RU2527898C1 - Low-output stationary plasma engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: plasma engine with closed electron drift comprises primary circular ionisation channel confined by structural elements from insulating materials and exposed at its outlet. At least one hollow cathode is connected with ionising gas feed line. Ring anode concentric with primary channel is spaced from its exposed end. Circular buffer chamber is arranged at primary channel inlet part, behind anode zone, its radial size exceeding that of the primary circular channel. Pipes to feed ionising gas are communicated in direction towards anode via circular distributor with zone different from that of anode.

EFFECT: higher thrust, simplified design, guaranteed operating cycle.

17 dwg

Description

The invention relates to plasma technology and is primarily intended for use in space technology as an executive body of an electro-propulsion propulsion system. The invention relates to plasma engines used in spacecraft, in particular to plasma engines with closed electron drift, called stationary plasma engines or "Hall engines".

Such engines are designed primarily for use in motion in space. As sources of ions or plasma, they are also used for terrestrial applications, in particular for ion processing. Due to their high specific impulse (from 1500 to 6000 s), they provide satellites with significant mass gain in comparison with chemical jet engines.

Closed electron drift plasma engines are characterized by a low energy cost of thrust due to the creation of conditions favorable for ionization, while the ion flux created by them is quasineutral, which removes the limitations of the ion current density due to the action of the space charge. In this regard, such a plasma engine can operate in a wide range of accelerating voltages. The ion current in good models of plasma accelerators of this type is close to the discharge current and is determined only by the mass flow rate of the working fluid. Thus, in known plasma accelerators with a closed electron drift, in contrast to ion accelerators, it is possible to independently change the mass flow rate and accelerating voltage, i.e., thrust and flow rate at high engine efficiency.

In the article by L.A. Artsimovich et al. "Development of a stationary plasma engine and its testing on the Meteor satellite" (Space Research, Moscow, 1974, vol. XII, issue 3, pp. 451-468) describes the general principle of constructing a plasma engine ( accelerator) with a closed electron drift.It consists of a discharge chamber with an annular channel of ionization and acceleration with an open outlet made of an insulating material, a gas-discharge hollow cathode mounted on the side of the open outlet from the annular channel and connected to the negative pole of the source a constant voltage, connected to the positive pole of the voltage source, a hollow annular gas distribution anode mounted at the entrance to the annular channel, the plasma accelerator also contains means for supplying ionized gas to the gas-discharge hollow cathode and to the hollow annular gas distribution anode, which has openings for supplying gas to it and for supplying ionized gas to the discharge chamber.The accelerator includes a system for creating a magnetic field in the cavity of the discharge chamber, including ir magnetic field and a magnetic circuit consisting of a central core, an end part on the side opposite to the exit from the annular channel, and an annular part located outside the annular channel and forming the output end of the accelerator. The end parts of the magnetic circuit are fastened with the help of peripheral magnetic conductive rod elements uniformly located around the discharge chamber, coaxially with it. The magnetic field source of the known accelerator consists of eight in series connected and included in the electric circuit electromagnetic coils wound on rod magnetically conductive elements.

Known plasma accelerator with a closed electron drift containing a magnetic system with three pairs of magnetic poles (US 4703222, H05H 1/00, publ. 1987). The known plasma accelerator comprises a discharge chamber with an annular channel of ionization and acceleration made of an insulating material and having an open outlet, a hollow buffer chamber in communication with the entrance of the annular channel, a cathode located on the side of the open outlet of the channel, and a ring-shaped anode coaxially mounted at the entrance to channel of the discharge chamber. The annular gas distribution device is placed in the buffer chamber without blocking the entrance to the annular channel and is made with holes for supplying ionized gas to the buffer chamber in the radial direction. The magnetic system of a known plasma accelerator consists of magnetic field sources, a magnetic wire and three pairs of annular magnetic poles located respectively on the side of the external and on the side of the inner walls of the discharge chamber. The first pair of magnetic poles covers the annular channel from the side of its open exit and forms the end part of the accelerator. The magnetic core includes a central cylindrical core mounted coaxially with the channel of the discharge chamber together with internal magnetic poles and magnetic field sources that are located between the internal magnetic poles. External elements of the magnetic circuit connect the external magnetic poles. The remaining sources of the magnetic field are located around the outer wall of the annular channel between the outer magnetic poles.

This embodiment of the magnetic system allows you to create the optimal magnetic field configuration for ionization and ion acceleration, which ensures an increase in the gas efficiency of the accelerator and its overall efficiency. In addition, the use of preionization in the buffer chamber of the accelerator, along with an increase in the efficiency of use of the working fluid, provides for the regulation of the characteristics of the plasma accelerator over a wide range.

However, the advantages inherent in the solution do not exclude the disadvantages regarding, first of all, the divergence of the ion beam, insufficiently high efficiency, limited reliability, design complexity, sufficiently large weight and large dimensions of the plasma accelerator, which should be used as part of a space propulsion system.

