RU2269024C1 - Method of and device for ignition of solid-propellant charge in solid-propellant rocket engine - Google Patents

Abstract

FIELD: rocketry; methods of ignition of solid-propellant charge.

SUBSTANCE: proposed method comes to ignition of igniter, propagation of burning products to charge, heating of charge surface and subsequent ignition of charge. First combustion products from igniter placed in semiclosed space of engine combustion chamber are directed to front end face of charge. After ignition of part of charge surface, combustion products from igniter are delivered to rear end face of charge. After combustion of igniter combustion products of charge formed at front end face are passed through space into prenozzle space of engine. Method of ignition of charge is implemented in solid-propellant rocket engine containing combustion chamber with nozzle unit, igniter and multigrain charge with support grid. Tube is secured on support grid from side of nozzle unit coaxially to chamber. Tube is divided into two spaces by partition with through holes closed by diaphragm. Diaphragm is installed between end face of partition and end face of igniter arranged in space pointed to front end face of charge. Annular channel is formed between free end of tube and front bottom of combustion chamber. Area of said channel is chosen to provide the following condition: summary area of holes in partition should be smaller than area of channel which, in its turn, should be smaller than area of cross section of tube.

EFFECT: increased reliability of solid-propellant rocket engine with charge with large relative elongation in wide temperature range.

3 cl, 1 dwg

Description

The invention relates to the field of rocket technology, namely to rocket engines of solid fuel (solid propellant rocket engines) and methods for igniting their charges.

A known method of igniting the charge of a rocket engine of solid fuel, selected for the prototype, including ignition and combustion of the igniter, the distribution of its combustion products along the charge, heating its surface and ignition due to the heat of the gases of the igniter, which is usually located at the front bottom of the combustion chamber [Internal ballistics of barrel systems and powder rockets. M.E.Serebryakov - M .: Oborongiz, 1962, p. 255]. The method is implemented by a solid fuel rocket engine containing a combustion chamber with a nozzle block, an igniter and a multi-cup charge with support grids. An igniter having a thin-walled body made of aluminum alloy, inside of which is placed smoke gun powder or a pyrotechnic composition, is located at the front bottom of the combustion chamber on its axis [Fundamentals of the design and construction of aircraft. V.N. Novikov, B.M. Avkhimovich, V.E. Veitin - M.: Mechanical Engineering, 1991, p. 119, 127]. This arrangement of the igniter provides reliable ignition of the charge of small elongation (the ratio of the length of the block to its outer diameter L / D≤3 ÷ 5), since the products of ignition of the igniter wash the entire surface of the charge, and reliable operation of the engine in the absence of strict requirements for the dispersion of output characteristics.

However, when a charge is ignited in a known manner from thin-walled checkers of large relative elongation (when the ratio of the length of the block to its outer diameter L / D> 7), a significant pressure drop occurs over the length of the charge, under which the end supporting surfaces of the charge blocks partially break in contact with back support lattice. This leads to an arbitrary increase in the surface of the combustion of the charge, the creation of a prohibitive pressure in the combustion chamber of the engine and, as a consequence, to the destruction of the engine. A possible decrease in the mass of the igniter reduces the pressure drop along the length of the charge, but at the same time the reliability of ignition of the charge at low temperatures also decreases.

In addition, due to the high velocity of the gas flow at the surface of the specified charge, the burning rate at the end of the charge increases, which leads to the transformation of the cylindrical checker into a conical one, and therefore to a decrease in the support surface of the charge, resulting in the destruction of the checkers and the engine loses its functionality. A similar phenomenon is most characteristic at extreme values of positive engine operating temperatures, when the mechanical characteristics of the fuel are significantly lower than under normal climatic conditions.

The objective of the invention is to increase the reliability of a solid fuel rocket engine with a charge of large elongation in a wide temperature range of application.

The solution of this problem is achieved by the method of ignition of the solid propellant rocket charge, including ignition of the igniter, distribution of its combustion products to the charge, heating of the surface of the charge and its subsequent ignition, in which the combustion products of the igniter located in the semi-enclosed cavity of the combustion chamber of the engine are initially directed to the front end of the charge and after ignition of a part of its surface organize the supply of the products of combustion of the igniter to the rear end of the charge, and after the combustion of the igniter, the product The combustion of the charge formed at the front end is passed through the cavity into the pre-nozzle volume of the engine.

The method is implemented by a solid propellant rocket engine containing a combustion chamber with a nozzle block, an igniter and a multi-cup charge with a support grate, in which a tube is divided into two cavities with a partition through the openings closed with a membrane on the support grate from the nozzle block side of the chamber, installed between the end of the septum and the end of the igniter, placed in the cavity facing the front end of the charge, while between the free end of the tube and the front bottom of the combustion chamber van annular passage area of which is selected from the condition

S _holes <S _can <S _tr ,

Where

S _can. - channel area;

S _holes - the total area of the holes of the partition;

S _tr - the cross-sectional area of the tube.

