共查询到13条相似文献,搜索用时 156 毫秒
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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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采用给水冷管状静电探针施加负偏置电压、并使探针以一定速度垂直于射流轴线扫过层流氩等离子体射流的方法,测量探针所收集到的累积离子饱和电流随侧向位置的变化,利用Abel变换推导出了局部离子饱和电流密度沿射流径向的分布;采用自制的水冷动压探针,以动态扫描法测量了射流动压沿射流径向的分布;根据局部离子饱和电流密度和射流动压的测量数据,由理论关系式推导出了等离子体射流横截面上的温度分布,同时,采用谱线相对强度法测量了等离子体射流的激发温度。结果表明:两种方法得到的等离子体射流中心温度吻合较好,所得到的射流中心温度随弧电流加大而增大的变化趋势也一致。 相似文献
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层/湍流等离子体射流的稳定性与三维特性的实验观测研究 总被引:1,自引:0,他引:1
采用普通照相和短时间曝光成像的ICCD照相技术,观测了低于大气压条件下产生的纯氩和氩-氢直流电弧等离子体射流的高温区的瞬时形貌及其变化,结合电弧弧根在阳极表面贴附行为的观测结果,对射流的稳定性与三维特性和弧根行为之间的关联进行了分析.结果表明,层流等离子体射流的高温区长度明显长于湍流射流情形,并且具有很好的轴对称性和时间稳定性;湍流射流的高温区瞬时形貌则表现出明显的三维特征;等离子体射流的三维特性与弧根在阳极表面的贴附行为没有直接的联系. 相似文献
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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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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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���������������Է��� 总被引:2,自引:0,他引:2
通过构建等离子体数字测控系统,测量了等离子体发生器不同工况下的工作参数,包括工作气体流量、冷却水温升、弧电压与弧电流等。运用能量平衡原理,计算了等离子体发生器出口射流平均焓值、平均温度及其分布。结果表明,在等离子体发生器的出口处,射流温度呈抛物线分布,增加主气气体流量,射流焓值与温度呈下降趋势,而添加氢气为辅助工作气体时,射流焓值与温度将会得到显著提高。 相似文献
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A novel DC plasma torch with multiple cathodes is developed for generating laminar, transitional and turbulent plasma jets. The jet's characteristics, including jet appearance, voltage fluctuation, thermal efficiency, specific enthalpy, and distributions of temperature, pressure, and velocity, are experimentally investigated. The results show that as the gas flow rate increases, the plasma jet transforms first from the laminar state to the transitional state and second to the turbulent state. Compared with the transitional/turbulent jet, the laminar jet possesses not only a better stability and a longer hightemperature zone but also a higher average/core temperature and a higher specific enthalpy at the nozzle's outlet. With the change of jet states from the laminar to the turbulent flow, the core pressure and velocity at the nozzle's outlet increase,while the decaying rates of temperature/pressure/velocity along the jet's axial direction increase sharply. Furthermore, applications of laminar, transitional and turbulent jets for zirconia spray coating are described. The test results indicate that the long laminar jet is favorable for the deposition of a high-quality coating because the powder particles injected into the laminar jet may have better heating and lower kinetic energy. 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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G. V. Kozlov G. R. Grek A. M. Sorokin Yu. A. Litvinenko 《Thermophysics and Aeromechanics》2008,15(1):55-68
Experimental data concerning the influence of initial conditions at the nozzle exit on the structure and development characteristics
of round jets are reported. Features in the development of laminar and turbulent round jets emanating from variously elongated
nozzles at identical Reynolds numbers are revealed. Smoke visualization pictures obtained for jets formed under different
initial conditions (with different distributions of mean and pulsating flow velocities at the nozzle exit) are discussed.
It is shown possible to make the zone of laminar flow in the jet stream more extended, and to delay the jet turbulization
process in space, by making the flow-velocity profile more parabolic at the exit of elongated nozzle. Features in the development
of vortical structures in a jet under an acoustic action are identified. It is shown that, for a turbulent round jet to be
produced right at the nozzle exit, the nozzle length must be increased in excess of a certain value so that to provide for
spatial growth of turbulent boundary layer thickness, finally ending in the formation of a fully turbulent flow velocity profile
across the channel.
This work was supported by the Russian Foundation for Basic Research (Grant No. 08-01-00027), the Ministry of Education and
Science of the Russian Federation (project RNP 2.1.2.3370), and by the grants of President of the Russian Federation (NSH-454.2008.1
and. MK-420.2008.1). 相似文献