Flow measuring device and method based on fluorescent tracer time difference method
By integrating symmetrically arranged dual fluorescence detection units with a U-shaped detection trough, the measurement problem of traditional fluorescent tracer time-of-flight method under low flow rate and micro-flow conditions is solved, realizing high-sensitivity flow measurement and zero-flow rate identification, adapting to complex environments, and reducing equipment costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG XIAOQIAO LIUSHUI ENVIRONMENTAL TECH CO LTD
- Filing Date
- 2026-03-06
- Publication Date
- 2026-05-12
AI Technical Summary
Traditional flow measurement techniques based on the time difference method using fluorescent tracers suffer from problems such as insufficient signal response, complex and costly equipment, insufficient anti-interference ability, and difficulty in identifying zero flow velocity and bidirectional flow under low flow velocity and micro flow conditions.
The integrated design of symmetrically arranged dual fluorescence detection units and U-shaped detection groove enables flow rate calculation, flow direction determination, and zero flow rate identification by accurately recording fluorescence signal characteristic parameters.
It achieves high-sensitivity flow measurement under low flow rate and micro-flow conditions, can accurately identify zero flow rate and bidirectional flow, adapts to complex environments, and reduces equipment costs.
Smart Images
Figure CN122015980A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fluid measurement technology, and particularly to a flow measurement device and method based on the fluorescent tracer time-of-flight method. This device and method are suitable for measuring fluid velocity and direction in fields such as online environmental monitoring (e.g., groundwater infiltration monitoring), and can uniquely identify zero-velocity (static) states. Specifically, this invention, through the synergistic design of symmetrically arranged dual fluorescent detection units and a U-shaped detection trough, combined with the injection of fluorescent tracers and precise time-of-flight detection, achieves accurate identification and measurement of micro-flow, bidirectional flow, and static fluids, overcoming the limitations of traditional flow measurement techniques based on the fluorescent tracer time-of-flight method under low-velocity conditions. Background Technology
[0002] Flow measurement based on the time-of-flight method using fluorescent tracers has wide applications in water conservancy engineering, environmental monitoring, and industrial production. Traditional flow measurement instruments based on the time-of-flight method using fluorescent tracers (such as Pitot tubes and turbine flow meters) rely on the principles of fluid dynamic pressure or mechanical motion. Under low flow rate / micro-flow conditions, insufficient signal response leads to measurement failure. High-precision optical equipment such as laser Doppler current meters (LDA) are complex in structure and expensive, making them difficult to adapt to field environments. Ultrasonic flow meters are susceptible to interference from bubbles and temperature changes at micro-flow rates, and suffer from problems such as difficulty in capturing time differences and waveform distortion.
[0003] Micro-flow measurement based on the time-of-flight method using fluorescent tracers (such as groundwater infiltration and thin-layer flow on slopes) requires extremely high equipment sensitivity and bidirectional flow detection capabilities. However, existing flowmeters are limited by minimum detection limits, making it difficult to meet these requirements. Although the fluorescence detection method has been introduced into this field due to its high sensitivity, existing solutions have significant drawbacks: single-point / asymmetric detection cannot determine flow direction and zero-velocity states, and it is easy to misinterpret the diffusion signal of tracers in stagnant fluids as low flow velocity; some systems rely on mechanical structures, failing to truly solve the flow measurement challenges of micro-flow measurement based on the time-of-flight method using fluorescent tracers, and their anti-interference capabilities and environmental adaptability are insufficient.
[0004] In view of the shortcomings of existing technologies, there is an urgent need in the field for a flow measurement scheme based on the fluorescent tracer time difference method that combines high sensitivity, low cost, strong environmental adaptability, and the ability to achieve bidirectional flow detection and zero flow velocity identification. Summary of the Invention
[0005] This invention proposes a flow measurement device and method based on the time difference method of fluorescent tracers. The core of the method lies in the integrated design of symmetrically arranged dual fluorescent detection units and U-shaped detection grooves. By accurately recording the characteristic parameters of the fluorescent signal, the flow velocity can be calculated, the flow direction can be determined, and the zero flow velocity can be identified.
