RU2171389C2 - Controlled rocket engine - Google Patents

Abstract

FIELD: rocketry. SUBSTANCE: proposed invention can be used in designing of solid-propellant rocket engine with wide range thrust control in flight. Rocket engine has housing 1, charge 2, nozzle 9 and hydraulic unit consisting of cup 3 pointed inwards the space of housing 1, piston 4 installed in cup 3 for longitudinal travel, liquid cooling agent 6 located in under-piston space 5 of cup 3. Under-piston space 5 of cup 3 is coupled with nozzle unit 7 pointed into space of housing 1. Piston 4 is of differential (stepped) make. Adjustable throttle 8 is installed between under-piston space 5 and nozzle unit 7. EFFECT: simplifies design, reduced mass, increased summary operation time on specific kind of fuel at preset overall dimensions of engine, reduced transient process time. 2 cl, 3 dwg

Description

 The invention relates to rocket technology and can be used to create solid propellant rocket engines with command control of thrust in flight over a wide range.

 It is known [Fakhrutdinov I.Kh., Kotelnikov A.V. Construction and design of solid propellant rocket engines: A manual for engineering universities - M: Mechanical Engineering, 1987, 328 pp., Ill.], That to solve problems such as intercepting, approaching, correcting the trajectory and range, maneuvering, mooring or soft landing in space flight conditions, thrust control of the rocket engine is required.

The thrust of the solid propellant rocket motor can be regulated by means of a thermal knife [V. Petrenko et al. "RDTT with an adjustable traction module", Miass, Publishing House GRTS "Design Bureau named after Academician VP Makeev", 1994, p. 69-70, fig. 3.1] The disadvantages of this type of solid propellant rocket motors are:
- a relatively large mass and design complexity;
- large transient times associated with geometric reconstruction of the combustion surface;
- a large length of the engine, caused by the need for a large thickness of the burning roof for fuels with existing burning rates;
- a relatively short time for a given value of the thickness of the burning roof (to reduce the rate of burning of fuel, varying its chemical composition, is more difficult than to increase the rate of burning, and a thermal knife can only increase the rate of burning).

 Closest to the proposed invention in terms of technical nature and the achieved positive effect is a guided rocket engine [Fakhrutdinov I. Kh., Kotelnikov A.V. Design and engineering of solid propellant rocket engines: A manual for engineering universities - M: Mechanical Engineering, 1987, 328 pp., Ill., Pages 250, 251, fig. 9.47], containing a charge, a nozzle and a hydraulic unit consisting of a nozzle and installed in the nozzle with the possibility of longitudinal movement of the piston, refrigerant fluid located in the under-piston cavity of the nozzle, the under-piston nozzle cavity being connected to the nozzle block facing the body cavity.

The control function of such an engine is limited by controlling the value of the total thrust impulse by quenching by means of water injection. The main disadvantages of the engine with a hydraulic extinguishing unit are:
- discreteness of regulation;
- the possible presence of several igniters increases the mass of the structure, leading to its complexity;
- the need for a large flow rate of water during injection complicates the nozzle block and increases the acting loads (pressure in the cavity of the hydro-quenching unit), that is, it leads to an increase in the mass of the structure.

 The technical task of the present invention is to simplify the design and reduce its mass; increase in the total operating time on this fuel for a given engine size; reduced transient times.

 The essence of the invention lies in the fact that in the known guided rocket engine containing a housing, a charge, a nozzle and a hydraulic unit, consisting of a facing into the cavity of the housing of the glass mounted in the glass with the possibility of longitudinal movement of the piston, the refrigerant fluid located in the under-piston cavity of the glass, moreover, the under-piston cavity of the cup is connected with the nozzle block facing the cavity of the housing, the piston is made differential (i.e. stepwise), and between the under-piston cavity and the nozzle block flax adjustable throttle.

The technical result is achieved due to the effect of lowering the temperature of the combustion products when water is injected into the combustion chamber. If the injection intensity is comparable to the gas intake from the charge, then the charge is quenched due to the intense heat extraction for heating and evaporation of the injected water. If the injection intensity is such that at any moment of the engine’s operation, 10-15% of water is in the combustion chamber, then the temperature in the chamber is regulated regulated, without causing the charge to cease to burn. Following a decrease in temperature, the pressure of the combustion products decreases, decreasing the convective heat supply to the combustion surface (both due to a decrease in pressure and due to a decrease in temperature). The burning rate of the fuel and the gas intake are reduced and the engine switches to low thrust mode. In order to prevent charge quenching while the engine is running stable, the water injection device should be auto-adjustable, that is, when the pressure in the combustion chamber is reduced, this device should automatically reduce the injection intensity. This property of auto-regulation has an injection unit with a differential piston. If the geometrical parameters of the injection unit are selected in such a way that with a decrease in the chamber pressure, the injection intensity decreases at the same level as the gas inlet decreases, then there is a pressure value P _{k min} at which the engine will operate stably under reduced thrust. When changing the flow area of the adjustable throttle changes the value of P _{k min} .

