RU2265746C2 - Solid-propellant rocket engine - Google Patents

Abstract

FIELD: rocketry.

SUBSTANCE: proposed solid-propellant rocket engine consists of combustion chamber accommodating solid-propellant charge secured by support grids, nozzle assembly and igniter. Charge is made form of all-round-burning grain consisting of concentrically arranged rings interconnected by radial bridges whose thickness is equal to thickness of rings. Relationships between summary area of critical section of nozzle assembly, summary initial area of charge burning surface, initial areas of burning surface of inner channel, channels between rings and outer surface, respectively, initial through areas of inner channel, channels between rings and between outer surface of charge and wall of combustion chamber, respectively, and experimental value of tolerable relative consumption for propellant used in charge, all protected by claim, are provided.

EFFECT: provision of maximum tolerable volumetric loading ratio of combustion chamber of any shape with possibility of obtaining either progressive or neutral thrust law.

5 dwg

Description

The invention relates to the field of rocket technology, namely to rocket engines of solid fuel with a small (tenths of a second) operating time, and can find application in the starting engines of unguided shells and guided missiles.

Known rocket engine of solid fuel, adopted by the authors for the prototype [1], consisting of a combustion chamber with a charge of solid fuel placed in it, fixed with support grids, nozzle block and igniter.

Due to the use of a multi-plate charge in the engine, consisting of several cylindrical channel blocks, assembled in one package and enclosed in the combustion chamber, the engine operating time is shortened, which makes it possible to increase the accuracy of hit of unguided shells due to the increase in the speed of their descent from the guides of the launcher, so as with a limited operating time, a large specific second flow rate and engine thrust are provided at a given level of ultimate pressure in the combustion chamber.

However, to fix the multi-cup charge in the combustion chamber, support gratings with a large area of the supporting surface and large passage sections are necessary, which complicates the design of the engine and increases its passive mass. The disadvantages of the prototype include the difficulty of fixing the checkers of the charge from radial movement and rotation relative to the longitudinal axis during transportation. This leads to the fact that the charge rubs against the supporting surfaces of the gratings, which leads to the formation of powder chips in the chamber and an unacceptable increase in pressure when the engine is triggered. In addition, when changing the temperature storage mode of the engine, the chips adhere to the side surfaces of the charge and the checkers can stick together, which leads to an off-design mode of the engine.

The disadvantages of an engine with an external multi-cup charge include the increase in the passive mass of the structure when the geometry of the combustion chamber changes. So, in a cylindrical combustion chamber when using an insert multi-cup charge, it is possible to realize a volumetric filling coefficient of up to 0.70 (the charge occupies up to 70% of the free volume of the engine’s combustion chamber). When using a plug-in multi-cup charge in a cylinder-conical combustion chamber, the volumetric filling coefficient decreases to 0.50 with an increase in the length of the conical section of the chamber (the charge occupies no more than 50% of the free volume of the engine’s combustion chamber, since the conical section of the combustion chamber is not filled with peripheral charge checkers). This leads to the need to increase the length of the combustion chamber (its passive mass) to accommodate the charge of the required mass. The length of the checkers is limited by the condition of the absence of erosive combustion in the central channel and in the gaps between the central checkers of the package. With an increase in the length of the checkers, an increase in the flow velocity in the channel leads not only to erosive combustion, but also to the appearance of radial and axial pressure drops (the pressure in the channel and at the rear end is lower than on the outside of the checker and at its front end). This can lead to faster burnout of the checkers at the rear end (occurrence of checker taper during the operation of the engine), reduction in the area of the supporting surface and destruction of the checkers due to their loss of stability while simultaneously applying axial and radial compressive forces during the operation of the engine.

The objective of the invention is to provide the maximum allowable coefficient of volumetric filling of the combustion chamber of a rocket engine having an arbitrary geometry, with the possibility of obtaining a progressive or neutral law of change in engine thrust with an all-round burning charge, operable in a wide temperature range of application with allowable variations in output characteristics with high reliability.

