A device and method for testing the transient adiabatic pressure of a pyrotechnic

Abstract

The present application relates to a kind of pyrotechnics transient adiabatic pressure testing device and method.Utilize pressure measuring bomb to gather the output energy of pyrotechnics, form initial pressure;Utilize piston rod and hydraulic medium to realize the transient adiabatic of pressure sensor and pyrotechnics pressure transmission;Select suitable pressure sensor to obtain pressure signal, the inherent frequency of pressure sensor meets the frequency characteristic demand of test system;According to pressure test precision needs and O ring friction force calculation formula, select O ring;Design reasonable exhaust hole, exclude the air component in pressure medium, so that pressure medium meets Pascal theorem.The present application has good repeatability, eliminates the adverse effects of lumen effect on pyrotechnics pressure test results, can isolate the transient high-temperature combustion gas generated when pyrotechnics works, effectively avoid the influence of temperature on test results.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of pyrotechnics pressure testing and relates to a pyrotechnics transient adiabatic pressure testing device and method. BACKGROUND

[0002] Pyrotechnics pressure testing belongs to the test content specified in GJB736-16A-2019 "Pyrotechnics Test Methods Part 16: Ignition Pressure-Time Curve Determination", mainly examines the ignition performance of pyrotechnics, and is one of the important test items before the delivery of pyrotechnics.

[0003] As shown in the accompanying Figure 1 According to the test method specified in GJB736-16A, the strain pressure sensor 11 is usually selected to obtain the pressure signal in the pyrotechnics pressure test. The strain pressure sensor 11 is made according to the Wheatstone bridge principle, and four resistance strain gauges are pasted on the sensing surface of the sensor to form an equal-arm bridge. After the sensing surface is pressed, the resistance value of the strain gauge changes, and the corresponding changed voltage is output, which is amplified and output to the acquisition system after conditioning.

[0004] The strain pressure sensor 11 used in the current pyrotechnics pressure test has poor temperature resistance, generally about 60℃. During the test, gun oil needs to be applied on the sensing surface of the pressure sensor 11 to reduce the influence of instantaneous high-temperature combustion gas on the test results through the gun oil barrier. This test method has significant effect in low-frequency test process, but still has the following problems:

[0005] (1) It is impossible to avoid the direct contact of the sensor sensing surface with the high-temperature combustion gas output by the pyrotechnics. When the test frequency is increased, the temperature change of the sensor is obvious, which easily causes distortion of the test signal.

[0006] (2) For constant-volume pressure measurement, the pressure sensor 11 is connected with the pressure measuring bomb 13 through the adapter mouth 12. The gas inlet channel of the adapter mouth 12 and the threaded hole between the pressure sensor 11 are prone to produce a pipe cavity effect, which affects the accuracy of the test results. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the application provides a pyrotechnics transient adiabatic pressure testing device and method, which mainly solves the problems of pipe cavity effect and high-temperature combustion gas affecting the accuracy of test results during pyrotechnics pressure testing.

[0008] The technical solution of the application is:

[0009] A pyrotechnics transient adiabatic pressure testing device, comprising a piston rod, an O-ring, a hydraulic medium, a joint, a pressure sensor, and a sealing gasket.

[0010] The joint is internally provided with a first columnar cavity and a second columnar cavity which are mutually through, the inner diameter of the first columnar cavity is smaller than that of the second columnar cavity; the piston rod is radially provided with two grooves in which O-rings are arranged, one end of the piston rod is inserted into the first columnar cavity of the joint and the piston rod can move along the first columnar cavity; a compression sealing pad is arranged at the bottom of the second columnar cavity of the joint, and the pressure sensor is screw-mounted in the second columnar cavity; the pressure sensor is connected with the data acquisition system through a signal conditioning amplifier.

[0011] Preferably, the joint is provided with an exhaust hole, the bottom surface of the exhaust hole is flush with the upper surface of the hydraulic medium;

[0012] Before the pressure sensor is installed, the cavity of the joint should be filled with the hydraulic medium, and air should be discharged from the exhaust hole of the joint until the air is completely discharged, and then the pressure sensor is screw-installed.

[0013] Preferably, during the test, the joint is screw-installed on the pressure bomb, after being installed in place, the first columnar cavity of the joint is in communication with the interface of the pressure bomb, and one end of the piston rod is in the interface of the pressure bomb.

