RU2590893C1 - Method for producing impact-compressed plasma layer and device for its implementation - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to plasma physics, mainly to physics and engineering of processes accompanying supersonic flow about bodies with high-speed plasma flows, and can be applied, in particular, to simulating structure and radiation of impact compressed flow layer during movement of spacecraft, planetary probes, meteorites, and other space objects (SO) in earth atmosphere at heights of 30 to 200 km, and more. Method for producing impact-compressed plasma layer (IPL) by reacting coaxially arranged high-enthalpy jet with model body, and then picking up structure of disturbed area near model body; new feature is that high-enthalpy jet is formed by jet diaphragm discharge in vacuum under flow conditions of erosion plasma jets in interelectrode gap, under conditions of model body arrangement with characteristic size P, found from ratio P ≤ 0.5 R , where R is radius of annular electrode, cm; between plasma-forming diaphragm and ring electrode (cathode and/or anode), at speed V_∞ of surging plasma flow upon model body within diaphragm to ring electrode space, and with composition of plasma flow corresponding to selected composition of plasma-forming material of inner wall of main nozzle in diaphragm hole: i.e. chemical elements and stoichiometric coefficients of initial substance formula; wherein structure of IPL disturbed area is recorded by optical methods by value of repulse of IPL blast wave and by spectral methods by IPL luminescence. Device for implementing this method is also disclosed.

EFFECT: technical result is possibility to obtain impact-compressed plasma layer and plasma flow structure about model body of specified shape* high-speed, up to 50 km/s and higher flows of virtually any possible chemical and ionisation composition.

3 cl, 3 dwg, 1 tbl

Description

The invention relates to plasma physics, mainly to the physics and technology of processes associated with supersonic flow of bodies by high-speed plasma flows, and can be used, in particular, to model the structure and radiation of a shock-compressed layer of a stream during the motion of spacecraft, planetary probes, meteoroids and other space objects (KO) in the Earth’s atmosphere at altitudes of 30-200 km and above, when KO moves through the atmosphere of the planets of the Solar system, as well as studying the thermophysical properties of materials, we use x in the rocket and space technology.

The physics of the phenomena accompanying the entry of cosmic bodies into the Earth’s atmosphere is the subject of meteor astronomy research [1]. The physics of meteor phenomena is based on the processes of inhibition and mass loss of spacecraft in the atmosphere, the peculiarities of motion in the atmosphere of large bodies forming a shock wave and shock-compressed layer (CSS) with luminescence and ionization. The complexity of the problems associated with modeling the interaction of spacecraft with the atmosphere inevitably leads to the use of the concepts of gas dynamics, hypersonic aerodynamics and plasma physics.

Currently, in the development of optical-electronic equipment (OEA) in the framework of research programs, comprehensive studies of the radiation of the upper atmosphere of the Earth and near-Earth space in all ranges of the optical spectrum are carried out in order to obtain the data necessary for modeling atmospheric phenomena of natural and technogenic origin. As a result of the implementation of such programs, a new direction has been created in the development of the OEA - remote sensing of the Earth (RS) in the UV and VUV spectral ranges. Using it, they solve, in particular, the problems of observing the atmospheric emission of atmospheric oxygen by glowing near the object of an shock-compressed layer of air and the erosion products of its surface.

One of the main methods used in the study of the possibility of observing the CO entry into the atmosphere by the emission of a shock-compressed layer accompanying the motion of an object, along with the numerical method, is an experimental modeling method.

A known method of producing a shock-compressed layer [Theoretical and experimental studies of hypersonic flows in the flow around bodies and in traces. Ed. G.G. Cherny and S.Yu. Chernyavsky. Moscow, Moscow State University, 1979] by hypersonic flow of bodies around a body with a high-speed gas stream, where aeroballistic installations are used for the formation of CSS. At the same time, the required flight speeds of the body model are achieved using gas guns, and the model moves in undisturbed gas.

The disadvantages of this method are the restrictions on the maximum speed of throwing up to 10-12 km / s, the limited choice of shape and material of models of bodies for throwing.

A device for implementing this method is known [Theoretical and experimental studies of hypersonic flows during flow around bodies and in traces. Ed. G.G. Cherny and S.Yu. Chernyavsky. Moscow, Moscow State University, 1979], which is a two-stage gas installation and consists of a first stage chamber with compressed gas and a second stage, where a light working gas (hydrogen) is compressed, which in turn accelerates the body. The first stage uses compressed helium or products of gunpowder. Both stages are separated by a diaphragm or a free piston.

