Tracer particle generation system for microscale flow channel flow process measurement

Abstract

The application discloses a tracer particle generating system for micro-scale flow channel flow process measurement and belongs to the technical field of micro-scale flow channel flow process measurement. In the system, a combustion flow path is used for obtaining a gas flow carrying nano-scale tracer particles by burning biomass materials; a dilution flow path is connected with an outlet end of the combustion flow path and is used for diluting the nano-scale tracer particle gas flow from the combustion flow path to obtain a nano-scale tracer particle gas flow with a required concentration. The application can obtain the nano-scale tracer particle gas flow with the required concentration and has the advantages of easy preparation, low cost and low pollution.

Description

Technical Field

[0001] This invention relates to the field of microscale flow process measurement technology, and in particular to a tracer particle generation system for microscale flow process measurement. Background Technology

[0002] Porous media have been widely used in sweating cooling, seepage combustion materials, and the internal structures of composite materials. Their flow and heat / mass transfer characteristics directly affect the efficiency, safety, and reliability of the system. Therefore, the study of flow fields related to porous media has significant theoretical and engineering value. However, due to the influence of the pore structure of porous media, fluid flow within and on the surface of porous media exhibits typical characteristics such as complex structure, large scale span, strong interface effects, and numerous coupling problems. These characteristics pose greater challenges to experimental measurement techniques.

[0003] Currently, commonly used non-contact flow velocity measurement methods include laser Doppler velocimetry (LDV), particle image velocimetry (PIV), molecular marker velocimetry (MTV), and femtosecond laser electron excitation (FEE) labeling velocimetry. Among these, molecular marker velocimetry and FEE both rely on laser excitation of the material within the flow field, resulting in low spatial resolution and limitations imposed by fluorescence quenching time, making it difficult to achieve high-precision measurements of flow states in porous media and near their outlets. Both LDV and PEV techniques require the placement of tracer particles in the flow field for flow process measurement. Currently, commonly used tracer particles in gas flow field measurements are atomized tar droplets and titanium dioxide particles. However, tar droplets are relatively large and exhibit severe adhesion effects in narrow flow channels, making them unsuitable for porous media measurements. Titanium dioxide particles typically range in size from 1 μm to 40 μm, while the pore size in porous media is mainly distributed in the range of 101 μm to 102 μm. Generally, in flow field measurements within straight pipes, the ratio of the tracer particle size to the characteristic size of the flow channel should be less than 1 / 10 to ensure that the particles do not clog the channel or severely affect the flow field morphology. However, the pores in porous media are highly irregular, and the particle size requirements for tracer particles are much higher than for common regular flow channels. If commonly used micron-sized titanium dioxide particles are used, they may clog the channel in porous media measurements, affecting the measurement results. To accurately measure the flow velocity in microscale flow channels such as porous media, submicron or even nanometer-sized tracer particles are required.

[0004] Meanwhile, the smaller the tracer particle size, the higher the production cost. Currently, 500g of titanium dioxide particles with a diameter of 1μm can cost thousands of yuan, which makes the preparation of submicron-sized titanium dioxide particles theoretically feasible, but lacks practical application in engineering.

[0005] In summary, in engineering practice, the limitations of tracer particles restrict the study of flow processes within microscale channels: droplets, such as those from e-liquid, are too large, resulting in significant adhesion effects; while nano-sized titanium dioxide particles are difficult to prepare, costly, and difficult to process, causing pollution when released into the atmosphere. To address this issue, there is an urgent need to develop tracer particles that are small in size, easy to prepare, and low in pollution. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to propose a tracer particle generation system for measuring microscale flow processes, capable of obtaining an airflow of nanoscale tracer particles at the desired concentration, with advantages of easy preparation, low cost, and low pollution.

[0007] A tracer particle generation system for measuring microscale flow processes according to an embodiment of the present invention includes: Combustion flow path, wherein the combustion flow path is used to obtain an airflow carrying nanoscale tracer particles by burning biomass materials; A dilution flow path is connected to the outlet end of the combustion flow path and is used to dilute the gas flow carrying nanoscale tracer particles from the combustion flow path to obtain a gas flow of nanoscale tracer particles of the desired concentration.