приход хладагента (воды) в камеру сгорания при этом составляет

(график П_ж=f(P_k) для фиксированного значения S представлен на фиг. 2).The patterns of the flow control (and draft) process are illustrated in FIG. 2. With steady-state (stationary) engine operation, the differential piston speed is

the arrival of refrigerant (water) in the combustion chamber in this case is

(the graph P _f = f (P _k ) for a fixed value of S is shown in Fig. 2).

In the absence of injection into the combustion chamber, the gas intake from the charge is
P _r = Fρ _t u ₁ P $\genfrac{}{}{0ex}{}{\text{ν}}{\text{k}}$ (2)
(the schedule P _g = f (P _k ) with ν = 0.2 ... 0.3 is shown in Fig. 2).

На фиг. 2 представлен график G_г = f(P_k) для температуры чистых продуктов сгорания и график G_г+ж= f(P_k) для пониженной температуры парогазовой смеси, обеспечивающей повышенный расход (см. выражение (3)).The consumption of combustion products or gas-vapor mixture through the nozzle is equal to

In FIG. Figure 2 shows a graph of G _g = f (P _k ) for the temperature of pure combustion products and a graph of G _{g + f} = f (P _k ) for a lower temperature of a gas-vapor mixture providing an increased flow rate (see expression (3)).

In the above expressions, the following notation:
D is the large diameter of the differential piston;
d is the small diameter of the differential piston;
σ _cr - the area of the critical section of the nozzle;
F is the surface area of the combustion of the charge;
S - flow area of an adjustable throttle;
μ is the coefficient of fluid flow;
ρ _W - the density of the liquid;
ρ _t - density of solid fuel;
u ₁ is the burning rate of the fuel at a pressure of 1 kG / cm ² ;
ν is an indicator in the law of the rate of fuel combustion;
R is the gas constant;
T is the temperature in the combustion chamber;
A is a coefficient characterizing the outflow of gas.

In the absence of injection (S = 0), the engine operates at a pressure P _k1 (see Fig. 2), where P _g = G _g . The flow rate of the working fluid (combustion products) is G ₁ .

When you open the adjustable throttle due to the receipt of refrigerant in the combustion chamber according to (1), the gas inlet from the charge decreases. A plot of P _{g + f} = f (P _k ) for a given fixed value of S is shown in FIG. 2 (when constructing this graph, the critical section area is mentally clamped). Stable operation of the engine during injection is possible at the point where the gas intake P _{g + f} becomes equal to the flow rate G _{g + f} , that is, at a pressure P _{k min} . The flow rate of the working fluid (gas-vapor mixture) is equal to G ₂ (see Fig. 2).

тяга двигателя, равная произведению удельного импульса на расход, уменьшается. Для обратного увеличения тяги достаточно перекрыть регулируемый дроссель.Due to the fact that G ₂ <G ₁ , and also due to a decrease in the specific impulse of thrust, which depends on the temperature in the chamber

the engine thrust equal to the product of the specific impulse and the flow rate decreases. To reverse thrust increase, it is enough to block the adjustable throttle.

 The proposed engine is capable of providing both a discrete-step sequence diagram of thrust change (Fig. 3a) and smooth regulation (Fig. 3b).

 Suppose that a given sequence diagram provides for up to 50% of rocket fuel to be used in low thrust modes. Then the required supply of water is 0.5x0.2 = 0.1, i.e. 10% of the mass of the charge. The mass perfection coefficient of conventional (unregulated) solid propellant rocket motors (ratio of structural mass to fuel mass) is approximately 0.1. Suppose that the dry mass of the design of the proposed engine is 2 times greater than that of conventional solid propellant motors. Then the coefficient of mass perfection of the proposed engine, taking into account the required supply of refrigerant, is approximately 0.3, that is, the mass perfection of the proposed engine is better than most known schemes of regulated solid propellant rocket motors. The specific thrust impulse of the proposed engine, which allows the use of high-energy fuels, is also higher (most known schemes of adjustable engines with mechanical regulators such as valves, thermal knife, etc. involve the use of low-temperature fuel compositions with low energy).

 The increase in the total operating time of the engine at given dimensions that determine the maximum possible thickness of the burning charge set when using fuels with the existing burning rate is achieved due to the fact that the proposed method of regulation is based on lowering the burning rate of the fuel in low draft modes by means of artificial heat selection.

