RU2666746C1 - Device for achieving supersonic speeds - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to plasma engineering. Device based on the railgun is made in the form of a coaxial line CL, where the discharge occurring between the CL electrodes is used as a "piston". When connecting the device's CL to a capacitive battery, the discharge "piston" compresses and ejects at high pressure with a speed of at least 8⋅10⁵ cm/s atmospheric gas through the outlet of the device at the end of the CL.

EFFECT: expansion of the device functional capabilities.

1 cl, 5 dwg, 2 tbl

Description

A device is proposed that ensures the achievement of supersonic air flow rates. The device will create tools for processing and cutting solid materials.

Known devices called railguns [1, 2, 3], in which accelerated bodies are located between the rails - two electrodes conductors - and are accelerated by the reactive movement of the gas discharge when connecting the rail conductors to a high voltage pulsed current source. In some designs, it is proposed to place fusible metal foil between the rails, which contributes to the ignition of a gas discharge at the beginning of the rails and turns into a discharge plasma upon melting. The current flowing through the discharge (plasma) forms a powerful electromagnetic field. Under the action of the Lorentz force, the conductor, that is, the plasma, begins to quickly move along the rail. Thus, a plasma clot, a gas discharge, becomes a plasma piston (like an analogue of a powder charge in a firearm).

The design of such devices is determined by the mass of the charge, which moves the Lorentz force along the rail.

As an analogue of the proposed device, a railgun device of any type mentioned in [1, 2, 3] can be adopted.

The lack of prototypes should be considered the practical impossibility of using a plasma piston (gas discharge) to form a high pressure gas mixture in a device for converting it into kinetic energy of a charge mass.

The technical result of this proposal is the ability to design a tool for processing solid

objects and materials with a gas jet, the speed of which is at least 15 _° C S (C _° S is the speed of sound in air).

Based on the proposed device, it is also possible to create a structure for launching charges with a mass of up to 1000 g at a specified speed and above.

The explanation and justification of the design features and operation of the proposed device is presented in the following figures and diagrams:

FIG. 1 is a physical model illustrating the operation of the railgun;

FIG. 2 is a simplified representation of the proposed design of the coaxial type;

степени ионизации α от давления p от отношения

где Е_КЛ - величины напряженности электрического поля в разрядном промежутке Δ на единицу давления;FIG. 3 - addiction

degree of ionization α from pressure p from the ratio

where E _CL - the magnitude of the electric field in the discharge gap Δ per unit pressure;

FIG. 4 - the proposed design of the device in the form of CL, where

1 - the external conductor of the cable, it is the casing

2 - conductor cuff 1 with holes for mechanical connection;

3 - inner conductor KL;

4 - an isolating disk;

5 - flange of an insulating disk 4 with holes for connection with a cuff 2;

6 - "screen" or "side" of ignition of a gas discharge;

Δ is the discharge gap;

l _KL - the length of the KL;

H is the total length of the device;

∅ _from - the diameter of the insulating disk;

d is the diameter of the holes on the cuff 2 and the flange 5;

∅ _cells - outer diameter of the CL (cuff 2);

FIG. 5 - hemispherical part of the device, where

7 - insert with a threaded view of the installation in the housing of the device 1;

8 - hole in the insert 7 for air outlet with mass m.

The proposed device for achieving supersonic speeds includes 2 metal electrodes with a discharge gap between them, which are connected from one end of the device to a high-voltage pulsed current source, and one of the electrodes is the external case of the device.

а противоположный конец внутреннего проводника жестко вакуумплотно зафиксирован в центре изолирующего диска, внешний диаметр которого также вакуумплотно соединен плоским металлическим фланцем с отверстиями, диаметры которых совпадают с фланцем и с размерами манжеты внешнего проводника для их механического жесткого соединения между собой, при этом у изолирующего диска на одном или на обоих проводниках КЛ размещен или размещены элементы для фиксации места поджига разряда.The device is made in the form of a coaxial line (CL), with conductors round in cross section, in which the line impedance KL Z _CL , constant along the line length, is set by the ratio of the inner diameter of the outer conductor d _n to the diameter of the inner conductor d _nn , while the outer conductor is made in the form glass, the bottom of which is a hemisphere with a hole for installation in the body of the hemisphere of the insert of refractory metal, the opposite end of the conductor is made in the form of a flat funnel, the expanded part of which is completed by a flat m nzhetoy apertured sleeve plane wherein the perpendicular axis KL, KL and the inner conductor in the zone of the hemisphere of the outer conductor also has a hemispherical shape while maintaining a TC zone discharge gap distance equal