[0006] This invention proposes a flow measurement device and method based on the time difference method of fluorescent tracers. The core of the method lies in the integrated design of symmetrically arranged dual fluorescent detection units and U-shaped detection grooves. By accurately recording the characteristic parameters of the fluorescent signal, the flow velocity can be calculated, the flow direction can be determined, and the zero flow velocity can be identified.
[0007] First aspect: A flow measurement method based on the time-difference method of fluorescent tracers The method employs a symmetrically arranged first and second fluorescence detection units, located on opposite sides of the same injection point in the flow channel with equal axial distances, each at a preset fixed distance L. The method comprises the following steps: Step S1: System initialization, signal processing and control unit self-test and set tracer release cycle; Step S2: Release fluorescent tracer, at time T0, inject fluorescent tracer into the flow channel through the injection point; Step S3: Dual-channel synchronous fluorescence monitoring, convert the light signal into a high signal-to-noise ratio electrical signal and transmit it to the signal processor; Step S4: Signal analysis and peak time extraction, the signal processor performs real-time analysis of the two signals, uses the first fluorescence detection unit and the second fluorescence detection unit to synchronously monitor the fluorescence signal in the flow channel, and obtains the following time parameters: the time t1 when the first fluorescence detection unit first detects the fluorescence signal and its fluorescence intensity peak time T1, the time t2 when the second fluorescence detection unit first detects the fluorescence signal and its fluorescence intensity peak time T2; Step S5: State judgment and flow rate calculation, based on the time parameters T0, t1, t2, T1, T2 and the preset fixed distance L, calculate the fluid flow rate and determine the flow direction; Step S6: Based on the flow rate V calculated in step S5, combine with the liquid level data of the pressure liquid level unit to obtain the cross-sectional area A, according to the formula Q = V × A calculates the volumetric flow rate.
[0008] Preferably, step S5, which involves calculating the flow velocity and determining the flow direction, specifically includes: If t1 and t2 are equal within a preset error range of ±5%, and T1 and T2 are equal within a preset error range of ±5%, and the two fluorescence signal curves show a synchronously changing low-concentration Gaussian distribution characteristic, then the fluid velocity is determined to be zero, i.e., V=0. If the first fluorescence detection unit does not detect a fluorescence signal, but the second fluorescence detection unit detects a fluorescence signal at time t2 and detects a significant peak at time T2, then the tracer diffusion rate is insufficient to reach the first fluorescence detection unit against the current. In this case, the diffusion effect is ignored, the water flow direction is determined to be from the first fluorescence detection unit to the second fluorescence detection unit, and the flow velocity is calculated according to the formula V = L / (T2 - T0). Conversely, if the flow direction is not determined to be the same, the flow direction is determined to be opposite, and the flow velocity is calculated according to the formula V = L / (T1 - T0). If the first fluorescence detection unit detects a fluorescence signal at time t1, and the second fluorescence detection unit detects a fluorescence signal at time t2 and detects a significant peak at time T2, then the direction of water flow is determined to be from the first fluorescence detection unit to the second fluorescence detection unit, and the diffusion of the tracer is sufficient to reach the first fluorescence detection unit. This diffusion effect cannot be ignored and needs to be included in the calculation.
[0009] By solving the simultaneous equations: t2 - T0 = L / (V + V 扩散 ) t1 - T0 = L / (V 扩散 - V) Conversely, when the flow is in the opposite direction: t1 - T0 = L / (V + V 扩散 ) t2 - T0 = L / (V 扩散 - V) Solving for the fluid velocity V and the tracer diffusion velocity V0, we obtain the actual fluid velocity V0 and the tracer diffusion velocity V0. 扩散 .
