共查询到20条相似文献,搜索用时 250 毫秒
1.
T. A. Lapushkina S. V. Bobashev R. V. Vasil’eva A. V. Erofeev S. A. Ponyaev V. A. Sakharov D. Van Wie 《Technical Physics》2002,47(4):397-405
The possibility is investigated of influencing the shock wave configuration in a xenon plasma flow at the inlet of a supersonic diffuser by applying electric and magnetic fields. Flow patterns resulting from interaction of the plasma with external fields in the entire diffusor volume and its different sections are compared. The patterns are obtained by the Schlieren method using two recording regimes: individual frames or a succession of frames. The study focuses on the normal shock wave formation process under strong MHD interaction over the whole diffuser volume. Basic factors affecting the plasma flow velocity in the diffuser under externally applied fields are compared, namely, the ponderomotive force and the Joule heating of the gas by the electric field, which decelerate the supersonic flow, and the heat removal to the external electric circuit producing the opposite effect. It has been shown that the external fields are most effective if applied to the inlet part of the diffuser, while the flow in the diffuser section, where there is a large density of dissipative structures, is not readily responsive to external factors. It is suggested that the measure of response can be estimated by the energy that goes to the shock wave formation as a result of the flow interaction with the diffuser walls. 相似文献
2.
R. V. Vasil’eva A. V. Erofeev T. A. Lapushkina S. A. Poniaev S. V. Bobashev D. M. van Wie 《Technical Physics》2005,50(9):1132-1138
This paper elaborates upon a previous investigation into the influence of external electric and magnetic fields on a flow
through a supersonic diffuser. The aim of the present study is to correlate a change in the configuration of a shock wave
emerging near the diffuser inlet at magnetohydrodynamic interaction with the amount of force and energy actions and with total
pressure losses. For this purpose, the main parameters of the shock wave structure and the total pressure are measured at
the diffuser outlet when the flow is subjected to magnetic and electric fields of various strengths at different routes of
current passage. In the experiments, a shock tube with a supersonic nozzle is employed. The shock tube forms a flow behind
the shock wave reflecting from the end of the tube, which terminates in the nozzle. The diffuser is located directly downstream
of the nozzle. The investigation is carried out in xenon. The flow is subjected to external fields at the inlet of the diffuser.
The shock wave structure is visualized by frame sweeping of Schlieren patterns of the flow. The total pressure is measured
with a piezoelectric transducer located at the end of the channel. The results obtained make it possible to optimize the action
on the flow in terms of power consumption and total pressure losses for a given design of the diffuser. 相似文献
3.
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
4.
Propagation characteristics of a high-power electromagnetic wave through an inhomogeneous magnetized plasma is investigated. Considering the momentum transfer equations for electrons and ions and taking into account the ponderomotive force, the distribution of electron density and dielectric permittivity are obtained. Using non-linear dielectric permittivity and Maxwell's equations in the absence of external current and charge densities, non-linear wave equations are achieved. The results indicate that the external static magnetic field can modify the profiles of both the electric and magnetic fields. It is also shown that the external static magnetic field enhances the amplitude of the electron density and the non-linear dielectric permittivity. 相似文献
5.
以无缓冲气化学氧碘激光器(COIL)实验器件的数据计算得到的混合喷管出口参数平均值作为光腔入口条件,对6种不同构型的扩压器从光腔入口至扩压器出口的流场进行了数值模拟,得出了各流场参数分布;对不同构型扩压器的流场特点、总压恢复性能进行了分析;研究了扩压器出口背压对流场参数的影响。结果表明:对于主流无缓冲气的COIL,等截面扩压器具有较好的压力恢复性能;增大扩压器出口背压可以使扩压器的压力恢复性能提高,然而,较高的背压使激波串向光腔方向移动,从而使光腔流场受到干扰,影响光腔的光束质量。 相似文献
6.
采用低磁雷诺数磁流体数学模型,对外加磁场下的高超声速半球体流场进行数值模拟.选取三种简单理想磁场(轴向、径向、周向均布磁场),分析了不同磁场类型对流场结构、气动阻力与洛伦兹阻力的影响及作用机理.研究发现,轴向磁场径向"挤压"效应使得激波外形凸出,且壁面静压存在"饱和现象";径向磁场存在轴向"外推"效应,较大的磁场强度会导致肩部形成高温区;周向磁场下感应电场的存在导致增阻效果很差.进而对比了两种相同驻点磁感应强度特殊分布磁场(偶极子磁场、螺线管磁场)下的流场,发现了不同于理想磁场的径向"扩张"效应.按增阻效果从大到小依次为径向磁场、螺线管磁场、轴向磁场、偶极子磁场、周向磁场. 相似文献
7.