Due to large overloads of the propelled body, light-piston or diaphragm units are used only for aeroballistic studies of sufficiently strong models of a simple form. Two-stage hydrogen plants with a heavy piston and a high compression ratio use a powder charge as an energy source. The highest speed of 11.2 km / s in such installations was achieved for a disc-shaped body model with a diameter of about 5 mm.

The disadvantages of this device are the restrictions on the maximum throwing speed to 10-12 km / s, the limited choice of the shape and material of body models for throwing, the complexity of the design and the complexity of its operation. Existing hypersonic throwing devices have almost reached the limit of their capabilities.

Known we have chosen as a prototype, a method of obtaining a CSS plasma [Ed. Tyrsky A.G. Hypersonic aerodynamics and heat and mass transfer of descent spacecraft and planetary probes. M. Fizmatlit, 2011. 546 pp.], Including electromagnetic gas heating, gas acceleration and supersonic flow around a stationary model of a body. In this method of experimental production of a shock-compressed layer near the body, air at room temperature is supplied with constant flow through an annular nozzle to the discharge channel of an induction plasma torch (VSU-4 unit with a quartz cylindrical tube 400 mm long and 80 mm in diameter). Heated in the inductor by a high-frequency electric field, the flow of air plasma flows into the pressure chamber through a conical sound nozzle located at the end of the discharge channel. A model body located coaxially with a flowing underexpanded jet at a certain distance from the exit from the discharge channel, interacting with the flow of high enthalpy air coming from the discharge channel of the induction plasma torch, creates a shock-compressed layer of heated gas near the streamlined body surface with its subsequent registration using high-speed shadow photography.

However, this method of obtaining CSS with hypersonic flow around the body has significant disadvantages and limitations. It uses a limited range of gases (nitrogen, CO ₂ , air) as a working substance, requires preliminary preparation of large volumes of a working gas mixture, followed by its supply to a closed working volume using sophisticated gas mixing technology using certified equipment. In addition, the maximum free-stream velocity V _{∞ is} also limited and reaches a value of no more than 12 km / s.

To implement this method, gigantic powers are required to provide the corresponding kinetic energy of the flow when flowing around a stationary model of a body.

As a prototype of the device, we have chosen a pulsed wind tunnel (IT-2) of the Central Aerohydrodynamic Institute. NOT. Zhukovsky [Ed. Tyrsky A.G. Hypersonic aerodynamics and heat and mass transfer of descent spacecraft and planetary probes. - M. Fizmatlit, 2011. 546 pp.], Which is a multi-mode electric-discharge installation with a capacitor power supply with stored energy up to 550 kJ. High values of gas pressure and temperature in the discharge chamber, made in the form of a cylindrical pipe, are achieved by heating the working gas (nitrogen, CO ₂ ) with a pulsed electric discharge of high power. In this case, the calculated gas plasma flow in the working part of the installation is maintained up to 100 ms. The pipe is equipped with conical nozzles with a solution angle of 10 ⁰ . In various test modes, a pulsed wind tunnel allows to obtain working gas flows with Mach numbers up to 20 and Reynolds numbers Re _∞ in the range 10 ⁵ -10 ⁶ .

The described device, as well as the method, cannot be used to solve problems associated with obtaining a supersonic flow near the KO and high-temperature physical phenomena accompanying the motion of the KO (for example, meteoroids) with the speed of entry into the atmosphere V = 16-70 km / s. It does not meet the requirements of modern hypersonic aerodynamics and plasma dynamics, when it is planned to develop space systems and vehicles with orbital velocities of entry into the atmosphere of 16 km / s and more.

The claimed group of inventions allows us to obtain a shock-compressed plasma layer and the structure of flows near a model body of a given shape * (* By a given model of a model body we mean a body in the form of a cone, wedge, cylinder, a dull body with a half-angle for cone and wedge Θ, radius of curvature for a blunt body Ro, with a characteristic body length L _mt .) of high-speed, up to 50 km / s and above, flows of almost any chemical and ionization composition.

When conducting plasma-dynamic studies, we first showed that an important requirement for modeling flow regimes in high-altitude hypersonic aerodynamics for a wide range of Mach numbers (M _∞ = 1 ... 30) and Reynolds (Re _∞ ≥1) corresponds to the plasma flow generated by a jet diaphragm discharge ( see Fig. 1), namely: the structure of the perturbed region near the model body when plasma flows around the jet diaphragm discharge at the diaphragm-ring electrode gap has the properties of self-similar flows, i.e. with proportionality of geometric dimensions, the proportionality of the values (speed, pressure, density) that determine the flow of the plasma stream flowing around the model body is observed; the thermodynamic parameters in the vicinity of a model body of a given shape are similar for combinations of parameters (density ρ _∞ , velocity V _∞ , Mach number M _∞ and Reynolds number Re _∞ ) of the incident flow.