[0008] The workflow of the tracer particle generation system for measuring microscale flow processes in this embodiment is as follows: The combustion flow path is activated to obtain an airflow carrying nanoscale tracer particles through incomplete combustion of biomass materials; the airflow carrying nanoscale tracer particles obtained from the combustion flow path enters the dilution flow path, and simultaneously, a carrier gas flow is input into the dilution flow path to fully and uniformly mix and dilute the airflow carrying nanoscale tracer particles from the combustion flow path, obtaining an airflow with the required concentration of nanoscale tracer particles, which is then transported to the subsequent process through the subsequent delivery flow path to carry out microscale flow process measurements.

[0009] The tracer particle generation system for measuring microscale flow processes in this invention has the following advantages: First, the tracer particles are easy to prepare and inexpensive. Specifically, the tracer particle generation system for measuring microscale flow processes uses biomass materials as raw materials to generate nanoscale tracer particles. Biomass is widely available and inexpensive, and the preparation process does not require complex chemical synthesis or nanofabrication, significantly reducing the production and use costs of tracer particles. Second, it is low-pollution. Specifically, the generated tracer particles come from biomass combustion, and their components (such as carbon-based particles and natural organic derivatives) are more easily degraded. The pollution to the environment after emission is far less than that of TiO2, meeting environmental protection requirements. Third, the tracer particles have a small average particle size. Specifically, the smoke particles produced in the combustion flow path serve as nanoscale tracer particles. Compared with traditional titanium dioxide particles, their average particle size is much smaller, which can be applied to microscale channel measurements at the micrometer level. This avoids channel blockage, has good tracking performance, and is helpful for velocity measurements in high-speed flow fields. Fourth, the size, concentration, and uniformity of the tracer particles are controllable. The dilution flow path introduces a carrier gas flow (such as nitrogen or dry air) to dilute the high-concentration original gas flow generated by combustion to the required concentration, ensuring uniform particle distribution and stable, uniform particle concentration in the output gas flow, thus meeting the requirements of subsequent measurements. Fifth, it has a wide range of applications: by adjusting the airflow conditions in the combustion flow path and the compaction of the biomass material, the size of nanoscale tracer particles can be controlled, thereby adapting to different experimental conditions.

[0010] In some embodiments, the combustion flow path includes a combustion chamber, a filter layer disposed within the combustion chamber, a filling combustion zone, and an electric heating component; the outlet end of the combustion chamber is connected to the dilution flow path, and the inlet end of the combustion chamber is for the gas to participate in combustion to enter; the filter layer is located downstream of the filling combustion zone in the flow direction of the combustion flow path, the filling combustion zone is used to fill biomass material, and the electric heating component is used to ignite the biomass material.

[0011] In some embodiments, the biomass material filling the combustion zone is located adjacent to the filter layer and the electric heating element.

[0012] In some embodiments, the electric heating component is an electric heating filter; or, the electric heating component includes an electric heating rod and a porous plate, the electric heating rod extending into the filling combustion zone, and the porous plate being located upstream of the filling combustion zone.

[0013] In some embodiments, the combustion chamber includes an outer combustion tube and an inner combustion tube, the outlet end of the outer combustion tube is the outlet end of the combustion chamber, the outlet end of the inner combustion tube is detachably fixed inside the inlet end of the outer combustion tube, and the inlet end of the inner combustion tube is the inlet end of the combustion chamber. The filter layer and the filling combustion zone are located inside the outer combustion tube, and the electric heating filter is fixed at the outlet end face of the inner combustion tube; or, the filter layer and the filling combustion zone are located inside the outer combustion tube and the electric heating rod is located in the filling combustion zone, and the porous plate is fixed at the outlet end face of the inner combustion tube.

[0014] In some embodiments, the biomass material is dried and pulverized plant biomass material.

[0015] In some embodiments, the combustion flow path further includes a dryer located upstream of the combustion flow path in the flow direction.

[0016] In some embodiments, the dilution flow path includes a main flow path and a regulating flow path; the outlet end of the main flow path is connected to the inlet end of the output interface; the main flow path includes a buffer mixing chamber and a monitoring section arranged sequentially in the flow direction of the main flow path; the outlet end of the combustion flow path is located upstream of the buffer mixing chamber in the flow direction of the main flow path; the buffer mixing chamber is used to uniformly dilute the nanoscale tracer particles to obtain an initial dilution airflow; the monitoring section is used to monitor the concentration of nanoscale tracer particles in the initial dilution airflow from the buffer mixing chamber. The outlet end of the regulating flow path is connected to the main flow path and is located between the monitoring section and the outlet end of the main flow path. The regulating flow path adjusts the gas flow rate at the outlet end of the regulating flow path according to the regulating signal output by the monitoring section, so that the gas from the outlet end of the regulating flow path is further diluted by the first dilution gas flowing downstream of the monitoring section, thereby obtaining the required concentration of nanoscale tracer particle gas flow.

