Test bed and test method for hydrogen combustion characteristic research

Abstract

The invention relates to a test bed and a test method for hydrogen combustion characteristic research, the test bed comprises a gas supply system, a gas mixing system, a vacuum pump, an ignition system, a monitoring system and a nozzle, and the components realize accurate control and cooperative work through pipelines and valves. The gas supply system achieves quantitative mixing of hydrogen and air through a mass flow controller, a baffle structure is arranged in the gas mixing system, and the uniformity and concentration stability of mixed gas are guaranteed. The ignition system adopts a power-adjustable laser, ignition energy and a pulse time sequence can be controlled, and stable and controllable ignition is realized; the monitoring system carries out visualization and temperature field synchronous measurement on the combustion process through an optical schlieren instrument and an infrared thermal imager. Compared with the prior art, the test bed is safe and reliable in structure, experimental parameters can be accurately regulated and controlled, the test bed can flexibly adapt to different combustion working conditions, and the test bed is suitable for hydrogen combustion mechanism research, combustion and detonation-detonation conversion characteristic analysis and hydrogen energy system safety performance verification.

Description

Technical Field

[0001] This invention relates to the field of hydrogen combustion and safety research equipment technology, and in particular to a test bench and testing method for studying the characteristics of hydrogen combustion. Background Technology

[0002] With the ongoing transformation of the global energy structure and the advancement of carbon emission reduction targets, clean and efficient energy has become a core direction for future development. Hydrogen energy, due to its high calorific value, zero carbon emissions, and renewable characteristics, is widely considered an important pathway to achieving green and low-carbon energy. However, hydrogen is a highly flammable gas with a wide combustion range, high explosion limits, and low minimum ignition energy, making its combustion and explosion behavior extremely sensitive. Insufficient understanding of its combustion characteristics during the production, storage, transportation, and application of hydrogen can lead to significant safety risks.

[0003] Currently, the propagation mode of hydrogen combustion and the mechanism of its transition from deflagration to detonation remain highly uncertain. Although some quantitative data exists, the lack of systematic experimental verification makes it difficult to accurately determine the concentration critical point. This directly impacts safety management and engineering design—it's difficult to precisely set facility safety distances, ventilation standards, and pressure relief device parameters; risk assessments during production, storage, and transportation may be biased; detection and early warning systems relying on concentration thresholds struggle to determine reasonable alarm values, leading to false alarms or missed alarms and hindering emergency response. In the event of a hydrogen accident, if rescuers cannot accurately determine the combustion pattern based on concentration, inappropriate measures may exacerbate the hazard. These uncertainties not only increase public safety concerns but also weaken industry investment confidence, hindering the large-scale promotion of hydrogen energy. The combustion characteristics of hydrogen vary significantly with volume fraction; flame propagation speed, combustion temperature, and combustion propagation patterns differ significantly at different concentrations. In-depth research into combustion patterns under varying concentration conditions is crucial for revealing combustion mechanisms, defining safety boundaries, optimizing ventilation and venting designs, and improving detection and early warning accuracy.

[0004] However, the number of experimental setups available for hydrogen ignition and combustion research is extremely limited, with most existing devices employing traditional spark plug ignition. Spark plug ignition suffers from unstable energy and uncontrollable discharge intensity, making it difficult to accurately quantify the actual ignition energy and resulting in poor repeatability of experimental results. Furthermore, spark plugs can only ignite a localized gas mixture near the electrodes, limiting the initial propagation range and spatial expansion characteristics of the flame, making it difficult to accurately reflect the overall combustion process of hydrogen at different concentrations. In addition, the hydrogen combustion flame is pale blue and difficult to observe with the naked eye, and existing experimental setups generally lack methods for flame visualization and simultaneous data acquisition, making it impossible to simultaneously acquire key parameters such as temperature field, flow field, and light radiation. These shortcomings result in a lack of systematic experimental support for the study of hydrogen combustion mechanisms under varying concentration conditions, hindering the development of safety assessments and engineering applications.

[0005] Chinese patent application CN118730479A discloses a hydrogen loop experimental device and its experimental method, including a gas supply system, a gas mixing and pressurization system, a pipe safety and equipment adaptability testing system, a venting and combustion testing system, and a data image acquisition system. It can simulate the hydrogen permeation performance of welded joints using different welding processes under different delivery pressures, hydrogen doping ratios, and testing times. It can also monitor changes in parameters such as temperature, pressure, sound pressure, and flame intensity during the hydrogen venting and combustion process in real time. However, the ignition device of this device only meets the basic requirement of igniting the vented gas, with severely insufficient accuracy and controllability. Furthermore, the monitoring system only covers basic parameters and lacks the core visualization dimension of the combustion process. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low concentration control precision, poor ignition stability, and insufficient safety protection in existing combustion test benches used in hydrogen combustion research. This invention provides a test bench and testing method for studying hydrogen combustion characteristics. The test bench has advantages such as reliable and safe structure, controllable and precise hydrogen concentration, accurately adjustable ignition energy, and visualization of the combustion process. Through modular design, it can be flexibly adapted to different combustion conditions, making it suitable for studying hydrogen combustion mechanisms, analyzing the characteristics of combustion transition to deflagration / detonation, and verifying the safety performance of hydrogen energy systems, providing comprehensive experimental support for hydrogen energy scientific research and engineering applications.

