An underwater acoustic emission burning rate test device for low-frequency weak combustion signal propellant

Abstract

The present invention discloses an underwater acoustic emission burning rate test device for low-frequency weak combustion signal propellant, which belongs to the technical field of solid propellant burning rate test, and comprises: a combustion chamber, a damping layer, a sensor module, a signal preamplifier module, and a data processing module. The damping layer is coated on the sensor module and is close to the combustion chamber. The sensor module collects the sound wave signal generated by the combustion of the propellant, and converts the collected sound wave signal into a charge signal and sends it to the signal preamplifier module. The signal preamplifier module converts the charge signal into a voltage signal, and realizes accurate frequency selection of the voltage signal through signal amplification and filtering, and filters out interference signals outside the preset frequency range. The filtered voltage signal is converted by frequency-voltage conversion, and the converted voltage is output and sent to the data processing module. The data processing module determines the starting and ending points of combustion and calculates the burning rate. Compared with the prior art, the present invention solves the problem that low-frequency weak combustion signal propellant cannot be tested for underwater acoustic emission burning rate.

Description

Technical Field

[0001] The invention belongs to the technical field of solid propellant burning rate testing, and in particular relates to an underwater acoustic emission burning rate testing device for a low-frequency weak combustion signal propellant. Background Art

[0002] The underwater acoustic emission method relies on the wide-band, broad-spectrum signal generated when the propellant strip burns to record the combustion time. The frequency distribution of the acoustic emission signal is related to the characteristics of the solid propellant system and the use environment. It can range from infrasound to ultrasound, and the strength of the signal is the key to whether the acoustic emission can normally obtain effective data. The frequency of the acoustic signal generated by the combustion of a typical solid propellant in a conventional pressure environment is mainly concentrated in the range of 5kHz to 45kHz, and the signal intensity is much higher than the background interference signal. However, due to its working pressure and its own combustion characteristics, the low-frequency weak combustion signal propellant generates a weak acoustic emission signal and a large signal fluctuation. The existing solid propellant underwater acoustic emission burning rate test device is difficult to meet the future high-performance solid propellant combustion performance test needs in terms of combustion signal acquisition, signal recognition, signal analysis, and signal full process monitoring. The underwater acoustic emission burning rate test device currently used in China has the following main defects when conducting burning rate tests on low-frequency weak combustion signal propellants: (1) The principle of underwater acoustic emission burning rate testing is to determine the burning time by collecting the acoustic signal generated by the combustion of the propellant, and to calculate the burning rate based on the length of the propellant combustion. However, when the propellant is ignited, the current signal will be transmitted to the acoustic emission sensor through the water medium and the combustion chamber shell, affecting the collection of the real-time combustion signal. Although the test devices are well grounded, there is still a high probability that test data abnormalities will occur during the test due to interference from electrical signals; (2) Under the wide pressure range of low-frequency weak combustion signal propellants, the extreme environment causes large changes in the propellant combustion signal spectrum. At the same time, due to environmental noise The voltage amplitude of the noise signal introduced by the noise of ... Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an effective and reliable underwater acoustic emission burning rate test device suitable for low-frequency weak combustion signal propellant.

[0004] In order to solve the above technical problems, the present invention discloses an underwater acoustic emission burning rate test device for low-frequency weak combustion signal propellant, comprising: a combustion chamber, a damping layer, a sensor module, a signal preamplification module and a data processing module;

[0005] The combustion chamber is a place where solid propellants burn, and is used for combustion tests under specific pressure and temperature conditions; the damping layer is made of insulating rubber damping material, which is coated on the surface of the sensor module by its own elasticity and is close to the combustion chamber, so as to shield the current signal on the combustion chamber shell and the noise signal in the environment; the sensor module is used to collect the sound wave signal generated by the combustion of the propellant, and convert the collected sound wave signal into a charge signal and send it to the signal preamplifier module, and the frequency of the charge signal is consistent with the frequency of the sound wave signal;

