Arc spot scanning of tube electrodes in gas-vortex plasmatorches

The peculiarities of cooling of stationary working hot and cold cathodes are under consideration. Scientific premises of the advisability of the tube electrodes arc-spot scanning are presented. The classification of the scanning methods is given. The assumption has been made that the phenomena of auto-electron emission of electrons in vacuum discharge tubes and in arc chambers of plasmatorches under the pressure equal or above atmospheric are somehow similar. The optimum scanning frequency and achievable values of the end-face tube cathode life-time have been estimated. Owing to the magnetic scanning, the area of the electrode surface, which is swept by the arc spot, increases one order or more, resulting in better cooling and reduced specific erosion. The continuous electrode lifetime becomes several orders longer than it is during the work without scanning.     

Methods for increasing the service life of electrodes in the arc plasmatorches

Results of experimental studies of electrode erosion in high-current arc discharges are presented. Available data on the service life of electrodes in the arc plasma generators sometimes are contradictory and do not give the whole pattern on the relationship of specific erosion of the electrode material with the basic determining parameters of the plasmatorch. The real ways to increase the duration of plasmatorch operation before electrode replacement have been proposed.     

Separation of water-steam plasma in steam-vortex plasmatorches

The possibility of separation of the water-steam plasma in a centrifugal force field of a vortex stream is under consideration. We obtained the formulas to compute the radial distribution of the plasma mixture components and also to determine the dependence of the pressure and its gradient on the distance to the axis for the regions of solid-state and potential rotation of the vortex. The examples of poor arc stabilization and the proposals for its perfection are presented. The effect of the gas kind on the voltage of the vortex-stabilized arc is shown. The influence of the water-steam plasma individual components, regarding the separation, on the water-steam plasma energy characteristics is explained.     

Auto-scanning in plasmatorches with the magnetic-vortex arc stabilization

Under consideration is the physical nature of the auto-scanning in plasmatorches with tube electrodes; the exclusive simplicity of this process comparing to the aeromagnetic and gas methods of scanning has been demonstrated.     

涡流管设计及应用进展综述

涡流管作为一种简易的制冷装置被广泛应用,但压缩气体在其内部产生能量分离效果的作用机理十分复杂,故至今仍没有通用的能量分离机理可以为涡流管的设计与应用提供理论指导。为了给涡流管的设计与应用工作提供参考,对本体结构及工质参数对涡流管能量分离性能影响的研究进展做了较为详尽的论述,并对涡流管在制冷领域和天然气工业领域的应用现状进行了概述。另外,还对涡流管下一步的设计及研究工作进行了展望,并就一些优化问题提出了合理的解决方案。     

涡流管性能的热力学分析

涡流管是一种新型的能量分离装置,热力学参数和几何参数对其的性能影响很大。该文依据热力学第一、第二定律,建立了涡流管能量分离过程热力学模型,将不可逆过程可用能损失归结为热量火用收益和压力损失两部分,获得了一种基于热力学火用分析的涡流管性能优化新途径。结合不同进气压力、喷嘴数和冷端出口直径的涡流管能量分离性能实验,得到上述诸因素对涡流管能量分离过程中火用变化的影响,通过对能量分离过程中热量火用收益和压力损失的比较,实现了涡流管能量分离性能的优化设计。     

涡流管能量分离过程的热力学模型

根据工程热力学理论对涡流管工作过程进行了热力学分析,在h—s图上定性地表示出热力过程,获得了过程中相关参数的计算公式。通过对管内能量分离过程热力学分析,借助J．Mischner的热力学熵增理论,获得了涡流管内能量分离效应与冷气流率的函数关系式,建立了完整的涡流管能量分离过程的热力学模型。     

Variational treatment of an isolated vortex tube in type-II superconductor

The structure of an isolated vortex tube, representing the mixed state of type-II superconductors near the lower critical field, has been investigated variationally for arbitrary values of the Ginzburg-Landau (G-L) parameter κ. The results are in excellent agreement with other calculations.     

Numerical visualization of counter rotating vortex ring formation ahead of shock tube generated vortex ring

Graphical Abstract  

     

新型涡流管的制冷特性研究

以新型涡流管为研究主体,通过实验,研究涡流管操作参数对涡流管性能的影响。根据实验数据,分析改变温度压力等操作参数对涡流管能量分离效应的影响。试验结果表明:当提高涡流管进气温度,其冷热两端出气温度升高,但并不影响涡流管的制冷效率;增加涡流管进气压力会提高涡流管制冷效应,并在冷流率为0.2时效果最明显;制冷效率随节流阀开度增加而增加且最终趋于稳定,而制热效率则随节流阀开度增加而减小并最终趋于稳定。     

涡流管研究进展及在天然气工业中的应用

涡流管是一种结构简单的能量分离装置,随着测试手段的进步,计算流体力学技术的发展,涡流管重新成为了研究热点。从理论、实验以及数值模拟三方面综述了涡流管的研究现状,并着重介绍了涡流管在天然气工业中的应用情况。     

轴流式涡流管内三维流场的大涡模拟

根据涡流管内可压缩气体的强旋转运动是导致涡流管能量分离的根本原因,提出了在涡流管内加入一个"X"型导流片迫使气流产生强旋转运动,使其进气方式变为轴流式。利用计算流体动力学(CFD)的方法,建立了轴流式和切流式涡流管内部气体流动的三维大涡数值模型,对其内部气流流场进行了数值模拟。数值模拟结果表明:"X"型导流片可以改变轴向进入气体的运动方向,使气体产生高速旋转运动,得出"X"型导流片的叶片夹角为θ=120°时,气体的旋转效果最好;大涡模拟可以较好地模拟涡流管内气流的三维流场。     

