等离子体发生器放电参数对推进剂燃烧特性的影响

揭示了电热化学炮所用的等离子体发生器初始放电参数对推进剂燃烧特性的影响规律。实验主要在密闭药室里进行 ,研究了等离子体发生器中毛细管初始几何尺寸以及输入电能发生变化时 ,推进剂的燃烧行为发生的变化规律。研究结果表明 ,推进剂的燃烧行为对等离子体发生器初始放电参数有较强的依赖性。     

第9届全苏低温等离子体发生器学术会议

会议于1983年10月在苏联伏龙芝市举行,是1963年新西伯利亚第1届会议以来的20周年纪念。苏联44个城市143个科研、敦育、科研-生产联合体等单位300余名代表出席。200余篇报告涉及气体放电等离子体的理论与实验研究,电极现象的探讨,等离子体诊断方法和仪器的介绍,各类等离子体发生器的研究及应用,以及等离子体工艺过程的自动化等。分析世界等离子体技术发展的形势可知,等离子体化工和冶金的巨大飞跃和普遍应用业已成熟。为使等离子体工艺和技术达到最佳指标及等离子体发生器可靠应用和工艺流程顺利      

三相交流等离子体炉的传热计算

近年来,等离子体技术在化学工业与冶金工业方面的应用日益广泛。在提取冶金方面,直流等离子体发生器与交流等离子体发生器(有电极)容易得到大功率,设备费用也较射频等离子体发生器为低,从而显得更有前途。本文给出三相交流等离子体炉的一种简化模型的传热计算。     

螺旋波等离子体放电特性研究进展

螺旋波等离子体是目前低温等离子体产生密度最高的等离子体源之一,在材料处理、薄膜沉积、宇航推进、磁约束聚变以及基础等离子体物理研究等领域都有很大的应用潜力.近年来国内外研究者普遍关注这种高密度等离子体源,一方面人们对螺旋波等离子体的放电理论缺乏深入的认识,对等离子体激发和传播过程中能量的吸收存在多种假设,比较认可的是螺旋波等离子体通过螺旋波与TG波耦合效应实现能量沉积;另一方面,螺旋波等离子体放电过程中会表现出许多独特的现象,如低场峰、模式跃迁、无电流双层结构等,无法给出统一的解释,对这些放电特性的研究无疑有助于加深对螺旋波等离子体放电机制的理解.文章从放电机制和放电特性两方面出发回顾了近15年来螺旋波等离子体基础研究进展,总结了螺旋波等离子体放电过程中的低场峰现象、模式跃迁和无电流双层现象等研究结果.围绕螺旋波等离子体放电特性研究,展望了未来的研究重点,为理解螺旋波等离子体能量耦合机制,实现工业应用提供支撑.     

热等离子体科学技术的现状和发展

概述了热等离子体科学技术的现状和发展,介绍了一些工业应用和等离子体发生器。      

激光干涉诊断ETC发射装置产生的等离子体射流

叙述了用光楔错位干涉与高速摄影技术诊断电热化学（ＥＴＣ）发射装置中等离子体发生器产生的等离子体射流的方法，研究了等离子体射流与毛细管几何尺寸以及电源供能的关系。该方法有助于改进电热化学发射装置中等离子体发生器的设计及其效能的提高。     

非平衡等离子体对甲烷——氧扩散火焰影响的实验研究

利用自主设计的等离子喷注器采用介质阻挡放电方式产生非平衡等离子体,首先利用纹影技术、热电偶、单点红外测温等多种诊断方法实验研究了纯氧放电等离子体的电学特性、热效应及气动效应,然后通过可见光和化学自发辐射成像技术获得了火焰形态及特征参数,详细分析了等离子体对甲烷--纯氧扩散火焰形态和释热的影响,并计算了放电功率及费效比. 结果表明, 燃烧导致放电电流显著增大,其中电压幅值与氧气流速对放电电流大小的影响规律正好相反;与空气等离子体相比, 相同流量与电压条件下氧等离子体放电功率较高,但其发光强度明显较弱; 氧等离子体热效应微弱, 对燃烧的影响可以忽略,放电反应中释热过程主要由含氧组分决定;放电产生了具有3个速度分量的诱导射流, 增大了氧射流角,且电压越大越显著.等离子体主要通过气动效应改变了燃料与氧化剂的掺混,使得一定条件下火焰变得更稳定、释热更强.在所研究的范围内等离子体作用的费效比最低仅为2.2％,大流量、小混合比更有利.      

