Propellant slow cook-off reaction intensity quantitative evaluation experimental device, method and application

Abstract

The application provides a propellant slow-burning reaction intensity quantitative evaluation experimental device, method and application, and belongs to the field of solid rocket engine safety. The device comprises: a slow-burning bomb comprising a shell and a propellant charge arranged in the shell; a temperature control mechanism comprising a ceramic heating jacket arranged outside the slow-burning bomb; a temperature measuring mechanism comprising a plurality of temperature measuring thermocouples arranged in the propellant charge; a pressure collecting mechanism comprising a pressure sensor arranged at the lower end of the slow-burning bomb and a plurality of overpressure sensors arranged around the slow-burning bomb; a PDV speed measuring mechanism comprising a laser generator and an oscilloscope connected with the laser generator, wherein a PDV optical fiber speed measuring probe is connected to the laser generator, and the PDV optical fiber speed measuring probe is arranged close to the slow-burning bomb. By collecting the internal pressure, temperature change, shock wave overpressure and expansion speed of the shell fragments of the propellant in the slow-burning process, the slow-burning reaction intensity of the propellant is analyzed, and quantitative evaluation of the reaction intensity of the propellant is realized.

Description

Technical Field

[0001] This invention belongs to the field of solid rocket engine safety, and relates to propellant thermal safety performance testing technology, specifically to an experimental device, method and application for quantitative evaluation of the intensity of slow combustion reaction of propellant. Background Technology

[0002] The thermal safety performance of propellants directly affects the efficiency and safety of rocket engines. The intensity of the slow-burn reaction of propellants under slow heating conditions is an important parameter in propellant performance evaluation. Currently, research on the intensity of the slow-burn reaction of propellants mainly relies on qualitative descriptions and empirical data, lacking a systematic and quantitative evaluation method.

[0003] Therefore, there is an urgent need to develop an experimental apparatus and method that can accurately measure the reaction intensity of propellants under different combustion conditions and provide reliable data support. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art and provide an experimental device, method and application for quantitative evaluation of the slow combustion reaction intensity of propellants. It aims to accurately measure the reaction intensity of propellants under slow heating conditions and solves the limitations of qualitative analysis in traditional evaluation methods.

[0005] This invention is achieved through the following technical solution:

[0006] A first aspect of the present invention provides an experimental apparatus for quantitatively evaluating the intensity of a slow-burning reaction of a propellant, comprising:

[0007] A heat-incendiary bomb, mounted on a fixed support, includes a casing and a propellant charge disposed within the casing;

[0008] The temperature control mechanism includes a ceramic heating jacket disposed on the outside of the incendiary bomb;

[0009] The temperature measuring mechanism includes multiple thermocouples disposed within the propellant charge, and the thermocouples are connected to a temperature acquisition device via thermocouple wires.

[0010] The pressure acquisition mechanism includes a pressure sensor located at the lower end of the incendiary bomb and multiple overpressure sensors located around the incendiary bomb.

[0011] The PDV velocity measurement mechanism includes a laser generator and an oscilloscope connected to the laser generator. A PDV fiber optic velocity measurement probe is connected to the laser generator and is positioned close to the incendiary bomb.

[0012] A further improvement of the present invention is that:

[0013] The housing includes a cylindrical outer shell, an upper end cover disposed at the upper end of the cylindrical outer shell, and a lower end cover disposed at the lower end of the cylindrical outer shell, and / or,

[0014] The propellant charge is disposed inside the cylindrical section shell, and the propellant charge has a central hole along the central axis.

[0015] A further improvement of the present invention is that:

[0016] The lower end cap has a central screw hole corresponding to the position of the propellant loading center hole, and the central screw hole is used to install a pressure sensor; and / or

[0017] The lower end cover also has edge screw holes near the central screw hole. Bolts are installed in the edge screw holes, and the bolts have a central through hole for leading out the temperature measuring thermocouple wire and the ignition wire.

[0018] A further improvement of the present invention is that:

[0019] The temperature control mechanism also includes a temperature control box and a temperature-controlled thermocouple disposed on the outer wall of the housing. The temperature control box is connected to the temperature-controlled thermocouple and the ceramic heating jacket, respectively.

[0020] A further improvement of the present invention is that:

[0021] The thermocouples are provided in four locations, which are respectively located at the top, bottom, center hole, and inner wall of the propellant charge.

[0022] A further improvement of the present invention is that:

[0023] The pressure sensor is mounted on the central screw hole of the lower end cover.

[0024] A further improvement of the present invention is that:

[0025] There are four overpressure sensors, which are grouped in pairs. The two groups of overpressure sensors are positioned opposite each other on both sides of the incendiary bomb. The distance between the two overpressure sensors in each group and the center of the incendiary bomb is 0.5 to 1 m.