[0014] The method for testing the transient adiabatic pressure of the explosive based on the device comprises the following steps:

[0015] The device for testing the transient adiabatic pressure of the explosive is built;

[0016] The device for testing the transient adiabatic pressure is calibrated by using the piston pressure gauge;

[0017] The explosive and the device for testing the transient adiabatic pressure are installed on the pressure bomb;

[0018] The explosive is subjected to a rated energy, the explosive generates high-temperature gas after working, the high-temperature gas establishes pressure in the pressure bomb, the pressure pushes the piston rod, the piston rod extrudes the hydraulic medium, the hydraulic medium transmits the pressure received by the piston rod to the sensing surface of the pressure sensor, the pressure sensor outputs a strain voltage, the strain voltage is input into the data acquisition system after being conditioned and amplified, and the acquisition of the transient pressure signal of the explosive is realized.

[0019] Preferably, the method for building the device for testing the transient adiabatic pressure of the explosive is as follows:

[0020] The inherent frequency of the pressure sensor and the data acquisition system is determined;

[0021] The interface size of the pressure bomb is determined;

[0022] According to the interface size of the pressure bomb and the sensor, the structure of the joint is determined, including the size of the first columnar cavity which is connected with the pressure sensor and the size of the external thread which is installed with the pressure bomb;

[0023] The outer size of the piston rod is determined;

[0024] Estimate the fundamental frequency f of the piston rod based on the simple harmonic motion spring model;

[0025] Determine the hydraulic fluid level;

[0026] Determine the location of the vent hole of the connector based on the liquid level;

[0027] The first and second cylindrical cavities of the connector are designed according to the piston rod size and the liquid level of the hydraulic medium.

[0028] Select the O-ring material specifications based on the required pressure test accuracy and the O-ring friction calculation formula;

[0029] Construct a transient adiabatic pressure testing device for pyrotechnics according to the structure and parameters determined above.

[0030] Preferably, the fundamental frequency f of the piston rod estimated by the simple harmonic spring model satisfies:

[0031]

[0032] Where E0 is the elastic modulus of the piston rod, ρ is the density of the piston rod material, and l is the length of the piston rod.

[0033] Preferably, the fundamental frequency f should be more than three times that of the data acquisition system.

[0034] Preferably, the hydraulic fluid level is determined as follows:

[0035] The hydraulic medium encapsulated in the joint cavity is equivalent to a semi-infinite closed-end pipe, and the fundamental frequency of this semi-infinite closed-end pipe is... Where E v ρ′ is the bulk modulus of the hydraulic medium, ρ′ is the density of the medium, and l′ is the liquid level. Ensure that the fundamental frequency f′ is more than 3 times that of the data acquisition system.

[0036] Preferably, the method for selecting the O-ring material specifications is as follows:

[0037] According to the formula for calculating static friction The O-ring size on the piston rod is determined by the accuracy range of the pressure test. In the formula, f″, d, and D are the friction coefficient between the O-ring and the groove, the cross-sectional diameter of the O-ring, and the outer diameter of the O-ring, respectively. E and u are the elastic modulus and Poisson's coefficient of the O-ring material, respectively. P is the external pressure borne by the hydraulic medium, and e is the O-ring compression ratio.

[0038] Preferably, when calibrating the transient adiabatic pressure test device using the piston pressure gauge, the number of calibration points is not less than four, and the relationship between the output voltage and the input pressure is obtained as P=aU+b, wherein U is the voltage value output by the pressure sensor, and a and b are constant coefficients calculated by the least square method.

[0039] Advantages of the present application:

[0040] (1) The prior art cannot avoid the impact of high-temperature and high-pressure gas and detonation fragments on the sensor sensitive surface. The present application isolates the high-temperature and high-pressure gas and detonation fragments from the sensor sensitive surface through the piston and hydraulic medium, reduces the influence of temperature on the sensor, avoids the damage of detonation fragments to the sensor, and improves the reliability of the test and the service life of the sensor.

[0041] (2) The prior art test technology usually switches the pilot pressure pipe to eliminate the influence of temperature on the sensor. The cavity of the pilot pressure pipe can cause pipe cavity effect, causing distortion of high-frequency pressure signals and affecting the accuracy of test results. The present application improves the natural frequency of the pipeline by transmitting force through the piston and hydraulic medium, and improves the accuracy of test results. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a test schematic under the prior art conditions;

[0043] Figure 2 is a sectional view of the pressure test device;

[0044] Figure 3 is a test schematic;

[0045] Figure 4 is a sectional view of the joint;

[0046] Figure 5 is a top view of the joint;

[0047] Figure 6 is a front view of the piston rod;

[0048] Figure 7 is a front view of the sealing gasket;

[0049] Figure 8 is a sectional view of the pressure cell;

[0050] Figure 9 is a half sectional view of the pressure cell. DETAILED DESCRIPTION

[0051] The present application will be described in further detail below with reference to the accompanying drawings:

[0052] The application can isolate the influence of high-temperature gas on the sensor, and is beneficial to improve the service life of the sensor. The application has wide application prospects in the fields of solid rocket pressure test, ignition cartridge pressure test and small cavity pressure test of various initiating explosive devices. In addition, the pressure test device designed by the application fundamentally eliminates the adverse effects of the cavity effect.