[0007] The objective of this invention can be achieved through the following technical solutions: A test rig for studying the combustion characteristics of hydrogen includes a gas supply system, a gas mixing system, a vacuum pump, an ignition system, a monitoring system, and a nozzle, which are sequentially connected via pipelines to a control unit for coordinated control. The gas supply system includes a hydrogen tank, an air tank, and a nitrogen tank. The hydrogen tank is connected to a hydrogen branch, the air tank is connected to an air branch, and the nitrogen tank is connected to a nitrogen branch. Each branch is equipped with a one-way valve, a pressure reducing valve, and a mass flow controller to control the gas output flow. The hydrogen branch is equipped with a flame arrester to prevent flame backflow. The nitrogen branch and the air branch merge downstream to form a mixing branch, while the hydrogen branch is independent. The mixing system includes a baffle-type mixing tank, a solenoid valve, a pressure gauge, and a hydrogen concentration sensor. The mixing branch and the hydrogen branch are connected to the front end of the mixing tank. The front end of the mixing tank is connected to a solenoid valve that controls the timing and flow rate of the gas entering the tank, and the rear end of the mixing tank is connected to a hydrogen concentration sensor that detects the concentration of the mixed gas. Both the front and rear ends of the mixing tank are connected to a pressure sensor that monitors the change in flow resistance. The outlet of the mixing tank is divided into two paths: one path is connected to a vacuum pump, and the other path is connected to a nozzle via a solenoid valve. The rear end of the vacuum pump is connected in series with a solenoid valve. The ignition system is located in the area directly in front of and above the nozzle, and the monitoring system is located behind the nozzle.

[0008] Furthermore, the ignition system includes a laser emitting head, a laser ignition controller, and a focusing lens group. The focusing lens group is fixed by a three-dimensional adjustable bracket and installed in the area directly in front of and above the nozzle. The laser ignition controller is electrically connected to the laser emitting head and adjusts the single-pulse energy, emission frequency, and timing of the laser emitting head. The pulsed laser emitted by the laser emitter is focused by a focusing lens group onto the central region of the combustion chamber for non-contact ignition.

[0009] Furthermore, the laser emitting head is an adjustable power pulsed laser, whose ignition energy is continuously adjustable in the range of 0.1mJ-10mJ; the laser emitting head maintains an angle of 20°-30° with the central axis of the nozzle, and the laser is focused on the core area of ​​the mixed gas at the nozzle outlet; the laser emitting head is also equipped with a high-temperature resistant quartz protective cover and a metal heat shield.

[0010] Furthermore, the mixing tank is made of 316L stainless steel and has an internal cross-baffle structure that allows hydrogen and air to mix thoroughly inside the tank. The mixing tank is connected to the pipeline via flanges or welding.

[0011] Furthermore, the monitoring system includes a schlieren imaging concave mirror, an optical schlieren spectrometer, and an infrared thermal imager; the schlieren imaging concave mirror and the optical schlieren spectrometer are arranged opposite each other, and the nozzle is placed in the optimal observation area of ​​the schlieren imaging concave mirror; the infrared thermal imager is aimed at the nozzle spray and combustion area, and works synchronously with the optical schlieren spectrometer to record the temperature field in real time.

[0012] Furthermore, the control unit includes a data acquisition module and a safety interlock module. The data acquisition module is connected to the mass flow controllers of each branch, the hydrogen concentration sensor, each pressure gauge, and the monitoring system via signal lines to collect flow rate, concentration, pressure, temperature, and monitoring data in real time. The safety interlock module is connected to the solenoid valves, ignition system, and pressure reducing valve of each branch via control lines to automatically cut off the gas supply and shut down the laser ignition system in case of overpressure, excessive richness, or abnormal temperature.

[0013] A method for testing hydrogen combustion characteristics based on the test bench described above for studying hydrogen combustion characteristics includes the following steps: Preparation phase: Install the required nozzles and pipelines, and check the system's sealing, grounding wires, and the integrity of the fire extinguishing devices; Purging phase: Open the nitrogen branch and purge and pressure test the pipeline and mixing tank. Repeat three times to remove residual gas. Vacuum stage: Open the solenoid valve at the back of the vacuum pump, start the vacuum pump, and evacuate the gas mixing system to the set pressure to eliminate residual gas; Gas mixing stage: Hydrogen and air are controlled to enter the mixing tank in a set ratio by mass flow controllers and solenoid valves. The concentration of the mixed gas is monitored in real time by the hydrogen concentration sensor at the back of the mixing tank, and the output of the mass flow controller is dynamically adjusted to prepare a mixed gas with the target volume fraction. Monitoring phase: Activate the optical schlieren and infrared thermal imager to simultaneously monitor flame propagation and temperature field changes; Ignition stage: The laser emitter focuses the laser to the center region of the combustion chamber through the focusing lens group, and ignites the mixed gas with a preset energy pulse to form a stable fire core. The monitoring system continuously records the flame propagation pattern, flow field disturbance and temperature field change data. Final stage: Shut down the gas source and laser system, perform nitrogen purging and system reset to ensure the equipment is restored to a safe state.

