Device and method for evaluating the intensity of thermal stimulation response under structural constraints of solid propellant

Abstract

The present invention discloses a device for evaluating the intensity of thermal stimulus response under structural constraints of solid propellant, belonging to the field of aerospace power technology; the present invention establishes a set of devices and methods for evaluating the intensity of thermal stimulus response under structural constraints of solid propellant according to three indicators: shock wave velocity, shock wave pressure, and aluminum witness plate dent volume, and the device structure includes upper and lower clamps, a heater shell, a heating rod, a thermocouple, an explosion-proof box, a propellant sample, a constraint shell, an aluminum witness plate, a pressure sensor, a heating control device, an LED point light source, a parabolic mirror group, and a CCD high-speed camera. The present invention can change the structural constraint strength of the sample by using different constraint shells, obtain the thermal response law, and can also capture a clear shock wave structure, and the device structure is simple, practical, reliable, and highly safe.

Description

Technical Field

[0001] The present invention relates to the field of aerospace propulsion technology, and in particular to a device and method for evaluating the intensity of thermal stimulation response under structural constraints of a solid propellant. Background Art

[0002] Solid propellant is a kind of explosive that releases energy through combustion and can convert the contained chemical energy into high-speed jet kinetic energy. It is widely used in aerospace vehicles and rocket missile weapons. Solid propellant can usually exist stably under appropriate storage conditions, but when it is continuously stimulated by unexpected heat sources, it may heat up and catch fire, causing combustion and explosion accidents. With the increasing demand for high-energy and high-burning-rate propellants in aerospace and military, the safety of solid propellants under thermal stimulation and the intensity of combustion and explosion have become more important.

[0003] Solid propellants are usually confined in the engine casing, and their response behavior under thermal load stimulation is very different from that of powder samples and unconfined propellants. Therefore, it is not enough to rely solely on differential scanning calorimetry, thermogravimetric analysis, infrared analysis and other analytical methods to study the thermal decomposition characteristics of propellants. In order to meet the needs of studying the intensity test and intensity assessment of the thermal response of propellants under structural constraints, it is necessary to design and manufacture a constraint device similar to the engine casing in order to carry out thermal stimulation tests of various propellants under structural constraints.

[0004] By manufacturing cooking devices of various shapes and sizes to conduct thermal stimulation tests on solid propellants, it is possible to obtain propellant response behaviors that are closer to the actual thermal stimulation environment, and to grade the thermal stimulation response intensities of multiple propellants under the same conditions. However, the existing propellant thermal stimulation devices are one-piece closed shells that are disposable, making it difficult to achieve convenient switching of different structural constraint strengths, and the judgment of the response intensity is based on phenomena such as the degree of shell fragmentation. In order to solve the above problems, the present invention proposes a device for evaluating the thermal stimulation response intensity of solid propellants under structural constraints. Summary of the invention

[0005] 1. Technical Problems to be Solved by the Present Invention

[0006] The purpose of the present invention is to provide a device for evaluating the intensity of thermal stimulation response under structural constraints of solid propellant to solve the problems mentioned in the background technology.

[0007] 2. Technical solution

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The present invention improves the solid propellant thermal stimulation test device, and realizes the replaceability of components with different constraint strengths on the test device by modularizing the constraint structure; the shock wave velocity is calculated by the image of the detonation process captured by the CCD high-speed camera schlieren system, the temperature at different positions of the device can be monitored by thermocouples, and the shock wave overpressure is monitored by pressure sensors. The propellant response intensity can be comprehensively evaluated by combining the shock wave velocity, shock wave pressure, and the volume of the dent on the aluminum witness plate; a set of modular experimental devices is further built and a response intensity evaluation method based on multiple measurement data is proposed. Specifically, it includes the following contents:

[0010] A device for evaluating the intensity of thermal stimulus response under structural constraints of a solid propellant, the device comprising an explosion-proof box, a heater, a constraint structure, a data acquisition system, and a schlieren system, wherein:

[0011] The explosion-proof box includes a glass window and a box body;

[0012] The heater comprises a heater housing, a heating rod, a wire, and a heating control device;

[0013] One end of the heating rod is inserted into the heater housing, and the other end is connected to the heating control device through a wire; the heating control device is used to control the heating rod to achieve electric heating; in addition to supporting the heating rod, the heater housing can also transfer heat more evenly to the surface in contact with the propellant sample;

