Laminar thermal boundary layer-based temperature-sensitive particle calibration method and system

Abstract

The present application belongs to the field of fluid dynamics and optical measurement technology, and particularly relates to a temperature-sensitive particle calibration method and system based on laminar thermal boundary layer, which comprises the following steps: a stable flow state of laminar thermal boundary layer is constructed by using a flow generating device, and temperature-sensitive particles to be calibrated are scattered in the fluid; fluid mechanics equation groups are solved in the whole flow field according to boundary conditions, and the analytical results of the fluid mechanics equation groups are corrected according to the fluid dynamics simulation results; laser is shaped into a sheet-shaped excitation light to excite the temperature-sensitive particles, and the position and light-emitting characteristics of the temperature-sensitive particles are obtained through data processing; the flow boundary conditions of the environment temperature where the temperature-sensitive particles are located are adjusted to realize the calibration of the temperature-sensitive particles; and the present application realizes the full-process automatic processing from the original image to the calibration curve by adopting the technical means of automatically extracting the light-emitting characteristics of the particles through image processing and data fitting algorithm, and improves the objectivity and processing efficiency of the calibration data.

Description

Technical Field

[0001] This invention belongs to the field of fluid dynamics and optical measurement technology, specifically a temperature-sensitive particle calibration method and system based on laminar thermal boundary layer. Background Technology

[0002] In recent years, with the development of science and technology and the improvement of industrial production levels, various complex fluid machinery, such as new gas turbines and high-efficiency heat exchangers, are gradually being applied to all aspects of social production activities and people's daily lives. Correspondingly, to achieve in-depth analysis of heat and mass transfer phenomena within fluids, temperature measurement technologies applicable to the internal workings of fluids have flourished. Among these, using temperature-sensitive particles to measure the temperature distribution within fluids is a widely adopted technical solution. For this technology, accurate calibration of the relationship between the characteristics of temperature-sensitive particles and temperature is a crucial means to improve the accuracy of temperature measurement.

[0003] Existing methods for calibrating temperature-sensitive particles generally employ conventional calibration methods, calibrating densely packed temperature-sensitive particles in a static state. CN113945297A proposes a dynamic temperature measurement method for magnetic nanoparticle temperature measurement calibration. This method involves placing a thermocouple sensor and a platinum resistance sensor within the magnetic nanoparticle sample, using the thermocouple sensor to correct the resistance-temperature relationship measured by the platinum resistance sensor to achieve particle calibration. This method applies to resistance-responsive temperature-sensitive particles, and this type of calibration object cannot be used in fluids; therefore, this method cannot be applied to the calibration of temperature-sensitive particles in fluids. CN111373444A proposes an optical calibration device and method that uses a calibration target with a scattered luminescent pattern to simulate particles in a flow field, and uses multiple optical cameras to acquire the optical properties of the simulated particles to achieve calibration. This method relies on a stringent premise: the luminescent pattern must accurately simulate the luminescence state of particles at different locations in the flow field under actual measurement conditions. This premise itself depends on the precise calibration of the temperature-sensitive particle state at different temperatures. Therefore, this method is actually only a rough calibration method for multi-camera optical systems and cannot be used for the calibration of temperature-sensitive particles in the flow field. CN111521297A proposes a spectral-temperature calibration device and method suitable for the phosphorescence specific intensity method. The phosphorescent temperature-sensitive particles are placed statically in a temperature-controlled heating device, and phosphorescence is excited by a beam of a specific wavelength, and phosphorescence spectra at different temperatures are collected. This method is suitable for calibrating temperature-sensitive particles used for temperature measurement in fluids. However, this method does not consider the potential influence of the sparse distribution of particles on the calibration results during actual flow measurement, nor can it avoid the distortion of calibration results caused by the physicochemical properties of the fluid or the optical properties of the wall in actual measurements.

[0004] It is evident that existing temperature-sensitive particle calibration methods do not consider the impact of the actual measurement environment on the reliability of the calibration results. In actual flow field temperature measurements, temperature-sensitive particles are randomly distributed within the fluid being measured at a density far lower than that under calibration conditions. This distribution results in particles operating in diverse fluid environments, significantly affecting their luminescence properties due to the non-uniform optical properties of the flow field and the particle's motion state. For calibration operations requiring high precision, these influences must be taken into account. Therefore, if the adverse effects of non-uniform absorption and refraction of light by the fluid caused by non-uniform flow field properties, as well as signal attenuation and changes in imaging conditions caused by particle distribution, can be reduced or eliminated during the calibration process of temperature-sensitive particles, the accuracy of temperature measurements in fluids can be greatly improved, leading to more precise analysis of temperature distribution in fluids. This will help us understand heat and mass transfer phenomena in fluids from a more scientific perspective, promoting the development of fluid dynamics and the advancement of social productivity. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a temperature-sensitive particle calibration method and system based on a laminar thermal boundary layer, which solves the problems in the prior art where temperature-sensitive particles are randomly distributed in the fluid under test at a distribution density far lower than the calibration state, and the luminescence properties are significantly affected by the non-uniform optical properties in the flow field and the particle motion state.

[0006] Thermosensitive particle calibration experimental device based on laminar thermal boundary layer includes:

[0007] The platform serves as the supporting foundation for the temperature-sensitive particle calibration experimental device;

[0008] A laser, which is fixedly mounted on one side of the top of the platform, is used to generate a laser beam of a specific wavelength;

[0009] A laser shaping lens assembly is fixedly installed on the output path of the laser and is used to shape the laser beam generated by the laser into a sheet-like excitation plate.

[0010] The calibration flow section is installed in the middle of the platform and located on the light-emitting side of the laser shaping lens group. It is used to receive the sheet-like excitation light to excite the temperature-sensitive particles flowing through it. The calibration flow section has a transparent observation window for the incident light of the sheet-like excitation light and the emission signal of the internal particle emission.

[0011] A temperature-controlled storage tank, installed on the other side of the platform, is used to store the working fluid and regulate its temperature;

[0012] An adjustable speed pump, the inlet of which is connected to the outlet of the temperature-controlled storage tank via a flow pipeline, is used to drive the fluid circulation.

[0013] A flow meter, the inlet of which is connected to the outlet of the adjustable speed pump through a flow pipeline, is used to monitor the fluid flow rate in real time;

[0014] The calibrated flow section has its inlet connected to the outlet of the flow meter via a flow pipeline, and its outlet returned to the temperature-controlled storage tank via a flow pipeline, forming a closed-loop circulation flow circuit.

[0015] A temperature control console is electrically connected to the temperature-controlled storage tank and the heater disposed in the calibration flow section, respectively, and is used to control the inlet temperature of the fluid before it enters the calibration flow section and the wall temperature of the calibration flow section.

[0016] A flow control console, electrically connected to the adjustable speed pump and the flow meter, is used to adjust the speed of the adjustable speed pump according to the feedback signal of the flow meter to control the fluid inlet velocity.

