Device and method for evaluating the impact of nozzle structure on thermal safety of solid rocket motor

Abstract

The present invention discloses a device and method for evaluating the influence of nozzle structure on the thermal safety of solid motors, belonging to the field of solid motor testing technology. In the device of the present invention, the engine test piece includes a heating rod shell, a motor shell, a nozzle constraint and a propellant sample. The heating control system includes a heating rod, a heating control device, a heating rod shell thermocouple and a motor shell thermocouple. The laser schlieren system includes a continuous laser light source, an incident spherical mirror, an exit spherical mirror, a CCD high-speed camera, a slit and a filter. The pressure data acquisition system includes a chamber pressure sensor, a shock wave overpressure sensor, a multi-channel acquisition card and a computer. The present invention simulates the propellant thermal stimulation response process under the engine structural constraint state, and quantitatively characterizes the intensity of ignition and detonation of the propellant sample under thermal stimulation by measuring the shock wave overpressure and the chamber pressure in the engine shell. Combined with the response level criterion, a quantitative evaluation of the engine thermal safety response level is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid engine testing, and relates to a device and method for evaluating the thermal safety of propellant charge in a solid rocket engine under different nozzle structure constraint parameters. Background Art

[0002] Solid propellant is an energetic material widely used in aerospace propulsion and rocket and missile weapons. It generates thrust by burning to generate high-temperature gases that expand and accelerate through a nozzle. However, in complex battlefield environments, the high energy content of propellants also makes them dangerous under various unexpected stimuli. In environments such as rapid and slow cook-offs, the propellant in solid motors can cause combustion and explosion accidents. Therefore, the thermal safety of solid propellants has attracted great attention.

[0003] The response of solid propellants to thermal stimulation depends not only on their physical and chemical properties but also on the structural constraints of the solid rocket motor. Structural constraints of varying degrees and forms have a significant impact on the intensity of the propellant's thermal response. Currently, established propellant thermal safety assessment methods are Part 2: Rapid Cook-off Test and Part 3: Slow Cook-off Test, both in the National Military Standard GJB10015-2021, "Solid Propellant Low-Vulnerability Assessment Method." This method is suitable for low-vulnerability assessments of standard test motors, but the cost of whole-unit engine testing is high, and the available experimental data is limited. The experimental results are primarily used to assess the engine's safety response level. As a key component of a solid rocket motor, the nozzle structurally imposes an axial constraint on the propellant charge. To understand the influence of nozzle structural parameters on the propellant's thermal response, it is necessary to design and manufacture a constraint device similar to the overall engine structure to facilitate propellant thermal stimulation experiments under various nozzle constraint conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a device and method for evaluating the impact of nozzle structure on the thermal safety of solid rocket motors. By simulating the propellant's response to thermal stimulation under the motor's structural constraints and measuring the shock wave overpressure and the motor case's internal bore pressure to quantitatively characterize the intensity of the propellant sample's ignition and detonation under thermal stimulation, the impact of the nozzle structure on the thermal safety of the solid rocket motor and the response level are evaluated. This invention has the advantages of high assessment accuracy, reliable operation, high safety, and convenient operation.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] The present invention discloses a device for evaluating the influence of a nozzle structure on the thermal safety of a solid rocket engine, comprising an upper fixture, a heating rod housing, a heating rod, a heating rod housing thermocouple, a lower fixture, a slit, a filter, a propellant sample, an engine housing, a nozzle restraint, a chamber pressure sensor interface, an engine housing thermocouple, a chamber pressure sensor, a shock wave overpressure sensor, fastening bolts, a wire, a heating control device, a laser light source, an incident spherical mirror, an exit spherical mirror, a CCD high-speed camera, a multi-channel acquisition card, and a computer. The propellant sample is pre-loaded in the engine casing before the experiment; the engine casing is connected to the nozzle constraint and the heating rod casing by threads to form a structural constraint on the propellant sample; the heating rod casing is clamped by an upper clamp and a lower clamp and fixed by tightening the fastening bolts; one end of the heating rod is inserted into the heating rod casing, 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, and the heat is transferred to the propellant sample through the heating rod casing and the engine casing. The propellant continues to heat up, and the pressure in the engine structural constraint increases sharply. At a certain moment, ignition will occur and quickly grow into combustion or detonation; the chamber pressure sensor is connected to the chamber pressure sensor interface on the engine casing by threads to measure the process of increasing the pressure in the engine cavity accompanied by the propellant heating; the shock wave overpressure sensor is installed on the overpressure sensor bracket, and the overpressure sensor is used to monitor the pressure generated by the propellant explosion Shock wave overpressure; one end of the engine casing thermocouple is inserted into the engine casing, and the other end is connected to the heating control device to monitor the heating process of the engine casing; one end of the heating rod casing thermocouple is inserted into the heating rod casing, and the other end is connected to the heating control device to monitor the heating process of the heating rod casing; the multi-channel acquisition card is connected to the chamber pressure sensor, overpressure sensor, heating control device and computer to monitor and record the temperature and pressure changes during the experiment in real time; the laser light source, incident spherical mirror, exit spherical mirror, slit, filter and CCD high-speed camera constitute a schlieren system, which is used to shoot and record the ignition and detonation process of the propellant under the structural constraints of the engine, wherein the laser light source generates a stable and continuous light beam of a specific wavelength, which is reflected by a spherical mirror and passes through the area where the test piece is located. The light beam is then reflected by another spherical mirror and passes through the slit and filter and is received by the CCD high-speed camera. The CCD high-speed camera is connected to the computer to save the image data on the computer.

