Experimental investigation of return currents in electrogasdynamic flows

An investigation is made of return electric currents in electrogasdynamic flows for laboratory sources of unipolar charged particles. These currents play an important role in the process of airplane electrification as a result of the work of jet engines. Models have been built, making it possible to study the behavior of return currents outside and inside an axisymmetric electrogasdynamic flow, in the absence (single-contour source) and the presence (double contour source) of an external annular neutral jet. It is shown that a rise in the return current J^– outside an electrogasdynamic jet is accompanied by a decrease in the take-off current J °. A decrease in the relative distance L from the source to an external grounded surface and an increase in the ratiov of the velocity of the external neutral jet to the velocity of the electrogasdynamic flow lowers J^– in both grounded and insulated models; in the latter case, where J ° J°0, there is an appreciable return current outside the jet. With an increase in the potential of the source from =0 to the floating potential, the current J^– rises, attaining a maximum, and then decreases. This effect is observed also when J^–=0 in both grounded and insulated models. For the case L–1,v=1, the theoretical and experimental dependences of J^– on the potential of the source , retarding the charged particles of the flow under transitional conditions, are in satisfactory agreement.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 127–134, January–February, 1978.In conclusion, the authors thank A. B. Vatazhin for his interest in the work, and A. P. Strekal and V. F. Kudryashov for their participation in the experiments.     

Experimental investigation of the active compensation of the electric charge of a body in a flow with ions and charged drops

Results of experimental investigation of the problem of active control of the charge acquired by a body (sphere) in flow with an electrically charged component (ions) and electrically charged dispersed phase (water drops) are obtained and analyzed. This situation is not uncommon during aircraft flight in a cloud front. Previous experimental studies have mainly considered flows without a dispersed phase. The required flow was created by introducing in a turbulent air-steam jet a corona discharge on whose ions “electric” condensation developed and on the growing drops that arose a charge was accumulated due to diffusion processes and directional ion motion in the electric field. On the sphere which was introduced in the charged jet a discharger (active compensator) with an autonomous high-voltage power source creating a potential difference between the discharger corona needle insulated from the body and the body surface was mounted. Measurements of the size and concentration of the drops ahead of the critical point of the sphere were performed. The electric currents to elements of the experimental electric system and the floating potential of the body were measured for various corona charge parameters and various voltages on the active compensator. An active control of the sphere charge, its complete removal and the recharge of the sphere, is realized.     

Free electrogasdynamic flows under conditions of unsaturation

An experimental study was made of electrogasdynamic flows behind sources of charged particles, working under conditions of unsaturation, for the purpose of studying the flow of unipolar reactive jets from present-day-airplane engines, which in a number of cases can work under these conditions. A special corona source was developed, with a change in the take-off current of the electrogasdynamic jet over wide limits; this source was used for the laboratory modelling of such processes. It is shown that the floating potential of an insulated source of charged particles is practically independent of the degree κ of saturation of the electro-gas-dynamic jet, i.e., of the value of the take-off current with a constant velocity of the flow; under these circumstances, the time required for establishment of the floating potential is inversely proportional to the value of κ. An investigation was made of the effect of the surrounding conditions on the characteristics of electrogasdynamic jet with different degrees of saturation κ. It was observed that a decrease in κ brings about an appreciable weakening of this effect.     

Determination of particle charge and size from the propagation of ultrasound in suspensions

The propagation of small perturbations in raulticomponent disperse media consisting of an uncharged dispersion fluid, positive and negative ions and charged particles or droplets of another fluid is investigated. When weak waves pass through emulsions and suspensions, because of the difference in the velocities of the ions and charged particles a non-uniform distribution of electric potential develops in the medium [1–3]. Expressions relating the amplitude of the electric potential and the amplitude of the fluid velocity in the wave, the particle charge and the parameters characterizing the medium are derived. Relations are obtained for the phase shift between the values of the electric potential and the fluid velocity. It is proposed to use the expressions obtained, which describe the propagation of ultrasound, for the experimental determination of the particle charge and other parameters of the disperse medium, in particular, the particle size.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 122–128, January–February, 1988.     