[0017] A high-speed camera is mounted on the platform using a fixture and bracket, and is located outside the observation window of the calibration flow section. Its imaging optical axis is perpendicular to the normal of the central plane of the sheet-like excitation light. to The included angle is used to acquire images of the emission of temperature-sensitive particles;

[0018] A computer, which is communicatively connected to the high-speed camera, the temperature control console, and the flow control console, is used to receive and process image data acquired by the high-speed camera to obtain the position and luminescence characteristics of the temperature-sensitive particles, and to analyze and correct the flow field parameters based on the boundary conditions fed back by the temperature control console and the flow control console, and finally establish a mapping function between the luminescence characteristics of the temperature-sensitive particles and the ambient temperature.

[0019] Preferably, the calibration flow section includes:

[0020] The inlet expansion stabilization section has an expansion channel structure and serves as the inlet end for fluid to enter the calibration flow section, thereby reducing fluctuations in the incoming flow velocity.

[0021] An inlet flow equalization plate is installed inside or at the outlet of the inlet expansion and stabilization section to rectify the fluid after expansion, so that the inlet velocity distribution tends to be uniform.

[0022] The calibration test section has its inlet end sealed to the outlet end of the inlet expansion and stabilization section, which is used to contain fluid and form a laminar thermal boundary layer; the calibration test section has a transparent observation wall to allow the incident light of sheet-like excitation light and the emission signal of the internal temperature-sensitive particles.

[0023] An outlet flow equalization plate is installed at the outlet of the calibration test section to maintain the stability of the flow within the calibration test section.

[0024] The outlet contraction and stabilization section has its inlet end sealed to the outlet end of the calibration test section, which is used to guide the fluid to flow smoothly out of the calibration flow section.

[0025] At least one inlet temperature monitoring thermocouple is installed near the inlet of the inlet expansion and stabilization section or the calibration test section to monitor the actual temperature of the fluid before it enters the calibration test section in real time.

[0026] At least one heater is installed inside or outside the wall of the calibration test section to heat the wall of the calibration test section in order to form a stable temperature gradient and laminar thermal boundary layer inside the calibration test section.

[0027] The first elastic sealing heat insulation block is installed at the connection between the calibration test section and the inlet expansion and stabilization section to achieve a sealed connection and reduce heat conduction loss.

[0028] The second elastic sealing heat insulation block is installed at the connection between the calibration test section and the outlet contraction and stabilization section to achieve a sealed connection and reduce heat conduction loss.

[0029] The temperature-sensitive particle calibration method based on laminar thermal boundary layer includes the following steps:

[0030] A stable flow state of laminar thermal boundary layer is constructed using a flow generator, and temperature-sensitive particles to be calibrated are dispersed in the fluid.

[0031] Based on the boundary conditions, the fluid dynamics equations are solved across the entire flow field. The analytical results of the fluid dynamics equations are then corrected based on the fluid dynamics simulation results. Specifically:

[0032] Once the temperature-sensitive particles to be calibrated enter a stable flow state, a set of flow control equations is established based on the structural dimensions of the experimental setup and the boundary condition data obtained by the control device. The established equations are then solved, and a corresponding computational fluid dynamics simulation model is established for simulation calculation. The model is then corrected based on the calculation results.

[0033] The laser is shaped into a sheet-like excitation beam and used to excite temperature-sensitive particles. The position and luminescence characteristics of the temperature-sensitive particles are obtained through data processing.

[0034] Temperature-sensitive particle calibration is achieved by adjusting the flow boundary conditions of the environment in which the temperature-sensitive particles are located.

[0035] Preferably, the stable flow state of the laminar thermal boundary layer constructed using the flow generator is as follows:

[0036] A stable flow environment is constructed using an adjustable-speed pump, a temperature-controlled storage tank, a calibration flow section, and flow piping. Flow rectification is achieved through an inlet expansion flow stabilization section and an inlet flow equalization plate. After the fluid enters the calibration test section, the wall temperature is controlled by a temperature control console. By setting boundary conditions, a stable temperature gradient is formed inside the calibration flow section, and a laminar thermal boundary layer is formed near the wall. Once the stable flow environment is established, temperature-sensitive particles to be calibrated are injected into the temperature-controlled storage tank or flow piping.

[0037] Preferably, the stable flow state is as follows:

[0038] The flow has simple boundary conditions that give its various flow parameters theoretical solutions. The flow is in a laminar state and has a fully developed boundary layer. The flow is steady, and the flow parameters do not change with time under certain boundary conditions. There is a stable temperature gradient in the fluid, the direction and magnitude of which are controlled by the boundary conditions. Temperature-sensitive particles to be calibrated are dispersed in the fluid.

[0039] Preferably, the establishment of the flow control equation set is as follows:

[0040] Once the temperature-sensitive particle to be calibrated enters a stable flow state, the flow control equations are established in the computer, including the continuity equation, momentum equation, and energy equation. Then:

[0041] The continuity equation is the mass conservation equation, which indicates that the fluid mass is conserved, that is, the net flow rate of the fluid per unit volume is zero; the momentum equation is the Navier-Stokes equation, which describes the momentum conservation relationship of the fluid, that is, the velocity change is determined by the pressure gradient and viscous diffusion; the energy equation is the temperature transport equation, which describes that the internal temperature change of the fluid is formed by the combined action of convection and heat conduction.

[0042] Preferably, the solution to the constructed system of equations is as follows:

[0043] In the computer, a three-dimensional coordinate system is established based on the geometry of the calibrated flow section. At the same time, the velocity field function and temperature field function are set along the width direction of the fluid. The inlet conditions, wall conditions and inlet temperature are determined in sequence. Based on the determined inlet conditions, wall conditions and inlet temperature, the velocity distribution function and temperature distribution function in the flow field are determined.

[0044] Preferably, the excitation of the temperature-sensitive particles is specifically as follows:

[0045] The laser generates a laser beam of a specific wavelength. The laser beam enters the laser shaping mirror group and is shaped by the sheet light generator, expanding the original circular laser beam into a sheet-shaped excitation beam. The shaped sheet-shaped excitation beam enters the flow field along the observation window of the calibration flow section and forms a light sheet with a width of 5 to 500 mm and a thickness of 10 μm to 10 mm in the calibration area, which excites the temperature-sensitive particles in the light sheet.

[0046] Preferably, the temperature-sensitive particle calibration is as follows:

[0047] The computer substitutes the spatial coordinates of the particles into the temperature distribution function based on the flow field temperature distribution function, calculates the fluid temperature value at the location of each particle, and changes the flow boundary conditions through the temperature control console and flow control console. After obtaining particle luminescence characteristic data under multiple temperature conditions, the computer uses a data fitting algorithm to perform curve fitting on the relationship between particle luminescence characteristic parameters and ambient temperature, constructs a particle calibration mapping function, and the temperature calibration of temperature-sensitive particles can be achieved based on the constructed mapping function.

