Controllable flow tracer particle generating device for PIV (particle image velocimetry) measurement

Abstract

The invention relates to the technical field of fluid measurement, and discloses a flow-controllable tracer particle generating device for PIV (particle image velocimetry) measurement, which comprises a mixing bin assembly, a tracer particle generating assembly, a flow control assembly, a concentration monitoring and feedback control assembly and an electrostatic synergistic assembly, the mixing bin assembly is composed of a first pneumatic quick connector, a second pneumatic quick connector, a mixing bin top plate, a mixing bin shell, a mixing bin bottom plate, a liquid discharging hole, a third pneumatic quick connector, a manual valve, a liquid collecting cup, an atomizer hole and an air outlet hole. The tracer particle generating assembly is composed of an atomizer body, a hose and an injection pump. The flow control and concentration monitoring feedback system is integrated, so that the gas flow and the particle concentration are synergistically and accurately regulated and controlled. The system can monitor the concentration of particles in the mixing bin in real time and intelligently adjust the speed of the injection pump, the stability of a particle field needed by PIV measurement is guaranteed from the source, and the problem of measurement errors caused by parameter fluctuation of a traditional device is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of fluid measurement technology, specifically to a controllable flow tracer particle generator for PIV measurement. Background Technology

[0002] Particle image velocimetry (PIV), as a non-contact flow field diagnostic method, plays an important role in combustion flow field research. Existing technologies, tracer particle generators suitable for large-scale flow field measurements typically have large volumes and flow rates, making them difficult to directly adapt to low-flow combustion environments, such as opposed flame and Bunsen burner experimental scenarios. These small burners require precisely controllable and low-value gas flow rates entering the combustion zone. Traditional particle generators, under these conditions, not only struggle to achieve accurate flow rate matching but also lack effective means of monitoring and controlling tracer particle concentration.

[0003] In practical applications, existing devices generally suffer from a key problem: they cannot simultaneously and precisely control the gas flow rate while also performing real-time monitoring and closed-loop feedback control of the tracer particle concentration within the mixing chamber. Fluctuations in gas flow rate or instability in particle concentration directly alter the number and distribution of effective tracer particles in the PIV measurement image, introducing systematic errors in velocity field measurement and severely impacting data accuracy and repeatability. Therefore, there is an urgent need for a generator capable of synergistically controlling gas flow rate and particle concentration to fundamentally ensure the reliability of PIV measurements in low-flow combustion fields. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a controllable flow tracer particle generator for PIV measurement, which solves the problem that existing devices cannot accurately control gas flow while simultaneously monitoring and controlling the tracer particle concentration in real time and implementing closed-loop feedback control, resulting in poor accuracy and repeatability of PIV measurement results.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a controllable flow tracer particle generator for PIV measurement, comprising a mixing chamber assembly, a tracer particle generator assembly, a flow control assembly, a concentration monitoring and feedback control assembly, and an electrostatic enhancement assembly. The mixing chamber assembly consists of a first pneumatic quick connector, a second pneumatic quick connector, a mixing chamber top plate, a mixing chamber outer shell, a mixing chamber bottom plate, a drain hole, a third pneumatic quick connector, a manual valve, a collection cup, an air inlet, an atomizer hole, and an air outlet. The tracer particle generator assembly consists of an atomizer body, a hose, and a syringe pump. The flow control assembly consists of a computer, a gas pipeline, a first mass flow controller, a second mass flow controller, a pressure reducing valve, and a gas cylinder.

[0006] By adopting the above technical solution, this invention achieves precise dual control of gas flow rate and particle concentration: on the one hand, the computer coordinates the control of two mass flow controllers to ensure that the total gas flow rate entering the system precisely matches the requirements of a small-flow combustion field; on the other hand, a concentration monitoring system based on laser transmission method senses the particle state in the mixing chamber in real time and dynamically adjusts the propulsion speed of the injection pump through an intelligent feedback mechanism. This coordinated control of flow rate and concentration ensures the stability and consistency of the particle field required for PIV measurement from the source, effectively solving the measurement error problem caused by parameter fluctuations in traditional devices.

[0007] Preferably, the mixing chamber body consists of a mixing chamber top plate, a mixing chamber outer shell, and a mixing chamber bottom plate, and is made of acrylic material. It is assembled by adhesive bonding and is used to directly observe the degree of atomization from the outside.

