RU51737U1 - GAS-DYNAMIC INSTALLATION - Google Patents

Abstract

The proposed utility model relates to the field of apparatus for studying the physical processes of generation of strong shock waves and thermal broadband radiation in finite pressure media. The purpose of developing a utility model is to build a system of hypersonic aerodynamics and radiation plasma dynamics to study the thermodynamic state of a gas in a medium flow having internal degrees of freedom up to a temperature of 50000K. Gas-dynamic installation (GU), including a Ludwig-type hypersonic wind tunnel (ADT), in which a cylinder with a high gas pressure is arranged in series, a prechamber — a long high-pressure channel, a Laval nozzle, a working part with mechanisms supporting the model, a diffuser and a vacuum cavity, three high-speed valves located after the high-pressure cylinder, in front of the prechamber, after the working part, blocks whose controls are connected to a digital computer (digital computer), free electron laser (FEL), including: a linear induction electron accelerator, an electron injector, an electromagnetic undulator, the control winding of which is connected to the FEL control unit and then to the digital computer, ion probes with a plasma flow parameter conversion unit, a holographic interferometer associated with a digital computer, high-speed film-making equipment, as part of the GU after the high-speed valve of the high-pressure cylinder, a closed tokamak-type magnetic trap is introduced, which includes the primary winding of the iron core and the toroidal magnetic coil I alignment liner electric field, a vacuum chamber, which via a transition pipe connection and quick-acting valve is connected to the prechamber ADT while using a waveguide - ictochnikom with plasma heating electromagnetic radiation coupled to a digital computer.

Description

The proposed utility model relates to the field of hypersonic aerodynamics and radiation plasma dynamics and is intended to study the physical processes of generation of strong shock waves and thermal broadband radiation in finite pressure media.

Known hypersonic wind tunnel (ADT) with a magneto-hydrodynamic (MHD) - Faraday accelerator (Byushgens GS, Sychev VV, Berdzhitsky EL, etc. "TsAGI - the main stages of scientific activity 1968-1993. ", M." Science ", 1996, p. 396). ADT contains a sequentially located electric arc heater that heats the gas to ≈2000K, a metering device, a primary supersonic nozzle, an MHD accelerator, a secondary nozzle, a working part, and ejectors.

However, this setup does not allow creating a model of the flow around bodies in an excited gas medium at ultrahigh temperatures - it does not take into account the property of real physical systems having internal degrees of freedom and determining resonance absorption frequencies.

NASA's conical electric arc chamber (JPL) shock tube is also known, where the energy for creating a shock wave is provided by a capacitive storage system consisting of 100 capacitors with an energy supply of 290 kJ at a voltage of 20,000 V. W. A. Menard. - A Higher Performance Electric-ARC-Driven Shook Tabe. JPL, Passadena California - AIAA Jornal, 1971, v. 9. N10. The velocities of shock waves reached values from 10 to 32 km / s, the temperature for air was 31000 K, and the time was 11 ms.

But higher temperatures when using an electric arc chamber for hypersonic research are not achieved.

The well-known "Gas-dynamic installation" (RU 46356 U, published on June 28, 2005), containing a hypersonic wind tunnel, in which are arranged in series: a high-pressure balloon, a Faraday MHD accelerator with control windings, a secondary nozzle, and a working one

part of the ADT with the investigated model and holder, an output nozzle, a multi-stage system of ejectors, pressure and temperature sensors connected through a converter to the first input of a computer, a free electron laser including a linear electron accelerator, electron injector, electromagnetic undulator, whose control coil is connected via a converter with a second computer input, and a third computer input through a converter connected to the control windings of the Faraday MHD accelerator, a spectrograph, and high-speed filming equipment.

