RU2213878C1 - Rocket engine thrust control method - Google Patents

Abstract

FIELD: rocket and space engineering. SUBSTANCE: invention relates to thrusters. Method is based on impulse changing of thrust. In process of engine operation continuous delivery of working medium into chamber is provided. Energy is supplied to working medium from external source in periodical pulses by means of arc discharge. Duration of pulse is determined by formula:

where P_ef is required value of engine effective thrust; P_MIN is engine thrust at no energy supply from external source; P_MAX is engine thrust at continuous energy supply from external source; T is pulse repetition rate. EFFECT: increased economy of rocket engine. 2 dwg

Description

 The invention relates to rocket and space technology and can mainly be used in small thrust rocket engines.

 The thrust control of a rocket engine is necessary to maintain the required thrust value when changing the operating conditions of the propulsion system and to change the thrust in order to ensure a given flight mode of the rocket or spacecraft. Existing methods for regulating the thrust of rocket engines in a wide range (deep throttling) lead to a significant decrease in efficiency and an increase in the mass and size characteristics of propulsion systems. In this regard, the problem of effectively regulating the thrust of rocket engines is one of the important problems that arise when creating and using space rocket technology.

 A known method of regulating the thrust of a rocket engine (see Dobrovolsky MV Liquid rocket engines. Design Basics. - M .: Mashinostroenie, 1968. S. 252), which consists in turning off one or more cameras of a multi-chamber engine.

 The disadvantages of this method are the large discreteness of change in traction and the large mass of the multi-chamber engine.

 Known methods for regulating the thrust of a rocket engine (see Dobrovolsky MV Liquid Rocket Engines: Design Basics. - M .: Mechanical Engineering, 1968. P. 252-254), which consist in changing the flow rate of the working fluid through the engine chamber by changing the number of revolutions of the turbopump unit, throttling the flow of the working fluid into the chamber, shutting off part of the nozzles, looping the flow of the working fluid, reducing the pressure in the tanks with the working fluid.

 The disadvantage of these methods is a significant decrease in engine efficiency when the flow rate of the working fluid deviates from the nominal value. This is due to the fact that a change in the flow rate of the working fluid leads to a change in the pressure in the chamber and, as a result, to an off-design mode of operation of the nozzle. The operation of the nozzle in an off-design mode is associated with the loss of the specific impulse of the engine (see Kulagin I.I. et al. Theory of liquid jet engines. Moscow USSR Defense Ministry, 1972. P. 160-166; Feodosiev VI, Sinyarev GB Introduction in rocket technology. M: Oborongiz, 1961. S. 269-271). Along with this, a decrease in the flow rate of the working fluid of liquid-propellant rocket engines is associated with a decrease in the pressure drop across the nozzles. As a result, the mixture formation of the fuel components in the chamber is deteriorated, which also leads to a decrease in engine efficiency.

 In addition, these methods cannot be used in liquid propellant small thrust engines, since for such engines a significant decrease in pressure from the nominal pressure in the chamber leads to instability of the combustion process.

Closest to the claimed invention should be considered a method of regulating the thrust of a rocket engine (see Belyaev N.M., Belik N.P., Uvarov E.I. Reactive control systems for spacecraft. - M .: Mechanical Engineering, 1979. P. 17 , 34-41), providing for periodic switching on and off of the engine (pulsed mode of engine operation). In a pulsed mode of engine operation, its effective thrust (constant in time thrust equivalent to pulsed mode) is determined by the relation
P _eff = to _Z P _NOM , (1)
(Appendix 2 to the decision on the grant of a patent, z. 2002113479/06),
where R _NOM is the nominal value of the engine thrust;
to _Z is the duty cycle duty cycle, which is the ratio of the engine operating time at one start to the time between successive engine starts.

 Measurement of the effective thrust value is provided by changing the duty cycle of the pulse mode.

 This method allows you to adjust the engine thrust in a wide range. Moreover, it can be used both in high-thrust engines and in low-thrust engines.

 A significant disadvantage of this method is its low profitability. This is due to the fact that starting and turning off the engine are associated with inefficient use of the working fluid. Firstly, starting and turning off the engine occurs at reduced pressure in the chamber. As a result of this, the camera operates in the over-expansion mode, which is associated with a decrease in the specific impulse. Secondly, the process of starting and turning off a liquid propellant rocket engine is associated with a deterioration in atomization, evaporation and mixing of fuel components. Thirdly, when starting and turning off the engine, the ratio of fuel components differs significantly from the optimal value, which leads to incomplete combustion of the fuel. Since when using this method, the processes of starting and turning off the engine make up a significant part of its operating time, a decrease in engine efficiency is very significant.

