Solid propellant non-standing wave type T-shaped burner

Abstract

The invention discloses a solid propellant non-standing wave type T-shaped combustor which is characterized in that a tube cavity of the combustor is in a closed straight tube shape, a fixed propellant is installed at any end of the tube cavity of the combustor, pulse holes are formed in the side wall of the tube cavity and used for applying pulses into the tube cavity, a micro-perforated plate is installed in the tube cavity, and the pulse holes are communicated with the micro-perforated plate. The micro-perforated plate is arranged perpendicular to the trend of the pipe cavity, a plurality of pressure reducing holes are uniformly formed in the micro-perforated plate, and the pressure reducing holes are used for enabling the pulse airflow to pass through, touch the end part of the pipe cavity, return again and pass through the pressure reducing holes again, so that the pressure intensity of the pulse airflow is reduced; therefore, the fixed propellant can feel pulse airflows with multiple different pressure intensities in the combustion process, and the performance of the fixed propellant under the multiple different pressure intensities can be conveniently researched; according to the invention, a multi-frequency working condition is realized in a shorter time through a single experiment, so that the test efficiency and the coverage range are improved; the performance testing efficiency of the solid propellant burner can be improved while the testing cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of solid propellant unstable combustion response testing, and particularly relates to a non-standing wave type T-shaped combustor for solid propellants. Background Art

[0002] Solid propellants are widely used in the propulsion systems of spacecraft such as rockets and missiles, and their combustion performance directly affects the flight performance of spacecraft and the success of missions. However, during the combustion process of solid propellants, combustion instability phenomena often occur, and their main feature is the periodic pressure oscillation in the combustion chamber. Therefore, exploring unstable combustion testing methods and deeply understanding the mechanism of solid propellant combustion instability can provide effective experimental data and theoretical basis for solving combustion instability problems, and is of great significance for the research on solid propellant unstable combustion.

[0003] Currently, experimental research methods for unstable combustion include T-shaped combustors, rotary valve methods, modulated nozzle methods, impedance tubes, magnetometers, etc. Among them, T-shaped combustors are widely adopted by researchers due to their mature technology. Through continuous improvement, measurements have been carried out on propellants with different formulations in different laboratories, and some relatively satisfactory data have been obtained. Its principle is to apply an oscillating pressure excitation related to the natural frequency of the combustor acoustic cavity to the solid propellant, so as to form a standing wave in the combustion chamber, thereby measuring the pressure coupling response characteristics. However, at the same time, the structural design of the T-shaped combustor determines that it can only resonate at specific natural frequencies. In this way, experiments can only be carried out under these specific frequency conditions, and cannot cover the combustion instabilities in other frequency ranges. In a typical experiment, there is one fundamental frequency. This limits the breadth of research. For complex combustion phenomena that require analysis in multiple frequency ranges, the T-shaped combustor appears to be insufficient. The pressure coupling response function Rp is usually used to describe the nonlinear feedback relationship between the dynamic change of the combustion chamber pressure and the propellant combustion rate, and is the core parameter for analyzing the mechanism of combustion instability.

[0004] Therefore, there is an urgent need to improve the solid propellant combustion instability testing device and method at present. It is necessary not only to ensure the stability of the test, but also to solve the problems of low test efficiency and long experimental period caused by single-frequency testing. The test goal of multiple frequencies in one experiment should be achieved. At present, the experimental test of the T-shaped combustor can only simulate a specific working condition (the natural frequency of the combustion chamber), and cannot meet the test requirements of comprehensively covering multiple frequencies. Summary of the Invention

[0005] The purpose of the present invention is to provide a non-standing wave type T-shaped combustor for solid propellants to solve the problem that the combustion data obtained from the single experiment test of the combustor at present can only be the natural frequency, and cannot meet the test requirements of multiple frequencies.

