A discrete self-ignition experimental method for explosive powder based on a rapid compressor

Abstract

The present invention discloses a discrete self-ignition experimental method for explosive powder based on a rapid compressor, comprising the following steps: 1) determining the components, proportions and total pressure p of the ambient gas in the combustion chamber of the rapid compressor, and calculating the respective partial pressures; 2) loading solid explosive powder into the injection pipe of the injection system of the visual combustion chamber end cover of the rapid compressor; 3) locking the compression piston at the compression bottom dead center position under the action of high oil pressure; 4) evacuating the combustion chamber environment, and sequentially filling the combustion chamber with argon gas of p1 and nitrogen gas of p2 through the gas distribution system; 5) rapidly compressing from the bottom dead center to the top dead center under the drive of compressed air in a high-pressure gas tank; 6) the solid explosive powder forms discrete powder in the combustion chamber through the powder injection holes on the injector under the action of high-pressure jet, and recording the visual image and dynamic pressure change of the compression process by using a high-speed camera and a pressure sensor; and 7) analyzing the self-ignition behavior of the solid explosive powder in the discrete state, and establishing a combustion model.

Description

Technical Field

[0001] The present invention belongs to the field of explosive ignition / detonation and combustion chemistry, and specifically relates to a discretized self-ignition experimental method for explosive powder based on a rapid compressor, which is used to study the ignition and combustion behavior of explosives under quasi-zero-dimensional thermal stimulation, establish explosive ignition models and combustion reaction kinetic mechanisms, etc. Background Art

[0002] Explosives are substances capable of intense combustion / explosion in a very short period of time. Due to their inherent oxygen content, when stimulated by external stimuli, they undergo redox reactions, releasing large amounts of energy and causing damage and destruction to surrounding objects. With the modernization of battlefields, new weapons and ammunition are rapidly being introduced. From the perspective of explosive synthesis and application, high energy density and insensitivity are currently the focus of research both domestically and internationally. However, there is a trade-off between high energy density and insensitivity: the higher the energy density, the lower the insensitivity, making them more susceptible to accidental ignition or even explosion when exposed to external stimuli, especially thermal stimulation. The response characteristics and reaction mechanisms of explosives under thermal stimulation directly impact their practical safety applications and the development of new insensitive explosives. Therefore, studying the spontaneous ignition behavior of explosives under thermal stimulation and exploring their combustion reaction mechanisms is crucial.

[0003] The thermal stimulation environment of explosives can be categorized as slow, fast, or ultrafast, depending on their heating rate. Currently, international research focuses on explosive response testing under slow heating rates (<10K / h) and fast heating rates (<20K / s), namely, slow and fast cook-off tests. Slow cook-off tests are primarily used to simulate the temperature, time, and response of explosives during storage, transportation, and combat readiness, when the ambient temperature slowly increases. Fast cook-off tests simulate the temperature, time, and response of explosives during accidental fires during storage, transportation, and combat readiness. On the battlefield, weapons and ammunition are subject to ultrafast thermal stimulation (heating rates exceeding 1000K / s) when encountering situations such as the detonation of adjacent explosives or enemy missile attacks. However, relatively little research has been conducted on the response and self-ignition behavior of explosives under ultrafast heating rates. Existing thermal stimulation tests for explosives struggle to accurately describe the thermodynamic state (temperature and pressure), and numerous external interference factors hinder the development of models for explosive combustion reactions.