[0006] The signal preamplifier module converts the charge signal input by the sensor module into a voltage signal and conditions and amplifies it. It realizes accurate frequency selection of the voltage signal through filtering, and filters out interference signals outside the preset frequency range. The filtered voltage signal is converted into an output voltage of the signal preamplifier module through frequency-to-voltage conversion, and the frequency of the voltage signal is linearly converted into the output voltage of the signal preamplifier module, and sent to the data processing module;

[0007] The data processing module is used for real-time monitoring of the propellant combustion signal state, determination of the combustion start and end points, and calculation of the burning rate.

[0008] Furthermore, the signal preamplification module includes a charge amplifier, a first filtering module, a first voltage amplifier, a second filtering module, a second voltage amplifier, a third filtering module, and a frequency-to-voltage converter;

[0009] The charge amplifier converts the charge signal collected by the sensor module into an amplified voltage signal and outputs it to the first filtering module; the first filtering module filters the frequency of the received voltage signal to filter out interference signals outside a preset frequency range; the filtered voltage signal is input to the first voltage amplifier, and the first voltage amplifier conditions and amplifies the input voltage signal and outputs an amplitude-amplified voltage signal;

[0010] The first voltage amplifier, the second filter module, the third voltage amplifier, and the third filter module are connected in series, the second filter module and the third filter module further filter out interference signals outside a preset frequency range, and the second voltage amplifier conditions and amplifies the voltage signal output by the second filter module;

[0011] The frequency-to-voltage converter receives the voltage signal output by the third filtering module, performs frequency-to-voltage conversion on the voltage signal, linearly converts the frequency of the voltage signal into the output voltage of the frequency-to-voltage converter, and sends it to the data processing module.

[0012] Furthermore, the sensor module includes a base, a compression nut, an acoustic emission sensor, and a screw;

[0013] When the combustion chamber is a hollow cylinder and a flat surface with an area larger than that of the base is left on the outer surface of the bottom: the base is fixed to the flat surface of the combustion chamber by screws to fix the position of the acoustic emission sensor; the clamping nut is connected to the base by threads, the acoustic emission sensor is placed in the base, and the acoustic emission sensor is pressed against the flat surface by the clamping nut; the response frequency range of the acoustic emission sensor is 15000 to 75000 Hz.

[0014] Furthermore, the flat table surface is used to increase the contact area between the acoustic emission sensor and the combustion chamber, and the acoustic emission sensor adjusts the pressure between the acoustic emission sensor and the flat table surface through a torque wrench to make it a constant value.

[0015] Furthermore, the damping layer material is selected from one of natural rubber, nitrile rubber, chloroprene rubber, butyl rubber, and styrene-butadiene rubber, and has a thickness of 0.1 to 0.8 mm.

[0016] Furthermore, the first filtering module, the second filtering module and the third filtering module all filter the noise frequencies lower than 1000 Hz and higher than 80000 Hz.

[0017] Furthermore, the frequency-to-voltage converter linearly converts the frequency of the voltage signal of 0 to 100,000 Hz into an output voltage of 0 to 10 volts.

[0018] Furthermore, before performing frequency-voltage conversion, the frequency-voltage converter first performs low-voltage amplitude filtering on the input voltage signal, and the voltage signal with an amplitude below 1.5 volts is not subjected to frequency-voltage conversion, so as to filter out the low-amplitude interference frequency after filtering by the first filtering module, the second filtering module, and the third filtering module.

[0019] Furthermore, the charge amplifier, the first filter module, the first voltage amplifier, the second filter module, the second voltage amplifier, the third filter module, and the frequency-voltage converter all use independent power isolators for power isolation, and are all shielded and installed in an all-aluminum shell.

