Visual test device for accurately testing the effect of combustible gas unsteady-state detonation flame arrester

Abstract

The present invention discloses a visualization test device and method for accurately testing the effect of a non-steady-state detonation flame arrester for combustible gas, including a vacuum system, an automatic gas distribution system, a schlieren camera system, a non-steady-state detonation blocking test combustion pipeline, a test and data acquisition system, and a high-voltage ignition and synchronization control system. The present invention adopts a method combining high-speed camera technology and schlieren optical technology to shoot and record the process of deflagration to detonation and the flame arrester blocking process in the pipeline, realizes the visualization of the whole process of non-steady-state detonation generation and blocking, and accurately and intuitively presents the dynamic change law of the shape and position of the flame and detonation wave over time. The dynamic rising characteristics of the pressure in the pipeline are measured by a pressure sensor, and the relationship between the pressure in the pipeline and the characteristics of the flame and detonation wave can be analyzed in combination with high-speed schlieren images. The changes in light intensity in the pipeline are detected by a photodiode, so as to obtain the position changes of the initial flame and the later detonation wave, and the propagation speed of the flame and the detonation wave at each moment can be calculated in combination with high-speed schlieren image analysis.

Description

Technical Field

[0001] The invention belongs to the field of safety technology, and in particular relates to a visual test device and method for accurately testing the effect of a non-steady-state detonation flame arrester of a premixed gas of combustible gas and air or oxygen. Background Art

[0002] Combustible gases (such as hydrogen, methane and ethylene) are widely used in the fields of petroleum, electricity, mining, metallurgy, transportation, chemical industry and gas supply due to their advantages of cleanliness, high efficiency and wide sources. On the other hand, due to the dangerous characteristics of combustible gases such as flammability, explosion, leakage and low ignition energy, special attention should be paid to safety issues in their production, transportation, storage and application. If the combustible gas is improperly controlled or used, so that combustion-supporting gases such as air or oxygen enter the confined space containing combustible gas, premixed gas will be formed, which can easily cause accidents such as fire and explosion. Industrial pipelines are common confined spaces. There are many types of process flows in general industrial pipelines, the production environment conditions vary, and the types of media transported are many and the conditions are harsh. Therefore, the causes and evolution of fire and explosion accidents in industrial pipelines are more complicated. When a premixed gas explosion occurs in an industrial pipeline, the combustion mechanism of the flame usually undergoes a transition from laminar flow to turbulent flow, and the combustion wave also develops from slow combustion to deflagration, and may even form a highly destructive detonation in the end. Detonation is a form of combustion reaction that propagates at supersonic speed relative to the front medium in the form of shock wave compression. Its formation and propagation mechanism is very complex, involving chemical reaction kinetics, shock wave dynamics, fluid mechanics and other aspects. It is one of the problems that have not been completely solved in the field of combustion and industrial safety. The formation of detonation waves can be achieved through two basic processes: direct initiation and the transformation from deflagration to detonation. Direct initiation requires a strong ignition source, which forms a strong shock wave through instantaneous energy release and then develops into a detonation wave; while the process of deflagration to detonation requires less initiation energy, and the deflagration wave gradually develops into a detonation wave under certain conditions, which is affected by many factors such as turbulence, shock wave action, shear layer instability and boundary layer. The ignition process in actual engineering often uses a lower ignition energy, so the formation of detonation generally goes through the process of deflagration to detonation. In the experiment, a combustion pipeline with obstacles is usually used to simulate the process of deflagration to detonation of combustible premixed gas in an industrial pipeline. At this time, the process of deflagration to detonation actually includes two stages: the gradual acceleration of the deflagration wave and the sudden formation of the detonation wave. First, under certain conditions, a low-speed flame can be continuously accelerated to become a high-speed turbulent flame under the action of obstacles; then a local detonation center, namely a detonation hotspot, can be generated in the instability area of ​​the boundary layer or near the turbulent flame surface. The stronger compression wave generated by the hotspot detonation induces a stronger chemical reaction during the outward propagation, forming a detonation wave, and then forming a non-steady-state overdriven detonation wave, which continues to grow and catch up with the leading shock wave. The overdriven detonation wave first accelerates, propagates a certain distance, and then decays to a Chapman-Jouguet (CJ) steady-state detonation wave. The later steady-state CJ detonation can be qualitatively and quantitatively analyzed using the classical CJ ​​theory and the ZND (Zeldovich, von Neumann, Doring) model, but the initial non-steady-state detonation is unpredictable.Although there is a qualitative explanation theory for the formation and initiation mechanism of hotspots during deflagration-to-detonation, the critical initiation conditions, time and location of hotspot formation are still unclear, and there is a lack of quantitative prediction results. The process of accelerating the deflagration wave to form a detonation wave is essentially controlled by the interaction between the combustion reaction zone and the nonlinear pressure wave, and also depends on the formation of critical initiation conditions. Even for an explosive mixture with given initial and boundary conditions, it is still difficult to predict whether or when and where the deflagration-to-detonation phenomenon will occur. Therefore, it is usually difficult to control the formation of deflagration-to-detonation in experiments, which brings difficulties to engineering applications, such as the design of detonation flame arresters. In addition, due to the high cost and danger of gas combustion and explosion experiments, high-performance computers are currently used more at home and abroad to conduct numerical simulation studies on the deflagration-to-detonation process, and there is a lack of experimental technology platform experiments that can accurately control the formation of deflagration-to-detonation.

[0003] At the same time, the existing explosion test platform is also difficult to accurately measure and control non-steady states such as overdriven detonation in the early stage of detonation. The speed and pressure of the initial overdriven detonation wave are greater than the later CJ steady-state detonation. The pressure of its wave surface can reach nearly twice the pressure of the CJ steady-state detonation wave surface, and has greater destructive power. Preventing the formation of overdriven detonation waves, or blocking the overdriven detonation waves that have been formed to reduce their destructive power and other related research are of great significance for the prevention and treatment of explosion accidents. Flame arresters are often used in industrial processes to provide protection for the storage, transportation and chemical processing equipment of flammable gases. Flame arresters refer to devices that allow airflow but prevent deflagration or detonation flames from propagating in gas pipelines and related equipment. They are an effective device that quenches flames and helps the free flow of gas in the system. Among them, the structure of the detonation-proof flame arrester is the most complex, requiring it to quench the detonation front moving at supersonic speed and withstand the huge pressure generated by the detonation wave. In-tube detonation arresters are mainly divided into two types: steady-state and non-steady-state. Compared with steady-state detonation arresters, the non-steady-state detonation wave passing through the non-steady-state detonation arrester mainly involves the overdriven detonation formed by the conversion of deflagration to detonation. Its propagation speed is faster and the detonation wave surface pressure is greater. Therefore, the explosion-proof effect of the non-steady-state detonation arrester is required to be higher. At present, there are few devices for testing the fire-proof effect of non-steady-state detonation arresters at home and abroad, and the existing devices have great uncertainty. The detonation wave entering the flame arrester may already be a steady-state detonation wave with a smaller wave surface pressure, rather than a steady-state overdriven detonation wave. Therefore, it is impossible to ensure the blocking effect of the flame arrester on the more powerful overdriven detonation wave. If these traditional testing devices with large uncertainties are used in industrial processes, there will be great safety risks.

[0004] Visualizing the process of the transformation from deflagration to detonation of combustible premixed gas, quantifying the length of the pipeline required for the process of deflagration to detonation, and developing accurate testing technology for the flame arresting effect of non-steady-state detonation flame arresters can not only reveal the mechanism of deflagration to detonation, but also provide a theoretical basis for the development of more efficient non-steady-state detonation flame arresters. At the same time, it provides reliable experimental basis and technical guidance for the prevention and control of explosion accidents and the safe use of gas fuels. Summary of the invention

[0005] The purpose of the present invention is to provide a visual test device and method that can observe the process of premixed gas of combustible gas and air or oxygen from deflagration to detonation and can accurately test the effect of non-steady-state detonation flame arrester in view of the shortcomings of the prior art. The device can be used for: (1) studying the characteristics and laws of the process of premixed gas from deflagration to detonation under the influence of factors such as different combustible gas components, premixed gas with different equivalence ratios, different ignition positions, different ignition energies, and obstacles of different heights (i.e., different blocking rates), and further improving the mechanism of deflagration to detonation; (2) accurately testing the blocking effect of non-steady-state detonation flame arrester on non-steady-state detonation wave; (3) realizing the visualization of the process of deflagration to detonation and the flame arresting effect of non-steady-state detonation flame arrester.

[0006] The technical solution adopted by the present invention is as follows: a visual test device for accurately testing the effect of a combustible gas non-steady-state detonation flame arrester. The entire test device includes a vacuum system, an automatic gas distribution system, a schlieren camera system, a non-steady-state detonation blocking test combustion pipeline, a test and data acquisition system, and a high-voltage ignition and synchronization control system.

[0007] The vacuum system includes a vacuum pump and a vacuum pressure gauge, wherein the vacuum pump device is used to extract the air in the combustion pipeline. During the test, the air inlet at the left end of the pipeline is closed, and the vacuum pump is connected to the pressure relief port at the right end of the downstream pipeline to start pumping air. When the reading in the vacuum pressure gauge connected to the upper wall of the upstream pipeline is equal to zero (or less than zero, related to the local atmospheric pressure) and remains stable for a period of time, the vacuum state is reached, and the vacuum pump is turned off at this time.