[0026] A further improvement of the present invention is that:

[0027] The pressure sensor is connected to the signal amplifier, and all four overpressure sensors are connected to the processing modulator. The signal amplifier and the processing modulator are respectively connected to the data acquisition unit.

[0028] A second aspect of the present invention provides an experimental method for quantitatively evaluating the intensity of a propellant slow-burn reaction. The method utilizes the aforementioned experimental apparatus to collect parameters during the slow-burn reaction process. The specific steps include:

[0029] The propellant sample was loaded into the propellant charge inside the incineration bomb, and the experimental device for quantitative evaluation of the slow incineration reaction intensity of the propellant was assembled.

[0030] Set the target temperature and heating rate on the temperature control box;

[0031] When the incendiary bomb is ignited, the internal pressure of the shell rises rapidly. When the pressure reaches the shell's fracture limit, the shell ruptures, and the shell fragments are dispersed at high speed under the action of the high-pressure gas products of the propellant. The internal pressure of the propellant after ignition is collected by pressure sensors, the air shock wave overpressure is collected by multiple overpressure sensors, the temperature change of the propellant grain during the heating process is collected by thermocouples, and the expansion velocity of the shell fragments is collected by the PDV velocity measurement mechanism.

[0032] Based on temperature changes, the expansion rate of shell fragments, internal pressure increase, and shock wave overpressure, the intensity of the slow combustion reaction of the propellant is analyzed, enabling a quantitative evaluation of the propellant reaction intensity.

[0033] A third aspect of the present invention provides the application of the above-described experimental apparatus or method for quantitatively evaluating the intensity of slow combustion reaction of propellants in the quantitative evaluation of propellant reaction intensity.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] This invention precisely controls the combustion environment temperature through a temperature control mechanism. When the combustion bomb ignites, the internal pressure of the shell rises rapidly. When the pressure reaches the shell's fracture limit, the shell ruptures, and shell fragments are dispersed at high speed under the action of high-pressure propellant gas products. The internal pressure increase process after the propellant charge ignites is collected by a pressure sensor located at the lower end of the combustion bomb. Multiple overpressure sensors located around the combustion bomb collect the air shock wave overpressure. The temperature change of the propellant grain during the heating process is collected by a temperature measuring mechanism. The expansion velocity of the shell fragments is collected by a PDV (Potentially Variable Voltage) velocity measuring mechanism. Then, based on the data such as temperature change, expansion velocity of shell fragments, internal pressure increase, and shock wave overpressure, the intensity of the slow combustion reaction of the propellant is analyzed, achieving a quantitative evaluation of the propellant reaction intensity.

[0036] This invention can provide a scientific basis for the safety assessment of propellants and the design and development of engine safety, and has broad application value and practicality. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of an experimental device for quantitatively evaluating the intensity of slow combustion reaction of propellants according to the present invention;

[0038] Figure 2 A diagram illustrating the process of heating an incendiary bomb;

[0039] Figure 3a The temperature change of the incendiary bomb when the groove on the side wall of the cylindrical section of the outer shell is 0 under the condition of spontaneous combustion;

[0040] Figure 3b The temperature change of the incendiary bomb when the groove on the side wall of the cylindrical section of the outer shell is 1 mm under spontaneous ignition conditions;

[0041] Figure 3c The temperature change of the incendiary bomb when the groove on the side wall of the cylindrical section of the outer shell is 2mm under spontaneous ignition conditions;

[0042] Figure 3d The temperature change of the incendiary bomb when the groove on the side wall of the cylindrical section of the outer shell is 3mm under spontaneous ignition conditions;

[0043] Figure 3e The temperature change of the incendiary bomb when the groove on the side wall of the cylindrical section of the outer shell is 4mm under spontaneous ignition conditions;

[0044] Figure 4a The internal pressure and shock wave overpressure curves of the cylindrical outer shell when the groove on the side wall of the outer shell is 0;

[0045] Figure 4b The internal pressure and shock wave overpressure curves of the cylindrical outer shell with a 1mm groove on the side wall are shown.

[0046] Figure 4c The internal pressure and shock wave overpressure curves of the cylindrical outer shell with a 2mm groove on the side wall are shown.

[0047] Figure 4d The internal pressure and shock wave overpressure curves of the cylindrical outer shell with a 3mm groove on the side wall are shown.

[0048] Figure 4e The internal pressure and shock wave overpressure curves of the cylindrical outer shell with a 4mm groove on the side wall are shown.

[0049] Figure 5 Velocity curves of casing fragments from B-4 and B-5 incendiary bombs;

[0050] Figure 6 The results of the charge reactivity calculations for five types of incendiary bombs are shown.