[0007] The engine test pieces include heater rod housing, engine housing, nozzle restraint and propellant samples.

[0008] The heating control system includes a heating rod, a heating control device, a heating rod housing thermocouple, and an engine housing thermocouple.

[0009] The laser schlieren system includes a continuous laser light source, an incident spherical mirror, an output spherical mirror, a CCD high-speed camera, a slit, and a filter.

[0010] The pressure data acquisition system includes a chamber pressure sensor, a shock wave overpressure sensor, a shock wave overpressure sensor bracket, a multi-channel data acquisition card, and a computer.

[0011] In order to meet the experimental requirements of changing the structural parameters of the nozzle, it is preferred that a chamber pressure sensor threaded interface is welded on the engine casing, a small hole is provided on the outer wall of the casing for inserting the engine casing thermocouple, and a threaded hole is provided on one side of the end for connecting with the heating rod casing; the adjustment of the structural parameters is achieved through nozzle restraints with different throat diameters and different outlet diameters; the engine casing and the nozzle restraint are connected by threads.

[0012] Preferably, the shell of the heating rod is in the shape of a stepped cylinder, and the outer wall of the protruding portion is processed with threads, and is connected to the engine housing through the threads.

[0013] To prevent overexposure of the CCD high-speed camera caused by the intense light from the intense combustion during propellant ignition and detonation, a slit and filter are preferably installed in front of the camera lens. The laser beam emitted by the laser source is first reflected by the incident spherical mirror. After the first reflection, the beam passes through the spatial area where the engine test article is located to capture the dynamic response within the engine test article's field of view. The beam is then reflected by the exit spherical mirror again. After the second reflection, the beam is filtered through the slit and filter to eliminate camera overexposure during the propellant ignition and detonation process.

[0014] To quantitatively assess the intensity of the thermal stimulus response, a chamber pressure sensor interface was welded to the engine housing. After being threaded into the sensor, the sensor measured the pressure increase inside the engine housing. A shock wave overpressure sensor was also positioned 30 cm from the test piece to measure the shock wave pressure generated by the ignition of the propellant sample.

[0015] In order to adjust the heating rate of the propellant, a thermocouple is used to monitor the temperature of the heated engine casing in real time. By controlling the power and on / off of the heating rod, the power is cut off when the temperature reaches the preset temperature of the current heating time, and the power is cut off when the temperature is lower than the preset temperature of the current heating time, thereby achieving control of the heating rate.

[0016] Preferably, test experiments to evaluate the impact of nozzle structure on the thermal safety of solid rocket engines are carried out at night or in a backlit open-air field to reduce the influence of natural light on the imaging effect of the laser light source schlieren system.

