A Deflagration-to-Detonation Experimental System and Method with Schlieren Visualization

Abstract

The present invention discloses a schlieren visualized deflagration-to-detonation experimental system and method, which relates to the technical field of combustion and explosion testing. The system includes a combustion tube, a schlieren system, a gas distribution system, an ignition system and a pressure acquisition system; an optical observation section is provided in the combustion tube; the schlieren system photographs the deflagration-to-detonation process in the combustion tube through the optical observation section; the gas distribution system is used to provide combustible gas of set pressure to the combustion tube; the ignition system is used to ignite the combustible gas in the combustion tube; the pressure acquisition system is used to collect the pressure in the combustion tube; an obstacle plate is provided in the lower side wall along the gas transmission direction of the optical observation section, and a number of protrusions are evenly distributed on the obstacle plate. The present invention can be used to study the evolution law of flame morphology, velocity and pressure in the process of deflagration-to-detonation of combustible gas in a pipeline.

Description

Technical Field

[0001] The invention relates to the technical field of combustion and explosion testing, and in particular to a schlieren visualized deflagration-to-detonation experimental system and method. Background Art

[0002] The explosion of flammable gas leakage can cause great damage to the safety of life and property. The explosion process of flammable gas includes ignition, flame propagation acceleration, deflagration to detonation, and detonation. Among them, detonation combustion is a pressure-gain combustion with fast propagation speed and large overpressure. The explosion threat caused by gas leakage is the research focus in the field of explosion safety. Also, because detonation propagation can bring efficient thrust performance and cycle efficiency, the research on rotating detonation engines and pulse detonation engines has received widespread attention in recent years. Deflagration to detonation is an important means to obtain detonation propagation. The safety field needs to suppress the deflagration to detonation process, and the aerospace field needs to promote the deflagration to detonation process. The presence of obstacles can suppress flame propagation and accelerate the transformation of flame to detonation.

[0003] Traditional deflagration-to-detonation testing methods include pressure measurement and smoke trail methods. The pressure measurement method can obtain the velocity and overpressure during the flame propagation process; the detonation wave propagation process will leave fish-scale-like track lines on the smoke film, and the smoke trail method records the detonation process based on this characteristic. Neither the pressure measurement method nor the smoke trail method can obtain detailed flame and shock wave evolution processes during deflagration-to-detonation. Whether the deflagration-to-detonation process is suppressed or promoted requires in-depth research on the combustion reaction dynamics of the flame propagation process.

[0004] The basic principle of the Schlieren method is to use the refractive index gradient of light in the flow field to measure the airflow density in the flow field, which can be used to observe flames and shock waves in the combustion process. The flame speed will change greatly during the process of deflagration to detonation, and there will be strong disturbances at the front and inside of the flame. A high-speed camera combined with a Schlieren system can clearly study this process. Therefore, in order to deeply study the process of deflagration to detonation, it is very important to build a deflagration to detonation experimental system with Schlieren visualization. Summary of the invention

[0005] In order to overcome the defects in the above-mentioned prior art, the present invention provides a Schlieren visualization deflagration-to-detonation experimental system for studying the evolution of flame morphology, velocity and pressure during the deflagration-to-detonation process of combustible gas in a pipeline.

[0006] To achieve the above object, the present invention adopts the following technical solutions, including:

[0007] A Schlieren visualized deflagration-to-detonation experimental system, comprising: a combustion tube, a Schlieren system, a gas distribution system, an ignition system and a pressure acquisition system;

[0008] An optical observation section is provided in the combustion tube; the schlieren system captures the process of deflagration to detonation in the combustion tube through the optical observation section; the gas distribution system is used to provide combustible gas of set pressure into the combustion tube; the ignition system is used to ignite the combustible gas in the combustion tube; and the pressure collection system is used to collect the pressure in the combustion tube.

[0009] Preferably, the left and right sides of the optical observation section along the gas transmission direction are sealed with quartz glass; an obstacle plate is provided inside the lower side wall of the optical observation section along the gas transmission direction, and a plurality of protrusions are evenly distributed on the obstacle plate.