This technical effect is achieved by us when

- in the method of producing a shock-compressed plasma layer by the interaction of a high-enthalpy jet with a model body located coaxially with the jet with subsequent registration of the structure of the perturbed region near the model body, it is new that a high-enthalpy jet is formed during a jet diaphragm discharge in vacuum in a supersonic flow regime of erosive plasma jets under conditions of placement of a model body with a characteristic size P found from the relation

Ρ≤0.5 R, where

R is the radius of the hole in the ring electrode, cm;

on the gap, the plasma-forming diaphragm is a ring electrode (cathode and / or anode), at a velocity V _{∞ of the} incident plasma flow on the model body, on the gap a diaphragm is a ring electrode, found from the relation

, где

where

V _cr = 724i ^0.22 / (0.9r ₀ ) ^0.33 - flow velocity in the critical section, m / s;

P _o = (1 + γ) [0.14i ^1.34 (2l ₀ ) ^0.93 ] / [r _{o 2.95} (1 + r ₀ / 2l ₀ ) ^0.67 ] - pushing pressure in the middle of the opening of the diaphragm, Pa;

R _vak is the pressure in the vacuum chamber, Pa;

γ = c _p / c _v = 1.1-1.3 is the adiabatic constant taking into account the plasma ionization energy;

ω is the average rate of ablation of the mass of the plasma-forming material of the diaphragm, kg / s;

µµ _o = 1.257 10 ^-6 GN / m;

i is the discharge current, A;

r ₀ is the radius of the hole in the diaphragm, cm;

2l ₀ - aperture thickness, cm;

R is the radius of the hole in the ring electrode, cm;

at the velocity ω of the ablation of the mass Δm of the plasma-forming substance of the jet selected from the relation

ω = Δm / t _gas , kg / s, where

Δm = ml ₀ / V _kp t _imp - ablation of the mass during gas exchange in the diaphragm opening, kg;

m is the total mass of carried away products of erosion of the material from the hole in the diaphragm, kg;

2l ₀ - the thickness of the diaphragm, m;

t _imp - discharge pulse duration, s;

V _cr - flow rate in the critical section of the flow nozzle, m / s;

t _gas = l ₀ / V _cr - gas exchange time in the opening of the diaphragm, s;

and with the component composition of the plasma flow corresponding to the selected composition of the plasma-forming material of the inner wall of the feed nozzle in the diaphragm opening: chemical elements and stoichiometric coefficients of the initial formula of the substance, and the structure of the perturbed region of the CSS is recorded by optical methods for the magnitude of the shock wave departure of the CSS and spectral methods for the emission of CSS ;

- in the device for producing a shock-compressed plasma layer, including a sealed discharge chamber with an electric power source, a gas-vacuum system, a nozzle mounted on the axis of the chamber and a model body located behind the nozzle, it is new that it is additionally inserted between the annular rings introduced into the chamber and made electrodes a diaphragm made with two coaxial flow nozzles, at least one model body with a characteristic linear size P, found from the ratio

Ρ≤0.5 R, where

R is the radius of the hole in the ring electrode, cm;

placed on the gap of the diaphragm-ring electrode (cathode and / or anode) at a distance D ₁ from the diaphragm, found from the ratio

D ₁ ≥10r ₀ , where

r ₀ is the radius of the hole in the diaphragm, cm;

as a power source, a pulsed current generator of jet diaphragm discharge with a discharge current value i (t) providing a flow rate V _cr in the critical section of the nozzle selected from the relation

v _cr = 724i ^0.22 / (0.9r ₀ ) ^0.33 , m / s, where

i is the discharge current, A;

r ₀ is the radius of the aperture, cm;

pressure P _cr in the critical section of the nozzle, selected from the ratio

P _cr = [0.14i ^1.34 (2l ₀ ) ^0.93 ] / [r ₀ ^2.95 (l + r ₀ / 2l ₀ ) ^0.67 ], Pa, where

i is the discharge current, A;

r ₀ is the radius of the aperture, cm;

2l ₀ - aperture thickness, cm;

the diaphragm is made of a plasma-forming material of a given chemical and stoichiometric composition and satisfies the following conditions: the ratio of the hole sizes 2r ₀ and the thickness 2l _{0 of the} diaphragm is selected from the ratio

2r ₀ / 2l ₀ = 1.0-2.0.

If the process is carried out in gas-dynamic (GD) mode, then two model bodies are installed in the chamber in the cathode and anode parts, respectively, while the ratio of the hole sizes 2r ₀ and the thickness 2l _{0 of the} diaphragm is chosen to be 1.0, and the discharge current value i (t ) the pulse current generator satisfies the condition

i≤1,4 10 ³ r _about ² , kA, where

r ₀ is the radius of the aperture, cm (see p. 3 of the Formula).