[0008] Preferably, the air inlet, atomizer hole, and air outlet on the top plate of the mixing chamber are used to house the first pneumatic quick connector, the atomizer body, and the second pneumatic quick connector, respectively; the air inlet and air outlet are threaded.

[0009] Preferably, the bottom plate of the mixing chamber has a drain hole for accommodating a third pneumatic quick connector, and the drain hole has threads.

[0010] Preferably, the second pneumatic quick connector is connected to the burner device for outputting a variable flow rate gas with tracer particles.

[0011] Preferably, the injection pump is connected to the liquid inlet of the atomizer body via a hose; the first mass flow controller is connected to the air inlet of the atomizer body via an air passage.

[0012] Preferably, the computer controls the gas flow of the first mass flow controller and the second mass flow controller through supporting software.

[0013] Preferably, the droplets sprayed from the atomizer body remain in the mixing chamber due to impact with the container wall, and are eventually discharged through the air passage connected to the third pneumatic quick connector installed in the drain hole, and collected by the collection cup; a manual valve is installed on the air passage connected to the third pneumatic quick connector to control the discharge of waste liquid.

[0014] Preferably, the concentration monitoring and feedback control component consists of a laser incident window, a transmitted light receiving window, a micro laser, and a photodetector disposed on the outer shell of the mixing chamber, and is used to monitor the concentration of tracer particles in the mixing chamber in real time and to control the propulsion speed of the injection pump.

[0015] Preferably, the electrostatic enhancement component consists of a Venturi-porous plate composite mixer, an upper electrode ring, and a lower electrode ring disposed inside the mixing chamber, used to improve particle dispersion and distribution uniformity.

[0016] Working principle: First, the gas source equipment is started. After the internal gas is depressurized and stabilized, it is delivered in two streams through pipelines. The computer, with the help of supporting software, precisely controls the flow rate of the two gas streams. One stream is directed to the atomizing component to provide power for particle atomization, while the other stream is directly sent to the mixing chamber to lay the flow foundation for subsequent particle mixing. At the same time, the injection pump stably delivers the tracer particle liquid to the liquid inlet of the atomizing component through a hose. Under the synergistic effect of gas power and liquid supply, the atomizing component atomizes the liquid into tiny particles that meet the requirements of PIV measurement.

[0017] The atomized particles and another stream of gas enter the mixing chamber through corresponding openings in the top plate. The mixing chamber is constructed of highly transparent material, allowing researchers to directly observe the atomization state and mixing process from the outside, facilitating timely adjustments to relevant parameters. After entering the mixing chamber, the gas and particles first flow through a composite mixer. This mixer, with its special structure, accelerates the airflow to create a low-pressure zone, attracting and ejecting the particles for initial mixing. Subsequently, the airflow is dispersed into multiple micro-jets, completing a secondary mixing process with the particles. Simultaneously, the electrode rings on the inner wall of the mixing chamber, in conjunction with an external high-voltage power supply, can switch operating modes according to experimental needs. Electrostatic action breaks up particle agglomeration, guiding particles to a uniform distribution and further enhancing the mixing effect.

[0018] During particle mixing, the concentration monitoring component operates synchronously. A stable laser beam is continuously emitted from the laser emitting component through an optical window on the mixing chamber's outer shell. This beam penetrates the particle-containing airflow and is captured by the receiving component. The receiving component converts the optical signal into an electrical signal and transmits it to the computer. The computer uses a built-in algorithm to calculate the real-time particle concentration based on the light intensity attenuation. If the concentration deviates from the set value, the computer immediately adjusts the injection pump's speed. If the concentration is too high, the liquid supply is reduced; if the concentration is too low, the liquid output is increased, ensuring that the particle concentration within the chamber remains stable within the optimal measurement range.

[0019] During the experiment, some atomized particles may remain after impacting the chamber wall. This waste liquid will naturally collect at the bottom of the chamber and be discharged through the drainage structure and supporting pipelines at the bottom of the chamber. It will then be collected by the collection component. The experimenters can flexibly control the timing of waste liquid discharge through manual valves to avoid waste liquid accumulation that could contaminate the chamber or affect the continuity of the experiment. Finally, the uniformly mixed, stable-concentration gas containing tracer particles is delivered to the burner equipment through a special connection component, providing a stable and reliable particle field for PIV measurement of low-flow combustion flow field, ensuring the accuracy of flow field velocity measurement and experimental repeatability.