[0017] In some embodiments, the buffer mixing chamber is one or more can-shaped containers containing a rectifier structure for uniformly diluting nanoscale tracer particles.

[0018] In some embodiments, the monitoring section includes a particle concentration monitor and a controller, and the regulating flow path includes a regulating valve; the particle concentration monitor is used to monitor the concentration of nanoscale tracer particles in the initial dilution gas flow from the buffer mixing chamber, and the controller outputs an adjustment signal based on the current particle concentration to control the opening of the regulating valve.

[0019] In some embodiments, the particle concentration monitor is a laser scattering or laser absorption particle concentration monitor.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the tracer particle generation system for measuring microscale flow processes in a channel according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a combustion chamber structure that uses an electric heating rod and a perforated plate as electric heating components; Figure 3 This is a schematic diagram of a combustion chamber structure that uses an electrically heated filter screen as the electric heating component.

[0022] Figure Labels A tracer particle generation system 1000 for measuring microscale flow processes in flow channels; Combustion flow path 1; combustion chamber 101; filter layer 1011; filled combustion zone 1012; electric heating component 1013; electric heating rod 10131; perforated plate 10132; electric heating filter screen 10133; outer combustion tube 1014; inner combustion tube 1015; groove 1016; dryer 102; Dilution path 2; Mainstream path 201; Buffer mixing chamber 2011; Monitoring section 2012; Controller 2013; Regulating flow path 202; regulating valve 2021. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] The following is combined Figures 1 to 3 This invention describes a tracer particle generation system 1000 for measuring microscale flow processes in a channel, according to an embodiment of the present invention.

[0025] like Figures 1 to 3 As shown, the tracer particle generation system 1000 for measuring microscale flow processes in the present invention includes a combustion flow path 1 and a dilution flow path 2.

[0026] Combustion path 1 is used to obtain an airflow carrying nanoscale tracer particles by burning biomass materials. The main function of combustion path 1 is to perform incomplete combustion of biomass materials while providing airflow to power the tracer particles generated by incomplete combustion. Since nanoscale tracer particles are produced by incomplete combustion of biomass materials, the production cost is low, and the nanoscale tracer particles can be completely burned after use to reduce pollution.

[0027] The particle size of the tracer particles generated during combustion is determined by the temperature of the combustion zone, airflow rate, and the particle size and dryness of the biomass material. The particle size distribution follows a normal distribution, and by adjusting the operating conditions, the half-maximum (FWHM) range of the particle size distribution can be constrained to within ±20 nm. Excessively large particles can be filtered out by the filter layer, while excessively small particles have virtually no impact on the measurement and can be ignored.

[0028] Dilution path 2 is connected to the outlet of combustion path 1 and is used to dilute the gas flow carrying nanoscale tracer particles from combustion path 1 to obtain the desired concentration of nanoscale tracer particle gas flow. The concentration of nanoscale tracer particles directly generated by incomplete combustion in combustion path 1 is often too high. Therefore, it is necessary to thoroughly and uniformly mix and dilute the carrier gas flow input through dilution path 2 with the gas flow carrying nanoscale tracer particles from combustion path 1 to adjust the concentration of nanoscale tracer particles in the gas flow to a suitable range for measurement.

[0029] The workflow of the tracer particle generation system 1000 for measuring microscale flow processes in this embodiment is as follows: Combustion flow path 1 is started to obtain an airflow carrying nanoscale tracer particles through incomplete combustion of biomass materials; the airflow carrying nanoscale tracer particles obtained from combustion flow path 1 enters dilution flow path 2, and simultaneously, carrier gas flow is input into dilution flow path 2 to fully and uniformly mix and dilute the airflow carrying nanoscale tracer particles from combustion flow path 1 to obtain the required concentration of nanoscale tracer particle airflow; subsequently, the required concentration airflow at the outlet of dilution flow path 2 flows into the output interface and is transported to subsequent processes to carry out microscale flow process measurements.