[0020] Furthermore, the data processing module converts the received voltage signal into a real-time combustion curve, sets a combustion signal voltage threshold, and adjusts the combustion signal voltage threshold within the range of 0 to 6V as a criterion for starting to count the combustion start and end point confirmation data. When n consecutive confirmation data are all higher than the combustion signal voltage threshold, the timing starts, and when n consecutive confirmation data are all lower than the combustion signal voltage threshold, the timing ends, which is used to confirm the start and end time of the propellant combustion, and calculate the burning rate by dividing the length of the propellant strip by the start and end time; <n<1000。

[0021] The beneficial effects of the present invention compared with the prior art are:

[0022] (1) Compared with the conventional underwater acoustic emission combustion rate test device, the combustion chamber used in the present invention adds a table, a sensor module base, and a sensor module clamping nut, and the sensor module base and the sensor module clamping nut are fixed by a torque wrench, thereby increasing the contact area between the acoustic emission sensor and the combustion chamber, fixing the pressure between the acoustic emission sensor and the combustion chamber, and improving the effectiveness and consistency of the acoustic emission sensor in receiving low-frequency weak combustion signals;

[0023] (2) Compared with the traditional underwater acoustic emission burning rate test device, the present invention adds a damping layer between the combustion chamber and the acoustic emission sensor to shield the electrical signal on the combustion chamber shell and the low-frequency signal and weak medium and high-frequency interference signal in the environment, effectively distinguishing the low-frequency weak combustion signal of the propellant from the noise signal, and greatly improving the success rate of the underwater acoustic emission burning rate test of the propellant with a low-frequency weak combustion signal and the validity of the test data;

[0024] (3) Compared with the traditional underwater acoustic emission burning rate test device, the present invention uses frequency / voltage conversion to monitor the characteristic combustion frequency of the low-frequency weak combustion signal propellant, replacing the traditional voltage amplification method, and fundamentally eliminating the influence of low-frequency environmental noise (below 15000Hz) and high-frequency (above 80000Hz) interference signals on the burning rate test results;

[0025] (4) Compared with the traditional underwater acoustic emission burning rate test device, the present invention designs a data processing module with adjustable ignition voltage, adjustable combustion signal voltage threshold, and adjustable combustion start and end point confirmation data quantity, so as to realize stable ignition of propellants with different ignition energies, ensure the reliability of ignition, realize combustion timing of propellants with different combustion frequencies, ensure the authenticity of combustion time, realize accurate judgment of combustion start and end points of different types of propellants, and ensure the accuracy of test data;

[0026] (5) The underwater acoustic emission burning rate test device used in the present invention breaks through the technical bottleneck that low-frequency weak combustion signal propellants cannot be tested for underwater acoustic emission burning rate, and has good single-batch burning rate test accuracy;

[0027] (6) The underwater acoustic emission burning rate device used in the present invention is implemented in accordance with relevant national military standards during the test process. The damping layer is made of common damping rubber material. The test device is simple, and the test operation process is simple and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a functional structure diagram of a low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device according to an embodiment of the present invention;

[0029] Figure 2 A cross-sectional view of a combustion chamber casing according to an embodiment of the present invention;

[0030] Figure 3 A cross-sectional view and a top view of a sensor module base according to an embodiment of the present invention;

[0031] Figure 4 A cross-sectional view of a sensor module compression nut according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of assembling a sensor module according to an embodiment of the present invention; DETAILED DESCRIPTION

[0033] The present invention will be described in detail below based on specific embodiments and in conjunction with the accompanying drawings.

[0034] Figure 1 This is a functional structure diagram of a low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device provided by an embodiment of the present invention, Figure 2 , Figure 3 , Figure 4 , Figure 5 A schematic diagram of the structure of an underwater acoustic emission burning rate test device for a low-frequency weak combustion signal propellant provided by an embodiment of the present invention, wherein: Figure 2 is a cross-sectional view of the combustion chamber casing of the device, Figure 3 The following are the cross-sectional view and top view of the sensor module base of the device. Figure 4 This is a cross-sectional view of the sensor module compression nut of the device. Figure 5 This is a schematic diagram of the sensor module assembly for the device.