[0014] Furthermore, the purging and pressure holding test process includes: Close all mass flow controllers and solenoid valves, open the pressure reducing valve of the nitrogen tank, and adjust the outlet pressure to the set value; Turn on the mass flow controller of the nitrogen branch, and simultaneously turn on the first solenoid valve of the mixing branch. Close the second and third solenoid valves, maintain the system pressure for the preset time, check the pipeline sealing and ensure that the gas replacement is sufficient. After the pressure holding period is completed, open the third solenoid valve at the tail end of the mixing tank to purge the air. Repeat the above operation 3 times to thoroughly remove residual gas and impurities from the system.

[0015] Furthermore, during the ignition stage, the energy and timing of the single pulse are adjusted by the laser ignition controller to achieve comparable combustion tests of mixed gases of different concentrations under the same energy conditions.

[0016] Furthermore, the flame propagation pattern, flow field disturbance, and temperature field change data obtained by the monitoring system are synchronized in time through the data acquisition module to construct a multi-dimensional data model of flame propagation speed and temperature change, and the influence of hydrogen concentration change on combustion characteristics is analyzed based on the multi-dimensional data model.

[0017] Compared with the prior art, the beneficial effects of the present invention include: 1. This invention provides an ignition test apparatus for studying the combustion characteristics of hydrogen, which can precisely adjust the hydrogen-air mixing ratio according to experimental requirements to achieve combustion studies under varying concentration conditions. The apparatus uses a mass flow controller and concentration sensor in a closed-loop control system to precisely adjust the hydrogen integral number within the range of 0-100%, ensuring uniformity of the mixed gas concentration. A flame arrester is installed in the hydrogen branch of the apparatus to prevent flame backflow.

[0018] 2. The device of this invention is equipped with an optical schlieren and an infrared thermal imager, which can simultaneously monitor gas flow, flame propagation and temperature field distribution, providing high-precision and visualization means for combustion behavior analysis and experimental data acquisition.

[0019] 3. The ignition method of this invention uses a laser ignition device, which can precisely control the ignition energy and pulse timing. Compared with traditional spark plug ignition, it can not only stably form the initial flame nucleus, but also achieve controllable and repeatable combustion experiments at different concentrations, thereby improving the reliability and comparability of experimental data.

[0020] 4. By setting up internal baffles, flow controllers and pressure monitoring systems in the mixing tank, this invention achieves thorough mixing of the mixed gas and precise flow regulation, effectively ensuring the accuracy and uniformity of the experimental hydrogen concentration, and solving the problem that traditional test benches cannot continuously adjust the concentration.

[0021] 5. The present invention has designed a complete experimental process including purging, vacuuming, gas mixing, ignition and monitoring. It can remove residual air before the experiment, ensure pipeline sealing and gas mixture purity, thereby significantly improving the safety and controllability of hydrogen combustion experiments.

[0022] 6. The device of this invention is suitable for flexible adjustment of different pipe diameters, nozzle heights and injection angles, and can simulate the hydrogen combustion process under various working conditions, supporting multi-dimensional applications from basic combustion mechanism research to safety boundary assessment, ventilation and venting optimization.

[0023] 7. The hydrogen gas integral of this invention can be precisely adjusted within the range of 0-100%. Closed-loop control through mass flow controller and concentration sensor ensures uniformity of mixed gas concentration. The laser ignition energy is continuously adjustable from 0.1mJ to 10mJ, and the pulse timing and frequency can be precisely set, enabling comparable experiments of mixed gases of different concentrations under the same energy conditions. The overall parameters are precise and controllable, and the experiment has strong repeatability. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the gas supply and mixing system of the hydrogen ignition test bench in this invention; Figure 2 This is a schematic diagram of the layout of the ignition and monitoring system in this invention; Figure 3 This is a flowchart of the method of the present invention; In the diagram: 1. Air tank; 4. Nitrogen tank; 7. Hydrogen tank; 16. Vacuum pump; 2. First pressure reducing valve; 5. Second pressure reducing valve; 8. Third pressure reducing valve; 17. Fourth pressure reducing valve; 3. First check valve; 6. Second check valve; 9. Third check valve; 10. First flame arrester; 22. Second flame arrester; 11. First mass flow controller; 12. Second mass flow controller; 13. First solenoid valve; 18. Second solenoid valve; 21. Third solenoid valve; 14. First pressure gauge; 19. Second pressure gauge; 15. Mixing tank; 20. Hydrogen concentration sensor; 23. Nozzle; 24. Laser ignition controller; 25. Laser emitter; 26. Focusing lens group; 27. Schlieren imaging concave mirror; 28. Optical schlieren; 29. ​​Infrared thermal imager. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] Example 1 This embodiment discloses an experimental setup for studying the combustion characteristics of hydrogen. The experimental setup is as follows: Figure 1 and Figure 2 As shown, it includes a gas supply system, a gas mixing system, a vacuum pump, an ignition system, a monitoring system, and a nozzle 23. All components are connected by pipelines, and precise gas supply and regulation are achieved through controllers and valves to meet the requirements of hydrogen combustion characteristic experiments.