 The proposed engine has the smallest transient time among the known schemes of regulated solid propellant motors (both in comparison with engines whose regulation process is based on the geometric reconstruction of the combustion surface under the influence of a heat knife, and in comparison with engines with an adjustable critical nozzle section). In an engine with an adjustable critical nozzle section, when the thrust decreases, the transition process consists of a decrease in the pressure in the combustion chamber to a new level and a decrease in the burning rate, on the one hand, which tracks the pressure drop, and on the other hand, which drags this drop (that is, the process has " spurious "share of the gas intake). For the proposed engine, the initial decrease in temperature (and hence pressure and gas intake) occurs almost instantly (for 0.001-0.003 s). The outflow time of the "excess" cold vapor-gas mixture is comparable to the time of a similar process when controlling the critical section of the nozzle, but occurs faster due to the larger outflow coefficient (expression (3)) and the absence of a "parasitic" fraction of the gas intake. In addition, due to the instantaneous decrease in specific impulse, the engine thrust decreases faster than the outflow of the "excess" vapor-gas mixture.

 Minimum transient times increase regulation accuracy.

 The specified technical solution is not known from the patent and technical literature.

The invention is illustrated by the following graphic material:
- in FIG. 1 shows a longitudinal section through a guided rocket engine,
- in FIG. 2 presents a flow control scheme (thrust) of the proposed engine,
- in FIG. 3 shows cyclograms of thrust change (in thrust coordinates R is time τ), which the proposed engine is capable of providing.

 The guided rocket engine contains a housing 1 with a charge 2. On the housing 1 is fixed a glass 3 facing the cavity of the housing 1. In the glass 3 is installed with the possibility of longitudinal movement of the differential piston 4. In the under-piston cavity 5 of the glass 3 is a refrigerant liquid 6 (for example, water ) In the cavity of the housing 1 there is a nozzle block 7 connected through an adjustable throttle 8 with a piston cavity 5 of the glass 3. The nozzle 9 of the engine can be made in a differential piston 4 (or in the housing 1). In the initial position, the adjustable throttle 8 is completely closed.

При перекрытом дросселе 8 дифференциальный поршень 4 остается неподвижен. Для перехода двигателя на режим пониженной тяги открывается регулируемый дроссель 8. В результате впрыска жидкости-хладагента 6 в полость корпуса 1 по зависимости (1) температура, давление и газоприход уменьшаются, и двигатель начинает работать на режиме пониженной тяги (с расходом G₂). При изменении проходного сечения регулируемого дросселя 8 меняются параметры работы двигателя (давление P_{k min}, расход G₂, тяга). При перекрытии регулируемого дросселя 8 двигатель возвращается на режим маршевой (максимальной) тяги.The device operates as follows. The engine is started by any of the known ignitors (not shown). After ignition, the pressure in the cavity of the housing 1 rises to a value of P _k1 (see Fig. 2). The engine starts to operate in marching mode (with a flow rate of G ₁ ). The pressure P _{W of the} liquid refrigerant 6 in the hydraulic cavity 5 under the action of the differential piston 4 exceeds the pressure in the combustion chamber:

When the throttle 8 is blocked, the differential piston 4 remains stationary. To switch the engine to reduced thrust mode, an adjustable throttle opens 8. As a result of injection of refrigerant liquid 6 into the cavity of housing 1, temperature, pressure and gas intake decrease according to (1), and the engine starts to operate in reduced thrust mode (with flow rate G ₂ ). When changing the flow area of the adjustable throttle 8, the engine operating parameters change (pressure P _{k min} , flow rate G ₂ , thrust). When the adjustable throttle 8 is closed, the engine returns to the marching (maximum) thrust mode.

 Technical and economic efficiency of the invention in comparison with the prototype, which is selected as a controlled rocket engine [Fakhrutdinov I. Kh. Kotelnikov A.V. Design and engineering of solid propellant rocket engines: A manual for engineering universities - M: Mechanical Engineering, 1987, 328 pp., Ill., Pages 250, 251, fig. 9.47], is to simplify the design and reduce its mass; an increase in the total operating time for a given fuel for a given engine size; reducing transient times.

Claims (1)

 A guided rocket engine containing a housing, a charge, a nozzle, and a hydraulic unit, consisting of a nozzle facing the cavity of the nozzle installed in the nozzle with the possibility of longitudinal movement of the piston, refrigerant fluid located in the nozzle cavity of the nozzle, the nozzle cavity of the nozzle connected to the nozzle block, facing the body cavity, characterized in that the piston is made differential (i.e. stepwise), and an adjustable throttle is installed between the piston cavity and the nozzle block.

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