RU46356U1 - GAS-DYNAMIC INSTALLATION - Google Patents

Abstract

Gas-dynamic installation containing a hypersonic wind tunnel (ADT), in which a high-pressure balloon, a control throttle, an electric arc heater, a dosing device, a primary supersonic nozzle, a magneto-hydrodynamic (MHD) Faraday accelerator with control windings, a secondary nozzle, and a working part are arranged in series ADT with the investigated model and holder, output nozzle, multi-stage system of ejectors, pressure and temperature sensors connected via input to converter m computer, high-speed filming equipment, spectrograph, and its composition includes a free electron laser containing a linear induction electron accelerator, electron injector, electromagnetic undulator, the control coil of which is connected through the converter to the first output of the computer, and the second output is connected to the control via the converter windings of the MHD accelerator Faraday

Description

The 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.

The large-sized hypersonic wind tunnel (ATD) T-117 is known (G.S.Byushgens, E.P. Berzhitsky, TsAGI - Center for Aviation Science, M. "Science", 1993), which allows the study of aerodynamic and thermal characteristics of models of various hypersonic flying devices (LA) with a fairly complete geometric similarity of models and nature. The aerodynamic circuit of the T-117 pipe contains an electric arc heater, the working part is a circle with a diameter of d = 1 m, a heat exchanger, a vacuum tank, shut-off valves, ejectors, a supersonic nozzle, and a supersonic diffuser.

The hypersonic pipe T-117 is a batch pipe using high-pressure compressed air (up to 320 atm.), Accumulated in cylinders with a capacity of 10 m ³ each. The necessary compression ratio in the pipe is created on the one hand by high braking pressure in the tube chamber (from 40 to 280 atm.) And, on the other hand, by using a four-stage stage of ejectors or a vacuum tank with a volume of 3000 m ³ with an initial vacuum of up to 0.01 mm Hg. creating the necessary vacuum behind one of the three unregulated supersonic diffusers.

The duration of one test when working with the ejector system is up to 3 minutes, with a vacuum capacity of 1.5 minutes.

The pipe has a set of profiled axisymmetric, supersonic nozzles with an output diameter of 1.0 m, designed to be implemented by the number M at the nozzle exit in the range from 10 to 20. The range of Re numbers is from 0.15 · 10 ⁶ to 4.8 · 10 ⁶ ( assigned to 1 m).

To prevent air condensation in the working part when it is accelerated to the given supersonic speeds, the working gas is pre-heated to a temperature in the prechamber of 1200-2000 K using an electric arc heater with a capacity of 25000 kW.

The working part of the pipe is made according to the scheme of the Eiffel chamber with cooled walls and is equipped with two high-speed mechanisms for introducing the tested model into the stream.

The pipe is equipped with a high-speed measuring and information complex consisting of: strain gauge scales for various cases of model loading, pressure and temperature sensors, optical flow visualization tools, computer systems. The experiment process is automated. The output is given in the form of tables and graphs. The following types of experiments can be carried out in a T-117 hypersonic wind tunnel:

- determination of the total aerodynamic characteristics of aircraft models and their elements;

- determination of the distribution of pressure and heat fluxes on the surface of the models;

- visualization of the flow pattern using a shear interferometer;

- physical research.

However, the composition and capabilities of this experimental base do not reflect the characteristics of the hypersonic range of flight speeds: a variety of physical effects and the impossibility of field modeling in ground conditions of all the necessary characteristics, taking into account the resonant energy absorption of the blunt end of the model.

Known ADT with magnetohydrodynamic (MHD) - Faraday accelerators (see Bryusgen G.S., Sychev V.V., Berdzhitsky E.L. et al. TsAGI - the main stages of scientific activity 1968-1993, p. 396 ) taken as a prototype. ADT contains a sequentially located electric arc heater, a metering device, a primary supersonic nozzle, an MHD accelerator, a secondary nozzle, a working part, and ejectors. In a hypersonic ADT, the pressure distribution over the surface of the models, the magnitude of the deviation and the shape of the shock wave, the parameters in the prechamber of the setup p ₀ and T ₀ of the total and static pressures in the flow at the location of the models, the braking enthalpy, and the degree of possible deviation from the thermodynamic equilibrium of the gas state at exit from the nozzle.