[0017] The present invention discloses a testing method for a testing device for evaluating the influence of nozzle structural parameters on the thermal safety of a solid rocket motor, comprising the following steps:

[0018] 1) Prepare cylindrical samples of a certain propellant composition;

[0019] 2) Place the cylindrical propellant sample into the engine housing. Use the engine housing fixture to connect the heating control device, heating rod, and nozzle restraint in sequence.

[0020] 3) Connect the heater housing thermocouple, engine housing thermocouple, chamber pressure sensor, and shock wave overpressure sensor, and debug the data acquisition system to ensure that the quality of the collected data meets the preset data quality requirements and that the acquisition system can trigger acquisition under the action of the pressure signal;

[0021] 4) Build and debug the laser schlieren system to ensure that the image acquisition area can cover the structurally constrained propellant sample and the surrounding space at least 20 cm away;

[0022] 5) Use heating control equipment to control the heating of the heating rod and monitor the temperature, pressure and image signals from the time of heating to the end of the propellant thermal response explosion process;

[0023] 6) Check the test site and observe the damage of the test piece. If there is any damage, collect the debris of the test piece around it, check whether there is any residual medicine inside the test piece, and collect the residual medicine splashed around it;

[0024] 7) The images recorded by the CCD high-speed camera and the chamber pressure curve and shock wave overpressure curve are used to determine the experimental response level.

[0025] The present invention discloses a method for evaluating the impact of nozzle structural parameters on the thermal safety of a solid motor, which is implemented based on the device for evaluating the impact of nozzle structural parameters on the thermal safety of a solid motor. The method for evaluating the impact of nozzle structural parameters on the thermal safety of a solid motor comprises the following steps:

[0026] Step S1: Read the temperature value of the engine casing during the cook-off process using a thermocouple, and extract the temperature time history curve recorded by the data acquisition card. At the cook-off response time, the reaction releases a large amount of heat, and the temperature curve should show a small jump at this time;

[0027] Step S2: The chamber pressure sensor collects the ignition pressure buildup process in the engine housing after the cook-off response. The data acquisition card receives and records the pressure time curve. At the cook-off response moment, the reaction produces a large amount of high-temperature combustion gas, and the pressure curve should show a sharp increase at this time.

[0028] Step S3: Determine the ignition timing of the engine test piece using the data obtained in steps S1 and S2;

[0029] Step S4: a high-speed camera records multiple consecutive schlieren images of the engine test piece at the ignition moment to observe the possible explosion process of the test piece;

[0030] Step S5: The shock wave overpressure sensor collects the shock wave overpressure generated by the explosion of the engine casing after the cook-off response, and the data acquisition card records the shock wave overpressure time history curve;

[0031] Step S6: Response level assessment is performed based on the collected shock wave overpressure time history curve and the response process recorded in the image. The response level assessment follows the following standards:

[0032] Detonation: The engine casing breaks into small fragments, generating a strong shock wave overpressure. The schlieren image shows a clear propagation process of the shock wave front. The small fragments refer to the engine casing fragments collected after the test with a diameter less than one-tenth of the engine casing diameter. The strong shock wave overpressure refers to the shock wave overpressure intensity exceeding the propellant detonation pressure.

[0033] Partial detonation: The engine casing is shattered, generating significant shock wave overpressure. The schlieren image shows a clear shock wave front propagation process. The significant shock wave overpressure refers to the shock wave overpressure intensity exceeding half of the propellant explosion pressure.

[0034] Explosion: The engine casing breaks into larger fragments, generating a shock wave overpressure whose intensity exceeds one-fifth of the propellant explosion pressure. The schlieren image shows a clear propagation process of the shock wave front. The larger fragments refer to fragments with a diameter greater than one-quarter of the engine casing diameter.

[0035] Detonation: The engine casing is obviously deformed and ruptured, forming a small number of larger fragments, which may generate shock wave overpressure. The schlieren image does not have an obvious shock wave front propagation process; the small number refers to less than 5 pieces, and the larger refers to fragments with a diameter greater than one-quarter of the engine casing diameter.