[0008] The automatic gas distribution system is used to configure the target concentration of combustible gas. The concentration of combustible gas is controlled by a high-precision mass flow meter (MFC) in the shell, and all flow meters are directly controlled by the computer of the control platform through solenoid valves. When distributing gas, the concentration parameters in the computer supporting software are set, and the combustible gas and combustion-supporting gas (air or oxygen) in the raw gas cylinder are transported into the gas mixing chamber at the target equivalent ratio for uniform mixing, and then connected to the combustion pipeline intake valve through a pipeline.

[0009] The Schlieren camera system includes a Schlieren instrument and a high-speed camera, and is arranged in a standard "Z" shape, with the combustion pipe located in the center path of the optical path. The Schlieren instrument includes a Schlieren light source, a focusing lens, a slit, a pair of reflective concave mirrors and a Schlieren knife edge. The instrument is a general optical display instrument used to observe the density and temperature distribution of a transparent medium and the change in the refractive index of the medium. When a premixed flame or detonation wave propagates in a pipe, there will be an obvious density difference near the front of the flame or reaction zone. When the light passes through the flow field, its direction, position and optical path will change. Therefore, optical measurement methods can be used to capture these density discontinuities without interfering with the internal flow field. After the light emitted by the Schlieren point light source passes through the focusing lens, the filament image is formed on the slit. The slit is adjusted to generate a divergent beam, which is transmitted to the corresponding reflective concave mirror. The generated parallel beam passes through the combustion pipe and is received by the reflective concave mirror on the other side, generating a convergent beam, which then enters the high-speed camera through the Schlieren knife edge and the focusing lens. The high-speed camera records the first-order derivative distribution image of the flow field density to intuitively present the flame evolution and the process of deflagration to detonation in the pipeline. The flame and detonation wave propagation speeds can be calculated from the photos taken by the high-speed camera.

[0010] The non-steady-state detonation blocking test combustion pipeline is mainly used to observe and determine the formation mode and position of non-steady-state detonation in the combustion pipeline, ensure the rapid formation of deflagration to detonation within a certain distance from the ignition position, and test the blocking effect of the non-steady-state detonation flame arrester on the non-steady-state detonation wave. The non-steady-state detonation blocking test combustion pipeline can also be used to study the characteristics of deflagration to detonation of premixed gases with different components or the same components but different equivalence ratios, and the Schlieren technology and high-speed camera are combined to obtain Schlieren photos to calculate the distance between the detonation occurrence position and the ignition position. Repeat the test multiple times under the same test conditions to obtain the run-up distance required for deflagration to detonation under these conditions.

[0011] The combustion pipeline for the non-steady-state detonation blocking test is a straight pipeline with a horizontal rectangular cross-section, which includes six parts of the combustion pipeline, namely: the upstream pre-test pipeline, the upstream segmented combined pipeline, the expansion joint, the intermediate pipeline, the non-steady-state detonation fire-blocking section and the downstream pipeline. Among them, except for the expansion joint, the walls on both sides of the remaining pipelines are made of quartz glass, which is convenient for the high-speed Schlieren camera system to capture the Schlieren images in the pipeline, realize the visualization of the flame propagation process, the process of deflagration to detonation and the process of detonation blocking, so as to determine the formation position of the non-steady-state detonation and observe the fire-blocking effect of the fire-blocking section. The upper and lower walls of all pipelines are made of stainless steel plates, and the front end and the rear (end) end and the end wall are also made of stainless steel plates. Except for the fire-blocking section, the upper and lower walls of the other parts of the pipeline are symmetrically arranged with continuous triangular obstacles made of stainless steel. The disturbance and acceleration effect of the continuous triangular obstacles on the flame can make the deflagration to detonation form within a shorter distance. The non-steady-state detonation fire-blocking section includes a fire-blocking core and a stainless steel shell. The fire-blocking core can be selected from a variety of commonly used fire-blocking cores corresponding to detonation-resistant flame arresters, such as corrugated plates, foam metals, and filled gravel, etc., to test the suppression effect of fire-blocking sections of different materials on unsteady-state detonation. Optical glass is installed on the left and right sides of the fire-blocking section to observe the blocking process of unsteady-state detonation in the fire-blocking section. The stainless steel shell of the pipeline is used to fix the internal fire-blocking core and connect it with the external pipeline.

[0012] In order to ensure that the test device is indeed effective in the actual industrial process, based on the small-scale laboratory test, the size of the test device can be increased as a whole, and then connected to a larger non-steady-state detonation flame arrester, so as to accurately test the flame-blocking effect of non-steady-state detonation flame arresters of various sizes to meet the needs of industrial applications. In addition to different flame-blocking core materials, industrial flame arresters of different structures can also be replaced to achieve accurate measurement of the flame-blocking effect of various types of detonation flame arresters.

[0013] An exhaust pipeline is arranged on the lower side wall near the rightmost end of the downstream pipeline, and an insulating valve is set. It is opened when the pipeline is inflated to ensure smooth airflow in the pipeline and prevent gas congestion in the pipeline from causing overpressure in the pipeline. A pressure relief port is arranged on the end wall of the downstream pipeline, and an insulating valve is set. It is opened when vacuuming to meet the vacuuming from the pressure relief port; it is closed when inflating to allow the displaced air and excess mixed gas to be discharged from the exhaust pipeline on the lower wall; it is opened during the test to discharge the combustion products and achieve pressure relief, thereby ensuring the safety of the deflagration-to-detonation test in the pipeline. An insulating valve is set on the left end wall of the upstream pre-test pipeline and the upstream segmented combined pipeline to control the start and end of the inflation process.

[0014] Accurately determining the location of the transition from deflagration to detonation is the key point and one of the difficulties in testing the effect of the non-steady-state detonation flame arrester. Therefore, a pre-test test is required before the formal start of the flame arrester effect detection test. The purpose is to preliminarily determine the length of the pipeline that the flame needs to propagate before the non-steady-state detonation occurs, that is, the run-up distance of the transition from deflagration to detonation, and further ensure that the pipeline length from the flame arrester section to the ignition position is the run-up distance during the flame arrester effect test, so that the transition from deflagration to detonation occurs right in front of the flame arrester section, ensuring that the non-steady-state detonation wave at the initial stage of the detonation enters the flame arrester section smoothly, and finally realizing the accurate test of the effect of the flame arrester section in resisting non-steady-state detonation. During the pre-test, the upstream pre-test pipeline, the non-steady-state detonation flame arrester section and the downstream pipeline are first connected, and the location of the transition from deflagration to detonation is observed through high-speed schlieren images and the run-up distance is calculated. In addition, during the pre-test, setting the same other parameters but different heights of the obstacle pipeline can study the characteristics of the premixed gas deflagration to detonation process under the influence of different blockage rates. Here, the blockage rate is defined as the ratio of twice the number of obstacles in the pipeline (two pairs of obstacles on the upper and lower walls are arranged symmetrically) to the height of the pipeline. After the run-up distance is obtained by testing, it is used to test the fire-blocking effect of the non-steady-state detonation flame arrester. Usually, the length of the upstream pre-test pipeline deviates from the run-up distance. At this time, if the upstream pipeline is reprocessed, it will delay the progress of the project, and the impact of the increased pipeline length on the flow field is difficult to effectively adjust. It is also necessary to continuously adjust the length of the upstream pipeline to keep it consistent with the run-up distance. The process is complicated and time-consuming. Therefore, after determining the run-up distance, it is necessary to use an adjustable pipeline to quickly adjust the pipeline length. If the length of the upstream pre-test pipeline is greater than or less than the run-up distance measured in the pre-test, it is necessary to replace the upstream pre-test pipeline with an adjustable pipeline structure formed by the combination of the upstream segmented combined pipeline, the expansion joint and the intermediate pipeline, and then connect the fire-blocking section and the downstream pipeline. The upstream segmented combined pipeline is composed of several equally structured pipe sections, which are used to increase or decrease pipe sections according to the results of preliminary tests. The expansion joints and intermediate pipelines are then used to make the sum of the upstream segmented combined pipeline, the expansion joints and the intermediate pipeline the run-up distance, ensuring that the unsteady-state detonation occurs directly in front of the fire-blocking section.

[0015] The expansion joint is a specially made short section of pipe that can adjust its length within the range of expansion and contraction. It is mainly used to compensate for the change in the location of the non-steady-state detonation caused by the change in the length of the pipe and its own influence on the flow field. After the upstream pre-test pipeline is replaced with a combination structure of the upstream segmented combined pipeline, the expansion joint and the intermediate pipeline, the position of the deflagration to detonation (i.e. the location of the non-steady-state detonation) may be slightly advanced or delayed relative to the pre-test. Therefore, it is necessary to connect an expansion joint to the pipeline. If the position of the deflagration to detonation is advanced, this small section of the expansion joint is shortened; if the position of the deflagration to detonation is delayed, this small section of the expansion joint is extended. On the basis of ensuring that the other parts of the pipeline remain unchanged, the location of the non-steady-state detonation is controlled at the run-up distance, ensuring that the non-steady-state detonation wave enters the fire-blocking section. The upper and lower walls of the expansion joint are made of stainless steel, and the connection with the upstream pipeline and the fire-blocking section uses a double-flange limited expansion joint to connect both sides with the flange. During installation, adjust the connection length between the two ends of the expansion joint and the flange, tighten the gland bolts diagonally and evenly, and then adjust the limit nuts. In this way, the expansion joint can be extended or shortened within the expansion range, and the expansion amount is locked to ensure the safe operation of the pipeline. Since the left and right walls of the expansion joint are also made of stainless steel, visualization cannot be guaranteed in this small section, so a section of visible intermediate pipeline needs to be connected behind it (that is, before the fire-blocking section) to determine the specific position of the non-steady-state detonation wave before entering the fire-blocking section.

