Solid propellant thermal weight loss and high initial temperature burning rate in-situ test system

Abstract

The invention discloses a solid propellant thermal weight loss and high initial temperature burning rate in-situ test system, and relates to the technical field of solid power. The heating temperature and duration of the solid propellant medicine strip are adjusted through the PID heating controller, the weight loss ratio of the medicine strip in the heating process is tested through the high-precision force sensor, and the surface temperature distribution of the medicine strip in the thermal response process is recorded through the high-speed thermal imager. And the laser is used for performing non-contact ignition on the heated high-initial-temperature explosive strip and performing in-situ measurement on the combustion speed of the high-initial-temperature explosive strip. The test system provided by the invention can test the weight loss ratio of the solid propellant under the programmed temperature rise thermal load, realizes the in-situ test of the combustion rate of the high-initial-temperature explosive strip of the solid propellant, and is of great significance to research on the correlation between the thermal decomposition characteristic and the combustion performance of the solid propellant, the thermal safety and the cook-off response. Compared with the prior art, the visual degree is higher, data capable of being measured in situ are diversified, the overall size is small, work is safe and reliable, and operation is easy and convenient.

Description

Technical Field

[0001] The invention relates to the field of solid power technology, and in particular to an in-situ testing system for the thermal weight loss rate of solid propellant under programmed temperature increase thermal load and the burning rate of high initial temperature thermal damage medicine strips. Background Art

[0002] Solid propellant is a solid mixture of energy and working fluid that solid rocket engines use to obtain thrust. It is an energetic material and belongs to a type of gunpowder. Solid propellants are always inevitably subjected to thermal stimulation due to heat sources, friction or impact heat during production, storage, transportation and use. In the history of solid propellant development, there have been a large number of propellant explosion accidents caused by thermal stimulation, which often cause casualties and damage to production lines. Research on the thermal safety of solid propellants is of great significance to improving the safety of aerospace engines and weapons and equipment. Therefore, since the advent of solid propellants, the thermal safety research of different types of propellants has always been an important topic.

[0003] Under the action of thermal load, the active components in solid propellants will undergo thermal decomposition, resulting in changes in the chemical composition of the remaining parts. The escape of the decomposed gases of the active components will cause thermal weight loss of the propellant. Component decomposition, thermal stress and other reasons will also cause thermal damage to the propellant (microstructure changes, such as the generation of pores and cracks). In general, thermal loads will cause changes in the chemical composition and microstructure of the propellant. These changes will further affect the ignition threshold and ignition response intensity of the propellant. Therefore, researchers have been committed to revealing the correlation between the thermal decomposition characteristics of propellants and combustion performance, as well as the thermal ignition response mechanism of propellants. In order to study the response law of solid propellants under high temperature load stimulation, researchers have designed various fast and slow baking equipment and gradually established standards. It was found that the baking response of the propellant is closely related to the burning rate characteristics after thermal damage, and the latter is affected by the propellant formula, shell constraints and thermal load history. Therefore, the key to studying the baking response mechanism of propellants is to establish the relationship between thermal decomposition characteristics and combustion performance. The existing test systems for studying the correlation between thermal decomposition and burning rate characteristics are all ex situ tests, that is, the heat treatment and burning rate tests are carried out in ex situ. The error introduced by humans due to the change in the initial temperature of the propellant is an inherent limitation of this test method. In addition, when measuring the temperature, using invasive temperature measurement methods such as inserting thermocouples into the propellant, and using contact ignition methods such as electric heating wire ignition, will cause large errors in the propellant burning rate test results.

[0004] In order to solve the above problems, the present invention proposes an in-situ testing system for thermal weight loss and high initial temperature burning rate of solid propellant. Summary of the invention

[0005] The purpose of the present invention is to provide a solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system to solve the problems raised in the background technology:

[0006] The existing test systems for studying the correlation between thermal decomposition and burning rate characteristics are all ex situ tests, that is, the heat treatment and burning rate tests are carried out ex situ. The error artificially introduced due to the change in the initial temperature of the propellant is an inherent limitation of this test method. In addition, the use of invasive temperature measurement methods such as inserting thermocouples into the propellant during temperature measurement and the use of contact ignition methods such as electric heating wire ignition during ignition will cause large errors in the propellant burning rate test results.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A solid propellant thermal weight loss and high initial temperature burning rate in-situ test system, characterized in that the test system includes a test mechanism, a heating controller, a charge amplifier, a data acquisition card, a high-speed infrared thermal imager and a computer;

