等离子体气动激励系统电特性的实验研究

为了研究大尺度等离子体激励器和调整电源电感、电容的情况,笔者对等离子体气动激励系统的电特性进行了实验研究,得出等离子体气动激励系统的电感和电容是影响电特性的关键因素。实验结果表明,一定的电源输入电压下,减小电源电感或串联电容分压器,等离子体气动激励系统的谐振频率、电源输入电流和放电电流增大,等离子体气动激励器的放电电压基本保持不变;随着电源频率的增大,等离子体气动激励系统放电有3个典型的方式,电源频率小于谐振频率时,放电电流波形有突变;随着电源频率增大,激励系统的感性不断增大,放电电流增大,电流突变消失;电源频率大于谐振频率后,电容将电压的高次谐波滤掉,放电电流减小。     

锯齿等离子体气动激励器放电特性与加速效应

为研究新型布局的锯齿等离子体气动激励器的放电特性与加速效应,在常规大气环境下测量了不同激励参数下的频率—放电电压—放电电流—电源电流以及等离子体气动激励器诱导的边界层速度。结果表明:与常规布局等离子气动激励器相比,布局形式改变后谐振频率保持不变,放电电压相差不大,但放电电流变小,消耗的功率变小;诱导速度与激励电压呈近线性关系变化,速度值较常规布局小,其尖端放电诱导的气流对流场的扰动影响有待进一步的研究;实验还发现锯齿等离子体气动激励器放电时离子流对绝缘材料有很强的破坏作用。     

射频放电等离子体气动激励特性的实验研究

为了提高等离子体气动激励的强度及流动控制的能力,实验研究了射频放电等离子体的气动激励特性。建立了射频放电等离子体气动激励实验系统,由射频信号发生器、阻抗匹配升压变压器、尖–尖电极等离子体激励器等组成。尖–尖电极等离子体激励器由一组对称的电极和固定装置组成,电极材料采用钨,固定装置材料采用胶木,固定之后电极间距为0.5 mm。在静止空气条件下进行实验,研究了射频放电等离子体的电特性和诱导流动特性。实验结果表明:气压变化时,等离子体激励器的阻抗会发生变化,耦合到等离子体激励器的输入功率也不同;在大气压下,由于射频放电存在快速加热作用,在静止空气中诱导产生了近似圆柱形的冲击波;冲击波首先以音速向外传播,随后强度逐渐减弱,一定时间后衰减为弱扰动;采用射频电源、重频脉冲直流电源、ns脉冲电源,均能在静止空气中诱导产生冲击波,冲击波波速接近音速。由于射频电源的体积、重量更小,实现阻抗匹配之后所需的电源输入功率最低,因此,射频放电是一种非常有前景的气动激励产生方式,在等离子体流动控制方面可能取得较好的效果。     

对称布局等离子体气动激励器的放电特性与加速效应

等离子体气动激励诱导空气流动特性的测试诊断,是等离子体流动控制的重要基础。为了解等离子体气动激励的电特性,以及激励电压幅值和相位对诱导流动特性的影响,选取对称布局介质阻挡放电激励器进行了实验研究。结果表明：对称布局激励器的放电形式为丝状放电,均匀发生在高压电极周围,与非对称布局激励器的放电图像不同;当激励器相邻高压电极上施加电压的幅值和相位均相同时,诱导的定向射流向上垂直于激励器表面,速度为m/s量级;改变激励器高压电极上施加电压的幅值或相位,可以诱导产生向左上方或右上方的射流,但不能有效增大诱导气流速度。     

μs脉冲等离子体气动激励特性的实验研究

等离子体气动激励特性的测试诊断是揭示等离子体流动控制物理作用机制的重要基础。为此,主要在常规大气环境条件下,对μs脉冲等离子体气动激励特性进行电、光谱和流动特性的综合测试诊断实验研究。实验结果表明:μs脉冲放电的本质是丝状放电,在一个周期内,放电集中在正电压脉冲和负电压脉冲的上升沿;随着激励电压幅值增大,发射光谱强度增大,但表征电子温度和密度的典型谱线比变化不大;在放电的起始阶段,等离子体气动激励诱导了启动涡,启动涡随后发展成近壁面射流;激励电压和脉冲重复频率越大,等离子体气动激励诱导体积力越大;μs脉冲等离子体气动激励为非定常激励,消耗的功率比激励电压波形为连续正弦波时减小约30%,对于等离子体流动控制研究更为有益。     

