CN111751110B - Carbon fiber heat release sound production device for oscillation combustion of solid propellant - Google Patents
Carbon fiber heat release sound production device for oscillation combustion of solid propellant Download PDFInfo
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- CN111751110B CN111751110B CN202010634020.XA CN202010634020A CN111751110B CN 111751110 B CN111751110 B CN 111751110B CN 202010634020 A CN202010634020 A CN 202010634020A CN 111751110 B CN111751110 B CN 111751110B
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Abstract
The invention discloses a carbon fiber heat release sound production device for oscillation combustion of a solid propellant, which comprises: the tester is a horizontally placed pipe body, and the inner cavity of the tester is used as a cavity for simulating pressure oscillation in a rocket engine combustion chamber. The heat release device is used for being vertically placed in the tester and comprises: the two heat insulation supporting pieces are plate bodies which are arranged at intervals and are parallel. Two electrodes, both of which are columnar bodies, each vertically penetrating through the two heat insulation supporting members; each electrode is horizontally equidistant from one of the open ends of the tester. And the carbon fiber yarns are wound on the parts, located between the two heat insulation supporting pieces, of the two electrodes in a reciprocating mode, and the adjacent wound carbon fiber yarns are not attached to each other. And the signal source is arranged outside the tester and is connected with the two electrodes, and the signal source, the two electrodes and the wound carbon fiber wire form a loop. The device realizes the generation of continuous, stable and controllable pressure oscillation with large amplitude in the tester.
Description
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of solid rocket engine combustion, and particularly relates to a carbon fiber heat release sound production device for solid propellant oscillatory combustion.
[ background of the invention ]
Accurate acquisition of combustion response values of the propellant under the pressure oscillation condition is the basis for predicting the combustion instability of the engine. At present, it is usually obtained experimentally, in a tester, by simulating the generation of pressure oscillations of large amplitude in the combustion chamber of a rocket engine. The method has the advantages that a loudspeaker and the like are used as external excitation, periodic pressure oscillation is generated in a tester by introducing periodic current to the loudspeaker, but the amplitude of the pressure oscillation generated by the method is small, belongs to the field of small disturbance, and is difficult to obtain nonlinear combustion response; a pulse excitation method can also be adopted, a small rocket engine is used for ignition, fuel gas with certain pressure and temperature is generated, and the explosion aluminum sheet is flushed and then enters a closed tester cavity to obtain required pressure oscillation. The method can generate pressure oscillation with extremely large amplitude, but the damping speed of the pressure oscillation is high, the pressure oscillation is different from the actual combustion condition of the propellant in the engine to a certain extent, and the experimental requirements are difficult to meet.
[ summary of the invention ]
The invention aims to provide a carbon fiber heat release sound production device for oscillation combustion of a solid propellant, which realizes continuous, stable and controllable large-amplitude pressure oscillation generated in a tester.
The invention adopts the following technical scheme: a carbon fiber heat release sound production device for oscillating combustion of solid propellant comprises: the tester is a horizontally placed square pipe body, and the inner cavity of the tester is used as a cavity for simulating pressure oscillation in a rocket engine combustion chamber; and its acoustic cavity modal frequency is known.
The heat release device is used for being vertically placed in the tester and comprises: the two heat insulation supporting pieces are both sheet-shaped bodies and are arranged at intervals and are parallel. Two electrodes, both of which are columnar bodies, each vertically penetrating through the two heat insulation supporting members; each electrode is horizontally equidistant from one of the open ends of the tester. And the carbon fiber yarns are wound on the parts, located between the two heat insulation supporting pieces, of the two electrodes in a reciprocating mode, and the adjacent wound carbon fiber yarns are not attached to each other.
And the signal source is arranged outside the tester and is connected with the two electrodes, and the signal source, the two electrodes and the wound carbon fiber wire form a loop. The signal source is used for transmitting signal waves to the carbon fiber wires to enable the carbon fiber wires to release heat, and when the heat release frequency of the carbon fiber wires is consistent with the oscillation frequency of the tester, the carbon fiber wires and the tester are coupled to generate large-amplitude gas pressure oscillation in the tester. And the gas supply system is communicated with the pipeline of the inner cavity of the tester and is used for filling gas into the cavity.
Further, each electrode was horizontally spaced from one of the open ends of the tester 1/4, the total length of the tester.