[0016] The structure and material of the intermediate pipeline are exactly the same as those of the upstream pre-test pipeline and the downstream pipeline, except that the length is shorter. The length of the intermediate pipeline can be appropriately increased or shortened during pipeline processing before the test, depending on the different initial working conditions such as the test gas composition or gas equivalence ratio, which leads to different non-steady-state detonation run-up distances. Ultimately, it is ensured that before the fire-blocking effect test of the fire-blocking section is carried out, the sum of the lengths of the upstream segmented combined pipeline, the initial expansion joint and the intermediate pipeline is equal to the run-up distance obtained in the pre-test. During the fire-blocking effect test, the expansion joint is fine-tuned according to the actual situation to ensure that the non-steady-state detonation occurs directly in front of the fire-blocking section.

[0017] The test and data acquisition system includes a high-frequency dynamic pressure sensor, a photodiode and a data acquisition instrument; a group of high-frequency dynamic pressure sensors and photodiodes are arranged at a certain distance on the center lines of the upper and lower walls of the upstream pre-test pipeline and the upstream segmented combined pipeline according to the length of the pipeline. The pressure sensor is used to record the pressure changes in the pipeline and monitor the formation and development of the detonation wave. The sensing part of the pressure sensor converts the pressure signal into a weak charge with extremely high output impedance, and then converts this weak charge into a voltage proportional to it through an adapted charge amplifier, and converts the high output impedance into a low output impedance. The charge amplifier is then connected to the dynamic data acquisition system. The selected data acquisition system must have a high sampling frequency and multiple input units to capture the extremely fast-propagating deflagration flame and detonation wave, and realize the synchronous acquisition of multiple signals at the same time. The photodiode is a semiconductor device composed of a PN junction, which has a unidirectional conductive characteristic. The change of light causes the change of the photodiode current. The greater the intensity of the light, the greater the reverse current, and the optical signal can be converted into an electrical signal to become a photoelectric sensor. The photodiode is directly connected to the data acquisition instrument, and the position of the flame and detonation wave in the pipeline can be detected by the change of signal intensity. Ensure that a set of pressure sensors and photodiodes are installed on the upper and lower walls of the intermediate pipeline adjacent to the fire-blocking section to detect the pressure and light intensity when the overdriven detonation wave is formed. At the same time, a set of pressure sensors and photodiodes are also installed on the upper and lower walls of the downstream pipeline adjacent to the intermediate fire-blocking section to detect the pressure and light signals in the pipeline behind the fire-blocking section, and combined with the schlieren images in the fire-blocking section and the downstream pipeline taken by the high-speed schlieren camera system, the visualization of the detonation blocking and subsequent processes is realized, so as to judge whether the non-steady-state detonation wave is completely blocked by the fire-blocking section. If the pressure and light signal curves obtained by the data acquisition instrument in the downstream pipeline have no sudden changes and no flame is observed in the downstream pipeline in the schlieren image, it means that the non-steady-state detonation wave has been completely blocked by the fire-blocking section. If, according to the test number (13) consecutive tests specified in the national standard, there are no sudden changes in the pressure and light signal curves in the results of repeated tests (GB / T13347-2010), and no obvious detonation reaction front or flame is observed in the schlieren image, it means that the fire-blocking section has excellent performance and can effectively block the non-steady-state detonation; if there is a sudden change in the curve or an obvious detonation reaction front or flame is observed in the schlieren image in one of the 13 consecutive tests, it means that the non-steady-state detonation is not effectively blocked by the fire-blocking section, and the fire-blocking performance of the fire-blocking section is considered to be unqualified. The performance of the fire-blocking section can be optimized by changing the fire-blocking core material or the structure of the fire-blocking section, thereby providing a practical solution for the further development of high-efficiency non-steady-state detonation flame arresters.

[0018] The high-voltage ignition and synchronous control system mainly includes a high-voltage igniter, an ignition electrode, an ignition energy oscilloscope, an adapted high-voltage probe and current probe, a synchronous controller and an ignition switch. The high-voltage igniter is a high-voltage pulse generator that realizes ignition through capacitor energy storage discharge, and the high voltage range is 5000-15000V. The ignition electrodes are arranged in pairs near the left end wall of the upstream pre-test pipeline and the first section of the upstream segmented combined pipeline. The ignition position of the ignition electrode is located at the center line of the upstream pipeline and the downstream pipeline. The ignition position can be changed along the center line according to the test requirements, so as to study the characteristics and laws of the transformation process of the premixed gas from deflagration to detonation under the influence of different ignition positions. The ignition electrode discharge trigger is realized by the synchronous controller, and the premixed gas is ignited by the high-voltage electric spark generated by the instantaneous discharge of the tip. During the instantaneous ignition process, by connecting the appropriate high-voltage probe and current probe to the ignition electrode end exposed on the outer side of the upper and lower walls of the pipeline, the voltage and current data of the ignition spark of the ignition device are captured in real time and fed back to the oscilloscope. Through the internal mathematical calculation of the oscilloscope, the energy value of the ignition spark of the ignition device is obtained. Different ignition energies can be generated by setting different capacitance and voltage values ​​in the high-voltage igniter, thereby determining different ignition capabilities for premixed combustible gases. During the test, the programmable synchronous controller is used to achieve synchronous control and synchronous triggering of the high-voltage ignition system, high-speed camera and data acquisition system.

[0019] The synchronous controller mainly consists of two parts: CPU and control panel. Three terminals, high-voltage igniter, high-speed camera and data acquisition instrument, are connected to the synchronous controller at the same time. The core component CPU accurately controls the trigger time of each terminal by setting and storing the trigger sequence and time interval of each component. In addition, it is necessary to configure a separate power supply for each terminal and set a different working voltage. The ignition switch is connected to the synchronous controller as the final trigger device of each system.

[0020] The working process of the test device is as follows:

[0021] (I) Pre-test process

[0022] (1) Adjust the laboratory temperature to the initial temperature required for the test;

[0023] (2) Install and debug the test equipment, connect the upstream pre-test pipeline, the non-steady-state detonation fire arrester section and the downstream pipeline required for the pre-test, and ensure that all test systems (automatic gas distribution system, test and data acquisition system, Schlieren camera system, high-voltage ignition and synchronization control system) are in good condition and work properly;

[0024] (3) Turn on each test device and preheat for 30 minutes;

[0025] (4) At the same time, use a vacuum pump to evacuate the combustion pipeline, and then check the air tightness of the pipeline to ensure that the pipeline is in good air tightness;

[0026] (5) Open the air intake valve of the combustion pipeline and the exhaust pipe on the rightmost lower wall. The combustible premixed gas of the target concentration configured by the automatic gas distribution system is delivered into the combustion pipeline through the air intake pipe, and other gases or impurities in the pipe are discharged from the exhaust pipe by the displacement method. When the gas distribution system software shows that the gas concentration has reached the target concentration and the concentration value is stable, stop the gas distribution and complete the gas distribution and inflation work;

[0027] (6) Close the air inlet valve and air outlet valve of the combustion pipeline and wait for about 30 seconds to ensure that the combustible gas mixture is in a stable and uniform mixing state;

[0028] (7) Turn on the high-voltage ignition system and set the ignition voltage of the high-voltage ignition system to the target value;

[0029] (8) Turn on and adjust the high-voltage probe, current probe, ignition energy oscilloscope, data acquisition instrument, high-speed camera and synchronization controller to the trigger state;

[0030] (9) After the preparation is completed, press the ignition switch connected to the synchronous controller to start the high-voltage ignition system, realize ignition in the tube through discharge at the tip of the ignition electrode, and obtain the energy value of the instantaneous discharge through each probe and the ignition energy oscilloscope. At the same time, trigger the high-speed camera and data acquisition instrument in sequence according to the preset time to shoot the flame acceleration and the process of deflagration to detonation, and measure the dynamic changes of the pressure and light intensity in the tube;

[0031] (10) After a flame acceleration and deflagration-to-detonation test is completed, the image data of the high-speed camera and the pressure and light signal data recorded by the data acquisition instrument are stored in the target memory card to prepare for subsequent data processing and analysis;

[0032] (11) Clean the combustion pipe, reset each test device, and prepare to start the next set of repeated tests;

[0033] (12) Under the same test conditions, including the same combustible premixed gas composition and equivalence ratio, at least 13 repeated tests are carried out to study the characteristics of the deflagration-to-detonation process, and the run-up distance from deflagration to detonation of each group is obtained by analyzing the image data of the high-speed camera and the pressure and light signal data recorded by the data acquisition instrument. The error is reduced by taking the average value, and finally a fixed run-up distance from deflagration to detonation under the test conditions is obtained;

[0034] (13) In addition to being used to obtain the run-up distance, after performing repeated tests under the same working conditions of step (12), the working conditions can also be changed, such as changing the composition of the combustible gas by connecting different air intake cylinders, changing the equivalence ratio of the combustible gas by setting the parameters of the gas distribution system software, changing the ignition position by setting different hole installation positions of the ignition electrode, changing the ignition energy output by the ignition electrode by setting the ignition voltage of the high-voltage igniter, and changing the blockage rate of the pipeline (i.e., the ratio of the obstacle height to the pipeline height in the same longitudinal section) by setting triangular obstacles of different heights. Repeated tests are carried out in each group to further study the characteristics and laws of the process of transformation from deflagration to detonation of premixed gas under the influence of factors such as different combustible gas components, premixed gases of different equivalence ratios, different ignition positions, different ignition energies, and different pipeline blockage rates.