However, in projects for the return of spacecraft (SC) to Earth, for example, in a project for the delivery of soil samples from Mars to Earth, the paths of entry into the Earth’s atmosphere at a speed of over 11 km / s are considered. Under these conditions, immediately after the front of the head shock wave near the apparatus, the gas temperature can reach values above 50,000K. At such temperatures, behind the shock wave, in place of the excitation of vibrational degrees of freedom of gas molecules and dissociation processes, which largely determine the thermodynamic parameters of the spacecraft flow around them at a flight speed of up to 8 km / s, the process of atomic ionization by electron impact occurs. At speeds above 10 km / s, atomic processes begin to dominate. In this case, the relationship between ionization and radiative processes begins to play a large role. (V. A. Gorelov, A. Yu. Kireev. Aerothermophysics of entry into the Earth’s atmosphere with superorbital velocity. Fundamental problems of high-speed currents. International scientific and technical conference. TsAGI. 2004.)

The purpose of developing a utility model is to build a system of hypersonic aerodynamics and radiation plasma dynamics to study the thermodynamic state of a gas in a medium flow having internal degrees of freedom up to a stagnation temperature of 50000K.

To solve this problem, a gasdynamic installation (GU), which includes a Ludwig-type hypersonic wind tunnel, in which a cylinder with a high gas pressure is arranged sequentially, a prechamber — a long high-pressure channel, a Laval nozzle, and a working part with

supporting mechanisms, a diffuser and a vacuum cavity, three quick-acting valves located after the high-pressure cylinder, in front of the prechamber, after the working part, the blocks whose controls are connected to a digital computer (digital computer), a free electron laser (FEL), including linear induction electron accelerator, electron injector, electromagnetic undulator, the control winding of which is connected to the FEL control unit and then to the digital computer, ion probes with a unit for converting plasma flow parameters, a holographic interferometer associated with a digital computer, high-speed filming equipment, a closed magnetic trap of the tokamak type, including a primary winding of an iron core, a toroidal magnetic field coil, an electric field alignment liner, a vacuum chamber, which a transition pipe and a high-speed valve connected to the ATD prechamber using a waveguide — to a source of electromagnetic radiation from a plasma heating connected to Digital computer

To clarify the essence of the utility model, figure 1 shows a functional diagram of a gas-dynamic installation, which shows:

1 - primary winding of the transformer;

2 - coils of a toroidal magnetic field;

3 - a vacuum chamber;

4 - a magnetic field coil;

5 - liner - thin-walled chamber for aligning the toroidal magnetic field;

6 - iron core (transformer magnetic circuit);

7 - connecting pipe;

8, 17, 34 - high-speed valve;

9 - prechamber (tube of long l) of the wind tunnel;

10 - Laval nozzle;

11 - ion probes - electric probes of ionized flow;

12 - tunable frequency laser;

13 - the working part of the wind tunnel;

14 - equipment for high-speed filming;

15 - the investigated model of the aircraft;

16 - model holder;

18 - diffuser;

19 - a vacuum cavity;

20, 32, 33 - control units for high-speed valves 17, 34;

21 - free electron laser (FEL);

22 - linear induction accelerator;

23 - cores of inductors;

24 - single-turn exciting windings;

25 - coils;

26 - electromagnetic undulator;

27 - electron injector;

28 - control unit FEL;

29 - holographic interferometer;

30 - digital electronic computer (digital computer);

31 - a converter of plasma flow parameters;

35 - cylinder with a high gas pressure;

36 - source of electromagnetic radiation with a waveguide.

Figure 2 shows the auxiliary device is a holographic interferometer, where are sequentially located:

37 - a glass window in the wall of the pipe;

38 - a cuvette with nitrobenzene;

39 - KDP crystal of potassium phosphate KH ₂ PO ₄ ;

40 - translucent mirror (reflector);

41 - the first photographic recorder;

42 - second photographic recorder;

43 - lens;

44 is a mirror.