[0036] Combustion: The engine case cracks or the engine test piece falls out of the fixture, but no shock wave overpressure is generated, and the schlieren image does not show obvious shock wave front propagation process;

[0037] No combustion: The engine casing is intact, no shock wave overpressure is generated, and there is no obvious shock wave front propagation process in the schlieren image.

[0038] Beneficial effects:

[0039] 1. The present invention discloses a device and method for evaluating the influence of the nozzle structure on the thermal safety of a solid engine. The device includes more than a dozen main components, which cooperate closely with each other, are tightly connected, are easy to disassemble, and are easy to operate. The present invention adopts a modular design for the shell and the nozzle. The engine shell and the nozzle restraint are connected by threads, and the engine shell and the heating rod shell are connected by threads. The heating rod shell is clamped by a fixture and fixed by tightening the fastening bolts. In the preparation process of different working condition experiments, nozzle restraints and engine shells with different size parameters need to be replaced. The modular design of the present invention realizes the rapid disassembly and replacement of parts, and facilitates the removal of residual medicine or residues inside so that the next test can be carried out as soon as possible. At the same time, the modularization of engine components also avoids the processing difficulty and cost of the whole-machine molding of the engine test piece.

[0040] 2. The present invention discloses a device and method for evaluating the impact of nozzle structure on the thermal safety of solid rocket engines. By welding a chamber pressure sensor interface to the engine casing, pressure measurement within the casing constraint during engine ignition and detonation is added, which can quantitatively characterize the pressure threshold of the propellant sample breaking through the casing constraint under thermal stimulation.

[0041] 3. The present invention discloses a device and method for evaluating the impact of nozzle structure on the thermal safety of solid rocket engines. A schlieren system based on a laser light source of a specific wavelength can capture a clear image of the propellant detonation process, and the shock wave structure and propagation process reflected by the air density fluctuation are clearly visible; a slit and a filter are installed in front of the camera lens; the laser signal emitted by the laser light source is refracted twice by an incident spherical mirror and an exit spherical mirror before entering a CCD high-speed camera to capture the dynamic response in the field of view of the engine test piece, and is also filtered by the slit and the filter to eliminate camera overexposure during the propellant ignition and detonation process.

[0042] 4. The present invention discloses a device and method for evaluating the impact of nozzle structure on the thermal safety of solid rocket engines. The device and method are based on a schlieren system of a laser light source of a specific wavelength. Through a Z-shaped optical path design, high-precision and high-value instruments and equipment such as the laser light source, spherical mirror assembly and high-speed camera are kept at a safe distance from the engine test piece that may explode, thereby improving the safety of the experimental equipment.

[0043] 5. The present invention discloses a method for evaluating the impact of nozzle structure on the thermal safety of solid rocket engines. The evaluation method adopts a variety of data sources, and the temperature, chamber pressure, shock wave overpressure, and response process images are mutually verified. The response level criterion provides quantitative details, and a quantitative evaluation of the thermal safety of solid rocket engines is achieved based on the quantitative details. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1This is a schematic cross-sectional view (front view) of the main structure of the test device for evaluating the impact of the nozzle structure on the thermal safety of a solid rocket motor according to the present invention;

[0045] Figure 2 A schematic diagram of a heater fixing method of a test device for evaluating the effect of a nozzle structure on the thermal safety of a solid rocket motor according to the present invention (left view);

[0046] Figure 3 A schematic diagram of the macroscopic layout (top view) of the test device for evaluating the effect of the nozzle structure on the thermal safety of a solid rocket motor according to the present invention;

[0047] Figure 4 This is a flow chart of the method for evaluating the impact of the nozzle structure on the thermal safety of a solid rocket motor according to the present invention;

[0048] In the figure: 1-upper fixture, 2-heating rod housing, 3-heating rod, 4-heating rod housing thermocouple, 5-lower fixture, 6-slit, 7-filter, 8-propellant sample, 9-engine housing, 10-nozzle restraint, 11-chamber pressure sensor interface, 12-engine housing thermocouple, 13-chamber pressure sensor, 14-shock wave overpressure sensor, 15-fastening bolt, 16-wire, 17-heating control device, 18-laser light source, 19-incident spherical mirror, 20-exit spherical mirror, 21-CCD high-speed camera, 22-multi-channel acquisition card, 23-computer. DETAILED DESCRIPTION

[0049] See also Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 This embodiment discloses a device for evaluating the impact of nozzle structure on the thermal safety of a solid rocket motor. The invention will be further described below with reference to the accompanying drawings and examples.