Approaches to the formation of a jet diaphragm discharge are known, see, for example, [2, 3].

The value of the total ablation of mass m of the plasma-forming material can be determined by the known method by weighing the diaphragm before and after the control discharge with the selected parameters of the discharge gap [4, 5].

Approaches to determining the component composition of plasma flows are known, see, for example, [4].

Optical and spectral methods for detecting plasma flows are known, see, for example, [6–8].

In FIG. 1 shows a diagram of a jet diaphragm discharge, which shows a plasma-forming diaphragm 1, a ring anode 2, a ring cathode 3.

2r ₀ is the diameter of the aperture;

2R is the diameter of the annular anode and cathode;

- напряженность азимутального магнитного поля; $${\overline{H}}_{\varphi }$$

- azimuthal magnetic field strength;

- плазменные струи в разрядном промежутке; $$\overline{V}$$

- plasma jets in the discharge gap;

- ток разряда; $$\overline{i}$$

- discharge current;

- направление линий азимутального магнитного поля $${\overline{H}}_{\varphi }$$

собственного тока разряда;

- direction of the azimuthal magnetic field lines $${\overline{H}}_{\varphi }$$

own discharge current;

- направление истечения плазменных струй $$\overline{V}$$

в анодной и катодной частях разрядного промежутка;

- direction of plasma jets $$\overline{V}$$

in the anode and cathode parts of the discharge gap;

- направление тока разряда $$\overline{i}$$

.

- direction of discharge current $$\overline{i}$$

.

In FIG. Figure 2a shows the recorded perturbed region 5 of the shock-compressed layer near the model body 4 when a plasma jet flows around it with a Mach number (M _∞ ≈ 4) flowing from the aperture of the diaphragm 1 towards the ring cathode 3 along the оси axis, where

θ _c is the angle of inclination of the shock wave (shock wave);

θ is the half angle at the apex of the cone of the model body 4.

In FIG. Figure 2b presents a snapshot of the CSS spectrum of emission along the оси axis of the incident flow onto the surface of a model body in the form of a cone with a half-angle θ = 45 ° obtained in the plasma flow regime of a cathode jet with the parameters described in the specific embodiment example. Along the axis of the wavelength λ, the designations of the spectral lines of ions of chemical elements present in the oncoming flow and at the critical point of the perturbed region 5 are plotted.

In FIG. 3 shows a diagram of a device for implementing the proposed method, where the discharge vacuum chamber 6, power supply 11, gas-vacuum system 7, ring anode 2, ring cathode 3, plasma-forming diaphragm 1, model 4, switch 8, ignition device 9, synchronization circuit 10;

D ₁ - the distance along the axis from the diaphragm to the model of the body 4;

2l ₀ - aperture thickness;

L is the diaphragm-electrode gap;

2R is the diameter of the hole in the ring electrode;

2r ₀ is the diameter of the hole in the diaphragm;

L _k is the inductance of the circuit;

With _o - the capacity of the high-voltage energy storage;

R _k is the resistance of the circuit.

A device that implements the claimed group of inventions, works as follows.

To solve the problem of modeling CSS for a plasma near a model body using the proposed method, for example, for a known-type spacecraft and its chemical composition moving at a speed V in the standard Earth’s atmosphere at a height H, the initial data of the simulation problem are compiled: the incident velocity V _∞ on the model the body is taken equal to the velocity of the SC, the thermodynamic parameters of the USS plasma near the model body, made on a scale relative to the SC, are taken equal to the thermodynamic parameters of the SCS near the SC in the atmosphere D at height H. In accordance with the original data modeling composition selected plasma diaphragm material. To implement the specified thermodynamic parameters of the CSS plasma near the model body using a jet diaphragm discharge, the current density in the diaphragm hole and the parameters of the hole in the diaphragm (diameter of the cylindrical hole 2r ₀ and thickness 2l _{0 of the} diaphragm) are selected. Then they compose a system of equations of radiation magnetic gas dynamics, which takes into account the electromagnetic force acting on a unit plasma volume, ohmic heating, and energy transfer by radiation in the approximation of radiant heat conductivity. The system of equations includes Maxwell's equations, where, taking into account the induction current due to the motion of the plasma, Ohm's law is written instead of the Coulomb law. (The solutions of a similar system of equations underlying the theoretical study of the physics of high-current electric-discharge light sources are given in [9, 10]). Solving the system of equations magnetogasdynamics for a given speed mode jet diaphragm discharge obtained approximate expression by which through the current magnitude value i in the hole and sizes of the cylindrical hole (2r ₀ and 2l ₀₎ is calculated all the necessary parameters of the plasma in the aperture (density ρ _o, pressure P _o , temperature T ₀ , speed of sound A _o ) and in the incident plasma flow (electron concentration N _e , pressure Ρ, electron temperature T _e , speed of sound A).

