JPH05321763A - Rocket engine having detachable ring nozzle - Google Patents

Abstract

PURPOSE:To prevent separation of the combustion gas in launching with a simple constitution, and achieve high expansion ratio in a simple manner at a high altitude. CONSTITUTION:A ring nozzle 11 consisting of a combustion chamber 1, a throat part 2, and an engine nozzle 3 furnished with the sealing property is connected to an outlet part 3a of the engine nozzle 3 of a rocket engine by explosion bolts 12 in a directly detachable manner. Under the atmosphere condition, separation of the combustion gas is prevented by functioning the ring nozzle 11 as a diffuser, and at a high altitude, the ring nozzle 11 is cut off to achieve the high expansion ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocket engine, and more particularly to a rocket engine with a detachable ring nozzle capable of preventing separation of a combustion gas flow under atmospheric pressure.

[0002]

2. Description of the Related Art Generally, a rocket engine, as shown in FIG. 4, burns a propellant in a combustion chamber 1 to generate a high-pressure gas in the combustion chamber, and expands the high-pressure gas through a throat section 2 and a nozzle 3. , Speed up the nozzle outlet 3a
It is ejected from the machine and its reaction produces thrust.
In order to realize a high speed in the nozzle 3, the throat portion 2 is narrowed down to a sufficiently small area so that the gas velocity when the combustion gas passes through the throat portion 2 becomes a sonic velocity. When the combustion gas that has passed through the throat portion 2 is expanded without being disturbed, the gas becomes supersonic, and the gas velocity also increases as the expansion ratio increases. This causes the nozzle of the rocket engine to generate a large thrust.

By the way, when the expansion ratio is increased to increase the thrust, the gas pressure at the nozzle outlet 3a becomes smaller, and the outside air pressure becomes higher than the injection gas pressure at the time of operation above the ground, so that the outside air becomes The jetted gas is compressed, and as shown in FIG. 5, the combustion gas 4 in the nozzle does not flow along the nozzle shape and is separated from the nozzle inner wall 3b.

This separation combustion gas flow is unstable and has adverse effects such as vibration of the engine and fluctuations in the heat flux to the nozzle wall surface, so separation is generally avoided. In addition, the following empirical formula is well known as the standard of peeling limit. P _i / P _a = (1.88M _i −1) ^−0.64 P _i : Static pressure at separation point P _a : Atmospheric pressure M _i : Mach number at separation point

On the other hand, the first stage of the rocket flies in the air until about 50 seconds after the launch, but it is common to fly in a vacuum after that. By the way, the total combustion time of the first stage of the H-I rocket is about 280 seconds, and that of the H-II rocket is about 280 seconds.
Since it is 350 seconds, only a part of the total combustion seconds of the first stage will burn in air. Therefore, the engine nozzle has a high expansion ratio as much as possible within the range where separation does not occur, resulting in performance deterioration under atmospheric pressure, but it is a good idea to increase the thrust in vacuum, that is, the specific impulse by making it overexpansion. Become.

[0006]

Conventionally, the following means have been considered as means for increasing the expansion ratio of the engine nozzle. (1) Method of increasing combustion pressure This method is the most widely used method at present. Although it is possible to make the engine compact, if the combustion pressure is increased, the thermal and strength of the engine components will be improved. Increased load, high development cost,
It also has the drawback of causing reliability problems.

(2) Extension nozzle system In this system, as shown in FIG. 6 (A), the extension nozzle 5 is evacuated immediately after the engine is ignited to a state of a low expansion ratio so that the atmospheric pressure in the sky is small. After that, (B) of FIG.
As shown in FIG.
It is a method of extending and increasing the expansion ratio.The characteristic of this method is that although the overall length is compact when the engine is ignited,
There is a drawback that the extension mechanism is complicated, and since the engine nozzle 3 and the extension nozzle 5 are connected to each other in the air, there is a problem that the sealing property at the connecting portion 7 between the two remains uneasy.

(3) Method of controlling boundary layer This method is a method of injecting another gas into the boundary layer in the vicinity of the wall surface of the engine nozzle or sucking the boundary layer, but the mechanism is complicated and it is possible to realize it. It is poor.

(4) Method of mounting another nozzle in the nozzle In this method, as shown in FIG. 7 (A), another internal nozzle 8 is provided in the engine nozzle 3 and, after reaching the sky, As shown in FIG. 7B, the internal nozzle 8 is separated, but there is a problem with the mechanism for separating the internal nozzle 8.
It is necessary to prevent the combustion gas flow after being cut off and having a high expansion ratio from flowing smoothly. Further, when the gas is disconnected, the gas flow expands rapidly, which may cause disturbance.

(5) Method using plug / nozzle This method is a method that has been proposed for a long time and is famous as a method that does not cause separation, but it is necessary to drastically change not only the nozzle but also the combustion chamber. However, it is said that there is a technical problem in cooling the combustion chamber, and it has not been put to practical use until now.

As described above, any of the conventionally proposed means for increasing the expansion ratio of the nozzle has a problem. The present invention has been made in order to solve the above problems of the conventional high expansion ratio increasing means for rocket engine nozzles, and prevents peeling at the time of launch with a simple structure and easily increases the expansion ratio in high altitude. The purpose is to provide a rocket engine that is made possible.

[0012]

In order to solve the above problems, the present invention provides a rocket engine in which a combustion chamber is provided with an engine nozzle through a throat portion, and a ring nozzle is provided at the exit portion of the engine nozzle. A rocket engine with a detachable ring nozzle is constructed by detachably sealing and directly coupling.