[0004] In summary, establishing an ultrafast thermal stimulation loading method ensures that the thermodynamic state of the environment in which the explosive is located can be clearly described; eliminating external interference factors can achieve contactless self-ignition test observation, and thus create a quasi-zero-dimensional system; it has important theoretical and application value for explaining the self-ignition phenomenon and establishing a combustion reaction model. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the self-ignition test of explosive powder discretization based on a rapid compressor. This method uses the characteristics of the rapid compressor device to generate a high temperature environment in a very short time to achieve a 2×10 4 K / s heating rate; the explosive powder is dispersed in a gas atmosphere with a clear thermodynamic state to form contactless self-ignition, achieving a quasi-zero-dimensional system; the experimental explosive particle size is small and the sample dosage is safe.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A method for discrete self-ignition of explosive powder based on a rapid compressor comprises the following steps:

[0008] 1) Determine the composition, proportion and total pressure p of the ambient gas in the rapid compressor combustion chamber, that is, determine the volume fractions A1 and A2 of the diluent argon and nitrogen; use the partial pressure formula pi = p × A i ,i=1,2, calculate the respective partial pressures;

[0009] 2) loading solid explosive powder into the injection pipe of the injection system of the end cover of the rapid compressor visual combustion chamber, and sealing the visual combustion chamber with the end cover;

[0010] 3) Hydraulic oil is pumped into the hydraulic section through a hydraulic pump, so that the compression piston is locked at the compression bottom dead center position under the action of high oil pressure;

[0011] 4) Use a vacuum pump to evacuate the combustion chamber through the pipeline, and fill the combustion chamber with argon gas (P1) and nitrogen gas (P2) in sequence through the gas distribution system;

[0012] 5) The pressure relief valve of the high-pressure oil pump is opened through the control system, and the oil pressure in the hydraulic section drops rapidly. Driven by the compressed air in the high-pressure gas tank, the compression piston-connecting rod-hydraulic piston-connecting rod-driving piston structure is rapidly compressed from the bottom dead center to the top dead center;

[0013] 6) When the control system opens the pressure relief valve, it synchronously controls the injection system, pressure acquisition system, and high-speed camera system signals. The solid explosive powder in the injection system is injected into the combustion chamber through the powder injection holes on the injector under the action of high-pressure jets to form discrete powder. The high-speed camera and pressure sensor are used to record the visual image of the compression process and the dynamic pressure changes.

[0014] 7) Using the known pressure data, the corresponding temperature is calculated using the ideal gas isentropic state equation. Based on the pressure curve and visualization image, the self-ignition behavior of solid explosive powder in the discretized state is analyzed, and a combustion model is established.

[0015] A further improvement of the present invention is that the solid explosive powder is 1-30 mg of micron / nano-sized cyclotrimethylene trinitramine RDX, cyclotetramethylene tetranitramine HMX or hexanitrohexaazaisopentazane CL-20 simple substance and a mixed explosive.

[0016] A further improvement of the present invention is that the combustion chamber end cover injection system includes a high-pressure gas source, a pressure reducing valve, a pressure gauge, an injector, a carrier ferrule with a nozzle, and an injector control drive module, wherein the high-pressure gas source is connected to the pressure reducing valve and the pressure gauge, the injector and the carrier ferrule with the nozzle are matched with a threaded seal, a signal is sent through the injector control drive module, and the high-pressure gas source cooperates with the pressure reducing valve and the pressure gauge to input high-pressure gas of a set pressure into the injector to spray out the powder.

[0017] A further improvement of the present invention is that the control system is programmed based on LabVIEW software and can synchronously control the pressure relief valve, the ejector, the pressure acquisition system and the high-speed camera.

[0018] A further improvement of the present invention is that the discretization of explosive powder refers to the discrete powder dispersed in the combustion chamber formed after the explosive passes through the high-pressure ejector.

[0019] A further improvement of the present invention is that the self-ignition behavior of explosive powder refers to the ignition process of discrete powder in a quasi-zero-dimensional ultrafast thermal stimulation environment, and is recorded by a pressure acquisition system and a high-speed camera.

[0020] A further improvement of the present invention is that the heating rate in the quasi-zero-dimensional ultrafast thermal stimulation environment is 2×10 4 K / s.

[0021] A further improvement of the present invention is that the ideal gas isentropic state equation is Where T c is the compression top dead center temperature, T0 is the initial temperature, γ is the specific heat ratio, p c is the compression top dead center pressure, and p0 is the initial pressure.