Such an approach allows, over a wide range of changes in the parameters of the equation of state of the discharge plasma in the diaphragm aperture (temperature 20,000 K <T <100,000 K and pressure 5 MPa <P <100 MPa), with fairly high accuracy (of the order of 5-10%), thermodynamic and gas-dynamic calculations are carried out during development necessary devices based on a jet diaphragm discharge in vacuum with the implementation of a given plasma flow regime (incident plasma flow velocity V _∞ and Mach numbers M _∞ ).

Then carry out the electrical calculation of the parameters of the pulsed discharge power source. Calculation approaches are known [9]. To obtain a current pulse i of the discharge of a given duration t _imp , amplitude i _o and shape, based on the calculation results, the interelectrode gap 2L, the value of the charging voltage U _{o of the} capacitor bank with the capacity C _o , the inductance of the circuit L _k , the resistance of the circuit R _k and the load resistance R _heat

After that, in the vacuum chamber 6 between the ring electrodes 2 and 3 through the plasma-forming diaphragm 1 (see Fig. 3) of the selected dimensions, a jet diaphragm pulse discharge is formed. To do this, to the ignition device 9 using a standard synchronization circuit 10, a trigger signal is opened, opening the switch 8 (for example, an ignitron) of the power supply 11, which is a high-voltage energy storage device with a capacity of _about . Then a high voltage is applied to the electrodes 2 and 3 and the capacitor bank with a capacity of C _{o is} discharged at the load, the interelectrode gap (anode 2 - cathode 3).

As a result of this, high-enthalpy plasma flows are obtained, flowing from the diaphragm opening to the sides of the ring electrodes, formed during jet diaphragm discharge in vacuum in the calculated flow regime of erosive plasma jets over an interelectrode gap of 2L in length. In this case, the velocity of the incident plasma flow W _∞ to the model body at the gap between the diaphragm and the ring electrode corresponds to the required calculated value for solving the CSS simulation problem (see Section 1 of the Formula).

The component composition of the plasma flow, predetermined, corresponds to the composition of the plasma-forming material (chemical elements) of the inner wall of the flow nozzle in the diaphragm hole, which, in a specific formulation of the problem, can simulate the composition of the atmosphere and the destruction products of the material of the cosmic body.

At the final stage of the implementation of the proposed method, a perturbed region is visualized near the model body with registration of the structure and spectral composition of the CSS radiation along the axis of the incident stream of the diaphragm discharge based on the known high-speed methods for recording fast processes [6, 7] and subsequent processing of the obtained images, photo scans and spectra OSS.

Thus, the structure of the perturbed region near the model body is obtained with photographic recording of the USS shock wave departure parameters (distance Δ departure or angle θ _s to the velocity vector V _∞ ) in the plasma flow for Μ _∞ > 1, (see Fig. 2a).

Based on the results of recording the spectral composition of the CSS radiation along the axis of the SDR incident flow (see Fig. 2b), the known parameters of the incident plasma plasma near the critical point are determined by known spectral methods (for example, by the method of relative intensities of spectral lines and the method of broadening the Stark spectral line) CSS: temperature T _e and concentration N _{e of} electrons [8]. After obtaining experimental results from the USS emission spectra in the form of spatio-temporal distributions of temperature T _e and electron concentration N _e , additional calculations of the thermodynamic parameters of the plasma are performed, for example, based on the Sakha equilibrium plasma model (calculation methods are known, see, for example, [8, 9]): the density ρ _∞ , the ion temperature of the oncoming flow, as well as the pressure P _Uss , the density of the Russ and the braking temperature T _Uss immediately after the direct shock wave (shock wave) in the region STS.

The results of determining the values of the braking pressure _Pss and the braking temperature _Tss at the critical point of the incoming flow are compared with the full-scale values of temperature, density and pressure behind the direct shock wave in a standard atmosphere depending on the height and speed of the TO motion (see, for example, [11, 12]).

Examples of specific performance.

As a first example of execution of the claimed group of inventions, we describe a method and device for producing a shock-compressed layer of carbon-oxygen-hydrogen plasma and the structure of flows near a model body made in the form of a cone with a half-angle at an apex of 45 ° at an incident flow velocity V _∞ = 28 km / s

To obtain a given speed V _∞ according to the ratios given in the claims, the required current density in the aperture opening is 350-400 kA / cm ² (gas-dynamic regime of jet diaphragm discharge). With the selected size of the hole diameter in the diaphragm 2r ₀ = 0.4 cm, the required value of the discharge current was 45-50 kA.