[0009] The heating controller is matched with the test mechanism to control and record the heating temperature of the test mechanism;

[0010] The charge amplifier is used to amplify the signal generated by the testing mechanism;

[0011] The data acquisition card is used to collect the signal amplified by the charge amplifier;

[0012] The high-speed infrared thermal imager is used to capture and monitor image data during the testing process of the testing organization;

[0013] The computer is used to collect temperature data from the heating controller, signal data from the data acquisition card and image data from the high-speed infrared thermal imager;

[0014] The testing mechanism comprises a laser, a bracket, an end cover, a clamp, an infrared-transmitting germanium glass box, heat transfer oil, a thermocouple, a U-shaped heating tube, a high-temperature resistant quartz tube, a rubber ring, a force sensor and a medicine strip; the heat transfer oil is contained in the infrared-transmitting germanium glass box, the end cover is fixedly arranged on the top of the infrared-transmitting germanium glass box, the force sensor is fixedly installed at the center of the top surface of the end cover, the open end of the high-temperature resistant quartz tube is clamped and connected to the rubber ring, and the rubber ring is placed on the force sensor; the rubber ring adopts an annular structure design, the center of the rubber ring and the end cover are provided with through holes, the end of the high-temperature resistant quartz tube passes through the through hole and is placed in the heat transfer oil, and the medicine strip is arranged in the high-temperature resistant quartz tube; the U-shaped heating tube is connected to the end cover, and the thermocouple is integrated and installed in the U-shaped heating tube; the bracket is a truss structure, which is clamped and fixed on the end cover by a clamp, and the laser is fixedly connected to the top of the bracket.

[0015] Preferably, the heating controller is connected to both ends of the upper side of the U-shaped heating tube, and the heating of the U-shaped heating tube is controlled by the input signal of the thermocouple and the PID control module. The U-shaped design is conducive to uniform heating of the heat transfer oil by heat convection.

[0016] Preferably, the charge amplifier is used to amplify the signal collected by the force sensor. The force sensor is a high-precision high-temperature resistant sensor with a maximum operating temperature of ≥300°C. The measurement data of the force sensor can be used to calculate the in-situ measurement curve of the thermal weight loss of the medicine strip.

[0017] Preferably, the heat transfer oil is made of high temperature resistant modified silicone oil with a heat resistance temperature of ≥250°C. It is not easily oxidized when used for a long time in an open heating environment and does not self-sustain combustion under normal pressure.

[0018] Preferably, the infrared-transmitting germanium glass box is made of heat-resistant infrared-transmitting germanium glass with a heat-resistant temperature of ≥500° C., and the infrared-transmitting germanium glass material is more conducive to high-speed infrared thermal imager shooting.

[0019] Preferably, the heat-resistant quartz tube has a heat-resistant temperature of ≥1500°C. Actual measurements show that when solid propellant sticks burn in the tube, the burning rate is relatively fast and the local burning time of the quartz tube is short. Such a quartz tube will not break when used to hold the sticks for burning. The side surface of the high-temperature resistant quartz tube is evenly engraved with scale lines at intervals of 1 mm, which is convenient for use as a length ruler when measuring the burning rate using infrared images.

[0020] Preferably, the laser is a high-power CO2 laser, which is fixed to the bracket by a ball joint. The non-contact ignition method of the laser will not destroy the thermal damage microstructure of the high initial temperature medicine strip, and will not affect the accuracy of the burning rate test of the medicine strip. The laser is vertically installed just above the high-temperature resistant quartz tube to ignite the medicine strip. The distance between the bottom end of the laser and the top end of the high-temperature resistant quartz tube is greater than or equal to 50 cm to prevent the flame of the burning medicine strip and the high-temperature jet from burning the laser.

[0021] Preferably, the high-speed infrared thermal imager photographs the surface temperature distribution of the medicine strip during the heating process through the infrared-transmitting germanium glass box, records the infrared image at a frame rate of 1000fps for a long time, and measures the burning rate of the heat-damaged medicine strip under in-situ high initial temperature conditions. The high-speed infrared thermal imager can effectively capture the surface temperature distribution and combustion image of the medicine strip during the thermal response process.