[0010] Preferably, the schlieren system includes in sequence along the light transmission direction: a light source, a collimating lens, a focusing lens, an aperture slit, a first plane mirror, a concave mirror, a second plane mirror, a knife edge and a camera;

[0011] The light emitted by the light source is converted into parallel light by a collimating lens, and then converged at the aperture slit by a focusing lens. After the light is amplified, it is reflected by a first plane mirror to the optical observation section, and then reaches the concave mirror after passing through the optical observation section. The light is focused again and reflected by a second plane mirror, so that the light is focused at the knife edge, and enters the camera after light cutting.

[0012] Preferably, the light reflected by the first plane mirror is perpendicular to the optical observation section, and the light can move horizontally along the length direction of the combustion tube, that is, the gas transmission direction.

[0013] Preferably, the combustion tube is composed of multiple sections of pipes, the optical observation section is spliced ​​in the multiple sections of pipes and the splicing position is adjustable; the combustion tube includes an acceleration section, an optical observation section and a pressure relief section in sequence along the gas transmission direction.

[0014] Preferably, the pressure acquisition system includes a second pressure sensor, a signal conditioner, an acquisition card and a computer connected in sequence; the acceleration section and the optical observation section are each provided with a second pressure sensor for collecting the pressure in the acceleration section and the optical observation section, and the collected pressure signal is transmitted to the computer in sequence through the signal conditioner and the acquisition card.

[0015] Preferably, the gas distribution system comprises: a gas distribution panel, a first pressure sensor, a digital display, and a vacuum pump;

[0016] The gas distribution panel inputs the combustible gas into the combustion pipe through a pipeline, and a ball valve is provided on the pipeline;

[0017] The first pressure sensor is arranged on the combustion tube, and is used to collect the gas pressure in the combustion tube, and is connected to the digital display to send the gas pressure to the digital display for display;

[0018] The vacuum pump is used to evacuate the gas distribution system.

[0019] Preferably, the gas distribution system further comprises: a combustible gas cylinder, an oxygen cylinder, and a premix tank;

[0020] The gas distribution panel fills the combustible gas in the combustible gas cylinder and the oxygen in the oxygen cylinder into the premixing tank according to a set ratio to obtain premixed combustible gas, and inputs the premixed combustible gas into the combustion tube.

[0021] Preferably, the ignition system includes an igniter and a semiconductor nozzle; the semiconductor nozzle is arranged in the combustion tube and close to the gas input end; the igniter is connected to the semiconductor nozzle through a cable to provide ignition energy.

[0022] A Schlieren visualized deflagration-to-detonation experimental method is applied to the above-mentioned Schlieren visualized deflagration-to-detonation experimental system, and the experimental method comprises the following steps:

[0023] S1, assemble the deflagration-to-detonation experimental system, check the air tightness of the combustion tube and the gas distribution system, and check whether the schlieren system, ignition system, and pressure acquisition system are working properly;

[0024] S2, mixing the combustible gas and oxygen according to a set ratio through a gas distribution system, and letting them stand for a period of time to ensure that the gases are evenly mixed, thereby obtaining premixed combustible gas;

[0025] S3, adjusting the Schlieren system so that the light emitted by the light source in the Schlieren system is collimated, focused and amplified and then vertically enters the optical observation section and passes through the optical observation section; the light passing through the optical observation section enters the camera of the Schlieren system after being focused and cut;

[0026] S4, the gas distribution system inputs the premixed combustible gas into the combustion tube, determines the gas pressure in the combustion tube according to the first pressure sensor provided on the combustion tube, and closes the gas distribution system after the gas pressure in the combustion tube reaches the set pressure;

[0027] S5, triggering the ignition system to ignite the gas in the combustion tube, and the gas burns in the combustion tube; the camera and pressure acquisition system record and store data.