[0020] This invention provides a controllable flow tracer particle generator for PIV measurement. It has the following advantages: 1. This invention achieves precise metering and active regulation of the gas supply to a low-flow combustion field through an integrated flow control component. A computer independently controls two mass flow controllers via accompanying software, enabling precise setting and maintenance of the gas flow rate entering the mixing chamber and atomizer. This not only ensures a stable and known total gas flow rate supplied to the burner, providing a reliable basis for accurately calculating the fuel-air equivalence ratio, but also fundamentally solves the key problem of inaccurate low-flow combustion experimental conditions caused by the uncontrollable and unknowable flow rate in traditional devices.

[0021] 2. This invention constructs a closed-loop stabilization system for tracer particle concentration by introducing concentration monitoring and feedback control components. This system senses the particle concentration within the mixing chamber in real time based on the laser transmission principle and intelligently adjusts the injection pump's propulsion speed accordingly. This dynamic feedback mechanism automatically maintains the particle concentration within the optimal range required for PIV measurement, effectively avoiding overly dense or sparse images caused by concentration fluctuations, thereby ensuring the reliability and repeatability of velocity field data.

[0022] 3. This invention optimizes the particle field distribution quality through an electrostatic enhancement component. The composite mixer, with its venturi tube and perforated plate structure, primarily functions to homogenize and guide the main airflow, promoting smooth and uniform mixing of the airflow and particles. Combined with a programmable electrostatic field, this component effectively suppresses particle aggregation tendencies and improves the uniformity of their spatial distribution. This synergistic effect provides a more dispersed and rationally distributed tracer particle field for PIV measurements. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a controllable flow tracer particle generator for PIV measurement according to the present invention. Figure 2 This is a schematic diagram of the mixing silo top plate and mixing silo bottom plate of the present invention; Figure 3 This is a schematic diagram of the outer shell of the mixing chamber of the present invention; Figure 4 This is a schematic diagram of the composite mixer of the present invention; Figure 5 This is a schematic diagram of the lower electrode ring of the present invention.

[0024] The components include: 1. Computer; 2. Gas pipeline; 3. First mass flow controller; 4. Second mass flow controller; 5. First pneumatic quick connector; 6. Second pneumatic quick connector; 7. Mixing chamber top plate; 8. Atomizer body; 9. Mixing chamber outer shell; 10. Mixing chamber bottom plate; 11. Drain hole; 12. Third pneumatic quick connector; 13. Manual valve; 14. Collection cup; 15. Hoses; 16. Injection pump; 17. Pressure reducing valve; 18. Gas cylinder; 19. Air inlet; 20. Atomizer hole; 21. Air outlet; 22. Laser entrance window; 23. Transmitted light receiving window; 24. Miniature laser; 25. Photodetector; 26. Composite mixer; 27. Upper electrode ring; 28. Lower electrode ring. Detailed Implementation

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

[0026] Please see the appendix Figure 1 and attached Figure 2 This invention provides a controllable flow tracer particle generator for PIV measurement, comprising a mixing chamber assembly, a tracer particle generator assembly, a flow control assembly, a concentration monitoring and feedback control assembly, and an electrostatic enhancement assembly. The mixing chamber assembly consists of a first pneumatic quick connector 5, a second pneumatic quick connector 6, a mixing chamber top plate 7, a mixing chamber outer shell 9, a mixing chamber bottom plate 10, a drain hole 11, a third pneumatic quick connector 12, a manual valve 13, a collection cup 14, an air inlet 19, an atomizer hole 20, and an air outlet 21. The tracer particle generator assembly consists of an atomizer body 8, a hose 15, and a syringe pump 16. The flow control assembly consists of a computer 1, a gas pipeline 2, a first mass flow controller 3, a second mass flow controller 4, a pressure reducing valve 17, and a gas cylinder 18.