[0050] This embodiment discloses a device for evaluating the effect of nozzle structure on the thermal safety of solid rocket motors, wherein the engine test piece is composed of a heating rod shell 2, a propellant sample 8, an engine shell 9, and a nozzle restraint 10. Figure 1 The heater housing 2 is a stepped cylindrical stainless steel structure with external threads on the raised portion of the step for connection with the internal threads of the engine housing. Two 5mm diameter, 3cm deep circular holes are provided in the cylindrical axial direction of the heater housing 2 for inserting the heater rod 3. A further 2mm diameter, 5cm deep circular hole is also provided in the axial direction for inserting the thermocouple 4 in the heater housing 2.

[0051] The engine housing 9 is a cylindrical stainless steel with a center hole of 10mm and a length of 30mm. An internal thread with a depth of 3cm is provided on one side of the opening for connection with the external thread of the heating rod housing 2. A boss is formed by cutting on the other side of the opening, and an external thread is provided on the outside of the boss for connection with the internal thread of the nozzle restraint 10. A groove is also provided on the side of the engine housing 9 near the heating rod housing 2 for inserting the engine housing thermocouple 12. A sensor interface 11 with a built-in internal thread is also welded on the side of the engine housing 9 near the nozzle restraint 10 for connection with the chamber pressure sensor 13. The chamber pressure sensor 13 transmits the piezoelectric signal formed by the pressure during the ignition and detonation of the engine test piece to the multi-channel data acquisition card 22 via a wire, and connects to the computer 23 for data acquisition and storage. As Figure 1 As shown, the chamber pressure sensor 13 is arranged in the cavity inside the engine housing 9. The purpose is to simulate the combustion chamber in the real engine structure and collect the pressure building process after the propellant ignition and detonation. At the same time, since the response degree of this experiment may be very intense, avoiding direct contact between the sensor and the propellant can reduce the probability of sensor damage.

[0052] The nozzle restraint 10 is a cylindrical stainless steel structure with a groove on one side. The inner wall of the groove is provided with internal threads that mate with the external threads of the engine housing 9 for connection. The center of the groove is a hole, the diameter of which gradually increases along the axial direction, forming the trumpet-like structure of the expansion section of a conventional solid rocket Laval nozzle. The engine structural parameter corresponding to the hole diameter here is the nozzle throat diameter.

[0053] The clamping diagram of the engine test piece is as follows: Figure 2 As shown, the fixture consists of two semicircular copper fixtures 1 and 5, secured together by bolts 15. 3mm flat grooves are symmetrically cut on either side of the heater rod housing 2 to facilitate clamping and limit axial displacement of the test specimen. A shock wave overpressure sensor 14 is positioned 30 cm from the engine test specimen. The sensor is held in place using a specialized fixture. During operation, the sensor's tip points toward the center of the test specimen where detonation may occur. The shock wave generated by the explosion is rectified by the tip and propagates to the sensitive element on the sensor's side surface. The resulting piezoelectric signal is transmitted via wires 16 to a multi-channel data acquisition card 22, which is then connected to a computer 23 for data acquisition and storage.

[0054] The schematic diagram of the experimental site layout of the device disclosed in this embodiment for evaluating the influence of the nozzle structure on the thermal safety of the solid rocket motor is as follows: Figure 3As shown, after the engine test piece is assembled and installed in the fixture, the heating rod 3 and the heating rod housing thermocouple 4 are inserted into the reserved interface of the heating rod housing 2, and the engine housing thermocouple 12 is inserted into the reserved interface of the engine housing 9. The heating rod and thermocouple are connected to the heating control device 17 using the wire 16. The heating control device 17 transmits the temperature data monitored by the thermocouple to the multi-channel data acquisition card 22 via the wire 16, and then connects to the computer 23 for data acquisition and storage.