This object is achieved by the fact that in a rocket engine of solid fuel, consisting of a combustion chamber with a solid fuel charge placed in it, fixed with support grids, a nozzle block and an igniter, in contrast to the prototype, the charge is made in the form of a comprehensive combustion checker, consisting of concentrically arranged rings interconnected by radial bridges, the thickness of which is equal to the thickness of the rings, while the condition

Where

- суммарная площадь критического сечения соплового блока;

- total critical area of the nozzle block;

- суммарная начальная площадь горящей поверхности заряда;

- total initial area of the burning surface of the charge;

- начальная площадь горящей поверхности внутреннего канала, каналов между кольцами и наружной поверхности соответственно;

- the initial area of the burning surface of the inner channel, the channels between the rings and the outer surface, respectively;

- начальная проходная площадь внутреннего канала, каналов между кольцами и между наружной поверхностью заряда и стенкой камеры сгорания соответственно;

- the initial passage area of the inner channel, the channels between the rings and between the outer surface of the charge and the wall of the combustion chamber, respectively;

q (λ) _add - the experimental value of the allowable relative flow rate for the fuel used in the charge, determined experimentally with the help of bench installations, protrusions can be made on the inner surface of the central charge ring.

The combination of structural elements, their mutual arrangement and the presence of optimal ratios of their geometric dimensions allows you to:

- realize the value of the coefficient of volumetric filling of the cylindrical combustion chamber 0.70-0.75 (the charge occupies 70-75% of the free volume of the combustion chamber of the engine), cylinder-conical combustion chamber - not less than 0.60-0.70 (the charge takes 60-70% free volume of the combustion chamber of the engine, since the conical section of the chamber is occupied by radial jumpers). An increase in the number of jumpers between the rings leads to an increase in the volumetric filling coefficient. The execution on the inner surface of the Central ring of the charge of the protrusions also allows you to increase the coefficient of volumetric filling of the combustion chamber;

- to provide the possibility of obtaining a progressive nature of the change in traction for an engine with a cylindrical combustion chamber. In this case, the necessary degree of progressivity is provided by the choice of the number of jumpers between the rings (with an increase in the number of jumpers, progressiveness increases). Traction constancy during engine operation can be ensured by conical sharpening on the outer surface of the charge. Thus, the degree of progressiveness of the engine thrust is governed by the number of jumpers, as well as the length and angle of sharpening on the outer surface of the charge. A decrease in the degree of progressivity can also be achieved by performing protrusions on the inner surface of the central ring of the charge;

- to ensure operability in a wide temperature range of application with allowable variations in the output characteristics of the engine with high reliability due to the fulfillment of the ratio between the areas of burning surfaces and passage sections. Fulfillment of the indicated ratio allows implementing a non-erosive regime of fuel combustion in the charge channels, since in this case the maximum flow rate above the burning surface can be realized only in the annular gap between the outer surface of the charge and the wall of the combustion chamber. Since the fraction of the outer surface in the total combustion surface is insignificant, even in the presence of erosive combustion (exceeding the permissible value q (λ) _add ) in the gap between the outer surface of the charge and the wall of the combustion chamber, possible pressure variations will not lead to unacceptable deviations of the engine output characteristics. If this ratio is violated, erosive combustion of the fuel may occur in the internal charge channels, the surface fraction of which in the total combustion surface exceeds the fraction of the outer surface. This can lead to an off-design pressure increase, to the non-simultaneous combustion of the charge along the length and radius, and ultimately to either the destruction of the charge and the engine, or to unacceptable deviations of the output characteristics of the engine. When implementing the specified ratio between the areas of the burning surfaces and the cross-sections during operation, the charge is affected by a radial pressure drop directed from the axis of the engine, which ensures the optimal strength mode of charge operation. Tensile stresses are transferred by jumpers to the outer ring and since the pressure in the channels between the rings and the annular gap is lower than in the internal charge channel, there is no compressive force on the outer ring in the areas between the jumpers;

- to exclude the formation of powder chips in the chamber due to the possibility of constructive design of support grids with limiters of rotation of the charge included in part of the charge channels, and thereby eliminate an unacceptable increase in pressure when the engine is triggered.