[0048] Preferably, the temperature-sensitive particle calibration system based on laminar thermal boundary layer includes: a steady flow field generation module, a flow field parameter calculation module, a calibration data acquisition module, and a calibration function generation module;

[0049] The steady flow field generation module is used to generate a stable flow containing a laminar thermal boundary layer, and forms a calibration environment after dispersing temperature-sensitive particles in the flow cycle.

[0050] The flow field parameter solution module is used to solve the fluid dynamics equations in the entire flow field based on the boundary conditions, and to make corrections based on the computational fluid dynamics simulation results.

[0051] The calibration data acquisition module is used to shape the laser into sheet-like excitation light to excite temperature-sensitive particles;

[0052] The calibration function generation module is used to establish a mapping function between the luminescence characteristics of temperature-sensitive particles and the ambient temperature, thereby enabling the calibration of temperature-sensitive particles.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] 1. This invention achieves a high degree of consistency between the calibration environment and the actual flow field measurement environment by dispersing temperature-sensitive particles in the laminar thermal boundary layer calibration environment. This effectively overcomes the problem of serious discrepancies between the calibration state and the actual measurement state caused by the dense accumulation and static state of particles in traditional static calibration methods, and significantly improves the accuracy of fluid temperature measurement.

[0055] 2. This invention achieves high-precision quantitative characterization of parameters such as velocity and temperature in the flow field by adopting a technique of full-field analytical description of the flow state and correction based on computational fluid dynamics simulation results. This avoids the systematic errors caused by relying solely on theoretical solutions or single measurement points in traditional methods, and provides accurate "real temperature reference values" for temperature-sensitive particles.

[0056] 3. This invention achieves the synchronous excitation and spatial positioning of a large number of temperature-sensitive particles in a sparsely distributed state by combining sheet-like excitation light excitation with high-speed camera imaging. This overcomes the technical bottlenecks of weak particle signals and poor imaging conditions in traditional methods, and significantly improves the acquisition efficiency and spatial resolution of calibration data.

[0057] 4. By adopting the technical means of changing the flow boundary conditions multiple times to allow the temperature-sensitive particles to traverse the target temperature range, this invention achieves full temperature range calibration within a single experimental device, avoiding repeatability errors caused by multiple disassembly and replacement of calibration equipment, and significantly improving the efficiency of the calibration process and the consistency of the data.

[0058] 5. This invention utilizes image processing and data fitting algorithms to automatically extract particle luminescence characteristics and construct mapping functions, achieving fully automated processing from the original image to the calibration curve. This avoids subjective errors caused by human intervention and significantly improves the objectivity and processing efficiency of the calibration data.

[0059] 6. By adopting a closed-loop circulation loop and temperature and flow rate coordinated control, this invention achieves independent adjustment and stable maintenance of multiple boundary conditions such as inlet temperature, wall temperature, and inlet velocity during the calibration process, providing a reliable hardware foundation for constructing a laminar thermal boundary layer with a stable temperature gradient. Attached Figure Description

[0060] Figure 1 A diagram of a temperature-sensitive particle calibration experimental device based on a laminar thermal boundary layer provided in an embodiment of the present invention.

[0061] Figure 2 This is a structural diagram of the calibration flow section in the flow generating device provided in an embodiment of the present invention.

[0062] Figure 3 This is a schematic diagram of the overall method steps of the temperature-sensitive particle calibration method based on laminar thermal boundary layer of the present invention.

[0063] Figure 4 This is a schematic diagram of the overall structure of the temperature-sensitive particle calibration system based on laminar thermal boundary layer of the present invention.

[0064] Figure 5 This is a schematic diagram of the temperature-sensitive particle calibration function provided in an embodiment of the present invention.

[0065] Explanation of reference numerals in the attached figures:

[0066] 1. Laser; 2. Laser shaping mirror assembly; 3. Calibration flow section; 4. Temperature control console; 5. Flow meter; 6. Variable speed pump; 7. Flow control console; 8. High-speed camera; 9. Computer; 10. Temperature-controlled storage tank; 11. Flow pipeline; 12. Equipment fixtures and supports.

[0067] 101. Inlet expansion and stabilization section; 102. Inlet temperature monitoring thermocouple; 103. Inlet flow equalization plate; 104. Calibration test section; 105a. First elastic sealing heat insulation block; 105b. Second elastic sealing heat insulation block; 106. Heater; 107. Outlet flow equalization plate; 108. Outlet contraction and stabilization section. Detailed Implementation

[0068] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0069] Example 1

[0070] Reference Figure 1 As an embodiment of the present invention, a temperature-sensitive particle calibration experimental device based on a laminar thermal boundary layer is provided, comprising:

[0071] The platform serves as the supporting foundation for the temperature-sensitive particle calibration experimental device;

[0072] Laser 1, which is fixedly installed on one side of the top of the platform, is used to generate a laser beam of a specific wavelength;

[0073] The laser shaping mirror assembly 2 is fixedly installed on the output path of the laser 1 and is used to shape the laser beam generated by the laser 1 into a sheet-like excitation plate.

[0074] The calibration flow section 3 is installed in the middle of the platform and located on the light-emitting side of the laser shaping mirror group 2. It is used to receive sheet-like excitation light to excite temperature-sensitive particles flowing through it.

[0075] The calibration flow section 3 has a transparent observation window for the incident light of the sheet-like excitation light and the outgoing light of the internal particle emission signal;

[0076] Temperature-controlled storage tank 10, which is installed on the other side of the platform, is used to store the working fluid and regulate the temperature of the fluid;

[0077] The adjustable speed pump 6 has its inlet connected to the outlet of the temperature-controlled storage tank 10 via the flow pipeline 11, and is used to drive the fluid circulation.

[0078] The flow meter 5, whose inlet is connected to the outlet of the adjustable speed pump 6 through the flow pipe 11, is used to monitor the fluid flow rate in real time.

[0079] The calibrated flow section 3 has its inlet connected to the outlet of the flow meter 5 through the flow pipe 11, and its outlet returns to the temperature-controlled storage tank 10 through the flow pipe 11, forming a closed-loop circulation flow circuit.

[0080] Temperature control console 4 is electrically connected to temperature control storage tank 10 and heater 106 installed in calibration flow section 3, respectively, and is used to control the inlet temperature of the fluid before it enters calibration flow section 3 and the wall temperature of calibration flow section 3.

[0081] The flow control console 7 is electrically connected to the adjustable speed pump 6 and the flow meter 5, and is used to adjust the speed of the adjustable speed pump 6 according to the feedback signal of the flow meter 5 to control the fluid inlet speed.

[0082] The high-speed camera 8 is mounted on the platform via a fixture and support 12, and is located outside the observation window of the calibration flow section 3. Its imaging optical axis is perpendicular to the normal of the central plane of the sheet-like excitation light. to The included angle is used to acquire images of the emission of temperature-sensitive particles;

[0083] Computer 9 is connected to high-speed camera 8, temperature control console 4 and flow control console 7 respectively. It is used to receive and process image data acquired by high-speed camera 8 to obtain the position and luminescence characteristics of temperature-sensitive particles, and to analyze and correct the flow field parameters according to the boundary conditions fed back by temperature control console 4 and flow control console 7. Finally, it establishes a mapping function between the luminescence characteristics of temperature-sensitive particles and ambient temperature.