and the opposite end of the inner conductor is rigidly vacuum-tightly fixed in the center of the insulating disk, the outer diameter of which is also vacuum-tightly connected by a flat metal flange with holes whose diameters coincide with the flange and with the dimensions of the cuff of the outer conductor for their mechanical rigid connection to each other, while the insulating disk is one or both of the CR conductors has or has placed elements for fixing the place of ignition of the discharge.

In another embodiment of the device, the said refractory metal insert is installed in the hemispherical part of the outer conductor so that the axis of the insert coincides with the axis of the CL, the internal shape of the insert retains the shape of the hemisphere when it is installed, and the area of the outlet in the insert is determined from the formula

where S _resp - the area of the outlet,

S _KL - the area of the ring in the working volume of the device,

V _con - the speed of the "piston" at the entrance to the hemisphere of the device,

V _o - the outlet air velocity from the outlet.

In FIG. Figure 1 shows the physical model of the railgun, where the force F is the Lorentz force of the gas discharge provides a high speed of its movement along the CR. The force F in this case is determined by the formula

μ - magnetic permeability (μ = 1.26⋅10 ^-6 Gn / m = 12.6 since 1 Gn = 10 ⁹ cm),

I is the current flowing along the rails,

d and r are respectively the diameter of the rail and the distance between them.

In the author's presentation, the design of the proposed coaxial railgun can also be formed with a larger number of rails arranged in a circle with equal discharge gaps. And in this design, the external rails can be combined into a single external ring conductor, and the internal rails into a single internal conductor. With a certain length of conductors, a coaxial cable line with a current discharge running along it (a plasma piston) appears, as shown in FIG. one.

According to the condition in the proposed device, the force F generated by the gas discharge is similar to a powder piston pushing a charge in the barrel of a small arms, that is, it acts on the gas mixture of mass m for a time Δt _air

m is the mass affected by the force F _{air in} order to reach the final velocity V _kon equal to V _kon = 10⋅C _sv = 3.4⋅10 ⁵ cm / s at the hemispherical shape of the external conductor during the time Δt _air .

Equating expressions (1) and (2), we calculate the value of current I in the device by the expression

см/с.Consider the operation of the proposed device when forming at the exit of a gas jet at a speed

cm / s.

For this case, we set in expression (3) the expected values of the input quantities:

),m = 2⋅10 ^-4 ⋅1293 = 0.2 g - the weight of air in the volume of the device, which can vary from 1.6⋅10 ^-4 m ³ (take the value

),

получим

и примем среднее значение

since r _n and r _VN are the radii of the outer and inner diameters d _n and d _VN , then taking the ratio

we get

and take the average value

In this case, the value of I turns out to be time-dependent Δt _air , the numerical values of which are given in table 1.

To determine the parameters of the pulsed power supply unit with a capacitance C _b and a battery inductance L _b, we find the energy necessary to reach a speed of 15 C _{sv with} mass m

As a condition, we assume that the energy E _{m is} fully provided by the energy of the capacitor bank, i.e.

From the expression (4), if we take U _b = 3⋅10 ⁴ V, C _b will be equal to

As a rule, the battery capacity C _b used for high-voltage switching power supply has a value of at least 1 μF [4]. Due to the fact that the current value I from expression (3) is minimum, its maximum value I _max can be determined from the equality

откуда

where from

с I_max=1,7⋅10⁴ А,In this case, when

with I _max = 1.7⋅10 ⁴ A,

and at Δt _air = 10 ^-5 c I _max = 1.7⋅10 ³ A.

We define the requirement for the inductance of the power battery L _b , provided that the duration Δt _air is equal to the half-cycle of the circuit formed by C _b and L _b

To reduce the operating values of I, the duration Δt _air should be set in the range (1 ÷ 5) ⋅10 ^-5 s and L _b will be equal to 0.4⋅10 ^-5 GN and. 10 ^-4 G.