[0028] The advantages of the present invention are:

[0029] (1) The present invention provides a Schlieren visualization deflagration-to-detonation experimental system, which can be used to study the evolution of flame morphology, velocity, and pressure during the deflagration-to-detonation process of combustible gas in a pipeline.

[0030] (2) The present invention provides an obstacle plate in the optical observation section. The process of flame deflagration to detonation in a smooth pipe is highly random and difficult to capture. The presence of obstacles can promote the process of flame deflagration to detonation.

[0031] (3) The combustion tube in the present invention is composed of multiple sections. In the specific implementation, the position of the optical observation section can be changed. At the same time, the schlieren system can adjust the light incident position according to the position of the optical observation section, which is convenient for studying the flame morphology of the combustible gas combustion process under different initial pressures and the difference between the deflagration to detonation process.

[0032] (4) The present invention provides pressure sensors in the acceleration section and the optical observation section, respectively, which can synchronously measure and record the overpressure of the shock wave, flame, deflagration to detonation, detonation and other processes during the experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of a Schlieren visualized deflagration-to-detonation experimental system of the present invention.

[0034] Figure 2 It is a schematic diagram of the structure of the optical observation section of an embodiment of the present invention.

[0035] Figure 3 It is a schematic diagram of the structure of the Schlieren system of an embodiment of the present invention.

[0036] Figure 4 It is a schlieren diagram of the deflagration-to-detonation propagation process of an embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 1-combustion tube, 2-schlieren system, 3-gas distribution system, 4-ignition system, 5-pressure collection system, 11-optical observation section, 12-acceleration section, 13-pressure relief section, 21-light source, 22-collimating lens, 23-focusing lens, 24-aperture slit, 25-first plane mirror, 26-concave mirror, 27-second plane mirror, 28-knife edge, 29-camera, 30-gas distribution panel, 31-first pressure sensor, 32-digital display, 33 - vacuum pump, 34 - combustible gas cylinder, 35 - oxygen cylinder, 36 - premixing tank, 37 - gas distribution hole, 38 - ball valve, 39 - valve, 41 - semiconductor nozzle, 42 - igniter, 51 - second pressure sensor, 52 - signal conditioner, 53 - acquisition card, 54 - computer, 110 - closed cover plate, 111 - first layer of quartz glass, 112 - second layer of quartz glass, 113 - obstacle plate, 114 - upper wall lining plate, 115 - flange. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, a Schlieren visualized deflagration-to-detonation experimental system of this embodiment includes: a combustion tube 1, a Schlieren system 2, a gas distribution system 3, an ignition system 4 and a pressure acquisition system 5.

[0041] The combustion tube 1 is installed on the detonation test platform. In this embodiment, the combustion tube 1 is composed of 6 sections of pipelines, among which the first 4 sections of the combustion tube 1 along the gas transmission direction have the same structure, all of which are acceleration sections 12; the 5th section of the pipeline is the optical observation section 11; and the 6th section of the pipeline is the pressure relief section 13. The tube body material of the combustion tube 1 is 6061 aluminum alloy, and the joints of each section of the pipeline are sealed with silicone pads and high vacuum sealing silicone grease. The interior of the combustion tube 1 is a square channel of 80×80 mm. The left and right sides of the 5th section of the combustion tube 1, i.e., the optical observation section 11, along the gas transmission direction are sealed with quartz glass. In a specific embodiment, the position of the optical observation section 11 can also be changed in multiple sections of the pipeline.