Known stationary plasma engine of low power with closed electron drift, containing a discharge chamber with a ring-shaped channel of ionization and acceleration, made of electrical insulation material and having an open outlet, a hollow buffer chamber in communication with the entrance of the ring-shaped channel, the cathode located on the side of the open channel output, ring-shaped an anode coaxially mounted at the entrance to the channel of the discharge chamber, an annular gas distribution device located in the buffer chamber without overlapping the input and in an annular channel and made with holes for supplying ionized gas to the buffer chamber, and a magnetic system with magnetic field sources, a magnetic circuit and three pairs of annular magnetic poles located respectively on the side of the external and internal walls of the discharge chamber, while the first pair of magnetic the poles encompasses the annular channel from the side of its open exit and forms the end part of the accelerator, the core includes a central cylindrical core, installed coaxial to the channel of the discharge chamber together with the internal magnetic poles and the first magnetic field source located between the internal magnetic poles, and external elements connecting the external magnetic poles, and the second magnetic field source is located around the outer wall of the annular channel between the external magnetic poles, characterized in that the interpolar gap of the second pair of poles is closed by a ring non-magnetic element, which forms, together with the indicated poles, the end part of the accelerator from the buffer side the first chamber, the outer pole of the third pair of magnetic poles being installed between the buffer chamber and the outer pole of the first pair, the inner pole of the third pair is formed on the central core and opposite the buffer chamber with an offset relative to the plane of the outer pole of the same pair of poles towards the gas distributor, the first source of magnetic the poles are placed between the inner poles of the first and third pairs, and the second source of magnetic field is installed between the outer poles of the first and third pairs (RU 2139647, H05H 1/54, F03H 1/00, Publ. 10/10/1999). Adopted as a prototype.

In a known solution, the use of a buffer chamber made it possible to achieve uniformity of the flow of neutral particles entering the channel, and consequently, of ions. During the operation of the patented plasma accelerator, the required magnetic field topology close to ideal is achieved by a simple and effective constructive solution, due to which it is possible to use only two magnetic field sources to solve this problem. This was achieved by the optimal arrangement of the third pair of magnetic poles, which allows the most simple way to create convex magnetic lines of force at the walls of the channel of the discharge chamber in its output part. As a result of the experiments, it was found that the required magnetic field profile in the buffer chamber is organized by optimizing its size according to the ratios given in this patent. The slope of the separatrices and the convexity of the magnetic field lines is adjusted by the position of the external and internal magnetic poles of the third pair. Such a constructive implementation determines the creation of a magnetic field configuration close to ideal (for controlling the shape of the accelerated ion flux), while unnecessary sources of magnetic field are excluded from the energy-stressed zone of the internal magnetic circuit. These capabilities make it possible to simplify the design of a plasma accelerator, reduce its weight and dimensions, reduce the half-angle of divergence of the ion beam to <± 15, and increase the efficiency up to 65-72%.

Stationary plasma engines (SPDs) are widely used on board modern spacecraft. Currently, interest has grown significantly in low-power SPDs (less than 200 W) as in Russia (Hall and ion plasma engines for spacecraft // OA Gorshkov, VA Muravlev, AA Shagayda; ed. Academician of the Russian Academy of Sciences A.S. Koroteev.M .: Engineering, 2008, pp. 31-42, 184-189; K.N. Kozubsky, V.M. Murashko, Yu.P. Rylov and other SPDs work in space / / Plasma Physics, 2003, vol. 29, No. 3, pp. 277-292; G.E. Bugrov, A.V. Desyatskov, M.V. Kozintseva, A.S. Lipatov. Integral parameters of a stationary ATON small plasma engine power in stationary and "machine-gun" modes // osmonautics and rocket science, 2008, 3 (52), pp. 69-74; MB Belikov, OA Gorshkov, EN Dyshlyuk et al. Development of a low-power Hall engine with a resource of up to 3000 hours // Cosmonautics and rocket science, 2008, 3 (52), pp. 131-141; Bugrova AI, Desiatskov AV, Kaufman HR et al. "Design and experimental investigation of a small closed drift thruster", 27 ^th International Electronic Propulsion Conference, 2001. - IEPC-2001-344) and abroad (Polk J. "Electric propulsion in the USA", 30 ^th International Electronic Propulsion Conference, Florence, Italy, 2007, -IEPC-2007-368; Polzin KA, Markusie T.E., Stanoev BJ et al. "Performance of a low power cylindrical Holl thruster", 29 ^th International Electronic Propulsion Conference, 2005, -IEPC-2005-011; Biagioni L., Cesari U., Saverdi M., "Development status of the HT-100 miniaturized hall effect thruster system", 41 ^th Join Propulsion Conference, 2005, -AIAA-2005-3875; Tahara H., Fujioka T., Kitano T. et al., "Optimization on magnetic field and acceleration channel for low power hall thrusters", 28 ^th International Electronic Propulsion Conference, 2003, -IEPC-2003-015).

This is mainly due to the expansion of work on the creation of a new generation of small spacecraft that can be used to solve telecommunication and remote sensing tasks of the Earth. The functions that SPD performs on board the spacecraft are the correction of the orbits of spacecraft, keeping it in a given orbit, and maintaining the desired orientation of the spacecraft in space.