The control unit includes a Ludwig-type hypersonic ADT, where a cylinder with a high gas pressure (35) is located in series, a prechamber (9) —a long channel of high pressure of long l, a Laval nozzle (10), a working part with mechanisms supporting the model (13), a diffuser (18 ), the vacuum cavity (19). Three quick-acting valves (34, 8, 17) located after the high-pressure cylinder (35), before the prechamber (9), after the working part (13), control units (33, 32, 20) of the quick-acting valves are connected to the digital computer (30). A free electron laser (21) includes: a linear induction electron accelerator (22), an electron injector (27), an electromagnetic undulator (26), the control winding of which is connected to the FEL control unit (28) and then connected to a digital computer (30). Ion probes (11) are connected to a digital computer (30) through a plasma flow parameter conversion unit (31) and a holographic interferometer (12, 29). High-speed filming equipment (14) captures rapidly occurring processes in the GU. After the high-speed valve (34) of the high-pressure cylinder (35), a closed tokamak-type magnetic trap is located, including the primary winding (1) of the iron core (magnetic circuit) (6), the toroidal magnetic field coil (2), the electric field alignment liner (5), a vacuum chamber (3), which is connected to the ADT prechamber (9) through a transition connecting pipe (7) and a quick-acting valve (8). In addition, the vacuum chamber (3) is connected via a waveguide to a source (36) of electromagnetic radiation from a plasma heating connected to a digital computer (30).

PG works as follows.

To obtain high values of the plasma flow parameters in the prechamber 9, the gas is heated in a closed tokamak-type magnetic trap.

Tokamak - a toroidal chamber with magnetic coils - a device for holding high-temperature plasma using a strong magnetic field. Plasma is created in a toroidal vacuum chamber (3), which serves as the only closed loop of the secondary winding of the transformer (6). When passing current increasing in time in the primary winding (1)

transformer inside the chamber (5) creates a whirlwind longitudinal electric field. At a low initial gas density, an electrical breakdown occurs and the chamber (3) is filled with plasma, followed by an increase in a large longitudinal current I _p . It creates its own poloidal (in the plane of the plasma cross section) magnetic field B _θ . To stabilize the plasma, a strong magnetic field B _{φ is used} , created using the windings (2) of the toroidal magnetic field. It is a combination of toroidal and poloidal magnetic fields that ensures the stable confinement of high-temperature plasma. The tokamak plasma is heated by the Joule heat from the current flowing through it. Isolation of it is sufficient for high temperatures. The tokamak is complemented by a plasma heating system. For this, resonance-type high-frequency heating equipment is used, the resonances of which correspond to internal oscillatory processes in the plasma. The ion component is heated in the range of harmonics of the cyclotron frequencies of plasma ions; the electrons are heated at electron-cyclotron resonance from the radiation source (36) using microwave antennas and coaxial electrodes. Initially, a plasma in a plasma chamber is created by the injection of ions or electrons or beams of neutral atoms — preliminary heating of the gas by current. In the chamber, the pressure of the working gas is maintained (not lower than atmospheric). The possibility of heating the plasma to high temperatures is due to the fact that in a strong magnetic field the particle paths look like spirals wound around the magnetic field line. Therefore, electrons and ions are retained for a long time inside the plasma. And only due to collisions and fluctuations of the electric and magnetic fields, energy is released in the form of a heat flux. The effectiveness of magnetic thermal insulation is characterized by the energy lifetime necessary to maintain it in a stationary state. The plasma from the tokamak (1, 2, 3, 4, 5, 6) through the inlet system - the connecting pipe (7) and the high-speed valve (8) enters the ADT.

Simulation of hypersonic flight requires the reproduction in braking pressures of braking pressures from fractions to hundreds of MPA and braking temperatures of up to 30000-50000K. At hypersonic numbers M, the loss of total pressure during flow inhibition and, accordingly, the required pressure drops in the pressure transducer increase rapidly. At numbers M> 4.5, the air in the ADT must be heated to prevent its condensation. The region of intense condensation in the gas stream is characterized by a jump in condensation (SC). The gas-dynamic manifestation of SC depends on the rate of expansion of the flow and the thermophysical parameters of the medium. In a hypersonic flow of a single-component gas, SC manifests itself in a change in the pressure, density, and velocity gradients. In a hypersonic ADT with hypersonic flows, the condensation of the main components of the air is eliminated by heating the working gas.