Further, the two heat insulation supporting pieces are arranged at intervals from front to back or from top to bottom.
Furthermore, the two electrodes are all metal columns, and threads are arranged on the metal columns along the length direction of the metal columns and used for supporting and spacing the carbon fiber yarns.
Further, the signal source is a function generator and a power amplifier which are connected, and the power amplifier is connected with each electrode.
Furthermore, a plurality of pressure sensors are arranged on the outer wall of the tester at intervals along the length of the tester, and each pressure sensor is connected with a data acquisition system.
Further, the number of the pressure sensors is 3, and the pressure sensors are respectively positioned at two ends of the tester and at the length of 1/2 pipes.
The invention also discloses a heat release device which is placed in the tester, wherein the tester is a horizontally placed square pipe body, and the inner cavity of the tester is used as a cavity for simulating the pressure oscillation in the combustion chamber of the rocket engine; and its acoustic cavity modal frequency is known.
The heat release device comprises: the two heat insulation supporting pieces are plate bodies which are arranged at intervals and are parallel. Two electrodes, both of which are columnar bodies, each vertically penetrating through the two heat insulation supporting members; each electrode is horizontally equidistant from one of the open ends of the tester. The carbon fiber wires are wound on the parts, located between the two heat insulation supporting pieces, of the two electrodes in a reciprocating mode, and the adjacent wound carbon fiber wires are not mutually attached; the carbon fiber wire is used for being connected with a signal source, signal waves are transmitted by the signal source, the carbon fiber wire releases heat, when the heat release frequency of the carbon fiber wire is consistent with the oscillation frequency of the tester, the carbon fiber wire and the tester are coupled, and large-amplitude gas pressure oscillation is generated in the tester.
The invention also discloses a working mode of the carbon fiber heat release sound production device for the oscillation combustion of the solid propellant, which comprises the following steps:
the tester with two closed ends is filled with nitrogen and reaches a set pressure.
The function generator outputs simple harmonic electric signals with set frequency and amplitude, the simple harmonic electric signals are transmitted to the power amplifier, and then the simple harmonic electric signals are respectively transmitted to the rings of carbon fiber yarns through the electrodes; the set frequency is 1/2 of the first order acoustic modal oscillation frequency of the tester.
Each circle of carbon fiber filaments periodically release heat along with the periodic change of the simple harmonic waves; the heat release frequency of the carbon fiber yarn is equal to the first-order acoustic modal oscillation frequency corresponding to the tester, and the two are coupled to generate large-amplitude gas pressure oscillation in the tester.
The invention has the beneficial effects that: in a tubular tester with known sound cavity modal frequency, continuous, stable and controllable large-amplitude pressure oscillation is generated in the tester by selecting the heat release and sound production characteristics, namely frequency, power and waveform, of the high-sensitivity wide-frequency-response carbon fiber filament.
[ description of the drawings ]
FIG. 1 is a schematic view showing the structure of a heat release device for placement in a tester according to the present invention.
Fig. 2 is a schematic structural diagram of a carbon fiber heat release sound production device for oscillating combustion of a solid propellant in the invention.
Fig. 3 is a graph showing the change in the amplitude of pressure oscillations over time measured in a nitrogen atmosphere.
Wherein:
3a. is a graph of the variation of pressure oscillations over a period of time.
Partial enlargement of the pressure oscillations.
Graph of the FFT analysis results for pressure oscillations in 3a.
Wherein: 1. a tester; 2. a square flange; 3. a pressure sensor; 4. a heat release device; 5. a function generator; 6. a power amplifier; 7. a nitrogen gas cylinder; 8. an electromagnetic valve; 9. an exhaust valve; 10. a data acquisition system; a signal source; 4-1, carbon fiber filaments; 4-2. thermally insulating support; 4-3. electrodes; 4-4. nut.
[ detailed description ] embodiments
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1 and 2, the invention discloses a carbon fiber heat release sound production device for oscillation combustion of solid propellant, comprising: the tester 1 is a horizontally placed pipe body, the cross section of the tester is rectangular or square, and the inner cavity of the tester is used as a cavity for simulating pressure oscillation in a rocket engine combustion chamber; and its acoustic cavity modal frequency is known.
