JPS5925110B2 - Rocket motor internal pressure vibration inducing device - Google Patents

Description

[Detailed description of the invention] The present invention relates to an internal pressure vibration inducing device for a rocket motor.

During the steady combustion of solid propellant in a rocket motor, the internal pressure suddenly increases irregularly and a combustion state accompanied by vibration (hereinafter referred to as internal pressure vibration) occurs. It is thought to be caused by changes in the natural frequency, etc., and is generally induced by the passage of solid debris such as restrictors.

If such internal pressure vibration exceeds the allowable limit, it will lead to the worst accident of destroying the rocket motor. Therefore, various conditions are applied during steady combustion of the propellant to check whether internal pressure vibration is induced, and this is considered in the design. It is important to provide documentation.

Conventionally, such an internal pressure vibration inducing device is a plastic case in which black gunpowder and small metal pieces as bullets are enclosed in the inner hole of a solid propellant or in the propellant, which exhibits a steady combustion curve A as shown in Fig. 1. A type was used in which a black powder was installed or buried, and black powder was detonated at the same time as the propellant was ignited or at a point where combustion progressed, causing small pieces of metal to be released and thereby inducing internal pressure vibrations.

However, even if it is possible to measure the internal pressure oscillations (curve B in Figure 1) using such a device, the main cause of the internal pressure oscillations is (a) the detonation pulse of black powder, or (b) the explosion of small metal pieces. It is difficult to determine whether this is due to release or (-9) an inherent defect in the propellant, and furthermore, it is difficult to set the detonation timing of black powder; (E) In order to estimate the motion path of the small metal piece ((therefore, the relationship with the internal pressure vibration cannot be clarified),
There was a drawback.

The present invention has been made in view of the above-mentioned point, and the first aspect thereof is
The purpose of this invention is to eliminate the above-mentioned drawbacks, and its second purpose is to provide an internal pressure vibration inducing device that can clearly control the conditions under which internal pressure vibration is induced. The objective is to obtain data that can predict internal pressure vibrations and use this data as design material for setting the specifications of the rocket motor.

Further, the present invention is characterized by supplying working gas from a rapid gas generator to a piston facing the projectile, driving the piston with the working gas, and transferring only the projectile from the injection tube using the combustion gas of the rocket motor. The purpose is to inject the liquid into the liquid and release it from the nozzle through a predetermined path.

An embodiment of the present invention will be described below with reference to the drawings.

Reference numeral 1 denotes a rocket motor mounted on a test stand (not shown), and this rocket motor 1 is loaded with an internal end-face combustion type solid propellant grain 4 having, for example, V-strifters 2 and 3 attached to its outer periphery and front end face, respectively. The motor case 5 has a front end plate 6 screwed onto the front part of the motor case 5.

The inner hole 4 of the propellant grain 4 is located on the axis of the front end plate 6.
A screw hole T communicating with a is formed, and an injection tube 9 holding a bullet 8 is screwed into this screw hole T.

The bullet 8 is formed, for example, in the shape of a right cylinder, and its outer diameter and length can be set to various values.

A cylinder 10 is screwed onto the front end of the injection tube 9 that protrudes outward from the front mirror plate 6, and within the cylinder 10 is a rod 1 that faces the bullet 8 and is in contact with the bullet 8 on its rear end surface.
A piston 12 having a piston 1 is slidably provided.

13 is a gas vent hole provided in the cylinder 10.

A rapid gas supply device 16 is screwed to the front end of the cylinder 10 via a connecting tube 15 fitted with a seal ring 14 on the outer periphery. Connected to programming timer.

As the rapid gas generator 16, specifically, a gas generator that instantaneously generates high-pressure gas by burning black powder or the like is used.

A free volume passage 17 for applying high pressure working gas generated by a rapid gas supply device 16 to the front end surface of the piston 12 is formed inside the connecting tube 15, and the volume of this free volume passage 17 is varied in various ways. This allows the driving speed of the piston 12, that is, the ejection speed of the bullet 8, to be changed.

The injection tube 9, bullet 8, cylinder 10, and piston 1 described above
2. The connecting tube 15 and the rapid gas supply device 16 collectively constitute an internal pressure vibration inducing device 18.

A nozzle holder 19 is screwed onto the rear part of the motor case 5, and a nozzle 21 made of graphite material or the like whose nozzle throat portion is closed by a nozzle closure 20 is fixed to this nozzle holder 19.

An igniter 22 is installed in the inner hole 4a of the propellant grain 4, and the igniter 22 and the programming timer (not shown) are connected via a covered conductor 23.

The front end plate 6 has a pair of pressure transmission holes 25 and 26 each opening into the combustion chamber 24, and these pressure transmission holes 25.
．． Connection openings 27 and 28 are provided which communicate with 26, respectively.

The connection opening 27 has a strain gauge type pressure sensor 29 for measuring the internal pressure Pc of the combustion chamber 24, and the connection opening 28 has, for example, a piezo type pressure sensor 30 for measuring internal pressure vibrations of the combustion chamber 24. It is worn.

