RU2392589C2 - Method for definition of flow rate of system for supply of working medium to plasma source - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to measurement equipment used mainly under space vacuum conditions and intended for definition of flow rate of working medium (xenon) supplied from spacecraft jet engine tanks. One measures operating pressure P_in(t) in the inlet main of the plasma source 1 (propulsion module/PM/ including a stationary plasma engine), defines the transfer characteristic of the thermothrottle 10 of the execution unit 5 of the stabilisation system 4 of the discharge current I_p of the plasma source regulating supply of working medium to the plasma source providing for nominal conditions of operation, with I_p=f(I_tt), where I_tt - thermothrottle current. In the course of the plasma source operation one measures the current value of the inlet main operating pressure and thermothrottle current. By dependence

one defines the current value of weight flow

of working medium per unit of time.

EFFECT: invention improves flow rate definition precision.

2 dwg

Description

The invention relates to measuring equipment, operated mainly in space vacuum, designed to determine the flow rate of the working fluid from the tanks of jet propulsion systems of spacecraft (SC).

A known method for determining the flow rate of the working fluid according to the results of measuring pressure and temperature in tanks of known volume [1], relating to indirect methods. In the general case, when the working fluid is stored in tanks in a single-phase gaseous state, there is a certain dependence of pressure on mass at various temperatures. As the flow of the working fluid and the current change in pressure and temperature determine the amount of residue. The initial charge and residues determine the flow rate of the working fluid.

The disadvantage of this method is that for its use it is necessary to translate the entire working fluid into a gaseous state corresponding to the region of operating temperatures and pressures. For a given volume in a gaseous state, only a limited mass of the working fluid can be stored [1]. Therefore, it is stored in a liquid state and is transferred to a gaseous state by means of special devices (heat exchangers-gasifiers) before flowing through jet engines. Thus, at the initial stages of the operation of jet engines, it is impossible to determine the amount of the remaining working fluid and from it the flow rate from an isolated volume, taking into account the initial filling. And only after the residues make up a certain part of the initial charge of the working fluid (see Fig. 4 in [1]), according to the dependences of the pressure of the gaseous working fluid in an isolated volume on the mass at various gas temperatures, its current residues can be determined for subsequent determination expense.

A known method for determining the tightness of the isolated volume of the supply system of the working fluid with a plasma source, mainly in a vacuum, the technical essence of the closest match with the invention, selected as a prototype [2]. The method includes measuring the pressure in the supply system of the working fluid, consisting of an isolated volume, pipelines and valves of the supply system (see FIG. 1 in [2]), measuring the operating parameters of the plasma source, determining from the measured values of the plasma source the flow rate of the working fluid.

The disadvantage of this method is that only the characteristics of the plasma source are taken into account for determining the flow rate of the working fluid, and the characteristics of the thermo-throttle actuator of the plasma source stabilization system regulating the flow of the working fluid per unit time to the plasma source are not taken into account. In addition, the operating pressures in the input line of the plasma source are also not taken into account. The flow rate of the working fluid through the plasma source directly depends on the transfer characteristics between the discharge current of the plasma source and the current of the thermal reactor obtained for different pressures in the input line of the plasma source.

The main disadvantage of the prototype method is the reduced accuracy of determining the flow rate of the working fluid per unit time from the supply system of the working fluid to the plasma source. This is due to the fact that the real values of the current of the thermal reactor and the pressure of the working fluid at the entrance to the plasma source are not taken into account.

The technical result in a newly developed method for determining the flow rate of the supply system of the working fluid to the plasma source is to increase the accuracy of determining the flow rate by using the transfer characteristic of the thermal reactor of the actuator of the plasma source stabilization system, defined for various values of the working pressure in the input line of the plasma source.

The above technical result is achieved by the fact that in the method for determining the flow rate of the supply system of the working fluid to the plasma source, which includes measuring the pressure in the supply system of the working fluid, measuring the operating parameters of the plasma source, determining from the measured values of the plasma source the flow rate of the working fluid, measure the working pressure in the input line a plasma source, measure the operating parameters of the plasma source for various values of the measured working pressure in the input line, determine the transfer hara the characteristic of the thermal reactor of the executive device of the stabilization system of the plasma source, which regulates the flow rate of the working fluid per unit time to the plasma source, ensuring the nominal mode of its operation, measure the current pressure values in the input line and the current of the thermo throttle, then determine the value by the dependence of the flow on the measured pressure and current of the thermo throttle the current flow rate of the working fluid per unit time, and according to certain current values of the flow rate of the working fluid per unit time at a fixed int vomited operation of the source define the working fluid flow of the working fluid supply system.

For example, a traction module (TM) was selected as a plasma source, which includes a stationary plasma engine (SPD) and a gas distribution unit (BGR) [1], for which xenon is the working fluid.