[0042] The gas distribution system 3 includes: a gas distribution panel 30, a first pressure sensor 31 (model Omega PXM309-3.5A10V) arranged on the combustion tube 1, a digital display 32 connected to the first pressure sensor 31, a vacuum pump 33, a combustible gas cylinder 34, an oxygen cylinder 35, and a premixing tank 36. The gas distribution panel 30 is used to fill the combustible gas in the combustible gas cylinder 34 (the combustible gas is one or more mixed gases of hydrogen, methane, propane, etc.) and the oxygen (combustion-supporting gas) in the oxygen cylinder 35 into the premixing tank 36 according to a set ratio, and let it stand for 24 hours to ensure that the gas is evenly mixed to obtain the premixed combustible gas. The gas distribution panel 30 is used to connect the gas output end of the premixing tank 36 to the gas input end of the combustion tube 1 through a pipeline, and a ball valve 38 is provided on the pipeline, and a gas distribution hole 37 is provided at the gas input end of the combustion tube 1. The vacuum pump 33 is used to evacuate the gas distribution system 3 and extract the gas in all pipelines in the gas distribution system 3 to ensure safety and no leakage. Before the experiment, the vacuum pump 33 is used to extract the gas in the combustion tube 1 and the gas distribution panel 30. When the reading in the digital display 32 is less than 0.10 kPa, the combustion tube 1 is in a vacuum state, and the premixed combustible gas can be filled into the combustion tube 1. After the experiment is over, the vacuum pump 33 is turned on again to extract the exhaust gas in the combustion tube 1 to form a vacuum state again. The gas distribution system 3 is also connected to the atmospheric environment through a valve 39.

[0043] The ignition system 4 comprises a semiconductor electric nozzle 41 and an igniter 42 (model TYQ-20-10) arranged at the wall surface of the gas input end of the combustion tube 1. The igniter 42 is connected to the semiconductor electric nozzle 41 through a cable to provide ignition energy.

[0044] The pressure acquisition system 5 includes: 8 second pressure sensors 51, a signal conditioner 52, an acquisition card 53 and a computer 54. Among them, 4 second pressure sensors 51 are arranged at equal intervals on the third and fourth sections of the combustion tube 1, and the other 4 pressure sensors are arranged at equal intervals on the fifth section of the combustion tube 1, i.e., the optical observation section 11; the second pressure sensor 51 is fixed on the combustion tube 1 using packaging technology, and the sensor element is parallel to the upper wall of the pipeline. The computer 54 is installed with a LabVIEW development program for pressure recording. The model of the second pressure sensor 51 is PCB 113B24, and the model of the signal conditioner 52 is PCB482C05. During the experiment, the pressure signals collected by each second pressure sensor 51 are transmitted to the LabVIEW program in the computer 54 through the signal conditioner 52 and the acquisition card 53 for display.

[0045] like Figure 2 As shown, the optical observation section 11 in the combustion tube 1 includes: a closed cover plate 110, a first layer of quartz glass 111, a second layer of quartz glass 112, an obstacle plate 113, an upper wall lining plate 114 and a flange 115. The optical observation section 11 is located at the fifth section of the combustion tube 1 and is used for observation with the Schlieren system 2. The optical observation section 11 is 630 mm long and has an inner diameter of 80×96 mm. Through holes are provided on the left and right side walls along the gas transmission direction, with a size of 470×120×30 mm. The through holes on each side wall are sequentially provided with a first layer of quartz glass 111 and a second layer of quartz glass 112 from the outside to the inside for sealing, and then the two layers of quartz glass are sealed with a closed cover plate 110. A through hole is also provided in the middle of the closed cover plate 110, with a size of 450×80 mm. The thickness of the first layer of quartz glass 111 is 28 mm, and the thickness of the second layer of quartz glass 112 is 2 mm. The two layers of quartz glass are made of the same material. Since flame combustion and explosion will wear the glass surface, in order to make the experiment economical and sustainable, a 2 mm second layer of quartz glass is set separately on the inside as a loss item. The obstacle 113 plate is 630 mm long, and the bottom layer is 8 mm thick. There are 10×10×10 mm small square column protrusions on it. Along the length direction of the optical observation section 11, that is, the gas transmission direction, the small square columns are spaced 10.67 mm apart. The size of the upper wall lining plate 114 is 630×80×8 mm, and there are 4 circular holes in the middle for the end of the second pressure sensor 51 to be placed. The obstacle plate 113 and the upper wall lining plate 114 are both fixed to the optical observation section 11 by screws. As a result, the internal channel of the optical observation section 11 is 80×80 mm and contains obstacles. The existence of obstacles can accelerate the transition from flame deflagration to detonation, and this has been widely demonstrated.