The calculated value of L _b should be used and taken into account when choosing the type of capacitor bank.

The calculation of the dimensions of the conductors of the device will produce from the condition that the voltage drop should not exceed 5% of U _b , that is

I⋅R _pr = 0.05⋅U _b , whence at I _max = 3⋅10 ⁴ A

The resistance of the CR conductors R _pr is determined by its material and the size of the known dependence

, где

where

ρ - resistivity of the material ohm

(ρ is 0.0175 for copper and 0.016 for silver),

S _CR - the cross section of the inner conductor in mm ² ,

l _CR - the length of the conductor in m

We define the length of the conductor l _CR (that is, the length of the CR to the boundary of the transition of the external conductor to the hemisphere) assuming that at the end of the length the piston speed reaches V _con .

and for two values of Δt _air - 10 ^-5 s and 5⋅10 ^-5 s

the length of the cable will be 2.5 cm and 12.7 cm.

м и при ρ=0,0175Will accept

m and at ρ = 0.0175

с по поверхности проводников с глубиной проводящего слоя

мм. В этом случае радиус внутреннего проводника КЛ r_вн может быть вычислен из равенстваSince the effect on CR is pulsed, the current will flow at

c along the surface of the conductors with a depth of the conductive layer

mm In this case, the radius of the inner conductor KL r _vn can be calculated from the equality

откуда

where from

The obtained small value of the calculated value of r _vn gives the right to freely choose the diameter of the inner conductor d _vn from the desirability of achieving the mechanical strength of the inner conductor as a console in the design of the device, and to prevent overheating of the conductor during operation of the device.

We establish the diameter d _int = 8 mm (r _int = 4 mm), then the inductance L _KL and the capacitance C _{KL are} calculated according to the known formulas [5]

,where ε is the dielectric constant 8.85⋅10 ^-12

,

значение

тогда C_КЛ=0,95⋅10^-13 Ф и L_КЛ=7,3⋅10^-8 Гн.and with a range of changes in the ratio

value

then C _KL = 0.95⋅10 ^-13 F and L _KL = 7.3⋅10 ^-8 G.

The calculated values C _CR and _CR L, being the actual load for the capacitor banks have practically no influence on the formation of duration Δt _Air (see. The expression (5).

We analyze the conditions for the formation of a gas discharge in the gap r _n -r _int = Δ. From the general theory of electrical conductivity in gases, it is known that in a gas medium between electrodes of a voltage equal to the ignition voltage U _zag , a gap (breakdown) occurs in the gap.

The discharge is achieved at gas pressure P if the condition [6]

where α is the primary ionization coefficient (Townsend coefficient), γ is the coefficient of secondary electron emission of the cathode (inner CR conductor). Note that the value of the coefficient γ for various metals from which the device can be made (copper, iron, aluminum, etc.) lies in the range from 0.01 to 0.1.

то есть зависимости числа ионов α, возникающих на длине в 1 м при давлении 1 мм рт.ст. от величины напряженности электрического поля E_КЛ на единицу давления в мм рт.ст.

откуда U_б=Δ⋅p.In FIG. 3 shows the dependence of the degree of ionization

that is, the dependences of the number of ions α arising over a length of 1 m at a pressure of 1 mm Hg from the magnitude of the electric field strength E _CR per unit pressure in mm Hg

whence U _b = Δ⋅p.

We use expression (9) and the dependence from FIG. 3 to assess the operating mode of the device with the following parameters:

a) atmospheric pressure in the device - 760 mm RT.article,

b) the discharge gap Δ - 10 and 12 mm,

c) the value of a is calculated from (9)

The calculation results are summarized in table 2.

From the table. 2 it follows that with a decrease in U _b to the proposed value of 3⋅10 ^4, an increase in γ is possible (for example, to 0.07), which allows to reduce Δ.

It should be recalled that with a value of Δ⋅p <0.005, the ignition potential begins to increase sharply. The reason for this is that the mean free path of the electron becomes comparable with the discharge gap Δ, as a result of which the probability of their collisions with gas molecules decreases.

The justification for the choice of the parameters Δ, E, and _CL indicates the possible combination of their values to select the optimal design solutions.

