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电弧等离子体射流核脉动的实验研究 总被引:2,自引:0,他引:2
电弧等离子体射流中的湍流是等离子体射流的典型物理现象之一,而以往的研究认为射流存在一个处于稳定状态的核心区域,也有人认为这个状态是层流的。本文采用电弧等离子光谱诊断及数字高速摄影的方法对常压电弧等离子体射流核进行了研究,采用了傅里叶变换的方法分析弧电压和射流光谱强度信号,发现电源的交流分量和阳极弧点运动对整个射流核的脉动特性都有体现,射流并不存在一个处于稳定状态的核心区域,相反谱线强度脉动图中可以看到,射流核的脉动是由电弧电压脉动造成的,这可能是射流核脉动的最主要原因。 相似文献
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电弧等离子体射流核脉动及射流卷吸的实验研究 总被引:1,自引:0,他引:1
湍流是电弧等离子体射流中典型的物理现象之一。以往的研究认为,射流存在一个处于层流状态的核心区域。采用电弧等离子体光谱诊断及数字高速摄影的方法对方法对常压电弧等离子体射流核进行了研究,采用傅里叶变换的方法分析了弧电压和射流光谱强度信号。结果发现,电源的交流分量和阳极弧点运动在整个射流核的脉动特性中都有体现,射流并不存在一个处于稳定状态的核心区域。相反,从谱线强度脉动图中可以看到,射流核的脉动是由电弧电压脉动造成的,这可能是射流核脉动的最主要原因。采用多元素谱线强度法研究了射流对空气的卷吸作用,并通过氮原子谱线强度确定了氮原子数密度在射流中的分布。 相似文献
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采用自行研制的直流非转移型等离子体发生器,对其产生的层流等离子体射流特性进行了实验研究。实验结果表明:该等离子体发生器在以纯氮气为工作气体时,呈现出高电压低电流的等离子体射流特性,该特性有助于提高等离子体发生器的电极寿命;在弧电流和工作气流量由小向大变化过程中,等离子体射流长度均呈现出先由短变长、再由长变短的变化规律;在等离子体射流长度由长变短的过程中,射流的形貌从相对集中、轴对称和稳定的状态向分散、非轴对称和不稳定的状态变化,即等离子体射流由层流形态向湍流形态转变,并且在此过程中射流产生的噪音逐渐增强。 相似文献
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本文应用大气压等离子体射流传热与流动的三维数学模型,在相同初始条件下,计算得到了采用不同湍流模型时氩等离子体射流对称轴线上的温度、速度及空气质量分数分布,并与文献中同等条件下的实验结果进行了比较,结果表明采用标准κ-ε模型和Realizableκ-ε模型时与实验结果相差较大,而采用RNGκ-ε湍流模型时模拟结果与实验数... 相似文献
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介绍了一种新型大气压直流双阳极等离子喷枪,并对其电特性参数和发射光谱进行了测量.通过对氩等离子体射流的电信号进行时域和频域分析,研究了载气流量和弧电流的变化对射流脉动的影响,结果表明氩等离子体电弧的伏安特性呈上升趋势,射流脉动属于接管模式,电源特性中的交流分量引起的电压波动是影响氩等离子体射流脉动的主要因素. 通过光谱法测量了氩等离子体射流在弧室内和弧室出口的发射光谱,利用玻尔兹曼曲线斜率法计算了射流的激发温度,根据Ar I谱线的斯塔克展宽得到了射流的电子密度,并对等离子体射流满足局域热力学平衡(LTE)
关键词:
等离子喷枪
射流脉动
激发温度
局域热力学平衡 相似文献
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通过电弧模型与熔池模型耦合数值模拟,研究了氩弧和氦弧特性及其对SUS304不锈钢钨极惰性气体保护(TIG)焊熔池形貌的影响.通过比较氩弧和氦弧的温度轮廓线以及阳极表面电流密度和热流密度分布发现,氦弧的径向距离比氩弧收缩明显,导致更多热量传递给阳极.模拟了氩弧和氦弧下浮力、电磁力、表面张力和气体剪切力分别对熔池形貌的影响.结果表明:不论是在氩弧还是在氦弧下熔池中表面张力是影响熔池形貌的最主要驱动力.在氩弧下,影响熔池形貌的另一个重要的驱动力是气体剪切力,而氦弧下则是电磁力.由于电磁力引起的内对流运动增加了熔深,从而导致相同氧含量时氦弧下的熔深和焊缝深宽比要高于氩弧下的熔深和焊缝深宽比.随着氧含量的增加,氩弧和氦弧下的焊缝深宽比均先增加而后保持不变.焊缝深宽比的模拟结果与实验结果符合较好.