Effect of sound on a supersonic jet

It is known that under the influence of sound from an external source or the sound emitted by the supersonic jet itself at discrete frequencies in nonoptimal flow regimes the supersonic jet expands more rapidly and its range is reduced [1, 2], However, the mechanism of action of the sound on the supersonic jet has not been adequately investigated and, in particular, no one has determined the intensity of the external source capable of producing a marked change in the gas dynamic parameters of the jet, its characteristics or how the interaction process develops. These questions are examined below. By means of shadow photography with a pulsed light source it is shown that a significant change in the gas dynamic characteristics of the supersonic jet can be achieved by directing at its base along the normal to the jet boundary sound with an intensity corresponding to 0.1–0.2% of the total pressure in the jet. The appearance of large-scale disturbances on the irradiated side of jet and the directional emission of sound by the jet at the frequency of the external source are noted.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 170–174, November–December, 1989.The author is grateful to A. A. Kochetkov for assisting with the work.     

Use of the turbulence energy equation in the theory of jet flows

In this study some of the assumptions introduced in [1] in developing a closed system of equations for a turbulent boundary layer will be simplified. With the aid of the system of equations of [1], a theoretical solution is found for the problem of a jet in an accompanying flow, it being assumed that the structure of the jet turbulence depends solely on local conditions. Experiment has shown that the turbulence in such a jet does depend also on the prehistory of the flow. At large distances from the source, the theoretical characteristics of the jet agree well with the experimentally determined characteristics of the wake beyond a body. Also examined is the problem of the boundary layer between two homogeneous flows, flowing with different velocities.Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp. 75–81, March–April, 1973.     

Drop evaporation in a turbulent gas jet

Evaporation of a semidispersive drop system in a turbulent gas jet is considered. A method for calculating drop evaporation in a turbulent gas jet is proposed based on a simplified solution of the scattering problem for an evaporating admixture. Evaporation of water as it is atomized in a turbulent air jet is experimentally studied. Approximate agreement is obtained between the results of the calculations and experiments.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 73–79, January–February 1976.     

Transonic outflow of an imperfect gas from a vessel with plane walls

Transonic isentropic imperfect gas flows^* were investigated in the one-dimensional formulation in [2–5]. The problem of the transonic outflow of a jet of thermally perfect gas with equilibrium excitation of the vibrational degrees of freedom of the molecules (calorically imperfect gas) was investigated in the two-dimensional formulation in [6]. Below the problem of the transonic outflow of a real (thermally and calorically imperfect) gas from a vessel with plane walls is considered. A method of solution is proposed. Calculation results characterizing the effect of the angle between the walls and the stagnation parameters on the transonic outflow of air are presented.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.6, pp. 88–95, November–December, 1993.The authors are grateful to G. Yu. Stepanov for his interest in their work.     

Effect of surrounding gas on velocity distribution function of molecules in molecular beam

Molecular-beam methods have become widely used in recent times for the study of flows of rarefied gases [1]. However, the very first experiments with molecular beams for agasdynamic source [2] showed that the measured intensities fell below theoretical predictions. Most devices for the creation of a molecular beam by means of a gasdynamic source have pumping equipment of comparatively low capacity and beam formation in them occurs with residual gas present. It was shown [3] that the residual gas penetrates into the jet and significantly reduces the intensity of the molecular beam. This and subsequent work [4, 5] were confined to measurements of intensity (density) and there are no data in the literature on the effect of residual gas on other parameters of the distribution function. The present work was devoted to a study of the effect of residual gas on the distribution function in a molecular beam defined from a jet in the scattering mode [6]. The work was performed on the small molecular-beam generator [7] and on the VS-4 low-density gasdynamic tube [8] at the Institute of Thermal Physics, Siberian Branch, Academy of Sciences of the USSR. Measurements of the distribution function by the time-of-flight method [9] were performed on the small molecular-beam generator and measurements of gas density on the VS-4.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fizito, No. 4, pp. 11–19, July–August, 1976.The authors are grateful to A. K. Rebrov for valuable discussions.     