The heat release device 4 is used for being vertically placed in the tester 1 and comprises: the two insulating supports 4-2, both plates, are shaped in accordance with the cross-section of the test cell 1. And are parallel. The two electrodes 4-3 are both columnar bodies, and each electrode 4-3 vertically penetrates through the two heat insulation supporting pieces 4-2; each electrode 4-3 is horizontally equidistant from one of the open ends of the tester 1. The carbon fiber filaments 4-1 are wound on the parts of the two electrodes 4-3 between the two heat insulation supports 4-2 in a reciprocating mode, and the adjacent wound carbon fiber filaments 4-1 are not attached to each other. The height of each of the two insulating supports 4-2 is slightly less than the height of the inner cavity of the tester 1. The spacing is such that the width and thickness of the two insulating supports 4-2 are such that they can be stably and vertically positioned. The heat insulation support 4-2 is made of heat insulation material.
And the signal source 11 is arranged outside the tester 1 and is connected with the two electrodes 4-3, and the signal source 11, the two electrodes 4-3 and the wound carbon fiber wire 4-1 form a loop. The signal source 11 is used for transmitting signal waves to the carbon fiber filament 4-1 to enable the carbon fiber filament 4-1 to release heat, and when the heat release frequency of the carbon fiber filament 4-1 is consistent with the oscillation frequency of the tester 1, the carbon fiber filament 4-1 and the tester are coupled to generate large-amplitude gas pressure oscillation in the tester 1.
And the gas supply system is communicated with the pipeline of the inner cavity of the tester 1 and is used for filling gas into the cavity.
The two electrodes 4-3 are each located at a horizontal distance 1/4 from one of the open ends of the tester 1, the length of the tester 1. The two heat insulating supports 4-2 are arranged at intervals in the front-back direction or in the up-down direction. The carbon fiber filaments 4-1 are completely positioned on the same cross section in the tester 1 no matter the carbon fiber filaments are arranged at intervals from front to back or arranged at intervals from top to bottom. The two electrodes 4-3 are all metal columns, and threads are arranged on the metal columns along the length direction of the metal columns and used for supporting and spacing the carbon fiber filaments 4-1.
The signal source 11 is a function generator 5 and a power amplifier 6 connected to each other, and the power amplifier 6 is connected to each of the electrodes 4-3.
A plurality of pressure sensors 3 are arranged on the outer wall of the tester 1 at intervals along the length of the tester, and each pressure sensor 3 is connected with a data acquisition system 12. The pressure sensors 3 are preferably 3 and are respectively positioned at two ends of the tester 1 and at the length of 1/2 pipes.
The invention also discloses a heat release device which is placed in the tester 1, the tester 1 is a horizontally placed square pipe body, the cross section of the tester is rectangular or in the positive direction, and the inner cavity of the tester is used as a cavity for simulating the pressure oscillation in the combustion chamber of the rocket engine; and the acoustic cavity modal frequencies of tester 1 are known.
The heat release device comprises: the two heat insulation supporting pieces 4-2 are plate bodies which are arranged at intervals and are parallel. The two electrodes 4-3 are both columnar bodies, and each electrode 4-3 vertically penetrates through the two heat insulation supporting pieces 4-2; each electrode 4-3 is horizontally equidistant from one of the open ends of the tester 1. The carbon fiber wires 4-1 are wound on the parts, located between the two heat insulation supporting pieces 4-2, of the two electrodes 4-3 in a reciprocating mode, and the adjacent wound carbon fiber wires 4-1 are not attached to each other; the carbon fiber filament 4-1 is used for being connected with a signal source 11, the signal source 11 transmits signal waves to enable the carbon fiber filament 4-1 to release heat, and when the heat release frequency of the carbon fiber filament 4-1 is consistent with the oscillation frequency of the tester 1, the carbon fiber filament 4-1 and the tester are coupled to generate large-amplitude gas pressure oscillation in the tester 1.
The working mode of the carbon fiber heat release sound production device for the oscillation combustion of the solid propellant is as follows: the tester 1 with two closed ends is filled with nitrogen and reaches a set pressure. The function generator 5 outputs simple harmonic electric signals with set frequency and amplitude, the simple harmonic electric signals are transmitted to the power amplifier 6 and then are respectively transmitted to the carbon fiber filaments 4-1 of each circle through the electrodes (4-3); the frequency was set to 1/2 of the first order mode oscillation frequency of the tester 1.