[0084] Reference Figure 2 This application also provides a structure for calibrating a flow section in a flow generating device, comprising:

[0085] The inlet expansion and stabilization section 101 has an expansion channel structure and serves as the inlet end for fluid to enter the calibration flow section 3, in order to reduce the fluctuation of the incoming flow velocity.

[0086] The inlet flow equalization plate 103 is installed inside the inlet expansion and stabilization section 101 or at the outlet to rectify the fluid after expansion, so that the inlet velocity distribution tends to be uniform.

[0087] The calibration test section 104 has its inlet end sealed to the outlet end of the inlet expansion and stabilization section 101, which is used to contain fluid and form a laminar thermal boundary layer; the calibration test section 104 has a transparent observation wall to allow the sheet-like excitation light to be incident and the emission signal of the internal temperature-sensitive particles to be emitted.

[0088] The outlet flow equalization plate 107 is installed at the outlet of the calibration test section 104 to maintain the stability of the flow within the calibration test section 104.

[0089] The outlet contraction and stabilization section 108 has its inlet end sealed to the outlet end of the calibration test section 104, and is used to guide the fluid to flow smoothly out of the calibration flow section 3;

[0090] At least one inlet temperature monitoring thermocouple 102 is installed near the inlet of the inlet expansion and stabilization section 101 or the calibration test section 104 to monitor the actual temperature of the fluid before it enters the calibration test section 104 in real time.

[0091] At least one heater 106 is installed inside or outside the wall of the calibration test section 104 to heat the wall of the calibration test section 104 in order to form a stable temperature gradient and laminar thermal boundary layer inside the calibration test section 104.

[0092] The first elastic sealing heat insulation block 105a is installed at the connection between the calibration test section 104 and the inlet expansion and stabilization section 101 to achieve a sealed connection and reduce heat conduction loss.

[0093] The second elastic sealing heat insulation block 105b is installed at the connection between the calibration test section 104 and the outlet contraction and stabilization section 108 to achieve a sealed connection and reduce heat conduction loss.

[0094] Reference Figure 3 The present invention also provides a method for calibrating temperature-sensitive particles based on laminar thermal boundary layers, comprising the following steps:

[0095] Step S1: Use a flow generator to create a stable flow state containing a laminar thermal boundary layer, and disperse the temperature-sensitive particles to be calibrated in the fluid.

[0096] Specifically, the stable flow state including a laminar thermal boundary layer is generated using a flow generator. This is achieved by constructing a stable flow environment through a steady flow field generation module. The flow generator, consisting of an adjustable-speed pump 6, a temperature-controlled storage tank 10, a calibrated flow section 3, and a flow pipeline 11, forms a closed-loop circulation circuit. Therefore:

[0097] The temperature-controlled storage tank 10 is used to store the working fluid and adjust the initial temperature of the fluid through the temperature control console 4 so that the fluid reaches the set inlet temperature before entering the flow circuit. Subsequently, the adjustable speed pump 6 drives the fluid to circulate along the pipeline under the control of the flow control console 7, and the fluid flow rate and inlet velocity are monitored in real time through the flow meter 5.

[0098] In addition, before entering the calibration flow section 3, the fluid undergoes flow rectification through the inlet expansion stabilization section 101 and the inlet flow equalization plate 103, making the inlet velocity distribution more uniform and thus reducing turbulence disturbance. Subsequently, the fluid enters the calibration test section, where heaters 6 are installed on the wall and the wall temperature is controlled by the temperature control console 4. By setting boundary conditions such as inlet temperature, wall temperature, and inlet velocity, a stable temperature gradient is formed inside the calibration flow section 3, and a laminar thermal boundary layer structure is formed near the wall.

[0099] Furthermore, once a stable flow environment is formed, temperature-sensitive particles (such as temperature-sensitive fluorescent particles or temperature-sensitive phosphorescent particles) to be calibrated are injected into the temperature-controlled storage tank 10 or the flow pipeline 11, and the particles are uniformly dispersed by means of fluid circulation. This allows the temperature-sensitive particles to enter the calibration flow section 3 in a sparse distribution state with the fluid, thereby forming a particle distribution state consistent with the actual measurement environment inside the flow field.

[0100] It should be noted that the designed closed-loop flow loop structure can form a laminar thermal boundary layer flow state with a stable velocity field and temperature gradient in the calibration flow section 3, providing a standard flow field environment for subsequent temperature-sensitive particle calibration.

[0101] The stable flow state generated by the flow generating device can have the following preferred characteristics:

[0102] The flow has simple boundary conditions, which give its various flow parameters theoretical solutions.

[0103] The flow is in a laminar state and has a fully developed boundary layer;

[0104] The flow is steady; under defined boundary conditions, the flow parameters do not change with time.

[0105] A stable temperature gradient exists within the fluid, the direction and magnitude of which are controlled by boundary conditions; temperature-sensitive particles to be calibrated are dispersed within the fluid.

[0106] Step S2: Solve the basic equations of fluid dynamics in the entire flow field according to the boundary conditions, and correct the analytical description based on the results of computational fluid dynamics simulation.

[0107] Specifically, the fundamental equations of fluid mechanics are solved across the entire flow field based on boundary conditions. This is achieved through theoretical modeling and calculation of the flow field using a flow field parameter solution module, which consists of a computer 9 and its internal fluid solver program, as detailed below:

[0108] Once the temperature-sensitive particles to be calibrated enter a stable flow state, based on the structural dimensions of the experimental setup and the boundary condition data (including inlet velocity, inlet temperature, wall temperature, and outlet pressure) obtained by the control device, a set of flow control equations is established in computer 9, including: continuity equation, momentum equation, and energy equation, as detailed below:

[0109] The continuity equation is the mass conservation equation, which means that the fluid mass is conserved, i.e., the net flow rate of the fluid per unit volume is zero. Therefore:

[0110] ;

[0111] ;

[0112] The momentum equation is the Navier-Stokes equation, used to describe the conservation of fluid momentum, i.e., the velocity change is determined by both the pressure gradient and viscous diffusion. Therefore:

[0113] ;

[0114] The energy equation is the temperature transport equation, used to describe how temperature changes within a fluid are caused by the combined effects of convection and conduction. Therefore:

[0115] ;

[0116] in, Represents the fluid velocity vector. Let represent the velocity component in the x-direction, represent the velocity component in the y-direction, and represent the velocity component in the z-direction. Denotes the divergence operator, Indicates fluid density, Indicates fluid pressure. Indicates the dynamic viscosity of a fluid. Indicates the pressure gradient. Represents the Laplace operator. Indicates fluid temperature. This represents the specific heat capacity of a fluid at constant pressure. Indicates the thermal conductivity of a fluid. Indicates the heat transfer term. This represents the thermal diffusion term.

