RU2125173C1 - Solid-propellant rocket engine - Google Patents

Abstract

FIELD: rocket engines. SUBSTANCE: this relates particularly to solid-propellant rocket engines with charges of high-pulse mixed solid propellants strongly connected with body, and they can be used in rockets (rocket projectiles) with hard-alloy engines and with fuels which are liable to vibration burning. Rocket engine has body, charge of solid propellant with igniting device, main chamber and additional chamber which are connected together through nozzle. End face of charge at side of body bottom part is made flat. Additional chamber is made in the form of hollow which is formed by body bottom part and front end face of charge. Nozzle is made as subsonic and it adjoins front end face of charge. Cross-section area of nozzle bore is determined according to following formula: F = KW/P $\genfrac{}{}{0ex}{}{\text{*}}{\text{o}}$ q(λ)^*τ_t, where K - calculating and experimental transient coefficient also taking into consideration outflow parameters of fuels used in charge and igniting device, w - initial volume of additional chamber, P $\genfrac{}{}{0ex}{}{\text{*}}{\text{0}}$ - retarding pressure created by igniting device, q(λ)^* - - reduced flow rate for λ<1, τ_t - operating period of igniting device. Aforesaid embodiment of engine enhances its operating stability. EFFECT: higher efficiency. 1 dwg

Description

 The invention relates to rocket engines of solid fuels, in particular to solid propellant rocket engines with charges of high-pulse mixed solid fuels, firmly bonded to the body, and can be used in rockets (rockets) with solid fuel engines whose fuels are prone to vibrational combustion.

 The object of the invention is a rocket engine with a charge of high-pulse mixed solid fuel firmly bonded to the engine body, designed to convert the potential energy of the fuel into the kinetic energy of the carrier and can be used as an engine - mover of a newly developed long-range missile.

 Vibration combustion in a solid propellant rocket chamber accompanied by a periodic change in pressure is a harmful phenomenon and can significantly affect engine reliability, timing of implementation, stability of ballistic characteristics, etc. For example, the occurrence of longitudinal mode pressure fluctuations, which are inherent in a solid elongated solid-state solid propellant, especially in cases where the ratio of the charge length to its diameter exceeds 10), is accompanied by mechanical vibrations and the appearance of alternating loads in the longitudinal direction. This can lead to disruption of the onboard control system and even to the destruction of the engine and the missile as a whole.

 Therefore, when creating new solid propellant rocket motors, simultaneously with measures to increase the total thrust impulse generated by the propulsion system, measures are taken to stabilize the combustion processes of the solid fuel charge.

 So, it is known a device that provides damping of vibrations in the event of vibrational combustion in solid propellant rocket motors (see, for example, US Pat. No. 3,786,633 "Fixation of a charge and a resonant system for suppressing vibrations in solid propellant rocket motors: NKI 60-255, MKI F 02 K 9/06 ), adopted by the authors as an analogue. In the known device is a structural circuit of a solid-state solid-propellant rocket with a charge fixation system and a resonant rod. Solid-state rocket solid rocket motor has a housing, an igniter, a nozzle and an auxiliary charge provided with an armor coating on the outer surface and both ends. ii unstable combustion in SRM-used analog resonance rod disposed in the charging channel.

 However, the resonant rods do not absorb high-frequency vibrations of a number of modes, and the placement of a resonant rod in the charge channel does not allow a high degree of filling of the engine chamber with fuel.

 Thus, the objective of this technical solution was to damp the pressure fluctuations of a number of modes in the event of unstable charge burning.

 Common signs with the rocket engine proposed by the authors is the presence of a housing, igniter, nozzle and charge as part of an analog device.

 At the same time, to increase the efficiency of damping pressure fluctuations in the engine, resonant acoustic cavities and various screens are widely used that provide acceptable characteristics of the charge density.

 Therefore, the closest in technical essence and the achieved technical effect to the claimed invention is a solid propellant rocket motor according to US Pat. U.S. N 3210932, cl. NKI 60-256, MKI F 02 K 9/04, adopted by the authors for the prototype. It contains a housing, a channel charge of solid rocket fuel, an igniter, a main and an additional chamber connected to each other through a supersonic nozzle, while the wall of the additional chamber is formed by a cylindrical combustion surface of the charge channel.

