CN110198590B - Method for researching characteristics of sheath layer of magnetic control plasma - Google Patents
Method for researching characteristics of sheath layer of magnetic control plasma Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 25
- 239000007789 gas Substances 0.000 claims abstract description 134
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- 239000003380 propellant Substances 0.000 claims description 28
- 150000002500 ions Chemical class 0.000 claims description 27
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Abstract
The invention discloses a method for researching the characteristics of a sheath layer of a magnetic control plasma, which belongs to the field of a sheath layer of a magnetic confinement plasma and comprises the following steps: s1: generating plasma at 3000-4000 k; s2: loading current of the electromagnetic coil; s3: generating an induction electric field, and generating an excitation electric field by an external magnetic field, wherein the acceleration effect of the electric field on particles can enable initial electrons in high-temperature fuel gas to form an avalanche ionization effect; s4, forming a magnetic confinement plasma sheath layer; s5: the thermal insulation effect of the magnetic confinement plasma sheath layer; s6: the magnetically confined plasma sheath suppresses the dynamic heat flux density. According to the method for researching the characteristics of the sheath layer of the magnetron plasma, after a parallel magnetic field is applied, the motion of charged particles is changed into the rotary motion around magnetic lines of force, the heat flow density of the plasma transmitted across the magnetic field is reduced, and the temperature rise of the inner wall surface is reduced along with the reduction of the heat flow density transmitted by gas, so that the heat ablation resistance of the body pipe is improved, and the service life is prolonged.
Description
Technical Field
The invention relates to the field of magnetic confinement plasma sheath layers, in particular to a method for researching the characteristics of a magnetic control plasma sheath layer.
Background
The plasma is an ionized gas-like substance consisting of positive and negative ions generated by exciting partial atoms or molecules under high temperature or specific excitation, and is in a fourth state except solid, liquid and gas states, gunpowder gas can be ionized to form plasma when a cannon emits, a project group applies a magnetic field parallel to the axial direction of the cannon barrel on the outer wall of the conventional cannon barrel, so that electrons and charged ions in the plasma are confined on the inner wall of the cannon barrel to form a non-electric neutral region, namely a magnetic confinement plasma sheath layer, and the formation of the magnetic confinement plasma sheath layer depends on the generation of the plasma and the transient action of the magnetic field.
When the barrel is used for transmitting, the gas inside the barrel flows at a speed higher than the sound speed along the orientation of the barrel in the thermal expansion process, the Mach number of the gas is about 1.2, the Mach number of the gas exceeds the sound speed, in the thermal expansion process of the gas, partial gas can be expanded to form gas heating heat energy due to the generation of shock waves, the density of the gas at the shock wave section is increased, the temperature of the gas is increased, the energy of the gas is transmitted to the barrel wall, and the shock waves are easy to cause ablation at the middle front part of the pipe wall due to the characteristics of high density and high temperature of the shock waves, namely more heat and higher high pressure are transmitted to the barrel at the middle front part of the pipe wall.
Disclosure of Invention
The invention aims to provide a method for researching the characteristics of a sheath layer of a magnetron plasma, which aims to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme: the method for researching the characteristics of the sheath layer of the magnetic control plasma comprises the following steps:
s1: generating plasma, wherein the radial bore pressure of the interior of the barrel is as high as 400MPa and the temperature is as high as 3000-4000 k when the barrel is launched;
s2: loading current of the electromagnetic coil;
s3: generating an induction electric field, and generating an excitation electric field by an external magnetic field, wherein the acceleration effect of the electric field on particles can enable initial electrons in high-temperature fuel gas to form an avalanche ionization effect;
s4, forming a magnetic confinement plasma sheath layer;
s5: the thermal insulation effect of the magnetic confinement plasma sheath layer;
s6: the magnetically confined plasma sheath suppresses the dynamic heat flux density.
Preferably, in S1, the barrel wall material of the barrel facing the high temperature, high pressure gas has a resistance to compression of about one half of the bore pressure of 200MPa and the additional 200MPa bore pressure is distributed to the barrel skin material by the material magnetic field.
Preferably, in S2, the solenoid is energized with a steep pulse front to cause the current on the solenoid to form a steep rising front from zero to 1000A in 10ns, resulting in the magnetic field generated by the solenoid rising from zero to 0.2T in 10 ns.