The intrinsic luminescence of the gas is fixed through interference filters. To determine the position of the shock wave under conditions of strong intrinsic luminescence of the gas, a shadow installation is used, based on the use of the anomalous dispersion effect.

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

The purpose of developing a useful model is to build a system of hypersonic aerodynamics and radiation plasma dynamics to study the thermodynamic state of a gas in a stream, a medium with internal degrees of freedom, and to study the pattern flow around models taking into account the resonant properties of the system.

To solve this problem, in a gas-dynamic installation, including a hypersonic wind tunnel (ADT), in which a high-pressure balloon is located, a throttle, an electric arc heater, a metering device, a primary supersonic nozzle, a magneto-hydrodynamic (MHD) Faraday accelerator with control windings are sequentially located , secondary nozzle, ADT working part with the investigated model and holder, output nozzle, multistage system of ejectors, pressure and temperature sensors connected the first computer input, high-speed filming equipment, spectrograph, a free-electron laser is introduced into it, including a linear induction electron accelerator, electron injector, electromagnetic undulator, the control coil of which is connected through the converter to the second input of the computer, and the third input of the computer through the converter is connected to control windings of the Faraday MHD accelerator.

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

1 - cylinder with high pressure;

2 - regulating throttle;

3 - electric arc heater;

4 - dosing device;

5 - primary supersonic nozzle;

6 - magneto-hydrodynamic MHD accelerator Faraday;

7 - secondary nozzle;

8 - tunable frequency laser;

9 - the working part of the wind tunnel;

10 - holder;

11 - model;

12 - nozzle;

13 - multi-stage system of ejectors;

14 - equipment for high-speed filming;

15 - spectrograph;

16 - temperature and pressure sensors;

17 - unit changes the electromagnetic fields (frequency) of the undulator;

18 - transducers of temperature and pressure of the stream;

19 - block changes in electromagnetic fields;

20 - computers;

21 - free electron laser;

22 - linear electron accelerator;

23 - inductor core;

24 - exciting windings;

25 - focusing coils;

26 - undulator;

27 - electron injector.

The gas-dynamic installation (GU) includes a hypersonic wind tunnel (ADT), in which a cylinder (1) with a high air pressure, a regulating throttle (2), an electric arc heater (3), a metering device (4), a primary supersonic nozzle (5) are sequentially located , a Faraday magneto-hydrodynamic accelerator (6) with control windings, a secondary nozzle (7), an ADT working part (9) with the model under study (11) and a holder (10), an output nozzle (12), a multi-stage ejector system (13), pressure and temperature sensors (16) that connect They are transmitted through converters with the first computer input (20).

As part of the ADT, equipment (14) for high-speed filming and a spectrograph (15) were installed. The structure of the GU includes a free-electron laser (21), which includes a linear induction accelerator with an electron injector (27), an electromagnetic undulator (26), the control coil of which is connected through an electromagnetic field converter - a frequency change unit (17) - to the second computer input (20); the third input of the computer (20) is connected via an electromagnetic field converter (19) to the control windings of the MHD accelerator (6).

Gas-dynamic installation operates as follows. Simulation of hypersonic flight requires reproduction of braking pressures from fractions of up to hundreds of MPA and braking temperatures of up to 10 ⁴ K. In the case of hypersonic Mach numbers, the total pressure loss during flow braking and the corresponding pressure drops in the motor transformer are intensively increased. At numbers M> 4.5, the air in the ADT must be heated to prevent its condensation. So, at M = 10, heat up to 10 ³ K, at M = 20, up to (2.5-2.8) · 10 ³ K. The maximum pressure in an air heater with an arc heater (3) is 18-20 MPa, which allows modeling hypersonic flight

devices (LA) only at low altitudes. The large pressure drop required for hypersonic ADTs is provided by a system of ejectors (13).