[0010] The second aspect: a flow measurement device based on the fluorescent tracer time-difference method. The method for implementing the above is characterized by comprising: The tracer injection unit includes a tracer reservoir (1) and an injection port (3) connected to a control valve or pump (2) for injecting fluorescent tracer into the flow channel at time T0. U-shaped fluorescence flow detection groove and dual detection unit: The first fluorescence detection unit (4) and the second fluorescence detection unit (5) are symmetrically arranged on both sides of the axial direction of the injection hole (3). The axial distance between the two detection units and the injection hole (3) is a preset fixed distance L, and their optical path axis is perpendicular to the fluid flow direction. Signal processing and control unit (6): electrically connected to the control valve or pump (2), the first fluorescence detection unit (4), the second fluorescence detection unit (5), and the pressure level unit (7), and configured to: control the operation of the tracer injection unit; record the first appearance time t1, t2 and peak time T1, T2 of the fluorescence signal detected by the first fluorescence detection unit (4) and the second fluorescence detection unit (5); calculate the flow velocity V and determine the flow direction based on T0, t1, t2, T1, T2 and distance L; Pressure level unit (7): connected to the signal processing and control unit (6), used to monitor the liquid level and then calculate the cross-sectional area A.
[0011] Preferably, the U-shaped fluorescence flow detection groove provides a rigid mounting reference for the first fluorescence detection unit (4) and the second fluorescence detection unit (5), ensuring that the accuracy of the distance L is not affected by thermal expansion and contraction or mechanical stress. Its structure can constrain the diffusion range of the fluorescent tracer to a certain extent and reduce stray light interference.
[0012] Preferably, both the first fluorescence detection unit (4) and the second fluorescence detection unit (5) include: Excitation light source: used to emit excitation light with a preset wavelength of 400-600nm, specifically LED or laser diode; Photodetector: Used to receive fluorescence signals; photodiode may be a specific option. Optical lens and filter assembly: used to focus the excitation light and filter the fluorescence signal.
[0013] Preferably, the preset fixed distance L is customized to 0.1 m, 0.15 m or 0.2 m according to the microflow rate measurement range.
[0014] Preferably, the signal processing and control unit (6) is further configured to identify the peak value of the fluorescence intensity and determine the peak times T1 and T2 by means of a first derivative zero-crossing detection algorithm or a Gaussian fitting algorithm.
[0015] Preferably, the rigid structure of the U-shaped fluorescent flow detection groove is made of stainless steel or engineering plastic to ensure the long-term stability of the positions of the two detection points.
[0016] Preferably, the signal processing and control unit (6) is further configured to automatically execute the calculation of the formula Q = V × A based on the cross-sectional area A and the calculated flow velocity V, and output the volumetric flow rate data.
[0017] This invention, through its symmetrical detection unit design, can accurately determine the static state of fluids and the direction of water flow. It is applicable to various scenarios such as still water, slow flow, and relatively fast flow, and solves the technical drawbacks such as the inability to detect micro-flow, the difficulty in identifying bidirectional flow, and the misjudgment of zero flow velocity.
[0018] The symmetrical detection unit employed in this invention can determine the static state of fluids and simultaneously identify the direction of water flow. It is capable of measuring fluids in static, slow-flowing, and relatively fast-flowing conditions, thus broadening its application range. To a certain extent, it solves the problems of undetectable microfluidics and bidirectional flow detection, clarifies the determination of static fluid states, and optimizes the technical shortcomings of tracer flow rate detection requirements. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the device structure of the present invention; Figure 2 This is a three-dimensional structural diagram of the water inlet section of the device of the present invention; Figure 3 This is a flowchart of the method of the present invention; Explanation of key component symbols in the diagram: 1. Tracer reservoir; 2. Control pump / valve; 3. Injection port; 4. First fluorescence detection unit; 5. Second fluorescence detection unit; 6. Signal processing and control unit; 7. Pressure and level unit. Detailed Implementation
[0020] The present invention will be further described below with reference to specific embodiments and accompanying drawings.
[0021] Example 1: Device Structure like Figure 1 and 2 As shown, the device of the present invention mainly includes a tracer storage chamber 1, a control pump / valve 2, an injection port 3, a first fluorescence detection unit 4, a second fluorescence detection unit 5, a signal processing and control unit 6, and a pressure and level unit 7.