非平衡等离子体对甲烷–氧扩散火焰影响的实验研究

利用自主设计的等离子喷注器采用介质阻挡放电方式产生非平衡等离子体,首先利用纹影技术、热电偶、单点红外测温等多种诊断方法实验研究了纯氧放电等离子体的电学特性、热效应及气动效应,然后通过可见光和化学自发辐射成像技术获得了火焰形态及特征参数,详细分析了等离子体对甲烷–纯氧扩散火焰形态和释热的影响,并计算了放电功率及费效比.结果表明,燃烧导致放电电流显著增大,其中电压幅值与氧气流速对放电电流大小的影响规律正好相反;与空气等离子体相比,相同流量与电压条件下氧等离子体放电功率较高,但其发光强度明显较弱;氧等离子体热效应微弱,对燃烧的影响可以忽略,放电反应中释热过程主要由含氧组分决定;放电产生了具有3个速度分量的诱导射流,增大了氧射流角,且电压越大越显著.等离子体主要通过气动效应改变了燃料与氧化剂的掺混,使得一定条件下火焰变得更稳定、释热更强.在所研究的范围内等离子体作用的费效比最低仅为2.2%,大流量、小混合比更有利.     

双环状电极大气压等离子体射流的时间分辨诊断

大气压等离子体射流在众多领域中发挥着至关重要的作用,其中,拥有双环状电极结构的射流装置表现十分突出,此类装置具有结构简单、放电稳定的优势,并且产生的射流长度较长、温度较低.本工作利用ICCD相机采集技术,对高频高压交流电源驱动的双环状电极等离子体射流进行了纳秒级时间分辨诊断.研究发现,在一个完整的放电周期内,存在两个明显的放电阶段,分别位于外加电压的正、负半周期的峰值附近,并且在正半周期的放电阶段中,亮度、射流长度、放电发展速度均明显强于负半周期,值得注意的是,仅在负半周期的放电阶段中,才能观察到等离子体离开管口自主向前传播的现象.本工作对于了解等离子体动力学过程,揭示等离子体的行为规律及优化等离子体设备等诸多方面有积极地推动作用.     

铜丝电爆炸的光谱分析

通过搭建脉冲成形网络放电模块和光谱测试系统,利用Andor SR750光谱仪测量了铜丝电爆炸等离子体在400~500nm范围内的发射光谱。根据热力学平衡理论,采用双谱线相对强度法计算了等离子体的激发温度,并研究了激发温度随时间变化的特性。研究结果表明,铜丝电爆炸产生的稳态等离子体的激发温度约为5 400K。在脉冲放电前期,激发温度变化较大;在放电后期,激发温度较稳定;整个脉冲时间内激发温度差约达800K。     

Multirail electromagnetic launcher powered from a pulsed magnetohydrodynamic generator

The operation of an electromagnetic multirail launcher of solids powered from a pulsed magnetohydrodynamic (MHD) generator is studied. The plasma flow in the channel of the pulsed MHD generator and the possibility of launching solids in a rapid-fire mode of launcher operation are considered. It is shown that this mode of launcher operation can be implemented by matching the plasma flow dynamics in the channel of the pulsed MHD generator and the launching conditions. It is also shown that powerful pulsed MHD generators can be used as a source of electrical energy for rapid-fire electromagnetic rail launchers operating in a burst mode.     

Applicability of a one-dimensional model to the calculation of the properties of a plasma generator

Most engineering methods for calculating the properties of plasma generators use similarity theory to derive dimensionless equations to generalize experimental results [1]. Although their accuracy is acceptable for practical calculations, the equations cannot be used for a physical analysis of the local phenomena occurring in the working channel of a plasma generator. In the present paper the experimental data are compared with the results of a calculation of the local and integrated heat and gasdynamic properties of a dc plasma generator with a longitudinally injected arc. The basis of the computational method is a quasi-one-dimensional gasdynamic model of the flow of an electrically conducting gas in the channel of the plasma generator developed and studied in [2].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 122–126, July–August, 1977.In conclusion, the authors thank G. A. Lyubimov for valuable remarks.     