[0117] Under steady-state flow conditions, neglecting the time term, the equations are constructed as a system of steady-state differential equations containing only spatial variables. The geometry of the calibration flow section 3 is used as the spatial boundary condition for solving, thereby obtaining the velocity distribution function and temperature distribution function in the flow field, as follows:

[0118] In computer 9, a three-dimensional coordinate system is established based on the geometry of the calibration flow section 3. ,in, Indicates the coordinates of the main flow direction. Represents the normal coordinates perpendicular to the wall. Indicates the coordinates in the width direction;

[0119] velocity distribution along The direction changes, and the velocity field function is: The temperature field function is ;

[0120] The inlet conditions, wall conditions, and inlet temperature are determined sequentially, as follows:

[0121] Entry requirements are:

[0122] ;

[0123] The wall conditions are:

[0124] ;

[0125] ;

[0126] The inlet temperature is:

[0127] ;

[0128] in, Indicates the inlet velocity. Indicates the inlet temperature. Indicates wall temperature;

[0129] To obtain the velocity distribution function and temperature distribution function in the flow field, specifically:

[0130] The velocity distribution function is then:

[0131] ;

[0132] ;

[0133] in, Represents the velocity distribution function. This represents the temperature distribution function.

[0134] Furthermore, a corresponding computational fluid dynamics (CFD) simulation model was established in Computer 9, and numerical simulation calculations were performed based on the geometric dimensions of the experimental setup, fluid properties, and boundary conditions. Temperature and velocity distribution data at discrete locations in the flow field were obtained through simulation, and these discrete data were compared with the theoretical analytical solution. The results are as follows:

[0135] When there are discrepancies between the analytical results and the simulation results, the flow field temperature distribution function is corrected by introducing correction coefficients or piecewise functions into the analytical expression, thereby obtaining a more accurate analytical description model of the entire field temperature, as follows:

[0136] A corresponding computational fluid dynamics (CFD) simulation model was established in Computer 9, and the discrete solution of the flow field was obtained through the grid discretization method, specifically:

[0137] Set the temperature value obtained from the CFD calculation to After parsing, it becomes ;

[0138] The difference between the two is:

[0139] ;

[0140] Introducing a correction coefficient into the analytical expression, we have:

[0141] ;

[0142] in, This represents the corrected temperature distribution function. This represents the temperature function obtained through analytical solution. Indicates simulation deviation, This indicates the adjustment of the weighting coefficient;

[0143] We can also use piecewise functions for correction, then we have:

[0144] ;

[0145] in, , This represents the position correction factor. , Indicates the gradient correction coefficient. This indicates the thickness of the thermal boundary layer.

[0146] Based on the simulation results, the velocity distribution function and temperature distribution function within the calibration flow section 3 are determined as follows:

[0147] The velocity distribution function, used to describe the process of a fluid forming a velocity boundary layer near a wall, is as follows:

[0148] ;

[0149] The temperature distribution function, used to represent the thermal boundary layer structure where the temperature gradually decreases from the wall to the fluid interior, is as follows:

[0150] ;

[0151] in, Indicates the inlet velocity. This represents the velocity gradient decay coefficient. Indicates the distance from the wall. Indicates the inlet temperature. Indicates the wall temperature. This represents the temperature decay coefficient.

[0152] It should be noted that once the temperature distribution function is determined, the spatial coordinates of the temperature-sensitive particles in the image are used as the basis for this. Calculating the ambient temperature at the particle's location, we have:

[0153] ;

[0154] in, Indicates the spatial position of the particle. This represents the ambient temperature of the particles, serving as a true temperature reference value for calibrating the particle luminescence characteristics.

[0155] Step S3: Shape the laser into a sheet-like excitation beam and use it to excite temperature-sensitive particles, and obtain the position and luminescence characteristics of the temperature-sensitive particles through data processing.

[0156] Specifically, after the flow field parameters are analyzed, the temperature-sensitive particles in the flow field are optically excited and imaged using a calibration data acquisition module.

[0157] Laser 1 generates a laser beam of a specific wavelength (wavelength range 200nm~1200nm), the laser beam enters the laser shaping mirror group 2, and is shaped by a cylindrical lens or sheet light generator to expand the original circular laser beam into a sheet-like excitation beam with a certain thickness.

[0158] The shaped sheet-like excitation light enters the flow field through the observation window of the calibration flow section 3, and forms a light sheet with a width of 5 to 500 mm and a thickness of 10 μm to 10 mm in the calibration area, which excites the temperature-sensitive particles in the light sheet.

[0159] It should be noted that when temperature-sensitive particles are excited by laser, they will produce a temperature-related luminescence response, such as changes in fluorescence intensity, changes in phosphorescence decay time, or changes in spectral peaks.

[0160] Furthermore, the specific technical parameters of the sheet-like excitation light are as follows:

[0161] The laser wavelength constituting the sheet-like excitation beam is 200~1200nm to efficiently excite temperature-sensitive particles; the laser constituting the sheet-like excitation beam operates in a preferred emission mode, capable of exciting particles through continuous or pulsed emission; the pulsed emission has preferred pulse energy, frequency, waveform, and duty cycle to meet the calibration requirements, with a pulse energy of 10μJ~10J, a pulse frequency of 1Hz~10kHz, and pulse waveforms including but not limited to rectified sine waves, square waves, triangular waves, sawtooth waves, etc., and a pulse duty cycle of 5%~95%; the sheet-like excitation beam has a preferred geometry, with a thickness of 10μm~10mm and a width of 5~500mm in the calibration area; the central plane of the sheet-like excitation beam is parallel to the observation surface of the flow device for convenient observation.

[0162] At the same time, in the direction of the normal to the central plane of the sheet-like excitation light to A high-speed camera 8 is positioned at the angle. A filter with a specific transmission wavelength range is installed at the front of the camera to filter the excitation light and retain only the emission signal of the temperature-sensitive particles. The high-speed camera 8 continuously captures images of the calibration area at a frame rate of 1Hz to 10kHz to obtain the original image sequence of the temperature-sensitive particles.

[0163] In addition, the image processing program in Computer 9 processes the acquired image sequence, including: image denoising and background subtraction, particle recognition and particle center localization, particle optical feature extraction, and particle emission time decay curve fitting, as detailed below:

[0164] Image denoising and background removal involves denoising and removing background from the acquired image sequence, as detailed below:

[0165] The original image sequence of the temperature-sensitive particles obtained. The background image collected before the experiment began was set as follows: ;

[0166] The image after background subtraction is:

[0167] ;

[0168] To further reduce the impact of noise, a two-dimensional Gaussian filter can be used for smoothing.

[0169] ;

[0170] The Gaussian filter kernel is:

[0171] ;

[0172] in, This represents the gray-level distribution function of the original image. This represents the grayscale distribution of the background image. This represents the image after background removal. This represents the image after denoising. This represents the convolution operator. This represents the Gaussian filter kernel function. This represents the standard deviation of the Gaussian filter, used to control the smoothing level.