Each circle of carbon fiber wires 4-1 periodically release heat along with the periodic change of the simple harmonic wave, the heat release frequency of the carbon fiber wires 4-1 is equal to the first-order acoustic mode oscillation frequency corresponding to the tester (1), and the two are coupled to generate large-amplitude gas pressure oscillation in the tester 1.
The conversion process from thermal energy to acoustic energy is a forward process according to the rayleigh criterion and pressure oscillations occur when unstable heat release rates and pressure fluctuations are in phase. The rayleigh criterion needs to satisfy the following inequality:
where T, V, Φ represent the oscillation period, the control volume, i.e., the combustion chamber volume, and the total dissipation of acoustic energy, including the sum of viscous losses, particle damping, radiation dissipation, etc., respectively. When the above inequality is satisfied, thermoacoustic instability will occur. The left side of the inequality represents the amount of heat transferred to the oscillation by the heating process during each cycle; the right side of the inequality is the total energy dissipation due to oscillation in each cycle, which is usually negligible.
For a closed-ended tubular structure, if first order acoustic mode instability is to be produced, it is necessary to place the heat release device in the portion of the tube near the orifice, the optimal location being 1/4 the length of the tube. Meanwhile, the more heat is added to the gas in the tube, the larger the amplitude of the generated oscillation is, while other parameters remain unchanged.
In the invention, the carbon fiber wire 4-1 is used as a heat release source, and the thermoacoustic effect of the carbon fiber wire 4-1 is utilized to produce sound. The sound production principle of the thermoacoustic effect is as follows: the fluctuation of the current input into the heat release source is utilized to generate surface temperature fluctuation, so that the circumferential local air density of the heat release source is changed, the surrounding air pressure fluctuation is caused, and the sound production process is realized in the sound cavity. When the carbon fiber wire 4-1 is subjected to alternating current, the carbon fiber wire is heated in both positive and negative half periods, and temperature oscillation with twice frequency and sound pressure with twice frequency are generated. If it is notCurrent of input sine signal
And assuming that the carbon fiber 4-1 is a pure resistor and the resistance value is R, the output power P isoutput(t) can be expressed as:
from the above, the frequency is from the original finω/2 pi to f out2 ω/2 pi ω/pi, the output frequency is twice the input frequency. I.e. the output frequency of the carbon fibre filaments 4-1 is twice the input frequency.
The heat generated by the carbon fiber filament is proportional to the length of the carbon fiber filament, and in order to generate more heat, the length of the carbon fiber filament per unit cross-sectional area needs to be ensured to be as long as possible. Since the heat release device is used for being placed in the cavity of the tester 1, the size of the heat release device is limited, and the cross-sectional configuration of the cavity of the tester 1 is considered so as to ensure that the heat release device can be placed and generate more heat. Therefore, the method is adopted, namely, the carbon fiber wire is wound on two axial electrodes 4-3 arranged at intervals in a reciprocating mode to form a net-shaped body consisting of a plurality of wire coils which are sequentially and integrally connected, and the wire coils are closely arranged along the length direction of the electrodes, but the adjacent wire coils are not attached to each other. In addition, the electrode 4-3 in the invention also serves as a fixing device and plays a role of fixing and supporting the carbon fiber wire 4-1.
The function generator 5 in the signal source 10 supplies the carbon fiber filament 4-1 with an input frequency and waveform, but the amplitude of its own waveform is low, so that it is necessary to connect the power amplifier 6 between the function generator 5 and the carbon fiber filament 4-1. The function generator 5 is used to generate a specified sinusoidal ac signal, which is a simple harmonic required in the present invention. The power is proportional to the resistance value under the same input voltage, and the power is P ═ U2The resistance is proportional to the length of the carbon fiber filament, so that in order to obtain a larger input power, the resistance needs to be smaller, and a larger heating area needs to be ensured. The electrodes can be increased according to the size of the actual tester 14-3, the carbon fiber wire 4-1 can be wound on the electrode 4-3 more densely under the premise of ensuring that the adjacent carbon fiber wires are not contacted with each other, so as to obtain larger input power. Through verification, in the tester, when the carbon fiber wire is wound on the adopted electrode 4-3 for 4-1 circles for more than 8 circles, the heat release effect is ideal. However, the amplification factor of the power amplifier 6 also needs to be properly adjusted to ensure that the carbon fiber filament 4-1 can work stably for a long time and work for a stable time>200s, or can be adjusted according to the actual required working condition to prevent the carbon fiber filament 4-1 from being burnt in the working process. The input of the signal source 11 is sine wave, and the signal source has a good use effect within 1000 Hz.