The presence of a tube fixed on the support grid from the nozzle block side coaxially with the chamber, divided into cavities by a partition with through holes, and the placement of the igniter of the required mass in a semi-closed cavity exclude direct contact of the igniter during combustion with thin-walled charge checkers when it is ignited, which reduces radial bending loads on charge checkers. Given that the cavity is constantly in communication with the front of the engine’s combustion chamber, the products of the igniter’s combustion, as its surface is connected to the combustion process, are constantly removed from the cavity, which reduces the pressure level in the cavity and reduces the mass of the structure. Opening holes in the partition after ignition of the end part of the surface of the charge, providing the supply of igniter products of combustion through them to the rear end of the charge, allows to reduce the axial pressure drop along the length of the blocks and to prevent the destruction of their supporting surface during ignition. Ensuring the flow of combustion products of charge after combustion of the igniter from the front end of the charge into the pre-nozzle volume of the engine through the cavity in which the igniter was previously located, reduces the consumption of combustion products through the cross section located at the support surface of the charge and the gas flow velocity at the surface of the charge. As a result, the burning rate of fuel at the supporting surface of the checkers is reduced, the decrease in the supporting surface of the charge, as well as the destruction of the charge at the beginning and end of the engine, is excluded, which increases the reliability of its operation and reduces the spread of output characteristics.

The presence of a membrane excludes the flow of the products of combustion of the igniter to the rear end of the charge until the ignition of the charge from the front end. The annular channel between the free end of the tube and the front bottom of the combustion chamber provides an even distribution of the products of combustion of the igniter along the cross section of the combustion chamber, thereby reducing lateral loads on the charge checkers. With the ratio of areas

S _holes <S _can <S _tr ,

Where

S _can. - channel area;

S _holes - the total area of the holes of the partition;

S _tr - the cross-sectional area of the tube.

the optimal mode of one-way flow of the products of combustion of the charge from the front end to the pre-nozzle volume of the engine after combustion of the igniter is ensured. The igniter can be made in the form of a sample of smoky gunpowder, placed in a glass of polymer material, the outer diameter of which is equal to the inner diameter of the tube. In this case, the membrane can serve as a housing of a glass made of a polymeric material, which will additionally allow fixing the igniter in the engine.

The invention is illustrated in graphic materials.

The drawing shows a diagram explaining the ignition method and the design of the engine that implements the specified method.

The solid fuel rocket engine contains a combustion chamber 1 with a nozzle block 2, an igniter 3 and a multi-cup charge 4. On the support grid 5 from the side of the nozzle block 2, a tube 6 is fixed coaxially with the chamber, inside of which a partition 7 is installed that separates the tube into two cavities. In the partition 7, holes 8 are made, closed by a destructible membrane 9. The igniter 3 is placed in the cavity 12 of the tube from the front of the front end of the charge and is fixed on its axis. An annular channel 10 is formed between the free end of the tube 6 and the front bottom of the combustion chamber. The igniter 3 is ignited from an initiating device 11 located opposite the igniter.

The proposed method is implemented as follows.

From the initiating device, for example, an electric igniter 11, the igniter 3, located in the cavity 12, is ignited. The combustion products of the ignitor through the annular channel 10 are fed to the front end of the charge 4 and ignite it. After ignition of the charge, the membrane 9 is destroyed, and the products of combustion of the igniter 3 through the openings 8 in the baffle 7 installed in the tube 6, enter the rear end of the charge 4 and ignite it. After combustion of the igniter 3, the products of combustion of the charge 4 flow from the front end through the cavity 12 and the holes 8 in the baffle 7 into the pre-nozzle volume, mix with the combustion products entering through the support grill 5 and are ejected through the nozzle block 2, creating engine thrust. The ratio of the products of charge combustion entering the pre-nozzle volume through openings 8 in the partition 7 and through the support grid 5 is determined as S opening _. / S _res , where S _res is the total area of the holes for the passage of gas in the grate.

The mass of the igniter, the geometric dimensions of the tube, the number of holes in the partition and the design parameters of the charge are determined in each case by calculation and are refined during the experimental development of the engine.

Thus, the proposed method of ignition of a solid propellant solid propellant rocket and a rocket engine for its implementation can improve the reliability of a solid fuel rocket engine with a large elongation charge in a wide temperature range of application.

Claims (2)

1. A method of igniting a solid propellant charge, including ignition of the igniter, spreading its combustion products to charge, heating the surface of the charge and subsequent ignition thereof, characterized in that the combustion products of the igniter located in the semi-enclosed cavity of the engine combustion chamber are initially sent to the front end of the charge and after the ignition of a part of its surface organize the supply of the products of combustion of the igniter to the rear end of the charge, and after the combustion of the ignitor, the products of the combustion of the charge formed at the front end, passes through the cavity in predsoplovoy engine size. 2. A solid propellant rocket engine containing a combustion chamber with a nozzle block, an igniter and a multi-cup charge with a support grill, characterized in that a tube divided into two cavities by a partition wall with through holes closed by a membrane is fixed to the support grille from the nozzle block side, installed between the end of the partition and the end of the igniter located in the cavity facing the front end of the charge, while between the free end of the tube and the front bottom of the combustion chamber tsevoy passage area of which is selected from the condition S _holes <S _can <S _tr , where s _can - channel area; S _holes - the total area of the holes of the partition; S _tr - the cross-sectional area of the tube.