In order to realize a critical current pulse with a current maximum i = 50 kA and a duration of the order of 400 μs, we performed an electrotechnical calculation of the high-current discharge circuit of the pulse current generator and selected a capacitor _bank with a capacity of C _0calc = 2.8 mF, a charge voltage of U _0calc = 5 kV, and a plasma-forming material with a velocity of ablation of mass ω≈70 g / s at a current density of about j _o = i / πr ₀ ≈400 kA / cm ² .

As the plasma-forming material of the diaphragm 1, see FIG. 3, a PTK textolite with a stoichiometric composition of C ₃₇ H ₄₇ O ₁₆ and a small amount of Mg, Ca, N impurities with a diameter of a cylindrical hole of 2r _about equal to 4.0 mm and a thickness of 2l ₀ = 4.0 mm was used.

Then, the parameters of the discharge circuit were determined L _k = 5.6 μG, R _k = 10 mOhm in the short circuit mode, and the charge voltage of the capacitor bank U _{o was} measured using a C196 kilovoltmeter.

Based on the approximating expressions for the selected values of the current i in the hole and the dimensions of the cylindrical hole (2r ₀ and 2l ₀ ), all the necessary plasma parameters in the diaphragm hole were calculated: density ρ _o = 6.7 · 10 ^-5 g / cm ³ , pressure P ₀ = 22.1 MPa, temperature T ₀ = 49300 K, speed of sound A _o = 13.7 km / s. In this case, the specific enthalpy on the axis in the diaphragm hole was Δh _o ≈696 kJ / g, and the specific conductivity on the axis in the diaphragm hole was η ₀ ≈301.4 Ohm ^-1 cm ^-1 .

The diameter of the hole in the 2R ring electrodes of graphite was 4.0 cm. The distance L from the diaphragm 1 to the ring anode 2 and the ring cathode 3 was 5.0 cm each, respectively, and the interelectrode gap 2L + 2l ₀ was 10.4 cm.

A model body made of PTK PCB with a stoichiometric composition C ₃₇ H ₄₇ O _{16 was} installed in the gap between the diaphragm-ring electrode at a distance of D ₁ = 2.0 cm from the diaphragm. The model body was made in the form of a cone with a half-solution angle θ = 45 ° and had a transverse dimension P = 0.8 cm and a length L _mt = 1.0 cm.

After conducting an electrical calculation of the parameters of the discharge circuit of the pulse current generator, the discharge was formed in a vacuum chamber 6 (see Fig. 3) with a volume of 70 l at a pressure P _vak = 1.0 Pa through an opening in the plasma-forming diaphragm 1 by applying voltage between the ring electrodes 2 and 3 from a capacitor bank 11 with a capacitance C ₀ = 2.8 mF and a charge voltage U ₀ = 5 ± 0.3 kV, (see Fig. 3).

When a discharge was formed on the interelectrode gap, a perturbed region was recorded near the model body: the CSS structure along the axis of the incident stream of a diaphragm jet using a VFU-1 high-speed photographic setup in high-speed shooting mode and a photo-chronograph mode, and the spectral composition of radiation using a SP-452 spectrograph and DFS-452 diffraction spectrograph [6, 7].

After the discharge was formed in the interelectrode gap, a current pulse of 395 μs duration with a current amplitude of 50 ± 2 kA was recorded on a storage oscilloscope, and the updated value of the PCB mass ablation rate was obtained equal to ω = 74 g / s for the selected composition by the weighing method and by the magnitude of the burnup (increase in diameter) diaphragm holes. In this case, the total mass m of carried away erosion products from the hole during the current pulse t _imp was m≈15 mg, and the ablation of the mass Δm during gas exchange in the diaphragm hole t _gas was Δm = ml ₀ / V _cr t _imp ≈ 11.4 μg.

To determine the experimental value of the velocity of the incident flow V _∞ on the model body at a time corresponding to, for example, the maximum of the discharge current, we used the well-known dependence, see, for example, [11], for the Mach number M _{∞ of the} stream flowing around the cone from the angle of inclination θ _s in front of the apex of the shock wave (shock wave), half of the angle θ at the apex of the cone and the adiabatic constant γ. The angle of inclination θ _c = 73.4 ° was determined from a photograph of the CSS with the cone near it, FIG. 2a. For the angle at the apex of the cone θ = 45 ° and the adiabatic constant γ = 1.25, the experimental value of the Mach number was M _∞ = 4.37. Then we determined the value of the experimental value of the free-stream velocity V _∞ = M _∞ A _∞ = 27.9 km / s, where A _∞ = 0.4 km / s is the speed of sound in the free-stream plasma, compared with the calculated V _∞ = 27.8 km / s according to the Formula, p. 1.

