CN115045778A - Measurement method for simulating acoustic-solid coupling response characteristic of solid rocket engine - Google Patents

Abstract

The invention provides a measurement method for simulating the sound-structure coupling response characteristics of a solid rocket motor. The rubber material is used to simulate the propellant, so that the sound-structure coupling response characteristics of the rocket motor can be effectively studied on the premise of ensuring the safety of the test, and the test cost is low. Features; by designing the main body fixing component, the support frame and spring components are used to hoist the shell on the test bench to reduce the influence of the restraint of the support frame on the vibration characteristics of the test model, and the shell is "relatively free" hoisted , to accurately simulate the free boundary conditions of the rocket engine at work, so that it can be verified experimentally that structural oscillations can indeed cause pressure oscillations inside the combustion chamber under suitable conditions, and a more accurate transfer of structural oscillations to the internal pressure of the combustion chamber can be obtained. function and the transfer function of the pressure oscillations in the combustion chamber to the engine structure oscillations.

Description

A Measurement Method for Simulating Acoustic-Structure Coupling Response Characteristics of Solid Rocket Motors

technical field

The invention belongs to the technical field of solid rocket motors, and particularly relates to a measurement method for simulating the acoustic-structure coupling response characteristics of solid rocket motors.

Background technique

In recent years, the multiple unstable combustion phenomena of solid rocket motors are mostly in the middle and late stages of engine operation, especially when the thickness of the grain in the combustion chamber becomes smaller and the thickness of the engine shell is on the same order of magnitude, it suddenly occurs. Unstable combustion, but in the early stage of work, it is more stable. This is probably due to the fact that the pressure oscillation of the gas in the combustion chamber and the shell vibration are directly coupled to each other due to the reduction of propellant in the later stage of the work, which plays a resonance effect, thus forming a positive feedback, which further strengthens the oscillation of the pressure in the combustion chamber, and then Severe unstable combustion occurred at the end of the work, leading to the failure of the mission. Therefore, it is urgent to use an experimental method to determine the coupling effect between the acoustic cavity of the combustion chamber and the structural solid.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a measurement method for simulating the sound-structure coupling response characteristics of a solid rocket motor, which can accurately simulate the free boundary conditions of the rocket motor during operation.

A measurement method for simulating the sound-structure coupling response characteristics of a solid rocket motor, comprising:

The solid rocket motor combustion chamber is simplified into a cylindrical tube cavity with both ends open as the casing (4); according to the pouring form of the propellant in the solid rocket motor combustion chamber, the same structure and the same structure are arranged on the inner surface of the casing (4). Rubber of the same thickness to simulate propellant (8);

The housing (4) is installed on the test bench (10), and a sound source is provided at each end of the housing (4);

A plurality of sound pressure sensors are arranged along the axial direction inside the casing (4), and a plurality of acceleration sensors are respectively arranged on the inner and outer sides of the casing (4);

Turn on the sound source, the acceleration sensor will record the vibration information of the casing (4) and the sound pressure signal recorded by the sound pressure sensor as the output signal of this test;

The openings at both ends of the casing (4) are closed, and a signal generator is used to generate a white noise signal, which acts on the outer wall of one end of the casing (4) as an input signal; the vibration information and sound of the casing (4) recorded by the acceleration sensor The sound pressure signal recorded by the pressure sensor is used as the output signal of this test;

The data collected from the above two tests are processed to obtain the transfer function from the structure oscillation to the internal pressure of the combustion chamber and the transfer function from the pressure oscillation in the combustion chamber to the engine structure oscillation, which are used to analyze the acoustic-structure coupling response characteristics of the solid rocket motor.

Preferably, two main body fixing assemblies (5) are used to install the housing (4) on the test bench (10);

The main body fixing assembly (5) includes a support frame (51), two sets of spring assemblies and two second springs (57);

The support frame (51) is a hollow structure, and the casing (4) can pass through the middle of the support frame (51); four evenly distributed hanging points are arranged on the same circumference of the outer wall of the casing (4);

The spring assembly includes an adjusting screw (52), a nut (53), a tension sensor (54) and a first spring (55); the upper end of the adjusting screw (52) passes through the through hole of the support frame (51) and is tightened by the nut (53) , the lower end is connected to one end of the tension sensor (54), the other end of the tension sensor (54) is connected to one end of the first spring (55), and the other end of the first spring (55) is connected to the hanging point of the housing (4); The two first springs (55) of the two spring assemblies are respectively connected to the upper suspension points on the housing (4);

One end of the two second springs (57) is connected to the inner wall of the support frame (51), and the other end is connected to the two hanging points at the lower part of the housing (4);

The pulling forces of the first spring (55) and the respective opposite second springs (57) in the two spring assemblies are on the same straight line, and the two formed straight lines are perpendicular to each other.