[0051] In the diagram, 1. Incendiary bomb, 101. Cylindrical outer shell, 102. Upper end cap, 103. Lower end cap, 104. Propellant charge, 105. Central hole, 106. Central screw hole, 107. Bolt, 2. Ceramic heating jacket, 3. Temperature control thermocouple, 4. Temperature measurement thermocouple, 5. Temperature acquisition device, 6. Pressure sensor, 7. Signal amplifier, 8. Data acquisition device, 9. Processing modulator, 10. Overpressure sensor, 11. DC regulated power supply, 12. PDV fiber optic velocity probe, 13. Laser generator, 14. Oscilloscope, 15. Temperature control box. Detailed Implementation

[0052] The present invention will now be described in further detail with reference to the accompanying drawings:

[0053] This invention provides an experimental apparatus for quantitatively evaluating the intensity of a propellant slow-burn reaction, such as... Figure 1 As shown, it includes:

[0054] The incendiary bomb 1 is mounted on a fixed support and includes a casing and a propellant charge disposed within the casing.

[0055] The temperature control mechanism includes a ceramic heating jacket 2 disposed outside the incendiary bomb 1;

[0056] The temperature measuring mechanism includes multiple thermocouples 4 installed inside the propellant charge, and the thermocouples 4 are connected to a temperature acquisition device 5 via thermocouple wires.

[0057] The pressure acquisition mechanism includes a pressure sensor 6 located at the lower end of the incendiary bomb 1 and multiple overpressure sensors 10 located around the incendiary bomb 1.

[0058] The PDV speed measurement mechanism includes a laser generator 13 and an oscilloscope 14 connected to the laser generator. A PDV fiber optic speed measurement probe 12 is connected to the laser generator 13 and is positioned close to the incendiary bomb 1.

[0059] During the experiment, the temperature of the combustion environment was precisely controlled by a temperature control mechanism. After the combustion bomb 1 ignited, the internal pressure of the shell rapidly increased. When the pressure reached the shell's fracture limit, the shell ruptured, and shell fragments were dispersed at high speed under the influence of the high-pressure gas products of the propellant. The internal pressure of the propellant after ignition was collected by a pressure sensor 6 located at the lower end of the combustion bomb 1. Multiple overpressure sensors 10 located around the combustion bomb 1 collected the air shock wave overpressure. The temperature change of the propellant grain during heating was collected by a temperature measuring mechanism. The expansion velocity of the shell fragments was collected by a PDV (Potentially Variable Voltage) velocity measuring mechanism. Based on the data such as temperature changes, the expansion velocity of the shell fragments, internal pressure, and shock wave overpressure, the slow combustion reaction intensity of the propellant was calculated, achieving a quantitative evaluation of the propellant reaction intensity. This invention can provide a scientific basis for propellant safety assessment and engine safety design and development, and has broad application value and practicality.

[0060] As a preferred embodiment of the present invention, such as Figure 2 As shown, the incendiary bomb 1 has a cylindrical structure, including a metal shell and a propellant charge 104. The metal shell includes a cylindrical outer shell 101, an upper end cap 102 disposed at the upper end of the cylindrical outer shell 101, and a lower end cap 103 disposed at the lower end of the cylindrical outer shell 101. The upper end cap 102 and the lower end cap 103 are connected by threads to the cylindrical outer shell 101. The propellant charge 104 is disposed inside the cylindrical outer shell 101, and the propellant charge 104 has a central hole 105 along the central axis. The outer diameter of the cylindrical section shell 101 is the same as the inner diameter of the cylindrical section shell 101. For example, in this embodiment of the invention, the inner diameter of the cylindrical section shell 101 is 50 mm and the outer diameter is 60 mm. It is made of D406A high-strength steel after vacuum heat treatment and has high strength. The outer diameter of the propellant charge 104 is 50 mm and the diameter of the central hole 105 is 10 mm. The charge is a three-component HTPB / AP / Al propellant, provided by the 46th Research Institute of the Sixth Academy of Aerospace Science and Industry. The upper and lower end caps are connected to the cylindrical section shell by threads with a thread length of 10 mm.

[0061] The lower end cap 103 has a central screw hole 106 corresponding to the position of the propellant loading center hole 105. The central screw hole 106 is used to install the pressure sensor 6. The lower end cap 103 also has an edge screw hole near the central screw hole 106. The edge screw hole is used to install a bolt 107. The bolt 107 has a central through hole for leading out the temperature measuring thermocouple wire and the ignition wire. The central screw hole 106 and the edge screw hole are sealed with sealant to ensure the system's airtightness.

[0062] The cylindrical outer shell 101 has grooves (not shown in the figure) on its side wall to change different shell constraints. The groove depth is preferably 0 to 4 mm. For example, in the embodiment of the present invention, the groove depth can be 0, 1 mm, 2 mm, 3 mm or 4 mm.