The region of intense condensation (gas-liquid phase transition) arising in an accelerating gas flow, the parameters of the thermodynamic state of which passed through the phase equilibrium curve, is characterized by a condensation jump (SC). SC is a consequence of the delay of condensation due to the insufficient number of condensation centers in the gas volume; therefore, ADT is equipped with a unit for air drying. In a hypersonic ADT with hypersonic flows, condensation of the main air components is eliminated by installing a working gas heater (3). 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.

With significant fluctuations in the current and discharge voltage in the heater associated with the instability of its conductive channel (3), a low quality of the heated flow is ensured. Therefore, the principle of discharge stabilization becomes a fundamental point. This ensures uniformity of movement of the conductive channel in the annular gap, certainty of the shape of the discharge and its position in the axial direction. In this case, an external magnetic field with a special topology is used to stabilize the discharge. The effect is provided by electromagnetic forces, the effect of which extends to each element of the discharge plasma.

In the conductive channel in the gap between the coaxial electrodes in an external axisymmetric magnetic field, the radial component of the magnetic induction changes along the axis of the electrodes. Under the action of the axial component of magnetic induction (Bx), the discharge channel between the electrodes will rotate between the electrodes relative to the longitudinal axis. But the interaction of the discharge with Bx cannot lead to the appearance of axial forces acting on it. Therefore, from the point of view of stabilization of the position of the discharge, Bx must be associated with the radial component of the magnetic induction Br.

A free electron laser (21) includes a linear accelerator (22), an electron injector (27), and an electromagnetic undulator (26).

In a linear induction accelerator (22), particle acceleration occurs in electric fields arising from 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 (tens or hundreds of NS) 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. A linear induction accelerator makes it possible to obtain kiloampere currents in a pulse at a current of 10 kA, and a side pulse duration of 50 NS.

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, a focusing device; providing a durable device for position correction; accelerated beam configurations. The effect of local energy supply on the structure of a supersonic flow and the flow regimes of models substantially changes

gas-dynamic structure of flows and supersonic flow regimes depending on the power, size and location of the energy release region in front of the streamlined body. The conditions and modes of energy release in a given region of the flow are carried out in a gas-dynamic setup using radiation energy (22). A laser remote method of introducing energy into a supersonic flow is used. The propagation of intense laser beams in the absorbed gas stream leads to the formation of heated local regions. The environmental parameters in the field of effective radiation absorption depend on the spectral region, the operating modes (pulsed, continuous) of the radiation source, as well as the method of supplying (thin extended beam, short or long focusing) energy. When threshold values of radiation intensity are exceeded, an optical breakdown occurs with the formation of a localized plasma in the gas stream. The properties of heated regions and plasma affect, in turn, the propagation and absorption of radiation and the dynamics of the formation of the energy source of the aircraft model. Dissipative processes lead to cooling (recombination) of the plasma and destruction of the plasma energy source some time after the energy pulse is introduced into the stream.

The main laws and interrelations of gas-dynamic processes and radiation energy absorption mechanisms that determine the thermal self-action of a laser beam in a stream, “light burning”, the formation of a high-speed laser spark — a laser wave of detonation of the propagation of optical discharges. In hypersonic gas flows, depending on the focusing conditions and when the radiation intensity is above the breakdown threshold, a localized laser plasma can form only in pulsed modes of a laser spark or light-detonation wave. During “sharp” focusing with a significant length of the breakdown plasma, a light-detonation wave propagating with hypersonic speed is formed, behind which a radiation absorption occurs in a narrow zone.

However, when the radiation intensity decreases or there are reasons that sharply decrease it near the focusing region, a light-detonation wave is not formed. In this case, the dynamics of the laser plasma corresponds to the regime of the laser spark, in which the change in parameters is determined by the radial size of the plasma. In the case of a short laser pulse duration, the condition of “instantaneous” energy release is fulfilled. Therefore, for a spherical and cylindrical laser spark, the gas-dynamic structure corresponds to the model of point explosion.

