Damping enhancing device for inhibiting unstable combustion of high-frequency tangential sound

Abstract

The invention relates to the technical field of solid rocket engines without aluminum propellants, in particular to a damping enhancing device for inhibiting unstable combustion of high-frequency tangential sound, which comprises a shell and a cover, the shell is arranged in a combustion chamber shell of a rocket engine, one side of the shell is open, and the other side of the shell is closed; one side, deviating from the opening, of the shell is communicated with a connecting hole of a front sealing head of a combustion chamber of the rocket engine; the cover body is connected to the opening of the shell, a sound absorption cavity is formed by the cover body and the shell, and a plurality of through holes communicating with the sound absorption cavity are formed in the cover body. Sound energy generated in the working process of the engine is absorbed, and the interaction between the propellant combustion process and the sound cavity mode of the combustion chamber is destroyed, so that the effect of inhibiting the unstable combustion phenomenon of the engine is achieved, and it is guaranteed that the engine normally works according to the design state.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum-free propellant solid rocket engines, and in particular to a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion. Background Art

[0002] Combustion instability is a key issue that has long affected the development process of solid rocket engines. Its basic characteristic is that the combustion chamber pressure changes periodically or approximately periodically. According to the relationship between the pressure oscillation frequency and the natural frequency of the combustion chamber cavity, combustion instability can be divided into acoustic combustion instability and non-acoustic combustion instability. Acoustic combustion instability is the result of the interaction between the propellant combustion process and the acoustic mode of the combustion chamber. Its basic characteristic is that the pressure oscillation frequency is basically consistent with the natural frequency of the combustion chamber cavity.

[0003] Due to the high energy density of solid propellants, even if only a small portion of the energy is converted into sound energy during the combustion process, large-amplitude pressure oscillations can be maintained, which further causes violent vibrations in the projectile body, rendering certain instruments and components unable to work properly, and even causing the engine to disintegrate and explode under extreme conditions.

[0004] Therefore, it is necessary to provide a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion to solve the above problems. Summary of the invention

[0005] The present invention provides a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion. By installing the device in the engine combustion chamber, the damping can be enhanced during the operation of the engine, the thermal-acoustic coupling phenomenon in the combustion chamber can be destroyed, and the effect of suppressing combustion instability can be achieved, so as to solve the problem that due to the high energy density characteristics of solid propellants, even if only a small part of the energy is converted into acoustic energy during the combustion process, large-amplitude pressure oscillations can be maintained, which further causes violent vibrations in the projectile body, causing some instruments and components to fail to work normally, and even causing the engine to disintegrate and explode under extreme conditions.

[0006] A damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion of the present invention adopts the following technical solution, including: A shell having an opening on one side, and a side facing away from the opening being used to communicate with a connecting hole of a front cover of a combustion chamber of a rocket engine; and a cover body, which is connected to the opening of the shell and forms a sound absorbing cavity with the shell, and is provided with a plurality of through holes communicating with the sound absorbing cavity.

[0007] Preferably, the shell is a bowl-shaped structure, the large end of which is open and concentrically connected to the cover body, an ignition wire placement tube is concentrically connected between the inner bottom of the bowl-shaped structure and the cover body, one end of the ignition wire placement tube passes through the cover body and the end is flush with the cover body, the other end of the ignition wire placement tube enters and passes through the bottom of the bowl-shaped structure and is connected to a connecting tube, which is used to communicate with the connecting hole of the front head of the combustion chamber of the rocket engine.

[0008] A design method of a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion of the present invention adopts the following technical solution, including: The through hole length, through hole area, through hole number, and sound absorption cavity volume are used as design parameters of the damping enhancement device; Establish the relationship between design parameters and resonant frequency; According to the relationship between the design parameters and the resonance frequency, an objective function with the sound absorption coefficient as the target is established; A multi-objective optimization algorithm is used to obtain the design parameters corresponding to the maximum objective function within the resonant frequency range required by the design; Based on the design parameters corresponding to the maximum objective function, a damping enhancement device is designed.

[0009] Preferably, the relationship between the design parameters and the resonant frequency is:

[0010] In the formula, is the resonant frequency; is the speed of sound; is the total number of through holes; is the area of ​​a single through hole; is the volume of the sound absorbing cavity; is the length of the through hole.

[0011] Preferably, the objective function is expressed as:

[0012]

[0013]

[0014]

[0015]

[0016] In the formula, is the sound absorption coefficient; is the first intermediate variable; is the second intermediate variable; is the speed of sound; is the through hole diameter; is the plate thickness; is the cavity depth; is the penetration rate of the through hole; is the perforation constant of the through hole; is the kinematic viscosity coefficient; is the angular frequency of the resonant frequency; is the resonance frequency.

[0017] Preferably, the resonant frequency range required by the design is: 7800 Hz-9000 Hz.

