共查询到20条相似文献,搜索用时 31 毫秒
1.
The feasibility of using nonmechanical (electrogasdynamic, EGD, and magnetohydrodynamic, MHD) methods to control shock-wave
configurations emerging in supersonic flows is investigated. In the EGD method, the flow is heated by a gas discharge; in
the MHD one, the flow is influenced by a Lorentz force arising in a gas discharge upon applying a magnetic field. The influence
of the gas discharge and MHD interaction on the position of a detached shock wave appearing in a supersonic xenon flow about
a semicylindrical body is studied. A discharge is initiated in the immediate vicinity of the leading edge of the body, and
the variation of the shock wave position with the intensity of the discharge (discharge current density) is traced when the
influence of the EGD action increases and/or an external magnetic field is applied (the influence of the MHD action increases).
Preliminary data for a supersonic air flow about a body are presented. 相似文献
2.
V. L. Bychkov L. P. Grachev I. I. Esakov A. A. Ravaev K. V. Khodataev 《Technical Physics》2004,49(7):833-838
A longitudinal dc electric discharge in a submerged high-pressure supersonic air jet is described. Photographs of the discharge
are provided. The experimental voltage across the discharge gap and the discharge current are given for two resistances of
the resistor that limits the discharge current over a certain range of the discharge channel length along the air flow. The
current-voltage discharge characteristic is provided at a constant discharge length. The main discharge characteristics are
obtained from a comparison of the experimental and theoretical results calculated on the basis of the simplest model. 相似文献
3.
A microwave discharge initiated by a surface wave on a dielectric body placed in a supersonic air flow is studied. The discharge
is shown to represent a thin plasma layer that uniformly covers the antenna surface. In experiments, the discharge propagation
velocity may be as high as 100 km/s, which is several orders of magnitude higher than the velocity of sound in air. The peak
pulse power necessary to excite the discharge in a wide range of air pressures (from 10−3 to 103 Torr) is no higher than 100 kW. It is shown that the gas temperature may rise to 1000–2000 K, rapidly increasing (with a
rate of ≈50 K/μs) at the early stage of discharge evolution. The discharge of this type may find applications in super-and
hypersonic plasma aerodynamics (such as control of the flow near the surface of a body moving in a dense atmosphere, reduction
of surface friction, optimization of ignition and combustion conditions for supersonic flows of gaseous fuel, etc.). It may
also be used to advantage in development of new-generation plasma sources for micro-and nanoelectronics purposes (plasma treatment
of surfaces, etching, and film deposition). 相似文献
4.
基于介质阻挡与准直流电弧放电的物理过程, 分析了它们的气动激励机理, 建立了各自的气动激励模型, 并分别研究了它们对低速和超声速流动的激励效果. 结果显示: 介质挡板放电等离子体气动激励机理是改变了连续流体中的三种力, 即由牛顿内摩擦引起的剪切应力、由电动力学引起的体积力及由压力突变引起的冲击力, 其中基于电动力学的体积力效应占主导地位; 临近空间环境中体积力的作用效果更强, 诱导速度更大; 超声速来流下准直流电弧放电气动激励机理主要是等离子体的热阻塞效应, 本文所建立的爆炸丝传热模型可以用于仿真其控制激波的过程; 热电弧对于超声速来流而言就像一个具有一定斜坡角度的虚拟突起, 可用于高超声速飞行器前体激波的控制. 相似文献
5.
将实验测得的电弧放电能量分布规律拟合为理想热源,采用数值仿真方法对一种高频等离子体射流激励器进行参数化研究,探索了激励器出口角度对激励器静特性的影响,并获得了在超声速来流(Ma0=2.0)情况下射流激励器的高速特性。结果显示:当射流出口流通面积相同时射流出口角度越小,激励器沿流向的动量注入能力越强,并且这一规律在高速射流条件的情况下仍然适用。相比静止条件,在超声速来流条件下,射流的动量注入能力更强,影响域更大。 相似文献
6.