[0027] The gas supply system includes a hydrogen tank 7, an air tank 1, and a nitrogen tank 4. Hydrogen tank 7 is connected to a hydrogen branch, air tank 1 is connected to an air branch, and nitrogen tank 4 is connected to a nitrogen branch. Each branch is equipped with a check valve, a pressure reducing valve, and a mass flow controller to control the gas output flow. The hydrogen branch is equipped with a first flame arrester 10 to prevent backflow of the flame.

[0028] Specifically, air tank 1, nitrogen tank 4, and hydrogen tank 7 are respectively equipped with a first pressure reducing valve 2, a second pressure reducing valve 5, and a third pressure reducing valve 8, as well as a first check valve 3, a second check valve 6, and a third check valve 9. The downstream outlet pressure of the pressure reducing valves is set at 0.5 MPa, and the pressure resistance of each pipeline is not less than 2 MPa to ensure the safety of system operation. The hydrogen branch is connected to a first flame arrester 10 after the third check valve 9 to prevent hydrogen backfire and avoid dangerous accidents.

[0029] The nitrogen branch and the air branch merge downstream to form a mixing branch. The output gases from air tank 1 and nitrogen tank 4 are connected to the mixing tank 15 through the mixing branch, and their flow rates are precisely regulated by the first mass flow controller 11.

[0030] The hydrogen branch is independent, that is, the hydrogen tank 7 has a separate branch, and the output flow is controlled by the second mass flow controller 12.

[0031] After flow regulation, air, nitrogen, and hydrogen are finally merged into the same mixing branch, providing a stable gas supply for subsequent mixing. The output of the gas supply system is controlled by the first solenoid valve 13 to realize the opening and closing and precise regulation of the gas supply.

[0032] The gas mixing system includes a baffle-type gas mixing tank 15, a second solenoid valve 18, a pressure gauge 19, and a hydrogen concentration sensor 20.

[0033] The mixing tank 15 is made of 316L stainless steel to ensure its corrosion resistance and structural safety under high-pressure hydrogen environments. The tank has an effective volume of 2 L and a rated maximum working pressure of 34.5 MPa, meeting the requirements for preparing high-pressure mixed gases. The mixing tank 15 features a cross-arranged multi-layered baffle structure. These baffles are welded and fixed using thin stainless steel plates of the same material. By forming complex flow channels, the gas flow entering the tank undergoes multiple collisions, splitting, and swirling as it passes through the interior, significantly enhancing turbulence intensity and improving gas mixing efficiency and uniformity, thus avoiding component inhomogeneity caused by laminar flow or flow field deviations. The mixing tank 15 is connected to pipelines via flanges or welding.

[0034] The front and rear ends of the mixing tank 15 are connected to pressure sensors that monitor changes in flow resistance, specifically a first pressure sensor 14 and a second pressure sensor 19, to monitor changes in flow resistance and gas pressure status, so as to ensure the safety and controllability of the experimental process.

[0035] A hydrogen concentration sensor 20 is installed at the rear end of the gas mixing tank 15 to detect the concentration of the mixed gas. Its measurement range is 0-100%, and its response time is 0.1 s. It is used to monitor the hydrogen concentration of the mixed gas in real time to ensure the accuracy of experimental data. At the same time, a second solenoid valve 18 is connected to the front end of the gas mixing tank 15 to control the timing and flow rate of gas entry. It is used to control the output of the mixed gas and achieve precise gas supply to the test nozzle.

[0036] The outlet of the mixing tank 15 is divided into two paths: one path is connected to the vacuum pump, and the other path is connected to the nozzle 23 via the solenoid valve 21. The second solenoid valve 18 is connected in series at the rear end of the vacuum pump 16.

[0037] The vacuum system includes a vacuum pump 16 and a fourth pressure-reducing valve 17. A pressure-reducing valve is installed at the outlet of the vacuum pump, controlling the outlet pressure to 0.5 MPa after pressure reduction. Each branch of the vacuum pipeline is equipped with an independent solenoid valve, a second solenoid valve 18, used to control the start and stop of the vacuum pumping function. Before the experiment, the vacuum system can be activated to pre-evacuate the mixing tank 15 and its connecting pipelines, thereby creating a controllable low-pressure or near-vacuum environment. This effectively removes residual gases or impurities, ensuring that the initial composition of the mixed gas meets the experimental requirements and avoiding interference from residual air or moisture on the mixing ratio and ignition characteristics.

[0038] Nozzle 23 is located at the end outlet of the experimental device and serves as the final outlet component for the external injection and ignition experiments of the mixed gas. A second flame arrester 22 is installed at the front end of the nozzle to prevent flame backflow into the upstream pipeline, thus preventing pipe combustion accidents caused by backfire and ensuring the safe operation of the entire system. The nozzle structure adopts a detachable modular design, facilitating replacement according to different experimental requirements. The nozzle outlet orifice diameter can be set to four specifications: 1.0 mm, 2.0 mm, 3.0 mm, and 4.0 mm, to simulate different leakage or injection conditions. Under the condition of ensuring the same outlet cross-sectional area, the nozzle shape can also be designed as circular, rectangular, triangular, or elliptical to study the influence of nozzle geometry on the hydrogen injection flow field, combustion pattern, and ignition characteristics.