 The solid propellant rocket engine adopted for the prototype operates as follows. When operating solid propellant rocket engines, the combustion products of solid fuel charge move along the gas path of the engine, while high-frequency vibrations are stabilized in the resonant acoustic cavity of the additional chamber.

 This method is more effective than the use of resonant rods in solid-state solid propellant motors, however, as the tests showed, the described design unsatisfactorily damps vibrations at the instant of ignition operation, which creates strong perturbations in the gas column of the combustion products, and changes sharply (in proportion to the square of the burning rate of the solid fuel charge) tuning of the resonant acoustic cavity does not allow to stabilize high-frequency oscillations during the whole time of the engine operation.

 Thus, the objective of this technical solution, the prototype was to develop a design that provides, at an acceptable loading density, damping vibrations in the initial period of working (quasi-stationary) engine operating modes.

 Common signs with the proposed rocket engine are the body, the charge of solid fuel with an igniter, the main and additional chambers connected by a nozzle.

где К - расчетно-экспериментальный переходный коэффициент, учитывающий, в том числе, параметры истечения топлив, применяемых в заряде и воспламенительном устройстве;
W - начальный объем дополнительной камеры;
p_o- давление торможения, создаваемое воспламенительным устройством;
q(λ) - приведенный расход для λ < 1;
τ_в- время работы воспламенительного устройства.In contrast to the prototype, in the rocket engine proposed by the authors, the end of the charge from the side of the bottom of the body is made flat, and the additional chamber is made in the form of a cavity formed by the bottom of the body and the front end of the charge, while the nozzle is made subsonic, and its passage area is determined by the formula

where K is the calculated and experimental transition coefficient, taking into account, inter alia, the parameters of the expiration of fuels used in the charge and ignition device;
W is the initial volume of the additional chamber;
p _o is the braking pressure created by the igniter;
q (λ) is the reduced flow rate for λ <1;
τ _in - the operating time of the igniter device.

 It is this that allows us to conclude that there is a causal relationship between the totality of the essential features of the claimed technical solution and the achieved technical result.

 These signs, distinctive from the prototype and to which the requested amount of legal protection applies, are sufficient in all cases.

 The objective of the invention is the creation of a rocket engine of solid fuel, which provides effective damping and stabilization of both high-frequency and low-frequency pressure fluctuations in the engine during the entire time of its operation, including the moment of ignition operation, at high parameters of charge density.

обеспечить постоянное докритическое истечение из основной камеры в дополнительную, тем самым эффективно гасить высокоамплитудные колебания в донной части двигателя с самого начала процесса выхода его на режим - с момента срабатывания воспламенительного устройства.A new set of structural elements, the form of their execution and the relative position, as well as the presence of connections between parts and components of the proposed engine and the ratio of their parameters, allow, in particular, due to the following:
- the front end of the charge from the side of the bottom of the casing is flat, an additional chamber in the form of a cavity formed by the bottom of the casing and the front end of the charge, and the nozzle adjacent to the front end of the charge - constantly stabilize high-frequency vibrations in the engine by maintaining the characteristics of the resonant acoustic cavity at a level a corresponding increase in the volume of gas in the chambers as the charge burns out, provided by a change in the volume of the cavity in proportion to the rate of combustion of the charge by moving the end face, about the agreed charge combustion;
- a subsonic nozzle with an initial flow area defined by the ratio

to ensure constant subcritical outflow from the main chamber to the additional one, thereby effectively damping high-amplitude oscillations in the bottom of the engine from the very beginning of the process of entering it into operation — from the moment the igniter device is activated.