[0006] The present invention adopts the following technical solution: a solid propellant non-standing wave type T-shaped burner. The lumen of the burner is a closed straight tube shape. Fixed propellant is installed at any one end of the lumen of the burner. Pulse holes are provided on the side wall of the lumen, and the pulse holes are used to apply pulses into the lumen. A perforated plate is installed in the lumen, and the perforated plate is arranged perpendicular to the direction of the lumen. A plurality of pressure reducing holes are evenly provided on the perforated plate, and the pressure reducing holes are used for the pulsed air flow to consume energy by rubbing against them when passing through the pressure reducing holes. The pulse energy is changed multiple times through repeated folding back, so that the fixed propellant can feel pulsed disturbances of multiple different frequencies during the combustion process, thereby facilitating the study of the combustion performance of the fixed propellant under multiple frequency excitations.

[0007] Furthermore, a second pressure sensor is installed on the side wall of the lumen of the burner, near the solid propellant; a first pressure sensor is installed on the side wall of the lumen of the burner, near the perforated plate.

[0008] Furthermore, the burner is used to obtain the pressure coupling response function of the propellant, and the obtaining method is as follows:

[0009] Step 1: During the combustion process of the propellant, when the pressure in the burner reaches a predetermined value, a first pulse is applied into the burner; and a second pulse is applied into the burner after the propellant burns out.

[0010] Step 2: Use the first pressure sensor and the second pressure sensor to monitor the pressure in the burner in real time; take the time-domain information of the first sensor pressure array after the second pulse is applied as the input, and take the time-domain information of the second sensor pressure array after the second pulse is applied as the output, and use the system identification method to obtain the damped attenuation transfer function.

[0011] Step 3: Take the time-domain information of the first sensor pressure array after the first pulse is applied as the input, and take the product of the time-domain information of the second sensor pressure array after the first pulse is applied and the damped attenuation transfer function as the output, and use the system identification method to obtain the burning surface response transfer function, and perform system simulation according to the burning surface response transfer function to obtain the pressure coupling response function.

[0012] The beneficial effects of the present invention are as follows:

[0013] The present invention realizes multi-frequency working conditions in a shorter time through a single experiment, thereby improving the test efficiency and coverage; it can improve the performance test efficiency of the solid propellant burner while reducing the test cost.

[0014] The burner of the present invention only fixes and loads the propellant at one end of the tube cavity, while in the prior art, the propellant is loaded on both sides of a conventional burner. Therefore, the present invention significantly reduces the amount of propellant used; and by applying two pulse excitations during the combustion process of the propellant, wide-frequency oscillation data acquisition can be achieved, improving the test efficiency.

[0015] The micro-perforated plate of the present invention can achieve the effect of pressure oscillation damping and form a non-standing wave type combustion response. The material of the micro-perforated plate is 30CrMnSi; by utilizing the better sound absorption ability of the decompression holes, it has a strong damping effect on the oscillating pressure, and finally forms a non-standing wave type pressure oscillation, generating oscillations of different frequencies. Thus, in the case of a single experiment, multi-frequency combustion response data acquisition can be achieved, realizing the study of the wide-frequency characteristics of the unstable combustion of solid propellants. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of the burner of the present invention;

[0017] Figure 2 is a schematic structural diagram of the micro-perforated plate;

[0018] Figure 3 is a test pressure curve graph of the burner in Example 1;

[0019] Figure 4 is an FFT processing result graph of the burner of the present invention under the condition of double pulses;

[0020] Figure 5 is an FFT processing result graph of the burner in the prior art under the condition of double pulses;

[0021] Figure 6 is a wide-frequency pressure coupling response function curve of the propellant obtained by the present invention.

[0022] Wherein: 10, tube cavity; 11, micro-perforated plate; 12, fixed propellant; 13, first cavity; 14, second cavity; 15, decompression hole; 16, pulse hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0024] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more. The "direction" in the present invention is described based on the direction of the present invention when it is in Figure 1 the state.

[0025] The present invention discloses a solid propellant non-standing wave type T-shaped burner. As Figure 1 shown, the lumen 10 of the burner is composed of five sections of lumens, and the lumens are connected by flange bolts. The lumen 10 of the burner is divided into a first cavity 13 and a second cavity 14 by a micro-perforated plate 11. A fixed propellant is installed at the right end of the lumen 10 of the burner, and a micro-perforated plate 11 is installed near the left end of the lumen 10 of the burner.