[0046] like Figure 3As shown, the Schlieren system 2 of the deflagration-to-detonation experimental system includes: a light source 21, a collimating lens 22, a focusing lens 23, an aperture slit 24, a first plane mirror 25, a concave mirror 26, a second plane mirror 27, a knife edge 28 and a camera 29 in sequence along the light transmission direction. The light emitted by the light source 21 is converted into parallel light by the collimating lens 22, and then converges at the aperture slit 24 by the focusing lens 23. After the light is amplified, it is reflected by the first plane mirror 25 to the optical observation section 11, passes through the optical observation section 11, and reaches the concave mirror 26. After the light is focused again, it is reflected by the second plane mirror 27, so that the light is focused at the knife edge 28, and enters the camera 29 after light cutting.

[0047] In the present invention, the light reflected by the first plane mirror 25 is perpendicular to the optical observation section 11, and the light reflected by the first plane mirror 25 can move horizontally along the length direction of the optical observation section 11, that is, the gas transmission direction, so that the position of the light passing through the optical observation section 11 can be adjusted according to specific needs. The light reflected by the second plane mirror 27 is focused on the knife edge 28, and the light entering the camera 29 needs to enter the lens of the camera 29 to the greatest extent and remain vertical. In this embodiment, the light source 21 is a xenon light source, the camera 29 is a high-speed camera, and the camera 29 is a FASTCAM SA-Z camera. The maximum shooting speed can reach 224000 fps, and the maximum resolution can reach 1024×1024.

[0048] Based on the above-mentioned Schlieren visualization deflagration-to-detonation experimental system, the Schlieren visualization deflagration-to-detonation experimental method implemented specifically includes the following steps:

[0049] S1, such as Figure 1 , 2 As shown in FIG. 3 , the deflagration-to-detonation experimental system is assembled on the detonation experimental platform according to the above requirements; the vacuum pump 33 is used in conjunction with the pressure gauge 32 to check the air tightness of the combustion tube 1 and the gas distribution system 3; and the experimental equipment such as the schlieren system 2, the ignition system 4, and the pressure acquisition system 5 are tested to see whether they are working normally.

[0050] S2, according to the experimental needs, the combustible gas in the combustible gas cylinder 34 and the oxygen in the oxygen cylinder 35 are input into the premixing tank 36 according to the set ratio through the gas distribution panel 30, and the premixing tank 36 is left to stand for 24 hours to ensure that the gases are evenly mixed, so as to obtain premixed combustible gas.

[0051] S3, adjust the schlieren system 2 so that the reflected light from the first plane mirror 25 enters the optical observation section 11 vertically, and the position of the light passing through the optical observation section 11 is adjusted according to the experiment; adjust the positions of the concave mirror 26, the second plane mirror 27, the knife edge 28 and the camera 29 so that the light enters the camera 29 lens to the greatest extent and remains vertical to the lens.

[0052] S4, fill the gas in the premixing tank 36 into the combustion tube 1 through the gas distribution system 3, confirm the pressure in the combustion tube 1 according to the indication of the pressure gauge 32, close the gas distribution hole 37 at the gas input end of the combustion tube 1 after reaching the requirement, and use the vacuum pump 33 to extract the gas in the gas distribution panel 30 and the gas distribution system 3 pipeline.

[0053] S5, check again whether the experimental equipment is safe, adjust the parameters of the camera 29, and after confirmation, trigger the igniter 42, the semiconductor nozzle 41 discharges and ignites the gas in the combustion tube 1, and the gas burns in the combustion tube 1; the camera 29 and the pressure acquisition system 5 record and store the data.

[0054] After the experiment is over, the gas distribution hole 37 is opened, the vacuum pump 33 is turned on, and the combustion tube 1 is evacuated; and the photos recorded by the camera 29 are checked to see whether they are the process of deflagration to detonation.