[0030] The tracer particle generation system 1000 for measuring microscale flow processes in this invention has the following advantages: First, the tracer particles are easy to prepare and inexpensive. Specifically, the tracer particle generation system 1000 for measuring microscale flow processes in microscale uses biomass materials as raw materials to generate nanoscale tracer particles. Biomass is widely available and inexpensive, and the preparation process does not require complex chemical synthesis or nanofabrication, significantly reducing the production and use costs of tracer particles. Second, it has low pollution. Specifically, the generated tracer particles come from biomass combustion, and their components (such as carbon-based particles and natural organic derivatives) are more easily degraded. The pollution to the environment after emission is far less than that of TiO2, meeting environmental protection requirements. Third, the tracer particles have a small average particle size. Specifically, the smoke particles in combustion flow path 1 serve as nanoscale tracer particles. Compared to traditional titanium dioxide particles, their average particle size is much smaller, allowing for applications in microscale channel measurements at the micrometer level. This avoids channel blockage, provides better tracking performance, and facilitates velocity measurements in high-speed flow fields. Fourth, the size, concentration, and uniformity of the tracer particles are controllable. Dilution flow path 2 introduces a carrier gas flow (such as nitrogen or dry air) to dilute the high-concentration original gas flow generated by combustion to the required concentration, ensuring uniform particle distribution. The output interface adjusts the dilution flow rate to ensure stable and uniform particle concentration in the output gas flow, adapting to the requirements of subsequent measurements. Fifth, it has a wide range of applications: by adjusting the airflow conditions in combustion flow path 1 and the compaction of the biomass material, the size of the nanoscale tracer particles can be controlled, thus adapting to different experimental conditions.

[0031] In some embodiments, the combustion flow path 1 includes a combustion chamber 101, a filter layer 1011 disposed within the combustion chamber 101, a combustion-filled zone 1012, and an electric heating element 1013. The outlet end of the combustion chamber 101 is connected to the dilution flow path 2, and the inlet end of the combustion chamber 101 is for the gas participating in the combustion to enter. The filter layer 1011 is located downstream of the combustion-filled zone 1012 in the flow direction of the combustion flow path 1. The combustion-filled zone 1012 is used to fill biomass material. The electric heating element 1013 is used to ignite the biomass material. The inlet end of the combustion chamber 101 is connected to the gas participating in the combustion, and the outlet end is directly connected to the inlet of the dilution flow path 2 through a channel. The filter layer 1011 can be a soft filter material to filter the gas flow after combustion, remove unburned large particulate impurities, ensure the size and uniformity of nanoscale tracer particles in the subsequent gas flow entering the dilution flow path 2, and avoid impurities interfering with the measurement. The combustion-filled zone 1012 is used to fill biomass material as fuel for the combustion reaction. During biomass combustion, its organic components decompose / gasify to generate nanoscale tracer particles with a particle size much smaller than the pore size of the porous medium, which are output along with the combustion gas flow. The electric heating element 1013 ignites the biomass material filling the combustion zone 1012 by electric heating. The electric heating element 1013 is not only a one-time ignition source, but also a permanent heat source for controlling the temperature inside the combustion chamber 101.

[0032] The workflow and principle of the tracer particle generation system 1000 for measuring microscale flow processes in this embodiment are as follows: The combustion gas (such as air or other suitable oxidant) enters from the inlet end of the combustion chamber 101, flows through the biomass material filling the combustion zone 1012, and the electric heating component 1013 ignites the biomass material. The biomass material reacts with the combustion gas, and the incomplete combustion of the biomass material generates nanoscale tracer particles which enter the filter layer 1011 with the combustion airflow. After the filter layer 1011 filters and removes impurities, an airflow carrying nanoscale tracer particles is obtained, which is output from the outlet end of the combustion chamber 101 and directly enters the dilution flow path 2 for concentration control.

[0033] Taking the experiment of filling dry tobacco shreds as fuel as an example: the particle size distribution of its smoke aerosol is concentrated in the range of 100~300nm, and the number concentration per unit volume is between 1.35×10⁻⁶. 8 -2.86×10 8 pcs / cm 3 Further filtration of cigarette smoke can reduce aerosol particle size and number concentration per unit volume. Therefore, the combustion chamber 101 of this embodiment can stably provide the required 10 2 nm-level tracer particles.