Preferably, in S3, the electromagnetic coil is accelerated by an induction angle electric field of 10ns, so that 2% ionization of the combustion gas occurs in the barrel, the electron density of the plasma generated by the ionization is about 2% of the density of the combustion gas in the barrel, the average temperature of the electrons is about 10eV, the radius of gyration of the electrons in the average magnetic field of 0.1T is about 17 μm, and the radius of gyration of the ions is about 2 mm.
Preferably, in S4, the time-varying magnetic field of the plasma sheath generates an angular induced electric field in the barrel, and the angular induced electric field accelerates the initial electrons to 20eV kinetic energy and generates avalanche ionization by collision with neutral gas molecules.
Preferably, in S5, under the condition that the thermal conductivity of the barrel material is not changed, the high-temperature and high-pressure properties of the gas fuel for the propellant of the launched barrel are not changed, and due to the application of the magnetic confinement plasma sheath, the heat flux density of the gas fuel transferred to the inner wall of the barrel is reduced by 33%, and the temperature of the gun steel material on the inner wall of the barrel is reduced by about 30%.
Preferably, in S6, during the combustion of the propellant inside the barrel, the fuel releases a large amount of heat during the rapid combustion process and is decomposed into small molecules with some macromolecules through oxidation, so that the temperature of the gas molecules is increased and the number density of the molecules is increased to form an explosion process, the gas molecules at the explosion point expand rapidly to push the outer layer gas to move outwards along the barrel, and the outer gas is pushed by the explosion point gas to generate a compression phenomenon.
Preferably, during the combustion of the fuel, the kinetic energy of the high-temperature combustion gas will be partially converted into the heat energy of the surrounding low-temperature gas, and the part of the energy converted into the heat energy of the surrounding gas reduces the emission efficiency of the propellant of the object to be emitted, i.e. the chemical energy contained in the propellant is converted into the kinetic energy ratio of the object to be emitted.
Compared with the prior art, the invention has the beneficial effects that: on the basis of traditional fluid mechanics, Lorentz force and Joule heat are respectively added into a momentum and energy conservation equation, a magnetic confinement plasma jet flow thermo-magnetic coupling model is constructed, and research results show that: the motion of the charged particles after the parallel magnetic field is applied is changed into the rotary motion around the magnetic force line, the heat flow density of the plasma transmitted across the magnetic field is reduced, and the temperature rise of the inner wall surface is reduced along with the reduction of the heat flow density transmitted by the fuel gas, so that the heat ablation resistance of the barrel is improved, and the service life is prolonged.
Drawings
FIG. 1 is an overall flow chart of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the present invention provides a technical solution: the method for researching the characteristics of the sheath layer of the magnetic control plasma comprises the following steps:
s1: the plasma is generated, the radial bore pressure in the plasma reaches 400MPa when the plasma is emitted, the temperature reaches 3000-4000 k, the deformation and abrasion of high-temperature and high-pressure gas on a pipeline material are serious, through the application of the high-toughness ultra-light active thermal protection material, the pressure resistance of the wall material of the barrel facing the high-temperature and high-pressure gas does not need to resist the total bore pressure of 400MPa, but half of the bore pressure is 200MPa, and the bore pressure of the other 200MPa is dispersed on the outer layer material of the barrel through a material magnetic field, so that the damage of the barrel is greatly reduced, and meanwhile, the requirement on the mechanical property of the wall material of the barrel is reduced;
assuming that the pressure in the body tube of the object to be shot reaches 400MPa when the object to be shot is shot, the inner diameter of the body tube is about 120mm, and the cross section area is about:
S＝0.25πD2＝0.25×3.14×(0.12)2＝1.13×10-2(m2)
total thrust of the emitted gas:
F＝PS＝400×106×1.13×10-2＝4.52×106(N)
the weight of the launched object is about 10kg, and the acceleration of the propellant to the launched object is about:
the length of the barrel is about 5m, and the acceleration time of the launched object from inside the barrel is about:
the exit velocity of the object to be launched is about:
Vt＝at＝4.52×105×4.7×10-3＝2124(ms-1)