Preferably, two mounting brackets (56) are fixed on the inner wall of the support frame (51), and the second spring (57) is connected to the support frame (51) through the mounting brackets (56).

Preferably, the main body fixing assembly (5) is symmetrically fixed on the test bench (10) with respect to the center of the casing (4).

Preferably, the main body fixing assembly (5) is fixed and supported by a triangular support frame (6).

Preferably, the shell (4) is made of structural steel.

The present invention has the following beneficial effects:

The invention provides a measurement method for simulating the sound-structure coupling response characteristics of a solid rocket motor. The rubber material is used to simulate the propellant, which can effectively study the sound-structure coupling response characteristics of the rocket motor under the premise of ensuring the safety of the test, and has the advantages of low test cost. specialty;

By designing the main body fixing component, the support frame and spring components are used to hoist the shell on the test bench to reduce the influence of the restraint of the support frame on the vibration characteristics of the test model. The free boundary conditions of the rocket engine during operation, so that it can be verified experimentally that the structural oscillation can indeed cause the pressure oscillation inside the combustion chamber under suitable conditions, and a more accurate transfer function from the structural oscillation to the pressure inside the combustion chamber and combustion can be obtained. Transfer function of chamber pressure oscillations to engine structural oscillations.

Description of drawings

Figure 1(a) is a schematic diagram of a measuring device for simulating the sound-structure coupling response characteristics of a solid rocket motor according to the present invention;

Figure 1(b) is a schematic structural diagram of the support structure and the spring hoisting housing;

Figure 2 is a schematic diagram of the distribution of the sound pressure sensor in the housing;

FIG. 3 is a schematic diagram of the measurement method.

Among them, 1- three-coordinate sliding table; 2- speaker shell; 3- tweeter and woofer; 4- shell; 5- main body fixed component; 6- triangle support frame; 7- movable support; 8- propellant; 10- test 51-support frame; 52-adjustment screw; 53-nut; 54-tension sensor; 55-spring assembly; 56-installation bracket; 57-second spring assembly.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

According to the actual situation of the solid rocket motor, the combustion chamber is simplified into a cylindrical tube cavity with openings at both ends as the shell 4, and the openings at both ends of the shell 4 are sealed. In order to simulate the real solid rocket motor, according to the pouring form of the propellant in the combustion chamber of the solid rocket motor, the same structure and the same thickness of rubber are arranged on the surface of the shell 4 to simulate the propellant 8, and then build a sound Setup for solid-coupling experiments.

The present invention uses rubber material to simulate the propellant 8, because the actual propellant is a pyrotechnic product and has the characteristics of flammability and explosion. For the safety of the test, a rubber material with similar physical parameters needs to be used instead. Although the physical parameters of the rubber sold on the market are different from the parameters of the actual propellant, the elastic modulus of the two is still in the same order of magnitude, and the difference is still several orders of magnitude compared with the elastic modulus of the engine casing. Therefore, commercially available rubber is used instead of the propellant. At the same time, the purpose of this experiment is to explore the transmission law of vibration excitation after passing through two layers of materials with large differences in mechanical properties, and this is the case in the combustion chamber of a solid rocket motor. Therefore, the materials used in the experiment can guarantee the same law as long as the difference in elastic modulus is not significantly different from that of the actual solid rocket motor combustion chamber in order of magnitude. Therefore, the experiment will use structural steel to machine the shell and replace the propellant with rubber.