[0035] The low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device of the embodiment of the present invention is as follows Figure 1 As shown, including:

[0036] Combustion chamber, damping layer, sensor module, signal preamplifier module and data processing module; wherein the signal preamplifier module includes a charge amplifier, a first filter module, a first voltage amplifier, a second filter module, a second voltage amplifier, a third filter module and a frequency-voltage converter.

[0037] In this embodiment, the combustion chamber is a hollow cylinder made of stainless steel, and a flat table with an area slightly larger than the sensor module base is left on the outer surface of the combustion chamber near the bottom. The sensor module includes a base, a clamping nut, an acoustic emission sensor, and a screw. The table is connected to the sensor module base through a screw, and the sensor module base is connected to the sensor module clamping nut through a thread. The damping layer is coated on the surface of the acoustic emission sensor by its own elasticity and is placed in the sensor module base. The acoustic emission sensor is close to the combustion chamber through the sensor module clamping nut and a torque wrench. The sensor module is connected to a charge amplifier, the charge amplifier is connected to a first filter module, the first filter module is connected to a first voltage amplifier, the first voltage amplifier is connected to a second filter module, the second filter module is connected to a second voltage amplifier, the second voltage amplifier is connected to a third filter module, the third filter module is connected to a frequency-voltage converter, and the frequency-voltage converter is connected to a data processing module.

[0038] When conducting underwater acoustic emission burning rate test on low-frequency weak combustion signal propellant, the propellant strip is placed vertically in the inner cavity of the combustion chamber and ignited. The combustion sound signal passes through the damping layer and is received by the acoustic emission sensor. The signal processed by the charge amplifier, the first filter module, the first voltage amplifier, the second filter module, the second voltage amplifier, the third filter module, and the frequency-voltage converter is input into the data processing module for real-time monitoring of the combustion state and calculation of the burning rate data.

[0039] In an alternative embodiment, Figure 2 , Figure 3 , Figure 4 As shown, a flat table surface slightly larger than the sensor module is reserved on the outer surface of the combustion chamber near the bottom. The table surface is connected to the sensor module base through screws, and the sensor module base is connected to the sensor module clamping nut through threads.

[0040] In an alternative embodiment, Figure 5 As shown, the assembly relationship of the sensor module on the outer surface of the combustion chamber is as follows: the sensor module base 3 is fixed to the table 2 on the outer surface of the combustion chamber 1 by screws 7, the damping layer 4 is wrapped around the outer surface of the acoustic emission sensor 6 by its own elasticity, the acoustic emission sensor 6 wrapped with the damping layer 4 is placed in the sensor module base 3, and the acoustic emission sensor 6 is pressed against the table 2 by the sensor module compression nut 5.

[0041] In an alternative embodiment, Figure 5As shown in the sensor installation diagram in the figure, the table is used to increase the contact surface between the acoustic emission sensor and the combustion chamber. The diameter of the sensor module base 3 is slightly larger than the diameter of the acoustic emission sensor 6 and is used to fix the position of the acoustic emission sensor 6. The sensor module clamping nut 5 tightly presses the acoustic emission sensor 6 on the table 2 through threads, and fixes the pressure between the acoustic emission sensor 6 and the table 2 through a torque wrench to ensure that the installation pressure of the acoustic emission sensor 6 is the same each time, thereby ensuring the consistency of the state of the acoustic emission sensor 6 when receiving the sound signal.

[0042] In an alternative embodiment, Figure 5 As shown in the sensor installation diagram, the damping layer 4 is located between the combustion chamber 1 and the acoustic emission sensor 6, and is used to shield the electrical signals on the combustion chamber shell and the low-frequency signals and weak medium and high-frequency interference signals in the environment. The damping layer 4 material is selected from one of natural rubber, nitrile rubber, chloroprene rubber, butyl rubber, and styrene-butadiene rubber, and the thickness is 0.1 to 0.8 mm.