the initial velocity of the actual launched object leaving the bore is about 1800ms-1, because the pressure of the launched gas is weakened due to combustion and gas expansion in the barrel, the thrust of the gas is not constant, resistance exists between the launched object and the barrel, the outlet velocity cannot reach the ideal velocity, the launched explosive is supposed to be sufficiently combusted in the cartridge case to form high-temperature and high-pressure gas, the density of the gas is gradually reduced and the pressure is gradually weakened along with the outward movement of the battle part of the launched object along the barrel, and the density of the gas in the barrel is about:
the partial high-energy particles in thermal equilibrium distribution collide with each other, so that a small part of gas molecules are ionized, the temperature of electrons is about 1eV, the temperature of ions is at the neutral particle temperature of 4000K and 0.4eV due to the large collision section and the high energy exchange efficiency between ions and molecules, the heat effect of the ionized plasma on the barrel is almost negligible, and the heat flow density (heat transferred on unit time and unit area) of high-temperature and high-pressure gas generated by propellant combustion transferred to the barrel wall is as follows:
wherein n iso、ToIs the density and temperature of the propellant gas in the barrel, P is the total pressure in the wall, k is the Boltzmann constant, maIs the weighted average mass of the gas molecules, assuming:
ma＝20×1.67×10-27＝3.34×10-26(kg)
sound velocity in high-temperature high-pressure gas:
in the thermal expansion process of the gas, the directional flow speed of the gas along the barrel is greater than the sound velocity, the Mach number of the gas is about 1.2, and exceeds the sound velocity, in the thermal expansion process of the gas, part of the gas can be expanded into gas heating heat energy due to the generation of shock waves, so that the density and the temperature of the gas at the shock wave section are increased, the energy of the gas is transmitted to the barrel wall, and the shock waves easily cause ablation at the middle front part of the pipe wall due to the characteristics of high density and high temperature of the shock waves that more heat and higher high pressure are transmitted to the barrel at the middle front part of the pipe wall;
the heat flow transferred by the fuel gas of 400MPa and 4000k to the barrel wall under the average condition is about:
if the density behind the shock wave surface is increased by about 1 time due to the formation of the shock wave, the temperature is increased by 50 percent, the heat flow density is increased by 3 times, the formation of the thermal collision shock wave in the barrel is inhibited, which is one of the important measures for reducing the thermal ablation of the barrel, the magnetic confinement plasma tube technology can play a role in reducing the Mach number of the explosion shock wave, the energy of the emission gas is reduced and is transmitted to the barrel through the gas heated by the shock wave, the current on the coil is increased from zero to 1000A from the ignition of the emission drug of the object to be emitted, the period is about 0.01ms, an axial magnetic field is formed in the barrel, the magnetic field is increased from zero to 2000Gs within 0.01 mus,
due to faraday's law of electromagnetic induction:
the magnetic field generated by the solenoid coil is in the Z direction, the field increasing with time generates an induced electric field in the barrel, which is angular in a cylindrical coordinate system, the inside radius of the barrel is Ro, and the integral along the inside loop of the barrel:
Eθ(r＝Ro)＝-107Ro(Vm-1)＝6×105(Vm-1)
the induced electric field generated by the changing magnetic field near the wall of the barrel is the largest, and assuming that ionization is generated due to particle collision on the high-energy tail of the particle molecules in high-temperature and high-pressure gas, initial electrons and ions are generated, the ionization component of the initial ionization accounts for negligible total gas density, the energy of the initial electrons is about 1eV, the energy of the ions is about 0.4eV, the electrons and the ions do cyclotron motion in a background axial magnetic field, the median value of the background magnetic field is about 0.1T, and the cyclotron radius of the electrons is:
radius of gyration of ion:
induced electric field EθThe electrons are accelerated during the electron cyclotron half-cycle so that the electrons gain about:
Δεe＝2rLeEθ＝2×16.9×10-6×6×105＝20.28(eV)
the mean free path of the initial electrons in the gas is about:
the number of collisions that occur between electrons and neutral gas molecules during a cyclotron half-cycle is approximately:
the kinetic energy lost by an electron per collision with a gas molecule is approximately:
the electrons are accelerated from an induction angle of 1eV to 20.28eV, the average energy is about 10eV, the loss is 2.73X 10-4eV per collision with neutral gas molecules, the total loss energy is about 3845 collisions in a half-cycle period, and the total loss energy is about:
ΔWc＝3845×2.73×10-4＝1.05(eV)
under the acceleration of the induced angular electric field, the acceleration energy of the electrons after a half of the cyclotron period is about 20eV, the electrons collide with neutral molecules to have the kinetic energy of ionized molecules, the kinetic energy of the initial electrons after the acceleration of the induced angular electric field can still be accelerated to the energy above 20eV by the electric field after the kinetic energy is lost through elastic collision with the neutral gas molecules, the acceleration time is about half of the cyclotron period of the electrons in a 0.1T magnetic field, and the cyclotron frequency of the electrons in an average magnetic field of 0.1T is about:
time for electrons to be accelerated by the induced angular electric field:
the duration of the induction electric field is about 10ns, electrons can be accelerated from 1eV to energy above 20eV 28 times in an electron cyclotron period, so that an ionization avalanche phenomenon occurs in a barrel, an initial electron is accelerated to kinetic energy of 20eV by the angular electric field, neutral gas molecules are impacted to generate ionization, an ionized electron and an original impact electron are generated, namely two electrons appear in the gas after primary ionization, the two electrons are decelerated to 20eV by the electric field within the time of 3.6 x 10-10s, 4 electrons are generated by the impact, and 228 electrons are generated by 28 times of impact;
s2: the loading of the current of the electromagnetic coil, in order to improve the initial emission speed of the object to be emitted and reduce the thermal ablation of the high-temperature high-pressure gas to the barrel, 2% of ionized plasma is required to be generated in the high-temperature high-pressure gas, the ionized components in the high-temperature high-pressure gas of 400MPa and 4000K can be almost ignored, the ionization rate cannot exceed one ten thousand, the electron temperature is below 1eV, even if a magnetic field is loaded, the initial speed of the object to be emitted is difficult to improve and the thermal ablation of the high-temperature high-pressure gas to the inner wall of the barrel is reduced, in order to improve the ionization rate of the high-temperature high-pressure gas, the invention adopts the power-up mode of the steep pulse front, so that the current on the electromagnetic coil forms the steep rising front, and rises from zero to 1000A within 10ns, and the magnetic field generated by the coil rises from zero to 0.2T within 10 ns;
s3: the induced electric field is generated, the external magnetic field generates an excitation electric field, the acceleration effect of the electric field on particles can enable initial electrons in high-temperature fuel gas to form an avalanche ionization effect, statistical results show that through the acceleration of the induced angular electric field of 10ns, 2% of combustion gas in a barrel is ionized, the electron density of plasma generated through ionization is about 2% of the fuel gas density of the barrel, the average temperature of electrons is about 10eV, the gyration radius of electrons in an average magnetic field of 0.1T is about 17 mu m, the gyration radius of ions is about 2mm, and the plasmas confined by the magnetic field can greatly change the dynamic process of the fuel gas in the barrel, so that characteristics beneficial to performance improvement are generated, such as: the initial velocity of the shot object out of the chamber is improved, and the ablation of high-temperature and high-pressure gas to the barrel is reduced;
s4: forming a magnetic confinement plasma sheath layer, wherein plasma electrons generated by avalanche are confined by a magnetic field within the time that the magnetic field generated by a coil reaches 0.2T and is maintained for 5ms, the electron cyclotron radius of the plasma electrons is about 20-60 mu m, and the magnetic confinement plasma sheath layer is formed in the thickness of 40-120 mu m near the inner wall of a barrel, wherein the density of electrons is about:
ne＝0.02no＝0.02×7.25×1027＝1.45×1026(m-3)
the average temperature of electrons in the sheath is about 10 eV;
the total pressure within the magnetically confined plasma sheath is about:
wherein the magnetic pressure:
pressure of electrons:
Pe＝nekTe＝1.45×1026×10×1.6×10-19＝2.32×108＝232(MPa)＝0.58Po
pressure of the ion:
Pi＝nikTi＝1.45×1026×1.38×10-23×4000＝8×106＝8(MPa)
the density of neutral gas molecules in the magnetically confined plasma sheath layer with the thickness of 40-120 μm on the inner wall of the barrel is about:
the magnetic confinement plasma sheath layer in the barrel is mainly characterized in that: the magnetic field which changes rapidly along with time generates an angular induction electric field in the barrel, the angular induction electric field accelerates initial electrons to reach the kinetic energy of 20eV and collides with neutral gas molecules to generate avalanche ionization, so that 2% of gas ionization is generated in the thickness of 40-120 mu m, the density of ionized plasma electrons is about 2% of the density of the original neutral gas, the temperature of the electrons is about 10eV, the electrons are restricted by an axial magnetic field, the convolution radius of the electrons is about 20-60 mu m, the electrons restricted by the magnetic field form a heat-insulating shielding-like layer in a sheath layer with the thickness of 40-120 mu m, the hot pressure of magnetically restricted electrons is about 232MPa and accounts for 58% of the total pressure of the inner layer gas, the density of the neutral gas in the magnetically restricted plasma sheath layer is greatly reduced only by 40% of the original density due to the existence of the magnetically restricted electrons in the thickness of 40-120 mu m close to the inner wall of the barrel, this causes the heat flux density of the neutral gas molecules and heavier ions which are not restricted by the magnetic field to be reduced by 60 percent;
s5: the thermal insulation effect of the magnetic confinement plasma sheath, and the mass flow density of the diffusion of the magnetically confined electrons to the inner wall of the barrel:
wherein venIs the collision frequency, ω, of electrons with neutral gas moleculesceIs the cyclotron frequency of the electron in the magnetic field;
wherein
Is the thermal velocity of electrons in the magnetically confined plasma sheath;
is the mean free path of the collision of electrons with neutral gas molecules in the sheath;
the electron current density carries a heat flux density of about:
Γeth＝εeΓem＝16×10-19×3.46×1028＝55.4GWM-2
the density of neutral gas molecules and ions in the sheath layer is about 40% of the density of gas without ionization, and the temperature of the neutral molecules and ions is still 4000K, so that the heat flow density of the neutral gas and ions transmitted to the inner wall of the barrel in the sheath layer is about:
Γoth＝0.4Γth＝0.4×205＝82(GWm-2)
therefore, the total heat flow density of the high-temperature and high-pressure fuel gas burnt by the propellant in the barrel transmitted to the gun steel material on the inner wall of the barrel through the magnetic confinement plasma sheath layer is about:
Γt＝Γeth+Γoth＝55.4+82＝137.4(GWm-2)＜205(GWm-2)
from the above formula, it can be clearly analyzed that, due to the existence of the magnetic confinement plasma sheath, the heat flux density of the gas in the barrel transmitted to the barrel wall steel material is reduced by about 33%, due to the reduction of the heat flux density of the gas transmitted to the barrel wall, an important effect is brought, the temperature of the inner wall of the barrel steel is reduced, and the reduction of the temperature of the barrel steel also correspondingly improves the ablation resistance of the barrel steel, so that the ablation resistance of the barrel is improved, the ablation of the barrel is reduced, the service life of the barrel is prolonged, if the heat conductivity of the barrel material is unchanged, the high-temperature and high-pressure performance of the propellant gas of the object to be launched is unchanged, due to the application of the magnetic confinement plasma sheath, the heat flux density of the gas transmitted to the inner wall of the barrel is reduced by 33%, and the temperature of the steel material on the inner wall of the barrel is reduced by about 30%, which is an important application characteristic of the magnetic confinement plasma sheath in the barrel, the temperature rise of the propellant gas to the inner wall material of the barrel is reduced;
the magnetic confinement electrons of the magnetic confinement plasma sheath layer act like a heat insulation layer with the thickness of about 120 microns in the body tube, the electrons are confined in the direction of a vertical magnetic field by an axial magnetic field to do a rotary motion so as to cause the density of diffusion flow of the electron vertical magnetic field to be reduced, the hot pressure formed by the electrons squeezes the hot pressure of neutral gas and ions, the density of gas molecules and ions which are not confined by the magnetic field in the sheath layer is reduced by 60%, the total hot flow density of the gas is reduced by 33%, therefore, the temperature rise of the material on the inner wall of the body tube is reduced by about 30%, the thermal ablation and thermal shock damage degree of the gas molecules to the inner wall of the body tube are reduced by the existence of the magnetic confinement plasma sheath layer, the service life of the body tube is prolonged, and under the condition that the plasma sheath layer is not confined magnetically, the temperature rise of the body tube is reduced
Barrel warm-up in the presence of magnetically confined plasma sheath