[0039] The ignition system is located in the area directly in front of and above the nozzle 23, and the monitoring system is located behind the nozzle 23.

[0040] The ignition system includes a laser emitter 25, a laser ignition controller 24, and a focusing lens group 26. The laser ignition controller 24 uses an adjustable power pulsed fiber laser as its core component, enabling precise control of single-pulse energy, emission frequency, and focusing time to meet the ignition requirements under different hydrogen concentrations. The system achieves programmable control of laser energy and trigger timing through modular electronic control. It is air-cooled, and its internal power supply lasts for approximately 40 minutes, making it suitable for multiple rounds of repeated ignition experiments.

[0041] The laser emitter 25 and the focusing lens group 26 are fixed by a three-dimensional adjustable bracket and installed in the area directly in front of and above the nozzle 23. The laser ignition controller 24 is electrically connected to the laser emitter 25 and adjusts the single pulse energy, emission frequency and timing of the laser emitter 25.

[0042] The laser emitter 25 employs a single-mode near-infrared fiber laser with a wavelength of 1080 nm, outputting a high-energy pulsed beam. The laser is directly focused onto the core region of the gas mixture near the nozzle via a focusing lens 26, forming a localized high-temperature plasma at this focal point, achieving instantaneous ignition of the gas mixture. The laser output power is adjustable from 50 W to 200 W, with a single pulse energy of 0.1 mJ to 10 mJ, a pulse width of approximately 50 to 200 ns, and a pulse repetition frequency adjustable from 10 Hz to 1 kHz. This allows for precise control of the ignition energy, ensuring stable ignition of gas mixtures of different concentrations under safe and controllable conditions.

[0043] The laser emitter 25 and focusing lens assembly 26 are mounted in the area directly above and in front of the nozzle on the test stand, maintaining an angle of 20°-30° with the central axis of the nozzle, and a horizontal distance of approximately 100-150 mm. This arrangement avoids direct contact between the high-temperature flame and the laser, preventing damage to the optical components from heat radiation and particle impact, while ensuring that the laser focus accurately targets the core of the gas mixture at the nozzle exit, achieving stable ignition. To prevent damage to the equipment from laser reflection and flame backflow, the laser emitter 25 is equipped with a high-temperature resistant quartz protective cover and a metal heat shield. A precision three-dimensional adjustable bracket allows for fine-tuning of the optical axis direction, focusing distance, and angle to adapt to experimental requirements of different jet velocities and ignition positions.

[0044] The monitoring system includes a schlieren imaging concave mirror 27, an optical schlieren instrument 28, and an infrared thermal imager 29. The schlieren imaging concave mirror 27 and the optical schlieren instrument 28 are arranged opposite each other, and the nozzle 23 is placed in the optimal observation area of ​​the schlieren imaging concave mirror 27 with a focal length of 1.5m. The infrared thermal imager 29 is aimed at the area of ​​the nozzle 23 for spraying and combustion, and works synchronously with the optical schlieren instrument 28 to record the temperature field in real time.

[0045] The optical schlieren 28 integrates a camera, a point light source, and a beam splitter. It utilizes a concave mirror to reflect light, ultimately establishing the optimal observation area at a focal length of 1.5m, where the nozzle 23 is also positioned. Since hydrogen combustion produces a pale blue flame, the entire device aims to observe gas flow patterns and combustion characteristics at different concentrations, which are difficult to see with the naked eye. The infrared thermal imager 29 is used to monitor the hydrogen reaction temperature and the temperature diffusion pattern during combustion.

[0046] The control unit includes a data acquisition module and a safety interlock module. The data acquisition module is connected to the mass flow controllers of each branch, the hydrogen concentration sensor 20, each pressure gauge and the monitoring system through signal lines to collect flow, concentration, pressure, temperature and monitoring data in real time. The safety interlock module is connected to the solenoid valves, ignition system and pressure reducing valve of each branch through control lines to automatically cut off the gas supply and shut down the laser ignition system in case of overpressure, excessive richness or abnormal temperature.

[0047] Example 2 This embodiment, based on the experimental apparatus disclosed in Embodiment 1 above, discloses a method for testing the combustion characteristics of hydrogen, the specific steps of which are as follows: Figure 3 As shown, it includes: Step S1, Preparation Stage: Install the required nozzles and pipelines, and check the system's sealing and the integrity of the grounding wire and fire extinguishing device.

[0048] The optical schlieren 28 integrates a camera, a point light source, and a beam splitter. It utilizes a concave mirror to reflect light, ultimately establishing the optimal observation area at a focal length of 1.5m, where the nozzle 23 is also positioned. Since hydrogen combustion produces a pale blue flame, the entire device aims to observe gas flow patterns and combustion characteristics at different concentrations, which are difficult to see with the naked eye. The infrared thermal imager 29 is used to monitor the hydrogen reaction temperature and the temperature diffusion pattern during combustion.