The characteristic of surface arc plasma included millisecond and microsecond actuation in supersonic flow is investigated both experimentally and numerically. In the experiment, the discharge characteristic of surface arc plasma in quiescent air and supersonic flow is recorded. The stable oblique shock could be observed with millisecond actuation. And the unstable compressive wave could be also observed with microsecond actuation. In the numerical investigation, plasma actuation is defined as a source term with input power density from discharge V–I characteristic, which is expected to better describe the influence of heating process. The numerical results are coincident with experimental results. In order to confirm the capability of surface arc plasma actuation to control supersonic flow, experimental investigations on control shock induced by ramp and separation of boundary layer induced by impinging shock are performed. All the results demonstrate the control effect of surface arc plasma actuation onto supersonic flow. 相似文献
7.
A. F. Aleksandrov V. M. Shibkov L. V. Shibkova 《Moscow University Physics Bulletin》2008,63(5):365-366
The influence of nonequilibrium plasma of the surface microwave discharge on the ignition of supersonic (M = 2) propane-air flow, as well as alcohol, benzene, and kerosene for sub- and supersonic air flow is studied. 相似文献
8.
为了增强等离子体激励器的扰动能力、提升等离子体气动激励的控制效果,采用高压探针、烟流显示和PIV流场测试等多种研究手段,开展了磁场加速等离子体激励器特性研究,获得了激励器不同时刻的放电图像,分析了磁场强度对激励器电学特性与诱导流场特性的影响规律.结果表明,(1)放电等离子体的定向运动速度与磁场强度成正比,磁加速等离子体的最大移动速度达到了6 m/s;(2)通过对不同剖面的诱导流场进行研究发现,磁场加速等离子体激励器能够在近壁区产生一系列涡结构.此外,该诱导流场具有显著的三维特征与非定常特性.研究结果为开展基于磁加速等离子体气动激励的流动控制奠定了基础. 相似文献
9.
In this work, the effect of electrical discharge on nitrate concentration is considered in aqueous solution. The atmospheric pressure plasma was produced by a high-voltage power supply at 27 k Hz using pin-to-pin configuration. Air, argon,and argon/methane mixture were used to study the working gas effect. UV-VIS spectroscopy and ion chromatography were used to analyze the effect of the electrical discharge on nitrate concentration in deionized water. Optical emission spectroscopy(OES) was applied to diagnose active species inside and on the surface of the deionized water solution. The results of the present work showed that the atmospheric pressure electric discharge with air increases nitrate concentration while it remains constant using argon and argon/methane electrical discharges. It was also revealed that in the presence of air, the electrical discharge reduces p H, acidifying the solution and increasing solution conductivity due to production of extra nitrate ions. On the other hand, argon electrical discharge increases p H and conductivity due to production of OHion in water. 相似文献
10.
The potential of using the Euler equations to numerically simulate the evolution of localized energy deposition zones interacting with a normal shock in quiescent air and in a supersonic channel flow is demonstrated. Simulation results are compared with available experimental data for an optical discharge in quiescent air and with results calculated for a supersonic flow using the Navier-Stokes equations with allowance for real gas effects. The possibility of predicting gasdynamic effects using the T- and q-models of energy deposition for perfect gas is justified. The variation of the gasdynamic structure and flow parameters near an energy deposition zone developing in a quiescent medium and interacting with a normal shock is analyzed in detail for different energy deposition powers. 相似文献
11.
Experimental data for magnetohydrodynamic (MHD) action on a supersonic nitrogen flow about an axisymmetric model are presented.