[0063] As a preferred embodiment of the present invention, such as Figure 1 As shown, the temperature control mechanism includes a ceramic heating jacket 2 disposed outside the incendiary bomb 1, a temperature-controlled thermocouple 3 disposed on the outer wall of the shell, and a temperature control box 15. The temperature control box 15 is connected to the temperature-controlled thermocouple 3 and the ceramic heating jacket 2 respectively. During the heating process, the temperature-controlled thermocouple 3 measures the ambient temperature around the propellant charge in real time and transmits the temperature data to the temperature control box 15 in real time. The temperature control box 15 adjusts the heating power of the ceramic heating jacket 2 according to the received temperature data, thereby accurately controlling the ambient temperature of the incendiary bomb and heating the propellant charge according to the preset heating curve.

[0064] In a preferred embodiment of the present invention, the temperature measuring mechanism includes multiple thermocouples 4 disposed within the propellant charge 104. The thermocouples 4 are connected to a temperature acquisition device 5 via thermocouple wires. Preferably, four thermocouples 4 are provided, which are respectively disposed at the top, bottom, central hole, and inner wall of the propellant charge 104. The thermocouple wires of the four thermocouples 4 pass through the central through hole of the bolt 107 connected to the lower end cover 103 and are connected to the temperature acquisition device 5 for real-time acquisition of the surface temperature and internal temperature of the propellant charge during the heating process.

[0065] Preferably, in this embodiment of the invention, both the temperature-controlling thermocouple 3 and the temperature-measuring thermocouple 4 are Kpsen K-type ultrafine thermocouples with a temperature measurement range of -50 to 300°C and a sensitivity of 0.1°C, which can achieve high-precision temperature measurement.

[0066] As a preferred embodiment of the present invention, the pressure acquisition mechanism includes a pressure sensor 6 disposed at the lower end of the incendiary bomb 1 and a plurality of overpressure sensors 10 disposed around the incendiary bomb 1.

[0067] Pressure sensor 6 is mounted on the central screw hole 106 of the lower end cover 103. Pressure sensor 6 is connected to signal amplifier 7 via a cable. One end of the cable is connected to pressure sensor 6 via an N5 connector, and the other end is connected to signal amplifier 7 via a BNC connector. Signal amplifier 7 is connected to data acquisition unit 8. All cables are low-noise coaxial shielded cables. Pressure sensor 6 is used to collect data on the internal pressure increase process after the propellant charge ignites.

[0068] Four overpressure sensors 10 are provided, arranged in pairs. The two pairs of overpressure sensors 10 are positioned opposite each other on either side of the incendiary bomb 1. The distance between the two overpressure sensors 10 in each pair and the center of the incendiary bomb 1 is 0.5–1 m. For example, in this embodiment, the distances between the two overpressure sensors 10 in each pair and the center of the incendiary bomb 1 are 0.5 m and 1 m, respectively. All four overpressure sensors are connected to a processing modulator 9, which is connected to a data acquisition unit 8. The four overpressure sensors 10 are used to collect the overpressure of the air shock wave.

[0069] In a preferred embodiment of the present invention, the PDV velocity measuring mechanism includes a laser generator 13 and an oscilloscope 14 connected to the laser generator 13. A PDV fiber optic velocity measuring probe 12 is connected to the laser generator 13 and is positioned close to the incendiary bomb 1. Preferably, the PDV fiber optic velocity measuring probe 12 is at the same height as the pre-drilled hole on the ceramic heating sleeve 2. Since the PDV fiber optic velocity measuring probe 12 continuously emits light towards the metal casing of the incendiary bomb, the time it takes to receive the light source signal changes when the casing breaks. Through a series of Fourier transform calculations, the expansion velocity of the casing fragments can be calculated. To ensure that the light emitted by the PDV fiber optic velocity measuring probe can hit the metal casing, the height of the PDV fiber optic velocity measuring probe needs to be consistent with the height of the pre-drilled hole on the ceramic heating sleeve.

[0070] During the experiment, the PDV fiber optic velocity probe 12 was mounted on a fixed bracket. The PDV fiber optic velocity probe 12 emitted a laser beam through a pre-drilled hole in the ceramic heating sleeve 2 towards the incendiary bomb. After the laser beam struck the side wall of the incendiary bomb, it was reflected back to the PDV fiber optic velocity probe. The reflected laser beam interfered with the emitted laser beam. Due to the Doppler effect, the frequency of the laser signal changed with the expansion velocity of the shell. Based on the change in the frequency of the laser signal after interference, the expansion velocity of the shell could be calculated, thus achieving non-contact measurement. Compared to traditional high-speed photogrammetry for measuring shell velocity, the PDV velocity measurement method has advantages such as high time resolution and high reliability. The laser generator 13 emitted a maximum laser power of 20.8 mW, and the oscilloscope sampling frequency was 40 GS·s. -1 The triggering method used in this experiment is internal triggering within the oscilloscope.