[0014] The restraint structure comprises an upper clamp, a lower clamp, a restraint housing and fastening bolts;

[0015] The restraining shell contains a propellant sample, and the restraining shell and the heater shell are connected by threads and sealed with a rubber ring; the lower clamp is fixedly connected to the bottom surface of the box body, and the upper clamp and the lower clamp are respectively arranged on the upper and lower sides of the restraining shell to fix the restraining shell, and the upper clamp and the lower clamp are connected by fastening bolts; in order to quantify the intensity of the thermal stimulus response of the propellant under structural constraints, a prefabricated fragile point with the smallest thickness is arranged on the restraining shell, and a prefabricated fragment structure is installed outside the prefabricated fragile point, which will break when the propellant is detonated, and the prefabricated fragment structure will splash to form directional fragments, impacting the aluminum witness plate and leaving a dent;

[0016] The data acquisition system includes a heater thermocouple, a restraint shell thermocouple, an aluminum witness plate, and a pressure sensor; the heater thermocouple and the restraint shell thermocouple are used to monitor the temperature of the heater shell and the restraint shell respectively; the aluminum witness plate is fixedly installed on the inner wall of the box body close to the prefabricated fragment structure, and the pressure sensor is fixedly installed on the inner bottom surface of the box body close to the aluminum witness plate to measure the shock wave pressure of the propellant detonation process; in order to obtain better shock wave pressure measurement data, the pressure sensor is arranged at a point that divides the distance between the restraint shell and the aluminum witness plate into three equal parts, and is at the three-point point closer to the aluminum witness plate. This arrangement makes it easier to detect shock waves and distinguish shock waves and their wall-impacting reflected waves from the pressure curve.

[0017] The heating control device can control the heating rod to achieve electric heating. The heat is transferred to the propellant sample through the heater shell. The propellant continues to heat up. At a certain moment, ignition will occur and quickly grow into combustion or detonation. The pressure in the closed confinement shell will increase sharply, and finally the prefabricated weak point on the confinement shell will be destroyed. The prefabricated fragment structure will fly out to form directional fragments, leaving dents on the impact aluminum witness plate.

[0018] The Schlieren system includes an LED point light source, an incident parabolic mirror, an exit parabolic mirror, and a CCD high-speed camera; the light beam emitted by the LED point light source becomes parallel light after passing through the incident parabolic mirror and passes through a glass window on one side, and the parallel light is emitted from the glass window on the other side and is reflected by the exit parabolic mirror and converged into a point light beam. The CCD high-speed camera filters the light signal and collects and processes it to output a high-definition Schlieren image; the CCD high-speed camera shoots the propellant detonation process through the glass window on one side of the box.

[0019] Preferably, the heater housing is a copper stepped cylinder with two deep holes at one end, and the deep holes match the heating rod.

[0020] Preferably, in order to avoid that the test device is damaged at other weak structures other than the prefabricated weak point when the propellant is detonated, resulting in unsatisfactory test results, the shortest distance between the front end of the heater thermocouple and the restraint shell thermocouple and the propellant sample is not less than the thickness of the prefabricated weak point.

[0021] Preferably, glass windows are provided on both sides of the explosion-proof box to facilitate the Schlieren system to capture the thermal stimulus response detonation process of the propellant; after each propellant test, the device needs to be disassembled and the glass windows wiped to keep them clean so as not to affect the quality of the captured image.

[0022] Preferably, grooves are provided on both sides of the restraint shell, and the grooves match the upper clamp and the lower clamp.

[0023] Preferably, in order to facilitate the thermal stimulation test under different structural restraint strengths, a variety of restraint shells with prefabricated weak points of different thicknesses are prefabricated. In order to avoid introducing unnecessary variables due to different fragment masses, the thickness of the prefabricated fragment structures on various interchangeable restraint shells are made to be the same. A certain space is left on the side and in the splash direction of the prefabricated fragment structure to ensure that the fragments fly out smoothly and do not collide or scratch with other structures except the aluminum witness plate during the process.