[0043] In an optional embodiment, the charge amplifier, the first filter module, the first voltage amplifier, the second filter module, the second voltage amplifier, the third filter module, and the frequency-to-voltage converter are isolated from the power supply by independent power isolators and are installed in an all-aluminum housing for shielding.

[0044] In an optional embodiment, the acoustic wave signal of the combustion of the low-frequency weak signal combustion propellant is filtered by the damping layer and received by the acoustic emission sensor, which is reflected on the sensor by outputting a weak charge signal with a frequency characteristic of the order of millivolt, and the frequency of the charge signal is consistent with the frequency of the acoustic wave signal.

[0045] This charge signal is very easy to be interfered with. The charge amplifier amplifies the received charge signal to an appropriate normalized value and converts it into a voltage signal for output. The first filtering module reduces the voltage of the noise signal with a frequency lower than 1000Hz and higher than 80000Hz by 30%. After the voltage signal is conditioned by the first voltage amplifier, the second filtering module, the second voltage amplifier, and the third filtering module, the voltage signal is output to the frequency-voltage converter. The frequency-voltage converter performs low-voltage amplitude filtering on the input voltage signal before performing frequency-voltage conversion. The voltage signal with an amplitude below 1.5V is not subjected to frequency-voltage conversion, which is used to filter out the low-amplitude interference frequency after the first filtering module, the second filtering module, and the third filtering module. At the same time, the frequency-voltage converter linearly converts the input 0-100000Hz propellant combustion sound signal into an output voltage of 0-10V.

[0046] In an optional embodiment, the data processing module converts the received voltage signal into a real-time combustion curve, sets the combustion signal voltage threshold, and adjusts the combustion signal voltage threshold within the range of 0 to 6V as a judgment standard for starting to count the combustion start and end point confirmation data, and adjusts the combustion start and end point confirmation data within the range of 0 to 1000 data, that is, the timing starts when n consecutive confirmation data are higher than the combustion signal voltage threshold, and the timing ends when n consecutive confirmation data are lower than the combustion signal voltage threshold, which is used to finally confirm the start and end time of the propellant combustion, and calculate the burning rate in combination with the length of the propellant strip.

[0047] Compared with the traditional underwater acoustic emission burning rate test device, the noise signal measured by the low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device and the combustion sound signal of the low-frequency weak combustion signal propellant are greatly improved, realizing the underwater acoustic emission burning rate test of the low-frequency weak combustion signal propellant, and the data accuracy is excellent. In this embodiment, the burning rate test results of the traditional underwater acoustic emission burning rate test device and the low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device for the low-frequency weak combustion signal propellant are shown in the following table:

[0048]

[0049] (F) in the above table means that the data is eliminated according to the Grubbs rule in GJB770B and is not included in the calculation of the average value and relative standard deviation. ( / ) means that the test device did not detect the propellant acoustic signal. It can be seen from the test results in the above table that compared with the traditional underwater acoustic emission burning rate test device, the low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device can effectively improve the success rate of the low-frequency weak combustion signal propellant underwater acoustic emission burning rate test and the reliability of the test results. For example, the standard value of the low-frequency weak combustion signal propellant in the table is (10.42±0.13) mm / s, and the average burning rate measured by the low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device is 10.45 mm / s, and the relative standard deviation is 0.089%. However, the traditional underwater acoustic emission burning rate test device has three propellant samples that cannot be tested, and the other two propellant samples are terminated prematurely due to the instability of the device receiving signal, resulting in a significant deviation of the measured burning rate data from the true value.