[0071] In this embodiment of the invention, the PDV velocimeter is a Photon Doppler Velocimeter (PDV), manufactured by Sichuan Wuke Optical Precision Machinery Co., Ltd., and can measure velocities ranging from 0.1 to 10000 m / s. -1 .

[0072] As a preferred embodiment of the present invention, the experimental apparatus for quantitatively evaluating the slow combustion intensity of propellant further includes an ignition mechanism, which comprises an igniter, an ignition wire, and an ignition charge. In this embodiment, the igniter uses a DC regulated power supply 11 (model UTP 1310+, 32V / 10A), the ignition charge is a B / KNO3 mixture, and the charge amount for each ignition is 100mg.

[0073] As a preferred embodiment of the present invention, the experimental device for quantitatively evaluating the intensity of the slow-burning reaction of propellants further includes a video monitoring mechanism (not shown in the figure). The video monitoring mechanism includes a high-speed camera and a surveillance camera, which are positioned at a safe distance (typically more than 50m for field tests). For example, in this embodiment, the experiment is conducted in an explosion crater. The high-speed camera and the surveillance camera are installed outside the crater, approximately 2m from the center, with tempered glass protecting them. The high-speed camera is used to observe the instant of explosion during the reaction. The surveillance camera is used to monitor for any accidents during the experiment, such as cable breaks or other unforeseen circumstances.

[0074] Among them, the high-speed camera (Qianyanlang X113) has a maximum shooting rate of 25000FPS and a minimum exposure time of 1μs. The surveillance camera model is Hikvision DS-IPC-B13HV3-LT, with 3 megapixels; the video recorder model is DS-7104N-F1.

[0075] This invention also provides an experimental method for quantitatively evaluating the intensity of a propellant slow-burn reaction. The method uses the aforementioned experimental apparatus for quantitatively evaluating the intensity of a propellant slow-burn reaction to collect relevant parameters during the propellant slow-burn reaction process. The specific steps include:

[0076] (1) Select different types of propellant samples according to experimental needs, prepare them according to standard specifications, and accurately measure the basic parameters such as mass and size of the propellant;

[0077] (2) Load the propellant sample into the propellant charge inside the incendiary bomb, according to... Figure 1 Assemble an experimental apparatus for quantitatively evaluating the intensity of slow combustion reaction of propellants;

[0078] (3) Set the target temperature and heating rate on the temperature control chamber, for example, set the experimental conditions to 1℃·min. -1 Heating at a rate of increase until the propellant reacts;

[0079] During the experiment, temperature-controlled thermocouples were used to measure the ambient temperature around the propellant charge in real time and transmit the temperature data to the temperature control box. The temperature control box adjusted the heating power of the ceramic heating jacket according to the received temperature data, thereby precisely controlling the combustion environment temperature. The temperature was adjusted in a timely manner according to the experimental needs to simulate different combustion environments.

[0080] (4) When the incendiary bomb is ignited, the internal pressure of the shell rises rapidly. When the pressure reaches the fracture limit of the shell, the shell ruptures and the shell fragments are scattered at high speed under the action of the high pressure gas products of the propellant. The internal pressure of the propellant after ignition is collected by pressure sensor, the air shock wave overpressure is collected by multiple overpressure sensors, the temperature change of the propellant column during the heating process is collected by thermocouple, and the expansion speed of the shell fragments is collected by PDV velocity measurement mechanism.

[0081] (5) Based on data such as temperature changes, expansion rate of shell fragments, internal pressure, and shock wave overpressure, analyze the intensity of the slow combustion reaction of the propellant to achieve a quantitative evaluation of the propellant reaction intensity.

[0082] After the first test is completed, repeat steps (1) to (5). For the pre-ignition test, when the temperature of the outer wall of the propellant charge reaches 120°C, perform the main control ignition.

[0083] Example:

[0084] Slow-burning combustion studies were conducted on the three-component HTPB propellant charge. The evolution characteristics of the slow-burning reaction under different shell constraints and different ignition temperatures were studied. A total of 7 experimental conditions were set, as shown in Table 1.

[0085] Table 1. Slow combustion test conditions of propellant under different shell constraints and different ignition temperatures.

[0086]

[0087] (I) Phenomena of slow-burning propellant test

[0088] (1) Reaction temperature and shell fragments

[0089] The temperature changes inside the charge during the combustion process were obtained by using thermocouples. Figures 3a to 3e Table 2 shows the temperature variations of incendiary bombs under different shell constraints under auto-ignition conditions. The slow-burning test results for incendiary bombs in different states are also presented. As can be seen from Table 2, for auto-ignition incendiary bombs, the outer wall temperature at the point of charge response is between 224 and 240 °C.