[0055] The heating control device 17 uses a self-programmed control program to control the power size and start and stop of the heating rod 3. By comparing the temperature data monitored in real time by the thermocouple with the temperature corresponding to the preset heating rate, if the current temperature is greater than the expected temperature, the power supply to the heating rod 3 is stopped. If the current temperature is lower than the expected temperature, the power supply to the heating rod 3 is maintained.

[0056] Optical diagnostic arrangement such as Figure 3 As shown, the light beam emitted by the laser light source 18 will become parallel light after passing through the incident spherical mirror 19. After the parallel light passes through the spatial area where the engine test piece is located, it is reflected by the exit spherical mirror 20 and converged into a point light beam. The point light beam is adjusted by the slit 6 and the filter 7. The CCD high-speed camera 21 collects and processes the light signal to obtain a high-definition schlieren image on the computer 23.

[0057] The heating control device 17 controls the power of the heating rod 3. As the heating rod housing 2 heats up, the power is simultaneously transferred to the propellant sample 8. The propellant continues to heat up, expanding due to the heat, accompanied by chemical reactions among its energetic components. As heating continues, ignition may occur, rapidly escalating into combustion or detonation. The pressure within the engine housing 9 increases dramatically, causing radial damage. After the propellant sample 8 ignites, the combustion gases are discharged through the nozzle restraint 10. A laser schlieren system, consisting of a laser light source 18, an incident spherical mirror 19, an exit spherical mirror 20, a CCD high-speed camera 21, a slit 6, and a filter 7, can capture the propellant ignition and detonation process, effectively eliminating camera overexposure caused by the intense propellant combustion.

[0058] Example: Thermal Stimulus Response Test and Safety Assessment of a High-Energy Composite Solid Propellant under Structural Constraints

[0059] The present embodiment discloses a method for evaluating the effect of nozzle structure on the thermal safety of a solid engine, which includes: preparing a φ5mm×10mm cylindrical sample of a certain component propellant; placing the cylindrical propellant sample 8 into the engine casing 9, connecting the heating rod casing 2 to the engine casing 9, and connecting the nozzle restraint 10 to the engine casing 9; fixing the heating rod casing 2 with fixtures 4 and 5; connecting the heating rod 3, the heating rod casing thermocouple 4, and the engine casing thermocouple 12 to the heating control device 17, and connecting the heating control device 17 to the multi-channel data acquisition card 22; connecting the chamber pressure sensor 13 and the shock wave overpressure sensor 14 to the multi-channel data acquisition card 22; inserting the heating rod 3 into the heating rod casing 2 Debug data acquisition to ensure that the chamber pressure sensor 13 and the shock wave overpressure sensor 14 can trigger acquisition under the action of the pressure signal; build and debug the laser schlieren system to ensure that the schlieren system can collect continuous multiple frames of high-definition images through signal triggering; use the heating control device 17 to control the heating of the heating rod 3. During the heating process of the heating rod shell 2, the heating will be conducted to the propellant sample 8. The propellant continues to heat up and expands due to heat, accompanied by chemical reactions of the energetic components therein. As heating continues, ignition may occur and quickly grow into combustion or detonation. The pressure in the engine shell 9 increases sharply, causing the engine shell 9 to be damaged radially. After the propellant sample 8 ignites, the combustion gas is discharged through the nozzle restraint 10. The laser schlieren system composed of the laser light source 18, the incident spherical mirror 19, the exit spherical mirror 20, the CCD high-speed camera 21, the slit 6, and the filter 7 can capture the propellant ignition and detonation process and effectively eliminate the camera overexposure caused by the violent combustion of the propellant.