[0050] The embodiment of the present invention provides an underwater acoustic emission burning rate test device for low-frequency weak combustion signal propellant. On the one hand, the combustion chamber table, sensor module base, and sensor module clamping nut are added, and the sensor module base and sensor module clamping nut are fixed by a torque wrench, thereby increasing the contact area between the acoustic emission sensor and the combustion chamber, fixing the pressure between the acoustic emission sensor and the combustion chamber, and improving the effectiveness and consistency of the acoustic emission sensor receiving low-frequency weak combustion signals. On the second hand, a damping layer is added between the combustion chamber and the acoustic emission sensor to shield the current signal on the combustion chamber shell and the low-frequency signal and weak medium and high-frequency noise interference signal in the environment, effectively distinguishing the low-frequency weak combustion signal of the propellant from the noise signal, and greatly improving the success rate of the underwater acoustic emission burning rate test of the low-frequency weak combustion signal propellant and the effectiveness of the test data. On the third hand, the characteristic combustion frequency of the low-frequency weak combustion signal propellant is monitored by using the frequency-voltage conversion method, replacing the traditional voltage amplification method, and eliminating the influence of low-frequency environmental noise (below 15000Hz) and high-frequency (above 80000Hz) noise signals on the burning rate test results from the root. Fourthly, a data processing module with adjustable ignition voltage, adjustable combustion signal voltage threshold, and adjustable combustion start and end point judgment and confirmation data quantity is designed to achieve stable ignition of propellants with different ignition energies, ensure the reliability of ignition, achieve combustion timing of propellants with different combustion frequencies, ensure the authenticity of combustion time, achieve accurate judgment of combustion start and end points of different types of propellants, and ensure the accuracy of test data. Fifthly, during the burning rate test, it is only necessary to adjust the combustion signal voltage threshold and the number of combustion start and end point judgment and confirmation data to achieve burning rate tests of different types of propellants, and ensure the validity and test accuracy of burning rate test data.

[0051] The invention proposes an underwater acoustic emission burning rate testing device for low-frequency weak combustion signal propellants, which not only breaks through the technical bottleneck that low-frequency weak combustion signal propellants cannot be subjected to underwater acoustic emission burning rate testing, but also has good single-batch burning rate testing accuracy. It can also adjust the ignition voltage, the combustion signal voltage threshold, and the combustion start and end point judgment confirmation data quantity to achieve stable ignition of propellants with different ignition energies, ensure the reliability of ignition, achieve combustion timing of propellants with different combustion frequencies, ensure the authenticity of the combustion time, achieve accurate judgment of the combustion start and end points of different types of propellants, and ensure the accuracy of the test data.