[0034] In some embodiments, such as Figure 2 and Figure 3As shown, the biomass material filled in the combustion zone 1012 is located adjacent to the filter layer 1011 and the electric heating element 1013. The three are arranged closely along the gas flow direction, from the electric heating element 1013 through the combustion zone 1012 to the filter layer 1011. This close arrangement reduces airflow stagnation within the combustion chamber 101, prevents the agglomeration of nanoscale tracer particles, and ensures that the generated nanoscale tracer particles quickly enter the filter layer 1011 and the dilution flow path 2.

[0035] In some embodiments, such as Figure 3 As shown, the electric heating component 1013 is an electric heating filter 10133. The electric heating filter is used to heat the combustion, regulate the airflow, and compress the biomass material filling the combustion zone 1012. It has a simple structure and high heat transfer efficiency.

[0036] In some embodiments, such as Figure 2 As shown, the electric heating component 1013 includes an electric heating rod 10131 and a perforated plate 10132. The electric heating rod 10131 extends into the filling combustion zone 1012, and the perforated plate 10132 is located upstream of the filling combustion zone 1012. The electric heating rod 10131 is used for heating combustion, and the perforated plate 10132 functions to compress the fuel, regulate airflow, and fix the electric heating rod 10131. The structure is simple and easy to install. The electric heating rod 10131 extending into the filling combustion zone 1012 of the combustion chamber 101 makes the biomass material burn more evenly.

[0037] In some embodiments, such as Figure 2 and Figure 3 As shown, the combustion chamber 101 includes an outer combustion tube 1014 and an inner combustion tube 1015. The outlet end of the outer combustion tube 1014 is the outlet end of the combustion chamber 101. The outlet end of the inner combustion tube 1015 is detachably fixed inside the inlet end of the outer combustion tube 1014, i.e., the inner combustion tube 1015 is inserted into the inlet of the outer combustion tube 1014 and connected by means of snaps, threads, etc. The inlet end of the inner combustion tube 1015 is the inlet end of the combustion chamber 101. The filter layer 1011 and the combustion-filling zone 1012 are located inside the outer combustion tube 1014, and the electrically heated filter screen is fixed at the outlet end face of the inner combustion tube 1015; or, the filter layer 1011 and the combustion-filling zone 1012 are located inside the outer combustion tube 1014, and the electrically heated rod 10131 is located in the combustion-filling zone 1012, and the perforated plate 10132 is fixed at the outlet end face of the inner combustion tube 1015. This makes disassembly and assembly convenient.

[0038] In some embodiments, such as Figure 3As shown, the inner wall surface of the outer combustion tube 1014 is provided with a groove 1016 for fixing the filter layer 1011. The filter layer 1011 is fixed to the inner wall of the inner combustion tube 1015 through the annular groove 1016 on the tube wall. In this way, the filter layer 1011 can be disassembled and replaced after a certain working cycle to avoid the filter layer 1011 from clogging and affecting the operation of the combustion chamber 101.

[0039] In some embodiments, the biomass material is dried and pulverized plant biomass material. This includes dried leaves, straw, sawdust, rice husks, bark, moss, hay, and processed plant residues (such as sugarcane bagasse). Different materials require different temperatures and airflow rates. After being pulverized, the biomass material is filled into the combustion chamber 101, which facilitates shaping and increases the porosity of the biomass material, allowing the airflow to carry carbon soot particles through.

[0040] In some embodiments, the combustion flow path 1 further includes a dryer 102, which is located upstream of the combustion flow path 1 in the flow direction. The biomass material is dried by the dryer 102 to remove moisture and is then pulverized to a suitable particle size. By incorporating the dryer 102, the following advantages are achieved: first, it increases the standardization of the material, ensuring uniform material properties within the combustion chamber 101, and facilitating comparison with data from various major thermophysical property databases for calculating operating parameters; second, it increases the porosity of the material, reducing its adsorption capacity and preventing the biomass material itself from adsorbing soot particles; and third, it increases the flammability of the biomass material, facilitating ignition and temperature control.