[0022] The tracer reservoir 1, control pump / valve 2, and injection port 3 together form the tracer release unit. The control pump / valve 2 injects fluorescent tracer droplets at specific times and quantities through the injection port 3 at a specific location within the U-shaped fluorescent flow detection channel, thus injecting fluorescent tracer into the U-shaped channel at regular intervals and in precise quantities. The device employs a U-shaped fluorescent flow detection channel and a dual detection unit design. The first fluorescent detection unit 4 and the second fluorescent detection unit 5 are fixedly installed on both sides of the injection port 3, with the optical path axes of both detection units perpendicular to the fluid flow direction. The axial distance between the two detection units and the tracer injection port 3 is a preset fixed distance L = 0.15m. The first fluorescent detection unit 4 and the second fluorescent detection unit 5 are symmetrically integrated on both sides of the tracer injection point and are equidistant.
[0023] The signal processing and control unit 6 is electrically connected to the control pump / valve 2, the first fluorescence detection unit 4, the second fluorescence detection unit 5, and the pressure / level unit 7. This unit includes: Controller: Sends precise timing trigger signals to control pump / valve 2; Signal processor: used to synchronously acquire, amplify, and filter the electrical signals from the two fluorescence detection units, and intelligently identify the peak value of fluorescence intensity through algorithms (such as first derivative zero-crossing detection or Gaussian fitting), and accurately record the time T0 when the fluorescent tracer is released, the time when each peak appears (T1 and T2), and the time when fluorescence appears (t1 and t2). The calculation and judgment module is used to calculate the flow velocity based on the time differences of T0, T1, T2, t1, and t2, as well as the preset fixed distance L between the detection units. It also determines the flow direction by comparing the times when high concentration peaks appear in T1 and T2. Specifically, this module has a built-in zero-velocity criterion: when neither detection unit's signal shows a sudden, sharp high-concentration peak, t1 and t2 are equal within a preset error range of ±5%, and the two fluorescence signal curves exhibit a synchronously changing low-concentration Gaussian distribution, the fluid velocity is determined to be zero. Finally, the volumetric flow rate is calculated using Q=V×A.
[0024] To better understand the key structure of this measuring device, the three-dimensional structural diagram of the water inlet section, shown in Figure 2, includes: a first fluorescence detection unit 4, a pressure level unit 7, an injection port 3, and a second fluorescence detection unit 5. Each fluorescence detection unit includes an excitation light source, a photodetector (such as a photodiode), and a set of optical lenses and filters for focusing and filtering specific fluorescence wavelengths. The liquid level measured by the pressure level unit 7, combined with the fixed shape of the pipe, is used to calculate the cross-sectional area A of the fluid.
[0025] Example 2: Measurement Method As shown in Figure 3, the flow measurement method based on the fluorescent tracer time difference method of this device has the following steps: Step S1: System Initialization. The signal processing and control unit performs a self-test and sets the tracer release cycle; Step S2: Release Fluorescent Tracer. At time T0, the controller triggers the tracer injection unit to inject a drop of fluorescent tracer into the flow channel, forming a tracer cluster; Step S3: Dual-Channel Synchronous Fluorescence Monitoring. The first fluorescence detection unit (left) and the second fluorescence detection unit (right) start synchronously, continuously monitoring the fluorescence intensity at their respective positions within the U-shaped fluorescence flow detection cell, and converting the optical signal into a high signal-to-noise ratio electrical signal for transmission to the signal processor; Step S4: Signal Analysis and Peak Time Extraction. The signal processor performs real-time analysis of the two signals, using the first fluorescence detection unit (left) and the second fluorescence detection unit (right) to synchronously monitor the fluorescence signal within the U-shaped fluorescence flow detection cell, obtaining the following time parameters: the time t1 when the first fluorescence detection unit first detects the fluorescence signal and its fluorescence intensity peak time T1, and the time t2 when the second fluorescence detection unit first detects the fluorescence signal and its fluorescence intensity peak time T2; Step S5: Status Judgment and Flow Rate Calculation. Based on the time parameters T0, t1, t2, T1, T2 and the preset fixed distance L, the fluid velocity is calculated and the flow direction is determined. The calculation module executes the following logic: S51. If t1 and