The creation of modern stationary low-power plasma engines goes both along the path of scaling the engines of the classical scheme, and based on the modification of their magnetic system. In the first case, the work is carried out in cooperation with OKB "Fakel" with the Research Center. M.V. Keldysh (Hall and ion plasma engines for spacecraft // O.A. Gorshkov, V.A. Muravlev, A.A. Shagayda; edited by the Academician of the Russian Academy of Sciences A.S. Koroteyev.- M .: Mechanical Engineering, 2008, p. 31-42, 184-189; MB Belikov, OA Gorshkov, EN Dyshlyuk et al. Development of a low-power Hall engine with a life of up to 3000 hours // Cosmonautics and Rocket Engineering, 2008, 3 (52 ), p. 131-141). In the second case, the work is carried out by the Fakel Design Bureau jointly with the Research Institute of Applied Mechanics and Electrodynamics (K.N. Kozubsky, V.M. Murashko, Yu.P. Rylov and other SPDs work in space // Plasma Physics, 2003, vol. 29, No. 3, pp. 277-292). Numerous experimental data in the above publications show that, with a decrease in the power consumed by the SPD, the anode traction efficiency classic SPD is reduced and at a power of 100-200 watts does not exceed 30.

When designing plasma engines consuming low power, the Moscow State Technical University MIREA is used as a scaling method based on the Melikov-Morozov criterion described in detail in publications (A.I. Bugrova, N.A. Maslennikov, A.I. Morozov. Similarity laws of integral characteristics in ultrasonic testing // ZhTF, 1991, volume 61, issue 6, pp. 45-51; A.I. Bugrova, A.V. Desyatskov, A.S. Lipatov, et al. Experimental Investigations of Stationary Plasma Engines of the ATON Family / / Plasma Physics, 2010, vol. 36, No. 4, pp. 395-400), as well as the patented magnetic field optimization method in 1999 (RU 2139647).

However, the direct use of the scaling method to obtain the current model, reduced in size relative to the analogue, does not provide the desired result.

According to estimates, with the power consumed by the SPD equal to 140-160 W, the consumption of xenon through the anode is ~ 0.7-0.9 mg / s. The discharge voltage should be about 170-200B. With these input parameters, a decrease in the efficiency of classic engines consuming low power compared to medium power SPDs (1-1.5 kW) from 50% to 30% can be explained as follows. From the above work it follows that the anode efficiency of the engine is associated with the efficiency of the ionization process, which is determined by the gas utilization coefficient and, by the voltage loss on the ionization of xenon atoms AU and the exchange parameter that determines the value of the discharge current. C.p.d. engine taking into account the power consumed by the magnetic coils is equal to:

- расход газа через анодWhere

- gas flow through the anode

The thrust developed by the engine is equal to

where M is the mass of the xenon ion, U _p is the discharge voltage, the gas utilization coefficient is defined as the ratio of the ion current exiting the channel to the mass current:

Discharge power:

NP-I _p U _p , (4)

Where

- массовый ток.

- mass current.

N _k - power consumed by the magnetization coils:

N _k = I _B U _B + I _H U _H , (6)

where I _B , I _H are the currents in the inner and outer coils, U _B , U _H are the voltages supplied to the coils.

Anode specific impulse of thrust is determined by the formula:

where g is the acceleration of gravity. An important characteristic for any SPD is the thrust price, which is defined as: Ct = N _Σ / F, (8)

where N _Σ = Np + Nk is the total power consumed by the engine. Ct determines the power spent on 1 mN thrust.

µ, ΔU and ξ depend on one similarity parameter β, which, in turn, depends on the flow rate and the radial dimensions of the accelerator discharge channel [10]:

where D _H is the inner diameter of the outer channel, in is the width of the channel.

It has been experimentally established (A.I. Bugrova, N.A. Maslennikov, A.I. Morozov. The laws of similarity of integral characteristics in ultrasonic testing // Zh.T. Fiz., 1991, Volume 61, Issue 6, pp. 45-51) that if β approaches 2 * 10 ^-2 mg / s * mm, then the values of μ and ξ tend to unity, ΔU to the ionization price, which for xenon is ~ 50 B, which is equal to about four times the ionization potential of the xenon atom. At the same time, the efficiency of SPD is maximum. It is impossible to obtain such a large β value for low power models. Even for a flow rate of 0.8 mg / s, b = 8 mm and D _H = 26 mm, we obtain β = 1.4 * 10 ^-2 mg / s * mm. This magnitude of the similarity parameter is sufficient for the effective operation of the engine (A.I. Bugrova, A.V. Desyatskov, A.S. Lipatov, etc. Experimental studies of stationary plasma engines of the ATON family // Plasma Physics, 2010, v. 36, No. 4 , p. 395-400).

However, it is impossible to realize a design with such a small diameter of the discharge chamber using traditional materials. Indeed, for the effective operation of an engine of any size, it is necessary that the shear value of the radial component of the magnetic field be ~ 0.02 T. To create such a field, at least two magnetization coils are needed - internal and external. These coils are powered from autonomous sources, since the currents in them must be much larger than the discharge current to obtain the required magnetic field, and the power consumed by the magnetizing coils makes a significant contribution to the total power N _Σ = Np + Nk consumed by the SPD. The inner coil is wound around the core. Experiments show that the minimum core radius at which there is no iron saturation is ~ 3 mm. With a four-layer winding of the internal coil with a POG wire with a core diameter of 1 mm, a winding height of 5 mm is required. In addition to the indicated dimensions, to ensure a life of 2500 hours using BGP-10 ceramics, the wall thickness of the internal insulator should be at least 3 mm. Thus, the minimum diameter of the discharge chamber with a channel width of 8 mm is D _H = 38 mm. Moreover, the criterion coefficient for the flow rate of 0.8 mg / s is equal to β = 0.008 mg / s • mm. This value is less than necessary and this explains the decrease in efficiency low power engines. The above formulas and comments on them apply both to classical LDS and to a new generation LDS. However, in SPD of a new generation of ATON type (A.I. Bugrova, A.V. Desyatskov, A.S. Lipatov, etc. Experimental studies of stationary plasma engines of the ATON family // Plasma Physics, 2010, v. 36, No. 4, p. . 395-400) it is possible to effectively form the optimal configuration of the magnetic field lines inside the channel. This is mainly due to the lack of magnetic screens, which are characteristic of classical SPDs.