As the carbon fiber wire 4-1 is conductive, and the electrode 4-3 adopts a metal column, the carbon fiber wire 4-1 cannot be directly placed in the tester 1 in order to prevent short circuit and the like in the working process; in addition, since the carbon fiber 4-1 has a soft texture, if it is directly placed in the tubular tester 1, the effective heating area is low, and the heating effect is not ideal. Therefore, two heat insulation supporting pieces 4-2 are arranged, are both sheet-shaped bodies and are arranged at intervals and are parallel; the carbon fiber wires 4-1 are wound on the two electrodes 4-3 in a reciprocating manner at the position between the two heat insulation supports 4-2, and the adjacent wound carbon fiber wires 4-1 are not attached to each other. The end of the metal column is fixed by a nut 4-4, and a bolt is sleeved on the metal column attached to the inner wall of the heat insulation support 4-2 to play a role in fixing and isolating the two heat insulation supports 4-2.
The heat release device is placed at the position, away from 1/4 pipe orifices of one pipe orifice, of the tubular tester 1, the function generator 5 and the power amplifier 6 are adjusted, so that the carbon fiber wire reaches the maximum power capable of working normally, the carbon fiber wire 4-1 releases heat, the circumferential gas density is reduced, pressure oscillation is generated, obvious sound can be heard in the tester 1, and the amplitude of the pressure oscillation generated in the tester 1 can be measured through the pressure sensor 10 on the tester 1. The two ends of the tester 1 are respectively provided with a square flange 2 which is sealed by a rubber gasket, and each end of the flange is fixed by 12M 6 bolts, so that the air tightness of the device is ensured.
The tubular tester 1 is fixed on a test bed by a fixing frame, a plurality of pressure sensors 3 are arranged at equal intervals along the length direction of the tubular tester 1, preferably 3, the positions of the 3 sensors 10 are respectively the two end parts and the middle part of the tester 1, the length of the tester 1 is set to be L, the left end in the figure is used as a starting point, the set positions are 0, L/2 and L, and the sensors 3 are used for measuring the pressure in the experimental process. The input power to the heat release device 4 located in the chamber of the tester 1 is regulated by a function generator 5 and a power amplifier 6. Meanwhile, a pressure supply system is connected in the experimental device, the pressure supply system is communicated with an inner cavity pipeline of the tester 1, a nitrogen gas cylinder 7 is used for supplying gas, and an electromagnetic valve 8 and an exhaust valve 9 are arranged on a pipeline between the nitrogen gas cylinder 7 and the tester 1 and used for generating specified initial balance pressure. The carbon fiber yarn 4-1 cannot stably operate in an air atmosphere for a long time. Therefore, the heat source device needs to be placed in an inert atmosphere such as nitrogen.
Each pressure sensor 3 is connected to the data acquisition and processing system 10, and is configured to convert a signal of the pressure sensor 3 into a voltage, and then convert the voltage into a pressure value through a conversion relationship.
The experimental measurement is carried out by adopting the carbon fiber filament heat release device for oscillating combustion of the solid propellant, which comprises the following specific steps:
first, in order to confirm the feasibility of the scheme of the present invention, the measurement and analysis of the relevant thermoacoustic characteristics of the carbon fiber filament 4-1 were performed, including power for stable operation, stable operation time, frequency response, etc. under air/nitrogen environment and dc/ac conditions.
Firstly, measuring the power and the stable working time of the carbon fiber 4-1 as a heat source in the tester 1 under the atmosphere of air and nitrogen and the direct current and alternating current electrifying environment respectively, wherein the resistance value of the selected carbon fiber 4-1 per unit length is about 1.884 omega/cm, namely 188.4 omega/m. Specific working conditions and experimental results are shown in table 1. The results show that: in an air environment, the carbon fiber filament 4-1 cannot stably release heat for a long time, the working time is less than 50s, and the maximum input power is low; after nitrogen with certain pressure is introduced, the input power and the corresponding stable heat release time of the carbon fiber filament 4-1 are obviously improved, and the working time reaches 100 and 500 seconds, even more than 1000 seconds. Therefore, the obtained carbon fiber yarn 4-1 can stably work for a long time with high power in a nitrogen atmosphere.
