Combustible liquid impact hot surface atomization and ignition test system and method

Abstract

This invention relates to a system and method for testing the atomization and ignition of flammable liquids upon impact with a hot surface, belonging to the field of combustion characteristic testing technology. It overcomes the limitations of existing testing equipment in exploring critical atomization conditions and the impact of atomization degree on combustion efficiency, while also solving the problem of difficult visualization of combustion flames. The solution is as follows: the testing system includes a droplet generation component for generating single droplets with controllable particle size, and a droplet atomization and ignition component for atomization upon impact with a hot surface and subsequent ignition. The droplet generation component includes an injection pump, an adapter valve, and a coaxial needle. The droplet atomization and ignition component includes a base, a guide rod, a clamping arm, and a pneumatic ignition component. The control system is electrically connected via data cables to a control switch, injection pump, heating controller, high-speed camera, and computer at the gas cylinder outlet. Data collected using the testing system and method provided by this invention provides a basis for studying droplet atomization characteristics and combustion mechanisms.

Description

Technical Field

[0001] This invention belongs to the field of combustible liquid combustion testing technology, specifically relating to a combustible liquid impact hot surface atomization and ignition testing system and method. Background Technology

[0002] Fuel, as an important energy medium, is widely used in industrial production and public welfare sectors such as power generation, metallurgy, chemical industry, transportation, and residential heating. Various combustion devices that use fuel as a power source are typically equipped with a spray system centered around an atomizer. Its function is to break up liquid fuel into fine droplets, increasing the contact area between the fuel and air to achieve fuel diffusion, thereby creating favorable conditions for complete combustion. In actual engine spraying, droplets inevitably collide with the high-temperature internal metal walls and undergo secondary atomization. This process is crucial for promoting secondary breakdown of liquid fuel, improving air-fuel mixture quality, and enhancing overall engine performance.

[0003] Traditional experimental testing devices mostly control the formation of single droplets by the droplet's own weight, making it difficult to control droplet size and initial velocity, and only allowing for single-droplet experiments. Furthermore, they primarily focus on the diffusion of droplets after impacting a hot surface, with only a few observing the subsequent combustion process, failing to directly quantify droplet breakup and atomization parameters and combustion performance. To achieve continuous droplet ... Summary of the Invention

[0004] The main objective of this invention is to overcome the shortcomings of the prior art and provide a test system and method for atomization and ignition of combustible liquids impacting a hot surface. This invention aims to overcome the limitations of existing test equipment in exploring the effects of changing droplet landing position, acceleration, heating substrate temperature on atomization critical conditions, atomization degree, and different ignition energies on combustion efficiency. It also solves the problem of the difficulty in visually observing combustion flames.

[0005] This invention is achieved through the following technical solution: a test system for the atomization and ignition of flammable liquids upon impact with a hot surface, comprising a droplet atomization and ignition component, an injection pump, a gas cylinder, a computer, a control cabinet, and an observation component. The observation component includes a high-speed camera and an infrared thermal imager. A high-voltage power supply module is installed inside the control cabinet. The control cabinet is electrically connected to the droplet atomization and ignition component, the injection pump, a control switch at the gas cylinder outlet, the computer, the high-speed camera, and the infrared thermal imager via data cables. The control cabinet controls the injection pump, the control switch at the gas cylinder outlet, the high-speed camera, and the infrared thermal imager to turn on or off. The high-speed camera stores the collected droplet atomization level image data and flame image data in the computer, and the computer displays them through a visual interface. The droplet atomization ignition assembly includes a coaxial needle tube, a guide rod, a clamping arm, a base, and a pneumatic ignition assembly. The guide rod is vertically upward above the base, and the root of the clamping arm is movably mounted on the guide rod. The coaxial needle tube is vertically downward and detachably mounted on the end of the clamping arm. A heating substrate is fixedly mounted on the upper surface of the base and below the coaxial needle tube. The heating substrate is electrically connected to the high-voltage power supply module. The heating substrate is covered by a housing, and the front sidewall of the housing is a transparent cover plate. The lens of the high-speed camera faces the transparent cover plate. The coaxial needle tube includes an inner needle tube and an outer needle tube sleeved around the inner needle tube. The inner and outer needle tubes are coaxially arranged. The outlet of the injection pump is connected to the upper end of the inner needle tube via a pipe. The lower end of the inner needle tube extends to the top of the inner cavity of the housing. The lower end faces of the inner and outer needle tubes are flush. An annular gap is provided between the inner and outer needle tubes. An adapter valve is provided on the outside of the coaxial needle tube. One end of the adapter valve is connected to the annular gap. The gas cylinder is connected to the other end of the adapter valve and the pneumatic ignition assembly via pipes. A gas flow meter is installed on the pipe connecting the gas cylinder and the pneumatic ignition assembly. The ignition end of the pneumatic ignition assembly extends into the housing. The gas cylinder simultaneously provides the gas source for cutting the droplets and the gas source for the pneumatic ignition assembly to drive the pneumatic electrode. The liquid working fluid extruded by the injection pump forms droplets at the lower end of the inner needle tube. The gas in the annular gap cuts the droplets at the lower end and accelerates them. That is, the inner and outer needle tubes are not connected. The inner needle tube is used to transport the liquid working fluid. After the liquid working fluid forms droplets at the tube opening, it is suspended or adhered to the opening of the inner needle tube. The gas outlet of the outer needle tube is flush with the liquid outlet of the inner needle tube, providing a shearing high-pressure gas flow. When the droplet size reaches a preset value, shearing high-pressure gas is introduced into the annular gap. By controlling the gas pressure, the droplets are cut, thereby forming a controllable droplet diameter. At the same time, the gas flow accelerates the droplets, thereby controlling their speed when they reach the heating substrate.