[0060] The evaluation process of the method for evaluating the impact of nozzle structure on the thermal safety of solid rocket motor disclosed in this embodiment is as follows: Figure 4 As shown, the starting time of the ignition and detonation response of the propellant sample is determined based on the temperature and pressure time history curve from heating to the end of the propellant thermal response and explosion process. The response level of the propellant under thermal stimulation load is determined based on the image captured by the CCD high-speed camera 21, combined with the peak pressure data collected by the chamber pressure sensor 13 and the shock wave overpressure sensor 14, to evaluate the intensity of the propellant's thermal stimulation response under the engine case-nozzle structural constraints. After the test is completed, the test site is cleaned and the damage of the test piece is observed. If there is any damage, the surrounding test piece debris is collected to check for residual propellant inside the test piece and collect any residual propellant that may have splashed out. The damaged engine case 9 and nozzle constraint 10 are then replaced, and the above test steps are repeated. After completing the test of nozzle constraint 10 with different structural parameters, the response level is determined according to the above-mentioned evaluation method, and the response results of different operating conditions are ranked by severity. This can evaluate the impact of the nozzle structure on the thermal safety of solid rocket engines and obtain the influence law of the nozzle structure on the thermal safety of solid rocket engines.

[0061] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for evaluating the effect of nozzle structure on the thermal safety of solid rocket motors, characterized by: The apparatus comprises an upper fixture, a heating rod housing, a heating rod, a heating rod housing thermocouple, a lower fixture, a slit, a filter, a propellant sample, an engine housing, a nozzle restraint, a chamber pressure sensor interface, an engine housing thermocouple, a chamber pressure sensor, a shock wave overpressure sensor, fastening bolts, a wire, a heating control device, a laser light source, an incident spherical mirror, an exit spherical mirror, a CCD high-speed camera, a multi-channel acquisition card, and a computer; the propellant sample is pre-loaded in the engine housing before the experiment; the engine housing is connected to the nozzle restraint and the heating rod housing by threaded connection to form a pair of The structural constraint of the propellant sample; the heating rod shell is clamped by the upper clamp and the lower clamp, and is fixed by tightening the fastening bolts; one end of the heating rod is inserted into the heating rod shell, 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, and the heat is transferred to the propellant sample through the heating rod shell and the engine shell. The propellant continues to heat up, and the pressure within the engine structural constraint increases sharply. At a certain moment, ignition will occur and quickly grow into combustion or detonation; the chamber pressure sensor is connected to the chamber pressure sensor on the engine shell through a thread. The interface is connected to measure the pressure increase process of the engine cavity accompanied by the propellant heating; the shock wave overpressure sensor is installed on the overpressure sensor bracket, and the overpressure sensor is used to monitor the shock wave overpressure generated by the propellant explosion; one end of the engine casing thermocouple is inserted into the engine casing and the other end is connected to the heating control device to monitor the temperature increase process of the engine casing; one end of the heater rod casing thermocouple is inserted into the heater rod casing and the other end is connected to the heating control device to monitor the temperature increase process of the heater rod casing; the multi-channel acquisition card is connected to the chamber pressure sensor, overpressure sensor, heating control device and computer to monitor and record the temperature and pressure changes during the experiment in real time; the laser light source, incident spherical mirror, exit spherical mirror, slit, filter and CCD high-speed camera constitute a schlieren system to record the ignition and detonation process of the propellant under the constraints of the engine structure, wherein the laser light source generates a stable and continuous light beam of a specific wavelength, which is reflected by a spherical mirror and passes through the area where the test piece is located. The light beam is then reflected by another spherical mirror and passes through the slit and filter before being received by the CCD high-speed camera. The CCD high-speed camera is connected to the computer to save the image data on the computer.

2. The device for evaluating the effect of nozzle structure on thermal safety of solid rocket motor according to claim 1, characterized in that: A threaded interface for the chamber pressure sensor is welded on the engine casing. A small hole is provided on the outer wall of the casing for inserting the engine casing thermocouple, and a threaded hole is provided on one side of the end for connecting with the heating rod casing. The adjustment of structural parameters is achieved through nozzle constraints with different throat diameters and different outlet diameters.

3. The device for evaluating the effect of nozzle structure on thermal safety of solid rocket motors according to claim 1, characterized in that: The shell of the heating rod is in the shape of a stepped cylinder, and the outer wall of the protruding part is processed with threads, which are connected to the engine shell through the threads.