Table 1 verification of working of carbon fiber filaments in air and nitrogen environments, respectively
In addition, the duration of the pulse excitation in the pulse excitation method is generally less than 1s, and the duration of the pressure oscillation generated by the pulse excitation is less than 1 s. As can be seen from the data in Table 1, the stable heat release time of the carbon fiber filament 4-1 in the nitrogen atmosphere can reach 100-500s, even more than 1000 s.
And secondly, measuring the frequency response characteristic of the carbon fiber filament 4-1, and aiming at the simple harmonic waves of different input frequencies, extracting the gray value of the light and shade change of the light emitted by the carbon fiber filament 4-1, and then performing Fast Fourier Transform (FFT) on the gray value to obtain the working frequency of the carbon fiber filament 4-1, thereby determining the relation between the output frequency and the input frequency. At present, the pressure oscillation frequency generated by the solid engine is mostly concentrated in the medium frequency range, namely 100-1000Hz, so that the frequency response range for researching the combustion response characteristic of the solid propellant is also 100-1000Hz medium frequency oscillation. Analyzing the relationship between the input frequency of the signal source and the heat release output frequency of the carbon fiber filament by two times according to the theory, thereby sweeping the frequency fin: set at 0-600Hz and frequency f of 4-1 for carbon fiber yarnoutThe response characteristic was measured. The results show that: when the input frequency of the signal source is 50Hz, the output frequency of the carbon fiber wire 4-1 is 101Hz, and when the input frequency of the signal source is 600Hz, the output frequency of the carbon fiber wire can reach 1203 Hz. The experimental results satisfied the frequency range of interest of the study, 100- & 1000 Hz. At the same time, the relation between the input frequency and the output frequency of the frequency signal source is basically kept twice, namely 2fin＝foutConsistent with theoretical results. Therefore, when the frequency to be measured is f, it is necessary to set the input frequency to f/2. The frequency response of carbon fiber filament 4-1 can meet the requirements in the frequency range of interest in current research. Obtained from the above experimental resultsIn conclusion, for measuring the combustion response characteristic of the solid propellant in the range of 100-1000Hz, the carbon fiber wire 4-1 is adopted as the heat release sound production device to meet the frequency response requirement.
Subsequently, the pressure oscillation amplitude that the carbon fiber yarn 4-1 can produce was measured under a nitrogen atmosphere using the aforementioned tubular tester 1.
The heat release device is placed in a cavity of the tester 1, the wound carbon fiber wires 4-1 are located at a position which is far away from the inlet 1/4 pipe at the right end, and end covers at two ends are installed on the square flange 2, so that the air tightness of the tester 1 is ensured. Then, nitrogen gas was introduced. The right hand side herein is defined with respect to the provided figures. The left and right sides of the invention are based on the attached drawings.
Before the experiment, nitrogen is firstly introduced into the tester 1, and the method specifically comprises the following steps: the vent valve 9 on the line was opened to vent the air in the tubular tester 1. Then closing the exhaust valve 9 and introducing nitrogen into the tubular tester 1; when the pressure in the tester is 0.6MPa, stopping introducing the nitrogen; simple harmonics of a specified frequency and power are input to the carbon fiber filament 4-1 by a signal source 11. The pressure change condition in the whole process is recorded by using the pressure sensor 3, the numbers of the pressure sensor 3 from the left end to the right end are respectively a, b and c, and the positions are respectively 0L and 1/2L, L from the left end of the tester 1. And in the working process of the carbon fiber yarn 4-1, the input power is 500W. The resonance frequencies of the tester 1 were 246Hz and 413Hz, respectively, and thus in order to determine the exothermic heat of the carbon fiber filament 4-1 and the resonance frequency of the tester 1, and set the input frequency of the function generator 5 to 0-500Hz according to the double relationship of the input frequency and the output frequency, the two were coupled when the resonance frequency of the acoustic cavity and the exothermic frequency were equal, thereby experimentally verifying the double relationship between the coupling frequency and the input frequency.
And (3) recording the change of the pressure oscillation amplitude of the pressure sensor after the carbon fiber wire 4-1 is electrified within a period of time through experiments, as shown in fig. 3.