[0027] Specifically, in the device's workflow, gas cylinder 18 is first opened. The gas inside cylinder 18 is then depressurized and stabilized by pressure reducing valve 17, and then transported via gas pipeline 2 to the first mass flow controller 3 and the second mass flow controller 4. At this time, computer 1 sets and controls the gas flow rates of the first mass flow controller 3 and the second mass flow controller 4 through supporting software. Through the coordinated action of these components, the gas flow rates entering the mixing chamber and atomizer are precisely controlled, thereby adapting to the requirements of a low-flow combustion flow field and avoiding the impact of excessive or unstable flow rates on the accuracy of PIV measurements. This also provides a basis for subsequent control of the mixing rate of tracer particles and gas. After the flow control component is activated, the injection pump 16 stably delivers the tracer particle liquid to the liquid inlet of the atomizer body 8 through the hose 15. At the same time, the first mass flow controller 3 delivers gas to the gas inlet of the atomizer body 8 through the gas pipeline 2, providing power for the atomization process. Through the precise control of the liquid inlet by the injection pump 16 and the atomization of the liquid into tiny particles by the atomizer body 8, the tracer particles that meet the requirements of PIV measurement are continuously generated, thereby avoiding uneven particle size or unstable output. This ensures the effectiveness of the basic conditions for particle distribution in the subsequent flow field and provides a particle source guarantee for subsequent adjustments to particle placement speed and density. The tracer particles generated by the atomizer body 8 and the gas delivered by the first mass flow controller 3 enter the mixing chamber through the atomizer hole 20 and the air inlet 19 on the mixing chamber top plate 7, respectively, and the first pneumatic quick connector 5 installed on the air inlet 19. Inside the mixing chamber, after the gas and tracer particles are fully mixed, it is delivered to the burner device through the second pneumatic quick connector 6 on the air outlet 21 of the mixing chamber top plate 7, while the drain hole 1 on the mixing chamber bottom plate 10... 1. The third pneumatic quick connector 12 and manual valve 13 are provided. During the experiment, the manual valve 13 can be opened to guide the droplets remaining after the atomizer body 8 hits the chamber wall and are collected in the collection cup 14. Through the division of labor of each component of the mixing chamber assembly, it plays the role of accommodating the gas and tracer particles, guiding the gas flow output after mixing, and recovering waste liquid. This ensures that the particles and gas are mixed evenly, avoids waste liquid from contaminating the device and affecting the continuity of the experiment, and facilitates the observation of the atomization mixing situation with the acrylic mixing chamber shell 9. This provides a direct basis for timely adjustment of experimental parameters.

[0028] Please see the appendix Figure 1 and attached Figure 2 The main body of the mixing chamber consists of a mixing chamber top plate 7, a mixing chamber outer shell 9, and a mixing chamber bottom plate 10. It is made of acrylic material and is assembled by adhesive bonding. It is used to directly observe the degree of atomization from the outside.

[0029] Specifically, during device operation, when the tracer particles ejected from the atomizer body 8 mix and atomize with the gas delivered by the first mass flow controller 3 within the chamber, the high transparency of the acrylic material allows for direct and clear observation from the outside of the atomization state, distribution uniformity, and mixing process of the particles. Simultaneously, the adhesive assembly method ensures the sealing of the mixing chamber, preventing gas leakage from affecting flow stability. This design not only enables real-time visual monitoring of the atomization effect but also ensures the structural stability of the mixing chamber and the sealing of the gas path. This allows researchers to easily adjust the liquid inlet volume of the syringe pump 16 or the gas flow rate of the first mass flow controller 3 based on observation results, ensuring that the tracer particle atomization effect meets PIV measurement requirements and avoiding measurement errors caused by uneven atomization or leakage.

[0030] Please see the appendix Figure 1 and attached Figure 2 The air inlet 19, atomizer hole 20, and air outlet 21 on the top plate 7 of the mixing chamber are used to house the first pneumatic quick connector 5, the atomizer body 8, and the second pneumatic quick connector 6, respectively; the air inlet 19 and the air outlet 21 have internal threads.

[0031] Specifically, the mixing chamber top plate 7 has three functional holes: an air inlet 19, an atomizer hole 20, and an air outlet 21, which are respectively used to install the first pneumatic quick connector 5, the atomizer body 8, and the second pneumatic quick connector 6. The inner walls of the air inlet 19 and the air outlet 21 are threaded, allowing the first pneumatic quick connector 5 and the second pneumatic quick connector 6 to be securely and sealed in their respective holes. This avoids gas leakage caused by loose gas connections and ensures easy assembly and disassembly. In the working process, the gas supplied by the second mass flow controller 4 enters the first pneumatic quick connector 5 through the gas pipeline 2, and then smoothly enters the mixing chamber through the air inlet 19. After the atomizer body 8 is fixed through the atomizer hole 20, the tracer particles it emits are directly injected into the mixing chamber and come into contact with the gas. The mixed gas containing particles then flows through the air outlet 21 and the second pneumatic quick connector 6 to the burner. This precise fit design between the orifice and the components clearly defines the gas path, particle channel, and output channel, while ensuring the stability of each component installation and the airtightness of the gas path. This ensures smooth flow of gas and tracer particles, stable mixing process, and avoids the impact of channel misalignment or leakage on flow control accuracy and atomization mixing effect, thus providing a stable particle field for PIV measurement.