静止空气中重频脉冲火花放电等离子体的气动激励特性

不同的状况下的重频脉冲(PRF)火花放电等离子体气动激励特性并不相同。为此,采用重频脉冲电源和激励器在静止空气中产生火花放电等离子体气动激励,研究了其激励特性。实验结果表明:由于重复脉冲火花放电存在快速加热,因此会瞬间产生很大的温度升和气压升,进而诱导产生冲击波;冲击波在流场中以声速传播,随后强度逐渐减弱,一定时间后衰减为弱扰动。保持脉冲重复频率不变,当激励电压绝对值增大时,注入流场的单脉冲能量和冲击波波速都随之增大。而保持激励电压不变,增大脉冲重复频率时,注入流场的单脉冲能量和冲击波波速基本不变,同时由于放电周期变短,因此上一个放电周期产生的弱扰动在下一次放电时仍然存在。     

等离子体流动控制技术原理及典型应用

等离子体流动控制激励器由于其具有响应时间短、激励频带宽、器件小、能耗低的技术优势,是流动控制领域最活跃的控制方式之一。等离子体激励器在飞行器的增升减阻、性能增强、力矩控制等方面具有重要的应用前景。文中通过实验和数值模拟方法研究了介质阻挡放电等离子体激励器(DBD)和等离子体合成射流激励器(PSJ)的基本气动特性。AC-DBD激励器主要产生射流扰动,NS-DBD等离子体激励器产生的扰动包括压力波、射流和旋涡结构,PSJ激励器能形成压力波和速度更高的射流扰动。采用AC-DBD激励器可以在低速流动下,推迟平板转捩;采用NS-DBD激励器可以在来流速度为25 m/s时,抑制翼型的流动分离,同时NSDBD在Ma=4.6时,可以控制圆柱脱体激波的激波强度。     

等离子体气动激励器布局对加速效应影响的实验研究

等离子体气动激励器作为等离子体流动控制的执行元件,其性能优劣对流动控制效果有重要影响。诱导气流速度是表征等离子体流动控制能力、衡量等离子体气动激励器性能的一个重要指标。研究了等离子体气动激励器的电极宽度、厚度、电极组内间距、绝缘材料介电常数和厚度等布局参数对诱导气流速度的影响。实验结果表明:选择介电常数合适、尽可能薄的绝缘材料,宽度较大、尽可能薄的条状电极,电极组内间距为1 mm左右的等离子体气动激励器,可提高等离子体气动激励诱导的气流速度。     

基于纳秒脉冲等离子体气动激励的翼型失速涡控制研究

为了揭示纳秒脉冲等离子体气动激励与附面层耦合作用机制,首先开展了NACA0015翼型的大迎角粘性绕流数值模拟,比较了3种典型湍流模型(S-A模型、standard k-w模型和SST k-w模型)对计算结果的影响,分析得到了翼型的近场旋涡分离流动流场结构特性,并对升力特性进行了频谱分析,得到了翼型非定常流动特征频率。进一步开展了基于脉冲等离子体气动激励的翼型大迎角绕流的频率耦合的风洞实验,实验结果表明:当固定激励电压,纳秒脉冲的激励频率大于或等于流场旋涡脱落频率时,控制效果最好,可在来流速度为100 m/s、攻角为22°时,可将翼型的升力系数增大18.1%,阻力系数减小22.5%。研究结论有助于揭示纳秒脉冲等离子体气动激励进行涡控制的作用机理,从而提高纳秒脉冲等离子体气动激励涡控制的能力。     

等离子体气动效应对燃烧室流场的影响

为了研究等离子体气动效应的内在机理,建立燃烧室助燃激励器中等离子体气动效应的数值仿真模型,通过求解电势方程和电荷密度方程,得到等离子体气动效应的体积力分布函数,将动量以源项的形式引入Navier-Stokes方程求解,对助燃激励器中等离子体气动效应诱导燃烧室空气流动进行了数值模拟,研究激励电压、气体流量和电荷密度对燃烧...     

Measurement method of plasma current and density in atmospheric pressure plasma jet

We present a measurement method of the plasma current and density in an atmospheric‐pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying a high RF voltage. The plasma in the form of a bullet is released as a plume or jet into the atmosphere. To study the characteristics of the atmospheric‐pressure plasma, the plasma current is measured using a current probe, and the drift velocity of plasma plume is measured using a photodetector. The current of the plasma plume is estimated by subtracting the ground line current from the power line current in the circuit. The density of plasma plume n is estimated from the plasma plume current I and the drift velocity v as I = envS, where S is the cross section of plasma plume. The density of the released plasma into the atmosphere is estimated as ∼10¹⁸ m⁻³ by the method. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Relation between plasma plume charge and length in atmospheric pressure plasma

We present atmospheric pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying a radio frequency high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. To study the formation of the plasma plume, the dependences of the plasma plume charge and the plasma plume length on the gas flow rate are examined. In a quartz tube with inner diameter 1.5 mm, which has more helium than air in the cross section of the flow channel, the distributions of the length and charge on the gas flow rate show similar tendencies. Consequently, when more helium gas is present than air, the travel length of the plasma plume correlates with the plasma plume charge. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