[0018] A solid rocket engine of the present invention adopts the following technical scheme, including: a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion disclosed in the present invention, and a solid rocket engine using a solid rocket engine without aluminum propellant.

[0019] An aircraft of the present invention adopts the following technical solution, including: a solid rocket engine disclosed in the present invention.

[0020] The beneficial effects of the present invention are: By designing a shell and a cover to form a sound-absorbing structure, a sound-absorbing effect can be achieved for solid rocket engines that experience high-frequency tangential acoustic unstable combustion, thereby destroying thermal-acoustic coupling and achieving the effect of suppressing unstable combustion. That is, the present invention absorbs the acoustic energy generated during the operation of the engine, destroys the interaction between the propellant combustion process and the acoustic cavity mode of the combustion chamber, thereby achieving the effect of suppressing the unstable combustion phenomenon of the engine and ensuring that the engine operates normally as designed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A cross-sectional view of a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to the present invention; Figure 2 It is a three-dimensional structural schematic diagram of a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to the present invention; Figure 3 It is a schematic diagram of the three-dimensional structure of a cover body in a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to the present invention; Figure 4 It is a schematic diagram of a cover body in a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to the present invention; Figure 5 Schematic diagram of theoretical sound absorption coefficient curve in an embodiment of the present invention; Figure 6 A schematic diagram of a simulation structure in an embodiment of the present invention; Figure 7 A schematic diagram of a sound absorption coefficient curve obtained by simulation in an embodiment of the present invention; Figure 8 It is a schematic diagram of a pressure curve with a damping enhancement device installed in an embodiment of the present invention; Fig. 9 It is a schematic diagram of a thrust curve with a damping enhancement device installed in an embodiment of the present invention; Fig.10 It is a schematic diagram of a pressure curve in an embodiment of the present invention without a damping enhancement device installed; Fig.11 It is a schematic diagram of a thrust curve in an embodiment of the present invention without a damping enhancement device installed; Fig.12 It is a schematic diagram of an acoustic signal curve in which a damping enhancement device is installed in an embodiment of the present invention; Fig.13 Schematic diagram of the acoustic signal curve in the embodiment of the present invention without the damping enhancement device installed.

[0023] In the figure: 1, shell; 2, cover; 21, through hole; 3, connecting tube. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] An embodiment of a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to the present invention is as follows: Figure 1 and Figure 2 As shown, it includes: a shell 1 and a cover 2, the shell 1 is arranged in the combustion chamber shell of the rocket engine, one side of the shell 1 is open, and the side of the shell 1 away from the opening is used to communicate with the connection hole of the front head of the combustion chamber of the rocket engine; the cover 2 is connected to the opening of the shell 1 and the cover 2 and the shell 1 form a sound absorbing cavity, as shown in FIG. Figure 3 and Figure 4 The cover body 2 is provided with a plurality of through holes 21 communicating with the sound absorbing cavity.

[0026] Specifically, in this embodiment, Figure 1 and Figure 2As shown, the shell 1 is a bowl-shaped structure, with its large end open and concentrically connected to the cover body 2, an ignition wire placement tube is concentrically connected between the inner bottom of the bowl-shaped structure and the cover body 2, one end of the ignition wire placement tube passes through the cover body and the end is flush with the cover body, the other end of the ignition wire placement tube enters and passes through the bottom of the bowl-shaped structure and is connected to a connecting tube 3, and the connecting tube 3 is threadedly connected to the connecting hole of the front head of the combustion chamber of the rocket engine through a thread.

[0027] A design method of a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion of the present invention comprises: Step 1, taking the length of the through hole 21, the area of ​​the through hole 21, the number of the through holes 21, and the volume of the sound absorbing cavity as design parameters of the damping enhancement device; Step 2: Establish the relationship between the design parameters and the resonant frequency; that is, the expression is:

[0028] In the formula, is the resonant frequency; is the speed of sound; is the total number of through holes 21; is the area of ​​a single through hole 21; is the volume of the sound absorbing cavity; is the length of the through hole 21.

[0029] Step 3: According to the relationship between the design parameters and the resonance frequency, establish an objective function with the sound absorption coefficient as the target, that is, the objective function is:

[0030]

[0031]

[0032]

[0033]

[0034] In the formula, is the sound absorption coefficient; is the first intermediate variable; is the second intermediate variable; is the speed of sound; is the diameter of the through hole 21; is the plate thickness; is the cavity depth; is the perforation rate of the through hole 21; is the perforation constant of the through hole 21; is the kinematic viscosity coefficient; is the angular frequency of the resonant frequency; is the resonance frequency.

[0035] Step 4: Use a multi-objective optimization algorithm to obtain the design parameters corresponding to the maximum objective function within the resonant frequency range required by the design; the resonant frequency range required by the design is: 7800Hz-9000Hz. It should be noted that the multi-objective optimization algorithm adopts a genetic algorithm, which is a prior art and will not be described in detail in this embodiment.