t2 are equal within a preset error range of ±5%, the tracer signal is detected at both detection points simultaneously. The fluorescence intensity slowly and uniformly diffuses and increases throughout the flow channel. T1 and T2 are equal within a preset error range of ±5%, and the two signal curves are highly consistent, forming a low-concentration Gaussian distribution fluorescence signal. The fluid velocity is determined to be zero (static state), i.e., V=0. S52. If the first fluorescence detection unit (left side) does not detect a fluorescence signal, but the second fluorescence detection unit (right side) detects a fluorescence signal at time t2 and detects a significant peak at time T2, then the tracer diffusion rate is insufficient to reach the first fluorescence detection unit (left side) against the current. In this case, the diffusion effect is defined as negligible, and the water flow direction is determined to be from the first fluorescence detection unit (left side) to the second fluorescence detection unit (right side). The flow velocity is calculated according to the formula V = L / (T2 - T0). Conversely, if the flow direction is opposite, the flow direction is determined to be opposite, and the flow velocity is calculated according to the formula V = L / (T1 - T0). S53. If the first fluorescence detection unit (left side) detects a fluorescence signal at time t1, and the second fluorescence detection unit (right side) detects a fluorescence signal at time t2 and detects a significant peak at time T2, then the direction of water flow is determined to be from the first fluorescence detection unit (left side) to the second fluorescence detection unit (right side), and the diffusion of the tracer is sufficient to reach the first fluorescence detection unit (left side). This diffusion effect cannot be ignored and must be included in the calculation.
[0026] By solving the simultaneous equations: t2 - T0 = L / (V + V 扩散 ) t1 - T0 = L / (V 扩散 - V) Conversely, when the flow is in the opposite direction: t1 - T0 = L / (V + V 扩散 ) t2 - T0 = L / (V 扩散 - V) Solving for the fluid velocity V and the tracer diffusion velocity V0, we obtain the actual fluid velocity V0 and the tracer diffusion velocity V0. 扩散 .
[0027] Step S6: Flow rate output. The cross-sectional area A is obtained by combining the liquid level data from the pressure level unit 7, and the volumetric flow rate is calculated using the formula Q=V×A.
[0028] In this embodiment, the U-shaped fluorescence flow detection groove provides a precise and fixed installation reference for the detection units on both sides, ensuring that the accuracy of the preset fixed distance L is not affected by thermal expansion and contraction or mechanical stress. At the same time, the U-shaped fluorescence flow detection groove forms an optical window, constraining the propagation of excitation light and emission fluorescence within the groove, effectively reducing stray light interference, and achieving a high signal-to-noise ratio of 45dB in the dark environment of the well casing.
[0029] Each fluorescence detection unit includes an excitation source, a photodetector (photodiode), and an optical lens and filter array for focusing and filtering specific fluorescence wavelengths. This configuration ensures the sensitivity and specificity of fluorescence detection.
[0030] Example 3, tracer injection unit: This unit consists of a 5L tracer reservoir 1, a control pump 2, and an injection port 3. This unit is responsible for injecting fluorescent tracer into the flow channel in a timed and quantitative manner.
[0031] U-shaped fluorescence flow detection channel and dual detection units: This is the core structure of the invention. The two vertical sidewalls of the channel serve as optical windows. A first fluorescence detection unit 4 and a second fluorescence detection unit 5 are symmetrically integrated at both ends of the U-shaped channel. These two detection units are fixedly mounted on both sides of the injection port 3, and their sole function is to detect the fluorescence intensity signal within the flow channel. The optical paths of these two units are precisely calibrated, perpendicular to the fluid flow direction, and their optical focal points are strictly equal to the axial distance of the tracer injection port 3, which is set to L = 0.15m in this embodiment.
[0032] Signal processing and control unit 6: This unit is electrically connected to the micro-control pump 2 and the two fluorescence detection units 4 and 5. Its functions include: Controller: Sends a precise timing trigger signal (defined as T0) to the tracer injection unit.
[0033] Signal processor: Synchronously acquires, amplifies, and filters electrical signals from the two PMTs. It intelligently identifies the peak values of fluorescence intensity using an algorithm (the first derivative zero-crossing detection algorithm or Gaussian fitting algorithm as described in claim 8) and accurately records the times T1 and T2 of each peak, as well as the times t1 and t2 when the fluorescence signal appears.