[0055] like Figure 4 Shown is the Schlieren image of the deflagration-to-detonation process of a hydrogen-oxygen premixed gas at an equivalent of 17.67 kPa obtained by the deflagration-to-detonation experimental system and experimental method based on Schlieren visualization. Figure 4 In the deflagration-to-detonation experiment, the light passes through the optical test section 11 in the center, the shooting parameters of the camera 29 are 120,000 fps, the resolution is 512×232, and the image time interval is Δt=8.33 μs.

[0056] According to the position distance ΔL of the flame front in the two Schlieren images (the red dotted line in the image is the flame front, which is the flame front or the detonation wave front) and the shooting time interval Δt of the two Schlieren images, the flame speed v can be calculated using the formula v=ΔL / Δt. Figure 4 The schlieren images with sequence numbers 1, 2, and 3 are used to calculate the flame front speeds of sequence numbers 2 and 3 to be 1000 m / s and 1200 m / s respectively. Figure 4 The schlieren images of sequence numbers 4, 5, and 6 show that the speeds of the flame front (detonation wave front) in sequence numbers 5 and 6 are 3000 m / s and 2880 m / s respectively. The detonation speed of the 17.67 kPa hydrogen-oxygen premixed gas calculated according to detonation theory is 2742.2 m / s. Compared with the experimental results, it can be determined that the detonation occurred at sequence number 4.

[0057] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A Schlieren visualization deflagration-to-detonation experimental system, characterized in that: include: Combustion tube (1), Schlieren system (2), gas distribution system (3), ignition system (4) and pressure collection system (5); The combustion tube (1) is provided with an optical observation section (11); the schlieren system (2) photographs the process of deflagration-to-detonation transition in the combustion tube (1) through the optical observation section (11); the gas distribution system (3) is used to provide combustible gas of a set pressure into the combustion tube (1); the ignition system (4) is used to ignite the combustible gas in the combustion tube (1); and the pressure collection system (5) is used to collect the pressure in the combustion tube (1); The combustion tube (1) is composed of a plurality of pipe sections, the optical observation section (11) is spliced ​​into the plurality of pipe sections and the splicing position is adjustable; the combustion tube (1) comprises an acceleration section (12), an optical observation section (11) and a pressure relief section (13) in sequence along the gas transmission direction; The optical observation section (11) comprises: a closed cover plate (110), a first layer of quartz glass (111), a second layer of quartz glass (112), an obstacle plate (113), an upper wall lining plate (114), and a flange (115); The optical observation section (11) is provided with through holes on the left and right side walls along the gas transmission direction, and the through holes on each side wall are provided with a first layer of quartz glass (111) and a second layer of quartz glass (112) in sequence from the outside to the inside for sealing, and then the two layers of quartz glass are sealed with a closed cover plate (110); An obstacle plate (113) is arranged in the lower side wall of the optical observation section (11) along the gas transmission direction, and a plurality of small square column protrusions are evenly distributed on the obstacle plate (113). The small square columns are spaced 10.67 mm apart in the gas transmission direction of the optical observation section (11); An upper wall lining plate (114) is provided in the upper side wall of the optical observation section (11) along the gas transmission direction, and four circular holes are opened in the middle of the upper wall lining plate (114) for placing the end of the second pressure sensor (51); the second pressure sensor (51) is used to collect the pressure in the optical observation section (11); The obstacle plate (113) and the upper wall lining plate (114) are both fixed to the optical observation section (11) by screws; The optical observation section (11) is connected to the combustion tube (1) via a flange (115).

2. The Schlieren visualization deflagration-to-detonation experimental system according to claim 1, characterized in that: The schlieren system (2) comprises, in order along the light transmission direction: a light source (21), a collimating lens (22), a focusing lens (23), an aperture slit (24), a first plane mirror (25), a concave mirror (26), a second plane mirror (27), a knife edge (28), and a camera (29); Light emitted by the light source (21) is converted into parallel light by a collimating lens (22), and then converged at the aperture slit (24) by a focusing lens (23). The light is amplified and reflected by a first plane mirror (25) to the optical observation section (11). After passing through the optical observation section (11), the light reaches the concave mirror (26). The light is focused again and reflected by a second plane mirror (27), so that the light is focused at the knife edge (28), and then enters the camera (29) after light cutting.