[0090] Table 2 Results of the slow-burning experiment with the incendiary bomb

[0091]

[0092] Depend on Figures 3a to 3eIt can be seen that during the heating phase, the propellant center temperature is the lowest, while the sidewall temperature is the highest. As the ignition temperature approaches, the temperature rise rate in the propellant center accelerates. This is because as the temperature increases, the propellant undergoes a thermal decomposition reaction, releasing heat. This heat cannot dissipate to the surrounding environment, leading to heat accumulation.

[0093] Observations of the recovered projectile debris after the experiment revealed that, for the B-1 incendiary bomb without grooves, the upper and lower end caps of the incendiary bomb body flew out after the incendiary response, the cylindrical outer shell was intact, and the fixed bracket was severely deformed, indicating that more work was done by flying out through the upper and lower end caps.

[0094] For the B-2 incendiary bomb, when the groove depth is 1mm, the upper and lower end caps of the bomb body fly out after the incendiary response, the cylindrical outer shell remains intact, and the fixing bracket is severely deformed. At this point, the reaction did not break off at the groove, indicating that the groove depth at this point has little impact on the reaction intensity.

[0095] For the B-3 incendiary bomb, when the groove depth is 2mm, the lower end cap of the bomb body remains largely intact after the incendiary response, the cylindrical outer shell cracks at the groove, the upper end cap cracks, and the fixing bracket deforms. At this depth, the groove depth can significantly reduce the intensity of the reaction.

[0096] For the B-4 incendiary bomb, with a groove depth of 3mm, the bomb body fractured at the threads of the upper and lower end caps after the combustion response, and the cylindrical outer shell broke into four pieces from the groove, with the fixing bracket deforming. For the B-5 incendiary bomb, with a groove depth of 4mm, the bomb body fractured at the threads of the upper and lower end caps after the combustion response, and the cylindrical outer shell broke into four pieces from the groove, with the fixing bracket deforming. A comparison of the B-4 and B-5 incendiary bombs shows that the cylindrical outer shell fractured at the groove in both cases, indicating that weakening the cylindrical outer shell through grooving can effectively reduce the intensity of the response.

[0097] (2) Internal pressure and shock wave overpressure

[0098] Figures 4a to 4e The figures show the internal pressure and shock wave overpressure curves obtained from the combustion test. For the B-1 combustion bomb, the propellant charge pressure rises rapidly upon ignition, reaching 348.31 MPa at approximately 0.8 ms. Subsequently, the shell breaks, the pressure sensor disconnects, and the average shock wave overpressure at 0.5 m and 1.0 m is 0.15 MPa and 0.05 MPa, respectively.

[0099] For the B-2 incendiary bomb, the propellant charge pressure rapidly increased upon ignition, reaching an internal pressure of 340.66 MPa at approximately 0.8 ms. Subsequently, the casing fractured. The average overpressure of the shock wave at 0.5 m and 1.0 m were 0.14 MPa and 0.05 MPa, respectively, comparable to the internal pressure and overpressure of the B-1 incendiary bomb. Comparison with the experimental debris reveals that the cylindrical casings of both incendiary bombs remained intact, breaking apart at both ends. This is because the 1 mm groove depth of the B-2 incendiary bomb was insufficient to effectively weaken the casing strength, resulting in comparable casing constraints in both experiments, thus leading to consistent experimental phenomena.

[0100] For the B-3 incendiary bomb, the propellant charge pressure rises rapidly upon ignition, reaching an internal pressure of 171.87 MPa at approximately 1.0 ms. Subsequently, the casing breaks apart, with average shock wave overpressures of 0.16 MPa and 0.07 MPa at 0.5 m and 1.0 m, respectively. While its internal pressure is lower than that of the B-1 incendiary bomb, the larger shock wave overpressure is due to the lower internal pressure and reactivity of the B-3. The weaker casing confinement and shallower groove depth result in less energy being consumed during casing breakup. Consequently, more of the energy released by the propellant upon ignition is converted into the kinetic and internal energy of the detonation products, leading to a higher shock wave overpressure.

[0101] For the B-4 incendiary bomb, the propellant charge pressure rises rapidly upon ignition, reaching 145.53 MPa internally at approximately 1.0 ms. Subsequently, the casing fractures, with average shock wave overpressures of 0.09 MPa and 0.04 MPa at 0.5 m and 1.0 m, respectively. Both its internal pressure and shock wave overpressure are lower than those of the B-3 incendiary bomb. As the groove depth of the casing increases, the casing constraint weakens, leading to a decrease in the reactivity and intensity of the propellant charge.