 The aim of the present invention is to eliminate the noted disadvantage of the prototype, i.e. increase the efficiency of the rocket engine.

 The specified goal is achieved as follows. In a method for controlling the thrust of a rocket engine, based on a pulsed change in thrust during engine operation, provide a continuous supply of the working fluid into the chamber. Energy is supplied to the working fluid in the engine chamber from an external source by means of an arc discharge with periodic pulses. In this case, the pulse duration is determined depending on the required value of the effective thrust of the engine.

где P_MIN - тяга двигателя при отсутствии подвода энергии от внешнего источника;
P_MAX - тяга двигателя при непрерывном подводе энергии от внешнего источника;
Т - периодичность следования импульсов;
t_И - продолжительность импульсов.The dependence of the thrust of the engine P from time t when using the proposed method is presented in figure 1. The effective thrust of the engine R _eff for this case can be determined as follows:

where P _MIN is the engine thrust in the absence of energy supply from an external source;
P _MAX - engine thrust with continuous supply of energy from an external source;
T is the pulse repetition rate;
t _And - the duration of the pulses.

It can be seen from the presented expression that when the duration of the pulses for supplying energy from an external source t _AND varies from 0 to G, the effective thrust of the engine changes, respectively, from P _MIN to P _MAX .

Предлагаемый способ обеспечивает возможность регулирования тяги ракетного двигателя в широком диапазоне. При этом, в отличие от прототипа, регулирование тяги не требует многократного запуска и выключения двигателя, так как регулирование тяги осуществляется при непрерывной подаче рабочего тела в камеру двигателя. В результате устраняются потери удельного импульса, связанные с работой сопла в режиме перерасширения, ухудшением смесеобразования компонентов топлива и отклонением соотношения компонентов от оптимального значения. Кроме того, подвод энергии к рабочему телу от внешнего источника посредством дугового разряда повышает температуру рабочего тела на входе в реактивное сопло, что приводит к увеличению скорости истечения рабочего тела из реактивного сопла. Благодаря этому существенно повышается экономичность ракетного двигателя.From expression (2) we obtain the formula for determining the duration of the pulses of energy supply from an external source, depending on the required value of the effective thrust of the engine:

The proposed method provides the ability to control the thrust of a rocket engine in a wide range. At the same time, unlike the prototype, thrust regulation does not require repeated starting and turning off the engine, since thrust regulation is carried out with a continuous supply of the working fluid into the engine chamber. As a result, the specific impulse losses associated with the operation of the nozzle in the over-expansion mode, the deterioration of the mixture formation of the fuel components and the deviation of the ratio of the components from the optimal value are eliminated. In addition, the supply of energy to the working fluid from an external source by means of an arc discharge increases the temperature of the working fluid at the entrance to the jet nozzle, which leads to an increase in the rate of expiration of the working fluid from the jet nozzle. Thanks to this, the efficiency of the rocket engine is significantly increased.

 Thus, the goal of the invention is achieved.

 A diagram of a device that implements the proposed method for regulating the thrust of a rocket engine is presented in figure 2.

 The device includes an engine chamber 1, which is connected to a storage and supply system of the working fluid 2. The engine chamber 1 is provided with electrodes 3 connected through a switching device 4 to an electric energy source 5, for which, for example, a solar battery can be used. The switching device 4 through the program-temporary device 6 is connected with the on-board control system 7 of the aircraft.

 Regulation of engine thrust is as follows. In the process of engine operation, the storage and supply system of the working fluid 2 provides a continuous supply of the working fluid to the engine chamber 1. In the engine chamber 1, the energy from the electric energy source 5 is supplied to the working fluid through an arc discharge between the electrodes 3 by periodic pulses. A pulsed energy supply is provided by periodically turning the switching device 4 on and off at the command of the program-time device 6. The setting of the program-time device 6 is carried out by the on-board control system 7.

 When the effective thrust of the engine deviates from the required value, the on-board control system 7 determines the new value of the duration of the energy supply pulses from the electric energy source 5 by the formula (3) and ensures the appropriate setting of the program-time device 6. As a result, the switching device 4 controlled by the program-time device 6, changes the duration of the pulses of the energy supply from the source of electric energy 5, which ensures the reduction of the effective traction needle to the desired value.

Claims (1)

A method of controlling the thrust of a rocket engine based on a pulsed change in thrust, characterized in that it provides a continuous supply of a working fluid to the engine chamber, and energy is supplied to the working fluid in the chamber from an external source by means of an arc discharge with periodic pulses, the duration of which is determined by the formula

where P _eff - the required value of the effective thrust of the engine;
P _MIN - engine thrust in the absence of energy supply from an external source;
P _MAX - engine thrust with continuous supply of energy from an external source;
T is the pulse repetition rate.

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