[0035] (II) Test process of fire-blocking effect of non-steady-state detonation fire-blocking section

[0036] (A) According to the run-up distance obtained in step (12) of the pre-test test process, the number of sections of the upstream segmented combined pipeline is selected so that the sum of the lengths of the upstream segmented combined pipeline, the expansion joint and the intermediate pipeline is the length of the run-up distance, the starting end of the fire-blocking section is connected to the rear of the intermediate pipeline, and the end is connected to the front of the downstream pipeline, and then steps (3)-(11) in the pre-test test are repeated, and the occurrence position of the non-steady-state detonation is observed and judged by the schlieren image taken by the high-speed camera and the pressure and light signal intensity obtained by the pressure sensor and the photodiode. If the occurrence position of the non-steady-state detonation is advanced, the length of the expansion joint is shortened; if the occurrence position of the non-steady-state detonation is delayed, the length of the expansion joint is extended to ensure that the non-steady-state detonation occurs in front of the fire-blocking section;

[0037] (B) After a test of the fire-blocking effect of a non-steady-state detonation fire-blocking section is completed, the image data of the high-speed camera and the pressure signal and light signal data recorded by the data acquisition instrument are stored, and the process of the fire-blocking section blocking the non-steady-state detonation wave is studied through the schlieren image taken by the high-speed camera. At the same time, the schlieren image can also be used to observe whether there is an obvious flame in the downstream pipeline. Then, a group of pressure sensors and photodiodes on the upper and lower walls of the downstream pipeline close to the fire-blocking section and the high-speed schlieren image are combined to judge the blocking effect of the fire-blocking section on the non-steady-state detonation wave. If the pressure sensor and the photodiode do not detect a sudden change signal in the results of repeated tests (GB / T13347-2010) according to the test number specified in the national standard (13) consecutive tests, and no obvious detonation reaction front or flame is observed in the schlieren image, it means that the fire-blocking section has excellent performance and can effectively block the non-steady-state detonation; if there is a sudden change in the curve or an obvious detonation reaction front or flame is observed in the schlieren image in one of the 13 consecutive tests, it means that the non-steady-state detonation is not effectively blocked by the fire-blocking section, and the fire-blocking performance of the fire-blocking section is considered to be unqualified. The performance of the fire-blocking section can be optimized by changing the fire-blocking core material or the structure of the fire-blocking section, thereby providing a practical solution for the further development of high-efficiency non-steady-state detonation flame arresters.

[0038] The advantages of the present invention compared with the prior art are:

[0039] 1. The present invention provides a technology and device that can accurately test the effect of a non-steady-state detonation flame arrester for combustible gas, overcoming the difficulty in testing the non-steady-state detonation flame arrester effect. The device can study the characteristics of the deflagration-to-detonation process and the flame arresting effect of a non-steady-state detonation flame arrester under conditions of different combustible gas components, premixed gases of different equivalence ratios, different ignition positions, different ignition energies, obstacles of different heights (different blocking rates), etc., and can record important characteristic parameters in the process of non-steady-state detonation formation, and can artificially control the test environment and test conditions.

[0040] 2. The present invention adopts a method combining high-speed camera technology and Schlieren optical technology to capture and record the process of deflagration to detonation in the pipeline and the flame arrester fire blocking process, so as to realize the visualization of the whole process of non-steady-state detonation generation and blocking, and accurately and intuitively present the dynamic change law of the shape and position of the flame and detonation wave over time.

[0041] 3. The present invention uses a pressure sensor to measure the dynamic rise characteristics of the pressure in the pipeline, and can combine high-speed schlieren images to analyze the relationship between the pressure in the pipeline and the flame and detonation wave characteristics. The light intensity changes in the pipeline are detected by a photodiode to obtain the position changes of the initial flame and the later detonation wave, and the propagation speed of the flame and detonation wave at each moment can be calculated in combination with high-speed schlieren image analysis. The device can be used to carry out many studies on the process of deflagration to detonation, such as the premixed flame acceleration of different types of test gases and the speed change and pressure increase characteristics during the process of deflagration to detonation. It can also be used to study the effects of mixed gases with different equivalence ratios, different ignition positions, different ignition energies and obstacles of different heights on flame acceleration and deflagration to detonation characteristics.

[0042] 4. The present invention adopts an adjustable pipeline structure formed by combining three parts: an upstream segmented combined pipeline, an expansion joint, and an intermediate pipeline. The expansion joint is a specially made small section of pipeline whose length can be adjusted within the range of expansion and contraction. It is mainly used to compensate for the change in the location of the non-steady-state detonation caused by the change in pipeline length and its own influence on the flow field. After the upstream pre-test pipeline is replaced with the combination structure of the upstream segmented combined pipeline, the expansion joint, and the intermediate pipeline, the position of the deflagration-to-detonation transition (i.e., the position where the non-steady-state detonation occurs) may be slightly advanced or delayed relative to the pre-test. Therefore, it is necessary to connect an expansion joint in the pipeline. If the position of the deflagration-to-detonation transition is advanced, this small section of the expansion joint is shortened; if the position of the deflagration-to-detonation transition is delayed, this small section of the expansion joint is extended. Therefore, on the basis of ensuring that other parts of the pipeline remain unchanged, the location of the non-steady-state detonation is controlled at the run-up distance to ensure that the non-steady-state detonation wave enters the fire-blocking section.

[0043] 5. The present invention installs fire-blocking cores of different types of flame arresters in the middle of the upstream and downstream pipelines of the non-steady-state detonation blocking test combustion pipeline, and then fixes them through stainless steel shells as different fire-blocking sections, to study the changes in the propagation speed, light intensity change, pressure rise and other characteristics of the non-steady-state detonation wave under the action of these fire-blocking sections; revealing the blocking effects of various fire-blocking cores such as corrugated plates, foam metals and filled gravel on non-steady-state detonation. In addition to changing the fire-blocking core material, the structure of the fire-blocking section can also be changed to ensure accurate testing of the blocking effects of fire-blocking sections of different structures on non-steady-state detonation. On the basis of small-scale laboratory tests, the size of the test device can be increased as a whole, and then larger industrial flame arresters can be connected to accurately test the fire-blocking effect of non-steady-state detonation flame arresters used in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of a visual test device for accurately testing the effect of a non-steady-state detonation flame arrester of a combustible gas according to the present invention;

[0045] Figure 2It is a schematic diagram of the internal structure of the high-precision automatic gas distribution system of the present invention; in the figure, MFC is a high-precision mass flow meter.

[0046] Figure 3 This is a schematic diagram of the combustion pipeline used in the test of the fire-blocking effect of the non-steady-state detonation fire-blocking section;

[0047] Figure 4 Schematic diagram of industrial non-steady-state detonation flame arrester.

[0048] Explanation of the accompanying drawings: Taking the pipeline connection during the pre-test test as an example, in the figure, 1-high-voltage igniter, 2-ignition energy oscilloscope, 3-current probe, 4-high-voltage probe, 5-ignition electrode, 6-vacuum pressure gauge, 7-upstream pre-test pipeline, 8-pressure sensor, 9-unsteady-state detonation fire-blocking section, 10-downstream pipeline, 11-vacuum pump, 12-first Schlieren reflection concave mirror, 13-slit, 14-focusing lens, 15-Schlieren light source, 16-automatic gas distribution system, 17-insulating valve, 18-photodiode, 19-exhaust pipeline, 20-pressure relief port, 21-synchronous controller, 22-high-speed camera, 23-Schlieren knife edge, 24-second Schlieren reflection concave mirror, 25-data acquisition instrument, 26-charge amplifier. It should be noted that the diameters of the first Schlieren reflection concave mirror 12 and the second Schlieren reflection concave mirror 24 can be increased or decreased in actual applications according to the length of the pipeline. The figure is only a schematic diagram of the structure, 27-upstream segmented combined pipeline, 28-expansion joint, 29-intermediate pipeline, 30-flame arrester core; 31-industrial non-steady-state detonation flame arrester. DETAILED DESCRIPTION

[0049] The following is an explanation of the embodiments of the present invention in conjunction with the accompanying drawings. Hydrogen and oxygen premixed gas is a common industrial pipeline transport gas, and the velocity and pressure of the detonation wave generated when it detonates are greater than those of other premixed gases, so the requirements for hydrogen and oxygen premixed gas non-steady-state detonation flame arresters are also higher. The following will take the deflagration to detonation test of hydrogen and oxygen premixed gas with an equivalence ratio of 1 in a 3mm high triangular obstacle pipeline in the laboratory as an example to design the parameters such as the size of each part.

[0050] The present invention discloses a visual test device for accurately testing the effect of a combustible gas non-steady-state detonation flame arrester. The device mainly comprises a high-voltage igniter 1, an ignition energy oscilloscope 2, a current probe 3, a high-voltage probe 4, an ignition electrode 5, a vacuum pressure gauge 6, an upstream pre-test pipeline 7, a pressure sensor 8, a non-steady-state detonation flame arrester section 9, a downstream pipeline 10, a vacuum pump 11, a first schlieren reflection concave mirror 12, a second schlieren reflection concave mirror 24, a slit 13, a focusing lens 14, a schlieren light source 15, an automatic gas distribution system 16, an insulating valve 17, a photodiode 18, an exhaust pipeline 19, a pressure relief port 20, a synchronous controller 21, a high-speed camera 22, a schlieren blade 23, a data acquisition instrument 25, a charge amplifier 26, an upstream segmented combined pipeline 27, an expansion joint 28, an intermediate pipeline 29, a flame arrester core 30 and an industrial non-steady-state detonation flame arrester 31.