[0006] Furthermore, a pressure sensor and a thermocouple are respectively installed on the inner wall of the housing opposite the transparent cover, and the pressure sensor and the thermocouple are electrically connected to the computer via data lines.

[0007] Furthermore, the injection pump includes a syringe, a base, a lead screw, and a sliding bracket. The lead screw is mounted horizontally on the base, and one end of the lead screw is connected to the rotor of a motor. The motor is electrically connected to a control cabinet. A nut is provided on the sliding bracket, and the sliding bracket is movably mounted on the lead screw through a lead screw-nut structure. The syringe stores a liquid working medium for the droplet atomization combustion experiment. The syringe sleeve is detachably clamped onto the base. The piston rod of the syringe approaches the sliding bracket. The motor drives the lead screw to rotate, which in turn drives the nut to move the sliding bracket along the lead screw in a straight line. During the sliding process, the sliding bracket squeezes the piston rod, squeezing the liquid working medium stored in the sleeve out of the syringe.

[0008] Furthermore, the pneumatic ignition assembly includes an electrode base and a pneumatic electrode. The electrode base is disposed on the upper surface of the base and symmetrically disposed on the left and right side walls of the housing. The pneumatic electrode is respectively installed on the corresponding electrode base. The pneumatic electrode is electrically connected to the high-voltage power supply module through a high-voltage circuit cable, and the ignition end of the pneumatic electrode extends into the interior of the housing. An air inlet is provided in the middle of the pneumatic electrode, and a pneumatic electrode drive tube is provided at the air inlet position of the pneumatic electrode. The pneumatic electrode drive tube is connected to the gas cylinder through a pipe.

[0009] Furthermore, the lower end of the inner needle tube is set as a flat opening, and the lower end of the outer needle tube is set as an inverted trumpet shape.

[0010] Furthermore, the high-speed camera is a high-speed CCD camera.

[0011] Furthermore, the control cabinet integrates an electrically connected PLC module, a grounding module, and a communication module, all of which are electrically connected to the high-voltage power supply module.