Wherein C is the thermal capacity of the thin layer of the inner wall of the barrel, T is the temperature of the inner wall of the barrel without the magnetic confinement plasma sheath, and gammathThe heat flux density of high-temperature and high-pressure fuel gas transferred to the barrel wall when no magnetic confinement plasma sheath layer exists, and q is the heat flux density of outward conduction of the barrel inner wall; gamma-shapedtThe total heat flow density transmitted to the inner wall of the barrel when the magnetic confinement plasma sheath layer exists is obtained by utilizing (A) to (B):
from the equation (C), it can be clearly analyzed that the existence of the magnetic confinement plasma sheath layer causes the reduction of the heat flux density of the high-temperature and high-pressure fuel gas of the propellant powder to the inner wall of the barrel, so that the temperature rise of the inner wall of the barrel is smaller than that of the non-magnetic confinement plasma sheath layer, the temperature of the inner wall of the barrel is reduced due to the existence of the magnetic confinement plasma sheath layer, the impact resistance of the barrel is improved due to the temperature reduction of the inner wall of the barrel, and the thermal ablation of the barrel is reduced;
s6: the magnetic confinement plasma sheath layer inhibits the dynamic heat flux density, the combustion process of the propellant powder in the barrel is very rapid, a large amount of heat is released in the rapid combustion process of the fuel and is decomposed into small molecules along with a plurality of macromolecules through oxidation, so that the temperature of gas molecules is increased, the number density of the molecules is increased to form the explosion process, the gas molecules at the explosion point are rapidly expanded to push outer layer gas to move outwards along the axial direction of the barrel, the outer gas is pushed by the gas at the explosion point to generate the compression phenomenon, and when the propelling speed Vo of the explosion high-temperature hot gas is greater than the sound velocity in the peripheral gas;
the kinetic energy of the high-temperature gas is partially converted into the heat energy of the peripheral low-temperature gas, and the energy converted into the heat energy of the peripheral gas reduces the emission efficiency of the propellant powder of the object to be emitted, namely the chemical energy contained in the propellant powder is converted into the kinetic energy ratio of the object to be emitted;
wherein M isHThe mass of the warhead of the launched object is calculated, the mass of the warhead of the same launched object is a constant, VH is the initial bore velocity of the warhead, ECh is the chemical internal energy of the propellant powder and is also a constant, and the efficiency of converting the chemical energy into the kinetic energy of the launched object is improved, namely the initial bore velocity VH of the warhead is directly improved;
how to further improve the initial velocity of the object to be launched from the chamber, namely improve the launching efficiency of the propellant, some researches adopt the propellant with low combustion temperature, the propellant decomposes a plurality of small molecules after burning, form high pressure by rapidly improving the molecular density of the fuel gas, but still can not solve the key point that the kinetic pressure kinetic energy of the rapidly expanding gas is converted into the heat energy of the peripheral gas, namely the shock wave heating process of the rapid expansion of the gas, because the rapid expansion of the fuel gas, the kinetic expansion velocity of the fuel gas is larger than the sound velocity in the peripheral gas, the shock wave is generated at the section of the rapidly expanding gas and the peripheral low-speed moving gas, the generation of the shock wave enables the gas dynamic pressure (directional thrust) at the front edge of the shock wave to be converted into the high-temperature thermal pressure (isotropic thrust, the propelling efficiency is obviously reduced), and the formation of the magnetic confinement plasma sheath layer in the body tube can greatly reduce the Mach number of the fuel gas in the body tube, thereby reducing the intensity of shock waves, reducing the rate of converting gas dynamic pressure into peripheral gas hot pressure, leading the gas dynamic pressure to act on the propulsion of the warhead of the object to be launched more, thereby improving the initial velocity of the warhead of the object to be launched, the main physical principle that the plasma sheath layer prevents the gas dynamic pressure from expanding rapidly to be converted into hot pressure is that an induced angular electric field is formed in a barrel due to the change of a magnetic field generated by an electromagnetic induction coil along with time, the induced electric field accelerates initial electrons to be more than 20eV within a time interval of 1.8 to 10s, the accelerated electrons collide with gas molecules to form avalanche ionization, about 2 percent