[0049] Step S2, purging stage: Open the nitrogen branch and purge and pressure test the pipeline and mixing tank 15. Repeat three times to remove residual gas.

[0050] The purging and holding pressure test process includes: Close the first mass flow controller 11, the second mass flow controller 12, the first solenoid valve 13, the second solenoid valve 18, and the third solenoid valve 21. Open the second pressure reducing valve 5 of the nitrogen tank 4 and adjust the outlet pressure to the set value (approximately 0.5 MPa). Then, open the first mass flow controller 11 of the mixing branch, and open the first solenoid valve 13 and the second check valve 6. Close the second solenoid valve 18 and the third solenoid valve 21 to maintain system pressure for approximately 1 minute to check the sealing of the mixing system and ensure sufficient gas replacement. After the pressure holding is completed, open the third solenoid valve 21 at the tail end of the mixing tank 15 to vent the system.

[0051] The above purging and pressure holding process is repeated three times to thoroughly remove residual gas and impurities from the system and ensure that the gas mixing system is in a clean and stable state.

[0052] Step S3, Vacuum Stage: Open the second solenoid valve 18 at the rear end of the vacuum pump 16, start the vacuum pump 16, and evacuate the gas mixing system to the set pressure to eliminate residual gas.

[0053] The vacuum pump 16 and its downstream second solenoid valve 18 are turned on to initiate the vacuuming operation, evacuating the mixing tank 15 and its connecting pipelines to remove residual air and impurities from the system. After reaching the set vacuum level, the second solenoid valve 18 and the vacuum pump 16 are closed sequentially to complete the vacuum stage operation. This step ensures the accuracy and purity of the subsequent gas mixing process, providing reliable initial conditions for mixing ratio control.

[0054] Step S4, gas mixing stage: The flow rate and entry time of hydrogen and air are controlled by a mass flow controller and a solenoid valve to prepare a mixed gas with the target volume fraction.

[0055] Keep all mass flow controllers and solenoid valves initially closed. First, open the first solenoid valve 13 at the front end of the mixing tank 15, adjust the second pressure reducing valve 5 and the first pressure reducing valve 2 of the hydrogen and air branches to the set pressure (generally 0.5 MPa), and set the target flow rate value on the first mass flow controller 11 and the second mass flow controller 12 according to the required mixing ratio. Then, sequentially open the first one-way valve 3 of the air branch, the second one-way valve 6 of the nitrogen branch, and the third one-way valve 9 of the hydrogen branch to allow the gas to enter the mixing tank 15 for mixing according to the set ratio. After the gas mixing is completed, close the one-way valves of the hydrogen and air branches and the mass flow controllers. At this time, the mixed gas concentration is detected in real time by the hydrogen concentration sensor 20 at the end of the mixing system to confirm that the mixing ratio meets the experimental set value.

[0056] Step S5, Monitoring Phase: Start the optical schlieren 28 and infrared thermal imager 29 to simultaneously monitor flame propagation and temperature field changes.

[0057] The optical schlieren spectrometer 28 and the schlieren imaging concave mirror 27 are activated, and the optical axis and focal length are adjusted to position the nozzle 23 in the optimal observation area for real-time observation of the gas mixture injection and combustion process. Simultaneously, the infrared thermal imager 29 is activated to continuously monitor and record the temperature field in the nozzle area, obtaining data on flame temperature distribution and diffusion characteristics during combustion. This stage provides visualization and quantitative basis for subsequent ignition and combustion behavior analysis.

[0058] Step S6, Ignition stage: The laser emitter 25 focuses the laser onto the central region of the combustion chamber through the focusing lens group 26, and ignites the mixed gas with a preset energy pulse to form a stable fire core.

[0059] The laser ignition controller 24 is activated, and the laser output power, single-pulse energy, and pulse frequency parameters are set (e.g., power 100W, frequency 100Hz). The pulsed beam generated by the laser emitter 25 is focused by the focusing lens 26 onto the core region of the mixed gas near the nozzle 23, forming a local high-temperature plasma at the focal point, inducing the mixed gas to ignite instantaneously and form a stable fire core. Simultaneously, the third solenoid valve 21 at the tail end of the mixing tank 15 is activated, allowing the mixed gas prepared according to the set ratio to be continuously delivered to the nozzle, achieving uniform injection and maintaining the combustion process.

[0060] By adjusting the single-pulse energy and timing using the laser ignition controller 24, comparable combustion tests of mixed gases with different concentrations under the same energy conditions can be achieved.

[0061] During the ignition phase, the monitoring system continuously records data on flame propagation patterns, flow field disturbances, and temperature field changes.

[0062] The data on flame propagation morphology, flow field disturbance, and temperature field changes obtained by the monitoring system are synchronized in time through the data acquisition module. This data is used to construct a multidimensional data model of flame propagation speed and temperature changes, and the influence of hydrogen concentration changes on combustion characteristics is analyzed based on the multidimensional data model.

[0063] Step S7, End Stage: Shut down the gas source and laser system, perform nitrogen purging and system reset to ensure the equipment is restored to a safe state.