[0012] The test method for testing the atomization and ignition of flammable liquids upon impact with a hot surface using the test system described above includes the following steps: S1. Installation and inspection of the test system: The test system is assembled in sequence, the gas supply line and control line are installed, and the overall test system is installed and debugged. S2. Parameter Settings: First, adjust the height of the coaxial syringe according to the droplet size to be observed, and control the heating plate to heat to the predetermined temperature and maintain stability through the control cabinet; then, open the control switch at the gas cylinder outlet through the control cabinet, adjust the gas pressure to the predetermined value, and keep the adapter valve in standby state; finally, adjust the injection rate of the injection pump and the flow rate of the gas delivered from the gas cylinder to the coaxial syringe according to the required droplet size and the speed when it reaches the heating plate, and open the pressure sensor and thermocouple through the control cabinet to collect data; S3. Adjust the observation components: Start the high-speed camera and infrared thermal imager, and adjust the shooting position, focal length, and aperture of the high-speed camera and infrared thermal imager; S4. Set experimental parameters: Enter the experimental parameters and save them as a configuration file. Then, click the "Single Experiment" or "Start Sequence" button to perform the following steps: S4-1. Preparation: Check if the heating temperature of the heating substrate is within the set tolerance range. If yes, continue to the next step; if not, the test system will alarm and pause. S4-2, Droplet Generation and Release: The injection pump is controlled by the control cabinet to perform single or continuous injection, forming a suspended droplet at the inner needle position; after the injection pump stops, the control cabinet issues a command to open the adapter valve to introduce high-speed airflow. When the droplet grows to the point that the resultant force of gravity, inertia, and air pressure is greater than the surface tension of the droplet, the suspended single droplet falls off from the inner needle at a predetermined time. S4-3, Impact Recording: When the adapter valve is opened, the high-speed camera and infrared thermal imager are triggered simultaneously. The high-speed camera and infrared thermal imager record the complete process from the droplet's flight to its impact on the heated substrate. S4-4, Ignition and Flame Recording: At the same time as the droplet impacts the heating substrate and atomizes, or within a set delay, the pneumatic ignition component is extended and ignited. The high-speed camera and infrared thermal imager continuously record the entire process of the flame from ignition to full development and change. S4-5. Data saving: Package the original video file, time series data of all sensors, intermediate results of image processing, judgment results, and all experimental parameters, name the packaged file with the corresponding "experiment number", and save it to the specified hard disk directory. S5. The system status is restored to "Ready" and awaits the next experimental instruction; S6. Device Cleaning: After returning the pneumatic electrodes to their original positions, release the remaining static electricity in the capacitors, and then clean the residual droplets on the test system. After the experiment, turn off the power, disassemble the cleaning system and clean each component for the next cycle.

[0013] The beneficial effects of this invention are as follows: This invention adjusts the position of the coaxial needle and controls the air pressure to form a controllable droplet diameter and speed at which it reaches the heating substrate, and uses a high-speed camera to capture images of the droplets after they impact the heating substrate.

[0014] In summary, this invention can form single droplets of different diameters and velocities and atomize and ignite them. It can obtain the degree of atomization and the development and changes of ignition after droplet atomization. It has the advantages of strong functionality, system integration, simple operation, and safe and reliable experimental process. The collected data can promote the study of droplet atomization characteristics and mechanism and provide data support for the combustion mechanism of droplets with different atomization degrees. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the droplet atomizing ignition assembly. Figure 3 This is a schematic diagram of the assembly structure of the coaxial needle tube and the adapter valve. Figure 4 This is a schematic diagram of an injection pump.