The present invention is aimed at achieving a technical result, which consists in increasing the traction characteristics of low power SPD operating on xenon, and simplifying the design while ensuring guaranteed continuous operation time.

The specified technical result is achieved in that in a stationary low-power plasma engine containing a discharge chamber with an annular channel of ionization and acceleration, made of electrical insulation material and having an open outlet, a hollow buffer chamber in communication with the entrance of the annular chamber, a cathode located on the side of the open outlet channel and communicated with the line for supplying ionized gas, an annular anode coaxially mounted to the channel of the discharge chamber, an annular gas distribution device a property placed in the buffer chamber without blocking the entrance to the annular channel and made with holes for supplying ionized gas to the buffer chamber, and a magnetic system of two ring-shaped magnetic devices with magnetic field sources located respectively on the side of the external and internal sides of the discharge chamber for creating a magnetic field in the main channel, ensure the presence in this channel of a radially directed magnetic field with a certain gradient to obtain maximum induction in during the main channel, the annular anode concentric to the annular channel of ionization and acceleration is located at a distance from its open end, in the input part of the main channel, an annular buffer chamber is placed beyond the anode zone, the size of which in the radial direction exceeds the radial size of the annular channel of ionization and acceleration, gas ducts for supplying ionized gas are communicated towards the anode through an annular distributor with a zone different from the zone of the anode, and from the rear A ring made of non-magnetic stainless steel is fixed to form a symmetric configuration of the magnetic field lines using two sources of the magnetic field of the ring-shaped magnetic devices of the magnetic system spaced in the transverse direction relative to the discharge chamber.

These features are significant and are interconnected with the formation of a stable set of essential features sufficient to obtain the desired technical result.

The present invention - the model is illustrated by a specific example of execution, which, however, is not the only possible, but clearly demonstrates the possibility of achieving the desired technical result.

Figure 1 - design of a plasma engine with a closed electron drift;

figure 2 - shows the configuration of the lines of force of the SPD model;

figure 3 - shows the current-voltage characteristics of the discharge from the discharge voltage for the three xenon flow rates of 0.7 mg / s, 0.8 mg / s and 0.9 mg / s;

figure 4 - shows the dependence of thrust on the discharge voltage for the three xenon flow rates of 0.7 mg / s, 0.8 mg / s and 0.9 mg / s;

figure 5 - shows the dependence of the anode specific impulse on the discharge voltage for three xenon flow rates of 0.7 mg / s, 0.8 mg / s and 0.9 mg / s;

6 - shows the dependence of the traction efficiency from discharge voltage for three xenon flow rates, 0.7 mg / s, 0.8 mg / s and 0.9 mg / s;

Fig.7 - shows the dependence of the efficiency from the total power N _Σ for the three xenon flow rates, 0.7 mg / s, 0.8 mg / s and 0.9 mg / s;

Fig. 8 shows the dependence of the specific impulse R _beats on the total power N _Σ for three xenon flow rates of 0.7 mg / s, 0.8 mg / s and 0.9 mg / s;

Fig.9 - shows the experimental dependence of the discharge current consumed by the SPD;

figure 10 - shows the experimental dependence of the total power;

11 - shows the experimental dependence of the ratio of the power consumed by the magnetization coils to the discharge power;

Fig - shows the experimental dependence of the exchange parameter on the current in the magnetization coils;

Fig - shows the dependence of the specific anode impulse of the thrust on the currents in the magnetization coils;

Fig.14 shows the dependence of the efficiency from currents in magnetization coils;

Fig - shows a graph of changes in the level of fluctuations of the discharge current;

Fig - shows a graph of the change in the price of thrust;

) и частиц гибнущих на стенках (

) от тока в катушках намагничивания. ♦-

▪

, ▲

,

Fig - shows the dependence of the ion flux of the first, second multiplicity (

) and particles perishing on the walls (

) from the current in the magnetizing coils. ♦ -

▪

, ▲

,

According to the present invention, the design of a closed electron drift plasma engine is contemplated. This engine contains a main annular channel of ionization and acceleration, limited by structural elements of insulating material and open at its output end. At least one hollow cathode is in communication with an ionizable gas supply line. A ring anode concentric to the main channel is located at a distance from its open end. In the input part of the main channel, behind the anode location zone, an annular buffer chamber is placed, the size of which in the radial direction exceeds the radial size of the main annular channel. Pipes for supplying ionized gas communicate in the direction of the anode through an annular distributor with a zone different from the zone of the anode. Means for creating a magnetic field in the main channel ensure the presence in this channel of a radially directed magnetic field with a certain gradient to obtain maximum induction at the output of the main channel.