The quasistationary regime of energy supply of radiation to a supersonic flow is realized by using laser radiation (21). External energy supply is effective in determining the drag coefficients of the geometry of bodies C _x , stabilization of the boundary layer, intensification of combustion in a hypersonic flow, etc., “thermal correction” is carried out - by creating heated areas for controlling flows. The investigation of the resonance properties of the processes of the interaction of ADT flows and energy supply to the aircraft model is carried out by changing the speed of the plasma frequency of the free-electron laser radiation (21) This is done using a computer (20), which uses frequency converters (17) and (19) through the converters electromagnetic fields is connected to the windings of the MHD accelerator (6) and the windings of the undulator (26) of a free electron laser. In a computer (20), the correspondence of the plasma flow rates and the laser radiation frequency is determined in accordance with the signals of the flow parameters sensors (16), coming through the transducers (18).

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 quasi-stationary light scattering: plasma electrons and ions with populated excited states are always present in a highly excited gas medium.

In ADTs with electric arc gas heaters at braking temperatures T ₀ ≥200 K, the gas in these pipes glows intensively both in the stream running onto the model and behind the shock wave in front of the model.

To visualize gas-dynamic flows, optical visualization methods are used, based on the phenomenon of light deflection when it passes through inhomogeneities of a dense transparent medium and interferometry for quantitative studies of the density of a transparent medium. With hitherferometric 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 interference pattern is a system of bands, the distance between the maxima of which at a given wavelength is determined by the angle of convergence of the interference waves. The GU used the interference method of anomalous dispersion — Kryukov-Rozhdestvensky, where “crossed” spectral devices — a Jamen interferometer and a spectrograph — were installed. For a spectrometer (15) with crossed prisms near the absorption bands of a substance, a decrease in the refractive index as a function of frequency is observed. In the interaction of high-power radiation with matter, the basic assumption of the theory of dispersion on the proportionality of polarization to the acting field is violated; an addition to the refractive index arises, proportional to the light intensity, leading to the self-action of light pulses and beams. Saturation of absorption is observed.

Gas dynamic methods are used to measure the flow velocity in an ADT. Using a device for direct speed measurement based on the Doppler effect. For this, resonant lines of atoms are excited in a stream using a tunable laser (8) using an interferometer.

A heat flow sensor (16) based on high-frequency single-crystal bismuth is used. The principle of the sensor is based on the transverse Seebeck effect. The output signal (thermoEMF) is linearly connected with the heat flux in the surface layer of bismuth, and the electric field vector is normal to the incident heat flux vector.

To determine the nature of the gas glow in an unperturbed flow, spectroscopic studies are carried out in front of the model using a spectrograph (15) The spectrum of gas emission from the zone behind the shock wave in front of the model differs from the spectrum of the unperturbed flow only in intensity, but not in composition.

The position of the front of the shock wave in front of the model using shadow shooting using a laser as a light source allows you to reduce the effect on the visualization result of the own glow of the stream from the zone in front of the shock wave front. In the region behind the shock wave, as the flow around blunt bodies increases, the temperature and density of the gas increase sharply, and a powerful radiation source is formed, which provides additional resonance excitation of non-atoms and molecules upstream beyond the shock front.

Claims (1)

Gas-dynamic installation containing a hypersonic wind tunnel (ADT), in which a high-pressure balloon, a control throttle, an electric arc heater, a dosing device, a primary supersonic nozzle, a magneto-hydrodynamic (MHD) Faraday accelerator with control windings, a secondary nozzle, and a working part are arranged in series ADT with the investigated model and holder, output nozzle, multi-stage system of ejectors, pressure and temperature sensors connected via input to converter m computer, high-speed filming equipment, spectrograph, characterized in that it includes a free electron laser containing a linear induction electron accelerator, electron injector, electromagnetic undulator, the control coil of which is connected via a converter to the first output of the computer, and the second output of the computer through the converter is connected to the control windings of the Faraday MHD accelerator.