[0173] Particle recognition and particle center localization involve thresholding the denoised image to achieve particle recognition and localization, as detailed below:

[0174] Let the threshold be T, then the particle region determination function is:

[0175] ;

[0176] in, This indicates that the pixel at the corresponding position belongs to the particle region. This represents the background area, and T represents the set threshold.

[0177] Once the particle region is identified, the particle center coordinates are determined using the gray-scale weighted centroid method, resulting in:

[0178] Regarding the first There are 1 particle, and its center position is:

[0179] ;

[0180] ;

[0181] in, Indicates the first The pixel region corresponding to each particle Represents the denoised image Indicates the first The coordinates of the particle center of each particle.

[0182] Particle optical feature extraction involves calculating the average fluorescence intensity of the identified particles, specifically:

[0183] ;

[0184] in, Indicates the average luminous intensity of the particles. This indicates the number of pixels within a particle region.

[0185] Particle emission time decay curve fitting is achieved by calculating fluorescence decay to fit the particle emission time decay curve, specifically as follows:

[0186] ;

[0187] in, (t) represents the particle in The luminous intensity at any given moment This indicates the initial luminescence intensity of the particle. Let represent the decay time constant of particle luminescence, which is obtained by fitting using the least squares method, then:

[0188] ;

[0189] in, This represents the particle emission decay curve. This indicates the initial luminescence intensity of the particle. This represents the k-th sampling time. Indicates the number of time sampling points. This represents the particle emission decay time constant.

[0190] Once the data processing is complete, a particle optical feature dataset is constructed based on the spatial coordinates and luminescence characteristic parameters of each temperature-sensitive particle. Then:

[0191] ;

[0192] ;

[0193] in, This represents the constructed particle optical feature dataset. Indicates the first The feature vector of each particle This represents the total number of particles. Represents the spatial coordinates of the particle. Indicates average luminous intensity. Indicates the spectral intensity ratio. Represents the light emission decay time constant. This represents the particle spectral distribution function.

[0194] It should be noted that the luminescence properties of temperature-sensitive particles can be one of the following or any combination thereof, specifically:

[0195] The refraction, reflection, and scattering characteristics of temperature-sensitive particles to excitation light; ultraviolet, visible, and infrared spectral curves of temperature-sensitive particles under excitation light; the position and intensity of a single peak in the spectrum of temperature-sensitive particles under excitation light; the relative positions and intensity ratios of multiple peaks in the spectrum of temperature-sensitive particles under excitation light; the rise curve and time constant of temperature-sensitive particles under excitation light; the saturation intensity of temperature-sensitive particles under excitation light; the decay curve and time constant of temperature-sensitive particles under excitation light, etc.

[0196] Step S4: Achieve temperature-sensitive particle calibration by adjusting the flow boundary conditions of the ambient temperature of the temperature-sensitive particles.

[0197] After obtaining the spatial location and luminescence characteristics of the particles, the relationship between the particle luminescence characteristics and the ambient temperature is established through the calibration function generation module, specifically:

[0198] First, computer 9, based on the flow field temperature distribution function obtained in step S2, substitutes the particle spatial position coordinates obtained in step S3 into the temperature distribution function to calculate the fluid temperature value at the location of each particle. Then:

[0199] Subsequently, the flow boundary conditions are changed by temperature control console 4 and flow control console 7, such as adjusting the variable speed pump 6 to change the inlet velocity, adjusting the temperature control tank 10 to change the inlet temperature, and adjusting the heater of the calibrated flow section 3 to change the wall temperature.

[0200] By repeatedly changing the boundary conditions, the temperature distribution in the flow field is altered, thereby allowing the temperature-sensitive particles to traverse the target calibration temperature range.

[0201] In addition, after each change in boundary conditions, steps S2 and S3 are repeated to obtain new particle luminescence characteristic data and corresponding temperature values, and the data is recorded.

[0202] It should be noted that the changes in flow boundary conditions follow the following principles:

[0203] The change of boundary conditions should enable the ambient temperature of the temperature-sensitive particles to traverse the calibrated target temperature range; the aforementioned stable flow state is a laminar flow state, and the Reynolds number is its main dimensionless characteristic number; the change of boundary conditions is mainly controlled by the Reynolds number, with the Reynolds number control range being 10~2000; for a given flow generating device, its characteristic scale is determined, and the inlet velocity is the main boundary condition controlling the Reynolds number; the inlet temperature and wall temperature can determine the fluid's average density and viscosity, thereby regulating the Reynolds number, and are also boundary conditions controlling the Reynolds number; the inlet velocity adjustment range is 0~50 m / s, the inlet temperature adjustment range is 5~200℃, and the wall temperature adjustment range is 0~800℃; the Prandtl number is an important dimensionless number characterizing the aforementioned laminar thermal boundary layer characteristics, and the Prandtl number is calculated and checked after each change of boundary conditions, with the Prandtl number control range being 0.1~10.

[0204] After obtaining particle luminescence characteristic data under multiple temperature conditions, the data fitting algorithm in the computer is used to perform curve fitting on the relationship between particle luminescence characteristic parameters and ambient temperature, and a particle calibration mapping function is constructed. Then:

[0205] ;

[0206] in, This indicates the temperature of the environment in which the particle exists. Parameters representing the luminescence properties of particles (such as light intensity, spectral peak value, or decay time constant).

[0207] refer to Figure 5 Based on the constructed mapping function, the temperature of the temperature-sensitive particles can be calibrated. This allows for the measurement of the particles' luminescence characteristics during actual flow field temperature measurement, and the inverse calculation of the fluid temperature where the temperature-sensitive particles are located. Specifically:

[0208] The calibration object is MFG thermosensitive phosphorescent particles (particle size distribution range 1-50 μm, excitation wavelength adaptation range 200-1200 nm) dispersed in silicone oil flow. The luminescence characteristics of the calibrated thermosensitive particles are the decay time constant of the thermosensitive particles under excitation light, then:

[0209] The heater temperature in the calibration flow section 3 was controlled at 175℃, the flow inlet temperature at 25℃, and the flow inlet velocity at 0.1m / s. The calculated flow Reynolds number was 1016~1992 and the Prandtl number was 0.42~0.14, which met the calibration requirements.

[0210] The analytical description of the full-field parameters of the flow field is obtained by calculation. The laser wavelength of the sheet-like excitation light is 405nm and it operates in pulse emission mode. The pulse energy is 10mJ, the pulse frequency is 10Hz, and the pulse waveform is a square wave with a duty cycle of 50%.

[0211] The sheet-like excitation material is 1 mm thick and spreads 500 mm in the calibration area.

[0212] The decay time constant of the excited light of the temperature-sensitive particles at each position in the flow field is extracted from the image sequence acquired by the high-speed camera 8 and correlated with the flow field temperature at the corresponding position; the (decay time constant, temperature) data points are plotted on the calibration function graph and fitted with a linear function to obtain the calibration function graph of the temperature-sensitive particles.