[0041] In some embodiments, the dilution flow path 2 includes a main flow path 201 and a regulating flow path 202. The outlet end of the main flow path 201 is connected to the inlet end of the output interface. The main flow path 201 includes a buffer mixing chamber 2011 and a monitoring section 2012 arranged sequentially in the flow direction of the main flow path 201. The outlet end of the combustion flow path 1 is located upstream of the buffer mixing chamber 2011 in the flow direction of the main flow path 201. The buffer mixing chamber 2011 is used to dilute the nanoscale tracer particles uniformly to obtain the initial diluted airflow. The monitoring section 2012 is used to monitor the concentration of nanoscale tracer particles in the initial diluted airflow from the buffer mixing chamber 2011 and output a regulating signal. The airflow carrying nanoscale tracer particles obtained by the combustion flow path 1 enters the main flow path 201, is initially mixed with the carrier gas flow introduced into the main flow path 201, and then enters the buffer mixing chamber for thorough and uniform mixing to obtain the initial diluted airflow. By setting up the buffer mixing chamber, the problem of uneven distribution and large concentration fluctuation of nanoscale tracer particles in the original airflow can be solved. A stirrer (not shown in the figure) can be installed inside the buffer mixing chamber 2011 to ensure thorough mixing of the gas and uniform dispersion of the nanoscale tracer particles, providing a stable foundation for monitoring and control in the subsequent monitoring section 2012. The cavity of the buffer mixing chamber 2011 can be a large-volume cavity, and its internal structure should avoid dead zones to prevent the deposition of nanoscale tracer particles.

[0042] The outlet end of the regulating flow path 202 is connected to the main flow path 201 and is located between the monitoring section 2012 and the outlet end of the main flow path 201. The regulating flow path 202 adjusts the gas flow at the outlet end of the regulating flow path 202 according to the regulating signal output by the monitoring section 2012, so that the gas from the outlet end of the regulating flow path 202 is further diluted by the first dilution gas downstream of the monitoring section 2012 to obtain the required concentration of nanoscale tracer particle gas flow.

[0043] In some embodiments, the monitoring section 2012 includes a particle concentration monitor (not shown) and a controller 2013, and the regulating flow path 202 includes a regulating valve 2021 (such as an electrically operated regulating valve); the particle concentration monitor is used to monitor the concentration of nanoscale tracer particles in the initial dilution gas flow from the buffer mixing chamber 2011, and the controller 2013 outputs a regulating signal according to the current particle concentration to control the opening of the regulating valve 2021.

[0044] The workflow of the tracer particle generation system 1000 for measuring microscale flow processes in this embodiment is as follows: First, the main flow path 201 is started to supply gas; at the same time, the combustion flow path 1 is introduced with gas flow that participates in combustion. The gas flow first passes through the dryer 102 to remove water before entering the combustion chamber 101. The gas flow generates and carries a large number of nanoscale tracer particles through the combustion reaction; then, the gas flow carrying nanoscale tracer particles merges into the main flow path 201 from the outlet end of the combustion flow path 1. Before entering the buffer mixing chamber 2011, the carrier gas flow in the main flow path 201 is initially mixed. The gas then enters the buffer mixing chamber 2011 to achieve thorough mixing and dilution of the nanoscale tracer particles, obtaining the initial dilution gas flow. This initial dilution gas flow then enters the monitoring section 2012, where a particle concentration monitor tracks the concentration of tracer particles. The monitor transmits the concentration signal to the controller 2013, which outputs an adjustment signal to the regulating valve 2021 on the regulating flow path 202 based on the current and target concentrations. The regulating valve 2021 responds to the signal by changing its opening to adjust the gas output flow of the regulating flow path 202. The gas flow output from the regulating flow path 202 then enters the main flow path 201, where it mixes and dilutes with the initial dilution gas flow to obtain the desired concentration of nanoscale tracer particle gas flow into the output interface, providing a stable concentration of tracer particle gas flow for the measurement process.

[0045] In some embodiments, the particle concentration monitor employs a laser scattering or laser absorption particle concentration monitor. Using laser scattering or laser absorption technology to measure soot particle concentration and size is relatively easy to implement when high accuracy requirements are not necessary. Furthermore, as a non-contact measurement method, its significant advantages include no interference with the flow field, no need for frequent filter paper replacements, and fast feedback speed. This is beneficial for the tracer particle generation system 1000, which is designed for measuring microscale flow processes, to dynamically adjust the particle size and concentration of tracer particles.