Solution of a variational problem for the flow in an MHD generator

The most complete study and construction of extremal plasma flow regimes in the channel of an MHD generator may be accomplished using the methods of variational calculus. The variational problem of conducting-gas motion in an MHD channel was first discussed in [1]. The general formulation of the problem for the MHD generator was considered in [2]. Solutions of variational problems for particular cases of extremal flows are given in [2–5].The present study obtains the solution of the variational problem of the flow of a variable conductivity plasma in an MHD generator which has maximal output power for given channel length or volume. An analysis of the solution is made, and a comparison of the extremal flows with optimized flow in a generator with constant values of the electrical efficiency and flow Mach number is carried out.     

Some electrodynamic effects in a MHD generator duct

Theoretical and experimental studies made in recent years show that the plasma flow in the duct of a real MHD generator differs significantly from the quasi-uniform model of the flow in an idealized MHD duct. This difference appears primarily in the analysis of the electrodynamics of the MHD generator. Usually the actual electrical characteristics of the generator are poorer than expected, which may be caused, in particular, by flow nonuniformities and electrical leaks in the duct. The influence of these factors shows up particularly strongly in the presence of the Hall effect.Some qualitative and quantitative estimates of these phenomena have already been made in the literature. The necessity for taking into account the influence of the cold boundary layer on the effective conductance of the plasma in the duct was shown in [1]; in [2] it was shown that this influence increases markedly in the presence of the Hall effect. The influence of shunting of the plasma by the electrically conductive walls of the duct was considered in [3–5].The present paper describes an analysis of the combined influence of the effects associated with flow nonuniformities and electrical leaks for the case of anisotropy of the plasma conductivity, and an example is presented of the calculation of flow in a MHD generator with finite variation of the parameters.     

Subsonic Radiation Gas Dynamics in a Laser Plasma Generator Channel

The radiation gasdynamic processes in the channel of an air laser plasma generator operating at atmospheric pressure are analyzed. In the multigroup approximation a numerical radiation gasdynamic model is formulated on the basis of the equations of motion of a viscous heat-conducting gas and the selective thermal radiation transport equation. Laminar and turbulent subsonic generator operation regimes are considered.For the purpose of approximately describing the turbulent gas and plasma mixing the Navier-Stokes equations averaged after Reynolds and the k-ε turbulence model are used. The problem is solved in the time-dependent two-dimensional axisymmetric formulation.Strong radiation-gasdynamic interaction regimes are investigated. In these regimes the energy losses due to radiation from the high-temperature region of the laser plasma and the absorption of its thermal self-radiation by the surrounding plasma and gas layers (radiation reabsorption) appreciably affect the gasdynamic flow structure. Two methods of integrating the selective thermal radiation transport equation in the generator channel are discussed. In one of these the thermal radiation transport is calculated inside the heated volume and in the other the radiation heat fluxes are calculated on the surfaces bounding the volume. The results of calculating the spectral and integral radiation heat fluxes on the inner surface of the generator are given.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, 2005, pp. 126–143.Original Russian Text Copyright © 2005 by Surzhikov.     

Performance investigation of plasma magnetohydrodynamic power generator

magnetohydrodynamic (MHD) power generator system involves several subjects such as magnetohydrodynamics, plasma physics, material science, and structure mechanics. Therefore, the performance of the MHD power generator is affected by many factors, among which the load coefficient k is of great importance. This paper reveals the effect of some system parameters on the performance by three-dimensional (3D) numerical simulation for a Faraday type MHD power generator using He/Xe as working plasma. The results show that average electrical conductivity increases first and then decreases with the addition of magnetic field intensity. Electrical conductivity reaches the maximum value of 11.05 S/m, while the applied magnetic field strength is B = 1.75 T. When B > 3T, the ionization rate along the midline well keeps stable, which indicates that the ionization rate and three-body recombination rate (three kinds of particles combining to two kinds of particles) are approximately equal, and the relatively stable plasma structure of the mainstream is preserved. Efficiency of power generation of the Faraday type channel increases with an increment of the load factor. However, enthalpy extraction first increases to a certain value, and then decreases with the load factor. The enthalpy extraction rate reaches the maximum when the load coefficient k equals 0.625, which is the best performance of the power generator channel with the maximum electricity production.     

