JPS6035548B2 - Rocket motor internal pressure vibration suppression method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for suppressing internal pressure vibration of a rocket motor.

The phenomenon in which the internal pressure suddenly increases irregularly during steady combustion of the solid propellant in a rocket motor, resulting in a combustion state accompanied by vibrations (hereinafter referred to as internal pressure vibration) is a phenomenon unique to the air column due to changes in the shape of the propellant's internal pores. It is said to be caused by changes in vibration frequency, etc., and is generally triggered by the passage of solid debris such as a rhinoceros restrictor.

If such internal pressure vibration exceeds the permissible limit, it will lead to the worst case scenario of destruction of the rocket motor, so it is necessary to suppress internal pressure vibration at the initial stage of occurrence. This invention was made in view of this need, and aims to reduce the amplitude of internal pressure oscillations by injecting pressure gas into the combustion chamber at valleys where the pressure of internal pressure oscillations is low, thereby suppressing internal pressure oscillations. The purpose is to do so.

The present invention will be explained below based on the drawings. FIGS. 1 and 2 are diagrams showing an embodiment of an apparatus for carrying out the present invention. First, to explain the configuration, 1 is a motor case of a rocket motor. Inside this motor case 1, an internal combustion type solid propellant 2 is loaded, and this solid propellant 2 is driven by an igniter (not shown). ignited. The holder 3 is screwed and fixed to the motor case so as to face the inner hole 2a of the solid propellant 2, and as shown in detail in FIG. A pressure sensor 5 as a vibration pressure pickup is fixed to the other end of the pressure guide hole 4 as shown in FIG. Therefore, the pressure sensor 5 mainly picks up the component in the machine axis direction (longitudinal vibration) of the internal pressure vibration. A plurality of initiators 6 serving as pressure gas generating means are housed within the holder 3. 7
The ignition ball of the finisher 6 is a lead wire 8 that ignites the ignition ball 7.

A plurality of stepped holes 9 are formed in the holder 3 so as to face one end of each finisher 6, and these stepped holes 9 are suitable for passage 101, respectively.

11 is a pressure gas injection hole formed in the holder 3, and this injection hole 11 connects the passage 10 and the combustion chamber 12.

A stepped closure 13 is provided at the other end of each stepped hole 9.
are fixed with adhesive, respectively, and each closure 13 prevents the combustion gas of the rocket motor or the combustion gas of another initiator 6 from acting on the initiator 6 when fixed,
When the initiator 6 burns, the combustion gas moves in the stepped hole 9 toward one end, and the combustion gas flows into the passage 1.
01 is allowed to flow out. Again in Figure 1, I
Reference numeral 4 denotes a control section for controlling the combustion of the initiator 6, and this control section 14 has an amplifier circuit 16 connected to the pressure sensor 5 via a signal cable 15. (an electrical signal corresponding to the amplitude of the longitudinal vibration) is amplified. Reference numeral 17 denotes a band-pass filter that receives the signal output from the amplifier circuit 16, and this band-pass filter 17 functions to extract the fundamental wave component (first-order vibration component) of the signal.

18 is a comparator that receives the signal output from the bandpass filter 17, and this comparator 18 compares the signal with a set level and emits a pulse every time the signal exceeds the set level.

Reference numeral 19 denotes a stepper that receives the pulse signal output from the comparator 18, and this stepper 19 counts the pulse signal and generates a stepped signal voltage proportional to the number of counts.

The delay circuit 20 is a delay circuit that receives the signal voltage output from the stepper 19, and this delay circuit 20 emits a pulse signal every time the level of the signal voltage from the stepper 19 rises and a certain period of time has elapsed since the rise.

21 is a power distributor that receives the signal from the delay circuit 20;
1 connects cable 2 every time it receives a signal from delay circuit 20.
2. Send a signal for ignition to each initiator 6 one after another via the lead wire 8.

Next, the action will be explained.

First, when the solid propellant 2 is ignited by the ignitor, the solid propellant 2 starts steady combustion.