[0022] The present invention has at least the following beneficial technical effects:

[0023] 1) The explosives used in the present invention are RDX, HMX, CL-20, etc. The sample synthesis technology is mature and simple and easy to obtain; the sample particle size is micron / nanoscale, the dosage is only 1-30 mg, the combustion explosion pressure and temperature are low, and the experimental risk is low.

[0024] 2) This invention focuses on fully discretizing the explosive using a powder injection system, achieving a contactless, quasi-zero-dimensional ignition process. The explosive powder is sprayed into a visual combustion chamber, where the sample reacts in a rapid thermal stimulation environment. The system is clean and interference-free, eliminating excess heat dissipation. This facilitates the precise description and construction of thermodynamic states and combustion reaction kinetic models during the powder's self-ignition process.

[0025] 3) The method of the present invention synchronously controls the pressure relief valve, the ejector, the pressure acquisition system, and the high-speed camera through the graphical modular LabVIEW. The rising edge of the starting signal voltage is triggered, with a high synchronization rate and no delay, and can realize multi-channel real-time recording and storage.

[0026] 4) The present invention uses argon and nitrogen as the combustion chamber environment gases, and no oxidants such as oxygen participate in the self-ignition process of the explosive powder, which is conducive to directly judging the oxygen content, oxidation reaction ability and reaction degree of the explosive itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of the rapid compressor used in the present invention.

[0028] Figure 2 Schematic diagram of the visualized combustion chamber structure with the powder injection system used in the present invention.

[0029] Figure 3 (a) and (b) are the discretization results of explosive powder in Example 1 of the present invention at 4MPa and 863K.

[0030] Figure 4 This is the pressure curve of explosive powder at 4 MPa and 863 K obtained by using a pressure sensor in Example 1 of the present invention.

[0031] Description of reference numerals:

[0032] 1-Fuel tank, 2-Compression section, 3-Light source, 4-Lens, 5-Injection system, 6-High-speed camera, 7-Control and acquisition system, 8-Hydraulic section, 9-Piston connecting rod system, 10-Drive section, 11-Metal hose, 12-High-pressure gas tank, 13-Air compressor, 14-Manual butterfly valve, 15-Electric butterfly valve, 16-Quartz glass, 17-Combustion chamber end cover, 18-Window end cover, 19-Compression piston. DETAILED DESCRIPTION

[0033] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present disclosure and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] like Figure 1-2 As shown, a schematic diagram of the structure of a fast compressor and a combustion chamber with a powder injection system used in the present invention includes a fuel tank 1, a compression section 2, a light source 3, a lens 4, an injection system 5, a high-speed camera 6, a control and acquisition system 7, a hydraulic section 8, a piston connecting rod system 9, a drive section 10, a metal hose 11, a high-pressure gas tank 12, an air compressor 13, a manual butterfly valve 14, an electric butterfly valve 15, a quartz glass 16, a combustion chamber end cover 17, a window end cover 18 and a compression piston 19.