[0016] In the diagram, 1 is the droplet atomizing ignition assembly, 2 is the injection pump, 3 is the gas cylinder, 4 is the gas flow meter, 5 is the computer, 6 is the control cabinet, 7 is the high-speed camera, and 8 is the infrared thermal imager. 101 is a transparent cover plate, 102 is a housing, 103 is a pressure sensor, 104 is a thermocouple, 109 is a heating base plate, 110 is a pneumatic ignition assembly, 105 is a coaxial needle tube, 106 is a guide rod, 107 is a clamping arm, 108 is a base, 111 is an adapter valve, 112 is an inner needle tube, and 113 is an outer needle tube. 201 is the syringe, 202 is the base, 203 is the lead screw, and 204 is the sliding support. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0018] like Figures 1 to 4 The test system shown demonstrates the atomization and ignition of flammable liquids upon impact with a hot surface. A test system for the atomization and ignition of flammable liquids upon impact with a hot surface includes a droplet atomization and ignition assembly 1, an injection pump 2, a gas cylinder 3, a computer 5, a control cabinet 6, and an observation assembly. The observation assembly includes a high-speed camera 7 and an infrared thermal imager 8. The control cabinet 6 is equipped with a high-voltage power supply module. The control cabinet 6 is electrically connected to the droplet atomization and ignition assembly 1, the injection pump 2, the control switches at the gas cylinder 3 outlet, the computer 5, the high-speed camera 7, and the infrared thermal imager 8 via data cables. The control cabinet 6 controls the control switches at the injection pump 2 and the gas cylinder 3 outlet, the high-speed camera 7, and the infrared thermal imager 8 to turn on or off. The high-speed camera 7 stores the collected droplet atomization level image data and flame image data in the computer 5, and the computer 5 displays them through a visual interface. The droplet atomizing ignition assembly 1 includes a coaxial needle tube 105, a guide rod 106, a clamping arm 107, a base 108, and a pneumatic ignition assembly 110. The guide rod 106 is vertically upward above the base 108, the root of the clamping arm 107 is movably mounted on the guide rod 106, and the coaxial needle tube 105 is vertically downward detachably mounted on the end of the clamping arm 107. A heating substrate 109 is fixedly mounted on the upper surface of the base 108 and below the coaxial needle tube 105. The heating substrate 109 is electrically connected to the high-voltage power supply module. The heating substrate 109 is covered by a housing 102, and the front sidewall of the housing 102 is a transparent cover plate 101. The lens of the high-speed camera 7 faces the transparent cover plate 101. The coaxial needle tube 105 includes an inner needle tube 112 and an outer needle tube 113 sleeved around the inner needle tube 112. The inner needle tube 112 and the outer needle tube 113 are coaxially arranged. The outlet of the injection pump 2 is connected to the upper end of the inner needle tube 112 through a pipe. The lower end of the inner needle tube 112 extends to the top of the inner cavity of the housing 102. The lower end faces of the inner needle tube 112 and the outer needle tube 113 are flush. An annular gap is provided between the inner needle tube 112 and the outer needle tube 113. A converter valve 111 is provided on the outside of the coaxial needle tube 105. One end of the converter valve 111 is connected to the annular gap. The gas cylinder 3 is connected to the converter valve 111 through pipes. The other end is connected to the pneumatic ignition assembly 110, and a gas flow meter 4 is installed on the pipe connecting the gas cylinder 3 and the pneumatic ignition assembly 110. The ignition end of the pneumatic ignition assembly 110 extends into the housing 102. The gas cylinder provides both the gas source for cutting the droplets and the gas source for the pneumatic ignition assembly 110 to drive the pneumatic electrode. The liquid working medium squeezed out by the injection pump 2 forms droplets at the lower end of the inner needle tube 112. The gas in the annular gap cuts the droplets at the lower end and accelerates the droplets. That is, the inner and outer needle tubes are not connected. The inner needle tube is used to transport the liquid working medium. After the liquid working medium forms droplets at the tube opening, it is suspended or adhered to the position of the inner needle tube opening. The air outlet of the outer needle tube is flush with the liquid outlet of the inner needle tube, providing a shearing high-pressure airflow. When the droplet size reaches the preset value, shearing high-pressure gas is introduced into the annular gap. The droplet can be cut by controlling the gas pressure, thereby forming a controllable droplet diameter. At the same time, the airflow gives the droplet an acceleration effect, thereby controlling the speed when it reaches the heating substrate.

[0019] Furthermore, a pressure sensor 103 and a thermocouple 104 are respectively installed on the inner wall of the housing 102 opposite to the transparent cover plate 101. The pressure sensor 103 and the thermocouple 104 are electrically connected to the computer 5 via data cables.

[0020] Further, the injection pump 2 includes a syringe 201, a base 202, a lead screw 203, and a sliding bracket 204. The lead screw 203 is mounted horizontally on the base 202, and one end of the lead screw 203 is connected to the rotor of the motor. The motor is electrically connected to the control cabinet 6. A nut is provided on the sliding bracket 204, and the sliding bracket 204 is movably mounted on the lead screw 203 through a lead screw-nut structure. The syringe 201 stores the liquid working medium for the droplet atomization combustion experiment. The sleeve of the syringe 201 is detachably clamped on the base 202. The piston rod of the syringe 201 approaches the sliding bracket 204. The motor drives the lead screw 203 to rotate, which in turn drives the nut to drive the sliding bracket 204 to slide linearly along the lead screw 203. During the sliding process, the sliding bracket 204 squeezes the piston rod, squeezing the liquid working medium stored in the sleeve out of the syringe 201.

[0021] Furthermore, the pneumatic ignition assembly 110 includes an electrode base and a pneumatic electrode. The electrode base is disposed on the upper surface of the base 108 and symmetrically disposed on the left and right side walls of the housing 102. The pneumatic electrodes are respectively installed on the corresponding electrode bases. The pneumatic electrodes are electrically connected to the high-voltage power supply module through high-voltage circuit cables, and the ignition end of the pneumatic electrode extends into the interior of the housing 102. An air inlet is provided in the middle of the pneumatic electrode, and a pneumatic electrode drive tube is provided at the air inlet position of the pneumatic electrode. The pneumatic electrode drive tube is connected to the gas cylinder 3 through a pipe.