[0102] For the B-5 incendiary bomb, the propellant charge pressure rises rapidly upon ignition, reaching an internal pressure of 140.86 MPa at approximately 1.0 ms. Subsequently, the casing fractures, with average shock wave overpressures of 0.07 MPa and 0.03 MPa at 0.5 m and 1.0 m, respectively. Both the internal pressure and shock wave overpressure are lower than those of the B-4 incendiary bomb, indicating that further reduction of casing constraint can more effectively reduce the intensity of the propellant reaction.

[0103] (3) Velocity of shell fragments

[0104] Only two experiments (B-4 and B-5 incendiary bombs) yielded PDV signals. Observation of the experimental debris revealed that only the sidewalls of the B-4 and B-5 incendiary bomb casings fractured, consistent with experimental findings. The casing expansion rates of the two incendiary bombs were as follows: Figure 5As shown, after the B-4 incendiary bomb reacts, the instantaneous velocity of the fragmented casing reaches 18.02 m / s. Afterward, the fragment velocity decreases. The casing velocity is not accelerated again by the detonation products; instead, it decreases. This also reflects that when the casing breaks, the explosive reaction is complete, and there is no further energy output. This is because the rapid pressure drop caused by the rupture of the casing's constraint structure causes the combustion wave front structure of the explosive to become unstable and extinguish under high pressure. After the B-5 incendiary bomb reacts, the velocity of the fragmented casing reaches 13.10 m / s, after which the fragment velocity decreases.

[0105] Based on the casing velocity measured by PDV (Potentially Detected and Measured) tests, the reaction intensity of the B-4 incendiary bomb is greater than that of the B-5 incendiary bomb, which is consistent with the increase in internal pressure. PDV measurement results can serve as a basis for quantitative analysis of the slow-burn reaction intensity and play an important role in analyzing the reaction level and evolution process of munitions.

[0106] (II) Quantitative Evaluation and Analysis of Reaction Intensity

[0107] The U.S. military standard MIL-STD-2105E determines the safety response level of munitions primarily based on the consumption of energetic materials, the degree of casing fragmentation and fragmentation velocity, shock wave overpressure, witness plates, and other supporting evidence.

[0108] From the perspective of reaction grade judgment criteria, the reaction process of energetic materials is an important basis. The faster and more complete the reaction of energetic materials, the higher the reaction grade. In insensitive tests, the reaction process of energetic materials is generally qualitatively judged through experimental phenomena and results. However, by extracting the internal pressure changes of the charge casing, the reaction process and reactivity of energetic materials can be calculated. If the reaction time is very short and the reactivity is very high, the reaction grade is generally high.

[0109] The calculation of the reaction degree when the charge reacts under the action of an external excitation source is obtained by obtaining internal pressure, and quantitative evaluation parameters of reaction intensity such as shock wave overpressure and fragmentation velocity obtained by the experiment are used to establish the basis for quantitative evaluation of charge reaction level, as shown in Table 3.

[0110] Table 3. Basis for Quantitative Evaluation of Explosive Charge Safety Reaction Level

[0111]

[0112] (1) Energy calculation of shell fragments

[0113] Observing the recovered bomb fragments, the sidewall fragments of the B-4 and B-5 incendiary bombs weigh approximately 84g each. The kinetic energy of the fragments was calculated using the kinetic energy theorem based on the expansion velocity of the fragments measured by PDV (Power Distribution Vehicle).

[0114]

[0115] In the formula: E k ν is the kinetic energy of the shell fragment, J; m is the mass of the shell fragment, kg; v is the velocity of the shell, m / s.

[0116] Table 4 shows the fragment energies of the B-4 and B-5 incendiary bomb casings. It can be seen that the fragment energies of the B-4 and B-5 incendiary bomb casings are 12.01 J and 6.35 J, respectively, which are at the combustion reaction level.

[0117] Table 4 Energy Calculation Results of Shell Fragments

[0118]

[0119] (2) Calculation of the reaction rate of the charge

[0120] Since the hydroxyl-butadiene ternary propellant cannot be initiated, its maximum pressure during explosion cannot be determined through static explosion tests. Therefore, the maximum pressure achievable under constant-volume combustion conditions was calculated using E5 software, and the calculation results are shown in Table 5. Furthermore, the maximum internal pressure was obtained through a combustion-heating experiment, and the reactivity of the propellant was compared with theoretical calculations. Figure 6 As shown, the reactivity of the B-1 and B-2 incendiary bombs is 0.1428 and 0.1397 respectively, reaching the deflagration reaction level, while the remaining incendiary bombs have a reactivity of less than 0.1, which is the combustion reaction level.