of plasma is generated, the average temperature of the plasma electrons is about 10eV, the thickness is about 120 micrometers, the temperature of the ions is equivalent to the temperature of the gas molecules, about 4000K, the thickness of the ions is about 4mm, but the plasma has the natural characteristic of maintaining electroneutrality, cause some electron to inwards diffuse, and some ion outwards diffuse, because electron inertial mass is less than the quality of ion far away, cause the inside diffusion velocity of electron to be greater than the speed that the ion outwards diffused for the thickness of plasma sheath is about 2mm, and plasma ionization rate is about 1%, exists about 1% plasma in the gas, and the speed that its density disturbance propagated is the sound velocity no longer, and the vertical magnetic field direction is magnetic sound wave speed, is the ion sound velocity in the parallel magnetic field direction, and the ion sound velocity is:
where η is 0.01, γ is the ionization rate of the gase3 is the adiabatic coefficient of electrons, TeIs electron temperature, kTe10eV, so the ion sound velocity in the body tube:
while the thermal velocity of the high-pressure fuel gas in the barrel (about the dynamic pressure expansion velocity) is only 2050ms < -1 >, because of the existence of the magnetic confinement plasma (although the ionization degree is only 1 percent), the speed of the gas density disturbance propagation is due to the existence of partially ionized plasma, the density disturbance propagation not only has thermal pressure, and the electrostatic force of the charge also participates in the process, so that the speed of density disturbance propagation is higher than the speed of sound, the Mach number of dynamic pressure propagation of explosion is not 1.2 but 0.98 at the moment, shock waves are not excited, the shock waves are not heated, and the propellant powder in the pipe wall is combusted, the dynamic pressure of the rapid expansion mainly acts on the warhead, the dynamic pressure thrust of the propellant in the axial direction of the body tube is larger than that of the propellant without a magnetic confinement plasma sheath, in the radial direction of the barrel, the propagation velocity of the gas density disturbance is the magnetosonic velocity, where the alfen velocity is about:
the radially deflagrated gases in the barrel still produce shock waves which manifest as the appearance of a magnetically confined plasma sheath, resulting in dynamic pressure in the barrel in parallel axial directions
>The thermal pressing of the barrel in the radial direction, the characteristic of anisotropy of the thermal pressing originates from the existence of a magnetic confinement plasma sheath layer, so that the dynamic pressure transmitted in parallel with the barrel is not generated by shock waves, the thermalization efficiency of fuel gas is lower than that generated by radial shock waves, and the speed of propellant powder propelling a fighting part to get out of a chamber when the characteristic of the plasma sheath layer is applied to the barrel is higher than that when the plasma sheath layer is not generated;
the electron density in the magnetic confinement plasma sheath is about 1.45 x 1026m-3, the temperature of the electrons is about 10eV, the thickness of the magnetic confinement plasma sheath is about 120 microns, the electrons cannot move across the magnetic field due to the confinement of the electrons by the axial magnetic field, but the electrons collide with neutral gas molecules to cause the electrons to diffuse across the magnetic field in the magnetic field, the electron current density of the electrons diffusing across the magnetic field is about 3.46 x 1028m-2s-1, the carried electron heat current density is about 55GWm-2, and due to the existence of the magnetic confinement plasma sheath, the radial heat current density of the gas is reduced to 82GWm-2, the total heat current density is about 137GWm-2, compared with the heat current density 205GWm-2 when the plasma sheath is not magnetically confined, the heat current density is reduced by about 33 percent, the efficiency of the total chemical energy of the propellant to be converted into the kinetic energy of the warhead of the propellant is improved by about 10 percent, in addition, due to the existence of the magnetic confinement plasma sheath layer, the disturbance propagation speed of the gas density is increased to the ion sound velocity (parallel to the barrel direction), the dynamic pressure of the expansion of the deflagration gas is less heated by the shock wave, and the efficiency of the dynamic pressure thrust is also improved, so that the magnetic confinement plasma sheath layer plays a role in weakening the heat flow density transmission of the high-temperature and high-pressure gas to the barrel, and the dynamic pressure thrust along the barrel direction is increased compared with the thrust when the plasma is not magnetically confined by the plasma sheath layer.