等离子体射流的推进机理

作为一种应用前景广阔的新兴等离子体源,大气压下非平衡等离子体射流在近10年的研究中取得了很大进展。为了更有效地利用等离子体射流,人们对其物理机理展开了深入研究,其中等离子体射流的传播机理尤其令人关注。一般认为等离子体射流的传播是受电场驱动的,但是最新的研究表明还存在另外一种驱动方式,即流体驱动。分别对以上两种驱动方式下射流传播的特点和影响因素进行了概述,并对电场驱动等离子体射流传播的空间特性、时间特性、极性效应,以及光电离的作用进行了讨论。流体驱动的等离子体射流与电场驱动的等离子体射流有着完全不同的传播过程,这种射流的传播是通过气流驱动的,具有推进速度相对较低,对电场不敏感等特性。最后,该文对大气压非平衡等离子体射流的传播机理中尚未解决的问题,以及未来的研究方向作了展望。     

等离子体环境中电磁兼容

文中力求通过实验研究与理论结合的方法，分析在等离子体环境中传播的电磁波与等离子体的相互作用。并设计加工实验装置以验证上述分析结果。     

等离子体射流及其医学应用

由于大气压非平衡等离子体射流装置能够在开放空间、而不是如传统放电仅在放电间隙内产生等离子体,这个显著优点对于许多应用,特别是近几年来兴起的等离子体医学方面的应用是至关重要的。为此,首先对大气压非平衡等离子体射流（N-APPJ）的研究现状进行阐述,结合作者课题组所作的研究,以及国内外其他研究者的成果,分别介绍几种以惰性气...     

等离子点火技术在福泉电厂的应用

详细介绍了贵州省首台600MW超临界机组福泉电厂2号机等离子点火技术的应用,并对贵州省较少使用的等离子无油点火技术要点进行总结,分析该系统的优势极其技术难点。     

等离子体点燃煤粉的热物理分析

电厂锅炉启停及低负荷稳燃过程中需消耗大量燃油，DLZ-200型等离子点火装置可以用等离子体直接点燃煤粉，节约燃油。综述了等离子体点燃煤粉的机理：其高温热化学作用可以生成低着火点的双组分燃料，再造挥发分，提高燃料的反应度，强化煤粉混合物的燃烧，等离子体中的活性原子可降低燃料的着火温度，加速热化学转换，促使燃料燃尽。等离子点火装置能够以较低的等离子点火功率点燃较大热功率的煤粉燃烧器。     

Numerical performance simulation of frozen helium plasma disk MHD generator

MHD electrical power generation with frozen helium plasma (FHP) is examined numerically. The FHP can be initiated by preionized helium without the alkali metal seed at the generator inlet. Since the three‐body recombination coefficient of helium ions is low at electron temperatures above 5000 K, the ionization degree can be kept almost constant in the entire region of the generator channel. The r?θ two‐dimensional numerical results show that the performance of the FHP MHD generator is comparable to that of the seeded plasma MHD generator, if the additional power consumed to preionization is ignored. In the FHP MHD generator, the ionization degree at the inlet should be controlled precisely, as well as the seed fraction in the seeded plasma MHD generator. Under an adequate inlet ionization degree for sustaining the FHP plasma, the plasma maintains the uniform structure. On the other hand, a slightly excess ionization degree causes a strong Lorentz force in the upstream region of the generator, deteriorating the generator performance. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 26–33, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10030     

Application of Magnetized Coaxial Plasma Guns for Simulation of Transient High Heat Loads on ITER Divertor

The magnetized coaxial plasma gun (MCPG) was investigated to seek possibilities of its application for a transient high heat testing to the ITER divertor surfaces. The experimental results showed that the MCPG could generate the hydrogen plasma stream with the ion energy of 50 eV, the peak energy density of 0.7 MJ/m² and the discharge duration of ∼0.05 ms. This capability is enough powerful to melt tungsten materials. Vaporization of a thin surface layer and a cloud of dense vapor plasma in front of the carbon calorimeter were observed by spectroscopic measurements. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Development of railgun accelerator at the institute of space and astronautical science (ISAS)

This paper describes the current status of the development of electromagnetic launchers such as the railgun at ISAS. The railgun is the most improved accelerator of Electromagnetic Launchers (EML). EML offers a potential for accelerating a projectile to much greater velocities than achieved with conventional powder guns or light gas guns. However, there has been little progress in increasing the velocity of EMLs since the experiment by Rashleigh and Marshall. A few experiments have been reported achieving velocities greater than 6km/s. The authors have achieved velocities greater than 6 km/s by reducing plasma leakage which is one of the factors limiting velocity. In this paper a 6 km/s launch is reported, compared with the results of two other shots considered from the viewpoint of plasma leakage, and the effect of entrainment of eroded material into the armature by rail ablation was discussed on the basis of simulated numerical calculations.