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The problem investigated is the break of a high-pressure pipeline carrying natural single-phase gas which may condensate (retrograde) when the pressure drops. Single-phase non-ideal gas is assumed using a general- ized equation of state. Taking advantage of the choked massflow condition, the break is split into a pipe flow problem and a dispersion flow problem, both solved using a finite difference control volume scheme. The transient flow field from the pipeline break location is expanded analytically, using an approximation of the governing equations, until ambient pressure is reached and matched to the corresponding gas dispersion flow field using as subgrid model a jet box with a time-varying equivalent nozzle area as an internal boundary of the dispersion domain. The turbulence models used for the pipe and dispersion flow fields are an empirical model of Reichard and the k–ϵ model for buoyant flow respectively. The pipe flow simulations indicate that the flow from the pipeline might include dispersed condensate which will affect quantitatively the mass flow rate from the pipeline and qualitatively the gas dispersion if the condensate rains out. The transient dispersion simulation shows that an entrainment flow field develops and mixes supersaturated gas with ambient warmer air to an unsaturated mixture. Because of the inertia of the ambient air, it takes time to develop the entrainment flow field. As a consequence of this and the decay of the mass flow with time, the lower flammability limit of the gas–air mixture reaches its most remote downstream position relatively early in the simulation (about 15 s) and withdraws closer to the break location. 相似文献
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针对电气设备在检修过程中存在的问题,企业应遵循电气设备的检修程序,推行点检定修和规程化管理制度,实施合理的大修与改造,抓好备件储备,强化微机对设备检修的管理。 相似文献
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程艳珍 《科技情报开发与经济》2004,14(6):130-131
根据全硫分析的测定原理,分析了影响测定精确度的几个因素,并提出了降低全硫分的方法,从而有效地提高了煤的全硫分析精确度。 相似文献
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介绍了红外焦平面热成像仪原理,系统采用FPGA对数据进行采集控制,采用DSP对数据进行处理并与PC机通信,在硬件上构成一个以DSP+FPGA+PC的成像电力在线检测系统。文章给出了红外成像视频信号和DSP数据处理方法,并使用VB6.0实现图像在PC机上的显示和处理。 相似文献
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DRAŽEN ADAMOVIĆ 《Transformation Groups》2016,21(2):299-327
We shall first present an explicit realization of the simple N = 4 superconformal vertex algebra L c N?=?4 with central charge c = ?9. This vertex superalgebra is realized inside of the bcβγ system and contains a subalgebra isomorphic to the simple affine vertex algebra L A1 \( \left(-\frac{3}{2}{\varLambda}_0\right) \). Then we construct a functor from the category of L c N?=?4 -modules with c = ?9 to the category of modules for the admissible affine vertex algebra L A1 \( \left(-\frac{3}{2}{\varLambda}_0\right) \). By using this construction we construct a family of weight and logarithmic modules for L c N?=?4 and L A1 \( \left(-\frac{3}{2}{\varLambda}_0\right) \). We also show that a coset subalgebra L A1 \( \left(-\frac{3}{2}{\varLambda}_0\right) \) is a logarithmic extension of the W(2; 3)-algebra with c = ?10. We discuss some generalizations of our construction based on the extension of affine vertex algebra L A1 (kΛ 0) such that k + 2 = 1/p and p is a positive integer. 相似文献
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考虑车削加工过程中刀具磨损对切削力系数的影响,用Gamma过程描述了切削力系数随时间的变化过程,并建立了车削颤振时变可靠性模型.提出了主动学习的Kriging模型与基于首次超越的子集模拟相结合的时变可靠性分析方法(AK-SSFP).对某一车床建立车削颤振稳定性模型,分别采用Monte Carlo方法(MCS)、基于主动学习Kriging的Monte Carlo方法(AK-MCS)和AK-SSFP方法计算车削颤振时变可靠度.AK-SSFP方法的结果与MCS方法的结果一致性很好,且AK-SSFP方法减少了真实极限函数的调用次数并缩短了运算时间.AK-SSFP在保证精度的同时提高了计算效率,解决了车削加工系统颤振时变可靠度的计算问题. 相似文献