[0022] Furthermore, the lower end of the inner needle tube 112 is set as a flat opening, and the lower end of the outer needle tube 113 is set as an inverted trumpet shape.

[0023] Furthermore, the high-speed camera 7 is a high-speed CCD camera.

[0024] Furthermore, the control cabinet 6 integrates an electrically connected PLC module, a grounding module, and a communication module, all of which are electrically connected to the high-voltage power supply module.

[0025] The test method for testing the atomization and ignition of flammable liquids upon impact with a hot surface using the test system described above includes the following steps: S1. Installation and inspection of the test system: The test system is assembled in sequence, the gas supply line and control line are installed, and the overall test system is installed and debugged. S2. Parameter Setting: First, adjust the height of the coaxial syringe 105 according to the particle size of the droplet to be observed, and control the heating substrate 109 to be heated to the predetermined temperature and kept stable through the control cabinet 6; then, open the control switch at the outlet of the gas cylinder 3 through the control cabinet 6, adjust the gas pressure to the predetermined value, and then open the valve of the adapter valve 111; finally, adjust the injection rate of the injection pump 2 and the flow rate of the gas delivered from the gas cylinder 3 to the coaxial syringe 105 according to the required particle size of the droplet to be detected and the speed when it reaches the heating substrate 109, and open the pressure sensor 103 and thermocouple 104 through the control cabinet 6 to collect data; S3. Adjust the observation components: Start the high-speed camera 7 and the infrared thermal imager 8, and adjust the shooting position, focal length, and aperture of the high-speed camera 7 and the infrared thermal imager 8. S4. Set experimental parameters: Enter the experimental parameters and save them as a configuration file. Then, click the "Single Experiment" or "Start Sequence" button to perform the following steps: S4-1. Preparation: Check if the heating temperature of the heating substrate 109 is within the set tolerance range. If yes, continue with the next steps; if not, the test system will alarm and pause. S4-2, Droplet generation and release: The injection pump 2 is controlled by the control cabinet 6 to perform single or continuous injection, forming a suspended droplet at the position of the inner needle tube 112; after the injection pump 2 stops injecting, the gas cylinder 3 is opened. When the droplet grows to the point that the resultant force of gravity, inertia and gas pressure is greater than the surface tension of the droplet, the suspended single droplet falls off from the inner needle tube 112 at a predetermined time. S4-3, Impact Recording: When the adapter valve 111 is opened, the high-speed camera 7 and the infrared thermal imager 8 are triggered simultaneously. The high-speed camera 7 and the infrared thermal imager 8 record the complete process from the droplet's flight to its impact on the heated substrate 109. S4-4, Ignition and Flame Recording: At the same time as the droplet impacts the heating substrate and atomizes, or within a set delay, the pneumatic ignition component 110 is extended and ignited, and the high-speed camera 7 and infrared thermal imager 8 continuously record the entire process of the flame from never being ignited to fully developing and changing. S4-5. Data saving: Package the original video file, time series data of all sensors, intermediate results of image processing, judgment results, and all experimental parameters, name the packaged file with the corresponding "experiment number", and save it to the specified hard disk directory. S5. The system status is restored to "Ready" and awaits the next experimental instruction; S6. Device Cleaning: After returning the pneumatic electrodes to their original positions, release the remaining static electricity in the capacitors, and then clean the residual droplets on the test system. After the experiment, turn off the power, disassemble the cleaning system and clean each component for the next cycle.

[0026] The primary technical advantage of this invention lies in filling the gap in the research on the entire process of "impact-atomization-ignition" of flammable liquids. Traditional testing devices often only focus on the breakup and evaporation of droplets after colliding with a hot surface, lacking in-depth exploration of the subsequent ignition and activation process. This system innovatively introduces an independent autonomous ignition system, capable of comprehensively observing and analyzing the ignition and development process after droplets collide with a hot surface and undergo atomization. This allows researchers not only to explore the critical conditions for atomization but also to further systematically analyze the specific impact of ignition energy on the combustion characteristics of different atomization levels during droplet breakup, greatly expanding the depth of research on droplet atomization combustion mechanisms.