[0032] Please see the appendix Figure 1 and attached Figure 2 The bottom plate 10 of the mixing chamber has a drain hole 11 for housing the third pneumatic quick connector 12, and the drain hole 11 has threads inside.

[0033] Specifically, a drain hole 11 is precisely opened at the center of the mixing chamber bottom plate 10. The inner wall of the drain hole 11 is threaded, which is specifically used to install the third pneumatic quick connector 12. The third pneumatic quick connector 12 can be firmly and sealed at the drain hole 11 through the threaded engagement, which not only ensures the airtightness of the connection, but also facilitates disassembly and maintenance before and after the experiment. During the working process of the device, some of the tracer particle droplets sprayed by the atomizer body 8 will remain due to impact with the mixing chamber shell 9 or the inner wall of the mixing chamber bottom plate 10. These residual droplets will naturally collect on the mixing chamber bottom plate 10 along the chamber wall, and then flow into the air passage pipe 2 connected to the third pneumatic quick connector 12 through the drain hole 11. The experimenter can open the manual valve 13 in time according to the accumulation of waste liquid to guide the waste liquid into the collection cup 14 for centralized collection. This design, through the cooperation of the drain hole 11 and the third pneumatic quick connector 12, plays a role in directional guidance and efficient recovery of atomization residual waste liquid. This avoids the accumulation of waste liquid in the mixing chamber, which would contaminate the chamber and affect the subsequent atomization mixing effect. At the same time, it prevents waste liquid leakage from contaminating the experimental environment, ensures the continuous and stable conduct of the experiment, and indirectly improves the reliability of PIV measurement.

[0034] Please see the appendix Figure 1 and attached Figure 2 The second pneumatic quick connector 6 connects to the burner equipment for outputting variable flow gas with tracer particles.

[0035] Specifically, after the tracer particles and gas are fully mixed in the mixing chamber, the second pneumatic quick connector 6 is directly connected to the burner equipment. By stably outputting the airflow through the outlet 21, it plays the role of conveying variable flow gas with tracer particles, thereby adapting to the requirements of small flow combustion flow field and ensuring the stability of the PIV measurement particle field.

[0036] Please see the appendix Figure 1 and attached Figure 2 The injection pump 16 is connected to the liquid inlet of the atomizer body 8 via a hose 15; the first mass flow controller 3 is connected to the air inlet of the atomizer body 8 via a gas pipeline 2.

[0037] Specifically, the injection pump 16 stably delivers tracer particle liquid to the liquid inlet of the atomizer body 8 through the hose 15, and the first mass flow controller 3 provides atomization power to the air inlet of the atomizer body 8 through the gas pipeline 2. The two work together to supply raw materials and power to the atomizer body 8, thereby enabling the atomizer body 8 to stably generate tiny tracer particles and achieve the effect of PIV measurement of small flow combustion field.

[0038] Please see the appendix Figure 1 and attached Figure 2 Computer 1 controls the gas flow of the first mass flow controller 3 and the second mass flow controller 4 through supporting software.

[0039] Specifically, the computer 1 uses supporting software to precisely set and regulate the gas flow of the first mass flow controller 3 and the second mass flow controller 4, thereby distributing the amount of gas entering the mixing chamber and the atomizer body 8 as needed. This achieves the effect of adapting to the measurement requirements of small-flow combustion flow field, ensuring stable gas supply, and laying the foundation for uniform mixing of tracer particles.

[0040] Please see the appendix Figure 1 and attached Figure 2 The droplets sprayed from the atomizer body 8 remain in the mixing chamber due to impact with the container wall, etc., and are eventually discharged through the air passage pipe 2 connected to the third pneumatic quick connector 12 installed in the drain hole 11, and collected by the collection cup 14; a manual valve 13 is installed on the air passage pipe 2 connected to the third pneumatic quick connector 12 to control the discharge of waste liquid.

[0041] Specifically, some of the tracer particle droplets ejected by the atomizer body 8 during operation will remain inside the mixing chamber due to impact with the container walls such as the mixing chamber shell 9 and the mixing chamber bottom plate 10. These residual waste liquids will naturally collect along the chamber walls to the mixing chamber bottom plate 10; then, through the third pneumatic quick connector 12 installed on the drain hole 11, they will be discharged through the connected air passage pipe 2 and finally collected by the collection cup 14. The manual valve 13 installed on the air passage pipe 2 connected to the third pneumatic quick connector 12 can be opened or closed by the experimenter as needed, which can flexibly control the timing and rate of waste liquid discharge, thereby avoiding the accumulation of waste liquid in the mixing chamber and affecting the subsequent atomization mixing effect, preventing pollution of the experimental environment, and ensuring the continuous and stable measurement of the small-flow combustion flow field PIV.