Efficiency of an electrostatically focused electron impact ion source

Summary Naidu [1] investigated the inverse problem of particle motion which specifies the electrostatic field to guide charged particles along a prescribed set of paraxial paths. As an example, an application to mass spectrometry was cited. From the theory an electric field was specified that should focus charged particles so that a gas source of greater efficiency than a modified Nier source appeared possible.An ion source is constructed employing the proposed focusing field. Experimentally the new source is found to have an overall efficiency of 4×10^–6, the same as the modified Nier source. The new ion source produces ions of 0.1 eV energy spread and a half angle of divergence of 0.5 deg. An explanation for the observed efficiency is given, and the reasons for the failure to improve the performance as predicted by Naidu are discussed.     

Propagation of an ion jet near a dielectric surface

Difficulties in determining experimentally the local electrical parameters of unipolar-charged jets are arousing interest in the theoretical investigation of electrogasdynamic (EGD) flows. Free EGD jets were examined, for example, in [1–3]. In order to control the charge on the dielectric parts of aircraft surfaces, which results from their static electrification and may have certain negative consequences [4], and, moreover, to influence the flow in the boundary layer use is being made of unipolar-charged jets propagating near the dielectric [5, 6]. In [6] the case of an ion jet near a dielectric surface possessing surface conductivity was investigated. In these circumstances it is possible to neglect charge diffusion, which considerably simplifies the problem. Space charge diffusion was taken into account in [7], but subject to certain very important simplifications. The author has calculated the electrical parameters of a unipolar-charged jet propagating in a viscous incompressible gas near an ideal dielectric plate, with allowance for surface and polarization charges and, moreover, the diffusion processes near the surface. An asymptotic solution is obtained for the equations of the ionic diffusion layer as the ratio of the thickness of the diffusion layer to the thickness of the hydrodynamic boundary layer tends to zero.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 174–180, September–October, 1984.The author is grateful to V. V. Mikhailov and A. V. Kazakov for valuable advice and comments.     

Electrode region of a weakly ionized plasma in chemical equilibrium

The paper is devoted to an analysis of the wall (electrode) region of disturbance of the electric parameters of a weakly ionized plasma, i.e., the region in which the concentrations of the charged particles and the values of the electric field change from the distributions corresponding to the conditions in the undisturbed plasma to the values determined by the boundary conditions on the wall.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 142–153, January–February, 1982.I thank G. A. Lyubimov and G. A. Tirskii for interest in the work and valuable discussions.     

Draft of a nozzle with the circulating outflow of a vortical flow of gas

The presence of circulation in an outflowing gas leads to a change in the working parameters of a nozzle. The question of the mass flow rate and the draft of a nozzle without a diffusor (a point) for twisted flows has been studied theoretically and experimentally [1–6]. The use of nozzles with a supersonic part introduces a considerable degree of complication into the method for the analytical calculation of the draft characteristics and the program for their experimental investigation. In [2, 7], a theory of a nozzle is formulated for a model of a potential circulating flow of gas; in [5, 8], an electronic computer was used to solve the complete system of the equations of gasdynamics for the motion of a rotating flow along a nozzle; in [7, 9], an investigation was made of a variational problem of the shaping of a diffusor for a circulation flow. The calculation of the draft, carried out in the above-mentioned communications (with the exception of [2], in which a study was made of a partial model of an eddyless rotational motion), is bound up with labor-consuming computer calculations. In the present article, in a development of [3, 6], a quasi-one-dimensional theory of a supersonic nozzle for a vortical flow of gas is formulated and verified experimentally.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 145–149, September–October, 1975.     

Parameters of flow near the axis in the shock layer in the interaction of a supersonic jet with a barrier

The axisymmetric interaction between a supersonic jet with a finite expansion ratio and a barrier is accompanied by the formation of complex sub- and supersonic flow in a shock layer whose thickness depends on the parameters of the jet and the position of the barrier. The main relationships of the interaction process have been established experimentally ([1–3] and others) and individual results of numerical calculations of such flows are known [4]. An analytical investigation of the parameters in the shock layer formed ahead of a plane barrier when an underexpanded jet impinges on it is presented below. The results of [5], where the region near the axis of a shock layer of arbitrary thickness is analyzed within the framework of a model of flow with a constant density, is placed at the basis of the analysis.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 63–70, September–October, 1978.The author thanks Yu. M. Tsirkunov for useful discussions.     

