Studies of a Magnetocumulative Source of Electromagnetic Pulses with a Double Inductive Energy Storage

An energy source based on a helical magnetocumulative generator with simultaneous initiation of an explosive charge on the axis was developed. The generator operates on a double inductive energy storage with current circuit breakers in each storage. The main analytical dependences of the pulse amplitude and shape on the parameters of the double inductive energy storage were obtained. In an experiment with such an energy source, a voltage pulse of 770 – 800 kV was obtained on a breaker made of electrically exploding wires. The voltage at possible load points was 1300 – 1350 kV. The duration of the voltage pulse edge from 0.1U _max to 0.9U _max did not exceed 0.5 sec.     

Calculating scheme and switching-on of the load of plane explosive-driven magnetic generators

A scheme is described for calculating explosive-driven magnetic generators, and analytical and numerical calculations are made of the problem of switching a generator on to a constant ohmic and induction load, to a load whose resistance rises linearly with the temperature, and to a plasma load with equilibrium radiation. In the latter case, a calculation is made of a variant involving switching on the load through a matched transformer.Translated from Zhurnal Prikladnoi Mekhanika i Tekhnicheskoi Fiziki, No. 2, pp. 37–41, March–April, 1973.     

Energy transfer from an inductive storage by means of an explosive current disconnect

Energy transfer from an inductive storage is considered for two types of systems: a disconnect with an intrinsic parasitic inductance for an inductive load and a purely resistive disconnect for a resistive load. Solutions are obtained for the voltage, power, and energy transferred to the load. The dependence of the efficiency of the device on its parameters is established.     

Optimal electromagnetic energy extraction from transverse galloping

A fully coupled electro-fluid-elastic model for electromagnetic energy harvesting from Transverse Galloping is presented here. The model considers a one degree-of-freedom galloping oscillator where fluid forces are described resorting to quasi-steady conditions; the electromagnetic generator is modelled by an equivalent electrical circuit where power is dissipated at an electrical load resistance; the galloping oscillator and the electromagnetic model are coupled appropriately. Two different levels of simplification have been made depending on the comparison between the characteristic electrical and mechanical timescales. The effect of the electrical resistance load on the energy harvested is studied theoretically. For fixed geometry and mechanical parameters, it has been found that there exists an optimal electrical resistance load for each reduced velocity. On the practical side, this result can be helpful to design tracking-point strategies to maximize energy harvesting for variable flow velocity conditions.     

Modal parameter prediction for structures with resistive loaded piezoelectric devices

Natural frequencies and damping ratios of a structure, with piezo devices bonded on it and shunted with a resistive load, depend on the electrical load itself. Therefore, several tests (experimental or numerical) ought to be carried out in order to determine the resistor which provides the maximum damping ratio for a mode of interest, and in turn the natural frequency of the whole structure. In this paper we present relationships which allow us to predict the modal parameters mentioned above, by using the natural frequencies of the structure when the external electrical circuit of the piezo device is in short or open conditions. Thus, only two tests would be necessary in order to obtain both the maximum damping ratio, introduced by the piezo device, and the natural frequency of the whole system. Besides, under an acceptable approximation, the resistive load, which should be used to obtain the maximum damping, can be obtained from the natural angular frequencies previously derived.     

Approximate similarity criterion for an arc of self-adjusting length burning in a plasma generator with vortex gas stabilization

Use of the theory of similarity to analyze experimental data on arc burning in plasma generators [1–3] has made possible a qualitative jump in methods of designing such devices. The success of this approach has raised the problem of finding similarity criteria giving a good generalization for each specific plasma generator model with allowance for the corresponding arc burning characteristics.We have obtained an approximate similarity criterion for the dimensionless potential drop along an arc burning in a plasma generator with vortex gas stabilization in the case when the length of the arc is determined by shunting [4], The results of an analysis of experimental data on arcs in plasma generators with air vortex stabilization are presented.In conclusion the author thanks B. A. Uryukov for his comments and A. D. Lebedev for assisting with the experiments. He is also grateful to M. F. Zhnkov for his constant interest.     

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.     

Electric field in the transverse cross section of the channel of an MHD generator

During the motion of a partially ionized gas in magnetohydrodynamic channels the distribution of the electrical conductivity is usually inhomogeneous due to the cooling of the plasma near the electrode walls. In Hall-type MHD generators with electrodes short-circuited in the transverse cross section of the channel the development of inhomogeneities results in a decrease of the efficiency of the MHD converter [1]. A two-dimensional electric field develops in the transverse section. Numerical computations of this effect for channels of rectangular cross section have been done in [2, 3], At the same time it is advisable to construct analytic solutions of model problems on the potential distribution in Hall channels, which would permit a qualitative analysis of the effect of the inhomogeneous conductivity on local and integral characteristics of the generators. In the present work an exact solution of the transverse two-dimensional problem is given for the case of a channel with elliptical cross section stretched along the magnetic field. The parametric model of the distribution of the electrical conductivity of boundary layer type has been used for obtaining the solution. The dependences of the electric field and the current and also of the integral electrical characteristics of the generator on the inhomogeneity parameters are analyzed.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 3–10, January–February, 1973.     