[0035] Before compression begins, the electric butterfly valve 15 disconnects the drive section 10 from the high-pressure gas tank 12. Air at 0.3-0.5 MPa is then pumped into the high-pressure gas tank 12 using the air compressor 13, serving as the power source for the piston-connecting rod system. Compressed air from the air compressor 13 pushes the piston-connecting rod system 9 from top dead center to bottom dead center. The combustion chamber end cover 17 is opened, and a certain amount of explosive powder is loaded into the injection system 5. The combustion chamber end cover 17 is bolted firmly to the combustion chamber, forming a sealed space. The gas distribution system then fills the combustion chamber with the powder injection system 5 with a certain amount of argon and nitrogen, and the air inlet valve is closed. The control and acquisition system 7 activates the oil pump, pumping the hydraulic oil from the fuel tank 1 into the hydraulic section 8, creating high-pressure hydraulic oil that brakes the piston-connecting rod system 9. At the start of compression, the electric butterfly valve connecting the high-pressure gas tank 12 and the drive section 10 opens, allowing compressed air to act on the piston-connecting rod system 9. This triggers the control and acquisition system 7, opening the oil pump pressure relief valve and rapidly reducing the oil pressure in the hydraulic section 8. Under the action of the compressed air, the piston-connecting rod system 9 rapidly moves from the bottom dead center to the top dead center. The trigger signal simultaneously controls the injector, the pressure acquisition system, and the high-speed camera 6, causing the explosive powder in the injection pipe to be sprayed into the combustion chamber under the high injection air pressure. The pressure sensor and the high-speed camera 6 begin to collect the pressure and temperature in the combustion chamber until the compression process and the explosive reaction are complete. The control and acquisition system 7 sends a signal to stop the pressure acquisition system and the high-speed camera. After compression is complete, the combustion chamber exhaust valve is opened to discharge the waste. Subsequently, the high-pressure air in the drive section 10 is released through the valve. The combustion chamber end cap 17 is opened, and acetone is introduced into the combustion chamber for cleaning to ensure a quasi-zero-dimensional system environment in the combustion chamber for the next experiment. The pressure curve is processed using MATLAB, and the high-speed image is processed using PCC software.

[0036] Example 1:

[0037] Before compression begins, 30 mg of RDX explosive powder with a particle size of 100 μm is prepared and loaded into the injector of the combustion chamber end cap. The combustion chamber is sealed using the end cap and bolts. The piston-connecting rod system is pushed to the bottom dead center of compression. Hydraulic oil is pumped into the hydraulic section using an oil pump to create high-pressure hydraulic oil, stopping the compression piston system at bottom dead center. An air compressor is used to fill the high-pressure gas tank with 0.35 MPa of air. The electric butterfly valve connecting the high-pressure gas tank to the drive section is opened. The ratio of argon to nitrogen in the combustion chamber is determined to be 1:1, and the total gas pressure is 0.234 MPa. Using the partial pressure law, the argon and nitrogen pressures are both 0.117 MPa. Argon and nitrogen are then sequentially filled into the combustion chamber using the gas distribution system at 0.117 MPa each.

[0038] At the start of compression, a signal from the control and acquisition system is triggered, opening the pressure relief valve and rapidly reducing the pressure within the hydraulic section. The piston-connecting rod system, under the action of 0.35 MPa high-pressure air, moves from bottom dead center to top dead center. Simultaneously, the high-pressure air forces the explosive powder within the injection system through the powder injection holes into the combustion chamber, where it is dispersed. The pressure acquisition system and high-speed camera record the entire process of powder injection and self-ignition.

[0039] After compression, the exhaust gas from the combustion chamber was exhausted and the inner walls of the chamber were cleaned with acetone. The valve in the drive section was then opened to release the high-pressure gas. Based on the ideal gas isentropic equation of state, given an initial pressure and temperature of 0.24 MPa and 300 K, respectively, and a final compression pressure of 4 MPa, the final compression temperature was calculated to be 863 K. MATLAB and PCC software were used to process the pressure and high-speed image data of the RDX powder under these conditions. Figure 3 and Figure 4 The discrete self-ignition process and pressure curve of RDX powder under this stimulus are shown in Figure 2. Figure 3 a is the state of RDX powder dispersed in the quasi-zero-dimensional system of the combustion chamber. After a certain induction time, RDX powder undergoes self-ignition under thermal stimulation, such as Figure 3 As shown in b. Figure 4 The pressure changes in the combustion chamber were recorded. The RDX explosive powder was discretely introduced into the combustion chamber at the top dead center of compression. After 17ms, the sample pressure rose sharply and then slowly decreased, indicating that the RDX powder underwent a self-ignition reaction. The explosion pressure was 5.5MPa.