Nadja Vogel 《Applied Surface Science》2006,252(13):4850-4856
We present results where highly supersonic plasma jets and accelerated plasma fragments are generated by interaction of an intense picosecond laser pulse with a metallic target (Al, Cu, W, and Ta) in gas atmosphere. The formation of jets and well-localized massive plasma fragments occurs when a strong forward shock from a main laser pulse and a reverse shock from a pre-pulse meet to. Interferometric and shadow graphic measurements with high temporal (100 ps) and spatial (1 μm) resolution yield information about the formation and evolution of plasma jets and plasma fragments. The excitation of the electric and self-generated magnetic field by ponderomotive force during propagation of the laser pulse in a gas atmosphere was investigated as well. It had been shown previously that under certain conditions a hollow current channel can be generated in laser-produced plasma. The azimuthal magnetic field in such a micro-channel was determined by Faraday rotation of a probing laser beam to be 7.6 MGauss (MG). Ion acceleration in a pinched annular current channel up to 8 MeV analogous to micro-“plasma focus” conditions, may be realized at lengths of 100 μm. Self-generated magnetic fields of 4-7 MG have also been measured in thin skin layers in front of shock waves, where well-collimated plasma blocks were separated and accelerated away from the plasma body. The velocity of dense plasma blocks reaches values of order of 3 × 108 cm/s and they are stable during acceleration and propagation in gas. 相似文献
8.
Kobayashi H. Okuno Y. Kabashima S. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(5):1526-1531
Three-dimensional nonuniform plasmas and boundary layers have been studied numerically under an MHD interaction. The nonuniform plasma of “streamer” owing to weak ionization of seed material has a spiral structure in the r-&thetas; plane, and the plasma becomes almost uniform between the walls in the r-z plane. This structure is almost the same as that in our previous paper (1997), where the gas (heavy particle) properties are assumed to be invariant and steady. In addition to the streamer, the nonuniform plasma of “domain” owing to weak ionization of noble gas is revealed. The domain has the structure perpendicular to the streamer. In a strong MHD interaction case, the static pressure considerably increases in the upstream region of a generation channel, and the pseudo-shock waves appear in the generator, but the plasma is almost uniform along the &thetas; direction. The boundary layer in the strong MHD interaction is considerably thick, and in the broad region near the wall the Hall current flows reversely. In the weak MHD interaction case, the plasma forms a nonuniform structure along the &thetas; direction, and the Hall current does not always flow in the opposite direction even on the insulator wall since the azimuthal electric field is not zero 相似文献
9.
The purpose of this experiment was to find a way to increase the effective conductivity in a nonequilibrium MHD channel. The
working material used was inert gas without admixtures of alkali metals. The experiment was carried out in a disk MHD channel
coupled to a shock tube, with radial expansion of the gas and an axial magnetic field. An inset was located in a sector of
the disk channel with electrodes, to which a load was connected to extract power into an external circuit. Voltage-current
characteristics were recorded in this experiment along with the structure of luminous nonuniformities. The results of the
experiment showed that as ionization instabilities develop, the effective conductivity of the plasma increases with increasing
magnetic induction, and the extracted power density for fields above critical turns out to be roughly 30% higher than that
calculated by assuming that the conductivity is a constant.
Zh. Tekh. Fiz. 67, 12–15 (December 1997) 相似文献
10.
D. S. Munkhoz V. A. Bityurin A. I. Klimov P. N. Kazanskii I. A. Moralev L. B. Polyakov B. N. Tolkunov 《Technical Physics》2017,62(7):1013-1018
The structure and dynamics of a near-wall gas flow produced by a rotating electric arc discharge in an external magnetic field around a cylindrical model without an incoming flow has been investigated. The electric arc on the model has been produced by a combined electric discharge (low-current rf discharge + high-current pulse-periodic discharge). Permanent magnets with induction B ≈ 0.1 T have been placed inside the cylindrical models. Ring electrodes are arranged on the surface of the model. The structure and dynamics of the near-wall gas flow around the cylindrical model have been investigated using high-speed photography, as well as the shadowgraph and particle image velocimetry (PIV) methods. 相似文献
11.
In this paper, the growth rate, ponderomotive force and the exciting
condition for parametric instability are derived by considering the loss
reaction using a new method. On the basis of the hydrodynamic
equations, we take the production and loss reactions in plasma into account
to derive the coupling equations for the electron plasma oscillation and
ion acoustic oscillation, and obtain the growth rate for the parametric
instability, the ponderomotive force and the exciting condition. The result
shows that (a) the production reaction has no effect on the parametric
instability, and the effect of loss reaction on the parametric instability
is a damping one, (b) the more intensive the external field or pump is, the larger
the growth rate is, (c) there exist two modes of the ponderomotive force,
i.e.\ the high frequency mode and the low frequency mode,
and (d) when ponderomotive force counteracts the damping force, the
oscillations become non-damping and non-driving. The ratio of the
electron plasma oscillation to ion acoustic oscillation is independent of
the loss reaction and the external field. 相似文献
12.