[0026] The lumen 10 of the burner is a closed straight cylinder shape. A fixed propellant 12 is installed at any end of the lumen 10 of the burner. Pulse holes 16 are provided on the side wall of the lumen 10. The pulse holes 16 are used to apply pulses into the lumen 10. As Figure 2 shown, a micro-perforated plate 11 is installed in the lumen 10. The micro-perforated plate 11 is arranged perpendicular to the direction of the lumen 10. A plurality of pressure relief holes 15 are evenly provided on the micro-perforated plate 11. The pressure relief holes 15 are used for the pulse air flow to consume energy by rubbing against each other when passing through the pressure relief holes 15, and the pulse energy is changed multiple times by repeated folding back, so that the fixed propellant 12 can feel multiple different frequency pulse disturbances during the combustion process, and thus it is convenient to study the combustion performance of the fixed propellant 12 under multiple frequency excitations.

[0027] A second pressure sensor is installed on the side wall of the lumen 10 of the burner, near the solid propellant; a first pressure sensor is installed on the side wall of the lumen 10 of the burner, near the micro-perforated plate 11.

[0028] The aperture of the pressure relief holes 15 of the micro-perforated plate 11 is preferably 1 mm - 3 mm. The depth of the pressure relief holes 15 of the micro-perforated plate 11 is 2 mm - 3 mm. The micro-perforated plate 11 is threadedly connected to the lumen 10 of the burner, and the distance from the installation position of the micro-perforated plate 11 to the nearest end of the lumen 10 is 50 - 110 mm.

[0029] By ensuring the aperture of the pressure relief holes 15 of the micro-perforated plate 11, a considerable sound absorption frequency band and sound absorption coefficient can be obtained in the lumen 10 of the burner without filling porous sound-absorbing materials.

[0030] The sound absorption mechanism of the micro-perforated plate 11 can be described as follows: The pressure relief holes 15 on the micro-perforated plate 11 have an acoustic impedance similar to that of air. The pressure relief holes 15 consume energy through friction with the air column and are a resonance sound absorber with a high acoustic resistance and a low acoustic mass. Usually, an air back cavity is also introduced to improve the sound absorption performance. In the micro-perforated plate 11, the pressure relief holes 15 have acoustic resistance and acoustic reactance, and the first cavity 13 provides pure acoustic reactance. The sound absorption coefficient α when the sound wave is normally incident is calculated according to the following formula:

[0031]

[0032] Where,

[0033]

[0034] In the formula, d is the diameter of the pressure relief holes 15, t is the thickness of the micro-perforated plate 11, both in mm; ν is the kinematic viscosity of air; D is the thickness of the first cavity 13, p is the perforation rate of the micro-perforated plate 11, ω is the angular frequency, k is a constant of the micro-perforated plate 11, r is the relative acoustic resistance rate, and m is the relative acoustic mass.

[0035] To make the sound absorption coefficient reach the peak value, the size of the micro-perforated plate 11 is designed to satisfy the resonance frequency f0 of its burner:

[0036]

[0037] Where, 2πω0 = f0.

[0038] Therefore, the design of the micro-perforated plate 11 has the best sound absorption effect at the resonance frequency.

[0039] The existing method for obtaining the pressure coupling response function of a burner is as follows:

[0040] When the propellant burns in the burner, after the pressure of the burner reaches a steady state, a first pulse excitation is applied, and the oscillating pressure of the burner at this time is measured. Then, after filtering out the direct current, the coefficient (including the damping and burning surface coefficients) ɑ1 of the pressure oscillation decay is calculated.

[0041] When the propellant is completely burned and the pressure in the burner just begins to drop, a second pulsed excitation is applied, and the coefficient ɑ2 of the decay of the second pressure oscillation is measured, assuming that the system damping of these two decays remains unchanged. Then, according to the two decay coefficients, the burning surface gain coefficient can be obtained:

[0042] α c = α1 - α2

[0043] Then, based on the propellant parameters of the burner, the burner length, and the relationship between acoustic energy, the relationship between the burning surface gain coefficient and the pressure coupling response function Rp can be obtained, that is:

[0044]

[0045] Among them, the average pressure is The measured average burning rate is The propellant density is ρ p ; the burner length is L; the theoretical sound speed (depending on the propellant combustion temperature) is a; the actual sound speed is a m , (a m = 2fL), the ratio of the propellant burning surface area to the channel area is S b / S c .