[0213] Example 2

[0214] Reference Figure 4 As an embodiment of the present invention, a temperature-sensitive particle calibration system based on a laminar thermal boundary layer is provided, including: a steady flow field generation module, a flow field parameter calculation module, a calibration data acquisition module, and a calibration function generation module;

[0215] Specifically, the steady flow field generation module generates a stable flow containing a laminar thermal boundary layer, dispersing temperature-sensitive particles in the flow cycle to form a calibration environment; the flow field parameter calculation module solves the basic fluid dynamics equations across the entire flow field based on boundary conditions, providing a full-field analytical description of parameters such as velocity and temperature in the flow state, and making corrections based on computational fluid dynamics simulation results; the calibration data acquisition module shapes the laser into sheet-like excitation light to excite the temperature-sensitive particles, places a high-speed camera 8 with a filter at an optimal position to capture calibration images, and uses an image processing program to acquire the position and luminescence characteristics of the temperature-sensitive particles from the calibration images; the calibration function generation module repeatedly changes the boundary conditions of the aforementioned flow state to make the ambient temperature of the temperature-sensitive particles traverse the target temperature range, obtains the ambient temperature of the particles based on the aforementioned analytical description, establishes a mapping function characterization between the luminescence characteristics of the temperature-sensitive particles and the ambient temperature, and realizes the calibration of the temperature-sensitive particles.

[0216] Furthermore, the steady flow field generation module includes a flow generation device comprising an adjustable speed pump, a calibration flow section 3, and a temperature-controlled storage tank, which generates a stable flow state containing a laminar thermal boundary layer. The flow generation device, in conjunction with the control device and auxiliary devices, adjusts parameters such as inlet velocity, inlet temperature, and wall temperature to ensure that the flow is a steady laminar flow with a controllable temperature gradient, and that the Reynolds number and Prandtl number meet the calibration requirements. Temperature-sensitive particles are uniformly distributed in the fluid.

[0217] Subsequently, the flow field parameter solution module combines the continuity equation, momentum equation, and energy equation to form a set of differential equations, and solves them according to the boundary conditions to obtain the analytical expressions of the flow parameters. At the same time, a computational fluid dynamics simulation model is established to obtain discrete temperature field data, and the analytical solution is corrected by adding correction terms to obtain an accurate description of the temperature distribution throughout the entire field.

[0218] During the measurement phase, the calibration data acquisition module adopts an architecture including a laser 1, a sheet light generator, and a high-speed camera 8. A laser of a specific wavelength, after being shaped, forms a sheet-like excitation light of a preferred thickness at a preferred location, exciting temperature-sensitive particles in continuous or pulsed mode. The high-speed camera 8 is positioned at the preferred location and, in conjunction with a filter, captures the particle emission signal. After the image processing program extracts the spatial position and emission characteristics of the particles from the original image, the calibration function generation module establishes a mapping function relationship between the emission characteristic parameters and the ambient temperature under full operating conditions across the target temperature range experienced by the temperature-sensitive particles, thus achieving temperature-sensitive particle calibration.

[0219] The system achieves precise control over the entire process, from flow field parameter adjustment, laser excitation control, image acquisition and processing to calibration function generation. It effectively overcomes the optical distortion and signal interference caused by non-uniform flow field and sparse particle distribution in traditional calibration and measurement environments by using a laminar thermal boundary layer calibration environment. It is suitable for the accurate calibration of various temperature-sensitive particles and provides a reliable data benchmark for fluid temperature field measurement.

[0220] Furthermore, if the functionality is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0221] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0222] More specific examples (a non-exhaustive list) of computer-readable media include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0223] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A temperature-sensitive particle calibration experimental device based on laminar thermal boundary layer, characterized in that: include: The platform serves as the supporting foundation for the temperature-sensitive particle calibration experimental device; A laser (1) is fixedly mounted on one side of the top of the platform and is used to generate a laser beam of a specific wavelength; The laser shaping lens assembly (2) is fixedly installed on the output path of the laser (1) and is used to shape the laser beam generated by the laser (1) into a sheet-like excitation plate. The calibration flow section (3) is installed in the middle of the platform and located on the light-emitting side of the laser shaping lens group (2). It is used to receive the sheet-like excitation light to excite the temperature-sensitive particles flowing through it. The calibration flow section (3) has a transparent observation window for the incident light of the sheet-like excitation light and the emission signal of the internal particle light. Temperature-controlled storage tank (10), which is installed on the other side of the platform, is used to store working fluid and regulate the temperature of the fluid; An adjustable speed pump (6) has its inlet connected to the outlet of the temperature-controlled storage tank (10) via a flow pipe (11) to drive fluid circulation. The flow meter (5) has its inlet connected to the outlet of the adjustable speed pump (6) via a flow pipe (11) for real-time monitoring of fluid flow. The inlet of the calibrated flow section (3) is connected to the outlet of the flow meter (5) through the flow pipe (11), and its outlet flows back to the temperature-controlled storage tank (10) through the flow pipe (11), forming a closed-loop circulation flow circuit. The calibration flow section (3) includes: The inlet expansion stabilization section (101) has an expansion channel structure and serves as the inlet end for fluid to enter the calibration flow section (3) to reduce the fluctuation of the incoming flow velocity; An inlet flow equalization plate (103) is installed inside or at the outlet of the inlet expansion and stabilization section (101) to rectify the expanded fluid and make the inlet velocity distribution more uniform. The calibration test section (104) has its inlet end sealed to the outlet end of the inlet expansion and stabilization section (101) for containing fluid and forming a laminar thermal boundary layer; the calibration test section (104) has a transparent observation wall for the incident light of sheet-like excitation light and the emission signal of the internal temperature-sensitive particles. An outlet flow equalization plate (107) is installed at the outlet of the calibration test section (104) to maintain the stability of the flow within the calibration test section (104); The outlet contraction and stabilization section (108) has its inlet end sealed to the outlet end of the calibration test section (104) to guide the fluid to flow smoothly out of the calibration flow section (3). At least one inlet temperature monitoring thermocouple (102) is installed near the inlet of the inlet expansion and stabilization section (101) or the calibration test section (104) to monitor the actual temperature of the fluid before it enters the calibration test section (104) in real time. At least one heater (106) is installed inside or outside the wall of the calibration test section (104) to heat the wall of the calibration test section (104) to form a stable temperature gradient and laminar thermal boundary layer inside the calibration test section (104). The first elastic sealing heat insulation block (105a) is installed at the connection between the calibration test section (104) and the inlet expansion stabilization section (101) to achieve a sealed connection and reduce heat conduction loss; The second elastic sealing heat insulation block (105b) is installed at the connection between the calibration test section (104) and the outlet contraction and stabilization section (108) to achieve a sealed connection and reduce heat conduction loss; Temperature control console (4) is electrically connected to the temperature control tank (10) and the heater (106) installed in the calibration flow section (3), respectively, and is used to control the inlet temperature of the fluid before it enters the calibration flow section (3) and the wall temperature of the calibration flow section (3); A flow control console (7) is electrically connected to the adjustable speed pump (6) and the flow meter (5) for adjusting the speed of the adjustable speed pump (6) according to the feedback signal of the flow meter (5) to control the fluid inlet speed. A high-speed camera (8) is mounted on the platform via a device clamp and bracket (12) and is located outside the observation window of the calibration flow section (3). Its imaging optical axis is perpendicular to the normal of the central plane of the sheet-like excitation light. to The included angle is used to acquire images of the emission of temperature-sensitive particles; Computer (9) is connected to the high-speed camera (8), the temperature control console (4) and the flow control console (7) respectively. It is used to receive and process the image data collected by the high-speed camera (8) to obtain the position and luminescence characteristics of the temperature-sensitive particles. It analyzes and corrects the flow field parameters according to the boundary conditions fed back by the temperature control console (4) and the flow control console (7), and finally establishes a mapping function between the luminescence characteristics of the temperature-sensitive particles and the ambient temperature.