[0051] The definition of directions in the embodiment of the present invention is as follows: in the longitudinal direction of the entire device, the end close to the insulating valve 17 is defined as the front end, and the end close to the pressure relief port 20 is defined as the rear end, or the end; looking at the front end direction from the rear end, the left hand direction is the left side, and the right hand direction is the right side;

[0052] The vacuum pump 11 is a 2XZ type rotary vane vacuum pump, i.e. a two-stage high-speed direct-connected structure rotary vane vacuum pump, which is connected to the pressure relief port 20 at the right end of the downstream pipeline 10 through a connecting pipeline. Before the test, the combustion pipeline is evacuated to a vacuum state in preparation for filling with combustible premixed gas. The vacuum pressure gauge 6 is an OMEGA DPG4000-30A ultra-high precision digital pressure gauge with a range of 0-30psi, a withstand pressure of 60psi, a burst pressure of 500psi, and an accuracy of ±0.05% of the full scale (positive pressure). It is connected to the upper wall of the upstream combustion pipeline and is used to synchronously monitor the vacuum degree in the pipeline. When the reading of the vacuum pressure gauge is equal to zero (or approximately zero, related to the local atmospheric pressure) and remains stable for a period of time, it indicates that the vacuum state has been reached in the pipeline.

[0053] The automatic gas distribution system 16 is controlled by the computer of the control platform. During the test, the computer is turned on and the gas distribution system software is run. By inputting the target concentration parameters, the combustible gas and the combustion-supporting gas in the raw gas cylinder of a certain equivalent ratio are transported into the gas distribution box. The gas distribution box is composed of a high-precision mass flow meter (MFC), a gas mixing chamber, an electromagnetic stop valve and a connecting circuit. The flow of the component gas is controlled by real-time monitoring of the MFC, thereby realizing dynamic gas distribution automation. The automatic gas distribution system 16 is connected to the insulated air intake valve 17 at the front end of the upstream pipeline of the combustion pipeline through the total gas transmission pipeline output by the gas mixing chamber in the box, and is used to fill the premixed gas of a certain equivalent ratio into the combustion pipeline until the internal pressure of the pipeline is stabilized to one atmospheric pressure, and the air intake valve is closed.

[0054] The Schlieren camera system includes a pair of Schlieren reflection concave mirrors, namely, a first Schlieren reflection concave mirror 12 and a second Schlieren reflection concave mirror 24 (the first Schlieren reflection concave mirror 12 and the second Schlieren reflection concave mirror 24 are actually located in the same horizontal direction, and are arranged on the left and right sides of the combustion pipe respectively), a high-speed camera 22, a Schlieren knife edge 23, a slit 13, a focusing lens 14 and a Schlieren light source 15. The Schlieren optical system adopts a standard "Z"-shaped optical path arrangement, and the two reflection concave mirrors, namely, the first Schlieren reflection concave mirror 12, the second Schlieren reflection concave mirror 24 and the focusing lens 14 are adjusted to be consistent with the center height of the Schlieren knife edge 23 and the slit 13, and the combustion pipe is placed in the center of the optical path. The Schlieren light source 15 is an iodine tungsten lamp; the mirror diameter of the two reflecting concave mirrors 12 and 24 is 300mm, and the focal length is 2000mm; the adjustment range of the knife edge 23 is 0-10mm, the minimum reading value is 0.01mm, and the adjustment angle is 360°; the adjustment range of the slit 13 is 0-3mm, the minimum reading value is 0.01mm, and the adjustment angle is 360°; the high-speed camera 22 uses a high-performance high-speed camera (such as Photron FASTCAM SAZ 2100K), the shooting speed is set to 200000-500000fps, and the high-speed camera 22 is triggered and started by the synchronous controller 21. During the test, the light emitted by the Schlieren light source 15 passes through the focusing lens 14, so that the filament is imaged on the slit 13. A point light source is formed at the position of the slit 13. The light of the point light source forms a beam of parallel light after passing through the first schlieren reflection concave mirror 12. The light beam passes through the quartz glass side wall of the combustion pipe, and then is reflected by the second schlieren reflection concave mirror 24, and is cut by the schlieren knife edge 23, and finally enters the high-speed camera 22 through the focusing lens. In the experiment, the schlieren and high-speed camera are combined to study the dynamic characteristics of the flame in the early stage of combustion wave propagation and the detonation wave in the later stage. The schlieren images taken by the high-speed camera intuitively show the dynamic change process of the flame and detonation wave shape and the relationship between the change of the position of the flame and the detonation wave front with time. At the same time, it is also of great significance to analyze the blocking process of the flame arrester core 30 in the non-steady-state detonation fire arrester section 9 for the non-steady-state detonation wave. In addition, the schlieren images can also be used to calculate the propagation speed of the flame and the detonation wave. The binary image of the flame or detonation wave is obtained by reading the schlieren image through software such as Matlab, and then the pixel x coordinate sequence of the corresponding front is read, so as to calculate the number of pixels moved by the flame or detonation wave front within a certain period of time. Then, the actual length corresponding to the pixel value of the Schlieren image is obtained according to the measured results. For example, a pixel in the Schlieren image corresponds to an actual length of b meters. The flame or detonation wave front speed can be calculated as follows:

[0055]

[0056] Where v is the flame front velocity (m / s), x is the pixel difference between the flame or detonation wave front positions in two adjacent schlieren images, and f is the shooting speed set by the high-speed camera (fps).

[0057] During the pre-test test in this experiment, the combustion pipe used was a horizontally placed rectangular cross-section straight pipe with an external dimension of 70mm×70mm×340mm and an internal dimension of 20mm×20mm×300mm. The pipe consists of three parts: the upstream pre-test pipe 7, the non-steady-state detonation fire arrester section 9 and the downstream pipe 10. The lengths of the three pipe parts during the pre-test in this experiment were 166mm, 40mm and 94mm respectively. The upper and lower walls and the front and rear end walls of the three pipe parts were made of 25mm thick 304 stainless steel. Continuous isosceles triangle obstacles were symmetrically arranged on the upper and lower stainless steel walls of the upstream pre-test pipe 7 and the downstream pipe 10. The bottom side length of a single obstacle was 5.8mm and the height was 3mm. The obstacle was a solid obstacle made of 304 stainless steel and was processed as one piece with the pipe wall. Optical glass was installed on the left and right sides of the three pipe parts. The glass material was optical quartz glass with a thickness of 25mm. It had good optical properties and was suitable for taking clear Schlieren images. A pair of ignition electrodes 5 are installed on the upper and lower walls of the combustion pipeline 26mm away from the front end outer wall, that is, 6mm away from the inner wall, to ignite the premixed gas filled in the tube through the electric spark at the tip of the electrode. According to the relevant requirements of the national petroleum gas pipeline flame arrester standard GB / T 13347-2010, a pair of pressure sensors 8 and photodiodes 18 are installed on the upper and lower walls of the upstream pre-test pipeline 7 every 80mm to detect the real-time pressure and light signal in the tube at the same distance. At the same time, the pressure sensor spacing is set to 80mm, which can also meet the requirement of having a pair of pressure sensors 8 and photodiodes 18 on the upper and lower walls at the end of the upstream pre-test pipeline to accurately measure the pressure and light signal of the combustion wave before entering the non-steady-state detonation flame arrester section 9. The non-steady-state detonation flame arrester section 9 is 40mm long and consists of a flame arrester core 30, optical quartz glass and a stainless steel shell. The fire-blocking core 30 uses a corrugated plate fire-blocking core corresponding to a commonly used corrugated plate detonation-blocking flame arrester, and then studies its fire-blocking effect. It can also be replaced with a fire-blocking core corresponding to other common detonation-blocking flame arresters, such as a foam metal flame arrester, a filling gravel, etc., and then compares and studies the fire-blocking effect of other fire-blocking cores. Optical quartz glass is installed on the left and right sides of the fire-blocking section. The internal fire-blocking section is observed through the quartz glass visual window and the blocking process of the non-steady-state detonation in the fire-blocking section is photographed. The stainless steel shell is used to fix the internal fire-blocking core and dock with the external pipeline. In addition to changing the fire-blocking core material, the existing fire-blocking section can also be replaced with other fire-blocking devices with different structures to ensure accurate testing of the blocking effect of fire-blocking devices with different structures on non-steady-state detonation. In order to ensure that the test device is indeed effective in the actual industrial process, on the basis of the small-scale laboratory test, the size of the test device can be increased as a whole, and then the larger industrial non-steady-state detonation flame arrester 31 can be connected, so as to accurately test the fire-blocking effect of the non-steady-state detonation flame arrester used in industry.The downstream pipeline 10 is a protective side pipe section, which is used to release pressure and discharge exhaust gas. The length of the downstream pipeline 10 is 94mm, which meets the relevant requirements of the national petroleum gas pipeline flame arrester standard GB / T13347-2010. A pair of pressure sensors 8 and photodiodes 18 are installed on the upper and lower walls of the starting end of the downstream pipeline 10 adjacent to the flame arrester section to detect the pressure and light intensity of the airflow in the pipeline after the flame arrester section, combined with the schlieren picture taken by the high-speed camera, as an important basis for judging the detonation resistance effect of the flame arrester section. A 20mm×20mm pressure relief port 20 is arranged at the very end of the downstream pipeline 10 as a cover for installing a valve. The valve is opened instantly during the test. After the combustion products pass through the valve, the exhaust gas is discharged to the outside through the smoke foil pipe connected to the outside to ensure that there is no gas accumulation indoors. An exhaust pipeline 19 is arranged near the very end of the lower side wall. When the automatic gas distribution system 16 is used to fill the pipe, the valve of the exhaust pipeline is opened to ensure smooth gas flow to ensure the safety of the test. Under this test condition, through more than three repeated preliminary tests, the run-up distance for the occurrence of unsteady-state detonation was found to be 145 mm.