In the pulsed-type ADT - Ludwig shock tube (TL), models of aircraft are tested at high Reynolds numbers (up to 10 ⁹ ) in a wide range of speed numbers M, up to M = 30. TL is actuated by opening valves 33, 8, 17. The flow pattern in the working part (13) remains almost unchanged for the period of time during which the rarefaction waves propagating along the prechamber (9) reach the end wall and are reflected from it and return to the nozzle. The duration τ of the stationary (working) flow is mainly determined by the channel length l and the speed of sound a in the gas with which the channel is filled . Stationary operation time is calculated in several tens (up to 10 ^-5 ) fractions of ms. A rarefaction wave is the propagation of an infinitesimal finite pressure perturbation Δp≤0 in a stationary or moving medium. If there is a continuous sequence of infinitesimal perturbations, then each subsequent perturbation propagates in the medium at a lower speed due to lower temperatures and gradually lags behind the previous one, the initial steep wave front becomes more gentle.

Low molecular weight and high pressure gas

accelerates in a rarefaction wave, compressing and heating gas in a shock wave. Two regions with quasistationary parameters are formed one after another. The test time is determined by the duration of the working gas through the working part of the TL. It is compressed in the shock waves falling and reflected from the nozzle. The initial gas parameters in the prechamber (9) are chosen so as to eliminate the appearance of secondary waves when the reflected shock jump is crossed.

The quasistationary regime of energy supply of radiation to a supersonic flow is realized using a laser (21). External energy supply is effective in determining the drag coefficients of the geometry of the bodies With _Y , stabilization of the boundary layer, intensification of combustion in a hypersonic flow, "thermal correction" is carried out - by creating heated areas to control flows. A study of the resonance properties of the processes of interaction of ADT flows and energy supply to the aircraft model is realized by changing the speed of the plasma frequency of free-electron laser radiation (21). This is done using a digital computer (30), which are connected to the FEL (21) through the control unit (28). In a computer (30), the correspondence between the plasma flow rates and the laser radiation frequency is determined in accordance with the signals of the sensors of the parameters of the ion probe flux (11) entering through the plasma flow transducers (31). Laser (FEL) (21) includes a linear accelerator (22), an electron injector (27), and an electromagnetic undulator (26).

In an accelerator, an increase in the energy of charged particles occurs under the influence of external longitudinal (directed along the velocity of the accelerated particles) electric fields. The accelerator includes a source (27) of accelerated particles, an electric or electromagnetic accelerating field generator, a vacuum chamber in which particles move during acceleration, an inlet-injection and beam ejection device from the accelerator, and a focusing device that provides a long-term device for

correction of the position of the configuration of accelerated beams.

In a linear induction accelerator (22), particle acceleration occurs in instantaneous electric fields with a change in magnetic induction. In a linear induction accelerator (22), electric field lines (with intensity E) are directed along the axis of the accelerator. An electric field is induced by a time-varying magnetic flux passing through successive ring ferrite inductors (23). The magnetic flux is excited in them by short current pulses transmitted through single-turn windings (24), covering the inductors. Focusing is performed by a longitudinal magnetic field, which is created by coils (25) located inside the inductors.

The processes occurring in extremely strong light fields are of the quasi-resonant type, and the polarization properties of the scattered radiation are anomalous. Atomic nuclei manifest themselves in the process of interaction with light beams of intensity 10 ²⁰ W / cm ² or more. In the process, the appearance of Raman scattering of visible radiation at transitions between the states of a compound nucleus is possible. The effects of the interaction of superstrong optical fields are manifested against the background of the effects of quasistationary light scattering: plasma electrons and ions with populated excited states are always present in a strongly excited gaseous medium. In ADT, at braking temperatures T ₀ ≥2000 K, the gas in these tubes glows intensively both in the flow incident on the model and behind the shock wave in front of the model.

An electric probe (31), as a means of diagnosing plasma formations, makes it possible to determine local values of the electron concentration and temperature at a given point of the ionized stream with a resolution determined by the size of the probe’s sensitive element. The measured local values find the distribution of electron concentration and temperature over the thickness of the shock layer.

The probe method consists in measuring the current strength of charged particles on an electrode having some potential relative to the plasma. Dependence

current strength from the electrode potential determines the probe characteristic. The probe characteristics determine the main plasma parameters - the temperature and concentration of charged particles, as well as the plasma potential, which is determined by measuring equipment. Structurally, the electric probes (31) are made in the form of separate sensors or combs for measuring the ion concentration profile. To measure electron concentration or electron concentration gradients in a layer directly adjacent to the surface of an aircraft model, flat or projecting probes are used.