2. A temperature-sensitive particle calibration method based on a laminar thermal boundary layer, applicable to the temperature-sensitive particle calibration experimental apparatus based on a laminar thermal boundary layer as described in claim 1, characterized in that: Includes the following steps: A stable flow state of laminar thermal boundary layer is constructed using a flow generator, and temperature-sensitive particles to be calibrated are dispersed in the fluid. Based on the boundary conditions, the fluid dynamics equations are solved across the entire flow field. The analytical results of the fluid dynamics equations are then corrected based on the fluid dynamics simulation results. Specifically: Once the temperature-sensitive particles to be calibrated enter a stable flow state, a set of flow control equations is established based on the structural dimensions of the experimental setup and the boundary condition data obtained by the control device. The established equations are then solved, and a corresponding computational fluid dynamics simulation model is established for simulation calculation. The model is then corrected based on the calculation results. The laser is shaped into a sheet-like excitation beam and used to excite temperature-sensitive particles. The position and luminescence characteristics of the temperature-sensitive particles are obtained through data processing. Temperature-sensitive particle calibration is achieved by adjusting the flow boundary conditions of the environment in which the temperature-sensitive particles are located.

3. The temperature-sensitive particle calibration method based on laminar thermal boundary layer as described in claim 2, characterized in that: The stable flow state of constructing a laminar thermal boundary layer using a flow generator is as follows: A stable flow environment is constructed by an adjustable speed pump (6), a temperature-controlled storage tank (10), a calibration flow section (3), and a flow pipeline (11). The flow is rectified by the inlet expansion flow stabilization section (101) and the inlet flow equalization plate (103). When the fluid enters the calibration test section (104), the wall temperature is controlled by the temperature control console (4). By setting boundary conditions, a stable temperature gradient is formed inside the calibration flow section (3), and a laminar thermal boundary layer is formed near the wall. After the stable flow environment is formed, the temperature-sensitive particles to be calibrated are injected into the temperature-controlled storage tank (10) or the flow pipeline (11).

4. The temperature-sensitive particle calibration method based on laminar thermal boundary layer as described in claim 3, characterized in that: The stable flow state is as follows: The flow has simple boundary conditions that provide theoretical solutions for its various flow parameters; the flow is in a laminar state and has a fully developed boundary layer; the flow is steady, and the flow parameters do not change with time under defined boundary conditions; a stable temperature gradient exists within the fluid, the direction and magnitude of which are controlled by the boundary conditions; and temperature-sensitive particles to be calibrated are dispersed within the fluid.

5. The temperature-sensitive particle calibration method based on laminar thermal boundary layer as described in claim 4, characterized in that: The establishment of the flow control equation set is as follows: Once the temperature-sensitive particle to be calibrated enters a stable flow state, the flow control equations are established in the computer (9), including the continuity equation, momentum equation, and energy equation, then: The continuity equation is the mass conservation equation, which indicates that the fluid mass is conserved, that is, the net flow rate of the fluid per unit volume is zero; the momentum equation is the Navier-Stokes equation, which describes the momentum conservation relationship of the fluid, that is, the velocity change is determined by the pressure gradient and viscous diffusion; the energy equation is the temperature transport equation, which describes that the internal temperature change of the fluid is formed by the combined action of convection and heat conduction.

6. The temperature-sensitive particle calibration method based on laminar thermal boundary layer as described in claim 5, characterized in that: The solution to the constructed system of equations is as follows: In the computer (9), a three-dimensional coordinate system is established according to the geometric structure of the calibrated flow section (3). At the same time, the velocity field function and temperature field function are set along the width direction of the fluid, and the inlet conditions, wall conditions and inlet temperature are determined in sequence. Based on the determined inlet conditions, wall conditions and inlet temperature, the velocity distribution function and temperature distribution function in the flow field are determined.

7. The temperature-sensitive particle calibration method based on laminar thermal boundary layer as described in claim 6, characterized in that: The specific details of exciting the temperature-sensitive particles are as follows: The laser (1) generates a laser beam of a specific wavelength. The laser beam enters the laser shaping mirror group (2) and is shaped by the sheet light generator to expand the original circular laser beam into a sheet-shaped excitation beam. The shaped sheet-shaped excitation beam enters the flow field through the observation window of the calibration flow section (3) and forms a light sheet with a width of 5 to 500 mm and a thickness of 10 μm to 10 mm in the calibration area, which excites the temperature-sensitive particles in the light sheet.

8. The temperature-sensitive particle calibration method based on laminar thermal boundary layer as described in claim 7, characterized in that: The temperature-sensitive particle calibration is as follows: The computer (9) substitutes the spatial coordinates of the particles into the temperature distribution function according to the flow field temperature distribution function, calculates the fluid temperature value at the location of each particle, changes the flow boundary conditions through the temperature control console (4) and the flow control console (7), and after obtaining the particle luminescence characteristic data under multiple temperature conditions, the computer (9) uses the data fitting algorithm to perform curve fitting on the relationship between the particle luminescence characteristic parameters and the ambient temperature, constructs the particle calibration mapping function, and the temperature calibration of the temperature-sensitive particles can be realized based on the constructed mapping function.

9. A system employing the temperature-sensitive particle calibration method based on laminar thermal boundary layer as described in any one of claims 2 to 8, characterized in that, include: The system includes a steady flow field generation module, a flow field parameter calculation module, a calibration data acquisition module, and a calibration function generation module. The steady flow field generation module is used to generate a stable flow containing a laminar thermal boundary layer, and forms a calibration environment after dispersing temperature-sensitive particles in the flow cycle. The flow field parameter solution module is used to solve the fluid dynamics equations in the entire flow field based on the boundary conditions, and to make corrections based on the computational fluid dynamics simulation results. The calibration data acquisition module is used to shape the laser into sheet-like excitation light to excite temperature-sensitive particles; The calibration function generation module is used to establish a mapping function between the luminescence characteristics of temperature-sensitive particles and the ambient temperature, thereby enabling the calibration of temperature-sensitive particles.

Images