4. The device for evaluating the effect of nozzle structure on thermal safety of solid rocket motor according to claim 1, characterized in that: The laser beam emitted by the laser light source is first reflected by the incident spherical mirror. After the first reflection, the beam passes through the spatial area where the engine test piece is located to capture the dynamic response in the field of view of the engine test piece. The light beam is then reflected by the output spherical mirror. After the second reflection, the light beam is filtered through a slit and a filter to eliminate the camera overexposure during the propellant ignition and detonation process.

5. The device for evaluating the effect of nozzle structure on thermal safety of solid rocket motor according to claim 1, characterized in that: The sensor is placed 30 mm away from the engine housing.

6. The device for evaluating the effect of nozzle structure on thermal safety of solid rocket motor according to claim 1, 2, 3, 4 or 5, characterized in that: The test method includes the following steps, 1) Prepare cylindrical samples of a certain propellant composition; 2) Place the cylindrical propellant sample into the engine casing, secure the casing with a fixture, and sequentially connect the heating control device, heating rod, and nozzle restraint. 3) Connect the thermocouple, chamber pressure sensor, and overpressure sensor, and debug the data acquisition system to ensure that the quality of the collected data meets the preset data quality requirements and that the acquisition system can trigger acquisition under the action of the pressure signal; 4) Build and debug the Schlieren system; 5) Use heating control equipment 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 explosion process; 6) Check the test site and observe the damage of the test piece. If there is any damage, collect the debris of the test piece around it, check whether there is any residual medicine inside the test piece, and collect the residual medicine splashed around it; 7) Record and save the images recorded by the CCD high-speed camera and the chamber pressure curve and shock wave overpressure curve.

7. A method for evaluating the effect of nozzle structure on the thermal safety of a solid rocket motor, implemented based on the apparatus of claim 1, 2, 3, 4, or 5, characterized in that: The following steps are included: Step S1: reading the temperature value of the engine casing during the cooking process by using a thermocouple, and extracting the temperature time history curve recorded by a data acquisition card; Step S2: The chamber pressure sensor collects the ignition pressure buildup process in the engine housing after the cook-off response, and the data acquisition card receives and records the pressure time history curve; Step S3: Determine the ignition timing of the engine test piece based on the data obtained in steps S1 and S2; Step S4: a high-speed camera records a continuous multi-frame schlieren image of the engine test piece at the ignition moment; Step S5: The shock wave overpressure sensor collects the shock wave overpressure generated by the explosion of the engine casing after the cook-off response, and the data acquisition card records the shock wave overpressure time history curve; Step S6: Response level assessment is performed based on the collected shock wave overpressure time history curve and the response process recorded in the image. The response level assessment follows the following standards: Detonation: The engine casing breaks into small fragments, generating a strong shock wave overpressure. The schlieren image shows a clear propagation process of the shock wave front. The small fragments refer to the engine casing fragments collected after the test with a diameter less than one-tenth of the engine casing diameter. The strong shock wave overpressure refers to the shock wave overpressure intensity exceeding the propellant detonation pressure. Partial detonation: The engine casing is shattered, generating significant shock wave overpressure. The schlieren image shows a clear shock wave front propagation process. The significant shock wave overpressure refers to the shock wave overpressure intensity exceeding half of the propellant explosion pressure. Explosion: The engine casing breaks into larger fragments, generating a shock wave overpressure whose intensity exceeds one-fifth of the propellant explosion pressure. The schlieren image shows a clear propagation process of the shock wave front. The larger fragments refer to fragments with a diameter greater than one-quarter of the engine casing diameter. Deflagration: The engine casing is significantly deformed and cracked, forming a small number of relatively large fragments. The Schlieren image does not show a clear shock wave front propagation process. The "small number" refers to fewer than 5 fragments, and the "large" refers to fragments with a diameter greater than one-quarter of the diameter of the engine casing. Combustion: The engine case cracks or the engine test piece falls out of the fixture, but no shock wave overpressure is generated, and the schlieren image does not show obvious shock wave front propagation process; No combustion: The engine casing is intact, no shock wave overpressure is generated, and there is no obvious shock wave front propagation process in the schlieren image.

Images