[0036] Step 5: Design a damping enhancement device based on the design parameters corresponding to the maximum objective function.

[0037] A solid rocket engine of the present invention comprises: a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion of the present invention, wherein a connecting tube of the damping enhancement device is connected to the head of the combustion chamber of the rocket engine, a connecting tube 3 of a shell 1 of the damping enhancement device is connected and fixed to a connecting hole of a front cover of the combustion chamber, and a fixing method can be flexibly determined according to the fixing methods that can be adopted by different solid rocket engines, and an opening surface of the device should be placed normal to the incident direction of the sound wave. After the device is installed, the engine can start working normally to play a sound absorbing role, thereby achieving the effect of suppressing unstable combustion.

[0038] An aircraft of the present invention comprises the solid rocket engine of an embodiment of the present invention.

[0039] The present invention is described below in conjunction with specific embodiments: Step 1: Damping enhancement verification: Taking the actual combustion instability problem of a certain type of engine as the background, the structural design and sound absorption effect verification of the damping enhancement device were carried out. The tangential sound oscillation frequency in the combustion chamber of this type of engine is concentrated in 7800Hz-9000Hz. Therefore, the design requirement for the damping enhancement device is to achieve the maximum sound absorption coefficient as much as possible within the frequency range of 7800Hz-9000Hz to suppress acoustic oscillation and destroy thermal-acoustic coupling.

[0040] Based on the objective function, it can be seen that since the sound absorption effect of the damping enhancement device is affected by multiple parameters, it is necessary to search for the optimal parameter combination according to the expression of the objective function during the design process so that the average sound absorption coefficient of the damping enhancement device in the frequency range of 7800Hz-9000Hz is the highest, thereby achieving the best sound absorption effect.

[0041] The final design parameters are as follows: the volume of the sound absorption cavity is 30cm3, the length of the through hole 21 (i.e., the plate thickness and wall thickness) is 2mm, the diameter of the through hole 21 is 0.6mm, the total number of through holes 21 is 624, and the hole opening method is to evenly open the holes on the opening surface to prevent burn-through during the operation of the engine. Due to the space shape limitation in the front head, the sound absorber is designed as a bowl-shaped structure, the diameter of the opening surface (i.e., the cover plate 2) is 84mm, and because of the ignition requirement, a 5mm diameter opening is left on the opening surface for the placement of the ignition line. It should be noted that the 5mm opening cannot affect the sound absorption cavity of the damping enhancement device. Therefore, it is necessary to design the wall surface for closure, so this embodiment is set in the form of a connecting tube. Finally, the connecting tube 3 at the rear end of the damping enhancement device has an M10×1-6H thread to connect with the front head of the combustion chamber.

[0042] After completing the parameter design of the damping enhancement device, verify its damping enhancement effect. According to the designed design parameters, the theoretical sound absorption coefficient curve can be obtained as follows: Figure 5 As shown, according to Figure 5 It can be concluded from the theoretical sound absorption coefficient curve shown that the damping enhancement device of the present invention can achieve the highest sound absorption coefficient within a specified frequency range, and can meet the requirements for effectively absorbing sound energy during the operation of the engine.

[0043] However, the above theoretical calculations do not introduce a specific physical field, and additional verification is needed to make the conclusion credible. Therefore, this embodiment also verifies the resonant frequency and sound absorption coefficient of the device based on COMSOL design simulation. The simulation setting diagram is shown in Figure 6 As shown in the figure, the sound absorption coefficient curve obtained by simulation is as follows Figure 7 As shown, according to Figure 7 The simulation results and Figure 5 From the theoretical verification results shown, it can be known that the damping enhancement device designed in this embodiment has a higher sound absorption coefficient within the selected frequency range, has a significant effect on absorbing sound energy during the operation of the engine, can effectively destroy thermal-acoustic coupling, and achieves damping enhancement during the operation process.

[0044] Step 2: Validity verification: After the design and processing of the damping enhancement device is completed, the present embodiment also conducts an engine test to verify the effectiveness of installing the damping enhancement device. Two engine tests were designed in total. Under the condition that the other test conditions are completely the same, a ground test bench ignition test was conducted, and the pressure, thrust data and acoustic signals during the test were recorded. The data of the two tests were analyzed and compared to verify whether the installation of the damping enhancement device can effectively suppress the combustion instability phenomenon.