Let us evaluate the possibility of the CR operation as a plasma piston.

Let us evaluate the possibility of working in a CR discharge as a discharge piston. In the initial state, the number of molecules in the gas mixture n _mol at a given pressure is determined by the well-known formula ^%

where p is the pressure in the volume V,

n _o - the number of molecules in 1 m ³ equal to 3.54 × 10 ²² at p = 1 mm Hg

With the accepted volume (a change from 1.6⋅10 ^-4 m ^{3 is} possible) the number of molecules will be equal

n _mol = 3.54⋅10 ²² ⋅760⋅1.6⋅10 ^-4 = 4.3⋅10 ²¹ mol,

the number of charges of the same sign (electrons) at a current of 5⋅10 ⁴ A

where e is the electron charge of 1.6⋅10 ^-19 C and the number of electrons is

n _email = 2⋅10 ¹⁸ email

It is clear that with a uniform distribution of air molecules n _mole in the working volume of the device, the condition n _el ≈n _mole will be fulfilled, that is, the air density in front of the “piston” will always be comparable with the number of discharge charges.

Based on the foregoing, the proposed device in FIG. 4 is presented as a coaxial line.

The outer conductor 1 has the form of a cylindrical glass with a bottom in the form of a hemisphere on one side and the transition of the glass into a flat conical shape with a cuff 2 with through holes in it on the opposite side of the glass.

The inner conductor 3 is a round metal rod, one end of which is rigidly vacuum-tightly fixed in the center of the insulating disk 4, the plane of which is perpendicular to the CR axis. The opposite end of the conductor 3 also has the shape of a hemisphere.

, где d_н и d_вн соответственно внутренний диаметр внешнего проводника и диаметр внутреннего проводника, которые определяют волновое сопротивление КЛ Z_КЛ.The discharge gap Δ in the CR is determined by the ratio

, where d _n and d _vn, respectively, the inner diameter of the outer conductor and the diameter of the inner conductor, which determine the wave impedance KL Z _KL .

The insulating disk 4 on the outer diameter is vacuum tightly connected to a metal flange 5, the dimensions of which and the holes in which coincide with the dimensions and holes of the cuff 2.

To prevent breakdown on the surface of the insulating disk 4, its shape when connected to a power source can be complex (it is shown in Fig. 4.)

In the zone of the insulating disk 4 on one of the cable conductors (this is the inner conductor 3 in Fig. 4), the placement of a “screen” 6 of low-melting foil for fixing the place of ignition of a gas discharge is shown. A different formation of the ignition site is possible - on the inner conductor at the location of the foil, a protruding “side” with a height of not more than 0.6 Δ is performed with a smooth drop to d _vn at a length of at least 2Δ (in Fig. 4, a “side”).

In FIG. 5 shows the hemispherical part of the external conductor of the device, where the replaceable refractory metal insert 7 is shown with a hole 8, from which air escapes at high speed and under high pressure during the discharge. Moreover, the distance Δ in this part of the device remains constant. The axis of the hole 8 in the insert 7 and the axis of the CL are the same.

L CR _CR length determined by the length of the inner conductor 3. The total length of the device H defines the length of the outer conductor 1 by flange 5 on the insulating disk 4. The diameter of insulating disk 4 - ∅ _of the diameter of the holes in the flange 5 and a cuff 2 - ∅ _holes, exterior cuff diameter 2 - ∅ _КЛ .

The device is connected to a pulsed high-voltage current source by mechanical household ties, the inner conductor from the outside is threaded for this. The connection of the housing of the device 1 is also mechanical using the holes for the bolt tie.

We calculate the pressure that occurs in the hemisphere of the device V _{p / sf} (Fig. 5).

The pressure P _air is related to the energy of translational motion of air molecules by the expression

where V _{p / sf} is the volume of air enclosed in the hemispherical part,

m _j and V _j are the mass and velocity i of the air molecule, respectively.