By providing the ring nozzle detachably at the engine nozzle outlet, the ring nozzle functions as a diffuser at the time of ignition on the ground, and the combustion gas flow is decelerated to increase the static pressure. The occurrence of separation of the combustion gas flow is prevented under atmospheric pressure. Further, by separating the ring nozzle after the rocket reaches the sky and does not cause separation, a high expansion ratio can be obtained and thrust can be increased.

[0014]

EXAMPLES Next, examples will be described. FIG. 1 is a schematic configuration diagram showing an embodiment of a rocket engine with a detachable ring nozzle according to the present invention. In the figure, 1 is a combustion chamber of a rocket engine, 2 is a throat part, and 3 is an engine nozzle, and these configurations are the same as those of the conventional one.
Reference numeral 11 denotes a ring nozzle according to the present invention, which has a tapered tube shape in order to have a function as a diffuser of combustion gas at a speed of sound or higher. Since this part should have heat resistance of about 20 to 30 seconds at most, it may be a radiation cooling method with a simple heat resistant coating (for example, seaside coating) on stainless steel or columbium alloy,
An ablative cooling method in which a simple ablative material is applied to an aluminum material may be used. The ring nozzle 11 is directly connected to the outlet portion 3a of the engine nozzle 3 by an explosive bolt 12 with a sealing property.

In the rocket engine of this structure, the area of the throat portion 2 is A _t , the Mach number of the combustion gas flow is M _t; The area of the position where separation occurs in the engine nozzle 3 when the ring nozzle is not provided is A _i , Mach number is M _i; Area of engine nozzle outlet is A _e , Mach number is M _e; Area of ring nozzle outlet 11a is A _RN , Mach number is M _RN , A _e > A _i > A It is set so that _RN > A _{t Me} > M _i > M _RN > M _t (= 1).

In the rocket engine thus constructed, at the time of lift-off, ignition is performed with the ring nozzle 11 coupled to the engine nozzle 3. At this time, the combustion gas flow from the combustion chamber 1 passes through the throat portion 2 and the engine nozzle 3
, The gas flow introduced into the ring nozzle 11 is decelerated and the static pressure increases. By reducing the nozzle expansion ratio by adding the ring nozzle 11, separation of the combustion gas flow under atmospheric pressure can be prevented, and lift-off can be performed in a state close to maximum expansion without lowering thrust.

After that, when the rocket reaches a high altitude and the engine nozzle 3 does not cause separation, the explosion bolt 12 is ignited and the ring nozzle 11 is separated as shown in FIG. By 3, the high expansion ratio can be obtained, the thrust can be increased, and a predetermined flight can be executed.

In the present invention, the total length of the engine is lengthened by the amount of the ring nozzle 11, but the nozzle separating mechanism by the explosion bolt 12 is simple and highly reliable, and the sealing property between the engine nozzle 3 and the ring nozzle 11 is high. Also about
It can be confirmed on the ground. Also, when the atmospheric pressure at the time of launch is high, by adding a ring nozzle, a low nozzle expansion ratio,
Since it is possible to prevent the thrust from decreasing due to the atmospheric pressure, it is possible to sufficiently compensate for the increase in the weight of the ring nozzle.

Further, since the combustion gas flow is a supersonic flow, the disturbance at the time of separating the ring nozzle does not affect the upstream, so that the disturbance at the time of separation can be reduced. In addition, by using a ring nozzle cooled with water or the like at the time of the ground burning test, it is possible to endure the burning test for a long time. Further, the vacuum thrust can be calculated only by measuring the static pressure on the inner wall surface of the ring nozzle, which eliminates the need for high-altitude combustion test equipment.

The vacuum thrust is calculated by measuring the static pressure on the inner wall surface of the ring nozzle 11 with a pressure gauge 13, as shown in FIG.
It can be calculated by the following formula. _{F = F M + ∫P RN dA} + ∫P a da = F M + ∫P RN da + P a A RN F: Vacuum thrust (ring status without nozzle) F _M: thrust measured (with ring nozzle) P _RN: Pressure on the inner wall of the ring nozzle P _a : Atmospheric pressure (normally regarded as constant) A _RN : Area of the ring nozzle outlet

[0021]

As described above on the basis of the embodiments,
According to the present invention, since the ring nozzle is detachably provided at the engine nozzle outlet, at the time of ignition on the ground, the ring nozzle functions as a diffuser, the combustion gas flow is decelerated, and the static pressure is increased. The occurrence of flaking of the combustion gas under atmospheric pressure is prevented. When it reaches the sky again,
By separating the ring nozzle, a high expansion ratio of only the engine nozzle is achieved and thrust can be increased.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a rocket engine with a detachable ring nozzle according to the present invention.

FIG. 2 is a diagram showing a mode when a ring nozzle is separated.

FIG. 3 is a diagram showing a test mode when a vacuum thrust is calculated by a ground test.

FIG. 4 is a cross-sectional view showing a configuration example of a conventional rocket engine.

FIG. 5 is a diagram showing a state where flaking of combustion gas occurs in a conventional rocket engine.

FIG. 6 is a diagram showing a conventional method of increasing the expansion ratio.

FIG. 7 is a diagram showing another conventional method for increasing the expansion ratio.

[Explanation of symbols]

 1 Combustion Chamber 2 Throat 3 Engine Nozzle 4 Combustion Gas Flow 5 Extension Nozzle 6 Actuator 7 Coupling 8 Internal Nozzle 11 Ring Nozzle 12 Explosion Bolt 13 Pressure Gauge

Claims (1)

[Claims] 1. A rocket engine in which an engine nozzle is provided in a combustion chamber through a throat portion, a ring nozzle is detachably sealed and directly coupled to an outlet portion of the engine nozzle, and a ring of a combustion gas flow is generated under atmospheric pressure. A rocket engine with a detachable ring nozzle, which is configured to prevent separation.