[0042] Please see the appendix Figure 1 -Appendix Figure 5 The concentration monitoring and feedback control component consists of a laser incident window 22, a transmitted light receiving window 23, a micro laser 24, and a photoelectric receiver 25 installed on the outer shell 9 of the mixing chamber. It is used to monitor the concentration of tracer particles in the mixing chamber in real time and to control the propulsion speed of the injection pump 16.

[0043] Specifically, the concentration monitoring and feedback control component consists of a laser entrance window 22 and a transmitted light receiving window 23 specifically installed on the outer shell 9 of the mixing chamber, as well as a miniature laser 24 and a photodetector 25 installed on the outside of the mixing chamber. The laser entrance window 22 and the transmitted light receiving window 23 are made of high-transmittance quartz glass, which ensures smooth laser penetration while maintaining the airtightness of the mixing chamber. In the working process of the device, after the tracer particles and gas begin to mix and atomize in the mixing chamber, the miniature laser 24 continuously emits a laser beam with a stable wavelength. The laser beam passes through the laser entrance window 22 into the mixing chamber, penetrates the airflow containing tracer particles, and is accurately captured by the photodetector 25 through the transmitted light receiving window 23. The photodetector 25 converts the received light signal into an electrical signal in real time and transmits it to the computer 1 through the data acquisition card. The computer 1 uses the concentration calculation algorithm built into the supporting software to convert the light intensity attenuation into the real-time concentration value of the tracer particles in the mixing chamber. If the monitored concentration deviates from the target value set in the experiment, computer 1 will immediately issue a control command to adjust the propulsion speed of syringe pump 16. When the concentration is too high, the propulsion speed will be slowed down to reduce the liquid supply; when the concentration is too low, the propulsion speed will be accelerated to increase the liquid output. Through the coordinated operation of various components, this component can track particle concentration in real time and dynamically correct the liquid supply for tracer particles. This avoids the problems of overlapping PIV measurement images due to excessively high particle concentration and missing measurement points due to excessively low concentration, ensuring that the particle concentration remains stable within the optimal range during PIV measurement of a low-flow combustion flow field. This significantly improves the accuracy of flow field velocity data and the repeatability of the experiment.

[0044] Please see the appendix Figure 1 -Appendix Figure 5 The electrostatic enhancement component consists of a Venturi-porous plate composite mixer 26, an upper electrode ring 27, and a lower electrode ring 28 located inside the mixing chamber, which is used to improve particle dispersion and distribution uniformity.

[0045] Specifically, the electrostatic enhancement component consists of a composite mixer 26 specifically installed below the air inlet 19 inside the mixing chamber, and an upper electrode ring 27 and a lower electrode ring 28 symmetrically embedded in the inner wall of the mixing chamber. The composite mixer 26 adopts an integrated structure, with a Venturi tube section at the top and a porous diffuser section at the bottom. The composite mixer 26 is directly and sealed to the top plate 7 of the mixing chamber by engaging with the internal thread of the air inlet 19 through its top thread structure. During installation, PTFE tape can be wrapped around the threads to ensure airtightness. The upper electrode ring 27 and the lower electrode ring 28 are used in conjunction with an external programmable high-voltage DC power supply. In the device's workflow, when the gas delivered by the second mass flow controller 4 enters the mixing chamber, it first flows through the compound mixer 26. The Venturi tube section accelerates the airflow and forms a specific flow field through the structure of the contraction cone, throat, and expansion cone, promoting the initial mixing of the airflow with the tracer particles ejected from the atomizer body 8. Subsequently, the airflow is dispersed into multiple uniform microjets through the uniform micropores of the porous diffuser section, ensuring that the airflow is stably and uniformly distributed in the mixing chamber and fully mixed with the particles. At the same time, the upper electrode ring 27 and the lower electrode ring 28 can switch working modes according to experimental requirements. In the anti-agglomeration mode, a voltage of the same polarity is applied to make the particles repel each other with the same charge. In the uniform distribution mode, different voltages are applied to form a directional electric field to guide the diffusion of particles. This component optimizes the mixing efficiency of gas and tracer particles and improves the particle dispersion state through the synergistic effect of airflow homogenization and electrostatic interaction. This results in a more uniform and stronger tracking effect of tracer particles in the mixing chamber and subsequent combustion flow field, effectively avoiding the problem of particle tracking ambiguity during PIV measurement caused by particle agglomeration or uneven distribution. It provides a more reliable particle field guarantee for accurate velocity measurement of low-flow combustion flow fields.