[0024] A method for evaluating the intensity of thermal stimulation response of solid propellant under structural constraints comprises the following steps:

[0025] S1. Prepare a φ10mm×20mm cylindrical propellant sample of a certain component propellant;

[0026] S2, placing the propellant sample prepared in S1 into the restraining shell, connecting the heater shell, fixing the restraining shell with the upper clamp, the lower clamp and the fastening bolts, and then inserting the heating rod;

[0027] S3. Debug the data acquisition system to improve the quality of collected data and seal the explosion-proof box;

[0028] S4. Build and debug the Schlieren system;

[0029] S5. Use the heating control device to control the heating of the heating rod, and monitor the temperature, pressure and video signal from heating to the end of the propellant thermal response combustion process;

[0030] S6. Take out the aluminum witness plate and place it on a horizontal table. Use ultra-fine powder such as fine sand to fill the dents on the witness plate surface. Use a long ruler to gently scrape off the fine sand above the edge of the witness plate. Weigh the mass of the remaining fine sand on the aluminum witness plate. Calculate the volume of the fine sand based on the loose density of the fine sand as a measure of the dent volume and the impact power of the fragments.

[0031] S7, calculating the heating explosion temperature and shock wave velocity according to the images taken by the CCD high-speed camera schlieren system, recording the peak temperature of each thermocouple, the first pressure peak measured by the pressure sensor, and the dent volume of the aluminum witness plate;

[0032] S8. Evaluate the intensity of thermal stimulus response under propellant structural constraints based on the three indicators of shock wave velocity, shock wave pressure, and aluminum witness plate dent volume, and write a test record report.

[0033] 3. Beneficial effects

[0034] (1) Simple structure and reliable operation: The test device of the present invention has only a dozen main parts, which cooperate closely with each other and are tightly connected. The overall operation of the device is reliable and safe.

[0035] (2) Component modularization: The main components of the test device of the present invention can be easily disassembled, especially the restraining shell can be disassembled, so that the remaining medicine or residue inside can be easily removed so as to carry out the next test as soon as possible.

[0036] (3) Serialization of key consumables: Because the prefabricated fragile points and prefabricated fragment structures on the constraint shell are designed to form directional fragments, the constraint shell is a consumable. In order to facilitate thermal stimulation tests under different structural constraint strengths, a variety of constraint shells with prefabricated fragile points of different thicknesses are prefabricated.

[0037] (4) Quantification of response intensity: By measuring the shock wave velocity, shock wave pressure, and the volume of the dent left by the fragments impacting the aluminum witness plate, the intensity of thermal stimulation detonation of the propellant sample under certain conditions can be quantitatively characterized.

[0038] (5) Visualization of response intensity: The schlieren system constructed using a CCD high-speed camera and several optical devices can capture a clear picture of the propellant detonation process. The shock wave structure and propagation process reflected by the air density fluctuation are clearly visible. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic cross-sectional view (front view) of the main structure of the device for evaluating the intensity of thermal stimulus response under structural constraints of solid propellant of the present invention;

[0040] Figure 2 It is a schematic diagram of the heater fixing method of the thermal stimulus response intensity assessment device under the structural constraint of the solid propellant of the present invention (left view);

[0041] Figure 3 This is a schematic diagram of the macroscopic layout of the device for evaluating the intensity of thermal stimulation response under the structural constraints of solid propellant of the present invention (top view).

[0042] In the figure: 1. upper fixture; 2. heater shell; 3. heating rod; 4. heater thermocouple; 5. lower fixture; 6. glass window; 7. box; 8. propellant sample; 9. restraint shell; 10. prefabricated fragment structure; 11. prefabricated weak point; 12. restraint shell thermocouple; 13. aluminum witness plate; 14. pressure sensor; 15. fastening bolt; 16. wire; 17. heating control equipment; 18. LED point light source; 19. incident parabolic mirror; 20. exit parabolic mirror; 21. CCD high-speed camera. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Embodiment 1:

[0045] See also Figure 1-3 , Thermal stimulus response test of a certain GAP composite solid propellant under structural constraints