Patented SPD contains (Fig. 1) a discharge chamber 1 made of an insulating (electrical insulating) material (BGP-10) with a main annular channel of ionization and acceleration 2 having an open outlet 3. A cavity of the buffer chamber is connected to the annular duct 2 from the side of its entrance made also of insulating material (electrical insulation - BGP-10). In this example, the buffer chamber is made in the discharge chamber and forms the structural part of the latter. On the side of the closed part of the annular channel 2, at least one hollow anode is installed, connected to the line for supplying ionized gas (non-magnetic gas inlet pipe 4 (steel 12X18H10T), fixed by means of an insulating sleeve 5 (БГП-10) in the wall supporting non-magnetic studs 6 ( steel 12X18H10T) for attaching the SPD to the support).

Ring anode 7 is made in the form of a sleeve (steel 12X18H10T). Moreover, the anode 7 is located at a distance from its open end. The annular anode 7 is pressed (in contact) through the presser foot 9 with the surface of the annular chamber 10 of non-magnetic material (steel 12X18H10T) having openings for the injection of a gas agent (for example, xenon gas) coming from the gas inlet tube 4 into and out of the cavity of the annular chamber 10 in the channel 2. The annular anode 7 is installed using the rigid tabs 9 of the clamp to the body of the annular chamber 10. The implementation of the clamping tabs 9 of electrically conductive material provides electrical connection of the anode with the power line from the positive floor usa constant voltage source.

The cathode and anode 7 are respectively connected to the negative and positive poles of a constant voltage source, forming a power circuit. The annular chamber 10 is located in the cavity of the buffer chamber and is an annular gas distribution device without blocking the entrance to the annular channel 2. The ionized gas is supplied to the hollow cathode and gas distribution device 7 from separate or from a common source of compressed gas. An inert gas is used as a working ionized gas, in this case xenon (Xe). In the annular gas distribution device (chamber 10), an opening is made for supplying ionized gas into it by means of a gas supply pipe 4. Ionized gas is supplied to the buffer chamber through openings in the chamber 10, which are oriented perpendicular to the axis of symmetry of the discharge chamber 1, around a circle of maximum diameter. The holes for the supply of ionized gas into the buffer chamber, radially directed, contributes to the creation of a uniform density of the working gas zone, occupying almost the entire volume of the buffer chamber.

An annular buffer chamber is located in the input part of the main channel beyond the anode location zone; the size of the annular buffer chamber in the radial direction exceeds the radial size of the main annular channel 2.

The magnetic field in the cavities of the buffer and discharge chambers is created using a magnetic system of two magnetic devices. The first magnetic device includes a central cylindrical core 11 of St3-10, with sources of a magnetic field 12 (inner coil) and magnetic poles 13. The second magnetic device includes a housing 14 of St3-10 L-shaped, inside which is installed an annular support 15, on the sides of which are two disk stops 16 of non-magnetic material (steel 12X18H10T). Thus, an annular cavity is formed for the source of magnetic field 17 (outer coil). The entire assembly is strengthened by a support disk 18 carrying the connecting elements of the magnetic core elements 19 of St3-10. The second magnetic device is made in the form of an annular assembly, which is worn on the discharge chamber 1 from the side of the open exit 3. By means of the magnetic core elements 19, the magnetic system is fastened. The outer rod elements 19 are uniformly located around the chamber 10 and channel 2 around the circumference and fasten the end parts of the plasma accelerator.

The design of the SPD magnetic system allows you to create, by selecting the internal diameters of the magnetic poles and the relative positions of the poles, the desired magnetic field configuration, which is characterized by a given field gradient (at least 100 E / cm) from zero in the anode region to the maximum value at the exit of the annular channel 2 and an angle between the branches of the separatrices of the field lines of the field, equal to about 90 °, and the separatrices intersect the walls of the channel 2 at an angle of about 45 °. This configuration of the magnetic field ensures the creation of the ion-focusing geometry of magnetic lines of force in the output part of the channel 2 and a positive gradient of the magnetic field from the anode to the exit from the channel. Moreover, a magnetic field is created near the anode with the separatrix direction at an angle of 45 °, which provides conditions for the separation of the ion flow from the channel walls and its focusing on the middle surface of the discharge chamber.

Modeling of the magnetic field was carried out according to a standard computer program using tabular characteristics of the magnetic materials of the engine. The position of the poles of the magnetic circuit, the current density in the inner and outer magnetization coils, the thickness of the poles, as well as the position and size of the magnetic “hole” in the rear flange of the model, the presence of which is necessary for new generation models of the α type (RU 2139647), were determined. As a result, the configuration of the magnetic field lines of the model was obtained, shown in figure 2, in which the following numbers indicate the following SPD elements: 20 - buffer volume, 21 - front flange, 22 - rear flange, 23 - magnetic "hole", 24 - outer coil, 25 - inner coil, 26 - hairpin. This figure corresponds to the current densities in the inner coil j _KB = 2.4 MA / m ² and the outer j _KH = 0.9 MA / m ² . At the same time, r is the field component at the cut of the model along the channel’s midline B _r = 0.0182 T, and at a distance of 10 mm from the cut into the channel B _r = 0.0092 T, that is, the field gradient at the cut along the canal midline is 0.009 T / cm These values are close to optimal.