The essence of the invention is illustrated by graphic materials, where Figs. 1, 2 show the design of an engine with a cylindrical combustion chamber, Figs. 3, 4 show a design of an engine with a cylindrical combustion chamber, with a support grid made with charge rotation limiters included in the part charge channels, figure 5 presents the dependence of the degree of progressivity S / S ₀ and the volumetric coefficient of the engine chamber Δ _w on the design of the proposed charge - the number of jumpers n.

The proposed engine includes a combustion chamber 1 with a solid fuel charge 2 placed in it, front 3 and rear 4 support grids, a nozzle unit 5 and an ignitor 6. The outer ring 7 is connected to the inner charge ring 8 by radial jumpers 9. On the back support grill can be made limiters of rotation of the charge 13 included in part of the channels of the charge, and on the inner surface of the Central ring 8 of the charge 2 can be made protrusions 14. The thickness of the inner 8, outer 7 rings h and jumpers 9 are equal.

Charge 2 can be made from existing ballistic solid rocket fuels using standard processes.

The possibility of producing a charge from ballistic solid fuels with more than two rings is limited by the requirements for the permissible level of variation in the output characteristics of the engine. When the number of rings is more than two tool needles, the channels forming between the rings should have a large overhang on the pylons relative to the outer or inner forming surfaces. As a result, the stiffness of the pylons decreases and needle oscillations are possible during pressing, which leads to unacceptable thickness variations of the rings and jumpers and to an unacceptable increase in the dispersion of the output characteristics of the engine. In addition, when the number of rings is more than two, it is difficult to ensure constant fuel characteristics in the charge in the radial direction, since rings of different levels will be pressed with different forces.

The functioning of the proposed engine is as follows. After the operation of the igniter 6, a charge 2 is placed in the combustion chamber 1. The products of fuel combustion from the surface of the charge passing through the internal channel 10, the channels between the rings 11 and the annular gap between the charge and the walls of the combustion chamber 12 expire through the nozzle 5, creating a thrust , the nature of the change of which is determined by the degree of charge progressivity (the number of jumpers).

The proposed implementation of a solid fuel rocket engine will allow for a maximum volumetric coefficient of the combustion chamber of a rocket engine with an arbitrary geometry, if it is possible to obtain a progressive or neutral law of change in engine thrust with an all-round burning charge, operable in a wide temperature range of application with allowable variations in output characteristics with high reliability.

Sourse of information.

1. Fundamentals of the design and construction of aircraft. V.N. Novikov, B.M. Avkhimovich, V.E. Veitin - M.: Mechanical Engineering, 1991, p. 119.

Claims (2)

1. A rocket engine of solid fuel, consisting of a combustion chamber with a solid fuel charge placed in it, fixed with support grids, a nozzle block and an igniter, characterized in that the charge is made in the form of a comprehensive combustion checker consisting of concentrically arranged rings connected between radial jumpers, the thickness of which is equal to the thickness of the rings, while the condition:

Where

- total critical area of the nozzle block;

- total initial area of the burning surface of the charge;

- the initial area of the burning surface of the inner channel, the channels between the rings and the outer surface, respectively;

- the initial passage area of the inner channel, the channels between the rings and between the outer surface of the charge and the wall of the combustion chamber, respectively; q (λ) _add - the experimental value of the allowable relative flow rate for the fuel used in the charge. 2. The rocket engine of solid fuel according to claim 1, characterized in that the protrusions are made on the inner surface of the central charge ring.

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