To explain the technical essence of the invention are given:

figure 1 is a schematic block diagram of stabilization in TM discharge current (I _p ) by the current of the thermal reactor (I _td );

figure 2 is an example of the tuning characteristics of one of the thermal reactors.

The following conventions are introduced:

1 - TM (highlighted by a dash-dot line);

2 - anode-cathode block (battery) SPD (highlighted by a dashed line);

3 - BGR (highlighted by a dashed line);

4 - block automatic control TM (BARTM) (highlighted by a dashed line);

5 - magnetic regulator (MR);

6 - anode current sensor (DTA);

7 - electropneumatic valves for supplying xenon to ТМ (ЭПК ТМ);

8 - electro-pneumatic valves for supplying xenon to the anode (EPKA);

9 - electro-pneumatic valves for supplying xenon to the cathode (EPKK);

10 - thermal throttle (TD);

11 - nozzles for supplying xenon to the anode (JA);

12 - nozzles for supplying xenon to the cathode (LC);

13 - anode (A);

14, 15 - cathodes: first (K), second (K2);

F - traction force TM;

U _p is the discharge voltage;

m _A is the mass flow rate of xenon through the anode per unit time;

m _to - mass flow of xenon through the cathode per unit time;

I _p is the discharge current;

I _td - current of the thermal reactor;

R _I - pressure at the entrance to the TM.

At the same time, TM 1 contains battery SPD 2 and BGR 3. BARTM 4 contains MP 5 and DTA 6. The inputs of the EP 1 TM 7 BGR 3 are connected to the input lines of the TM 1, and the outputs of the EP 7 TM 7 are connected to the TD 10. The outputs of the TD 10 are connected through ZhA 11 and LCD 12 to the inputs of EPKA 8 and EPKA 9, respectively. The outputs of the EPKA 8 are connected to the anode A. Each of the outputs of the EPKA 9 is connected to the first K1 14 and the second K2 15 cathodes.

The anode with its electrical part is connected to the inputs of the DTA 6, the outputs of which are connected to the first inputs of MP 5. And to the second input of MP 5, settings are made to maintain the discharge current of 2.23 A from external current regulators. The output of MP 5 is connected to the electrical part of the TD 10.

To create a long and continuous traction F in TM 1 using battery 2 SPD, at the inlet of the BGR 3, gaseous xenon is maintained at a nominal pressure of 1.75 atm. In this case, the discharge voltage U _p = 300 V in the battery 2 is supported by means of stabilization of the plasma discharge BARTM 4. After the TM reaches the rated thrust mode (~ 4 g), BARTM 4 keeps its stability from the influence of destabilizing factors, such as:

- instability of the plasma discharge, manifested, in particular, due to low-frequency fluctuations of the average value of the discharge current ± 0.1 A;

- instability of inlet pressure ± 0.1 atm .;

- instability of discharge voltage ± 15 V;

- abnormal inrush currents of the discharge.

To solve these problems, several means are used in BARTM 4, including the stabilization system of the discharge current by the current of the thermal reactor, which implements the linear dependence I _p = f (I _td ). This task is implemented in hardware in the MP 5 BARTM 4 device, the current value I _p is supplied to one input of which from the DTA 6 sensor, and the precision current setting corresponding to the discharge current I _p = 2.23 ± 0.1 is supplied to the other input BUT.

Xenon is supplied to the TM by opening the EPA TM 7. Then, through EPKA 8 and EPKK 9, xenon is fed into the plasma discharge zone [1]. In this case, the TM contains one anode A 13, with which one of the two cathodes K1 14 or K2 15 works.

The executive device of the stabilization system I _p = f (I _td ) is TD 10 installed in BGR 3 TM 1, the operation of which is based on the principle of changing the xenon flow rate in the capillary tube through which it flows, due to its heating by the current supplied from MP 5 . This changes the viscosity of xenon and, thereby, regulates its supply. The flow characteristics of the TD 10 with a change in the heating current of the capillary is nonlinear.

In the TM 1 nominal mode, the discharge current I _p = 2.23 A must be provided with a 1.5 A thermal current, which is done by setting in BARTM 4 MP 5 when simulating the discharge current 2.23 A with ohmic resistance and introducing the corresponding installation into MP 5.

On the other hand, during the acceptance tests (PSI) of TM, xenon spills of pneumatic tracts BGR 3 TM1 without and when a current of 1.5 A is applied to the TD 10. When the TM1 and BARTM 4 equipment are turned on together, the thermal inductor current is automatically set by the BARTM 4 stabilization system at the level a value significantly different from 1.5 A, while providing a discharge of 2.23 A. The reason for this is the following circumstance: after turning on the TM 1 and reaching its nominal mode, the gas kinetic pressure of xenon in the cathode cavity oveshivaetsya Plasma discharge pressure of the cathode.