Energy characteristics of harmonic internal wave generators

The propagation of internal waves plays an important role in liquid media with layers that vary according to density (stratified liquids) and are located in a gravitational field, which include the Earth's atmosphere and oceans. Highly controlled experiments are essential for investigating efficient generators of internal waves (in particular, harmonic internal waves). Hence, it is important to compare the efficiences of various types of internal wave generators. This problem is considered for the simplest forms of stratification: discontinuous and uniform (with a constant buoyancy frequency N). Although there are very few studies of oscillations in the case of discontinuous stratification, there are even fewer investigations of uniform stratification (e.g., see [1–4]). A comparison of the efficiences of different types of generators has not been made for the latter case. This is done below on the basis of energy estimates for two types of generators: for objects (a sphere or cylinder) that undergo small harmonic oscillations in a liquid and for objects with pulsating volumes.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 53–59, July–August, 1986.     

基于等效电路法的变三角截面驰振压电能量收集研究

随着能源危机的逐渐加剧,人们对压电俘能器研究的投入也与日俱增,目前常见的研究压电俘能器的模拟方法只能研究其接入简单的单一电阻负载电路时的性能,且不能解决压电俘能器的高强度直流电路耦合问题。因此,本文借助二阶范德波尔控制方程将压电俘能器的主要部件等效为电子元件,进而基于等效电路法建立了与变三角截面驰振压电振动俘能器相对应的等效电路模型。借助风洞实验验证了所建立的等效电路模型的准确性。采用该模型研究了外接电路,钝体顶角,外接电阻和来流速度对变三角截面驰振压电俘能器输出电压,输出功率和响应位移的影响,结果表明,随着电阻的增大,输出电压逐渐增大且增长率逐渐减小。交直流电路的最佳负载分别为1.05 MΩ和1.4 MΩ,当风速为7.03 m/s,钝体顶角为90°时,交直流电路输出电压和输出功率的峰值分别为41.34 V,0.974 mW和50.8 V,0.616 mW。随着钝体顶角的增大,输出电压,输出功率和响应位移均逐渐增大且增大的速度逐渐减小。等效电路模型可以高效,准确地对不同结构参数下和外界电路下的压电振动俘能器的输出功率,输出电压,响应位移及其影响因素进行研究,所提出的等效电路模型于加快对压电振动俘能器的研究与推广应用具有一定意义。     

核电690合金传热管微动疲劳试验及损伤机理分析

核电蒸汽发生器传热管在微幅磨损与交变载荷的作用下形成微动疲劳,导致其表面裂纹萌生和扩展乃至破裂,从而影响反应堆的安全. 为研究径向载荷以及轴向交变应力对690合金管微动疲劳寿命的影响规律,开展690合金管管材的微动疲劳试验,获得690合金管管材的微动疲劳寿命曲线,并与相关研究数据进行对比分析,以便探讨材料在微动疲劳下的寿命模型. 对不同载荷下的690合金管试样的磨痕表面进行三维形貌和扫描电镜观测,分析磨损表面的损伤机理;对不同载荷下的690合金管试样断口的宏观与微观形貌进行表征,分析裂纹萌生、起裂过程及其失效机理. 结果表明690合金管与403不锈钢(SS)抗振条间的磨损机理为剥层及磨粒磨损;690合金管在径向载荷作用下于微动磨损处产生裂纹源,裂纹在轴向交变应力的作用下不断向内部扩展,最终导致断裂;其断裂形式为解理疲劳断裂.      

Direct Conversion of the Energy of Laser and Fusion Plasma Clouds to Electrical Energy During Expansion in a Magnetic Field

The paper deals with the physical and electrotechnical principles of the promising method of direct conversion of the kinetic energy of an expanding plasma cloud to electrical energy by inductive generation of currents in short–circuited load coils that enclose the plasma and are oriented across the external magnetic field. An analysis of plasma deceleration by a magnetic field and transfer of plasma energy to an inductive load gave a solution of the problem in general form and the dimensionless parameters of the problem that determine the deceleration radius, the coil current, and the theoretical conversion efficiency. The role of the basic physical effects, including parasitic ones (plasma instabilities and Joule heating), influencing the real efficiency is assessed. A comparison of the results with data of experiments with laser–produced plasma clouds on a KI–1 facility and with available numerical results shows that in the optimized version of the method for conversion of inertial confinement fusion energy, a 30% efficiency can be achieved.     

Nonlinear buckling of torsion-loaded functionally graded cylindrical shells in thermal environment

Based on the nonlinear large deflection theory of cylindrical shells, this paper deals with the nonlinear buckling problem of functionally graded cylindrical shells under torsion load by using the energy method and the nonlinear strain–displacement relations of large deformation. The material properties of the functionally graded shells vary smoothly through the shell thickness according to a power law distribution of the volume fraction of the constituent materials. Meanwhile, on the base of taking the temperature-dependent material properties into account, various effects of external thermal environment on the critical state of the shell are also investigated. Numerical results show various effects of the inhomogeneous parameter, the dimensional parameters and external thermal environment on nonlinear buckling of functionally graded cylindrical shells under torsion. The present theoretical results are verified by those in literature.     