3. The Schlieren visualization deflagration-to-detonation experimental system according to claim 2, characterized in that: The light reflected by the first plane mirror (25) is perpendicular to the optical observation section (11), and the light can move horizontally along the length direction of the combustion tube (1), that is, the gas transmission direction.

4. The Schlieren visualization deflagration-to-detonation experimental system according to claim 1, characterized in that: The pressure acquisition system (5) comprises a second pressure sensor (51), a signal conditioning instrument (52), an acquisition card (53) and a computer (54) which are connected in sequence; the acceleration section (12) and the optical observation section (11) are both provided with a second pressure sensor (51) for acquiring pressure in the acceleration section (12) and the optical observation section (11), and the acquired pressure signal is sequentially transmitted to the computer (54) through the signal conditioning instrument (52) and the acquisition card (53).

5. The Schlieren visualization deflagration-to-detonation experimental system according to claim 1, characterized in that: The gas distribution system (3) comprises: a gas distribution panel (30), a first pressure sensor (31), a digital display (32), and a vacuum pump (33); The gas distribution panel (30) inputs the combustible gas into the combustion pipe (1) through a pipeline, and a ball valve (38) is provided on the pipeline; The first pressure sensor (31) is arranged on the combustion tube (1) and is used to collect the gas pressure in the combustion tube (1), and is connected to the digital display (32) to send the gas pressure to the digital display (32) for display; The vacuum pump (33) is used to evacuate the gas distribution system (3).

6. The Schlieren visualization deflagration-to-detonation experimental system according to claim 5, characterized in that: The gas distribution system (3) further comprises: a combustible gas cylinder (34), an oxygen cylinder (35), and a premixing tank (36); The gas distribution panel (30) charges the combustible gas in the combustible gas cylinder (34) and the oxygen in the oxygen cylinder (35) into the premixing tank (36) according to a set ratio to obtain premixed combustible gas, and inputs the premixed combustible gas into the combustion tube (1).

7. The Schlieren visualization deflagration-to-detonation experimental system according to claim 1, characterized in that: The ignition system (4) comprises an igniter (42) and a semiconductor electric nozzle (41); the semiconductor electric nozzle (41) is arranged in the combustion tube (1) and close to the gas input end; the igniter (42) is connected to the semiconductor electric nozzle (41) via a cable to provide ignition energy.

8. A Schlieren visualization deflagration-to-detonation experimental method, characterized in that: Using the Schlieren visualization deflagration-to-detonation experimental system described in any one of claims 1 to 7, the experimental method comprises the following steps: S1, assemble the deflagration-to-detonation experimental system, check the air tightness of the combustion tube (1) and the gas distribution system (3), and check whether the schlieren system (2), the ignition system (4), and the pressure acquisition system (5) are working normally; S2, mixing the combustible gas and oxygen according to a set ratio through the gas distribution system (3), and letting it stand for a period of time to ensure that the gas is evenly mixed, thereby obtaining a premixed combustible gas; S3, adjusting the Schlieren system (2) so that the light emitted by the light source (21) in the Schlieren system (2) is collimated, focused and amplified before being vertically incident on the optical observation section (11) and passing through the optical observation section (11); the light passing through the optical observation section (11) is focused and cut before entering the camera (29) of the Schlieren system (2); S4, the gas distribution system (3) inputs the premixed combustible gas into the combustion tube (1), determines the gas pressure in the combustion tube (1) according to a first pressure sensor (31) provided on the combustion tube (1), and closes the gas distribution system (3) after the gas pressure in the combustion tube (1) reaches a set pressure; S5, triggering the ignition system (4) to ignite the gas in the combustion tube (1), and the gas burns in the combustion tube (1); the camera (29) and the pressure acquisition system (5) record and store data.

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