[0046] Therefore, the prior art can only be carried out under these specific frequency conditions and cannot cover the combustion instability in other frequency ranges. In a typical experiment, there is a fundamental frequency. This limits the breadth of research. For complex combustion phenomena that require analysis in multiple continuous frequency ranges, the burner is insufficient.

[0047] The burner of the present invention is used to obtain the pressure coupling response function of the propellant, and the obtaining method is as follows:

[0048] Step 1: During the combustion process of the propellant, when the pressure in the burner reaches a predetermined value, a first pulse is applied to the burner; and after the propellant is completely burned, a second pulse is applied to the burner;

[0049] Step 2: Use the first pressure sensor and the second pressure sensor to monitor the pressure in the burner in real time; take the time-domain information of the first sensor pressure array after the second pulse is applied as the input, and take the time-domain information of the second sensor pressure array after the second pulse is applied as the output, and use the system identification method to obtain the damping attenuation transfer function;

[0050] Step 3: Take the time-domain information of the first sensor pressure array after the first pulse is applied as the input, and take the product of the time-domain information of the second sensor pressure array after the first pulse is applied and the damping attenuation transfer function as the output, and use the system identification method to obtain the burning surface response transfer function, and perform system simulation according to the burning surface response transfer function to obtain the pressure coupling response function.

[0051] Among them, the system identification method selects MATLAB software.

[0052] Among them, the specific time for applying the second pulse is: when the propellant burns out and the pressure of the burner just starts to drop, the initial value of the pressure drop is the pressure in the burner when the propellant burns out.

[0053] Therefore, based on the input and output data, different model structures (zeros and poles) and parameters are selected for system identification to obtain the burning surface response transfer function. Based on the burning surface response transfer function, a pulse containing the experimental oscillation frequency is input for system simulation, and analysis and calculation are performed on the burning surface response transfer function for R p , and the broadband pressure coupling response function of the propellant can be obtained through one calculation.

[0054] Example 1

[0055] The solid propellant selected in this example is a hydroxyl-terminated polybutadiene three-component composite propellant. The length of the burner selected in this example is 1 m. The solid propellant is fixed at the right end of the tube cavity 10. The micro-perforated plate 11 is fixed inside the tube cavity 10 and near the left end of the tube cavity 10. The pulse excitation device is installed inside the tube cavity 10 through the pulse hole 16 and near the micro-perforated plate 11. The first pressure sensor and the second pressure sensor are respectively installed inside the tube cavity 10, with the first pressure sensor near the micro-perforated plate 11 and the second pressure sensor near the fixed propellant.

[0056] Among them, the aperture of the pressure-reducing hole 15 of the micro-perforated plate 11 is 2 mm, the thickness of the micro-perforated plate 11 is 3 mm, the diameter of the micro-perforated plate 11 is 90 mm, the inner diameter of the tube cavity 10 of the burner is 90 mm, the distance between the micro-perforated plate 11 and the left end of the tube cavity 10 is 60 mm, the distance between the micro-perforated plate 11 and the right end of the tube cavity 10 is 940 mm, the distance between the first pressure sensor near the micro-perforated plate 11 and the left end of the tube cavity 10 is 130 mm, the distance between the first pressure sensor and the micro-perforated plate 11 in the tube cavity 10 is 70 mm, the distance between the second pressure sensor near the solid propellant and the right end of the tube cavity 10 is 90 mm, and the distance between the second pressure sensor and the solid propellant in the tube cavity 10 is 40 mm. The ratio of the total area of each pressure-reducing hole 15 to the cross-sectional area of the tube cavity 10 is 1:125. The ratio of the thickness of the micro-perforated plate 11 to the length of the tube cavity 10 is 3:1000. The micro-perforated plate 11 divides the tube cavity 10 of the burner into a first cavity 13 and a second cavity 14, and the volume ratio of the first cavity 13 to the second cavity 14 is 60:937.