关键词:
氩弧
氦弧
电弧特性
熔池形貌 相似文献
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《等离子体物理论文集》2017,57(2):58-66
Plasma jets from conventional non‐transferred arc plasma devices are usually operated in turbulent flows at atmospheric pressure. In this paper, a novel non‐transferred arc plasma device with multiple cathodes is introduced to produce long, laminar plasma jets at atmospheric pressure. A pure helium atmosphere is used to produce a laminar plasma jet with a maximum length of >60 cm. The influence of gas components, arc currents, anode nozzle diameter, and gas flow rate on the jet characteristics is experimentally studied. The results reveal that the length of the plasma jet increases with increasing helium content and arc current but decreases with increasing nozzle diameter. As the gas flow rate increases, the length of the plasma jet initially increases and then decreases. Accordingly, the plasma jet is transformed from a laminar state to a transitional state and finally to a turbulent state. Furthermore, the anode arc root behaviours corresponding to different plasma jet flows are studied. In conclusion, the multiple stationary arc roots that exist on the anode just inside the nozzle entrance are favourable for the generation of a laminar plasma jet in this device. 相似文献
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Shimanovich V.D. Smyaglikov I.P. Zolotovsky A.I. Yas'ko O.I. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(5):877-882
This paper studies the anode region of an eroding anode with a nonstationary arc-root attachment. High-current free-burning short as well as long arcs at atmospheric pressure are investigated. A technique to study the anode region of the arc is suggested. An anode moving perpendicular to the arc axis was used for estimating parameters of the anode jets at a given moment of their development. The mechanism of current transfer in the anode region is considered on the basis of electrophysical and optical-spectroscopic investigations of the arc attachment traces and plasma parameters both of the anode jet and arc column. The anode jet was found to be of importance in the stationary arc operation. The near-anode plasma parameters depend on the effect of the cathode jet. In short arcs (La~2 mm), the plasma temperature at the anode exceeds 20000 K, while in long arcs (La >50 mm), it falls below 7000 K. At plasma temperature Ta >11000 K, the total arc current in the anode region is transferred through the arc plasma, while at lower temperatures, both the arc column and the anode jet take part in the current transfer 相似文献
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Dorier J.-L. Gindrat M. Hollenstein C. Salito A. Loch M. Barbezat G. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2001,29(3):494-501
The fluctuating behavior of a Sulzer Metco F4 DC plasma gun has been investigated by simultaneous measurement of the time dependencies of the are voltage and of images from the nozzle interior. An end-on imaging arrangement using a mirror and a mask in the optical path from the are to the camera allows visualization of the anodic arc attachment by strongly attenuating the bright emission from the are column. With the torch operating in the restrike mode, sequences of images have been acquired in synchronization with several typical features of the are voltage fluctuations showing that the attachment nature changes during a restrike cycle. Multiple attachments which coexist at least during the 1 μs exposure time of the camera have been evidenced and are interpreted as a continuous process of creation/vanishing of successive arc roots with a smooth transfer of the current from one to the other. The anode wear is shown to have a strong effect on the root position over the anode periphery, with a preference for attachment in eroded regions. The effects of operation parameters such as current, gas flow and injector type on the attachment nature and position are also presented 相似文献
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Although plasma torches have been commercially available for about 50 years, areas such as plasma gun design, process efficiency,
reproducibility, plasma stability, torch lives etc. have remained mostly unattended. Recent torch developments have been focusing
on the basic understanding of the plasma column and its dynamics inside the plasma torch, the interaction of plasma jet and
the powders, the interaction of the plasma jet with surroundings and the impingement of the jet on the substrate. Two of the
major causes of erratic and poor performance of a variety of thermal plasma processes are currently identified as the fluctuations
arising out of the arc root movement on the electrodes inside the plasma torch and the fluid dynamic instabilities arising
out of entrainment of the air into the plasma jet. This paper reviews the current state of understanding of these fluctuations
as well as the dynamics of arc root movement in plasma torches. The work done at the author’s laboratory on studying the fluctuations
in arc voltage, arc current, acoustic emissions and optical emissions are also presented. These fluctuations are observed
to be chaotic and interrelated. Real time monitoring and controlling the arc instabilities through chaos characterization
parameters can greatly contribute to the understanding of electrode erosion as well as improvement of plasma torch lifetime. 相似文献
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Arc root motions in generating dc argon hydrogen plasma at reduced pressure are optically observed using a high-speed video camera. The time resolved angular position of the are root attachment point is measured and analysed. The arc root movement is characterized as a chaotic and jumping motion along the circular direction on the anode surface. 相似文献
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利用高速纹影系统和数值模拟方法研究了激波/边界层干扰对逆流喷射的等离子体合成射流的响应特性,并揭示了流动控制机理.实验在来流马赫数Ma=3.1的风洞中进行,测试模型采用钝头体和压缩斜坡的组合模型,等离子体合成射流激励器安装在钝头体头部.纹影系统捕捉了放电频率为f=1 kHz和f=3 kHz的激励对附体激波形态和分离激波运动的控制效果.等离子体合成射流使压缩斜坡激波/边界层干扰区域的起始点向下游移动,分离泡尺寸减小,附体激波强度减弱,发生弯曲,再附点移向上游,与此同时分离激波向附体激波逼近.与f=3 kHz激励相比,f=1 kHz激励的射流流量更大,对激波/边界层干扰的影响范围更广、控制效果更好.通过数值模拟,揭示了射流与来流相互作用对下游流场的作用机理:射流与来流相互作用诱导出大尺度旋涡,大尺度旋涡耗散发展增强了近壁面流场的湍流度;压缩斜坡上游近壁面的流场性质发生变化,进而导致了压缩斜坡激波/边界层干扰区域流动的变化. 相似文献