[0064] After the ignition experiment is completed, the laser ignition controller 24, the third solenoid valve 21 at the tail end of the mixing tank 15, and the gas supply branch are closed sequentially. Once the system pressure returns to atmospheric pressure, all solenoid valves and the mass flow controller are closed, and the vacuum pump 16 and the monitoring equipment (optical schlieren 28 and infrared thermal imager 29) are stopped. To ensure safety, the nitrogen branch is reopened, and the system pipeline is purged with nitrogen to remove any remaining mixed gas. Finally, the equipment is checked and cleaned, and data from each stage of the experiment are recorded to provide safe preparation conditions for the next experiment.

[0065] To study the effects of nozzle geometry or injection angle on flame propagation and stability, nozzle modules of different specifications or shapes (such as circular, rectangular, or elliptical) can be used, and the operation process of steps S1-S7 can be repeated. By comparing parameters such as flame length, combustion zone temperature distribution, and ignition delay time, the regular characteristics of hydrogen combustion behavior under different injection conditions can be obtained.

[0066] If it is necessary to simulate external airflow disturbances or environmental ventilation conditions, an external wind field device can be arranged near nozzle 23 to adjust the wind speed and direction parameters and perform coordinated control while executing step S6 ignition stage, so as to study the influence of environmental wind on flame morphology, stability and backfire risk, and provide experimental support for hydrogen combustion safety under complex working conditions.

[0067] When it is necessary to verify the influence of laser ignition parameters on ignition success rate and fire nucleus formation characteristics, multiple sets of comparative experiments can be conducted by adjusting the output power of laser emitter 25, focal length position of focusing lens 26 and pulse frequency, repeating step S6, and combining the synchronous monitoring results of infrared thermal imager 29 and optical schlieren 28 to analyze the correspondence between laser energy density and fire nucleus formation time.

[0068] After the equipment has been out of service for an extended period or after an experiment, the system should be purged as described in step S7 to ensure that any residual gas in the pipelines and mixing tank 15 is completely emptied. Then, all solenoid valves should be closed, the power supply disconnected, and key components (including the laser emitter 25, focusing lens group 26, optical schlieren 28, and infrared thermal imager 29) should be dustproofed and moisture-proofed to extend the equipment's lifespan and ensure the safety and reliability of the next experiment.

[0069] Example 3 Based on Embodiment 2, this embodiment provides an electronic device, including: one or more processors and a memory, wherein the memory stores one or more programs, the one or more programs including instructions for executing the aforementioned hydrogen combustion characteristic test method.

[0070] At the hardware level, the electronic device includes a processor, internal bus, network interface, memory, and non-volatile memory, and may also include other hardware required for business operations. The processor reads the corresponding computer program from the non-volatile memory into memory and then runs it to implement the aforementioned hydrogen combustion characteristic testing method. Of course, in addition to software implementation, this invention does not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc. That is to say, the execution subject of the following processing flow is not limited to individual logic units, but can also be hardware or logic devices.

[0071] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0072] Computer-readable media include both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0073] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A test bench for studying the combustion characteristics of hydrogen, characterized in that, The test bench includes a gas supply system, a gas mixing system, a vacuum pump, an ignition system, a monitoring system, and a nozzle (23), which are connected in sequence via pipelines to a control unit for coordinated control; wherein, The gas supply system includes a hydrogen tank (7), an air tank (1), and a nitrogen tank (4). The hydrogen tank (7) is connected to a hydrogen branch, the air tank (1) is connected to an air branch, and the nitrogen tank (4) is connected to a nitrogen branch. Each branch is equipped with a check valve, a pressure reducing valve, and a mass flow controller to control the gas output flow. The hydrogen branch is equipped with a flame arrester to prevent backflow of flames. The nitrogen branch and the air branch merge downstream to form a mixing branch, and the hydrogen branch is independent; the mixing system includes a baffle-type mixing tank (15), a second solenoid valve (18), a pressure gauge (19) and a hydrogen concentration sensor (20), and the mixing branch and the hydrogen branch are connected to the front end of the mixing tank (15). The front end of the mixing tank (15) is connected to a second solenoid valve (18) that controls the timing and flow rate of the gas entering the tank. The rear end of the mixing tank (15) is connected to a hydrogen concentration sensor (20) that detects the concentration of the mixed gas. Both the front and rear ends of the mixing tank (15) are connected to a pressure sensor that monitors the change in flow resistance. The outlet of the mixing tank (15) is divided into two paths: one path is connected to a vacuum pump, and the other path is connected to a nozzle (23) via a third solenoid valve (21). The rear end of the vacuum pump (16) is connected in series with the second solenoid valve (18). The ignition system is located in the area directly in front of and above the nozzle (23), and the monitoring system is located behind the nozzle (23).

2. The test bench for studying the combustion characteristics of hydrogen according to claim 1, characterized in that, The ignition system includes a laser emitter (25), a laser ignition controller (24), and a focusing lens group (26). The laser emitter (25) and the focusing lens group (26) are fixed by a three-dimensional adjustable bracket and installed in the area directly above the nozzle (23). The laser ignition controller (24) is electrically connected to the laser emitter (25) and adjusts the single pulse energy, emission frequency, and timing of the laser emitter (25). The pulsed laser emitted by the laser emitter (25) is focused by the focusing lens group (26) onto the central region of the combustion chamber for non-contact ignition.