Cyclostrophic adjustment in swirling gas flows and the Ranque-Hilsch vortex tube effect

A theoretical analysis of cyclostrophic adjustment is presented; i.e., adjustment to balance between pressure gradient and centrifugal force in axisymmetric flow of an inviscid gas is examined. The solution to the problem is represented as the sum of a time-independent (balanced) and time-dependent (wave) components. It is shown that the wave component of the flow in an unbounded domain decays with time, and the corresponding solution reduces to the balanced component. In a bounded domain, the balanced flow component exists against the background of undamped acoustic waves. It is found that the balanced flow is thermally stratified at Mach numbers close to unity, with a substantial decrease in gas temperature (to between ?50 and ?100°C) in the axial region. This finding, combined with the results of special experiments, is used to explain the Ranque-Hilsch vortex tube effect.     

涡流管复合冷却服降温性能实验研究

为解决人们在高温环境作业时的热应激,本文设计出一种涡流管和相变材料复合型冷却服.通过实验研究冷却服在不同工况下的降温参数变化和热舒适评价规律.实验表明:轻度劳动下复合型冷却服使皮肤温度最大降幅为7.6℃;重度劳动下热舒适最大值为1.5且降温续航时间长达80 min.复合型冷却服中的相变材料减小了人体核心温度的波动,使降...     

涡流管冷却的旋转晶体窗口有限元分析

 采用有限元分析方法,考虑到输出窗口在空间上的分布不均匀性,对白宝石、石英晶体窗口在光强分布均匀/不均匀、有/无冷却、是否旋转等各种情况下的温度场进行了分析和讨论。结果表明：当光强分布不均匀时,采用旋转方法能有效地减小温度场的不均匀性;当对输出窗口进行强迫冷却时,输出窗口温度场不均匀性明显减小。因此采用涡流管冷却的旋转晶体窗口能有效改善输出窗口的输出特性。     

涡流管冷却的旋转晶体窗口有限元分析

采用有限元分析方法,考虑到输出窗口在空间上的分布不均匀性,对白宝石、石英晶体窗口在光强分布均匀/不均匀、有/无冷却、是否旋转等各种情况下的温度场进行了分析和讨论。结果表明：当光强分布不均匀时,采用旋转方法能有效地减小温度场的不均匀性;当对输出窗口进行强迫冷却时,输出窗口温度场不均匀性明显减小。因此采用涡流管冷却的旋转晶体窗口能有效改善输出窗口的输出特性。     

Luminescence intensity of vortex cavitation in a Venturi tube changing with cavitation number

Hydrodynamic cavitation in a Venturi tube produces luminescence, and the luminescence intensity reaches a maximum at a certain cavitation number, which is defined by upstream pressure, downstream pressure, and vapor pressure. The luminescence intensity of hydrodynamic cavitation can be enhanced by optimizing the downstream pressure at a constant upstream pressure condition. However, the reason why the luminescence intensity increases and then decreases with an increase in the downstream pressure remains unclear. In the present study, to clarify the mechanism of the change in the luminescence intensity with cavitation number, the luminescence produced by the hydrodynamic cavitation in a Venturi tube was measured, and the hydrodynamic cavitation was precisely observed using high-speed photography. The sound velocity in the cavitating flow field, which affects the aggressive intensity of the cavitation, was evaluated. The collapse of vortex cavitation was found to be closely related to the luminescence intensity of the hydrodynamic cavitation. A method to estimate the luminescence intensity of the hydrodynamic cavitation considering the sound velocity was developed, and it was demonstrated that the estimated luminescence intensity agrees well with the measured luminescence intensity.     

涡流管内三维强旋转流场数值模拟与分析

涡流管内可压缩气体的强旋转流动是涡流管能量分离的根本原因和驱动力,因而涡流管内流场研究是揭示涡流管能量分离物理机制的首要关键问题。由于涡流管内可压缩气体的三维强旋转湍流流动,实验测量中存在诸多问题,而CFD数值模拟技术对此具有很大的优势。文中以涡流管内部流场为研究对象,建立了涡流管计算域模型并进行网格划分,讨论了边界条件、湍流模型以及线性方程组求解策略等问题,对不同冷气流率下的涡流管内三维强旋流流场结构特性进行数值模拟,获得了不同冷气流率下的旋转运动、轴向运动、径向运动和循环流的分布特性。研究表明Realizableκ-ε湍流模型能够充分反映强旋流动特点,数值模拟结果与文献中实验值基本吻合。     

涡流管冷却的旋转晶体窗口有限元分析

采用有限元分析方法,考虑到输出窗口在空间上的分布不均匀性,对白宝石、石英晶体窗口在光强分布均匀/不均匀、有/无冷却、是否旋转等各种情况下的温度场进行了分析和讨论.结果表明当光强分布不均匀时,采用旋转方法能有效地减小温度场的不均匀性;当对输出窗口进行强迫冷却时,输出窗口温度场不均匀性明显减小.因此采用涡流管冷却的旋转晶体窗口能有效改善输出窗口的输出特性.