[0045] In the first engine experiment, a damping enhancement device was installed in the engine, and the pressure curve during the engine operation was obtained as shown below: Figure 8 As shown, the thrust curve during the engine operation is obtained as Fig. 9 As shown by Figure 8 and Fig. 9 It can be seen that the pressure curve and thrust curve during the engine operation are normal, both in line with the engine design state, no abnormal working state occurs, and the unstable combustion phenomenon disappears. In the second engine test, the engine was ignited without adding a damping enhancement device and kept in the original design state as a control effect. The pressure curve obtained in the second engine test is shown in the figure below. Fig.10 The thrust curve is shown in Fig.11 As shown. Fig.10 and Fig.11 It can be seen that the engine has obvious pressure rise phenomenon during operation, and the thrust also has large oscillation phenomenon. Therefore, this embodiment believes that unstable combustion occurred in the engine test without the damping enhancement device installed. By comparing the results of the two engine tests, it can be seen that whether the damping enhancement device is installed has a great influence on the test results, and the curves obtained from the test are very different. Among them, the test curve with the damping enhancement device installed is very normal, while the test curve without the damping enhancement device installed shows obvious abnormalities, which can indicate that the installation of the damping enhancement device has played a positive role in suppressing unstable combustion and achieved the design purpose.

[0046] Secondly, during the test, the acoustic signals during the engine operation were recorded twice to verify the effect of the damping enhancement device on suppressing combustion instability from the acoustic aspect. The acoustic signal curve obtained by the first engine experiment is as follows: Fig.12 As shown in the figure, the acoustic signal curve obtained from the second engine test is as follows: Fig.13 As shown in the figure, by measuring the acoustic signals in the two engine tests, it can be found that the acoustic signal curve measured by the engine test with the damping enhancement device installed in the first engine test conforms to the characteristics of the normal operation of the engine, that is, the sound energy intensity decreases evenly with the increase of frequency. However, the acoustic signal measured by the engine without the damping enhancement device has an obvious characteristic frequency peak at the frequency of unstable combustion. Comparing the two tests, it can be shown that the damping enhancement device has a significant sound absorption effect within the designed frequency range.

[0047] In summary, by conducting engine tests on engines with and without sound absorbers installed, recording the thrust, pressure and acoustic signal data of the engine during operation, and analyzing the above data in combination with the engine tests, the following conclusions were drawn: the damping enhancement device can effectively absorb sound energy within the selected frequency range, thereby suppressing unstable combustion.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion, characterized in that: include: A shell is arranged in the combustion chamber shell of the rocket engine, one side of which is open, and the side facing away from the opening is used to communicate with the connecting hole of the front head of the combustion chamber of the rocket engine; and a cover body, which is connected to the opening of the shell and forms a sound absorbing cavity with the shell, and is provided with a plurality of through holes communicating with the sound absorbing cavity.

2. A damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to claim 1, characterized in that: The shell is a bowl-shaped structure, and the opening at its large end is concentrically connected to the cover body. An ignition wire placement tube is concentrically connected between the inner bottom of the bowl-shaped structure and the cover body. One end of the ignition wire placement tube passes through the cover body and the end is flush with the cover body. The other end of the ignition wire placement tube enters and passes through the bottom of the bowl-shaped structure and is connected to a connecting tube. The connecting tube is used to be threadedly connected to the connecting hole of the front head of the combustion chamber of the engine.

3. A design method for a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion, characterized in that: include: The through hole length, through hole area, through hole number, and sound absorption cavity volume are used as design parameters of the damping enhancement device; Establish the relationship between design parameters and resonant frequency; According to the relationship between the design parameters and the resonance frequency, an objective function with the sound absorption coefficient as the target is established; A multi-objective optimization algorithm is used to obtain the design parameters corresponding to the maximum objective function within the resonant frequency range required by the design; Based on the design parameters corresponding to the maximum objective function, a damping enhancement device is designed.

4. The design method of a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to claim 3, characterized in that: The relationship between design parameters and resonant frequency is: In the formula, is the resonant frequency; is the speed of sound; is the total number of through holes; is the area of ​​a single through hole; is the volume of the sound absorbing cavity; is the length of the through hole.

5. The design method of a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to claim 3, characterized in that: The expression of the objective function is: In the formula, is the sound absorption coefficient; is the first intermediate variable; is the second intermediate variable; is the speed of sound; is the through hole diameter; is the plate thickness; is the cavity depth; is the penetration rate of the through hole; is the perforation constant of the through hole; is the kinematic viscosity coefficient; is the angular frequency of the resonant frequency; is the resonant frequency.

6. The design method of a damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion according to claim 3, characterized in that: The resonant frequency range required by the design is: 7800Hz-9000Hz.

7. A solid rocket engine, characterized in that: include: A damping enhancement device for suppressing high-frequency tangential acoustic unstable combustion as described in any one of claims 1-2.

8. The solid rocket motor according to claim 7, characterized in that: The solid rocket motor uses a solid rocket motor with aluminum-free propellant.

9. An aircraft, characterized in that: Including the solid rocket motor as described in claim 7 or 8.

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