[0034] Calculation and Judgment Module: This is the core of the method. Based on T0, t1, t2, T1, T2, and a fixed distance L, it executes the logic in the following method to calculate the flow velocity V and determine the flow direction. Pressure and Level Unit 7: This unit is used for level monitoring, thereby obtaining the cross-sectional area A (e.g., if the equipment is placed in a rectangular water channel with a width of 0.4m and the measured level is 0.5m, then the cross-sectional area A = 0.2m). 2 ).
[0035] The method flowchart corresponding to this embodiment is as follows: Figure 3 As shown in the flowchart, each step is described in detail below: Step S1: System initialization, power-on self-test of the signal processing and control unit, and setting of the tracer release cycle (e.g., once every 5 minutes).
[0036] Step S2: Release the fluorescent tracer. At the set time T0 (e.g., 12:00:00.000), the controller triggers the control pump to inject a 1 mL fluorescent tracer droplet into the flow channel through the injection port, forming an initial tracer cluster.
[0037] Step S3: Dual-channel synchronous fluorescence monitoring. At the moment of injection, the first fluorescence detection unit (left side) and the second fluorescence detection unit (right side) start synchronously. They convert the received light signal into an electrical signal, which is then amplified, filtered, and transmitted to the signal processor.
[0038] Step S4: Signal analysis and peak time extraction. The signal processor performs real-time analysis on the two signals. A Gaussian fitting algorithm is used to intelligently identify the peak value of the fluorescence intensity. This algorithm has better robustness to common noise and baseline drift in microfluidics and can accurately determine T1 and T2.
[0039] Step S5: Status determination and flow rate calculation. The calculation module executes the following logic: Scenario S51: In a measurement, if the system finds that t1 and t2 are approximately equal within the instrument error range (e.g., difference < 10 ms), and T1 and T2 are also approximately equal, and the two fluorescence signal curves are highly consistent, both showing a low-concentration, broad-peak Gaussian distribution shape without any high-concentration sharp peaks, then the system determines that the fluid velocity is zero (static state), i.e., V = 0.
[0040] Scenario S52: If the first fluorescence detection unit (left side) does not detect a fluorescence signal (signal does not exceed the noise threshold), while the second fluorescence detection unit (right side) has a clear fluorescence signal at time t2 and a significant peak appears at time T2, then the water flow direction is determined to be from left to right, and the tracer diffusion rate is insufficient to reach the upstream unit against the current. In this case, ignoring the diffusion effect, the flow velocity V = L / (T2 - T0) = 0.15m / (10s) = 0.015m / s.
[0041] Scenario S53: As shown in the measurement data of this example, both units detected signals and peaks. The system determines the flow direction to be from the side with the later peak appearance time to the side with the earlier peak appearance time (taking the direction from the first fluorescence detection unit to the second fluorescence detection unit as an example). Due to the significant diffusion effect of the tracer clusters, the diffusion effect must be considered. System simultaneous equations: t2 - T0 = L / (V + V 扩散 =>30 = 0.15 / (V + V) 扩散 ) t1 - T0 = L / (V 扩散 - V) =>50 = 0.15 / (V 扩散 - V) Solving this system of equations yields the actual flow velocity V = 0.00025 m / s and the diffusion velocity V0. 扩散 = 0.001m / s.
[0042] Step S6: Flow rate output. Using the cross-sectional area of the flow channel A = 0.4m × 0.5m = 0.4 m², calculate the volumetric flow rate according to the formula Q = V × A. For the result of scenario S53, Q = 0.00025m / s × 0.4 m² = 0.0001m³ / s.
[0043] This embodiment fully validates the measurement of fluid velocity / volume and flow direction in fields such as online environmental monitoring (e.g., groundwater infiltration, slow-flow channels) through a specific, demanding application scenario, and uniquely identifies zero-velocity (static) states. It specifically demonstrates the applicable conditions and calculation methods for different velocity calculation logics. It proves that these structural features (such as the stability and optical constraint of the U-shaped channel, the arrangement of symmetrical detection units, and the selection of specific optical components) are necessary and effective for achieving high-precision time-of-flight methods in micro / slow-flow conditions. This embodiment successfully solves the problem of flow monitoring in micro-flow environments. Its bidirectional flow detection capability enables the analysis of complex microfluidic scenarios, while its superior zero-velocity identification capability eliminates misjudgments.