Breakdown of the near-electrode layer in a flow of ionized gas

An electric discharge in a flow of ionized gas is widely used in many physics and engineering problems. Among them are problems associated with current flow in various magnetohydrodynamic devices (generators, accelerators), arc shunting in a plasmatron, physical experiments in shock tubes, etc. It is known that with cold electrodes providing the contact between the plasma and the external circuit and relatively high pressures, two modes of current flow occur: at low current, the discharge is of a distributed nature; as the applied voltage increases, the discharge abruptly shifts into a discharge with a clearly developed cathode spot at some critical current density (we call this form of discharge an arc discharge). Existing experimental data [1–20] refers to varying experimental conditions. Furthermore, the critical voltage (or current) at which the transition of the discharge from a distributed discharge to an arc discharge occurs varies within very broad limits. From an analysis of the experimental data, a condition is formulated which the discharge parameters satisfy at the time of transition from a distributed discharge to an arc discharge.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 16–23, May–June, 1973.The author thanks Yu. A. Nikuev for invaluable help in the analysis of experimental data.     

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.     

Generation of electromagnetic energy in a magnetic cumulation generator with the use of inductively coupled circuits with a variable coupling coefficient

A method of generation of electromagnetic energy and magnetic flux in a magnetic cumulation generator is proposed. The method is based on dynamic variation of the circuit coupling coefficient. This circuit is compared with other available circuits of magnetic energy generation with the help of magnetic cumulation (classical magnetic cumulation generator, generator with transformer coupling, and generator with a dynamic transformer). It is demonstrated that the proposed method allows obtaining high values of magnetic energy. The proposed circuit is found to be more effective than the known transformer circuit. Experiments on electromagnetic energy generation are performed, which demonstrate the efficiency of the proposed method.     

爆炸式电磁感应脉冲发生器

为了探索脉冲发生器新的技术方法,在传统脉冲发生器的基础上,提出了一种依靠爆炸驱动的电磁感应脉冲发生器。介绍了发生器的工作过程,对发生器中炸药的爆炸和冲击过程进行了计算和数值模拟,建立了带有初始电压和初始静磁场的发生器的工作电路模型,得出了感应电压的计算方法。设计了一种通过永磁体提供初始静磁场的脉冲发生器,并分别对装有两种不同炸药的发生器进行了实验。实验表明:爆速较高的炸药驱动发生器可产生峰值更高的电压脉冲。实验结果偏低于计算结果,原因是理论计算中简化了磁芯磁场和冲击波速度。     

Front sections of bodies of revolution with annular channel and nearly minimal wave drag

A study is made of the problem of constructing the generator of the outer part of a body of revolution with annular channel that in the case of supersonic flow with attached shock wave realizes nearly minimal wave drag for fixed dimensions. The complete equations for the flow of an ideal (inviscid and non-heat-conducting) gas are used. The construction is completed by numerical solution of Cauchy and Goursat problems by the method of characteristics. Conditions of optimality are obtained by means of the method of an undetermined control contour [1]. One of the conditions cannot be satisfied, which makes the approach approximate. Nevertheless, the smooth nonoptimal generators which are obtained give compared with straight generators almost the same gain (up to 12% for the wave drag coefficient) as the optimal contours with bends constructed using an exact and much more complicated method [2]. At the same time, the gain with respect to generators that are optimal in the approximation of Newton's formula is much less (from a few tenths to 1 of a percent). It is established that the expression for the drag of optimal bodies with annular channel obtained in the framework of a linear theory [3; 4] gives in the considered problem, in contrast to the problem of an optimal rear section, not only quantitatively but even qualitatively incorrect results.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 138–145, January–February, 1984.     

Influence of stretch and temperature on the energy density of dielectric elastomer generators

Application of dielectric elastomers(DE) has remarkably increased in mechatronics because they are suitable candidates for energy harvesting due to their low cost,light weight, and high energy density. The dielectric elastomer generators(DEGs) exhibit high performance regardless of the applications scale. However, functioning as a generator, a DE may lose its efficiency due to several failure modes including material rupture, loss of tension(LT), electrical breakdown(EB), and electromechanical instability(EMI). The failure modes confine the area of allowable states for generation process.Dielectric constant and dielectric strength of such elastomers depend on the amount of applied deformation and also working temperature, which are often ignored in theoretical simulations. In this paper, variations of the above-mentioned parameters are considered in mechanical and electrical modellings to investigate their effects on energy density and efficiency of generators. Obtained results show that, ignoring the variations of material dielectric constant and dielectric strength leads to overestimation of the specific energy.Furthermore, it is shown that, for an acrylic-based generator, the specific energy sharply decreases with temperature rise.     

Analysis of the Effect of Changed Curvature and Load Distribution on the Deformation of a Flexible Long Cylindrical Shell

The effect of changed curvature and load distribution on the deflection–load relationship is studied based on the exact analytical solutions of the nonlinear problem on the deformation of a flexible long noncircular cylindrical shell with clamped and hinged edges under a nonuniform normal load. Graphs show how changes in the curvature and load parameters affect the upper critical load.