When internal pressure vibration (longitudinal vibration) occurs during this steady combustion, this internal pressure vibration is transmitted to the pressure sensor 5 through the pressure guiding hole 4, and the pressure sensor 5 sends a voltage signal corresponding to this internal pressure vibration to the amplifier circuit 16. The amplifier circuit 16 converts this signal into a third
After amplification as shown in figure a, bandpass filter-1
The bandpass filter 17 extracts only the fundamental wave component of this signal and sends it to the comparator 18' as shown in FIG. 3b. The comparator 18 compares the signal with a set level shown in broken lines in FIG. 3b, and sends a pulse signal to the stepper 19 as shown in FIG. 3c each time the signal exceeds the set level. The stepper 19 counts this pulse signal and sends a stepwise signal voltage proportional to the number of counts as shown in FIG. 3d to the delay circuit 20' every two pulses in this case. Each time the level of this signal rises, the delay circuit 20 controls the third
A pulse signal as shown in Fig. e is sent to the power distributor 21. Here, when a certain period of time has elapsed since the signal voltage from the stepper 19 increased, it means when the internal pressure vibration reaches the valley, that is, when the vibration pressure becomes the lowest or near it. be. Since longitudinal vibration is a type of air column vibration, its frequency can be calculated based on the length of the propellant inner hole 2a, and in addition, in a rocket motor combustion test, for example, a shot is injected into the inner hole 2a. The delay time can be set in advance. Every time the power distributor 21 receives the pulse signal, it sends a signal to each initiator 6 one after another via the cable 22 and the lead wire 8, and ignites the ignition ball 7 to cause the initiator 6 to burn. for example,
If the first pulse signal shown in FIG. 3e is sent by the power distributor 21 to the initiator 6 shown in the upper part of FIG. 2, the initiator 6 will burn and the combustion gas will move the closure 13 toward one end. As a result, high-pressure combustion gas is ejected into the combustion chamber 12 of the motor case 1 via the stepped hole 9, the passage 10, and the injection hole 11, and instantaneously increases the pressure in the combustion chamber. In other words, the valley of the pressure vibration is lifted and the self-excitation enhancement effect is suppressed. Next, the third e
When the second pulse signal shown in the figure is sent by the power distributor 21 to another initiator 6 shown in the lower part of FIG. , the amplitude of the pressure vibration becomes smaller. By injecting the combustion gas of the initiator 6 into the combustion chamber 12 one after another, the internal pressure vibration is suppressed and attenuated, and finally the pulse signal is no longer output from the comparator 18, and the initiator 6 also does not burn. . Note that the initiators 6 are burned one after another until the internal pressure vibration is suppressed, and the number of initiators 6 may be one or two or more. Furthermore, when the internal pressure vibration occurs again, the remaining initiators 6 are burned one after another in the same way as described above. Note that when the internal pressure vibration occurs again, the signal transmission is skipped to the initiator 6 that has already finished combustion.
It is desirable to use a power distributor 21 that sends the first pulse signal output from the delay circuit 20 to the initiator 6 that has not yet burned.

As explained above, according to the present invention, pressure gas is injected into the combustion chamber at the valley where the oscillating pressure is low to reduce the amplitude of the internal pressure oscillation, thereby quickly damping the internal pressure oscillation. Accidents such as destruction of the rocket motor will not occur.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic overall view showing an embodiment of a device for implementing the method for terminating internal pressure vibration of a rocket motor according to the present invention, FIG. 2 is a sectional view of a holder, and FIG. Figure e is a graph showing each signal state in the control section. 2...Solid propellant, 6...Initiator, 12...Combustion chamber, 14...Control unit. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. The internal pressure of a rocket motor characterized in that when internal pressure oscillations occur during operation of the rocket motor, pressurized gas is instantaneously injected into the combustion chamber to reduce the amplitude when the internal pressure oscillations reach a trough. Vibration suppression method.