As can be seen from fig. 3a, since the frequency of the signal source 11 is gradually increased from 0Hz to 500Hz with time, the signal source is coupled with the first-order frequency and the second-order frequency of the acoustic cavity at 18.2s and 22.4s respectively to be in a resonance state, the amplitude of the pressure oscillation after the coupling resonance is maximum and is 0.2 and 0.25 respectively, and the released heat frequency is not coupled with the acoustic cavity frequency and is in an off-resonance state at 14s, 16s, 20s, 24s and the like. The amplitude of the non-resonance was about 0.03 and the ratio of the maximum amplitude of the resonance to the amplitude of the non-resonance was about 8 times, indicating that a relatively significant pressure oscillation occurred in the tester 1 after the carbon fiber filament 4-1 was energized. In the prior art, a loudspeaker is adopted as external excitation, the amplitude of pressure oscillation generated is about 0.04, and the amplitude of pressure generated by heat release of the carbon fiber yarn 4-1 in the invention is about 6 times of the amplitude generated by the loudspeaker.
The maximum amplitudes, i.e. at 17.5-19s and 21-23 s, are chosen to be amplified, resulting in the result shown in fig. 3b, which gives a process where the pressure oscillation amplitude undergoes a linear increase and decay. This is because as the input frequency gradually increases, the heat release frequency also increases accordingly, and as the input frequency approaches the resonance frequency of the tester 1, the resonance amplitude gradually increases. When the input frequency continues to increase and the generated heat release frequency exceeds the resonance frequency of the tester 1, the resonance effect is eliminated and the oscillation amplitude is reduced to an un-resonance state.
The FFT analysis of the oscillation segments 17.5-23s in fig. 3a, results are shown in fig. 3c, and it can be seen that there are two distinct peak frequencies of oscillation, 246.6Hz and 413.4Hz respectively, corresponding to the first and second order oscillation frequencies of the tester. And the first and second order frequencies of the oscillation of the tube tester 1 at the normal temperature 298K calculated by the formula f ═ na)/(2L were 170Hz and 340Hz, respectively. The reasons for the above differences are: the sound velocity of the sound field is changed due to the fact that the temperature of the carbon fiber filament 4-1 is high in the working process. The temperature in the tester 1 was corrected to obtain first and second order frequencies of oscillation of the tubular tester 1 of 246Hz and 410Hz, respectively. Consistent with the experimental results.
The experiments show that pressure oscillation with certain amplitude can be generated in the tester 1 by using the carbon fiber wire 4-1 as a heat source, which shows that a scheme for researching the oscillatory combustion of the solid propellant in the frequency range of 100-1000Hz by using the heat release sound of the carbon fiber wire 4-1 is feasible.
Claims (10)
1. A carbon fiber heat release sound production device for oscillating combustion of solid propellant is characterized by comprising:
the tester (1) is a horizontally placed pipe body, and the inner cavity of the tester is used as a cavity for simulating pressure oscillation in a rocket engine combustion chamber; and the modal frequency of the acoustic cavity is known;
a heat release device (4) for vertical placement in a tester (1), comprising:
two heat insulation supporting pieces (4-2) which are both plate-shaped, arranged at intervals and parallel; the shape of the test tube is consistent with that of the cross section of the tester (1);
two electrodes (4-3) which are both cylindrical bodies, wherein each electrode (4-3) vertically penetrates through the two heat insulation supporting members (4-2); the horizontal distances between each electrode (4-3) and one open end of the tester (1) are equal;
the carbon fiber wires (4-1) are wound on the parts, located between the two heat insulation supporting pieces (4-2), of the two electrodes (4-3) in a reciprocating mode, and the carbon fiber wires (4-1) wound adjacently are not attached to each other;
the signal source (11) is arranged outside the tester (1) and is connected with the two electrodes (4-3), and the signal source (11), the two electrodes (4-3) and the wound carbon fiber yarn (4-1) form a loop;
the signal source (11) is used for transmitting signal waves to the carbon fiber filament (4-1) to enable the carbon fiber filament (4-1) to release heat, and when the heat release frequency of the carbon fiber filament (4-1) is consistent with the oscillation frequency of the tester (1), the carbon fiber filament and the tester are coupled to generate large-amplitude gas pressure oscillation in the tester (1);
and the gas supply system is communicated with the pipeline of the inner cavity of the tester (1) and is used for filling gas into the cavity.