[0053] As shown in the accompanying drawings, Figures 2-9 A pressure test device for initiating explosive device is designed by the application, which comprises a pressure sensor 11, a joint 21, a sealing gasket 23, an O-ring 24, a hydraulic medium 25 and a piston rod 26.

[0054] The joint 21 is internally provided with a first columnar cavity and a second columnar cavity which are mutually through, and the inner diameter of the first columnar cavity is smaller than that of the second columnar cavity. The piston rod 26 is radially provided with two grooves, and the grooves are internally provided with the O-ring 24. One end of the piston rod 26 is inserted into the first columnar cavity of the joint 21, and the piston rod 26 can move along the first columnar cavity. The sealing gasket 23 is arranged at the bottom of the second columnar cavity of the joint 21, and the pressure sensor 11 is threadedly arranged in the second columnar cavity. The pressure sensor 11 is connected with a data acquisition system through a signal conditioning amplifier.

[0055] The joint 21 is provided with an exhaust hole 22, and the bottom surface of the exhaust hole is flush with the liquid level of the hydraulic medium.

[0056] Before the pressure sensor 11 is installed, the cavity of the joint 21 should be filled with the hydraulic medium 25, and the air should be completely discharged from the exhaust hole 22 of the joint 21, and then the pressure sensor 11 is installed through the thread.

[0057] During the test, the joint 21 is threadedly arranged on the pressure bomb 13. After being installed in place, the first columnar cavity of the joint 21 is in communication with the pressure bomb 13 and the pressure bomb interface. One end of the piston rod 26 is arranged in the pressure bomb interface.

[0058] Test principle: a rated energy is applied to the initiating explosive device 14. After the initiating explosive device works, the main charge burns in the pressure bomb 13 to generate a detonation wave and high-temperature gas. The detonation wave and high-temperature gas push the piston rod 26, and the piston rod 26 extrudes the hydraulic medium 25. According to the Pascal theorem, the hydraulic medium 25 transmits the pressure of the piston rod 26 to the sensing surface of the pressure sensor 11. The pressure sensor 11 outputs a strain voltage, which is input into the data acquisition system after signal conditioning and amplification, so as to realize the acquisition of the transient pressure signal of the initiating explosive device 14 and achieve the test purpose.

[0059] The specific steps of the application are as follows:

[0060] (1) Design of pressure bomb: design the pressure bomb according to the volume requirement of the pressure bomb and the installation size of the pyrotechnics, and leave a threaded mounting hole for the pressure measuring device on the pressure bomb body, and the mounting hole avoids facing the output end of the pyrotechnics.

[0061] (2) Design of pressure testing device: the piston rod is sleeved with an O-ring and loaded into the pressure measuring connector, then the hydraulic medium is filled, and the pressure sensor is screwed, to make the pressure testing device.

[0062] The preparation steps of the pressure testing device are as follows:

[0063] (1) Determine the inherent frequency of the pressure sensor and the data acquisition system.

[0064] (2) Determine the interface size of the pressure bomb.

[0065] (3) According to the interface size of the pressure bomb and the pressure sensor, determine the structural characteristics of the connector, that is, the threaded hole size for installing the pressure sensor and the external thread size for installing the pressure bomb.

[0066] (4) Determine the outer size of the piston rod. According to the simple harmonic vibration spring model, estimate the fundamental frequency of the piston rod Wherein E0 is the elastic modulus of the piston rod, p is the density of the piston rod material, and l is the length of the rod. Ensure that the fundamental frequency is more than 3 times the acquisition system.

[0067] (5) Determine the liquid level of the hydraulic medium. The hydraulic medium packaged in the sensor cavity is equivalent to a semi-infinite closed-end pipeline, and the fundamental frequency f' is calculated according to the quarter sound speed formula. That is Wherein E v is the bulk modulus of the hydraulic medium, p' is the medium density, and l' is the liquid level. Ensure that the fundamental frequency f' is more than 3 times the data acquisition system.

[0068] (6) Design the connector cavity according to the piston rod and the liquid level of the hydraulic medium.

