RU2125174C1 - Solid-propellant rocket engine - Google Patents

Abstract

FIELD: rocket engines. SUBSTANCE: this relates to rocket engines with charges of high-pulse mixed solid fuels strongly connected with body and they can be used in rockets (rocket projectiles) with hard-alloy engines with fuels which are liable to vibrating burning. Rocket engine has sectional charge of solid fuel and acoustic spaces located between sections of charge. Rear end-piece of slot-shaped (star-shaped) passage of front section is made with widening portion. Front end-piece of rear section passage is made with narrowing portion. Widening portion of front section is provided with cylindrical strip which is oriented in parallel to longitudinal axis of passage and it is located at side of rear end face of section in larger diameter of section. Made after narrowing portion of rear section is step preferably of toroidal configuration. Maximal diameter of narrowing portion of rear section passage is equal to 1.15-1.45 diameters of arms in front section passage. Depth of strip is 0.015-0.025, and its diameter is 0.5-0.7 of diameter of slots in front section. Height of step is 0.03-0.09 of difference between maximal diameter of narrowing section and passage proper in rear section of charge. Aforesaid embodiment of engine enhances stability of internal ballistic characteristics at wider spectrum of frequencies of suppressed oscillations. 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. So, for example, the occurrence of longitudinal mode pressure fluctuations, which are inherent in solid-state solid-state solid-state solid-state solid-state solid-state solid-state solid-state solid-state solid-state solid-state solid-state solid-state solid propellants, especially in cases where the ratio of the charge length to its diameter exceeds 12, 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 entire 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 patent N 3786633 "Fixation of the charge and resonant damping system in solid propellant rocket motors: CL NKI 60-255, MKI F 02 K 9/06) , and 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 fixing 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. Ram 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 at the same time, the placement of a resonant rod in the charge channel does not allow a high degree of filling 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 improve the efficiency of damping pressure fluctuations in the engine, various screens are widely used that provide acceptable characteristics of the loading density.

 Therefore, the closest in technical essence and the achieved technical effect to the claimed invention is the "Jet engine of solid fuel" according to the application N 96105263 of 03/19/96 (a positive decision on the grant of a patent of the Russian Federation of 04/24/97), adopted by the authors for the prototype. It contains a housing in which a sectional charge of solid fuel and damping rings, a nozzle block and an ignition device, acoustic cavities between the charge sections, formed by facing each other by the end surfaces of adjacent charge sections, are installed.

 The solid propellant rocket engine adopted for the prototype operates as follows.

 During the operation of solid propellant solid propellant solid fuel combustion products, the charge moves along the gas path of the engine, while in the charge on each diaphragm a certain pressure drop is formed, which has a strong damping effect on low-frequency vibrations in solid propellant solid propellant rocket engines, and additional acoustic cavities located between the charge sections provide effective quenching high frequency vibrations.

 This method is more effective than the use of resonant rods in solid propellant motors, however, the use of the described design led to the appearance of off-design pressure peaks in the initial period of engine operation at extremely positive temperatures.

 Thus, the objective of this technical solution, the prototype was the development of solid propellant rocket motors, which at an acceptable loading density provides effective damping.

 Common features with the rocket engine proposed by the authors are a housing in which a sectional charge of solid fuel and acoustic cavities located between the charge sections are installed.

 Unlike the prototype, in the rocket engine proposed by the authors, the rear end of the slotted (star-shaped) channel of the front section is made with an expanding section, and the front end of the channel of the rear section is made with a tapering section, the expanding section of the front section is equipped with a cylindrical "ribbon" oriented parallel to the longitudinal axis of the channel and located on the rear side of the section on the larger diameter of the section, behind the tapering section of the rear section there is a ledge, mainly of a toroidal shape, while the maximum diameter of the narrowing section of the channel of the rear section is 1.15 - 1.45 of the diameter of the "rays" of the channel of the front section, the depth of the "ribbon" is 0.015 - 0.025, and its diameter is 0.5 - 0.7 of the diameter of the slits of the front section, the height of the step is 0.03 - 0.09 of the difference in the maximum diameter of the tapering section and the actual channel of the rear section of the charge.

 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, to which the requested amount of legal protection applies, in all cases are sufficient.

 The objective of the invention is the creation of a rocket engine of solid fuel, ensuring the stability of ballistic characteristics (elimination of off-design pressure peaks) with effective damping of both high-frequency and low-frequency pressure fluctuations in the engine at high parameters of charge density.