13.
Averaged forces of Miller's type, acting on the particles of a bounded plasma in parallel external a. c. electric and d. c. magnetic fields, are found on the basis of the equations of the two-component MHD. It is assumed, that standing transverse waves are excited in the plasma by the external source before the a. c. electric field is switched on. 相似文献
14.
The ponderomotive force plays a fundamental role in the absorption of laser light on self-consistent plasma density profiles, in multiple-photon ionization, and in intense field electrodynamics. The relativistic corrections to the ponderomotive force of a transversely polarized electromagnetic wave lead to an approximately 20-percent reduction in the single particle ponderomotive force produced by a 10-?m 1016-W/cm2 laser field. Recent experimental investigations are based on using two intense laser fields to produce desired laser-matter interactions. This paper presents the first derivation of the nonlinear relativistic ponderomotive force produced by two intense laser fields. The results demonstrate that relativistic ponderomotive forces are not additive. 相似文献
15.
Kobayashi H. Satou Y. Okuno Y. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2002,30(6):2152-2159
In an magnetohydrodynamic (MHD) generator using a frozen inert gas plasma (FIP), the availability of a frozen argon plasma, the influence of plasma uniformity at the generator inlet on the performance, and the feasibility of a large-scale generator are numerically examined by /spl gamma/-/spl theta/ two-dimensional simulation. The FIP is produced by pre-ionizing inert gas without an alkali metal seed at the generator inlet, then the ionization degree of the plasma is kept almost constant in the whole of the channel because of considerable slow recombination of the inert gas just like frozen reaction plasma. It is found that not only helium, but also argon frozen plasma MHD generation is realized, although highly accurate control of inlet ionization degree is necessary for argon. It is important to reduce the nonuniformity of plasma properties at the generator inlet in order to raise the maximum enthalpy extraction ratio. Even for the large-scale generator with 1000-MW thermal input, the ionization degree is kept almost constant in the whole of the channel and the high performance is obtainable. This result is extremely attractive for the FIP MHD generator. 相似文献
16.
17.
作为一种新概念高超声速热防护手段,磁控热防护系统在实际应用中往往需要考虑霍尔效应的影响.为了在真实气体环境下求解霍尔电场,采用交替隐式近似因子分解法建立并验证了热化学非平衡流体域电场数值求解方法.分析了电场虚拟步进因子和收敛性的关系以及影响步进因子取值的因素,提出了当地变步进因子加速电场收敛方法.研究表明,存在一个最优的步进因子a_p使得霍尔电场收敛速度最快,并且随网格尺度的减小和霍尔系数的增加,最优步进因子a_p变大,电势场收敛速率变慢.对于局部加密网格而言,当地变步进因子法的电势收敛性明显优于常规的定步进因子法. 相似文献
18.
On the basis of the two-component MHD and a full electromagnetic treatment, nonlinear resonances of bounded plasma placed in crossed external a.c. electric and constant magnetic fields are found. 相似文献
19.
A. S. Filippov I. A. Korotkin A. A. Kanaev V. V. Kondakov I. O. Urazov O. A. Ushakova P. G. Yakovlev 《Journal of Engineering Thermophysics》2008,17(4):320-327
The results of numerical modeling of two-phase electrolyte thermo-and hydrodynamics in the working space of a separate electrolyzer
cell with vertical electrode arrangement are presented. The problem is solved in a self-consistent formulation taking into
account the electric current, Joule heat evolution, gas evolution, gas and liquid flows, and electric conductivity of the
disperse phase. Within the framework of the proposed two-liquid approach, near-wall bubbly flow is calculated using a model
of expanding gas plume, which is based on the introduction of an effective force acting upon the gas phase. The results of
several variants of such calculations are compared. The numerical solution is also compared to approximate analytical solutions
of the problem. The results of this study can be used to calculate estimations of the electrical and thermal regimes of vertical
electrolyzers. 相似文献
20.
采用基于OpenFOAM环境自主开发的低磁雷诺数磁流体求解器,对45°和90°突扩矩形管中液态金属流体在受到垂直流向的外加磁场作用时的速度、感应电流、压力的分布及突扩位置处的MHD三维现象进行数值模拟.结果表明:磁场沿突扩方向时,由于无回流涡,45°比90°突扩管在肩部位置速度分布更优.哈特曼数增大,强射流和突扩结构,在突扩肩部位置引发流动的不稳定性.伴随感应电流的不稳定,流动不稳定发展到突扩位置上游.磁场沿垂直突扩方向时感应电流的三维效应显著.哈特曼数增大,MHD压降显著增大.同方向磁场和相同哈特曼数,不同突扩角度的三维无量纲压力梯度无明显差异. 相似文献