, а в катод

. Это соотношение, примерноSimilarly, the gas-kinetic pressure of xenon entering the discharge chamber is balanced by the pressure of the plasma discharge at the output of the anode block. In this case, xenon with a flow rate should continuously enter the anode

, and to the cathode

. This ratio is approximately

1 to 10, is set in BGR 3 using the anode JA 11 and the cathode LC 12 jets.

To realize the supply of xenon of such a flow rate at a pressure drop from the inlet of the BGR 3 to the outlet of the TD 10 from 1.75 atm to ~ 0.0395 atm (30 mmHg), and even with its exact division into the anode and cathode flow, the task in the design and technological plan is complex. This problem is solved by installing pneumatic resistors-nozzles ZhA 11 and ZhK 12 in the anode and cathode pneumotracts.

Since it is difficult to produce precision jets, they are sequentially installed in BGR 3 and regulated by the stabilization system I _p = f (I _td ), a pneumatic resistance, the role of which is played by TD 10. This thermal throttle solves several problems of blocking destabilizing factors of thrust at once, including reducing accuracy requirements for nozzles.

The thermo throttle has the ability to regulate the flow rate up to 30% of the required nominal value; therefore, it can change the anode and, at the same time, cathode flow rate over a wide range with the help of BARTM 4, thereby eliminating the rigidity of the requirements for the accuracy of flow formation by ZhA 11 and ZhK 12 BGR 3.

Another circumstance explaining the differences in the tuning value of the thermal inductor in BARTM 4 and BGR 3 is a feature of the structural diagram of the stabilization system in BARTM 4.

The block diagram of the stabilization system I _p = f (I _td ) is presented in figure 1. From this diagram it follows that there are two magnetic regulators (MRs) - the main and the backup ones, operating with different TD 10. The set discharge current of 2.23 A of the setup is formed in these MPs by their own circuits with one common DTA 6 anode current sensor.

Therefore, each of the TD 10 BGR 3 is configured to work as part of the TM separately.

Figure 2 presents an example of the tuning characteristics of one of the TD10:

a) current-voltage characteristic (CVC) of the discharge gap (anode-cathode) TM;

b) the characteristic of the discharge current output I _p (t), to the nominal operating mode for P _in = 1.75 atm;

c) the transfer characteristic of the control device MP stabilization system I _p ;

d) the transfer characteristic of the thermal reactor of the actuator of the stabilization system I _r .

- суммарный секундный массовый расход ксенона.In addition to the previously introduced designations, the following are additionally shown: RT - “operating point” (nominal tuning parameter);

- total second xenon mass flow rate.

Consider the intra-systemic interdependence of these characteristics and their relationship with the actions of the proposed method.

In the PSI process, the working pressures at the input to the source are measured, the working parameters of the plasma source (SPD) are measured for various values of the measured working pressures of the nominal range of the input line. In a specific case, the I – V characteristics of the discharge gap TM are obtained by measurements at various pressure values at its inlet (see Fig. 2a).

(см. фиг.2г). С помощью исполнительного устройства системы стабилизации разрядного тока I_р за счет дозированной подачи ксенона обеспечивается номинальный режим работы СПД.For the measured operating parameters, the transfer characteristics of the regulation of the flow rate of the working fluid per unit time through the plasma source are determined, providing the nominal mode of its operation. For SPD according to the I – V characteristic, characterizing the output of the discharge current I _r to the nominal mode and operation after reaching the mode (see Fig. 2b), the transfer characteristics of the control device MP 5 of the stabilization system I _p (see Fig. 2c) are determined, providing a nominal supply xenon

(see Fig. 2d). Using the actuator of the system for stabilizing the discharge current I _r due to the dosed xenon feed, the nominal operation mode of the SPD is ensured.

.Next, in the process of operation of the plasma source, the current values of the parameters of the transfer characteristics of the regulation of the flow of the working fluid in the plasma source and the pressure in the input line are measured. In a specific example, I _td (t) and P _in (t) are measured, and the value of the current flow rate of the working fluid per unit time is determined from these determined flow dependencies for these measured flow control parameters and pressure, namely, from the characteristic shown in FIG. 2d), taking into account the measured parameters I _td (t) and P _in (t), determine the current values

.

. При этом передаточная характеристика управляющего устройства МР системы стабилизации I_р остается неизменной на протяжении всего срока эксплуатации ТМ.BARTM 4 is configured according to the nominal parameters of the TM operation corresponding to the RT: U _p = 300 V; I _p = 2.23 A; I _td = 1.5 A;

. In this case, the transfer characteristic of the control device MP of the stabilization system I _p remains unchanged throughout the entire life of the TM.