On the basis of traditional fluid mechanics, Lorentz force and Joule heat are respectively added into a momentum and energy conservation equation, a magnetic confinement plasma jet flow thermo-magnetic coupling model is constructed, and research results show that: the motion of the charged particles after the parallel magnetic field is applied is changed into the rotary motion around the magnetic force line, the heat flow density of the plasma transmitted across the magnetic field is reduced, and the temperature rise of the inner wall surface is reduced along with the reduction of the heat flow density transmitted by the fuel gas, so that the heat ablation resistance of the barrel is improved, and the service life is prolonged.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (6)
1. The method for researching the characteristics of the sheath layer of the magnetron plasma is characterized by comprising the following steps of:
s1: generating plasma, wherein the radial bore pressure of the interior of the barrel is as high as 400MPa and the temperature is as high as 3000-4000 k when the barrel is launched;
s2: loading current of the electromagnetic coil;
s3: generating an induction electric field, and generating an excitation electric field by an external magnetic field, wherein the acceleration effect of the electric field on particles can enable initial electrons in high-temperature fuel gas to form an avalanche ionization effect;
s4: forming a magnetically confined plasma sheath; wherein,
the loading of the current of the electromagnetic coil generates 2% of ionized plasma in the high-temperature and high-pressure gas, the ionized components in the high-temperature and high-pressure gas with the pressure of 400MPa and 4000K can be ignored, the ionization rate can not exceed one ten thousandth, the electron temperature is below 1eV, in order to improve the ionization rate of the high-temperature and high-pressure gas, a steep pulse front electrification mode is adopted, the current on the electromagnetic coil forms a steep rising front, the current rises from zero to 1000A within 10ns, and the magnetic field generated by the coil rises to 0.2T within 10 ns; in order to improve the ionization rate of high-temperature and high-pressure gas, a steep pulse leading edge power-on mode is adopted, so that the current on the electromagnetic coil forms a steep rising leading edge, and the current rises from zero to 1000A within 10ns, and the magnetic field generated by the coil rises from zero to 0.2T within 10 ns;
the magnetic confinement plasma sheath layer has a heat insulation effect and can inhibit dynamic heat flux density;
the induced electric field is generated, the external magnetic field generates an excitation electric field, the acceleration effect of the electric field on the particles can enable initial electrons in the high-temperature gas to form an avalanche ionization effect, the acceleration effect of the electric field on the particles can enable the initial electrons in the high-temperature gas to form the avalanche ionization effect, 2% of the combustion gas in the barrel is ionized through the acceleration of the induced angular electric field of 10ns, 2% of the ionization of the combustion gas in the barrel is enabled, the electron density of the plasma generated through ionization is about 2% of the density of the combustion gas in the barrel, the average temperature of the electrons is about 10eV, the gyration radius of the electrons in the average magnetic field of 0.1T is about 17 μm, the gyration radius of the ions is about 2mm, the plasmas confined by the magnetic field can greatly change the dynamic process of the combustion gas in the barrel, and the plasmas confined by the magnetic field can greatly change the dynamic process of the combustion gas in the barrel, the initial velocity of the shot object out of the chamber is improved, and the ablation of high-temperature and high-pressure gas to the barrel is reduced.
2. The method for studying the characteristics of the sheath of the magnetron plasma as claimed in claim 1, wherein: at S1, the barrel wall material having the barrel facing the high temperature, high pressure gas has a resistance to pressure of 200MPa against half of its bore pressure, and an additional 200MPa bore pressure is dispersed through the material magnetic field into the barrel outer layer material.
3. The method for studying the characteristics of the sheath of the magnetron plasma as claimed in claim 1, wherein: in S4, the rapidly time-varying magnetic field of the plasma sheath generates an angular induced electric field in the barrel, and the angular induced electric field accelerates the initial electrons to 20eV kinetic energy and generates avalanche ionization by collision with the neutral fuel gas molecules.
4. The method for studying the characteristics of the sheath of the magnetron plasma as claimed in claim 1, wherein: under the condition that the heat-conducting property of the barrel material is not changed, the high-temperature and high-pressure property of the gas of the propellant of the launched barrel is not changed, and due to the application of the magnetic confinement plasma sheath layer, the heat flux density of the gas transmitted to the inner wall of the barrel is reduced by 33%, and the temperature of the gun steel material on the inner wall of the barrel is reduced by 30%.
5. The method for studying the characteristics of the sheath of the magnetron plasma as claimed in claim 1, wherein: in the combustion process of the propellant powder in the body tube, a large amount of heat is released in the rapid combustion process of the fuel, and the fuel is decomposed into small molecules along with some macromolecules through oxidation, so that the temperature of gas molecules rises, the number density of the molecules increases to form an explosion process, the gas molecules at the explosion point expand rapidly to push outer-layer gas to move outwards along the axial direction of the body tube, and the external gas is pushed by the gas at the explosion point to generate a compression phenomenon.
6. The method for studying the characteristics of the sheath of the magnetron plasma as claimed in claim 5, wherein: in the combustion process of the fuel, the kinetic energy of the high-temperature gas is partially converted into the heat energy of the peripheral low-temperature gas, and the partial energy converted into the heat energy of the peripheral gas reduces the emission efficiency of the propellant powder of the object to be emitted, namely the chemical energy contained in the propellant powder is converted into the kinetic energy ratio of the object to be emitted.
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| CN107973674A (en) * | 2017-11-17 | 2018-05-01 | 中国人民解放军陆军装甲兵学院 | Magnetized plasma TEGDN gun propellant |
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