To visualize gas-dynamic flows, optical visualization methods based on the phenomenon of light deflection when passing through inhomogeneities of a dense transparent medium and interferometry for quantitative studies of the density of a transparent medium are used. When interferometric registration of the flow field, the pattern of the distribution of light intensity bands reflects the spatial distribution of the refractive index of the medium.

The increase in information content in the diagnosis of multicomponent plasma is carried out using polychromatic holography. Plasma sounding is carried out by three wavelengths: the fundamental frequency and harmonics of a ruby laser (12) (694.3 and 347.2 Nm) and stimulated Raman scattering (SRS) of the ruby laser radiation in nitrobenzene (765.8 Nm). The laser beam (12) hits the aircraft model (15) after it passes through a cell with nitrobenzene (38) and a KDR crystal (KH ₂ PO ₄ - potassium phosphate), resulting in the formation of a light beam containing radiation with three types waves. The three-wavelength light beam passes the light delay line (44), which leads not only to the necessary time shift relative to the moment of the appearance of the laser torch of the aircraft model (15), but also to an improvement in the spatial coherence of the Raman radiation. A translucent mirror (40) is used to separate the light beam into an object beam passing through a laser torch and a reference one. Two holographies are simultaneously recorded: one (41) in the light

the fundamental frequency and harmonics of a ruby laser (12), the other (42) in the light of stimulated Raman scattering. Three-holographic holographic interference (HI) is carried out simultaneously for three plasma components, a laser plume of the electron model, working gas molecules and metal atoms of the model.

Using GI, interfetometric patterns formed by waves are obtained and interpreted, of which one is recorded and reconstructed holographically. The interaction of the reconstructing wave with the structure recorded on the hologram leads to the restoration of the object wave. If the reconstructing wave is an exact copy of the reference wave, then the phase and amplitude structures of the object wave are precisely restored. If we illuminate the hologram by removing the object, we will see its image in the same place and in the same state in which it was while recording the hologram.

Phase objects (shock waves in gases and plasma) are studied by transmission through their object beam. GI allows one to obtain the spatial distribution of the refractive index, which, in turn, is uniquely associated with the spatial distribution of the concentration of atoms, molecules and electrons. Since the hologram captures not only phase, but also amplitude distortions introduced by the plasma, the plasma absorption coefficient is determined from this. Information in the GI method about the phase properties of an object is extracted from the bending of interference fringes. The measured value in this case is the phase difference of the interfering waves normalized to the period — the shift of the bands, the relationship between the shift of the bands and the refractive indices of the plasma.

The position of the front of the shock wave in front of the model using shadow high-speed shooting (GI) using a laser as a light source (12) can reduce the effect on the visualization result of the intrinsic flux from the zone in front of the shock wave front. In the region behind the shock wave, when the blunt bodies flow around, the temperature and density of the gas sharply increase, forming a powerful radiation source that provides additional resonant excitation of atoms and molecules upstream beyond the shock front.

Claims (1)

Gas-dynamic installation (GU), including a hypersonic wind tunnel (ADT), in which a high-pressure gas cylinder is arranged in series, a prechamber — a long high-pressure channel, a Laval nozzle, a working part with supporting mechanisms, a diffuser and a vacuum cavity, three quick-acting valves, located after the high-pressure cylinder, in front of the prechamber, after the working part, the blocks whose controls are connected to a digital computer (digital computer), a free electron laser (FEL), including a frost induction electron accelerator, electron injector, electromagnetic undulator, the control winding of which is connected to the FEL control unit and then to the digital computer, ion probes with a plasma flow parameter conversion unit, topographic interferometer connected to the digital computer, high-speed film-making equipment, characterized in that its composition after the high-speed valve of the high-pressure cylinder was introduced a closed magnetic trap of the tokamak type, including the primary winding of the iron core, toroidal magnesium coils field, an electric field leveling liner, a vacuum chamber, which is connected to the ADT prechamber through a transitional connecting pipe and a quick-acting valve, and with the help of a waveguide, to a source of electromagnetic radiation from a plasma heating connected to a digital computer.