[0027] Secondly, this system achieves a key technological breakthrough in droplet generation and precise control. Existing testing equipment mostly relies on the droplet's own weight to fall, making it difficult to control the droplet size and initial velocity, and typically only allows for single-droplet experiments. This invention employs a self-designed coaxial needle tube and inner and outer ring coordinated droplet injector system. The droplet size is controlled by an injection pump, while a high-pressure axial airflow is applied downwards through the outer tube to cut the droplet and impart downward acceleration. This design not only precisely controls the droplet diameter and impact velocity on the substrate, but also allows for flexible formation of single droplets or continuously controllable droplet flows by adjusting the relevant parameters of the gas and liquid source components. This innovation enables the device to better simulate the diverse droplet impact conditions present in actual industrial applications, making its applicability and research scope wider than traditional methods.

[0028] Finally, this invention constructs a multi-dimensional, visualized comprehensive observation and data acquisition system, significantly enhancing the scientific research value of the data. Traditional methods are mostly limited to observing the physical dispersion of droplets upon impact with a hot surface, making it difficult to directly quantify combustion performance. This system focuses on in-depth observation of the entire flame and combustion process, equipped with a professional high-speed camera and infrared thermal imager, enabling non-contact, visualized measurement of the atomization and temperature field distribution characteristics. Simultaneously, combined with a pressure sensor mounted on the transparent shell and a professional image analysis system, researchers can intuitively obtain key information such as droplet size distribution, trajectory, total specific surface area, evaporation rate, and flame morphology evolution. These rich observation methods effectively solve the problem of the difficulty in visually observing combustion flames, providing solid data support for a comprehensive analysis of the entire combustion process of combustible droplets after breaking and atomizing on a heated metal wall.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A test system for the atomization and ignition of flammable liquids upon impact with a hot surface, comprising a droplet atomization and ignition assembly, an injection pump, a gas cylinder, a computer, a control cabinet, and an observation assembly, wherein the observation assembly includes a high-speed camera and an infrared thermal imager, and the control cabinet is equipped with a high-voltage power supply module, characterized in that, The control cabinet is electrically connected to the droplet atomization ignition assembly, the injection pump, the control switch at the gas cylinder outlet, the computer, the high-speed camera, and the infrared thermal imager via data cables. The control cabinet controls the injection pump, the control switch at the gas cylinder outlet, the high-speed camera, and the infrared thermal imager to turn on or off. The high-speed camera stores the collected droplet atomization level image data and flame image data in the computer, and the computer displays them through a visual interface. The droplet atomization ignition assembly includes a coaxial needle tube, a guide rod, a clamping arm, a base, and a pneumatic ignition assembly. The guide rod is vertically upward above the base, and the root of the clamping arm is movably mounted on the guide rod. The coaxial needle tube is vertically downward and detachably mounted on the end of the clamping arm. A heating substrate is fixedly mounted on the upper surface of the base and below the coaxial needle tube. The heating substrate is electrically connected to the high-voltage power supply module. The heating substrate is covered by a housing, and the front sidewall of the housing is a transparent cover plate. The lens of the high-speed camera faces the transparent cover plate. The coaxial needle tube includes an inner needle tube and an outer needle tube sleeved outside the inner needle tube. The inner and outer needle tubes are coaxially arranged. The outlet of the injection pump is connected to the upper end of the inner needle tube through a pipe. The lower end of the inner needle tube extends to the top of the inner cavity of the housing. The lower end faces of the inner and outer needle tubes are flush. An annular gap is provided between the inner and outer needle tubes. An adapter valve is provided outside the coaxial needle tube. One end of the adapter valve is connected to the annular gap. The gas cylinder is connected to the other end of the adapter valve and the pneumatic ignition assembly through pipes. A gas flow meter is provided on the pipe connecting the gas cylinder and the pneumatic ignition assembly. The ignition end of the pneumatic ignition assembly extends into the housing. The pneumatic ignition assembly includes an electrode base and a pneumatic electrode. The ignition end of the pneumatic electrode extends into the interior of the housing. An air inlet is provided in the middle of the pneumatic electrode. A pneumatic electrode drive tube is provided at the air inlet position of the pneumatic electrode. The pneumatic electrode drive tube is connected to the gas cylinder through a pipe. The injection pump includes a syringe, a base, a lead screw, and a sliding bracket. The lead screw is mounted horizontally on the base, and one end of the lead screw is connected to the rotor of a motor. The motor is electrically connected to a control cabinet. A nut is installed on the sliding bracket, and the sliding bracket is movably mounted on the lead screw via a lead screw-nut structure. The syringe stores a liquid working medium for the droplet atomization combustion experiment. The syringe sleeve is detachably clamped onto the base. The piston rod of the syringe is close to the sliding bracket. The motor drives the lead screw to rotate, which in turn drives the nut to move the sliding bracket along the lead screw in a straight line. During the sliding process, the sliding bracket squeezes the piston rod, squeezing the liquid working medium stored in the sleeve out of the syringe.