[0069] (7) According to the liquid level of the hydraulic medium, set the position of the exhaust hole so that the bottom surface of the exhaust hole is flush with the liquid level.

[0070] (8) Select the material specification of the O-ring, and determine the groove size of the O-ring on the piston rod according to the empirical calculation formula of the static friction force And the accuracy range of the pressure test, wherein f'', d, and D are the friction coefficient of the O-ring and the groove, the cross-sectional diameter of the O-ring, and the outer diameter of the O-ring, respectively, E and u are the elastic modulus and Poisson's ratio of the O-ring material, respectively, P is the external pressure borne by the hydraulic medium, and e is the compression amount of the O-ring, which can be calculated by the calculation formula e = [d0-(h+c)] / d0, wherein d0 is the cross-sectional diameter of the O-ring in the free state, h is the groove depth, and c is the hole shaft gap.

[0071] (9) Fit the O-ring 24 into the groove of the piston rod 26 and insert the connector 21. Place the sealing gasket 23 on the stepped hole of the connector 21, pour in the hydraulic medium 25, and screw on the pressure sensor 11 until the sealing gasket 23 is pressed tightly, ensuring that the air is completely discharged from the exhaust hole 22 of the connector 21.

[0072] The use of the pressure measuring device of the present invention will be described in detail below with specific examples:

[0073] (1) Connect the pressure sensor 11 to the data acquisition system through a signal conditioning amplifier.

[0074] (2) Use a piston-type pressure gauge to calibrate the pressure testing device, with no less than four calibration points. Obtain the relationship between output voltage and input pressure as P = aU + b, where P is the pressure value, U is the voltage value output by the sensor, and a and b are constant coefficients calculated by the least squares method during calibration.

[0075] (3) Install the pressure testing device 31 onto the pressure testing bullet 13.

[0076] (4) Install the pyrotechnic device 14 onto the pressure tester 13.

[0077] (5) Apply the specified ignition energy to the pyrotechnic 14. After the pyrotechnic 14 is working, it generates high-temperature gas. The high-temperature gas builds up pressure in the pressure measuring bullet 13. The pressure pushes the piston rod 26 and acts on the pressure sensor 11 through the hydraulic medium 25. The pressure sensor 11 generates a strain signal, which is conditioned and amplified before being output to the acquisition system.

[0078] (6) The output pressure of the pyrotechnic device is obtained according to the relationship between pressure and voltage, P = aU + b.

[0079] This invention utilizes a pressure-sensing projectile to concentrate the output energy of a pyrotechnic device, forming an initial pressure. A piston rod and hydraulic medium transmit the output pressure while simultaneously achieving transient insulation. The piston rod structure, the type of hydraulic medium, and the liquid level are calculated theoretically. A suitable pressure sensor is selected to acquire the pressure signal, and the sensor's natural frequency meets the frequency characteristics requirements of the testing system. An O-ring is selected based on the required pressure testing accuracy and the O-ring friction calculation formula. A vent is installed according to the liquid level to remove air from the pressure medium, ensuring the pressure medium conforms to Pascal's law.

[0080] The application can adjust the installation size of the pressure sensor according to the requirement, avoids the influence of the threaded hole of the fixed pressure sensor on the volume change of the pressure bomb, and creates conditions for the test of the small cavity of the initiating explosive. The application has good repeat characteristics, eliminates the step of smearing gun oil on the sensing surface of the pressure sensor, can avoid the influence of repeated disassembly and assembly of the pressure sensor on the test efficiency and quality, and is beneficial to improving the service life of the pressure sensor. The application eliminates the adverse influence of the cavity effect on the test result of the initiating explosive. The application can isolate the transient high-temperature combustion gas generated by the work of the initiating explosive, and effectively avoids the influence of the temperature on the test result.

[0081] The contents not described in detail in the specification of the application belong to the known technology of the person skilled in the art.