[0058] In the test of the fire-blocking effect of the unsteady-state detonation fire-blocking section in this experiment, the combustion pipeline used is composed of five parts, namely, the upstream segmented combined pipeline 27, the expansion joint 28, the intermediate pipeline 29, the unsteady-state detonation fire-blocking section 9 and the downstream pipeline 10, and the unsteady-state detonation fire-blocking section 9 contains different types of fire-blocking cores 30. Among them, the upstream segmented combined pipeline 27 is spliced ​​by multiple sections of pipelines, which is used to select different sections to connect according to the pre-test results, so as to flexibly change the length of the upstream pipeline. Each section of the upstream segmented combined pipeline is similar to the structure and material of the upstream pre-test pipeline. The upper and lower walls and the front and rear end walls are also made of 25mm thick 304 stainless steel. The upper and lower stainless steel walls are symmetrically arranged with continuous isosceles triangle obstacles. The base length of a single obstacle is 5.8mm and the height is 3mm. The obstacle is a solid obstacle made of 304 stainless steel and is processed as one with the pipeline wall. Optical quartz glass with a thickness of 25mm is also installed on the front and rear sides of the pipeline. A pair of ignition electrodes 5 are installed on the upper and lower walls at a distance of 26mm from the front end outer wall, that is, 6mm from the inner wall, to ignite the premixed gas filled in the tube through the electric spark at the tip of the electrode. The initial state (not extended or shortened) length of the expansion joint 28 is 20mm, and the adjustable length range of the rotating nut is ±10mm. The structure and material of the expansion joint are slightly different from those of the upstream and downstream pipelines. In order to achieve effective expansion and contraction and ensure the compressive strength of the structure, the left and right walls of the expansion joint do not use optical quartz glass, but are provided with a stainless steel shell. The overall expansion joint is made of all stainless steel. The material and internal structure of the intermediate pipe are the same as those of each section of the upstream segmented combined pipe, and the length is 40mm. The upstream segmented combined pipe is composed of multiple sections. The upstream segmented combined pipe is pre-processed. The specific number of sections can be selected according to actual needs. Generally, 6-7 sections can be processed in advance. Except for the first section, which has a length of 26mm due to the need to set the ignition electrode 6mm away from the front inner wall, the other sections are all 20mm. In the laboratory test of deflagration-to-detonation conversion of hydrogen-oxygen premixed gas with an equivalence ratio of 1 in a triangular obstacle pipe with a height of 3mm, the pre-test results show that the run-up distance for non-steady-state detonation is 145mm. Therefore, only 4 sections of upstream segmented combined pipes are needed, namely the first section of 26mm plus the last three sections of 20mm each. At this time, the total length of the upstream segmented combined pipe is 86mm, plus the initial expansion joint length of 20mm and the middle pipe length of 40mm, so that the pipe length before the fire-blocking section is 146mm, close to the run-up distance of 145mm, and then the expansion joint length is shortened by 1mm, and finally the pipe length before the fire-blocking section is the run-up distance length.It should be noted that the structure of the expansion joint is slightly different from that of the upstream and downstream pipelines. In order to achieve effective expansion and contraction and ensure the compressive strength of the structure, the left and right walls of the expansion joint are not made of optical quartz glass, but stainless steel. The difference in structure and material may have a slight effect on the flow field in the pipeline, and the run-up distance may increase or decrease slightly around 145mm. In the test, the length of the expansion joint can be fine-tuned according to the location of the unsteady-state detonation observed in the actual schlieren image, so that the sum of the lengths of the upstream segmented combined pipeline, the expansion joint and the intermediate pipeline is the length of the run-up distance, ensuring that the unsteady-state detonation occurs just in front of the fire arrester section, thereby accurately testing the detonation-blocking effect of the unsteady-state detonation fire arrester section or the flame arrester for industrial applications.

[0059] The pressure in this test device is measured by a pressure sensor 8. Considering that the propagation of premixed flames and detonation waves is a very rapid process, accompanied by instantaneous high temperature and high pressure, the pressure sensor 8 needs to be a high-frequency dynamic pressure sensor with extremely fast response speed and high instantaneous high temperature tolerance. The PCB 112A05 piezoelectric quartz pressure sensor is selected in this device, with a maximum range of 34475kPa, a response frequency ≥200kHz, a charge sensitivity of 151.0pC / MPa, and a maximum instantaneous temperature of 1649℃. The pressure sensor is connected to a charge amplifier 26 to convert the weak charge output by the pressure sensor into a voltage proportional to it, and to convert the high output impedance into a low output impedance. The YE5852B charge amplifier is selected in this device, which has dual channels and a maximum input charge of ±10 6 Pc, sensitivity 0.01-1000mV / Pc, low noise less than 5μV. The charge amplifier needs to be preheated for 30 minutes before the test. Photodiode 18 uses SM05PD2A type packaged silicon photodiode, and the measurement spectrum range is 200-1100nm. The charge amplifier and the photodiode are both connected to the data acquisition instrument 25, so as to record the dynamic changes of pressure and light intensity in the pipeline over time during the combustion process. The time and position of the occurrence of deflagration to detonation, that is, the formation time and position of non-steady-state detonation, can also be determined by the changes in pressure and light intensity. The pressure and light intensity curves of the entire combustion process output by the data acquisition instrument will have a sharp jump when the deflagration turns to detonation. The data acquisition instrument is a HIOKI 8826 dynamic data acquisition instrument. The data acquisition instrument provides a variety of input units, with a total of 32 channels, which can simultaneously collect various types of signals, and the maximum waveform sampling rate of each channel is 1Ms / s.

[0060] The high-voltage igniter 1 is connected to the synchronous controller 21 and two ignition electrodes 5 installed near the upper and lower walls of the upstream pre-test pipeline 7 or the first section of the upstream segmented combined pipeline 27 through wires. The 2002-1 type synchronous high-voltage pulse generator is selected in this test device, and the capacitor is charged by alternating current during the test. The ignition electrode is installed 6mm away from the left end wall of the pipeline, and its ignition position is on the center line of the pipeline. Its position can also be changed according to the test requirements, so as to study the characteristics and laws of the transformation process from deflagration to detonation of the premixed gas under the influence of different ignition positions. The ignition electrode discharge trigger is realized by the synchronous controller 21. During the discharge process, the transformer will increase the voltage at a ratio of 1:50, and realize instantaneous discharge through the ignition electrode, generating a high-voltage electric spark at the tip of the ignition electrode to ignite the premixed combustible gas. Different capacitances and different voltages will produce different ignition energies, and different ignition energies determine the different ignition capabilities of the spark to the premixed gas. The ignition energy generally occupies a certain proportion in the total reserve energy, and the total reserve energy can be calculated according to the following formula:

[0061]

[0062] In the formula, E is the total reserve energy (J), C is the capacitance (μF), and V is the voltage (V). The voltage can be adjusted as required. In the test, C is 200μF. When V is 100V, the total reserve energy of the ignition electrode is calculated to be 1J by formula (2). The energy released from the tip of the actual ignition electrode is generally less than the total reserve energy. In order to accurately measure the ignition energy of the high-voltage igniter, the ignition energy oscilloscope 2 can be used with the appropriate current probe 3 and the high-voltage probe 4 to feed back the collected data of the voltage and current values ​​of the ignition spark of the ignition device to the oscilloscope. Through the internal calculation of the oscilloscope, the ignition spark energy value of the ignition device is obtained. In this test device, a Keysight InfiniiVision DSOX3024T oscilloscope is selected, with a bandwidth of 200MHz. The calculated rise time is less than or equal to 1.75ns. There are 4 channels in total, the maximum sampling rate of all channels is 5GSa / s, the maximum storage depth is 4Mpts as standard, and the waveform capture rate is greater than 1 million waveforms / second. The current probe uses the Keysight CP8500A current probe with a maximum bandwidth of 12MHz, a rise time of less than or equal to 29ns, a maximum continuous current of 150Arms, and a peak current of 300A. The high-voltage probe uses the Keysight DP6700A high-voltage differential probe with a maximum bandwidth of 100MHz, a rise time of less than or equal to 3.5ns, an accuracy of ±2%, and a range selection (attenuation ratio) of 100X / 1000X. Set the oscilloscope horizontal scale unit to 1μs to ensure that the oscilloscope captures a single spark. The high-voltage probe and current probe are connected to channels 1 and 2 of the oscilloscope respectively, set the test voltage value of channel 1, set the test current value of channel 2, and adjust the attenuation ratio of the voltage and current probes to ×1000. Before the test, the positive and negative poles of the high-voltage probe test end are connected to the ignition electrode discharge positive pole and the shell (ground) respectively, to collect the discharge voltage when the ignition device is discharged. Then disconnect the ignition cable from the ignition electrode needle, and prepare two wires, the first of which connects the inner core of the ignition cable and the electrode, and the second connects the metal shells of the two. Load the current probe to the first wire according to its test method to collect the output current of the ignition device. During the test, adjust the oscilloscope, add measurement channels 1, 2 and M (M is the oscilloscope mathematical calculation waveform), select the maximum value for the test type of measurement channels 1 and 2, and select the area for the test type of M. In the mathematical function of the oscilloscope, set the mathematical expression ①×② (① is channel 1, ② is channel 2), and the mathematical waveform displays the value of a single spark energy value. If the value corresponding to ① is A and the value corresponding to ② is B, then the value of A×B is the ignition energy value.