2. The test system for atomization and ignition of flammable liquids upon impact with a hot surface according to claim 1, characterized in that: Pressure sensors and thermocouples are respectively installed on the inner walls of the housing opposite the transparent cover. The pressure sensors and thermocouples are electrically connected to the computer via data cables.

3. The test system for the atomization and ignition of flammable liquids upon impact with a hot surface according to claim 1, characterized in that: The electrode holders are disposed on the upper surface of the base and symmetrically arranged on the left and right side walls of the housing. The pneumatic electrodes are respectively installed on the corresponding electrode holders and are electrically connected to the high-voltage power supply module through high-voltage circuit cables.

4. The test system for atomization and ignition of flammable liquids upon impact with a hot surface according to claim 1, characterized in that: The lower end of the inner needle tube is set as a flat opening, while the lower end of the outer needle tube is set as an inverted trumpet shape.

5. The test system for the atomization and ignition of flammable liquids upon impact with a hot surface according to claim 1, characterized in that: The high-speed camera is a high-speed CCD camera.

6. The test system for the atomization and ignition of flammable liquids upon impact with a hot surface according to claim 1, characterized in that: The control cabinet integrates an electrically connected PLC module, a grounding module, and a communication module, all of which are electrically connected to a high-voltage power supply module.

7. A method for testing the atomization and ignition of flammable liquids upon impact with a hot surface using the testing system described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Installation and inspection of the test system: The test system is assembled in sequence, the gas supply line and control line are installed, and the overall test system is installed and debugged. S2. Parameter Settings: First, adjust the height of the coaxial syringe according to the droplet size to be observed, and control the heating plate to heat to the predetermined temperature and maintain stability through the control cabinet; then, open the control switch at the gas cylinder outlet through the control cabinet, adjust the gas pressure to the predetermined value, and keep the adapter valve in standby state; finally, adjust the injection rate of the injection pump and the flow rate of the gas delivered from the gas cylinder to the coaxial syringe according to the required droplet size and the speed when it reaches the heating plate, and open the pressure sensor and thermocouple through the control cabinet to collect data; S3. Adjust the observation components: Start the high-speed camera and infrared thermal imager, and adjust the shooting position, focal length, and aperture of the high-speed camera and infrared thermal imager; S4. Set experimental parameters: Enter the experimental parameters and save them as a configuration file. Then, click the "Single Experiment" or "Start Sequence" button to perform the following steps: S4-1. Preparation: Check if the heating temperature of the heating substrate is within the set tolerance range. If yes, continue to the next step; if not, the test system will alarm and pause. S4-2, Droplet Generation and Release: The injection pump is controlled by the control cabinet to perform single or continuous injection, forming a suspended droplet at the inner needle position; after the injection pump stops, the control cabinet issues a command to open the adapter valve to introduce high-speed airflow. When the droplet grows to the point that the resultant force of gravity, inertia, and air pressure is greater than the surface tension of the droplet, the suspended single droplet falls off from the inner needle at a predetermined time. S4-3, Impact Recording: When the adapter valve is opened, the high-speed camera and infrared thermal imager are triggered simultaneously. The high-speed camera and infrared thermal imager record the complete process from the droplet's flight to its impact on the heated substrate. S4-4, Ignition and Flame Recording: At the same time as the droplet impacts the heating substrate and atomizes, or within a set delay, the pneumatic ignition component is extended and ignited. The high-speed camera and infrared thermal imager continuously record the entire process of the flame from ignition to full development and change. S4-5. Data saving: Package the original video file, time series data of all sensors, intermediate results of image processing, judgment results, and all experimental parameters, name the packaged file with the corresponding "experiment number", and save it to the specified hard disk directory. S5. The system status is restored to "Ready" and awaits the next experimental instruction; S6. Device Cleaning: After returning the pneumatic electrodes to their original positions, release the remaining static electricity in the capacitors, and then clean the residual droplets on the test system. After the experiment, turn off the power, disassemble the cleaning system and clean each component for the next cycle.

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