[0046] See also Figure 1 , Figure 2 , Figure 3 The main structure of the device for evaluating the intensity of thermal stimulus response under structural constraint of solid propellant of the present invention includes clamps 1 and 5, a heater shell 2, a heating rod 3, an explosion-proof box 7, a propellant sample 8, a constraint shell 9, an aluminum witness plate 13, a pressure sensor 14, a heating control device 17, an LED point light source 18, an incident parabolic mirror 19, an exit parabolic mirror 20, and a CCD high-speed camera 21; a thermocouple 4 is embedded in the heater shell 2; the heating rod 3 is connected to the heating control device 17 through a wire 16; a transparent glass window 6 is installed on one side of the explosion-proof box 7; there is a prefabricated fragment structure 10 and a prefabricated fragile point 11 on the constraint shell 9, and a thermocouple 12 is also embedded in one side of the shell; the tightness of the clamp holding the constraint shell can be changed by adjusting the tightness of the fastening bolt 15. The heating control device 17 can control the heating rod 3 to achieve electric heating. The heat is transferred to the propellant sample 8 through the heater shell 2. The propellant continues to heat up. At a certain moment, ignition will occur and quickly grow into combustion or detonation. The pressure in the closed confinement shell 9 increases sharply, and finally the prefabricated fragile point on the confinement shell 9 is destroyed. The prefabricated fragment structure 10 flies out to form directional fragments, which may leave dents after impacting the aluminum witness plate 13. The Schlieren system composed of an LED point light source 18, an incident parabolic mirror 19, an exit parabolic mirror 20, and a CCD high-speed camera 21 can capture the propellant detonation process.

[0047] like Figure 1 As shown in the figure, the pressure sensor is arranged at a point where the distance between the constraint shell and the aluminum witness plate is divided into three equal parts, and it is at a point that is closer to the aluminum witness plate. This arrangement makes it easier to detect the shock wave and distinguish the shock wave and its wall-impacting reflected wave from the pressure curve. A 3mm groove is opened on both sides of the constraint shell to facilitate clamping and prevent the constraint shell from sliding along the axial direction.

[0048] like Figure 3The figure shows a macroscopic layout diagram of the device for evaluating the intensity of thermal stimulus response under the structural constraints of solid propellants of the present invention. The light beam emitted by the LED point light source 18 will become parallel light after passing through the incident parabolic mirror 19 and pass through the glass window on one side. After the parallel light is emitted from the glass window on the other side, it will be reflected by the exit parabolic mirror 20 and converged into a point light beam. The CCD high-speed camera 21 will filter the light signal and collect and process it to output a high-definition Schlieren image.

[0049] The use of the thermal stimulus response intensity assessment device under the constraint of the solid propellant structure of the present invention is as follows: prepare a φ10mm×20mm cylindrical sample of a certain component propellant; put the cylindrical propellant sample into the constraint shell, use a clamp to fix the constraint shell, and sequentially connect the heating control device, the heating rod, the heater shell, and the constraint structure; debug the data acquisition system to make the collected data quality better, and close the explosion-proof box; build and debug the Schlieren system; use the heating control device to control the heating of the heating rod, and monitor the temperature, pressure and video signal from heating to the end of the propellant thermal response combustion process; take out the aluminum witness plate and place it on a horizontal table, using Fill the largest and deepest dent on the witness plate surface with ultrafine powders such as fine sand, gently scrape off the fine sand above the edge of the witness plate with a long ruler, weigh the mass of the remaining fine sand on the aluminum witness plate, and calculate the volume of the fine sand according to the loose density of the fine sand as a measure of the dent volume and the impact power of the fragments; calculate the heating explosion temperature of the propellant and the shock wave velocity after detonation based on the image recorded by the CCD high-speed camera, record the peak temperature of the thermocouple and the first pressure peak measured by the pressure sensor, and the dent volume of the aluminum witness plate; evaluate the intensity of the thermal stimulation response of the propellant under structural constraints based on the shock wave velocity, shock wave pressure, and the dent volume data of the aluminum witness plate.

