure
waves. In particular, when an express train travels through a narrow tunnel at a speed higher than that of a conventional
train, more severe pressure variations can occur and cause passengers ear discomfort. This paper presents a very simple and
effective reduction method of the large pressure variation for a narrow conventional tunnel. When a compression wave and an
expansion wave are superposed, the pressure variation can be greatly reduced. Using this phenomenon, this study proposes the
construction of a dummy tunnel duct which superposes the pressure waves and reduces the large pressure variation. Using the
proposed method, the construction cost is much lower compared to other methods because the dummy tunnel duct can be constructed
at the entrance or at the exit of an existing tunnel with a simple tunnel shape. To investigate the change in the maximum
pressure difference and pressure variation ratio with the application of a dummy tunnel duct, full-scale tests and numerical
analyses were conducted. The results showed that the maximum pressure changes and pressure variation ratio are significantly
reduced by a short dummy tunnel duct. From these results, the dummy tunnel duct is expected to be a very economical and practical
solution to passenger ear discomfort problems for express trains traveling through conventional narrow tunnels. 相似文献
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本文对质量检验合格的螺栓在施工中失效的一真实案例进行了失效原因分析,提出了改进设计方案.同时对检验条件与工程实践间的差距及解决方法做了有益的探讨. 相似文献
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大口径透镜姿态调整机构的支承分布设计 总被引:2,自引:0,他引:2
为了设计大口径透镜姿态调整机构,研究了三顶三拉调平结构布置方式的调节性能及其对受力变形和光束质量的影响。采用几何方法,得出了三顶三拉结构在任意三角形布置下升高量与调整角度变化的关系,定义了角度调整的相关系数;利用有限元分析软件分析了3类支承点布置情况下调节平板的变形情况。分析结果表明,三顶三拉调整机构具有调整量可计算的特点,当调节平板的尺寸为580 mm×570 mm×20 mm,采用等腰三角形支承点布置方式时,重力引起的最大变形为12.51μm。对采用了等腰三角形三顶三拉结构的透镜姿态调整机构进行了装校调试及打靶实验,结果证实了该布点方式对姿态调整的有效性和调整完成后精度的稳定性。 相似文献
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介绍了大型甲醇和一氧化碳生产装置在线分析系统的设计和应用。对仪器选定的评估标准、取样系统设计和制作、在线分析系统安装和投运等问题作了讨论。此在线分析系统已成功投入运行。 相似文献
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从Fourier分析和卷积滤波入手,从工程角度来讨论小波分析的基本原理,并利用小波带滤波方法对大轴承的振动信号进行时频分析,确定了大轴承故障的部位、类型和程度,经现场拆卸验证,结论是正确的。 相似文献
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An analysis based on the Navier-Stokes equations is made for the flow of a liquid in magnetohydrodynamic circular bearings under rotating conditions. The analysis presents expressions for both radial and tangential velocities with and without inertia effects. The results show that the application of a magnetic field reduces both radial and tangential velocities. The rotational inertia effect has a greater effect on the radial velocity at small film thicknesses. 相似文献
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Stefano Malavasi Roberto Corretto Fabio Fossati 《Flow Measurement and Instrumentation》2011,22(5):428-437
Although Particle Image Velocimetry techniques are widely used in the experimental investigation of the flow structure around obstacles, the application of these techniques in wind tunnels is frequently limited by the dimension of the areas involved, which make the image acquisition set-up expensive.This paper examines the use of Particle Streak Velocimetry (PSV) and marker detection techniques to measure the flow field around bodies with relatively large dimensions. In spite of its minimal requirements in terms of acquisition set-up, the method permits the investigation of complex phenomena.The tests described in the paper were carried out in air using a rigid cylinder, free to oscillate in a wind tunnel. Coupling PSV and marker detection techniques with the phase average of the measured velocity fields, the evolution of vortex shedding behind a cylinder with a diameter of 200 mm was measured with an acquisition area of about 1000×1200 mm. 相似文献