In FIG. Figure 2b presents a snapshot of the spectral composition of the study of CSS with the axis of the incident flow on the surface of a model body in the form of a cone with a half-solution angle θ = 45 ° obtained in the calculated regime of the plasma flow of the cathode jet.

After processing the spatial distribution of the radiation spectra in the oncoming flow and in the CSS, FIG. 2b, by the methods of quantitative spectroscopy [8] (by the method of relative intensities of the spectral lines of carbon ions of the same multiplicity of CII 283.76 nm and CII of 391.84 nm and by the Stark broadening of the lines of the hydrogen atom H _β 486.1 nm and the carbon ion CII 299.3 nm) values were obtained:

- the electron temperature T _e∞ = 17000 K and the electron concentration Ne _∞ = 9.0 × 10 ¹⁶ cm ^-3 in the incident flow;

- the electron temperature T _{e Uss} = 22000 K and the electron concentration N _{e Uss} = 2.0 × 10 ¹⁸ cm ^-3 in the critical region of the CSS of the plasma.

Based on these experimental data, using the Saha equilibrium plasma model [8], the density ρ _∞ , pressure P _∞ and sound velocity A _∞ in the incident plasma flow were calculated, as well as the values of the required thermodynamic values of the ion temperature T _{i ouss} , pressure Ρ _ouss and concentration ions N _{i USS of the} plasma of the USS near the critical point for the selected model body, see the table.

The given simulation example describes the equilibrium state of the plasma in the critical region of the CSS in the supersonic flow regime at M _∞ = 4.37 when the body moves in the atmosphere at an altitude of about 30 km at a speed of about 28 km / s.

As another example of execution of the claimed group of inventions, a shock-compressed layer of carbon-hydrogen-oxygen-nitrogen plasma was obtained using organoplastics (C ₇₃ H ₅ O ₁₂ N ₁₀ ) as the plasma-forming material and the flow structure around a blunt-shaped model body with a radius of curvature R ₀ = 0.4 cm and a characteristic body length L _mt = 1.0 cm at an incident flow velocity V _∞ = 28 km / s and its density ρ _∞ = 1.26 × 10 ^-6 g / cm ^-3 with the implementation of the calculated parameters plasma in the CSS (braking pressure P _USS = 13.4 × 10 ⁵ Pa; temperature T _USS = 23000 K and constant oh adiabat γ = 1.21).

Using the claimed group of inventions, a shock-compressed layer of carbon-fluorine plasma was also obtained, where, as a plasma-forming material, polytetrafluoroethylene (C ₂ F ₄ ) _n and a flow structure near a model body of a blunt shape with a radius of curvature R ₀ = 0.4 cm and the characteristic body length L _mt = 1.0 cm at an incident flow velocity V _∞ = 53.2 km / s with the implementation of plasma parameters in the CSS (braking pressure _Pss = 128.6 × 10 ⁵ Pa; braking temperatures T _uss = 37000 K , density ρ _усс = 2.39 × 10 ^-4 g / cm ^-3 and adiabatic constant γ = 1.23).

Thus, the results obtained make it possible to simulate phenomena during supersonic flow of bodies by high-speed plasma flows, and can be used to describe the structure and radiation of a shock-compressed layer similar to the flow during the motion of spacecraft, planetary probes, meteorites and other space objects (SC) in the atmosphere Earth at heights of 30-200 km and above, described in the literature (see, for example, [1, 12]), as well as in studying the thermophysical properties of materials used in space rocket technology.

Literature

1. Bronstein V.A. Physics of meteor phenomena. - M.: Science, 1981. 416 p.

2. Kalashnikov EV // TVT, 1996.V. 34, No. 4. S. 501-505.

3. Kalashnikov EV, Kostitsyna T.G. // TVT, 2000, T. 38, No. 2. S. 194-199.

4. Kalashnikov E.V., Kostitsyna T.G. // Opt. and spectrum. 1995.Vol. 78, No. 1. S. 60-64.

5. Abramovich G.N. Applied gas dynamics. M, Science. 1976. 888 p.

6. Dubovik A.S. Photographic registration of fast processes. M., Science. 1984.

7. Minko L.Ya. Production and research of pulsed plasma flows. Minsk. 1970.

8. Lochte-Holtgreven. Plasma research methods. M., World. 1971. 552 p.

9. Riser Yu.P. Physics of gas discharge. M., Science. 1987.592 s.

10. Alexandrov A.F., Rukhadze A.A. Physics of high-current electric-discharge light sources. M., Moscow State University. 1976.