где К - расчетно-экспериментальный переходный коэффициент, учитывающий, в том числе, параметры истечения топлив, применяемых в заряде и воспламенительном устройстве;
W - начальный объем дополнительной камеры;
p_o- давление торможения, создаваемое воспламенительным устройством;
q(λ) - приведенный расход для λ < 1;
τ_в- время работы воспламенительного устройства.The essence of the invention lies in the fact that in a rocket engine including a housing, the charge of solid fuel with an igniter, the main and additional chambers connected by a nozzle, unlike the prototype, according to the invention, the front end of the charge from the bottom of the housing is made flat, and the additional chamber made in the form of a cavity formed by the bottom of the body and the front end of the charge, while the nozzle is made subsonic and adjacent to the front end of the charge, and the initial passage area with la is defined by the relation

where K is the calculated and experimental transition coefficient, taking into account, inter alia, the parameters of the expiration of fuels used in the charge and ignition device;
W is the initial volume of the additional chamber;
p _o is the braking pressure created by the igniter;
q (λ) is the reduced flow rate for λ <1;
τ _in - the operating time of the igniter device.

 The invention is illustrated by the drawing, in which in FIG. 1 shows a General view of the proposed rocket engine of solid fuel.

(обозначения приведены выше).The proposed solid propellant solid propellant rocket motor consists of a housing 1, in which a firmly bonded solid fuel charge 2 and an ignition device 3 are located. The charge channel 4 and the pre-nozzle volume 5 of the housing 1 form the main chamber 6. In the bottom part 7 of the housing 1 there is an additional chamber 8 made in the form cavity 9 formed by the bottom part 7 of the housing 1 and the front end face 10 of the charge 2. The main 6 and additional 8 chambers communicate through a nozzle 11 made subsonic in the channel 4 of the charge 2 adjacent to the end face 10. The end face 10 of the charge 2 is made flat, and the nozzle is made EHO subsonic with the initial area determined from the condition ensure continuous subcritical expiration ratio

(designations are given above).

 The above solid fuel jet engine operates as follows.

 After the ignition device 3 is activated, it is filled with the combustion products of the main chamber 8 and (through the nozzle 11) of the additional chamber 6. In the nozzle 11, the flow of combustion products of the igniter device 3 and, partially, the charge 2, flowing into the additional chamber 6 is localized, accompanied by a rise static pressure, loss of total pressure, absorption of acoustic energy, and accordingly, the damping of high-amplitude vibrations in the bottom of the engine. High-frequency oscillations are stabilized in the resonant acoustic cavity 9 of the additional chamber 8, the volume of which changes in proportion to the burning rate of the charge 2 due to the movement of the end face 10 due to the burning of the charge 2. This allows you to maintain the characteristics of the resonant acoustic cavity 9 at a level corresponding to an increase in the volume of gas in the chambers 6 and 8 as charge 2 burns out and constantly stabilize high-frequency vibrations in the engine. In addition, as the charge 2 burns out, the difference in the areas of the nozzle 11 and channel 4 decreases, reducing the loss of total pressure in the bottom of the engine.

 The implementation of the rocket engine in accordance with the invention has improved the stability of the ballistic characteristics of the engine with an expanded spectrum of frequencies of suppressed oscillations, while reducing the loss of total pressure and thereby increasing the reliability and energy characteristics of the engine.

 The indicated positive effect was confirmed by fire bench tests of prototypes of solid propellant rocket motors made in accordance with the invention (report inv. N 46656).

 Currently, development of working design documentation is underway, production and preliminary tests of prototypes are planned, mass production of the engine is scheduled. 3o

Claims (1)

A solid fuel rocket engine comprising a housing, a solid fuel charge with an igniter, a primary and secondary chamber connected by a nozzle, characterized in that the end face of the charge on the bottom of the housing is flat, and the secondary chamber is made in the form of a cavity formed by the bottom case and the front end of the charge, while the nozzle is made subsonic and adjacent to the front end of the charge, and the area of its passage section is determined by the formula

where K is the calculated and experimental transition coefficient, taking into account, inter alia, the parameters of the expiration of the fuel used in the charge and ignition device;
W is the initial volume of the additional chamber;
P $\genfrac{}{}{0ex}{}{\text{*}}{\text{0}}$ - braking pressure generated by the igniter;
q $\genfrac{}{}{0ex}{}{\text{*}}{\text{λ}}$ - reduced flow rate for λ <1;
τ ₃ - the operating time of the igniter device.