Flow around a sphere by a two-phase supersonic jet

Results are presented of a calculation of the flow around a sphere of a two-phase supersonic jet, discharging into a vacuum. Calculations were performed by the determination method with use of a difference grid constructed on the basis of characteristic ratios [1], The parameters of the unperturbed jet were determined with the two-velocity and two-temperature model of mutually penetrating flows of continuous media (gas and particles) [2, 3] by the network method [4]. In calculating the flow around the sphere, as in [5–7], it was assumed that the particles do not affect the gas flow in the shock layer. An analysis of the effect of particles on gasdynamic parameters in a shock layer was performed in [8].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 171–176, November–December, 1978.The authors are grateful to A. N. Nikulin for providing the program for calculation of flow about a blunt body by a uniform supersonic flow.     

Decay of a plasma produced by a pulsed beam of accelerated electrons in an He-Ne mixture at high pressure

Increased interest has recently been shown in the low-temperature plasma produced by the action of electron beams on dense gases. This interest is due to the possibility of investigating plasma-chemical reactions in highly nonequilibrium conditions [1] and also to the prospect of introducing new methods of pumping gas lasers: by recombination [12], charge transfer [3], the formation of complex compounds [4, 5], etc. The plasma in question is characterized by high rates of reactions involving charged and neutral particles, which largely accounts for the difficulty of investigating such a plasma experimentally. For instance, problems of determining the kind of ions predominating in the plasma, the mechanism of recombination decay, the nature of the luminescence on individual spectral transitions, etc., become nontrivial. In this paper we investigate the decay of a plasma in neon and in an He-Ne mixture at high gas pressure.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 16–22, January–February, 1978.We thank G. A, Mesyats for assistance in this work and Yu. I. Bychkov and V. V. Ryzhov for discussion of the results.     

电流动聚焦中非牛顿流体射流影响因素的实验研究

在一套流动聚焦装置上加载高压直流电场形成电流动聚焦,并开展了非牛顿流体带电射流的不稳定性特性实验研究。实验在自行设计的装置系统上完成,获得了电流动聚焦中非牛顿流体射流的流动状态,考察了不同控制参数下射流形态的变化。结果表明,由于非牛顿流体具有粘弹性,与牛顿流体相比,非牛顿流体带电射流体现了更复杂的流动特点。这些实验结果为我们理解复杂条件下非牛顿流体射流的流动机理提供了参考,也有助于深入的实验分析和理论研究奠定了基础。     

Interaction between an external compression shock and a blunt body in a hypersonic stream

A complex shock configuration with two triple points can occur during the interaction between an external oblique compression shock and the detached shock ahead of a blunt body (for instance, ahead of a wing or stabilizer edge). This results in the formation of a high-pressure, low-entropy supersonic gas jet [1–6]. Here two flow modes are possible [1], which differ substantially in the intensity of the thermal and dynamic effects of the stream on the blunt body: mode I corresponds to the impact of a supersonic jet [2–6], while the supersonic jet in mode II does not reach the body surface in the domain of shock interaction because of curvature under the effect of a pressure drop. Conditions for the realization of the above-mentioned flow modes are investigated experimentally and theoretically, and an approximate method is proposed to determine the magnitude of the compression shock standoff in the interaction domain. Blunt bodies with plane and cylindrical leading edges are examined. The results of a computation agree satisfactorily with experimental data.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 97–103, January–February, 1976.The author is grateful to V. V. Lunev for discussing the research and for useful remarks.     

Electric arc in a submerged gas jet

The results of photographic studies of the behavior of an electric arc in a submerged gas jet, using both regular photography and still and cine shadow photography, are presented. The interaction of the arc with the turbulent portion of the jet and the development of disturbances in the arc and the thermal layer around the arc dependent on initial jet velocity are noted. Experimentally obtained values for extent of the arc laminar zone, radius of arc thermal layer, and electric field intensity are compared with calculated values.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 17–23, September–October, 1971.     

Autowave flows of weakly conducting gas in rough channels in the presence of strong electromagnetic fields

The steady-state flow of a gas in a rough channel in the presence of strong transverse magnetic and electric fields is considered. It is shown that in this case there also exists a periodic regime consisting of a sequence of deceleration waves [5–7]. The periodic regime results from the action of the forces of resistance to the motion of the gas.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 152–158, January–February, 1989.The authors wish to thank A. A. Barmin and A. G. Kulikovskii for valuable discussions.