RU2517971C1 - Nozzle-free solid-propellant rocket engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: proposed engine comprises combustion chamber with front bottom, cylindrical part and rear end and charge with central channel secured to combustion chamber. Said charge consists of two tandem parts. Charge larger part is located nearby bottom and has cylindrical central channel. Charge smaller part is located nearby combustion chamber rear end and has the central channel. Central channel flow section area increases smoothly toward outlet cross-section and is made from fuel with combustion rate some 30÷50% smaller than that of the charge larger part. Smaller charge weight makes 2÷10% of the charge total weight.

EFFECT: higher efficiency of solid-propellant charge.

5 cl, 2 dwg

Description

The invention relates to rocket technology and can be used to create launch-booster stages for rockets with ramjet engines and in auxiliary solid propellant rocket engines.

Currently, in ramjet engines, the most common are designs with a plug-in start-and-run solid propellant rocket engine that is inserted into the ramjet combustion chamber, centered and fixed in it. After the end of the operation, the clamps are cut off and the solid-propellant rocket motor housing is pushed out through the ramjet nozzle by high-speed air pressure. According to this scheme, the start-up and launch stages of missiles with IPVRDZH “X-31” and “Mosquito” work. The starting and booster solid propellant rocket engine can be built into the ramjet combustion chamber and remain in it until the propulsion system is fully operational. These structural schemes do not allow the use of the entire volume of the combustion chamber and the volume loss is more than 4.5% -5%. From this drawback, the free starting-booster stage circuit with a solid fuel charge or attached to the wall of the ramjet combustion chamber is free. The world's first integral ramjet engine (IPVRD) of the Soviet 3M9 anti-aircraft missile has a separate TT charge armored on the outer surface and a firing nozzle.

In the development of this scheme, a charge was proposed that has an internal channel in the form of a cylinder with a profiled output section, which during the combustion process creates the effect of a flow-nozzle (Integrated ramjet solid propellant engines (Fundamentals of theory and calculation) / V.N. Aleksandrov, V.M.Bytskevich, V.K. Verkholomov, etc. - M. / IKC "Akademkniga", 2006, p.191-193).

In the cylindrical part of the channel, solid fuel combustion products are accelerated to the speed of sound due to the supply of mass and to supersonic speed in the profiled part of the channel. Such a solid propellant rocket motor does not have a rigid nozzle and is called a non-nozzle solid propellant rocket motor (BSDRTT). Using it as a starting-booster stage in the ICREP is considered very promising.

The advantages of this design are:

- lack of discharged elements during the flight;

- simplicity of design and, as a consequence, its cheapness;

- high mass excellence and fuel fill ratio.

The disadvantages of BSRTT include:

- lower average integral specific impulse of engine thrust in comparison with specific impulse of solid propellant rocket engine with nozzle;

- the pressure diagram in the chamber of the BSRDTT is substantially uneven (degressive) in operating time, which increases the mass of the engine structure.

The objective of the invention is to increase the specific impulse of the thrust BSRDTT and reduce the degressiveness of the pressure-time relationship, that is, the maximum and minimum pressure in the combustion chamber. In addition, this invention will increase the specific thrust impulse BSRDTT by 5% ÷ 10% compared with the analogue due to the reduction of the height of the minimum cross section at the outlet of the channel.

The technical result consists in increasing the geometric degree of expansion of the flow in the output section by reducing the height of the critical section of the channel, which increases the efficiency of use of the charge of solid fuel.

The technical result is achieved by the claimed design of a nozzle-free rocket engine of solid fuel. The non-fuel solid fuel rocket engine contains a combustion chamber with a front bottom, a cylindrical part, a rear end and a charge attached to the combustion chamber with a central channel. The charge is made of two sequentially arranged parts. Most of the charge located at the front bottom is made with a cylindrical central channel. A smaller part of the charge is located at the rear end of the combustion chamber, equipped with a central channel, the area of the passage section of which gradually increases towards the output section, while the geometric degree of expansion of the channel (nozzle) increases. In addition, this part of the charge is made of fuel having a burning rate 30% ÷ 50% lower than the burning rate of most of the charge, and its mass is 2% ÷ 10% of the total mass of the charge. This ratio of the characteristics of the charges will allow to increase the specific impulse of the engine thrust and reduce the degressiveness of the engine pressure diagram.

The use of a charge from a slow-burning fuel placed at the outlet of the channel helps to reduce the height of the output section of the channel and, as a result, increase the average integral pressure of the combustion products during operation.