A new set of structural elements, the form of their execution and relative position, as well as the ratio of the sizes of the structural elements of the proposed engine allow, in particular due to the following:
the rear end of the slot (star-shaped) channel of the front section with an expanding section - to prevent the merging of the pulsations of adjacent recirculation zones into tangential mode oscillations;
an expanding section of the front section with a cylindrical "ribbon" oriented parallel to the longitudinal axis of the channel and placed on the side of the rear end of the section at a larger diameter of the section with a depth of 0.015-0.025, and a diameter of 0.5 - 0.7 of the diameter of the "rays" of the front section; the front end of the channel of the rear section - with a tapering section with a maximum diameter of 1.15 - 1.45 of the diameter of the "rays" of the channel of the front section - to exclude the force interaction of the flow of combustion products with the front end of the rear section of the solid fuel charge;
behind the tapering section of the rear section of the ledge, mainly of a toroidal shape, with a height of 0.03-0.09 of the difference in the maximum diameter of the tapering section and the channel of the rear section of the charge itself - to ensure an uninterrupted flow of combustion products of solid fuel charge at the entrance to the channel of the rear section.

 The essence of the invention lies in the fact that in a rocket engine comprising a sectional charge of solid fuel and acoustic cavities located between the charge sections, in contrast to the prototype according to the invention, the rear tip of the slot (star) channel of the front section is made with an expanding section, and the front end of the channel of the rear section - with a tapering section, the expanding section of the front section is provided with a cylindrical "ribbon" oriented parallel to the longitudinal axis of the channel and placed on the side the rear end of the section on the larger diameter of the section, behind the tapering section of the rear section, a ledge is made, mainly of a toroidal shape, while the maximum diameter of the tapering section of the channel of the rear section is 1.15 - 1.45 of the diameter of the "rays" of the channel of the front section, the depth of the "ribbon" is 0.015-0.025, and its diameter 0.5-0.7 of the diameter of the "rays" of the front section, the height of the step is 0.03-0.09 of the difference in the maximum diameter of the tapering section and the actual channel of the rear section of the charge.

 The invention is illustrated by the drawing, in which in FIG. 1 shows a general view of the proposed solid fuel rocket engine, and FIG. 2 is a graph of the dependence of pressure (P) on the ratio of the step height (h) and the difference in the maximum diameter (D) of the tapering section and the diameter (d) of the channel of the rear section of the charge itself, on the ratio of the maximum diameter (D) of the tapering section of the channel of the rear section and the diameter ( Dl) of the "rays" of the channel of the front section and from the ratio of the depth (Vlt) and the diameter (Dlt) of the ribbon with the diameter (Dl) of the "rays" of the front section.

The proposed solid propellant rocket motor consists of a housing 1, in which a solid fuel charge 2 is located, consisting of several sections 3 with channels 4, between which damping rings 5, a nozzle block 6 and an ignition device 7 are installed. Acoustic cavities 8 are placed between adjacent sections 3 of the charge 2, formed by the end surfaces 9 adjacent sections 3 charge 2. The rear end of the gap (radial) channel 4 ⁿ 3 ⁿ front section formed with an expanding portion 10, and channel front end 4 ^of the rear section 3 ^of - a tapered portion (intake) 11. The expanding portion 10 of the front section 3 is provided with a cylindrical ⁿ "ribbon" 12, oriented parallel to the longitudinal axis of the channel 4 and ⁿ placed at the rear end side of ^claim 9, section 3 at a larger diameter portion 10 of the tapered portion 11 of the rear section 3 ^h ledge 13 is made, mainly of a toroidal shape, while the maximum diameter of the tapering section 11 of the channel 4 ^{s of the} rear section 3 ^s is 1.15 - 1.45 of the diameter of the beams of the channel 4 ^{p of the} front section 3 ^p , the depth of the ribbon 12 is 0.015 - 0.025 and its diameter is 0.5 - 0.7 diameter slots of the front section 3 ^p , the height of the step 13 is 0.03 - 0.09 of the difference between the maximum diameter of the tapering section 11 and the channel 4 ^{s of the} rear section 3 ^s .

 A solid fuel jet engine operates as follows.

 When the products of combustion of the charge of solid fuel 2 flow through the channels 4 of section 3 of charge 2 on the damping rings 5, local acceleration of the generally accelerating flow occurs, accompanied by a rise in static pressure and some loss of total pressure and absorption of acoustic energy, which ensures damping of low- and mid-frequency oscillations.