When the TM enters the operating mode, the mass flow rate of the working fluid differs significantly from the nominal (see Fig. 2c, 2d). Further, in the process of TM operation, from the influence of the above destabilizing factors, there are constant changes in the flow rate of the working fluid. The instability of the discharge voltage (± 15 V) leads to a change in the value of the discharge current 2.23 ± 0.1 A, which, in turn, change the value of the current of the thermal reactor. As a result, changes in the mass flow rate of the working fluid occur, see Fig. 2d). Abnormal inrush currents of discharge up to 5A, lead to "saturation" of the regulatory characteristic of the MR control device, while the flow rate of the working fluid exceeds the nominal value by about two times. The pressure at the inlet to the TM P _in (t) and the current of the thermal reactor I _td (t) are independent parameters when controlling the operation of the module. The instability of the input pressure of 1.75 ± 0.1 atm, leads to significant changes in the flow rate of the working fluid, see fig.2d).

, что требует постоянного его определения.Thus, the current mass flow rate of the working fluid changes during operation

, which requires constant determination.

It should be noted that as the resource is developed by the plasma source, the indicated expenditure values, as well as the operating parameters of the source itself, undergo changes. This is evidenced by an example of a change in the SPD parameters in the process of developing its resource [4]. The pressure values at the inlet to the source may also change due to resource changes in pressure regulators. In all cases, the system for regulating the supply of the working fluid will provide the source.

In SPD, when the resource is developed, the specific impulse of thrust drops. At the same time, due to an increase in the second mass flow rate, no significant decrease in engine thrust occurs, which is an important factor for the performance of the spacecraft flight program [4].

Thus, according to certain current values of the mass flow rate of the working fluid per unit time and the duration of the source at a fixed interval, the mass of the spent working fluid is determined from the controlled volume at any stage of the resource’s development by the source:

where (t ₀ , t _k ) is the source operation interval.

A typical example of a device for the possibility of implementing the proposed method can be SPD [5], where, in particular, its operation is described in detail with devices implementing the function described in BARTM 4.

Improving the accuracy in the proposed method for determining the flow rate of the working fluid from the isolated volume of the supply system of the working fluid with a plasma source compared with the prototype is estimated by the minimum values of the volumetric flow rate. For the prototype method, it is ~ 3 cm ³ / s [3], pp. 103-104. And for the proposed method, with a second mass flow rate of 2.5 mg / s and a xenon density of ~ 60 kg / m ³ , the volumetric flow rate is ~ 4 · 10 ^-2 cm ³ / s [1].

From the ratio of values it follows that the proposed method is approximately two orders of magnitude more accurate compared to the prototype method. In addition, its use on board the spacecraft can reduce the mass of measuring devices. This is one of the determining factors when choosing methods for determining the flow rate of the working fluid from the tanks of rocket propulsion systems of the spacecraft.

BIBLIOGRAPHY

1. Kalinkin D.A., Kovtun B.C. Determination of the tightness of the storage and supply system of the gaseous working fluid of rocket engines during the spacecraft operation. - Proceedings of the RAS. Ser. Energy 2007, No. 3, pp. 132-141.

2. Patent RU 2272265 C2, IPC7 G01M 3/00. Kalinkin D.A., Kovtun B.C., Sysoev D.V. A method for determining the tightness of an isolated volume of a working fluid supply system with a plasma source, mainly in a vacuum. Inventions, 2005, No. 8.

3. Technical diagnostic tools. Directory. Under the general editorship of V.V. Klyuyev. - M.: Mechanical Engineering, 1989, pp. 103-104.

4. Patent RU 2251090 C1, IPC7: G01M 19/00, F03H 1/00, H05H 1/54. Gnizdor R.Yu., Gopanchuk V.V., Murashko V.M., Semenenko D.A. A method for predicting changes in the parameters of a stationary plasma engine in the process of developing a resource. Inventions, 2005, No. 12.

5. Patent RU 2009374 C2, IPC7: F03H 1/00, H05H 1/54. Graur V.F., Kozubsky K.N., Zhasan B.C. Stationary plasma engine. Inventions, 1994, No. 25.

Claims (1)

A method for determining the mass flow rate of a working fluid supplied from an isolated volume to a plasma source with a system for stabilizing the discharge current I _{p of the} plasma source, including measuring pressure, measuring the operating parameter of the plasma source, characterized in that the working pressure P _in (t) is measured in the input supply line plasma, determine the transfer characteristic of the thermal reactor of the actuator of the system for stabilizing the discharge current I _{p of the} plasma source, which regulates the supply of the working fluid to the plasma source, which has a nominal operating mode, and I _p = f (I _td ), where I _td is the current of the thermal reactor, during the operation of the plasma source, the current values of the working pressure in the input line and the current of the thermal reactor are measured, then according to the dependence

determine the current mass flow rate

the working fluid per unit time and according to certain current values of the mass flow rate of the working fluid per unit time on a fixed interval of operation of the source determine the mass flow rate of the working fluid from an isolated volume.

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