11. Applied aerodynamics. Ed. N.F. Krasnova. M., High School. 1974. 135 p.

12. Nonequilibrium physico-chemical processes in aerodynamics. / Under the total. ed. G.I. Maykapara. M., Mechanical Engineering. 1972.344 s.

Claims (3)

1. A method for producing a shock-compressed plasma layer by interaction of a high-enthalpy jet with a model body located coaxially with the jet, followed by registration of the structure of the perturbed region near the model body, characterized in that a high-enthalpy jet is formed during a diaphragm jet discharge in vacuum in the flow of erosive plasma jets on the interelectrode gap under the conditions of placement of a model body with a characteristic size P found from the relation
P≤0.5R,
where R is the radius of the hole in the ring electrode, cm;
on the gap, the plasma-forming diaphragm is a ring electrode (cathode and / or anode), at a velocity V _{∞ of the} incident plasma flow on the model body, on the gap a diaphragm is a ring electrode, found from the relation

Where
V _cr = 724 i ^0.22 / (0.9r ₀ ) ^0.33 is the flow velocity in the critical section, m / s;

- pushing pressure in the center of the diaphragm opening, Pa;
P _vak is the pressure in the vacuum chamber, Pa;
γ = c _p / c _v = 1.2-1.3 - adiabatic constant taking into account the plasma ionization energy;
ω is the average rate of ablation of the mass of the plasma-forming material of the diaphragm, kg / s;
µµ _o = 1.257 10 ^-6 GN / m;
i is the discharge current, A;
r ₀ is the radius of the hole in the diaphragm, cm;
2l ₀ - aperture thickness, cm;
R is the radius of the hole in the ring electrode, cm;
at the velocity ω of the ablation of the mass Δm of the plasma-forming substance of the jet, it is selected from the relation
ω = Δm / t _gas , kg / s, where
Δm = ml ₀ / V _cr t _imp - weight loss during gas exchange in the diaphragm opening, kg;
m is the total mass of carried away products of erosion of the material from the hole in the diaphragm, kg;
2l ₀ - the thickness of the diaphragm, m;
t _imp - discharge pulse duration, s;
V _cr - flow rate in the critical section of the flow nozzle, m / s;
t _gas = l ₀ / V _cr - gas exchange time in the opening of the diaphragm, s;
and with the component composition of the plasma flow corresponding to the selected composition of the plasma-forming material of the inner wall of the flow nozzle in the diaphragm opening: chemical elements and stoichiometric coefficients of the initial formula of the substance, and the structure of the perturbed CSS region is recorded by optical methods according to the CSS shock wave and spectral methods for CSS emission; 2. A device for producing a shock-compressed plasma layer, comprising a sealed discharge chamber with an electric power source, a gas-vacuum system, a model body installed on the axis of the chamber and a model body located behind the nozzle, characterized in that it is additionally inserted between the ring electrodes introduced into the chamber and made a diaphragm made with two coaxial feed nozzles and at least one model body with a characteristic linear size P found from the relation
P≤0.5R,
where R is the radius of the hole in the ring electrode, cm;
placed on the gap of the diaphragm is an annular electrode (cathode and / or anode) at a distance D ₁ from the diaphragm, found from the ratio
D ₁ ≥10r ₀ , where
r ₀ is the radius of the hole in the diaphragm, cm;
as a power source, a pulsed current generator of jet diaphragm discharge with a discharge current value i (t) providing a flow rate V _cr in the critical section of the nozzle selected from the relation
V _cr = 724 i ^0.22 / (0.9r ₀ ) ^0.33 m / s, where
i is the discharge current, A;
r ₀ is the radius of the aperture, cm;
pressure P _cr in the critical section of the nozzle, selected from the ratio

Where
i is the discharge current, A;
r _{0 is the} radius of the aperture, cm;
2l ₀ - aperture thickness, cm;
the diaphragm is made of a plasma-forming material of a given composition and satisfies the following conditions: the ratio of the hole sizes 2r ₀ and the thickness 2l _{0 of the} diaphragm is selected from the ratio
2r ₀ / 2l ₀ = 1.0-2.0. 3. The device according to claim 2, characterized in that two model bodies are installed in the chamber in the cathode and anode parts, respectively, while the ratio of the hole sizes 2r ₀ and the thickness 2l _{0 of the} diaphragm is selected to be 1.0, and the discharge current value i ( t) the pulse current generator satisfies the condition
i≤1,4 · 10 ⁶ r ₀ ² , And, where
r ₀ is the radius of the aperture, see

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