Claims

1. A method for testing the transient adiabatic pressure of an initiating explosive device based on a testing device for the transient adiabatic pressure of an initiating explosive device, characterized in that, The pyrotechnics transient adiabatic pressure testing device comprises a piston rod (26), an O-ring (24), a hydraulic medium (25), a joint (21), a pressure sensor (11), and a sealing gasket (23); The joint (21) is internally provided with a first columnar cavity and a second columnar cavity which are mutually through, and the inner diameter of the first columnar cavity is smaller than that of the second columnar cavity; the piston rod (26) is radially provided with two grooves, and the grooves are internally provided with the O-ring (24); one end of the piston rod (26) is inserted into the first columnar cavity of the joint (21), and the piston rod (26) can move along the first columnar cavity; the sealing gasket (23) is arranged at the bottom of the second columnar cavity of the joint (21), and the pressure sensor (11) is threadedly arranged in the second columnar cavity; the pressure sensor (11) is connected with a data acquisition system through a signal conditioning amplifier; The pyrotechnics transient adiabatic pressure testing method comprises the following steps: The pyrotechnics transient adiabatic pressure testing device is built; The piston pressure gauge is used to calibrate the transient adiabatic pressure testing device; The pyrotechnics and the transient adiabatic pressure testing device are arranged on the pressure measuring bomb; The pyrotechnics is applied with a rated energy, and high-temperature combustion gas is generated after the pyrotechnics works; the high-temperature combustion gas establishes pressure in the pressure measuring bomb, the pressure drives the piston rod, the piston rod extrudes the hydraulic medium, the hydraulic medium transmits the pressure received by the piston rod to the sensing surface of the pressure sensor, the pressure sensor outputs a strain voltage, and after signal conditioning and amplification, the strain voltage is input into the data acquisition system, so that the pyrotechnics transient pressure signal is acquired; The method for building the pyrotechnics transient adiabatic pressure testing device is as follows: The inherent frequency of the pressure sensor and the data acquisition system is determined; The interface size of the pressure measuring bomb is determined; According to the interface size of the pressure measuring bomb and the sensor, the structure of the joint is determined, including the size of the first columnar cavity which is connected with the pressure sensor and the size of the external thread which is connected with the pressure measuring bomb; The outer size of the piston rod is determined; The fundamental frequency f of the piston rod is estimated according to the simple harmonic vibration spring model; The liquid level of the hydraulic medium is determined; According to the liquid level, the position of the exhaust hole of the joint is determined; According to the size of the piston rod and the liquid level of the hydraulic medium, the first columnar cavity and the second columnar cavity of the joint are designed; According to the pressure testing accuracy requirement and the O-ring friction force calculation formula, the material specification of the O-ring is selected; The pyrotechnics transient adiabatic pressure testing device is built according to the above determined structure and parameters.

2. The method according to claim 1, wherein the method is characterized by: The joint (21) is provided with an exhaust hole (22), and the bottom surface of the exhaust hole is flush with the upper surface of the hydraulic medium; Before the pressure sensor (11) is installed, the joint (21) should be filled with the hydraulic medium (25) to ensure that the air is completely discharged from the exhaust hole (22) of the joint (21), and then the pressure sensor (11) is installed through the thread.

3. The method according to claim 2, wherein the method is characterized by: During the test, the joint (21) is threadedly installed on the pressure measuring bomb (13), and after being installed in place, the first columnar cavity of the joint (21) is connected with the interface of the pressure measuring bomb (13); one end of the piston rod (26) is arranged in the interface of the pressure measuring bomb.

4. The method according to claim 1, wherein the method is characterized by: The simple harmonic vibration spring model estimates the fundamental frequency f of the piston rod, and the following formula is satisfied: wherein E0 is the elastic modulus of the piston rod, ρ is the density of the piston rod material, and l is the length of the piston rod.

5. The method according to claim 4, wherein the method is characterized by, The fundamental frequency f should be greater than 3 times of the data acquisition system.

6. The method according to claim 1, wherein the method is characterized by: The liquid level of the hydraulic medium is determined in the following manner: The hydraulic medium encapsulated in the joint cavity is equivalent to a semi-infinite closed-end pipe, the fundamental frequency of which is where E v is the bulk modulus of the hydraulic medium, p' is the medium density, and l' is the liquid height, ensuring that the fundamental frequency f' is more than 3 times greater than the data acquisition system.

7. The method according to claim 1, wherein the method is characterized by: The O-ring material specification is selected in the following manner: According to the static friction force calculation formula and pressure test accuracy range to determine the size of the piston rod O-ring, where f", d, D are the friction coefficient of the O-ring and the groove, the O-ring cross-sectional diameter, and the O-ring outer diameter, E and u are the elastic modulus and Poisson's ratio of the O-ring material, P is the external pressure borne by the hydraulic medium, and e is the O-ring compression rate.

8. The method according to claim 1, wherein the method is characterized by: When calibrating the transient adiabatic pressure testing device using a piston pressure gauge, the number of calibration points is not less than four, and the relationship between the output voltage and the input pressure P=aU+b is obtained, wherein U is the voltage value output by the pressure sensor, and a and b are constant coefficients calculated by the least square method.

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