[0022] A solid propellant thermal weight loss and high initial temperature burning rate in-situ testing method based on the system includes the following steps:

[0023] S1: Put the rubber ring on the open end of the high temperature resistant quartz tube, adjust the weight of the rubber ring to ensure that the high temperature resistant quartz tube will not float in the heat transfer oil when it is empty. The reading of the force sensor when it is empty is recorded as F0;

[0024] S2: Adjust the focus position of the laser to vertically align it with the center of the upper surface of the medicine strip;

[0025] S3: Start the high-speed infrared thermal imager and the heating controller's heating program to monitor the thermocouple temperature and the medicine strip surface temperature;

[0026] S4: The reading of the force sensor after the medicine strip is placed in the heat-resistant quartz tube is recorded as F1, and the reading of the force sensor during the heating process is recorded as F2. The thermal weight loss rate δ of the medicine strip is calculated by the following formula:

[0027]

[0028] S5: When the propellant reaches the expected high initial temperature thermal damage condition after programmed heating, the laser is started to ignite the propellant strip in situ;

[0029] S6: After the burning of the medicine strip is completed, the heating controller's temperature rising program is turned off, and the air cooling system is started to cool the heat transfer oil. After the heat transfer oil cools down, a new high temperature resistant quartz tube is replaced;

[0030] S7: Calculate the burning rate of the high initial temperature medicine strip using the infrared image of the burning medicine strip taken by the high-speed infrared thermal imager, and output the weight loss rate-temperature curve and the burning rate-initial temperature curve of the high initial temperature medicine strip during the heating process after data processing.

[0031] Compared with the prior art, the present invention provides a solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system, which has the following beneficial effects:

[0032] The present invention proposes an in-situ test system for thermal weight loss and high initial temperature burning rate of solid propellant, improves and optimizes the structure of existing solid propellant thermal decomposition and burning rate test equipment, and can realize in-situ testing of the burning rate of high initial temperature medicine strips of solid propellant, which is very meaningful for the correlation between the thermal decomposition characteristics and combustion performance of solid propellants, thermal safety and baking response research. The present invention adjusts the heating temperature and duration of solid propellant medicine strips through a PID heating controller, tests the weight loss rate of medicine strips during heating through a high-precision force sensor, records the surface temperature distribution of medicine strips during thermal response through a high-speed thermal imager, and non-contact ignites the high initial temperature medicine strips during heating through a laser and measures the burning rate of the high initial temperature medicine strips in situ. In summary, the present invention can realize the in-situ measurement of the burning rate of high initial temperature medicine strips, and the system has a high degree of visualization, and the response process can be photographed using a high-speed thermal imager. The test system can measure a variety of data in situ, the overall size is small, the operation is safe and reliable, and the operation is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a front cross-sectional view of a solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system mentioned in Example 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of the overall layout of a solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system mentioned in Example 1 of the present invention;

[0035] Description of the markings in the figure:

[0036] 1. Laser; 2. Bracket; 3. End cover; 4. Clamp; 5. Infrared-transmitting germanium glass box; 6. Heat transfer oil; 7. Thermocouple; 8. U-shaped heating tube; 9. High-temperature resistant quartz tube; 10. Rubber ring; 11. Force sensor; 12. Medicine strip; 13. Heating controller; 14. Charge amplifier; 15. Data acquisition card; 16. High-speed infrared thermal imager; 17. Computer. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0038] The present invention improves and optimizes the structure of the existing solid propellant thermal decomposition and burning rate testing equipment, and proposes a solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system. The heating temperature and duration of the solid propellant strip are adjusted by a PID heating controller, the weight loss rate of the strip during the heating process is tested by a high-precision force sensor, the surface temperature distribution of the strip during the thermal response process is recorded by a high-speed thermal imager, and the high initial temperature strip during heating is non-contact ignited by a laser and the burning rate of the high initial temperature strip is measured in-situ. The present invention can realize the in-situ measurement of the burning rate of the high initial temperature strip, and the system has a high degree of visualization, and the response process can be photographed by a high-speed thermal imager. The test system can measure a variety of data in-situ, the overall size is small, the operation is safe and reliable, and the operation is simple. Specifically include the following contents.