Estimates made using the Bori formula (dependence of the pressure in the chamber on the characteristics of the fuel) show that a decrease in the burning rate of the charge located at the rear end of the combustion chamber by ≈30% with a degree in the combustion law ν equal to 0.4 leads to increase the average integral pressure by 50%, which reduces the effect of a pressure drop in the combustion chamber over time. Moreover, this effect increases with an increase in ν. Estimates of the specific impulse BSRDTT for this option show that it is possible to increase the specific impulse of thrust by ≈10%.

In addition, the inner channel of the smaller part of the charge can be made in the form of a truncated cone with a base located at the rear end of the combustion chamber, or in the form of a supersonic part of the Laval nozzle, which makes it possible to further increase the specific impulse of thrust due to a decrease in scattering losses [Gas-dynamic and thermophysical processes in solid propellant rocket engines / AM Hubertov, V.V. Mironov, D.M. Borisov et al .; Ed. A.S. Koroteeva. M .: Engineering, 2004]. The increase in specific impulse is estimated at 2% ÷ 4%.

In addition, the interface between the larger and smaller charges is either a conical surface, the generatrix of which is perpendicular to the generatrix of the nozzle contour, for the conical central channel of the smaller part of the charge, or a conical surface, which is perpendicular to the tangent to the generatrix of the central channel at a point belonging to the circle forming the critical section, for the central channel of the smaller part of the charge in the form of a supersonic part of the Laval nozzle. This gives an additional opportunity to increase the specific impulse of thrust due to the formation of an input cone in the nozzle portion of the charge channel.

The invention is illustrated by drawings.

Figure 1 presents a General view of the proposed design BSRTT, where the Central channel of the smaller part of the charge is made in the form of a truncated cone.

Figure 2 presents a General view of the proposed design of the solid propellant rocket motor, where the central channel of the smaller part of the charge is made in the form of a supersonic part of the Laval nozzle.

The engine (Fig. 1, 2) consists of a combustion chamber 1, in which a solid fuel charge is installed, fastened with its walls, consisting of two parts 2, 3. Part 2 is a solid fuel charge with a high combustion temperature, located at the front bottom 7, and part 3 - the charge of solid fuel with a low combustion temperature, located at the rear end 8, has a circuit 4 (figure 1), the area of the passage section of which gradually increases towards the outlet, or a profiled supersonic part 4 (figure 2). The interface between the larger and smaller charges is a conical surface 5 (Fig.1, 2). Solid fuel is ignited by an igniter 6.

The engine operates as follows. After the ignition device 6 is installed in the front bottom 7 of the combustion chamber 1, the parts of the charge 2 and 3 are ignited. The combustion products of the part of the charge 3 form a stream of low-temperature combustion products, and the burning charge 2 creates a high-temperature stream.

Currently, BSRDTT models have been manufactured and experimental studies are being conducted to determine the effectiveness of the proposed design options.

Claims (5)

1. A fuel-free solid fuel rocket engine, consisting of a combustion chamber with a front bottom, a cylindrical part, a rear end and a charge attached to the combustion chamber with a central channel, characterized in that the charge consists of two parts arranged in series, with most of the charge located at the front bottom, made with a cylindrical central channel, and a smaller part of the charge is located at the rear end of the combustion chamber, has a central channel, the passage area of which is gradually increasing tsya toward the exit section, and is made of a fuel having a burning rate of 30% ÷ 50% smaller than the rate of combustion most of the charge and mass of the smaller portion of the charge was 2% ÷ 10% of the total charge weight. 2. The non-fuel solid fuel rocket engine according to claim 1, characterized in that the central channel of the smaller part of the charge is made in the form of a truncated cone with a base located at the rear end of the combustion chamber. 3. The non-fuel solid fuel rocket engine according to claim 1, characterized in that the central channel of the smaller part of the charge is made in the form of a supersonic part of the Laval nozzle with a base located at the rear end of the combustion chamber. 4. The non-fuel solid fuel rocket engine according to claim 2, characterized in that the interface between the larger and smaller parts of the charge is made in the form of a conical surface, the generatrix of which is perpendicular to the generatrix of the central channel of the smaller part of the charge. 5. The non-fuel solid-fuel rocket engine according to claim 3, characterized in that the interface of the larger and smaller parts of the charge is made in the form of a conical surface, the generatrix of which is perpendicular to the smaller part of the charge tangent to the generatrix of the central channel at a point belonging to the circle forming the nozzle critical section Laval.

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