High-frequency vibrations are stabilized by the resonant acoustic cavity 8. As the charge 2 burns out due to variability in the radius of the cross section of the cavity 8, its characteristics change and track the change in the volume of the gas column in the engine (change in the conditions for oscillation generation). When the products of combustion of fuel of section 3 ^p exit at the ends 9, in the shadow between the "rays" of the channel 4 ^p turbulent recirculation zones are formed, pulsations in which can develop into oscillations of the tangential mode. Due to the supply of a jet of combustion products from the surface of the smaller diameter of the channel 4 ^p along the generatrix of the expanding section 10 into the shadow zone between the "rays", the power of the recirculation zones is reduced, which prevents the merging of the pulsations of the neighboring recirculation zones into tangential mode oscillations. At the same time, when flowing along the “ribbon” 12, the vector of the flow rate of the combustion products deviates from the radial direction to the axial parallel to the axis of the channels 4 and is directed to the intake (tapering section) 11, which limits the force interaction of the jet with the end face 9 of section 3 ^s and an unaccountable decrease in the passage section of the channel 4 ^h is excluded, thereby eliminating an unaccounted pressure increase in the front section 3 ^{p of the} engine.

As shown by experimental and theoretical studies, while reducing the maximum diameter portion 10 of diameter less than 0.5 "beams" ⁿ channel 4 derating recirculation zones sufficient to unconditioned vibration absorption does not occur. When the value of 0.7 of the diameter of the "rays" is exceeded, the flow of combustion products from one "beam" to another begins, which, due to fluctuations of the described process, leads to the development of oscillations of the tangential mode. At the same time, in this case, the radial component of the movement of the combustion products, despite the presence of a “ribbon” 12, cannot be extinguished, as a result of which the force interaction of the combustion products at the end 9 of section 3 ^s continues, causing an increase in pressure in the engine. A similar pattern is observed when performing a “ribbon” 12 with a depth less than 0.15 and a tapering section 11 with a maximum diameter less than 1.15 the diameter of the “rays” of the channel 4 ^{p of the} front section 3 ^p . If the “ribbon” is made with a depth greater than 0.25 of the diameter of the “rays” of the channel 4 ^p , the radial component of the velocity of the combustion products is completely extinguished, but at the same time the gas supply to the shadow zone between the “rays” stops and the recirculation power decreases The zones necessary to prevent tangential vibrations do not occur. If the maximum diameter of the intake 11 exceeds 1.45 the diameter of the slots of the channel 4 ^{p of the} front section 3 ^p , between the flow flowing out of the channel 4 ^p and the surface of the intake (tapering section) 11 back flows occur due to the additional free volume formed between the main product stream combustion and the surface of the fuel, and developing into powerful recirculation zones. As a result, the heat supply to the burning surface increases sharply, increasing the burning rate of the fuel, which, in turn, causes an off-design pressure increase in the engine. At the intersection of the tapering section 11 with the surface of the channel ^4h , the velocity vector of the flow of combustion products of charge 2 changes from radial to axial direction, however, the flow does not detach from the surface and the recirculation zone develops, since the volume in which, as in the prototype, was created so that reverse currents would develop turbulence, occupied by ledge 13, the toroidal surface of which flows continuously around the stream. When making a step with a height less than 0.03, the difference between the initial diameter of the section 11 and the diameter of the channel 4 ^s does not provide a continuous flow, and despite the step 13 at the beginning of the channel 4 ^s , a recirculation zone develops, which leads to the emergence of an erosive combustion mode and an increase in pressure in engine. If the step 13 is made with a height greater than 0.09 of the difference between the initial diameter of the section 11 and the diameter of the channel 4 ^s , then the decrease in the passage section of the channel 4 ^s exceeds the created by the developed recirculation zone, which also leads to an increase in pressure.

 The implementation of the rocket engine in accordance with the invention allowed to increase the stability of the ballistic characteristics of the engine with an expanded spectrum of frequencies of suppressed oscillations, reducing the loss of total pressure and thereby raising 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. 4c

Claims (1)

 A solid fuel rocket engine containing a sectional charge of solid fuel and acoustic cavities located between charge sections, characterized in that the rear end of the slot (star) channel of the front section is made with an expanding section, and the front end of the channel of the rear section is made with a tapering section, an expanding section of the front the section is equipped with a cylindrical “ribbon” oriented parallel to the longitudinal axis of the channel and placed on the larger diameter of the section from the rear end of the section, and the narrowing section of the rear section has a ledge of predominantly toroidal shape, while the maximum diameter of the narrowing section of the channel of the rear section is 1.15 - 1.45 of the diameter of the "rays" of the channel of the front section, the depth of the ribbon is 0.015 - 0.025, and its diameter is 0 , 5 - 0.7 of the diameter of the "rays" of the front section, the height of the step is 0.03 - 0.09 of the difference between the maximum diameter of the tapering section and the actual channel of the rear section of the charge.

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