[0057] The test process is as follows: Connect the ignition circuit, the pulse excitation system, and the pressure acquisition system. Start the ignition button. When the pressure in the burner reaches 6.3 MPa during the combustion process of the solid propellant, apply an 80 MPa pulse excitation. After the propellant combustion ends, apply a second 80 MPa pulse excitation to obtain the pressure change during the entire combustion process of the solid propellant. The measured pressure curve is as Figure 3 shown. In the figure, the red line is the data collected by the second pressure sensor, the black is the data collected by the first pressure sensor, and the blue is the data obtained after filtering the average pressure value from the pressure fluctuation data after applying the two pulses.

[0058] Process the measured pressure curve. Filter the DC component from the measured pressure curve, and then perform a fast Fourier transform (FFT) on the oscillation segment data to obtain its frequency domain information. The frequency domain curve is as Figure 4 shown.

[0059] As Figure 4 shown, it can be seen from the FFT processing results that the formation of non-standing waves results in three first-order oscillation frequencies of 561 Hz, higher-order oscillation frequencies of 1817 Hz and 3954 Hz for the pressure, and at the same time suppresses the amplitude of the first-order oscillation. As Figure 6 shown, the test goal of multiple frequencies in one experiment is achieved, greatly improving the experimental efficiency of measuring the pressure coupling response characteristics.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is:

[0062] When the pressure in the burner reaches 6.6 MPa during the combustion process of the solid propellant, apply an 80 MPa pulse excitation, and do not set the micro-perforated plate 11.

[0063] The frequency domain curve of this comparative example is as Figure 5 shown. From Figure 5 it can be seen that after applying a single pulse, only the first-order oscillation frequency of 176 Hz is measured. Therefore, it can be shown that when the micro-perforated plate 11 is not set, only a single oscillation frequency can be obtained in a single experiment and the experimental efficiency is low.

[0064] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A solid propellant non-standing wave T-type burner, characterized in that: The tube cavity (10) of the burner is in the shape of a closed straight cylinder. A fixed propellant (12) is installed at either end of the tube cavity (10) of the burner. A pulse hole (16) is provided on the side wall of the tube cavity (10). The pulse hole (16) is used to apply pulses into the tube cavity (10). A micro-perforated plate (11) is installed in the tube cavity (10). The micro-perforated plate (11) is arranged perpendicular to the direction of the tube cavity (10). A plurality of pressure relief holes (15) are evenly provided on the micro-perforated plate (11). The pressure relief holes (15) are used to cause the pulse airflow to rub against the pressure relief holes (15) when the pulse airflow passes through the pressure relief holes to consume energy. The pulse energy is changed multiple times by repeated reversal, so that the fixed propellant (12) can feel a plurality of pulse disturbances of different frequencies during the combustion process, so as to facilitate the study of the combustion performance of the fixed propellant (12) under multiple frequency excitations.

2. A solid propellant non-standing wave T-type burner according to claim 1, characterized in that: A second pressure sensor is installed on the side wall of the tube cavity (10) of the burner, close to the solid propellant; and a first pressure sensor is installed on the side wall of the tube cavity (10) of the burner, close to the micro-perforated plate (11).

3. A solid propellant non-standing wave T-type burner according to claim 1, characterized in that: The burner is used to obtain the pressure coupling response function of the propellant, and the obtaining method is: Step 1: During the combustion process of the propellant, when the pressure in the burner reaches a predetermined value, a first pulse is applied to the burner; and after the propellant is completely burned, a second pulse is applied to the burner; Step 2: Using the first pressure sensor and the second pressure sensor to monitor the pressure in the burner in real time; Using the time domain information of the pressure array of the first sensor after the second pulse is applied as input and the time domain information of the pressure array of the second sensor after the second pulse is applied as output, a damping attenuation transfer function is obtained by using a system identification method; Step 3: Using the time domain information of the pressure array of the first sensor after the first pulse is applied as input, and the product of the time domain information of the pressure array of the second sensor after the first pulse is applied and the damping attenuation transfer function as output, the combustion surface response transfer function is obtained by using the system identification method, and the pressure coupling response function is obtained by system simulation based on the combustion surface response transfer function.

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