These pressure sensors 29 and 30 are connected to an unillustrated measurement control panel, such as a strain meter, data encoder, etc., via unillustrated lead wires, and this measurement control panel is connected to an unillustrated I/O panel.
It is connected to the programming timer (not shown) via the J-conductor.

Next, the operation of one embodiment of the present invention will be explained.

A predetermined time before an ignition signal is issued to the igniter 22 from a programming timer (not shown), for example approximately 1 second, this programming timer sends a command signal to the measurement control panel via the lead wire to activate the measurement control panel. let

Therefore, from this point on, the output signals from the pressure sensors 29, 30 are input to the measurement control panel and recorded.

Next, in FIG. 1, at θ seconds, an ignition signal is sent from the programming timer to the igniter 22 via the covered conductor 23, and the igniter 22 is ignited.

The ignition of the igniter 22 causes the combustion chamber 24 to be filled with high-temperature combustion gas under high pressure.

For this reason, the combustion surface of the propellant grain 4, that is, the inner hole 4
The inner surface a and the rear end surface are ignited, and the nozzle closure 20 is blown off from the nozzle 21.

Then, the propellant grains 4 begin steady combustion by ignition.

At this time, the steady combustion curve A picked up by the pressure sensor 29 is shown by a solid line in FIG.

When a predetermined period of time, for example T3 seconds, has elapsed from 0 seconds, a signal is sent from the programming timer to the rapid gas supply device 16 via the lead wire.

Therefore, the black powder or the like in the rapid gas supply device 16 is combusted, and high-pressure working gas is instantaneously generated.

This working gas is rapidly supplied to the rear end surface of the piston 12 through the free volume passage 17, and the working gas drives the piston 12 inside the cylinder 10 toward the bullet 8 at high speed.

Therefore, the elastic material 8 is ejected from the injection tube 9 into the combustion gas filling the combustion chamber 24, passes through the combustion gas, and enters the nozzle 2.
Jump out from 1.

At this time, if internal pressure oscillations were likely to be induced, the propellant grains 4, which had been burning while drawing a steady combustion curve A, would become as shown in Figure 1 as the projectile 8 passes through the combustion gas. The fuel burns while drawing the internal pressure oscillation curve B shown in FIG.

In addition, in FIG. 1, a curve E indicated by a broken line is drawn when the propellant grain 4 continues steady combustion (steady combustion curve,
The area between the curve C and the curved line indicates the amplitude range of internal pressure vibration, which is picked up by the pressure sensor 29, and the internal pressure vibration (curve B) is picked up by the pressure sensor 30, which is transmitted via the lead wire. It is sent to the measurement control panel and recorded.

In order to determine whether a propellant grain designed using such an internal pressure vibration inducing device is likely to induce internal pressure vibrations, it is determined as follows.

First, for example, 10 grains each of propellant grains of specification A, which had no problems in the past, and propellant grains of specification B, which are newly designed, are prepared.

On the other hand, the bullets are made of steel and have a right cylindrical shape, and a bullet of 5φ×51 mm is prepared as a bullet of C specification, and a bullet of 10φ×101 mm is prepared as a bullet of D specification.

Next, such projectiles of specifications C and D are fired into the combustion gas of propellant grains of specifications A and B, respectively, after 15 hours have elapsed from O seconds to T1, T2, T3, and T4.15.

The results are shown in the table below, where the X mark in the table represents the case where internal pressure vibration did not occur, and the O mark in the table represents the case where internal pressure vibration occurred.

In the above table, if the A specification grain is 1 D specification bullet,
When fired after 5 hours, internal pressure oscillations occurred, but this grain had no problem in practical use in the past.

On the other hand, for the B specification grain, after 15 hours for the C specification bullet, and for the D specification bullet, T3, T4.1
Internal pressure oscillations occurred in each firing after 5 hours had elapsed.

In other words, the B specification grains according to the new design are determined to be likely to induce internal pressure vibrations, and indicate that further consideration is required regarding the shape of the inner hole, etc.

As explained above, when ejecting a projectile using a rapid gas generation source such as gunpowder, the present invention does not release the generated gas into the combustion gas of the propellant (it is possible to simply eject only the projectile). , the test conditions are extremely simplified and it is possible to perform various comparative tests by changing these conditions in various ways.
It is possible to provide simple and clear design data regarding the induction of internal pressure vibrations when designing new propellant grains.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing a combustion curve of a propellant, and FIG. 2 is a sectional view showing an embodiment of an internal pressure vibration inducing device for a rocket motor according to the present invention.

1 is a rocket motor, 8 is a bullet, 9 is an injection tube, 12 is a piston, 16 is a rapid gas generator, and 18 is an internal pressure vibration inducing device.

Claims (1)

[Claims] 1. A device for inducing internal pressure vibrations by passing elasticity through the combustion gas of a rocket motor, which includes an injection tube that maintains elasticity, a piston provided opposite the elasticity, and a device that rapidly supplies working gas to the piston. What is claimed is: 1. A device for inducing internal pressure vibrations in a rocket motor, comprising: a rapid gas generating device for supplying a rapid gas;