2. The carbon fiber heat release and sound production device for solid propellant oscillatory combustion as claimed in claim 1, characterized in that the horizontal distance between the two electrodes (4-3) and one of the open ends of the tester (1) is 1/4 of the total length of the tester (1).
3. The carbon fiber heat release and sound production device for the oscillatory combustion of the solid propellant as claimed in claim 1 or 2, wherein the cross section of the tester (1) is rectangular or square.
4. The carbon fiber heat release and sound production device for the oscillating combustion of the solid propellant as claimed in claim 1 or 2, wherein two heat insulation supports (4-2) are arranged at intervals in the front-back direction or in the up-down direction.
5. The carbon fiber heat release and sound production device for the oscillatory combustion of the solid propellant as recited in claim 1 or 2, characterized in that both of the electrodes (4-3) are metal columns, and each of the metal columns is provided with a thread along the length direction thereof for supporting and spacing the carbon fiber filaments (4-1) of each circle.
6. The carbon fiber heat release and sound production device for the oscillatory combustion of the solid propellant as recited in claim 1 or 2, characterized in that the signal source (11) is a function generator (5) and a power amplifier (6) which are connected, and the power amplifier (6) is connected with each electrode (4-3).
7. The carbon fiber heat release and sound production device for the oscillatory combustion of the solid propellant is characterized in that a plurality of pressure sensors (3) are arranged on the outer wall of the tester (1) at intervals along the length of the tester, and each pressure sensor (3) is connected with a data acquisition system (12).
8. The carbon fiber heat release and sound production device for solid propellant oscillatory combustion is characterized in that the number of the pressure sensors (3) is 3, and the pressure sensors are respectively located at two ends of the tester (1) and at the length of 1/2 pipes.
9. A heat release device is characterized by being placed in a tester (1), wherein the tester (1) is a horizontally placed square pipe body, and an inner cavity of the tester is used as a cavity for simulating pressure oscillation in a combustion chamber of a rocket engine; and the modal frequency of the acoustic cavity is known;
the heat release device comprises:
the two heat insulation supporting pieces (4-2) are plate bodies, are arranged at intervals and are parallel;
two electrodes (4-3) which are both cylindrical bodies, wherein each electrode (4-3) vertically penetrates through the two heat insulation supporting members (4-2); the horizontal distances between each electrode (4-3) and one open end of the tester (1) are equal;
the carbon fiber wires (4-1) are wound on the parts, located between the two heat insulation supporting pieces (4-2), of the two electrodes (4-3) in a reciprocating mode, and the carbon fiber wires (4-1) wound adjacently are not attached to each other; the carbon fiber wire (4-1) is connected with a signal source (11), the signal source (11) is used for transmitting signal waves, so that the carbon fiber wire (4-1) releases heat, when the heat release frequency of the carbon fiber wire (4-1) is consistent with the oscillation frequency of the tester (1), the carbon fiber wire and the tester are coupled, and large-amplitude gas pressure oscillation is generated in the tester (1).
10. The working method of the carbon fiber heat release and sound production device for the oscillating combustion of the solid propellant is characterized by comprising the following steps of:
the tester (1) with two closed ends is filled with nitrogen and reaches a set pressure;
the function generator (5) outputs simple harmonic electric signals with set frequency and amplitude, the simple harmonic electric signals are transmitted to the power amplifier (6), and then the simple harmonic electric signals are transmitted to the carbon fiber filaments (4-1) of each circle through the electrodes (4-3); the set frequency is 1/2 of the first-order acoustic modal oscillation frequency of the tester (1);
the carbon fiber wires (4-1) in each circle periodically release heat along with the periodic change of simple harmonics, the heat release frequency of the carbon fiber wires (4-1) is equal to the first-order acoustic mode oscillation frequency corresponding to the tester (1), and the first-order acoustic mode oscillation frequency are coupled to generate large-amplitude gas pressure oscillation in the tester (1).
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| CN113676827B (en) * | 2021-08-25 | 2024-07-12 | 西北工业大学 | Direct blowing type frequency conversion oscillation experimental device for measuring frequency response function of solid propellant |
| CN113686580B (en) * | 2021-08-25 | 2024-05-10 | 西北工业大学 | Standing wave oscillation experimental device for simulating nonlinear acoustic vibration mode of engine combustion chamber |
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