The magnetic "hole" is a ring 27 (figure 1) of non-magnetic stainless steel inserted into the rear flange of the model. It is needed to form a symmetric configuration of the magnetic field lines using only two magnetization coils. As can be seen from figure 2, the model implements a "curly" magnetic circuit, allowing to reduce its dimensions.

With equipotentialization of the magnetic field lines, we can assume that the ion flux moves almost perpendicular to the tangent lines to them. From the symmetry of the pattern of the lines of force depicted in figure 2 it follows that the ion flux in the channel of the accelerator will be symmetrical. Unlike classical SPDs, there is a separatrix of magnetic field lines. The zero position of the magnetic field coincides with the point of intersection of the branches of the separatrix. The anode is located opposite the zero of the magnetic field and is mounted on an external insulator. Thus, the shape of the magnetic field lines is focusing for the ion flux, and the jet at the exit from the model is torn off from the walls of the insulators. All this should lead to an increase in efficiency. anode block SPD.

As a result of the optimization, a laboratory model of SPD was designed and manufactured (Fig. 1). Overall dimensions of the model: diameter ~ 70 mm, length ~ 60 mm. The model was tested both at the stand of MSTU MIREA, and at the stand of the Fakel Design Bureau. The experimentally measured integral parameters obtained at both stands practically coincided.

The integral characteristics of the laboratory model of SPDs were measured on stands whose vacuum chambers were pumped out by diffusion pumps. The xenon consumption in the experiments ranged from 0.7 mg / s to 0.9 mg / s. In this case, the dynamic pressure did not exceed 1 * 10 ^-4 mm Hg. by air. The total power consumed by the model, including the power spent on the magnetization coils, varied in the range from 125 W to 200 W.

0,8 мг/с и 0,9 мг/с измерялись вольтамперные характеристики разряда и тяга, создаваемая ускорителем. Токи в катушках намагничивания подбирались по минимуму разрядного тока. Оказалось, что для всех расходов оптимальные токи во внутренней и наружной катушках равны I_B=I_H=5A. По формулам (1-7) рассчитывался анодный к.п.д. с учетом суммарной потребляемой мощности анодного блока N_Σ=Np+Nk и удельный импульс тяги. На фиг.3-6 приведены вольтамперные характеристики разряда (фиг.3), зависимость тяги (фиг.4), анодного удельного импульса (фиг.5) и тягового к.п.д. (фиг.6) от разрядного напряжения для трех указанных расходов. Из фиг.3 видно, что вольтамперные характеристики разряда для всех расходов практически вертикальны, что характеризует хорошую степень ионизации атомов ксенона. Тяга и удельный импульс (фиг.4 и 5) растут с ростом напряжения разряда по линейному закону. Максимальные значения тяги, полученные при U_P=210B равны 9,4 мН, 10,6 мН и 12,5 мН для расходов 0,7 мг/с, 0,8 мг/с и 0,9 мг/с соответственно. Удельный импульс при этом напряжении равен 1370с, 1380с и 1410с и тяговый анодный к.п.д достигает величины 43,8% при расходе 0,9 мг/с. Однако мощность, потребляемая ускорителем при этом расходе превышает 150 Вт. Это видно из фиг.7 и 8, где для этих режимов изображены кривые зависимости к.п.д. и удельного импульса Р_уд от суммарной мощности N_Σ. Из этого чертежа видно, что при расходе ксенона

и напряжении 210B суммарная мощность не превышает 150Вт, при этом к.п.д. равен 41%, удельный импульс достигает значения Р_уд=1370с, тяга равна 9,4 мН. Другим режимом с мощностью N_Σ=150Вт является режим с расходом 0,8 мг/с, к.п.д. 39%, Р_уд=1240с, F=9,7мН, U_P=190B.For three xenon costs

0.8 mg / s and 0.9 mg / s measured the current-voltage characteristics of the discharge and the thrust generated by the accelerator. The currents in the magnetization coils were selected to minimize the discharge current. It turned out that for all costs, the optimal currents in the inner and outer coils are equal to I _B = I _H = 5A. According to formulas (1-7), the anode efficiency was calculated taking into account the total power consumption of the anode block N _Σ = Np + Nk and specific impulse of thrust. Figure 3-6 shows the current-voltage characteristics of the discharge (figure 3), the dependence of the thrust (figure 4), the anode specific impulse (figure 5) and traction efficiency (6) from the discharge voltage for the three indicated costs. Figure 3 shows that the current-voltage characteristics of the discharge for all flows are almost vertical, which characterizes a good degree of ionization of xenon atoms. The thrust and specific impulse (Figs. 4 and 5) increase with increasing discharge voltage according to a linear law. The maximum thrust values obtained at U _P = 210B are 9.4 mN, 10.6 mN and 12.5 mN for flow rates of 0.7 mg / s, 0.8 mg / s and 0.9 mg / s, respectively. The specific impulse at this voltage is 1370s, 1380s and 1410s and the traction anode efficiency reaches 43.8% at a flow rate of 0.9 mg / s. However, the power consumed by the accelerator at this flow rate exceeds 150 watts. This can be seen from Figs. 7 and 8, where the efficiency curves are shown for these modes. and specific impulse P _beats from the total power N _Σ . From this drawing it can be seen that with xenon consumption

and a voltage of 210V, the total power does not exceed 150W, while the efficiency is equal to 41%, the specific impulse reaches a value of P _beats = 1370 s, thrust is 9.4 mN. Another mode with a power of N _Σ = 150 W is a mode with a flow rate of 0.8 mg / s, efficiency 39%, P _ud = 1240s, F = 9,7mN, U _P = 190B.