3. The test bench for studying the combustion characteristics of hydrogen according to claim 2, characterized in that, The laser emitter (25) is an adjustable power pulsed laser, whose ignition energy is continuously adjustable in the range of 0.1mJ-10mJ; the laser emitter (25) maintains an angle of 20°-30° with the central axis of the nozzle, and the laser is focused on the core area of ​​the mixed gas at the outlet of the nozzle (23); the laser emitter (25) is also equipped with a high-temperature resistant quartz protective cover and a metal heat shield.

4. The test bench for studying the combustion characteristics of hydrogen according to claim 1, characterized in that, The mixing tank (15) is made of 316L stainless steel and has a cross-type baffle structure inside to fully mix hydrogen and air. The mixing tank (15) is connected to the pipeline by flange or welding.

5. The test bench for studying the combustion characteristics of hydrogen according to claim 1, characterized in that, The monitoring system includes a schlieren imaging concave mirror (27), an optical schlieren (28), and an infrared thermal imager (29). The schlieren imaging concave mirror (27) and the optical schlieren (28) are arranged opposite to each other. The nozzle (23) is placed in the optimal observation area of ​​the schlieren imaging concave mirror (27) with a focal length of 1.5m. The infrared thermal imager (29) is aimed at the nozzle (23) and the area of ​​spraying and combustion, and works synchronously with the optical schlieren (28) to record the temperature field in real time.

6. The test bench for studying the combustion characteristics of hydrogen according to claim 1, characterized in that, The control unit includes a data acquisition module and a safety interlock module. The data acquisition module is connected to the mass flow controller, hydrogen concentration sensor (20), pressure gauges and monitoring system of each branch through signal lines to collect flow rate, concentration, pressure, temperature and monitoring data in real time. The safety interlock module is connected to the solenoid valve, ignition system and pressure reducing valve of each branch through control lines to automatically cut off the gas source and shut down the laser ignition system in case of overpressure, excessive concentration or abnormal temperature.

7. A method for testing hydrogen combustion characteristics based on a test bench for studying hydrogen combustion characteristics as described in any one of claims 1-6, characterized in that, Includes the following steps: Preparation phase: Install the required nozzles (23) and pipelines, and check the system's sealing and the integrity of the grounding wire and fire extinguishing device; Purge phase: Open the nitrogen branch and purge and pressure test the pipeline and mixing tank (15) three times to remove residual gas; Vacuum stage: Open the solenoid valve at the back end of the vacuum pump (16), start the vacuum pump (16), and evacuate the gas mixing system to the set pressure to eliminate residual gas; Gas mixing stage: Hydrogen and air are controlled to enter the mixing tank (15) in a set ratio by each mass flow controller and solenoid valve. The concentration of the mixed gas is monitored in real time by the hydrogen concentration sensor (20) at the back end of the mixing tank (15), and the output of the mass flow controller is dynamically adjusted to prepare the mixed gas with the target volume fraction. Monitoring phase: Start the optical schlieren (28) and infrared thermal imager (29) to simultaneously monitor flame propagation and temperature field changes; Ignition stage: The laser emitter (25) focuses the laser to the center region of the combustion chamber through the focusing lens group (26), and ignites the mixed gas with a preset energy pulse to form a stable fire core. The monitoring system continuously records the flame propagation pattern, flow field disturbance and temperature field change data. Final stage: Shut down the gas source and laser system, perform nitrogen purging and system reset to ensure the equipment is restored to a safe state.

8. The method for testing the combustion characteristics of hydrogen according to claim 7, characterized in that, The purging and pressure holding test process includes: Close all mass flow controllers and solenoid valves, open the pressure reducing valve (5) of the nitrogen tank (4), and adjust the outlet pressure to the set value; Turn on the nitrogen branch mass flow controller (11), and at the same time turn on the first solenoid valve (13) of the mixing branch, and close the second solenoid valve (18) and the third solenoid valve (21), maintain the system pressure for the preset time length, check the pipeline sealing and ensure that the gas replacement is sufficient; After the pressure holding is completed, open the third solenoid valve (21) at the tail end of the mixing tank (15) to vent the gas; Repeat the above operation 3 times to thoroughly remove residual gas and impurities from the system.

9. The method for testing the combustion characteristics of hydrogen according to claim 7, characterized in that, During the ignition stage, the single pulse energy and timing are adjusted by the laser ignition controller (24) to achieve comparable combustion tests of mixed gases of different concentrations under the same energy conditions.

10. A method for testing the combustion characteristics of hydrogen according to claim 7, characterized in that, The monitoring system obtains data on flame propagation morphology, flow field disturbance, and temperature field changes, which are synchronized in time through a data acquisition module. This data is used to construct a multidimensional data model of flame propagation speed and temperature changes, and the influence of hydrogen concentration changes on combustion characteristics is analyzed based on the multidimensional data model.

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