When the piston reaches the speed V _con , in particular the following value - V _con = 15⋅C _sv = 5.1⋅10 ⁵ cm / s, the volume air flow entering the hemispherical part of the device under the action of the Lorentz force is equal to V _con ⋅ S _KL ,

Where

Assuming that the entire flow of the compressed air comes out through an insertion hole area S d _{of holes of holes,} then the speed V _O of the effluent may be calculated from the equation

мм S_отв=3,14⋅10^-2 см²,

что превышает 1-ую космическую скорость. Расчет показывает, что значение V_вых может быть уменьшено путем уменьшения V_кон, то есть уменьшения длины устройства L_КЛ.and with

mm _holes S = 3,14⋅10 ^-2 cm ^2,

which exceeds the 1st cosmic velocity. The calculation shows that the value of V _o can be reduced by decreasing V _con , that is, reducing the length of the device L _KL .

The pressure that the outgoing air stream P _air generates is calculated according to (12) and provided that

m = 0.2 g, and V _con = 5.1⋅10 ⁵ cm / s, we obtain

where from

The CL impedance is [7, 8]

where ε is the dielectric constant,

Ом, а для зоны нахождения изоляционного диска с диаметром ∅_из целесообразно рекомендовать диэлектрик с меньшим значением (при ε=3 ∅_из=70 мм).as a result, at given values of r _int = 4 mm and r _n = 14 mm

Ohm, and for the zone of location of the insulating disk with a diameter of ∅ _of it is advisable to recommend a dielectric with a lower value (with ε = 3 ∅ _of = 70 mm).

According to the authors, the proposed device is capable of machining solid materials (metal, stone, wood, etc.).

REFERENCES:

[1] “Jet propulsion during a gas discharge from an external current lead” - M .: RAS, JETP Letters, vol. 13, No. 15, 1989

[2] Ageev A.A. “Electromagnetic gun-weapon of the future”, Techkult website, 09/21/2011

[3] Russian Cosmos, journal No. 9, 2011

[4] Russian Technology Group 2 CJSC RTG-2 - high-voltage power supplies, capacitors, dischargers, control systems; e-mail: rastgr2@yandex.ru.

[5] Koshkin N.I., Shirkevich M.G. "Reference to elementary physics" "- M .:" Science ", 1965

[6] Lynch P., Nikolaydes A. "Tasks on physical electronics" - M .: ed. The World, 1975

[7] Atabekov G.I. "Theoretical Foundations of Electrical Engineering" - M .: Energy, 1970

[8] Gunston M.A. "Guide to wave impedances of microwave feeder lines" (translation from English. A. Fradkina) - M .: Communication, 1976

Claims (7)

1. A device for achieving supersonic speeds, comprising two metal electrodes with a discharge gap between them, which are connected from one end of the device to a high-voltage pulse current source, while one of the electrodes is an external housing of the device, characterized in that the device is made in the form coaxial line (CL), with conductors round in cross section, in which the wave impedance of the CL is set by the ratio of the inner diameter of the outer conductor d _n to the diameter of the inner conductor d _nv Z _KL , constant along the length of the line, while the outer conductor is made in the form of a cup, the bottom of which is a hemisphere for installation of a refractory metal insert with a hole in the hemisphere body, the opposite end of the conductor is made in the form of a flat funnel, the expanded part of which is completed with a flat cuff with holes, the cuff plane is perpendicular to the CR axis, and the inner CL conductor in the hemisphere of the outer conductor also has a hemispherical shape while maintaining the distance between the discharge gap in the CL zone weaving equal

and the opposite end of the inner conductor is rigidly, vacuum tightly fixed in the center of the insulating disk, the outer diameter of which is also rigidly, vacuum tightly connected with a flat metal flange with holes whose diameters coincide with the dimensions of the openings of the cuff of the outer conductor for mechanical rigid connection with each other, while the insulating the disk on one or both conductors of the cable is placed or placed elements to fix the place of ignition of the discharge. 2. The device according to claim 1, characterized in that the said refractory metal insert is installed in the hemispherical part of the external conductor so that the axis of the insert coincides with the axis of the cable, the internal shape of the insert retains the shape of the hemisphere when it is installed, and the area of the outlet in the insert determines from the formula:

where S _resp - the area of the outlet, S _KL - the area of the ring in the working volume of the device, V _con - the speed of the "piston" at the entrance to the hemisphere of the device, V _o - the outlet air velocity from the outlet.

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