The experiments were carried out in the Big Shock Tube (Ioffe Physical-Technical Institute), at the end of which a test section
equipped with a supersonic nozzle was mounted. A test conic model coupled with a cylinder is attached to the output cross
section of the nozzle. A magnetic field is produced by a solenoid placed on the cylindrical part of the model through which
a pulsed current due to an external voltage source discharging passes. Electrodes on the conic part of the model initiate
a gas discharge, which rotates about the axis of the model in the solenoidal magnetic field. The influence of the magnetic
field on the gasdynamic pattern of the flow near the model and on the heat flux toward its surface is investigated. Schlieren
patterns of the flow about the model, photographic scans of the discharge glow, and heat flux measurements are taken. It is
found that the magnetic field has an effect on the gasdynamic pattern of the flow near the model and on the heat flux toward
its surface. The dependence of MHD effects on the external voltage polarity is also revealed. 相似文献
12.
The flow of a nonequilibrium gas-discharge plasma around a semicylindrical body is studied. The aim of the study is to see
how a change in the degree of nonequilibrium of the incoming plasma changes the separation distance between a shock wave and
the body. Experiments are carried out with a supersonic nozzle into which a semicylindrical body is placed. The inlet of the
nozzle is connected to a shock tube. In the course of the experiment, electrodes built into the wall of the nozzle initiate
a gas discharge in front of the body to produce an additional nonequilibrium ionization in the stationary incoming supersonic
flow. The discharge parameters are selected such that the discharge raises the electron temperature and still minimizes heating
of the gas. The degree of nonequilibrium of the flow varies with gas-discharge current. Diagnostics of the flow is carried
out with a schlieren system based on a semiconductor laser. The system can record flow patterns at definite time instants
after discharge initiation. 相似文献
13.
V. F. Tarasenko S. K. Lyubutin S. N. Rukin B. G. Slovikovskii I. D. Kostyrya V. M. Orlovskii 《Technical Physics》2005,50(11):1462-1466
The subject of study is ultrashort avalanche-produced electron pulses generated in air under atmospheric pressure. The current
amplitude of the pulses behind 45-μm-thick AlBe foil exceeds 100 A, and their FWHM is ≈0.2 ns. The conditions of generation
of ultrashort pulses persist at repetition rates as high as 1.5 kHz. A volume discharge initiated in an open coaxial-electrode
gas diode by high-voltage nanosecond pulses generates hard (> 60 keV) radiation. 相似文献
14.
《Journal of Electrostatics》2006,64(6):416-421
The decoloration efficiency of azo dye (Acid Orange 7, AO7) using a multi-needle-to-plate high-voltage pulsed corona discharge system was investigated in this paper. The effect of several parameters, including peak pulse voltage and pulse frequency of the discharge system, initial pH and electrical conductivity of the dye solution, mode of needle electrode distribution and gas flow rate on the decoloration rate of the dye wastewater was reviewed. The results obtained show that the pulsed discharge system with a multi-needle-to-plate electrode could dispose azo dye wastewater efficiently. The decoloration rate increased with an increase in applied peak pulse voltage and pulse frequency. Decoloration was more efficient in the acidic solution, and the decoloration rate displayed no marked change under solutions of differing electrical conductivity. For the case in which we example the effect of gas flow rate on the decoloration efficiency of Acid Orange solution, we found that better decoloration efficiency occurred using the seven-needle-to-plate discharge system, which had more discharge anodes. 相似文献
15.
Electric discharge in a supersonic air jet is studied. It is ignited in a linearly polarized quasi-optical microwave electromagnetic
beam the initial field intensity of which is much lower than the breakdown level. Electric breakdown is initiated by a tubular
electromagnetic vibrator, one end of which has spikes and is covered by a quartz tube. Atmospheric air enters into a low-pressure
working chamber through the inner channel of the vibrator. As a result, an immersed supersonic air jet forms in the chamber
at the outlet from the quartz tube. A microwave discharge ignited in this jet is “attached” to aft spikes of the vibrator.
The energy deposit into the discharge plasma and the effective area of energy interaction between the discharge and excited
microwave field are estimated from the temperature and stagnation pressure distributions in the wake of the discharge. 相似文献
16.