[0046] Example 1 In this embodiment, methyl silicone oil is used as a tracer particle to measure the combustion flow field of a methane / air premixed flame via PIV measurement, which illustrates the specific implementation method and working process of this device in detail.

[0047] First, assemble and connect the device. Draw an appropriate amount of methyl silicone oil using a syringe, ensuring all air is expelled from the syringe before securely attaching it to the injection pump 16. The injection pump 16 is connected to the liquid inlet of the atomizer body 8 via a hose 15. Compressed air output from the gas cylinder 18 is regulated by the pressure reducing valve 17 and then connected to the inlets of the first mass flow controller 3 and the second mass flow controller 4 via gas pipelines 2. The outlet of the first mass flow controller 3 is connected to the air inlet of the atomizer body 8 via gas pipelines 2. The outlet of the second mass flow controller 4 is connected to the compound mixer 26 installed at the air inlet 19 via gas pipelines 2 and the first pneumatic quick connector 5. The air outlet 21 of the mixing chamber is connected to the air inlet of the Bunsen burner via the second pneumatic quick connector 6 and the corresponding gas pipeline. The concentration monitoring and feedback control component and the electrostatic enhancement component are installed and electrically connected as described above, ensuring that the optical paths of the miniature laser 24 and the photodetector 25 are aligned, and that the computer 1 can normally collect data and issue control commands.

[0048] Turn on the power to computer 1, first mass flow controller 3, second mass flow controller 4, syringe pump 16, and programmable high-voltage DC power supply. Open the main valve of gas cylinder 18 and adjust pressure reducing valve 17 to stabilize the output pressure within the required range.

[0049] In the software interface of computer 1, set the following initial parameters: 1. Set the flow rate of the first mass flow controller 3 to Q1 and the flow rate of the second mass flow controller 4 to Q2, ensuring that Q1 + Q2 equals the target total air flow rate. This total flow rate must be matched with the methane flow rate to meet the equivalence ratio requirements of premixed combustion.

[0050] 2. Set the target concentration value of the tracer particles to C. target .

[0051] 3. Select the operating mode of the electrostatic enhancement component. For example, set it to "anti-agglomeration mode" and apply a DC voltage of the same polarity and appropriate magnitude to the upper electrode ring 27 and the lower electrode ring 28. For example, the voltage range can be selected between -1kV and -10kV according to experimental requirements, so that the tracer particles can obtain sufficient surface charge to generate a mutually repelling electrostatic effect.

[0052] 4. Set the initial propulsion speed of the syringe pump 16 to V. initial .

[0053] After the parameters are set, start the first mass flow controller 3, the second mass flow controller 4, and the syringe pump 16 in sequence in the software interface. At the same time, turn on the miniature laser 24.

[0054] After the device is started, the compressed air is precisely divided into two paths: one path, Q1, enters the atomizer body 8 as atomizing gas; the other path, Q2, enters the compound mixer 26, where a stable flow field is formed through its venturi section. Subsequently, the airflow is evenly distributed into multiple micro-airflows by the porous diffuser section. The injection pump 16 delivers methyl silicone oil to the atomizer body 8 at a set speed, where it is broken into micron-sized droplets by the atomizing gas and sprayed into the mixing chamber.

[0055] Within the mixing chamber, the uniform airflow from the compound mixer 26 is thoroughly mixed with the tracer particle droplets generated by the atomizer. During this process: Concentration Monitoring and Feedback: The laser beam emitted by the miniature laser 24 passes through the aerosol in the mixing chamber and is received by the photodetector 25. The computer 1 calculates the light intensity attenuation in real time and converts it into a particle concentration value C. real The PID control algorithm within the software will control C. real With C target Compare, if C real <C target If C, the injection speed of the syringe pump 16 will automatically increase; real >C target Then it will automatically reduce its propulsion speed until C real Stable at C target Nearby, closed-loop stable control of concentration is achieved.