[0039] Embodiment 1:

[0040] See also Figure 1-2 The present invention proposes an in-situ test system for thermal weight loss and high initial temperature burning rate of solid propellant, comprising a laser 1, a bracket 2, an end cover 3, a fixture 4, an infrared-transmitting germanium glass box 5, a heat-conducting oil 6, a thermocouple 7, a U-shaped heating tube 8, a high-temperature resistant quartz tube 9, a rubber ring 10, a force sensor 11, a medicine strip 12, a heating controller 13, a charge amplifier 14, a data acquisition card 15, a high-speed infrared thermal imager 16, and a computer 17; wherein the laser 1 is used for igniting the medicine strip 12, is fixed to the upper crossbeam of the bracket 2 through a ball joint, and is suspended directly above the high-temperature resistant quartz tube 9 and the medicine strip 12;

[0041] The bracket 2 is a truss structure, which is clamped and fixed on the end cover 3 by a clamp 4 and is used to clamp the laser 1;

[0042] The end cover 3 is the upper cover of the infrared-transmitting germanium glass box 5, and a through hole is opened on its surface for the U-shaped heating tube 8 and the high-temperature resistant quartz tube 9 to pass through;

[0043] The infrared-transmitting germanium glass box 5 contains heat-conducting oil 6, and the infrared-transmitting germanium glass material is conducive to the high-speed infrared thermal imager 16 to shoot;

[0044] The thermocouple 7 is fixedly connected to the U-shaped heating tube 8 and immersed in the heat transfer oil 6 to measure the oil temperature near the medicine strip 12;

[0045] The U-shaped design of the U-shaped heating tube 8 is conducive to uniformly heating the heat transfer oil 6 by heat convection; the open end of the high temperature resistant quartz tube 9 is clamped by a rubber ring 10 and placed on the force sensor 11, and the closed end is vertically immersed in the heat transfer oil 6, and the medicine strip 12 is placed in the high temperature resistant quartz tube 9;

[0046] The force sensor 11 is a ring-shaped structure, the through hole in the middle passes through the high-temperature resistant quartz tube 9, and is placed on the end cover 3 as a whole; the heating controller 13 is connected to the upper ends of the U-shaped heating tube 8, and controls the heating of the U-shaped heating tube 8 through the input signal of the thermocouple 7 and the PID control module;

[0047] The signal of the force sensor 11 is amplified by the charge amplifier 14 and then collected by the data acquisition card 15;

[0048] The high-speed infrared thermal imager 16 is set up in front of the infrared-transmitting germanium glass box 5 to capture the surface temperature distribution and combustion image of the thermal response process of the medicine strip 12;

[0049] The computer 17 is responsible for collecting the temperature measurement data from the heating controller 13 , the force data from the data acquisition card 15 , and the infrared image from the high-speed infrared thermal imager 16 .

[0050] During the test, firstly, the rubber ring is put on the open end of the high temperature resistant quartz tube, and the weight of the rubber ring is adjusted to ensure that the high temperature resistant quartz tube will not float in the heat transfer oil when it is empty. The force sensor reading when it is empty is recorded as F0; then the focusing position of the laser is adjusted to vertically align with the center of the upper surface of the medicine strip, and the high-speed infrared thermal imager and the heating program of the heating controller are started to monitor the thermocouple temperature and the surface temperature of the medicine strip; the force sensor reading after the medicine strip is placed in the heat resistant quartz tube is recorded as F1, and the force sensor reading during the heating process is recorded as F2, and then the thermal weight loss rate δ of the medicine strip 12 is calculated based on F1 and F2, and the calculation formula is: When the propellant reaches the expected high initial temperature thermal damage condition through programmed heating, the laser is started to ignite the medicine strip in situ; after the medicine strip is burned, the heating program of the heating controller is turned off, and the air cooling system is started to cool the heat transfer oil. After the heat transfer oil is cooled, a new high-temperature resistant quartz tube is replaced; the infrared image of the burning medicine strip taken by a high-speed infrared thermal imager is used to calculate the burning rate of the high initial temperature medicine strip, and after data processing, the weight loss rate-temperature curve and the burning rate-initial temperature curve of the high initial temperature medicine strip during the heating process are output.

[0051] In summary, the solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system proposed in the present invention can carry out in-situ testing of the thermal decomposition characteristics of the propellant and the burning rate of the damaged medicine strip. In terms of the testing of the thermal decomposition and thermal damage characteristics of the propellant, the thermal weight loss rate and the heat conduction temperature field can be monitored. In terms of the combustion performance, the burning rate characteristics and the combustion temperature field of the high initial temperature medicine strip can be tested. The heating temperature and duration of the solid propellant medicine strip are adjusted by a PID heating controller, the weight loss rate of the medicine strip during the heating process is tested by a high-precision force sensor, the surface temperature distribution of the medicine strip during the thermal response process is recorded by a high-speed thermal imager, and the high initial temperature medicine strip during heating is non-contact ignited by a laser and the burning rate of the high initial temperature medicine strip is measured in-situ.