, U_p=180В. Для этого изменялись токи в катушках намагничивания от 3A до 5A с шагом 0.25A, причем как во внутренней, так и в наружной катушках токи были одинаковы, поэтому конфигурация силовых линий не менялась.The effect of the magnetic field on the integral parameters of the SPD at the input parameters was verified

, U _p = 180V. For this, the currents in the magnetization coils changed from 3A to 5A with a step of 0.25A, and the currents in both the internal and external coils were the same, so the configuration of the field lines did not change.

Fig. 9-12 shows the experimental dependence of the discharge current (Fig. 9), the total power consumed by the SPD (Fig. 10), the ratio of the power consumed by the magnetizing coils to the discharge power (Fig. 11) and the exchange parameter (Fig. 12) from the current in the magnetizing coils. It can be seen from the figures that with an increase in the magnetic field, the discharge current and, accordingly, the total power consumed by the SPD, first sharply fall, and then go to the "shelf". The relative fraction of power consumed by the magnetization coils grows almost linearly (Fig. 11). The exchange parameter asymptotically decreases to a value of 1.23 (Fig. 12).

At each experimental point, thrust was measured and the dependences of the specific anode impulse of thrust and efficiency were calculated. from currents in magnetization coils. These curves are presented in FIGS. 13 and 14. It is noteworthy that the thrust and, accordingly, the specific impulse in the indicated range of the magnetic field change insignificantly (Fig. 13). On Fig η _a - anode efficiency excluding losses in the magnetization coils, η _aΣ - efficiency anode block taking into account these losses. From Fig. 14 it is seen that η _aΣ first increases sharply, reaching a maximum, and then slightly decreases, while η _a monotonously increases and goes to the "shelf". Therefore, the decrease in the efficiency of the η _aΣ model can be explained by an increase in the heating of the magnetization coils when a larger current is passed through them. On Fig shows how the level of fluctuations of the discharge current, and in Fig.16 - the price of traction. It can be seen that the level of oscillations decreases with increasing current in the coils from 4.5% to 2.5%. The price of traction also decreases from 18 W / mN to 16 W / mN. From Fig.13-16, it follows that with increasing currents in the magnetic coils to the optimum values (minimum discharge current), the efficiency of the engine in the main parameters increases.

The behavior of integral parameters with an increase in current in magnetic coils, and therefore with an increase in the magnetic field in the ionization zone, can be explained on the basis of the following considerations. The plasma stream emerging from the SPD is a completely ionized medium consisting of xenon ions of the first and second magnitude and particles that have fallen from acceleration. The share of the latter can be associated with various reasons: the passage without ionization in the accelerator, the death of ions on the walls and their transformation into neutrals. According to (A.I. Bugrova, A.S. Lipatov, A.I. Morozov, S.V. Baranov. The effect of the ratio of the fractions of ions of different multiplicity on the integral parameters of the SPD type ATON // Letters to Zh. Phys., Volume 31, issue 21 , 2005, pp. 87-94) these flows are associated with integral parameters by the relations:

- суммарный расход ксенона,

и

- поток однократно и двукратно ионизованных атомов,

- поток частиц, гибнущих на стенках, k - коэффициент, определяющий вклад сквозного тока в ток разряда (к≈0,1). На фиг.17 приведены зависимости

, от тока в катушках намагничивания (I_В=I_Н), который меняется в пределах от 3A до 5A. Из чертежа видно, что при увеличении тока в катушках доля однократно ионизованных ионов возрастает от 31% до 64%, а доля ионов второй кратности убывает от 39% до 15%. Кроме того, уменьшается доля частиц, гибнущих на стенках разрядной камеры. Уменьшение доли двухзарядных ионов и частиц, гибнущих на стенках, приводит к увеличению к.п.д. (В. Ким, В.И. Козлов, В.М. Мурашко и др. Исследование особенностей работы стационарных плазменных двигателей при повышенных разрядных напряжениях //Космонавтика и ракетостроение, 2008, 3(52), сс. 21-27) и незначительному уменьшению удельного импульса. Это связанно с тем, что при уменьшении количества ионов второй кратности снижается средняя скорость истечения струи, а значит, уменьшается удельный импульс. При этом уменьшаются потери на ионизацию.Where

- total xenon consumption,

and

- a stream of once and twice ionized atoms,

is the flux of particles perishing on the walls, k is the coefficient determining the contribution of the through current to the discharge current (k≈0.1). On Fig shows the dependence

, from the current in the magnetization coils (I _B = I _N ), which varies from 3A to 5A. From the drawing it can be seen that with increasing current in the coils, the fraction of singly ionized ions increases from 31% to 64%, and the fraction of ions of the second magnitude decreases from 39% to 15%. In addition, the proportion of particles dying on the walls of the discharge chamber is reduced. A decrease in the fraction of doubly charged ions and particles perishing on the walls leads to an increase in the efficiency (V. Kim, V.I. Kozlov, V.M. Murashko et al. Study of the features of stationary plasma engines at high discharge voltages // Cosmonautics and Rocket Engineering, 2008, 3 (52), pp. 21-27) and insignificant decrease in specific impulse. This is due to the fact that with a decrease in the number of ions of the second magnitude, the average jet velocity decreases, and, therefore, the specific impulse decreases. At the same time, ionization losses are reduced.