[0050] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and improved concepts of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A device for evaluating the intensity of thermal stimulus response under structural constraints of solid propellant, characterized in that: The device includes an explosion-proof box, a heater, a restraint structure, a data acquisition system, and a Schlieren system, wherein: The explosion-proof box comprises a glass window (6) and a box body (7); The heater comprises a heater housing (2), a heating rod (3), a wire (16), and a heating control device (17); one end of the heating rod (3) is inserted into the heater housing (2), and the other end is connected to the heating control device (17) via the wire (16); the heating control device (17) is used to control the heating rod (3) to achieve electric heating; The restraining structure comprises an upper clamp (1), a lower clamp (5), a restraining shell (9) and a fastening bolt (15); a propellant sample (8) is contained in the restraining shell (9), and the restraining shell (9) and the heater shell (2) are connected by threads and sealed by a rubber ring; the lower clamp (5) is fixedly connected to the inner bottom surface of the box body (7), and the upper clamp (1) and the lower clamp (5) are respectively arranged on the upper and lower sides of the restraining shell (9) to fix the restraining shell (9), and the upper clamp (1) and the lower clamp (5) are connected by fastening bolts (15); a prefabricated fragile point (11) with the smallest thickness is arranged on the restraining shell (9), and a prefabricated fragment structure (10) is installed outside the prefabricated fragile point (11); The data acquisition system comprises a heater thermocouple (4), a restraint shell thermocouple (12), an aluminum witness plate (13), and a pressure sensor (14); the heater thermocouple (4) and the restraint shell thermocouple (12) are used to monitor the temperature in the heater shell (2) and the restraint shell (9), respectively; the aluminum witness plate (13) is fixedly mounted on the inner wall of the box (7) on one side close to the prefabricated fragment structure (10); the pressure sensor (14) is fixedly mounted on the inner bottom surface of the box (7) on one side close to the aluminum witness plate (13) to measure the shock wave pressure of the propellant detonation process; The schlieren system comprises an LED point light source (18), an incident parabolic mirror (19), an exit parabolic mirror (20), and a CCD high-speed camera (21); the light beam emitted by the LED point light source (18) is transformed into parallel light after passing through the incident parabolic mirror (19) and passes through a glass window (6) on one side; the parallel light is emitted from the glass window (6) on the other side and is reflected by the exit parabolic mirror (20) and converged into a point light beam; the CCD high-speed camera (21) filters the light signal and collects and processes it to output a high-definition schlieren image; the CCD high-speed camera photographs the propellant detonation process through the glass window (6) on one side of the housing (7).

2. A device for evaluating the intensity of thermal stimulation response of solid propellant under structural constraints as claimed in claim 1, characterized in that: The heater housing (2) is a copper stepped cylinder, one end of which is provided with two deep holes, the deep holes matching the heating rod (3).

3. A device for evaluating the intensity of thermal stimulation response of solid propellant under structural constraints as claimed in claim 1, characterized in that: The shortest distance between the front ends of the heater thermocouple (4) and the restraining shell thermocouple (12) and the propellant sample (8) is no less than the thickness of the prefabricated fragile point (11).

4. A device for evaluating the intensity of thermal stimulation response of solid propellant under structural constraints as claimed in claim 1, characterized in that: Grooves are provided on both sides of the restraining shell (9), and the grooves match the upper clamp (1) and the lower clamp (5).

5. The device for evaluating the intensity of thermal stimulation response of solid propellant under structural constraints according to claim 1, characterized in that: A certain amount of space is left on the side and in the splashing direction of the prefabricated fragment structure (10) to ensure that the fragments can fly out smoothly and do not collide or scratch other structures except the aluminum witness plate (13) during the process.

6. The evaluation method used in the device for evaluating the intensity of thermal stimulus response of solid propellant under structural constraints as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Prepare a φ10 mm×20 mm cylindrical propellant sample (8) of a certain component propellant; S2, placing the propellant sample (8) prepared in S1 into the restraining shell (9), connecting the heater shell (2), fixing the restraining shell (9) with the upper clamp (1), the lower clamp (5) and the fastening bolts (15), and then inserting the heating rod (3); S3, debugging the data acquisition system to improve the quality of the collected data, and sealing the explosion-proof box (7); S4. Build and debug the Schlieren system; S5, using the heating control device (17) to control the heating of the heating rod (3), and monitoring the temperature, pressure and video signal from the time of heating to the end of the propellant thermal response combustion and explosion process; S6. Take out the aluminum witness plate (13) and place it on a horizontal table. Use ultrafine powder such as fine sand to fill the indentation on the surface of the aluminum witness plate (13). Use a long ruler to gently scrape off the fine sand above the edge of the aluminum witness plate (13). Weigh the mass of the fine sand remaining on the aluminum witness plate (13). Calculate the volume of the fine sand based on the loose density of the fine sand as a measure of the volume of the indentation and the impact power of the fragments. S7, calculating the heating explosion temperature and the shock wave velocity according to the image captured by the CCD high-speed camera (21) schlieren system, recording the peak temperature of each thermocouple, the first pressure peak measured by the pressure sensor (14), and the dent volume of the aluminum witness plate (13); S8. Evaluate the intensity of the thermal stimulus response under the structural constraints of the propellant based on the three indicators of shock wave velocity, shock wave pressure, and the volume of the dent on the aluminum witness plate (13), and write a test record report.

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