[0052] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0053] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device, characterized in that: It includes a combustion chamber, a damping layer, a sensor module, a signal preamplifier module and a data processing module; The combustion chamber is a place where solid propellants burn, and is used for combustion tests under specific pressure and temperature conditions; the damping layer is made of insulating rubber damping material with a thickness of 0.1 to 0.8 mm, and is coated on the surface of the sensor module by its own elasticity and close to the combustion chamber, so as to shield the current signal on the combustion chamber shell and the noise signal in the environment; the sensor module is used to collect the sound wave signal generated by the combustion of the propellant, and convert the collected sound wave signal into a charge signal and send it to the signal preamplifier module, and the frequency of the charge signal is consistent with the frequency of the sound wave signal; The signal preamplifier module converts the charge signal input by the sensor module into a voltage signal and conditions and amplifies it. It realizes accurate frequency selection of the voltage signal through filtering, and filters out interference signals outside the preset frequency range. The filtered voltage signal is converted into an output voltage of the signal preamplifier module through frequency-to-voltage conversion, and the frequency of the voltage signal is linearly converted into the output voltage of the signal preamplifier module, and sent to the data processing module; The data processing module is used for real-time monitoring of the state of the propellant combustion signal, determination of the combustion start and end points, and calculation of the burning rate; specifically, the data processing module converts the received voltage signal into a real-time combustion curve, sets the combustion signal voltage threshold, and adjusts the combustion signal voltage threshold within the range of 0 to 6V as a judgment standard for starting to count the combustion start and end point confirmation data, and starts counting when n consecutive confirmation data are all higher than the combustion signal voltage threshold, and ends counting when n consecutive confirmation data are all lower than the combustion signal voltage threshold, and is used to confirm the start and end time of the propellant combustion, and calculate the burning rate by dividing the length of the propellant strip by the start and end time; <n<1000。 2. The low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device according to claim 1 is characterized in that: The signal preamplification module includes a charge amplifier, a first filtering module, a first voltage amplifier, a second filtering module, a second voltage amplifier, a third filtering module, and a frequency-to-voltage converter; The charge amplifier converts the charge signal collected by the sensor module into an amplified voltage signal and outputs it to the first filtering module; The first filtering module filters the frequency of the received voltage signal to filter out interference signals outside a preset frequency range; the filtered voltage signal is input to the first voltage amplifier, and the first voltage amplifier conditions and amplifies the input voltage signal and outputs an amplitude-amplified voltage signal; The first voltage amplifier, the second filter module, the third voltage amplifier, and the third filter module are connected in series, the second filter module and the third filter module further filter out interference signals outside a preset frequency range, and the second voltage amplifier conditions and amplifies the voltage signal output by the second filter module; The frequency-to-voltage converter receives the voltage signal output by the third filtering module, performs frequency-to-voltage conversion on the voltage signal, linearly converts the frequency of the voltage signal into the output voltage of the frequency-to-voltage converter, and sends it to the data processing module.

3. The low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device according to claim 1 is characterized in that: The sensor module includes a base, a compression nut, an acoustic emission sensor, and a screw; When the combustion chamber is a hollow cylinder and a flat surface with an area larger than that of the base is left on the outer surface of the bottom: the base is fixed to the flat surface of the combustion chamber by screws to fix the position of the acoustic emission sensor; the clamping nut is connected to the base by threads, the acoustic emission sensor is placed in the base, and the acoustic emission sensor is pressed against the flat surface by the clamping nut; the response frequency range of the acoustic emission sensor is 15000 to 75000 Hz.

4. The low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device according to claim 3 is characterized in that: The flat table surface is used to increase the contact area between the acoustic emission sensor and the combustion chamber. The acoustic emission sensor adjusts the pressure between the acoustic emission sensor and the flat table surface through a torque wrench to make it a constant value.

5. The low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device according to claim 1 is characterized in that: The damping layer material is selected from one of natural rubber, nitrile rubber, chloroprene rubber, butyl rubber and styrene-butadiene rubber.

6. The low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device according to claim 2 is characterized in that: The first filtering module, the second filtering module and the third filtering module all filter the noise frequencies lower than 1000 Hz and higher than 80000 Hz.

7. The low-frequency weak combustion signal propellant underwater acoustic emission burning rate test device according to claim 2 is characterized in that: The frequency-to-voltage converter linearly converts the frequency of a voltage signal of 0 to 100,000 Hz into an output voltage of 0 to 10 volts.

8. The underwater acoustic emission burning rate test device for low-frequency weak combustion signal propellant according to claim 7 is characterized in that: The frequency-to-voltage converter performs low-voltage amplitude filtering on the input voltage signal before performing frequency-to-voltage conversion. The voltage signal with an amplitude below 1.5 volts is not subjected to frequency-to-voltage conversion, so as to filter out the low-amplitude interference frequency after filtering by the first filtering module, the second filtering module, and the third filtering module.

9. The underwater acoustic emission burning rate test device for low-frequency weak combustion signal propellant according to claim 2 is characterized in that: The charge amplifier, the first filter module, the first voltage amplifier, the second filter module, the second voltage amplifier, the third filter module, and the frequency-voltage converter are all isolated by independent power supply isolators and are all shielded and installed in an all-aluminum shell.

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