[0046] In some embodiments, the regulating valve 2021 is an electrically operated regulating valve. Electrically operated regulating valves are directly driven by electrical signals, offering advantages such as high control precision, fast response speed, and ease of integration with controllers.

[0047] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A tracer particle generation system for measuring microscale flow processes in channels, characterized in that, include: Combustion flow path, wherein the combustion flow path is used to obtain an airflow carrying nanoscale tracer particles by burning biomass materials; A dilution flow path is connected to the outlet end of the combustion flow path and is used to dilute the gas flow carrying nanoscale tracer particles from the combustion flow path to obtain a gas flow of nanoscale tracer particles of the desired concentration.

2. The tracer particle generation system for measuring microscale flow processes according to claim 1, characterized in that, The combustion flow path includes a combustion chamber, a filter layer disposed within the combustion chamber, a filling combustion zone, and an electric heating component; the outlet end of the combustion chamber is connected to the dilution flow path, and the inlet end of the combustion chamber is for the gas to participate in combustion to enter; the filter layer is located downstream of the filling combustion zone in the flow direction of the combustion flow path, the filling combustion zone is used to fill biomass material, and the electric heating component is used to ignite the biomass material.

3. The tracer particle generation system for measuring microscale flow processes according to claim 2, characterized in that, The biomass material filling the combustion zone is located adjacent to the filter layer and the electric heating element.

4. The tracer particle generation system for measuring microscale flow processes according to claim 3, characterized in that, The electric heating component is an electric heating filter; or, the electric heating component includes an electric heating rod and a porous plate, the electric heating rod extending into the filling combustion zone, and the porous plate located upstream of the filling combustion zone.

5. The tracer particle generation system for measuring microscale flow processes according to claim 4, characterized in that, The combustion chamber includes an outer combustion tube and an inner combustion tube. The outlet end of the outer combustion tube is the outlet end of the combustion chamber. The outlet end of the inner combustion tube is detachably fixed inside the inlet end of the outer combustion tube. The inlet end of the inner combustion tube is the inlet end of the combustion chamber. The filter layer and the filling combustion zone are located inside the outer combustion tube, and the electric heating filter is fixed at the outlet end face of the inner combustion tube; or, the filter layer and the filling combustion zone are located inside the outer combustion tube and the electric heating rod is located in the filling combustion zone, and the porous plate is fixed at the outlet end face of the inner combustion tube.

6. The tracer particle generation system for measuring microscale flow processes according to claim 1, characterized in that, The biomass material is dried and pulverized plant biomass material.

7. The tracer particle generation system for measuring microscale flow processes according to claim 1, characterized in that, The combustion flow path also includes a dryer, which is located upstream of the combustion flow path in the flow direction.

8. The tracer particle generation system for measuring microscale flow processes according to any one of claims 1-7, characterized in that, The dilution flow path includes a main flow path and a regulating flow path; the main flow path includes a buffer mixing chamber and a monitoring section arranged sequentially in the flow direction of the main flow path, and the outlet end of the combustion flow path is located upstream of the buffer mixing chamber in the flow direction of the main flow path. The buffer mixing chamber is used to dilute the nanoscale tracer particles uniformly to obtain the initial dilution airflow, and the monitoring section is used to monitor the concentration of nanoscale tracer particles in the initial dilution airflow from the buffer mixing chamber. The outlet end of the regulating flow path is connected to the main flow path and is located between the monitoring section and the outlet end of the main flow path. The regulating flow path adjusts the gas flow rate at the outlet end of the regulating flow path according to the regulating signal output by the monitoring section, so that the gas from the outlet end of the regulating flow path is further diluted by the first dilution gas flowing downstream of the monitoring section, thereby obtaining the required concentration of nanoscale tracer particle gas flow.

9. The tracer particle generation system for measuring microscale flow processes according to claim 8, characterized in that, The monitoring section includes a particle concentration monitor and a controller, and the regulating flow path includes a regulating valve; the particle concentration monitor is used to monitor the concentration of nanoscale tracer particles in the initial dilution gas flow from the buffer mixing chamber, and the controller outputs an adjustment signal according to the current particle concentration to control the opening of the regulating valve.

10. The tracer particle generation system for measuring microscale flow processes according to claim 9, characterized in that, The particle concentration monitor is a laser scattering or laser absorption particle concentration monitor.

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