[0040] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for the self-ignition test of explosive powder discretization based on a rapid compressor, characterized in that: The following steps are involved: 1) Determine the composition, proportion and total pressure p of the ambient gas in the rapid compressor combustion chamber, that is, determine the volume fractions A1 and A2 of the diluent argon and nitrogen; use the partial pressure formula pi = p × A i ,i=1,2, calculate the respective partial pressures; 2) loading solid explosive powder into the injection pipe of the injection system of the end cover of the rapid compressor visual combustion chamber, and sealing the visual combustion chamber with the end cover; 3) Hydraulic oil is pumped into the hydraulic section through a hydraulic pump, so that the compression piston is locked at the compression bottom dead center position under the action of high oil pressure; 4) Use a vacuum pump to evacuate the combustion chamber through the pipeline, and fill the combustion chamber with argon gas (P1) and nitrogen gas (P2) in sequence through the gas distribution system; 5) The pressure relief valve of the high-pressure oil pump is opened through the control system, and the oil pressure in the hydraulic section drops rapidly. Driven by the compressed air in the high-pressure gas tank, the compression piston-connecting rod-hydraulic piston-connecting rod-driving piston structure is rapidly compressed from the bottom dead center to the top dead center; 6) When the control system opens the pressure relief valve, it synchronously controls the injection system, pressure acquisition system, and high-speed camera system signals. The solid explosive powder in the injection system is injected into the combustion chamber through the powder injection holes on the injector under the action of high-pressure jets to form discrete powder. The high-speed camera and pressure sensor are used to record the visual image of the compression process and the dynamic pressure changes. 7) Using the known pressure data, the corresponding temperature is calculated using the ideal gas isentropic state equation. Based on the pressure curve and visualization image, the self-ignition behavior of solid explosive powder in the discretized state is analyzed, and a combustion model is established.

2. The method for self-ignition of explosive powder discretization based on a rapid compressor according to claim 1, characterized in that: The solid explosive powder is 1-30 mg of micron / nano-level cyclotrimethylene trinitramine RDX, cyclotetramethylene tetranitramine HMX or hexanitrohexaazaisopentazane CL-20 simple substance and mixed explosives.

3. The method for self-ignition test of explosive powder discretization based on a rapid compressor according to claim 1, characterized in that: The combustion chamber end cover injection system includes a high-pressure gas source, a pressure reducing valve, a pressure gauge, an injector, a carrier ferrule with a nozzle, and an injector control drive module. The high-pressure gas source is connected to the pressure reducing valve and the pressure gauge. The injector and the carrier ferrule with a nozzle are matched with a threaded seal. A signal is sent through the injector control drive module. The high-pressure gas source cooperates with the pressure reducing valve and the pressure gauge to input high-pressure gas of a set pressure into the injector to spray out the powder.

4. The method for self-ignition test of explosive powder discretization based on a rapid compressor according to claim 1, characterized in that: The control system is programmed based on LabVIEW software and can synchronously control the pressure relief valve, the ejector, the pressure acquisition system and the high-speed camera.

5. The method for self-ignition test of explosive powder discretization based on a rapid compressor according to claim 1, characterized in that: Explosive powder discretization refers to the discrete powder formed and dispersed in the combustion chamber after the explosive passes through the high-pressure ejector.

6. The method for self-ignition test of explosive powder discretization based on a rapid compressor according to claim 1, characterized in that: The self-ignition behavior of explosive powder refers to the ignition process of discrete powder under a quasi-zero-dimensional ultrafast thermal stimulation environment, which is recorded by a pressure acquisition system and a high-speed camera.

7. The method for self-ignition test of explosive powder discretization based on a rapid compressor according to claim 6, characterized in that: The heating rate under the quasi-zero-dimensional ultrafast thermal stimulation environment is 2×10 4 K / s.

8. The method for self-ignition test of explosive powder discretization based on a rapid compressor according to claim 1, characterized in that: The isentropic equation of state for an ideal gas is Where T c is the compression top dead center temperature, T0 is the initial temperature, γ is the specific heat ratio, p c is the compression top dead center pressure, and p0 is the initial pressure.

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