[0121] Table 5 Pressure Calculation Results

[0122]

[0123] (3) Quantitative evaluation of reaction intensity

[0124] The parameters of the propellant charge reaction during slow baking were calculated through the baking and combustion experiment, as well as the shock wave overpressure and other experimental phenomena obtained from the experiment. The quantitative evaluation of the reaction intensity of the propellant charge is shown in Table 6.

[0125] Table 6 Quantitative Evaluation of Propellant Load Safety Reaction Level

[0126]

[0127]

[0128] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0129] In the description of this invention, unless otherwise stated, the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0130] The above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the technical solutions described in the specific embodiments of the present invention. Therefore, the foregoing description is only a preferred option and is not restrictive.

Claims

1. An experimental apparatus for quantitatively evaluating the intensity of a slow-burning reaction of a propellant, characterized in that, include: A heat-incendiary bomb, mounted on a fixed support, includes a casing and a propellant charge disposed within the casing; The temperature control mechanism includes a ceramic heating jacket disposed on the outside of the incendiary bomb; The temperature measuring mechanism includes multiple thermocouples disposed within the propellant charge, and the thermocouples are connected to a temperature acquisition device via thermocouple wires. The pressure acquisition mechanism includes a pressure sensor located at the lower end of the incendiary bomb and multiple overpressure sensors located around the incendiary bomb. The PDV velocity measurement mechanism includes a laser generator and an oscilloscope connected to the laser generator. A PDV fiber optic velocity measurement probe is connected to the laser generator and is positioned close to the incendiary bomb.

2. The apparatus according to claim 1, characterized in that, The housing includes a cylindrical outer shell, an upper end cover disposed at the upper end of the cylindrical outer shell, and a lower end cover disposed at the lower end of the cylindrical outer shell, and / or, The propellant charge is disposed inside the cylindrical section shell, and the propellant charge has a central hole along the central axis.

3. The apparatus according to claim 2, characterized in that, The lower end cap is provided with a central screw hole corresponding to the position of the propellant loading center hole; and / or, The lower end cap is also provided with edge screw holes near the center screw hole, and bolts are installed in the edge screw holes. The bolts have a center through hole.

4. The apparatus according to claim 1, characterized in that, The temperature control mechanism also includes a temperature control box and a temperature-controlled thermocouple disposed on the outer wall of the housing. The temperature control box is connected to the temperature-controlled thermocouple and the ceramic heating jacket, respectively.

5. The apparatus according to claim 1, characterized in that, The thermocouples are provided in four locations, which are respectively located at the top, bottom, center hole, and inner wall of the propellant charge.

6. The apparatus according to claim 3, characterized in that, The pressure sensor is mounted on the central screw hole of the lower end cover.

7. The apparatus according to claim 1, characterized in that, There are four overpressure sensors, which are grouped in pairs. The two groups of overpressure sensors are arranged opposite each other on both sides of the incendiary bomb. The distance between the two overpressure sensors in each group and the center of the incendiary bomb is 0.5 to 1m.

8. The apparatus according to claim 7, characterized in that, The pressure sensor is connected to the signal amplifier, and all four overpressure sensors are connected to the processing modulator. The signal amplifier and the processing modulator are respectively connected to the data acquisition unit.

9. A method for quantitatively evaluating the intensity of slow combustion reaction of propellants, characterized in that, The parameters of the propellant slow combustion reaction process are collected using the experimental apparatus for quantitative evaluation of propellant slow combustion reaction intensity as described in any one of claims 1-8. The specific method steps include: The propellant sample was loaded into the propellant charge inside the incineration bomb, and the experimental device for quantitative evaluation of the slow incineration reaction intensity of the propellant was assembled. Set the target temperature and heating rate on the temperature control box; When the incendiary bomb is ignited, the internal pressure of the shell rises rapidly. When the pressure reaches the shell's fracture limit, the shell ruptures, and the shell fragments are dispersed at high speed under the action of the high-pressure gas products of the propellant. The internal pressure of the propellant after ignition is collected by pressure sensors, the air shock wave overpressure is collected by multiple overpressure sensors, the temperature change of the propellant grain during the heating process is collected by thermocouples, and the expansion velocity of the shell fragments is collected by the PDV velocity measurement mechanism. Based on temperature changes, the expansion rate of shell fragments, internal pressure increase, and shock wave overpressure, the intensity of the slow combustion reaction of the propellant is analyzed, enabling a quantitative evaluation of the propellant reaction intensity.

10. The experimental apparatus for quantitative evaluation of propellant slow combustion reaction intensity as described in any one of claims 1-8 or the experimental method for quantitative evaluation of propellant slow combustion reaction intensity as described in claim 9, in the quantitative evaluation of propellant reaction intensity.

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