The present study deals with the visualization of the air flow inside a supersonic ejector. Our attention is more precisely
focused on the choked flow phenomenon which occurs along the mixing chamber of the secondary nozzle and which can be visualized
by CFD. Laser tomography visualizations are used to validate the CFD model. The evolution of flow configuration in the ejector
with the primary stagnation pressure is examined both in the case of zero secondary flow and in the case of free entrainment
of induced air. 相似文献
17.
D. F. Latfullin I. V. Mursenkova N. N. Sysoev 《Moscow University Physics Bulletin》2009,64(3):352-354
The supersonic air flow at Mach numbers of 1.1–1.6 in a shock tube is experimentally investigated during initiation of nanosecond
pulse surface sliding discharges. The shadow images of the flow field after discharge initiation, which characterize the dynamics
of shock waves propagating from the discharge area, are obtained. Periodic pressure pulsations on the shock tube channel wall
are recorded. The pressure dynamics is shown to correspond to both the motion of shock waves from the discharge area and a
supersonic flow of the discharge-excited gas near the channel wall. The pressure increase on the shock tube channel wall was
6–18%, as compared to the pressure in an unperturbed flow.
Original Russian Text ? D.F. Latfullin, I.V. Mursenkova, N.N. Sysoev, 2009, published in Vestnik Moskovskogo Universiteta.
Fizika, 2009, No. 3, pp. 114–116. 相似文献
18.
Wind tunnel experiments on flow separation control of an Unmanned Air Vehicle by nanosecond discharge plasma aerodynamic actuation
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Plasma flow control(PFC) is a new kind of active flow control technology, which can improve the aerodynamic performances of aircrafts remarkably. The flow separation control of an unmanned air vehicle(UAV) by nanosecond discharge plasma aerodynamic actuation(NDPAA) is investigated experimentally in this paper. Experimental results show that the applied voltages for both the nanosecond discharge and the millisecond discharge are nearly the same, but the current for nanosecond discharge(30 A) is much bigger than that for millisecond discharge(0.1 A). The flow field induced by the NDPAA is similar to a shock wave upward, and has a maximal velocity of less than 0.5 m/s. Fast heating effect for nanosecond discharge induces shock waves in the quiescent air. The lasting time of the shock waves is about 80 μs and its spread velocity is nearly 380 m/s. By using the NDPAA, the flow separation on the suction side of the UAV can be totally suppressed and the critical stall angle of attack increases from 20° to 27° with a maximal lift coefficient increment of 11.24%. The flow separation can be suppressed when the discharge voltage is larger than the threshold value, and the optimum operation frequency for the NDPAA is the one which makes the Strouhal number equal one. The NDPAA is more effective than the millisecond discharge plasma aerodynamic actuation(MDPAA) in boundary layer flow control. The main mechanism for nanosecond discharge is shock effect. Shock effect is more effective in flow control than momentum effect in high speed flow control. 相似文献
19.
The finite-difference time-domain (FDTD) method is used to calculate electrostatic discharge (ESD) currents induced in a charged human body approaching a vehicle. Maximum current densities induced in the human body are much higher than the threshold current density of 1 μA/cm2 for the steady-state current flow cases, which may cause biological effects. It is found that the ESD current induced in the heart is smaller than the threshold current required to produce ventricular fibrillation in humans. The specific absorption (SA) induced in the human body is considerably smaller than the value of 28.8 J/kg regulated by the ANSI. 相似文献
20.
The results of an experimental study of the spatial structure of a high-voltage diffuse discharge in a wire-plane electrode system are presented. Self-organization of the discharge current channels into regular cells is observed in the plane perpendicular to the electric field vector. The dependences of the structural parameters of the discharge in centimeter-sized gaps on the interelectrode distance are studied at air pressures within the range 220–760 torr. Self-organization of the discharge structure is explained in terms of the electric interaction among charges of the diffuse channel heads during bridging of the gap. 相似文献