The specific test steps are as follows:

(1) Placement of the test piece

As shown in FIGS. 1( a ) and 1 ( b ), the housing 4 is mounted on the test bench 10 by two main body fixing assemblies 5 , and the two main body fixing assemblies 5 are fixed to the test bench symmetrically with respect to the center of the housing 4 10, and are respectively fixed and supported by a triangular support frame 6, the main body fixing assembly 5 includes a support frame 51, two sets of spring assemblies and two second springs 57;

The support frame 51 is a hollow structure, and the shell 4 can pass through the middle of the support frame 51; four evenly distributed hanging points are arranged on the same circumference of the outer wall of the shell 4;

The spring assembly includes an adjustment screw 52, a nut 53, a tension sensor 54 and a first spring 55; the upper end of the adjustment screw 52 passes through the through hole of the support frame 51 and is tightened by the nut 53, and the lower end is connected to one end of the tension sensor 54, and the other end of the tension sensor 54. One end is connected to one end of the first spring 55, and the other end of the first spring 55 is connected to the hanging point of the housing 4; the two first springs 55 of the two spring assemblies are respectively connected to the upper hanging point of the housing 4 ;

One end of the two second springs 57 is connected to the inner wall of the support frame 51, and the other end is connected to the two suspension points at the lower part of the housing 4; wherein, two mounting brackets 56 are fixed on the inner wall of the support frame 51, and the second spring 57 is attached to the support frame 51 by means of mounting brackets 56 .

The pulling forces of the first spring 55 and the respective opposite second springs 57 in the two spring assemblies are on the same straight line, and the two straight lines formed are perpendicular to each other, the springs can effectively reduce the rigid constraint of the support frame 51 on the housing 4, The influence of the restraint of the support frame 51 on the vibration characteristics of the test model is reduced. As a result, the shell 4 is "relatively free" to be lifted, simulating the free boundary condition of the rocket engine when it is working, but it cannot achieve a completely free boundary on the ground, so it is called the "relatively free" boundary condition.

(2) The arrangement of the sensor.

A certain number of sound pressure sensors are placed inside the housing 4 along the axial direction to measure the pressure oscillation data excited by the vibration of the sound source. Figure 2 shows the location distribution of the sound pressure sensors (the number and arrangement of the sensors will be based on the to be modified according to actual needs). The sensitivity of the sound pressure sensor is 50mv/pa, and the range is 20-146db. Taking the 2m-long housing 4 as an example, a certain number of acceleration sensors are installed on the inside and outside of the housing 4 along the busbar. The number and arrangement of the sensors will be discussed later. Adjust according to actual needs in the experiment. The position of the acceleration sensor can be placed through the calculation of the standing wave equation. The position of the measuring point should not be placed at the position of the vibration node, and try to choose a position with a large amount of deformation, otherwise the measured result will be very small, which will make the measurement The precision of the results is reduced.

(3) Structural response experiment under acoustic cavity pressure disturbance

In the sound-structure coupling measurement test, a tweeter 3 with the same specifications is placed at both ends of the shell 4 as a sound source to emit sound waves of a specified frequency and amplitude to generate continuous sound in the cavity of the shell 4 The pressure vibrates, and the sound pressure signal is measured by the sound pressure sensor. The acoustic shell 2 of the tweeter 3 is fixed on the three-coordinate sliding table 1, and the three-coordinate sliding table 1 is set on the test bench 10, and can drive the tweeter 3 to move back and forth to adapt to the shells 4 of different sizes.

Under the action of the internal standing wave sound field, the casing 4 will vibrate, the acceleration sensor will record the vibration information of the casing 4, the acceleration signal and the sound pressure signal are used as the output signal of the system, and the signal is transmitted to the computer through the data acquisition system. Record test data.

(4) Acoustic cavity sound pressure response experiment under the action of structural vibration

First, remove the sound sources at both ends of the acoustic cavity shell 4, and use discs that are consistent with the shell material to close the openings at both ends. Then, a signal generator is used to generate a white noise signal, which is amplified by a power amplifier and acts on the outer wall of one end of the casing 4 as an input signal of the system. The structural vibration of the casing 4 is measured by the acceleration sensor, and then the sound source signal, acceleration signal and sound pressure signal are analyzed and collected by the data acquisition system. Finally, the analysis and processing of the recording and response are carried out by the software in the computer.

(5) Process the collected data, make the pressure oscillation frequency and structural vibration frequency graph under the two tests, carry out numerical analysis and research, and draw conclusions.