[0052] 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 inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system, characterized in that: The test system comprises a test mechanism, a heating controller (13), a charge amplifier (14), a data acquisition card (15), a high-speed infrared thermal imager (16) and a computer (17); The heating controller (13) is matched with the test mechanism and is used to control and record the heating temperature of the test mechanism; The charge amplifier (14) is used to amplify the signal generated by the testing mechanism; The data acquisition card (15) is used to collect the signal amplified by the charge amplifier (14); The high-speed infrared thermal imager (16) is used to capture and monitor image data during the testing process of the testing mechanism; The computer (17) is used to collect temperature data from the heating controller (13), signal data from the data acquisition card (15) and image data from the high-speed infrared thermal imager (16); The testing mechanism comprises a laser (1), a bracket (2), an end cover (3), a fixture (4), an infrared-transmitting germanium glass box (5), heat-conducting oil (6), a thermocouple (7), a U-shaped heating tube (8), a high-temperature-resistant quartz tube (9), a rubber ring (10), a force sensor (11) and a medicine strip (12); the heat-conducting oil (6) is contained in the infrared-transmitting germanium glass box (5), the end cover (3) is fixedly arranged on the top of the infrared-transmitting germanium glass box (5), the force sensor (11) is fixedly installed at the center of the top surface of the end cover (3), the open end of the high-temperature-resistant quartz tube (9) is clamped and connected to the rubber ring (10), and the rubber ring (10) is placed on the force sensor (11); the rubber ring (10) is designed with a ring structure, and a through hole is provided at the center of the rubber ring (10) and on the end cover (3); the end of the high-temperature resistant quartz tube (9) passes through the through hole and is placed in the heat transfer oil (6), and the medicine strip (12) is arranged inside the high-temperature resistant quartz tube (9); the U-shaped heating tube (8) is connected to the end cover (3), and the thermocouple (7) is integrated and installed inside the U-shaped heating tube (8); the bracket (2) is a truss structure, which is clamped and fixed on the end cover (3) by a clamp (4), and the laser (1) is fixedly connected to the top of the bracket (2).

2. A solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system according to claim 1, characterized in that: The heating controller (13) is connected to both ends of the upper side of the U-shaped heating tube (8), and controls the heating of the U-shaped heating tube (8) through the input signal of the thermocouple (7) and the PID control module.

3. A solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system according to claim 1, characterized in that: The charge amplifier (14) is used to amplify the signal collected by the force sensor (14); the force sensor (14) is a high-precision high-temperature resistant sensor with a maximum operating temperature of ≥300°C.

4. A solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system according to claim 1, characterized in that: The heat transfer oil (6) is selected from high temperature resistant modified silicone oil, and the heat resistant temperature is ≥250°C.

5. The solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system according to claim 1, characterized in that: The infrared-transmitting germanium glass box (5) is made of heat-resistant infrared-transmitting germanium glass with a heat-resistant temperature of ≥500°C.

6. A solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system according to claim 1, characterized in that: The heat-resistant temperature of the high-temperature resistant quartz tube (9) is ≥1500°C, and the side surface of the high-temperature resistant quartz tube (9) is evenly engraved with scale lines at intervals of 1 mm.

7. A solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system according to claim 1, characterized in that: The laser (1) is a high-power CO2 laser, which is fixed to the bracket (2) through a ball joint; the laser (1) is vertically installed just above the high-temperature resistant quartz tube (9) for igniting the medicine strip (12), and the distance between the bottom end of the laser (1) and the top end of the high-temperature resistant quartz tube (9) is greater than or equal to 50 cm.

8. The solid propellant thermal weight loss and high initial temperature burning rate in-situ testing system according to claim 1, characterized in that: The high-speed infrared thermal imager (16) photographs the surface temperature distribution of the medicine strip (12) during the heating process through the infrared-transmitting germanium glass box (5), records the infrared image for a long time at a frame rate of 1000 fps, and measures the burning rate of the heat-damaged medicine strip under in-situ high initial temperature conditions.

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