[0056] Electrostatic enhancement: The flow equalization effect of the composite mixer 26 works in conjunction with the electrostatic field. In the 'anti-agglomeration mode', charged tracer particles avoid agglomeration due to mutual electrostatic repulsion, maintaining a good dispersion state and effectively improving the uniformity of particle distribution in the flow field.

[0057] Through the acrylic mixing chamber shell 9, the atomization and mixing situation inside the chamber can be directly monitored, serving as an auxiliary basis for judgment.

[0058] The optimized aerosol, with stable concentration and uniform distribution after the above process, is output through the second pneumatic quick connector 6 and mixed with methane gas before the Bunsen burner to form a combustible premixed gas. PIV measurement is then performed after ignition.

[0059] Observe the tracer particle image in the PIV acquisition software. If the particle density in the image is still not ideal, the target concentration value C in computer 1 can be fine-tuned. target The concentration monitoring and feedback control system will automatically adjust to the new set value. If poor particle tracking is detected, try switching the electrostatic enhancement component to "uniform distribution mode" or adjusting the electric field strength.

[0060] If waste liquid is observed to accumulate at the bottom of the mixing chamber during the experiment, the manual valve 13 can be opened in time to discharge the waste liquid into the collection cup 14 to avoid interfering with the experiment.

[0061] After the experiment, shut off the syringe pump 16, mass flow controller, valve of gas cylinder 18, high-voltage power supply and power supply of each device in sequence.

[0062] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A controllable flow tracer particle generator for PIV measurement, characterized in that: The system includes a mixing chamber assembly, a tracer particle generating assembly, a flow control assembly, a concentration monitoring and feedback control assembly, and an electrostatic enhancement assembly. The mixing chamber assembly consists of a first pneumatic quick connector (5), a second pneumatic quick connector (6), a mixing chamber top plate (7), a mixing chamber outer shell (9), a mixing chamber bottom plate (10), a drain hole (11), a third pneumatic quick connector (12), a manual valve (13), a collection cup (14), an air inlet (19), an atomizer hole (20), and an air outlet (21). The tracer particle generating assembly consists of an atomizer body (8), a hose (15), and an injection pump (16). The flow control assembly consists of a computer (1), a gas pipeline (2), a first mass flow controller (3), a second mass flow controller (4), a pressure reducing valve (17), and a gas cylinder (18).

2. The controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The main body of the mixing chamber consists of the mixing chamber top plate (7), the mixing chamber shell (9), and the mixing chamber bottom plate (10). It is made of acrylic material and is assembled by adhesive bonding. It is used to directly observe the degree of atomization from the outside.

3. The controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The air inlet (19), atomizer hole (20) and air outlet (21) on the top plate (7) of the mixing chamber are used to house the first pneumatic quick connector (5), the atomizer body (8) and the second pneumatic quick connector (6), respectively; the air inlet (19) and air outlet (21) are threaded.

4. A controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The bottom plate (10) of the mixing chamber has a drain hole (11) for accommodating a third pneumatic quick connector (12), and the drain hole (11) has threads.

5. A controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The second pneumatic quick connector (6) connects to the burner equipment for outputting variable flow gas with tracer particles.

6. A controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The injection pump (16) is connected to the liquid inlet of the atomizer body (8) via a hose (15); the first mass flow controller (3) is connected to the air inlet of the atomizer body (8) via a gas pipeline (2).

7. A controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The computer (1) controls the gas flow of the first mass flow controller (3) and the second mass flow controller (4) through the supporting software.

8. A controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The droplets sprayed from the atomizer body (8) remain in the mixing chamber due to impact with the container wall and other reasons. They are eventually discharged through the air pipe (2) connected to the third pneumatic quick connector (12) installed in the drain hole (11) and collected by the collection cup (14). A manual valve (13) is installed on the air pipe (2) connected to the third pneumatic quick connector (12) to control the discharge of waste liquid.

9. A controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The concentration monitoring and feedback control component consists of a laser incident window (22), a transmitted light receiving window (23), a micro laser (24), and a photoelectric receiver (25) set on the outer shell (9) of the mixing chamber. It is used to monitor the concentration of tracer particles in the mixing chamber in real time and to control the propulsion speed of the injection pump (16) in feedback.

10. A controllable flow tracer particle generator for PIV measurement according to claim 1, characterized in that: The electrostatic enhancement component consists of a Venturi-porous plate composite mixer (26), an upper electrode ring (27), and a lower electrode ring (28) disposed inside the mixing chamber, and is used to improve particle dispersion and distribution uniformity.

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