An important parameter of the SPD is the divergence of the jet flowing out of the engine, which is determined by the solid angle at which 90% of the directed ion flow enters. For the classical models M-70 and SPD-100, the half-angle of divergence is ± 45 ° (K.N. Kozubsky, V.M. Murashko, Yu.P. Rylov and other SPDs work in space // Plasma Physics, 2003, vol. 29, No. 3, pp. 277-292).

To determine the divergence of the α-40 model, the profiles of the directed ion current to the double probe were taken. As a result of processing these curves, a divergence half angle of ± 25 ° was obtained, which is substantially less than that of classical models. The decrease in the divergence of the jet in the SPD is explained by the shift of the "center of gravity" of the ionization zone inland. This is realized using a buffer volume, where neutral atoms are isotropized, and creating a focusing geometry of the magnetic field lines in the channel. It should be noted that as the angle of divergence of the jet decreases, the width of the erosion belts increases both on the outer and inner channels of the discharge chamber. This means that perhaps the divergence of the jet affects the engine resource.

при вкладываемой мощности N_Σ≈150Вт в течение 50 часов.According to the established criteria, the resource is determined by the time of continuous operation of the engine, at which the thickness of the insulators in the section becomes zero. To calculate the wall thickness of the insulator for this resource, it is necessary to determine the erosion rate at the cut in the radial direction. Short-term life tests of the SPD operating in the U _p = 210B mode were carried out.

with a power input of N _Σ ≈150 W for 50 hours.

The experiments showed that the average erosion rate at the LDS section for the inner wall was 3 μm / hour, the external - 2.25 μm / hour. According to these data, using a logarithmic approximation, it was found that for a resource of 2500 hours, the thickness of the internal ceramics should be 2.9 mm, the outer - 2.2 mm.

Comparative characteristics of low power SPD developed by different organizations are given in the table.

Table Parameter Model (developer) SPD-50M "Keldysh Center" SPD of the present invention XNT 100 NO Europe Discharge voltage, B 200 210 160 Discharge current, A 0.72 0.63 one Power, W 147.5 147 160 Thrust, mN 9,4 9,4 10 Anode specific impulse of thrust, s 1090 1370 950 Anode efficiency,% 34.2 41,4 31,2 Resource of the discharge chamber, hour > 1800 2500 * - * - predicted resource.

The table shows that the SPD model of the present invention has several advantages compared to similar SPDs developed both in the Russian Federation and abroad. So, with a power input of ~ 150 W, a discharge voltage of 210 V, a xenon flow rate of 0.7 mg / s, the thrust was 9.4 mN, the anode specific impulse of thrust was ~ 1370 s, the anode efficiency taking into account the power consumed by the magnetizing coils, equal to 41%. Another mode with a higher thrust (9.7 mN), but with a lower specific impulse (1240 s) at the same power input, was obtained at a flow rate of 0.8 mg / s and a voltage of 190 V. amounted to 39%. In this mode, the level of oscillations of the discharge current is 2.5%. For a power of 140 W, the influence of the magnetic field on the integral parameters of the model was studied. It is shown that the integral characteristics are determined by the ratio of the fractions of singly and doubly charged ions of xenon atoms, which depends not only on the configuration of the lines of force, but also on its magnitude. The angle of divergence of the jet is ± 25 °. The predicted resource is 2500 hours. The data presented in the work show that the effectiveness of SPD is higher than that of the known analogues.

Such a plasma engine with a closed electron drift according to the patented invention can be used, first of all, in space technology as an actuator of an electric propulsion system. In addition, a plasma accelerator can be used in scientific research to simulate directed plasma flows.

Claims (1)

A stationary low-power plasma engine containing a discharge chamber with an annular channel of ionization and acceleration made of an insulating material and having an open outlet, a hollow buffer chamber in communication with the inlet of the annular chamber, a cathode located on the side of the open outlet of the channel and communicated with the line for supplying the ionizable gas, an annular anode coaxially mounted to the channel of the discharge chamber, an annular gas distribution device located in the buffer chamber without overlapping yes into an annular channel and made with holes for supplying ionized gas to the buffer chamber, and a magnetic system of two annular magnetic devices with magnetic field sources located respectively from the outer and from the inner walls of the discharge chamber to create a magnetic field in the main channel, providing the presence in this channel of a radially directed magnetic field with a certain gradient to obtain maximum induction at the output of the main channel, characterized in that the ring the anode concentric to the annular channel of ionization and acceleration is located at a distance from its open end; in the input part of the main channel, an annular buffer chamber is placed beyond the anode zone; its size in the radial direction exceeds the radial size of the annular channel of ionization and acceleration, gas inlets for supplying ionized gas communicated towards the anode through an annular distributor with a zone different from the zone of the anode location, while a ring of nonmagnet is fixed from the side of the rear flange stainless steel for forming a symmetrical configuration of the magnetic field lines using two annular magnetic devices of the magnetic system spaced in the transverse direction relative to the discharge chamber of the magnetic field.

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