[0063] During the test, the high-speed camera 22, the high-voltage electric ignition device 1 and the data acquisition device 25 are synchronously controlled and triggered simultaneously by the synchronous controller 21. This device uses an OMRON SK20 programmable synchronous controller (PLC), which mainly includes two parts: a CPU and a control panel. It can connect multiple terminals at the same time, and the CPU can accurately control the trigger time of each terminal by inputting and storing the trigger sequence and time interval of each terminal. Usually, it is necessary to configure a power supply for each terminal separately and set different working voltages. In this test, the high-speed camera 22, the high-voltage electric ignition device 1 and the data acquisition device 25 require 3.3V, 5V and 3.3V DC voltages respectively, and the synchronous controller 21 itself requires 24V DC voltage.

[0064] The pressure resistance, flow resistance and other designs in this test all meet the relevant requirements of the national petroleum gas pipeline flame arrester standard GB / T13347-2010.

[0065] Parts of the present invention that are not disclosed in detail belong to the common knowledge in the art.

[0066] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A visual test device for accurately testing the effect of a combustible gas unsteady-state detonation flame arrester, characterized in that: Including vacuum system, automatic gas distribution system, Schlieren camera system, non-steady-state detonation blocking test combustion pipeline, test and data acquisition system, high-voltage ignition and synchronization control system; The vacuum system includes a vacuum pump and a vacuum pressure gauge, wherein the vacuum pump is used to extract air from the combustion pipeline to make the combustion pipeline reach a vacuum state; Automatic gas distribution system, used to configure combustible gas of target concentration. Multiple raw gas cylinders are connected to mass flow meters through electromagnetic stop valves. The electromagnetic stop valves are directly controlled by computers connected to the control platform. The gas in the raw gas cylinders passes through the electromagnetic stop valves and mass flow meters into the gas mixing chamber, and then is connected to the combustion pipeline intake valve through pipelines; The Schlieren imaging system includes a Schlieren instrument and a high-speed camera, and is arranged in a standard "Z" shape. The combustion pipeline is located in the central path of the optical path. The Schlieren instrument includes a Schlieren point light source, a focusing lens, a slit, a pair of reflecting concave mirrors and a Schlieren knife edge. The pair of reflecting concave mirrors are arranged on the left and right sides of the combustion pipeline. The Schlieren instrument is used to observe the density and temperature distribution of transparent media and the change of refractive index in the medium. When the premixed flame or detonation wave propagates in the combustion pipeline, there will be a density difference near the flame or the front of the reaction zone. When the light passes through the flow field, its direction, position and optical path will change. Therefore, the Schlieren instrument is used to capture The density discontinuity of the flow field will not interfere with the internal flow field. After the light emitted by the point light source of the Schlieren instrument passes through the focusing lens, the filament image is formed on the slit; the slit is adjusted to generate a divergent light beam, which is transmitted to the corresponding first reflecting concave mirror. The generated parallel light beam passes through the combustion pipe and is received by the second reflecting concave mirror on the other side to generate a converging light beam, which then enters the high-speed camera through the Schlieren knife edge and the focusing lens; the high-speed camera intuitively presents the flame evolution and the process of deflagration to detonation in the pipeline by recording the first-order derivative distribution image of the flow field density, and calculates the flame and detonation wave propagation speed through the photos taken by the high-speed camera; The non-steady-state detonation blocking test combustion pipeline is used to observe and determine the formation mode and position of non-steady-state detonation in the combustion pipeline. The non-steady-state detonation blocking test combustion pipeline is a horizontal rectangular cross-section straight pipeline, including six parts of the combustion pipeline, namely: upstream pre-test pipeline, upstream segmented combined pipeline, expansion joint, intermediate pipeline, non-steady-state detonation fire-blocking section and downstream pipeline. Among them, except for the expansion joint, the left and right walls of the remaining parts of the combustion pipeline are made of quartz glass, which is convenient for the high-speed Schlieren camera system to capture the Schlieren image in the pipeline, realize the visualization of the flame propagation process, the process of deflagration to detonation and the detonation blocking process, so as to determine the formation position of the non-steady-state detonation and observe the fire-blocking effect of the fire-blocking section. All upper and lower walls are made of stainless steel plates, and the front and rear walls are also made of stainless steel plates; except for the non-steady-state detonation fire-blocking section, the upper and lower walls of the other parts of the combustion pipeline are symmetrically arranged with continuous triangular obstacles made of stainless steel. The steady-state detonation fire-blocking section includes a fire-blocking core and a stainless steel shell. Optical glass is installed on the left and right sides of the unsteady-state detonation fire-blocking section to observe the blocking process of the unsteady-state detonation in the fire-blocking section. The stainless steel shell is used to fix the internal fire-blocking core and connect with the external pipeline. An exhaust pipeline is arranged on the lower side wall near the end of the downstream pipeline, and an insulating valve is arranged. It is opened when the combustion pipeline is inflated to ensure smooth air flow in the combustion pipeline and prevent gas congestion in the combustion pipeline from causing overpressure in the pipeline. A pressure relief port is arranged on the end wall of the downstream pipeline, and an insulating valve is arranged. It is opened when vacuuming to meet the vacuuming from the pressure relief port; it is closed when inflating to discharge the replaced air and excess mixed gas from the exhaust pipeline on the lower wall; it is opened during the test to discharge the combustion products and realize pressure relief, thereby ensuring the safety of the explosion-to-detonation test in the pipeline. An insulating valve is arranged on the front end wall of the upstream pre-test pipeline and the upstream segmented combined pipeline to control the start and end of the inflation process; A high-voltage ignition and synchronization control system, including a high-voltage igniter, an ignition electrode, an ignition energy oscilloscope, an adapted high-voltage probe and current probe, a synchronization controller and an ignition switch; the high-voltage igniter is a high-voltage pulse generator that realizes ignition through capacitor energy storage discharge, the ignition electrodes are arranged in pairs near the front end wall of the upstream pre-test pipeline or the first section of the upstream segmented combined pipeline, the ignition position of the ignition electrode is located at the center line of the upstream pipeline and the downstream pipeline, and the position can be adjusted along the center line, so as to study the characteristics and laws of the transformation process from deflagration to detonation of the premixed gas under the influence of different ignition positions; the synchronization controller includes a CPU and a control panel, and three terminals of the high-voltage igniter, a high-speed camera and a data acquisition instrument are simultaneously connected to the synchronization controller, and the core component CPU accurately controls the trigger time of each terminal by setting and storing the trigger sequence and time interval of each component; The test and data acquisition system includes pressure sensors, photodiodes and data acquisition instruments. A group of high-frequency dynamic pressure sensors and photodiodes are arranged at regular intervals on the center lines of the upper and lower walls of the upstream pre-test pipeline and the upstream segmented combined pipeline according to the length of the pipeline. The pressure sensor is used to record the pressure changes in the pipeline and monitor the formation and development of the detonation wave.

2. A visual test device for accurately testing the effect of a non-steady-state detonation flame arrester for combustible gas according to claim 1, characterized in that: During the test, close the air inlet at the front end of the combustion pipeline, connect the vacuum pump to the pressure relief port at the right end of the downstream pipeline and start to pump air. When the reading on the vacuum pressure gauge connected to the upper wall of the upstream pipeline is equal to zero or less than zero and remains stable, the vacuum state is reached. At this time, turn off the vacuum pump.

3. A visual test device for accurately testing the effect of a non-steady-state detonation flame arrester for combustible gas according to claim 1, characterized in that: The target concentration of the combustible gas is controlled by the mass flow meter MFC in the automatic gas distribution box. All mass flow meters are directly controlled by the computer of the control platform through electromagnetic stop valves. The concentration parameters in the computer supporting software are set during gas distribution, and the combustible gas and combustion-supporting gas in the raw gas cylinder are transported into the gas mixing chamber at the target equivalence ratio for uniform mixing, and then connected to the combustion pipeline intake valve through a pipeline.

4. A visual test device for accurately testing the effect of a non-steady-state detonation flame arrester for combustible gas according to claim 1, characterized in that: The non-steady-state detonation blocking test combustion pipeline is used to ensure that the deflagration to detonation transition is formed within a certain distance from the ignition position, and to test the blocking effect of the non-steady-state detonation flame arrester on the non-steady-state detonation wave; the non-steady-state detonation blocking test combustion pipeline can also be used to study the characteristics of the deflagration to detonation transition of premixed gases with different components or the same components but different equivalence ratios, and the schlieren technology and high-speed camera are combined to obtain the schlieren photos and then calculate the distance between the detonation occurrence position and the ignition position. Repeat the test multiple times under the same test conditions to obtain the run-up distance required for the deflagration to detonation transition under these conditions.