In order to use the cylindrical cavity in the test to simulate the actual situation of the actual solid rocket motor, the test designed by the present invention will use different thickness of rubber to simulate the propellant 8 with different meat thickness (ie different working time). It is also possible to carry out two sets of acoustic-structure coupling tests of acoustic cavities of different lengths (2m and 3m), each set of acoustic cavities of different lengths simulates 4 tests of propellant 4 with different rubber thicknesses, so it is expected that 8 sets of tests will be carried out, each set of tests Both are measured using two different fixing methods. Therefore, 8 sets of test equipment with different lengths and thicknesses were processed.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. A measurement method for simulating acoustic-solid coupling response characteristics of a solid rocket engine is characterized by comprising the following steps:

simplifying a solid rocket engine combustion chamber into a cylindrical pipe cavity with two open ends as a shell (4); according to the pouring form of the propellant in the combustion chamber of the solid rocket engine, rubber with the same structure and the same thickness is arranged on the inner surface of the shell (4) and is used for simulating the propellant (8);

the shell (4) is arranged on a test bench (10), and two ends of the shell (4) are respectively provided with a sound source;

a plurality of sound pressure sensors are arranged in the shell (4) along the axial direction, and a plurality of acceleration sensors are respectively arranged on the inner side and the outer side of the shell (4);

turning on the sound source, the acceleration sensor records the vibration information of the shell (4) and the sound pressure signal recorded by the sound pressure sensor as the output signal of the test;

the openings at the two ends of the shell (4) are closed, a signal generator is used for generating a white noise signal, and the white noise signal acts on the outer wall of one end of the shell (4) and serves as an input signal; vibration information of the shell (4) recorded by the acceleration sensor and a sound pressure signal recorded by the sound pressure sensor are used as output signals of the test;

and processing the data collected in the two tests to respectively obtain a transfer function from the structural oscillation to the internal pressure of the combustion chamber and a transfer function from the pressure oscillation in the combustion chamber to the structural oscillation of the engine, so as to analyze the sound-solid coupling response characteristic of the solid rocket engine.

2. A method of measurement for simulating the acoustic-solid coupling response characteristics of a solid-rocket engine as claimed in claim 1, wherein two body-fixed assemblies (5) are used to mount the housing (4) on the test-bed (10);

the main body fixing component (5) comprises a supporting frame (51), two groups of spring components and two second springs (57);

the supporting frame (51) is of a hollow structure, and the shell (4) can penetrate through the middle of the supporting frame (51); 4 uniformly distributed hoisting points are arranged on the same circumference of the outer wall of the shell (4);

the spring assembly comprises an adjusting screw rod (52), a nut (53), a tension sensor (54) and a first spring (55); the upper end of the adjusting screw rod (52) penetrates through a through hole of the supporting frame (51) and is screwed by a nut (53), the lower end of the adjusting screw rod is connected with one end of a tension sensor (54), the other end of the tension sensor (54) is connected with one end of a first spring (55), and the other end of the first spring (55) is connected to a hanging point of the shell (4); two first springs (55) of the two spring assemblies are respectively connected to lifting points on the upper part of the shell (4);

one ends of the two second springs (57) are connected to the inner wall of the support frame (51), and the other ends of the two second springs are connected to two lifting points at the lower part of the shell (4);

the first spring (55) in the two spring assemblies and the tension of the second spring (57) opposite to the first spring are on the same straight line, and the two straight lines are perpendicular to each other.

3. A method of measuring the acoustic-solid coupling response characteristic of a simulated solid rocket engine according to claim 2, wherein two mounting brackets (56) are fixed to the inner wall of the supporting frame (51), and the second spring (57) is connected to the supporting frame (51) through the mounting brackets (56).

4. A method of measurement for simulating the acoustic-solid coupling response characteristics of a solid-rocket engine as claimed in claim 2 or 3, wherein the body-fixed components (5) are fixed on the test-bed (10) symmetrically with respect to the center of the casing (4).

5. A method of measurement of acoustic-solid coupling response characteristics of a simulated solid-rocket engine according to claim 2 or 3, wherein the body-fixed assembly (5) is fixed and supported by a tripod (6).

6. A method of measurement of simulating the acoustic-solid coupling response characteristics of a solid-rocket engine as claimed in claim 2 or 3, wherein said housing (4) is made of structural steel.

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