Cathode spots on electrode slag films in an open-cycle MHD generator

A study has been made of the function of the electrodes (cathodes) in an open-cycle MHD generator for several different reasons [1–3], because the electrode processes have marked effects on the erosion and electrical characteristics of the electrodes. The specific features of the conditions in an MHD generator channel include, particularly, the high-temperature plasma composed of combustion products together with the deposition of potassium salts on the electrodes. These factors have a marked effect on the behavior of the cathode spots. In the case of an MHD generator fueled by coal, the plasma contains the incombustible mineral part of the fuel (ash). Therefore, the electrode surfaces receive not only potash salts, but also slag, which consists of various refractory oxides that differ from the potassium compounds in electrical conductivity, thermal conductivity, and emissivity. These films may substantially affect the parameters of the cathode spots, and hence the erosion, and the values may differ substantially from those given in [3]. We have examined the major features of the cathode spot behavior for an open-cycle MHD generator fueled by coal.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 29–33, July–August, 1976.     

Flow and Heat Transfer in Underexpanded Air Jets Issuing from the Sonic Nozzle of a Plasma Generator

We present the results of an experimental investigation and numerical simulation of the gasdynamic structure of underexpanded dissociated-air jets and the heat transfer in these strongly nonequilibrium flows under the test conditions realized in the 100-kW electrodeless VGU-4 plasma generator of the Institute for Problems in Mechanics of the Russian Academy of Sciences (IPM RAS). The flow and heat transfer analysis is carried out on the basis of measurements of the static pressure in the plenum chamber, at the sonic nozzle exit, and on the low-pressure chamber wall, the stagnation pressure on the jet axis using a Pitot tube, and the heat transfer at the stagnation points of water-cooled models placed along the jet axis. The numerical simulation, based on complete Navier-Stokes equations, includes the calculation of (1) equilibrium air plasma flows in the discharge channel of the VGU-4 plasma generator; (2) underexpanded nonequilibrium dissociated-air jet outflow into the ambient space; and (3) axisymmetric jet flow past cylindrical models.     

Development of localized arc filament RF plasma actuators for high-speed and high Reynolds number flow control

Recently developed localized arc filament plasma actuators (LAFPAs) have shown tremendous control authority in high-speed and high Reynolds number flow for mixing enhancement and noise mitigation. Previously, these actuators were powered by a high-voltage pulsed DC plasma generator with low energy coupling efficiency of 5–10%. In the present work, a new custom-designed 8-channel pulsed radio frequency (RF) plasma generator has been developed to power up to 8 plasma actuators operated over a wide range of forcing frequencies (up to 50 kHz) and duty cycles (1–50%), and at high energy coupling efficiency (up to 80–85%). This reduces input electrical power requirements by approximately an order of magnitude, down to 12 W per actuator operating at 10% duty cycle. The new pulsed RF plasma generator is scalable to a system with a large number of channels. Performance of pulsed RF plasma actuators used for flow control was studied in a Mach 0.9 circular jet with a Reynolds number of about 623,000 and compared with that of pulsed DC actuators. Eight actuators were distributed uniformly on the perimeter of a 2.54-cm diameter circular nozzle extension. Both types of actuators coupled approximately the same amount of power to the flow, but with drastically different electrical inputs to the power supplies. Particle image velocimetry measurements showed that jet centerline Mach number decay produced by DC and RF actuators operating at the same forcing frequencies and duty cycles is very similar. At a forcing Strouhal number near 0.3, close to the jet column instability frequency, well-organized periodic structures, with similar patterns and dimensions, were generated in the jets forced by both DC and RF actuators. Far-field acoustic measurements demonstrated similar trends in the overall sound pressure level (OASPL) change produced by both types of actuators, resulting in OASPL reduction up to 1.2–1.5 dB in both cases. We conclude that pulsed RF actuators demonstrate flow control authority similar to pulsed DC actuators, with a significantly reduced power budget.