5. A visual test device for accurately testing the effect of a non-steady-state detonation flame arrester for combustible gas according to claim 1, characterized in that: The fire-blocking cores are selected from a variety of fire-blocking cores corresponding to detonation-resistant flame arresters to test the inhibitory effect of fire-blocking sections of different materials on non-steady-state detonation.

6. A visual test device for accurately testing the effect of a non-steady-state detonation flame arrester for combustible gas according to claim 1, characterized in that: The expansion joint is a section of pipe whose length can be adjusted within the range of expansion and contraction, and is used to compensate for the change in the position of the non-steady-state detonation caused by the change in the length of the combustion pipe and its own influence on the flow field; after the upstream pre-test pipe is replaced with the combination structure of the upstream segmented combined pipe, the expansion joint and the intermediate pipe, the position of the deflagration to detonation may be advanced or delayed relative to the pre-test, and the expansion joint is connected to the pipe. If the position of the deflagration to detonation is advanced, this section of the expansion joint is shortened; if the position of the deflagration to detonation is delayed, this section of the expansion joint is extended, so as to control the position of the non-steady-state detonation to be at the run-up distance on the basis of ensuring that other parts of the combustion pipe remain unchanged, and ensure that the non-steady-state detonation wave enters the fire-blocking section.

7. A visual test device for accurately testing the effect of a non-steady-state detonation flame arrester for combustible gas according to claim 1, characterized in that: The ignition electrode discharge trigger is realized by a synchronous controller. The premixed gas is ignited by a high-voltage electric spark generated by instantaneous discharge at the tip. During the instantaneous ignition process, the voltage and current data of the ignition spark of the ignition device are captured in real time and fed back to the oscilloscope by connecting suitable high-voltage probes and current probes to the ignition electrode ends exposed on the outer sides of the upper and lower walls of the pipeline. The energy value of the ignition spark of the ignition device is obtained through mathematical calculations inside the oscilloscope. Different ignition energies are generated by setting different capacitances and voltage values ​​in the high-voltage igniter, thereby determining different ignition capabilities for premixed combustible gases. During the test, the programmable synchronous controller is used to realize synchronous control and synchronous triggering of the high-voltage ignition system, high-speed camera and test and data acquisition system. The high voltage range is 5000-15000V.

8. A visual test device for accurately testing the effect of a combustible gas unsteady-state detonation flame arrester according to claim 1, characterized in that: The sensing part of the pressure sensor converts the pressure signal into an electric charge, and then converts the electric charge into a voltage proportional to the electric charge through an adapted charge amplifier. The charge amplifier is then connected to a dynamic data acquisition system to capture the deflagration flame and detonation wave with extremely fast propagation speed, and realize the synchronous acquisition of multiple signals at the same time; the photodiode is directly connected to the data acquisition instrument to detect the position of the flame and detonation wave propagation in the pipeline through the change of signal intensity; ensure that a group of pressure sensors and photodiodes are installed on the upper and lower walls of the intermediate pipeline adjacent to the fire-blocking section to detect the pressure and light intensity when the overdriven detonation wave is formed; at the same time, a group of pressure sensors and photodiodes are also installed on the upper and lower walls of the downstream pipeline adjacent to the intermediate fire-blocking section to detect the pressure and light signal in the pipeline behind the fire-blocking section.

9. A visual test method for accurately testing the effect of a combustible gas unsteady-state detonation flame arrester, characterized in that: Including pre-test test and non-steady-state detonation fire-blocking section fire-blocking effect test; The steps of the pre-test experiment are as follows: Step (1) adjusting the laboratory temperature to the initial temperature required by the test; Step (2) installing and debugging the test device, connecting the upstream pre-test pipeline, the non-steady-state detonation fire arrester section and the downstream pipeline required for the pre-test, and ensuring that the test system and the automatic gas distribution system, the test and data acquisition system, the Schlieren camera system, the high-voltage ignition and synchronization control system of each part are in normal state; Step (3) Turn on each test device and preheat for 30 minutes; Step (4) At the same time, the combustion pipeline is evacuated using a vacuum pump device, and then the air tightness of the combustion pipeline is checked to ensure that the pipeline has no leakage; Step (5) opens the air intake valve of the combustion pipeline and the exhaust pipeline at the lower wall at the end, delivers the combustible premixed gas of the target concentration configured by the automatic air distribution system into the combustion pipeline through the air intake pipeline, and discharges other gases or impurities in the pipeline from the exhaust pipeline by the replacement method. When the air distribution system software shows that the gas concentration reaches the target concentration and the concentration value is stable, stops the air distribution, and completes the air distribution and inflation work; Step (6) closing the air inlet valve and the air outlet valve of the combustion pipeline, and leaving it for about 30 seconds to ensure that the combustible gas mixture is in a stable and uniform mixing state; Step (7) turning on the high-voltage ignition system and setting the ignition voltage of the high-voltage ignition system to a target value; Step (8) turns on and adjusts the high-voltage probe, current probe, ignition energy oscilloscope, data acquisition instrument, high-speed camera and synchronization controller to a triggering state; After step (9) is ready, press the ignition switch connected to the synchronous controller to start the high-voltage ignition system, realize ignition in the combustion pipe by discharging at the tip of the ignition electrode, and obtain the energy value of the instantaneous discharge through each probe and the ignition energy oscilloscope. At the same time, trigger the high-speed camera and the data acquisition instrument in sequence according to the preset time to shoot the flame acceleration and the process of deflagration to detonation, and measure the dynamic changes of the pressure and light intensity in the combustion pipe; Step (10) After a flame acceleration and deflagration-to-detonation test is completed, the image data of the high-speed camera and the pressure and light signal data recorded by the data acquisition instrument are stored in a target storage card to prepare for subsequent data processing and analysis; Step (11) cleaning the combustion pipe, resetting each test device, and preparing to start the next set of repeated tests; Step (12) carries out at least 13 repeated tests under the same test conditions, including the same combustible premixed gas components and equivalence ratio, to study the characteristics of the deflagration-to-detonation process, and obtains the run-up distance of the deflagration-to-detonation of each group by analyzing the image data of the high-speed camera and the pressure and light signal data recorded by the data acquisition instrument, and reduces the error by taking the average value, and finally obtains a fixed run-up distance of the deflagration-to-detonation under the test conditions; In addition to obtaining the run-up distance, step (13) changes the working conditions after repeating the test under the same working conditions of step (12). The components of the combustible gas are changed by connecting different air intake cylinders, the equivalent ratio of the combustible gas is changed by setting the parameters of the gas distribution system software, the ignition position is changed by setting different perforation installation positions of the ignition electrode, the ignition energy output by the ignition electrode is changed by setting the ignition voltage of the high-voltage igniter, and the blockage rate of the combustion pipeline is changed by setting triangular obstacles of different heights, that is, the ratio of the obstacle height of the same longitudinal section to the height of the combustion pipeline. Repeated tests are carried out in each group to further study the characteristics and laws of the process of transformation from deflagration to detonation of premixed gas under the influence of factors such as different combustible gas components, premixed gases of different equivalent ratios, different ignition positions, different ignition energies, and different pipeline blockage rates.

10. A visual test method for accurately testing the effect of a combustible gas unsteady-state detonation flame arrester according to claim 9, characterized in that: The test of the fire-blocking effect of the non-steady-state detonation fire-blocking section includes the following steps: Step (A) selects the number of sections of the upstream segmented combined pipeline according to the run-up distance obtained in step (12) of the pre-test test process, so that the sum of the lengths of the upstream segmented combined pipeline, the expansion joint and the intermediate pipeline is the length of the run-up distance, connects the starting end of the fire-blocking section to the middle pipeline, and connects the end to the front of the downstream pipeline, and then repeats steps (3)-(11) in the pre-test test, and observes and judges whether the occurrence position of the non-steady-state detonation is directly in front of the fire-blocking section through the schlieren image taken by the high-speed camera and the pressure and light signal intensity obtained by the pressure sensor and the photodiode. If the occurrence position of the non-steady-state detonation is advanced, the length of the expansion joint is shortened; if the occurrence position of the non-steady-state detonation is delayed, the length of the expansion joint is extended to ensure that the non-steady-state detonation occurs directly in front of the fire-blocking section; Step (B) after a test of the fire-blocking effect of the non-steady-state detonation fire-blocking section is completed, the image data of the high-speed camera and the pressure signal and light signal data recorded by the data acquisition instrument are stored, and the process of the fire-blocking section blocking the non-steady-state detonation wave is studied through the schlieren image taken by the high-speed camera. At the same time, the schlieren image can also be used to observe whether there is an obvious flame in the downstream pipeline. Then, a group of pressure sensors and photodiodes on the upper and lower walls of the downstream pipeline close to the fire-blocking section and the high-speed schlieren image are combined to judge the blocking effect of the fire-blocking section on the non-steady-state detonation wave. If the pressure sensors and photodiodes are in the results of repeated tests for a predetermined number of times, the fire-blocking section will be blocked. If the photodiode does not detect a sudden change signal, and no obvious detonation reaction front or flame is observed in the schlieren image, it means that the fire-blocking section has excellent performance and can effectively block the non-steady-state detonation; if there is a sudden change in the curve once in the continuous test or an obvious detonation reaction front or flame is observed in the schlieren image, it means that the non-steady-state detonation is not effectively blocked by the fire-blocking section, and the fire-blocking performance of the fire-blocking section is considered to be unqualified. The performance of the fire-blocking section can be optimized by further changing the fire-blocking core material or the structure of the fire-blocking section, thereby providing a practical solution for the further development of high-efficiency non-steady-state detonation flame arresters.

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