[0044] The above description is only a specific embodiment of the present invention, but the structural and method features of the present invention are not limited thereto. The present invention can be used on similar products, and any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.
Claims
1. A flow measurement method based on the time-of-flight fluorescence tracer method, comprising a symmetrically arranged first fluorescence detection unit and a second fluorescence detection unit, wherein the two detection units are located on opposite sides of the same injection point in the flow channel and are equidistant from each other by an axial distance of L, characterized in that, The method includes the following steps: Step S1: System initialization, signal processing and control unit self-test and set fluorescent tracer release cycle; Step S2: Release fluorescent tracer. At time T0, inject fluorescent tracer into the flow channel through the injection point. Step S3: Dual-channel synchronous fluorescence monitoring converts the optical signal into a high signal-to-noise ratio electrical signal and transmits it to the signal processor; Step S4: Signal analysis and peak time extraction. The signal processor performs real-time analysis on the two signals. The first fluorescence detection unit and the second fluorescence detection unit are used to synchronously monitor the fluorescence signal in the U-shaped groove and obtain the following time parameters: the time t1 when the first fluorescence detection unit first detects the fluorescence signal and its fluorescence intensity peak time T1, and the time t2 when the second fluorescence detection unit first detects the fluorescence signal and its fluorescence intensity peak time T2. Step S5: State judgment and flow velocity calculation. Based on the time parameters T0, t1, t2, T1, T2 and a fixed distance L, calculate the flow velocity V of the fluid and determine the flow direction. Step S6: Based on the flow velocity V calculated in step S5, and combined with the liquid level data of the pressure liquid level unit, the cross-sectional area A is obtained, and the volumetric flow rate is calculated according to the formula Q = V × A.
2. The method according to claim 1, characterized in that, Step S5, which involves calculating the flow velocity and determining the flow direction, specifically includes: If t1 and t2 are equal, and T1 and T2 are equal, and the two fluorescence signal curves show a synchronously changing low-concentration Gaussian distribution characteristic, then the fluid velocity is determined to be zero, i.e., V=0. If the first fluorescence detection unit does not detect a fluorescence signal, but the second fluorescence detection unit detects a fluorescence signal at time t2 and detects a peak at time T2, then the tracer diffusion rate is insufficient to reach the first fluorescence detection unit against the current. In this case, the water flow direction is determined to be from the first fluorescence detection unit to the second fluorescence detection unit, and the flow velocity is calculated according to the formula V = L / (T2 - T0). Conversely, if the flow direction is not equal, the flow direction is determined to be opposite, and the flow velocity is calculated according to the formula V = L / (T1 - T0). If the first fluorescence detection unit detects a fluorescence signal at time t1, and the second fluorescence detection unit detects a fluorescence signal at time t2 and detects a peak at time t2, then it is determined that the water flow direction is from the first fluorescence detection unit to the second fluorescence detection unit, and the tracer diffusion is sufficient to reach the first fluorescence detection unit. By solving the simultaneous equations: t2 - T0 = L / (V + V 扩散 ) t1 - T0 = L / (V 扩散 - V) Conversely, when the flow is in the opposite direction: t1 - T0 = L / (V + V 扩散 ) t2 - T0 = L / (V 扩散 - V) Solving for the fluid velocity V and the tracer diffusion velocity V0, we obtain the actual fluid velocity V0 and the tracer diffusion velocity V0. 扩散 .
3. A flow measurement device based on the fluorescent tracer time-difference method for implementing the method of claim 1 or 2, characterized in that, include: The tracer injection unit includes a tracer reservoir (1) and an injection port (3) connected to a control pump / valve (2) for injecting fluorescent tracer into the flow channel at time T0; The U-shaped fluorescence flow detection groove and the dual detection unit are arranged symmetrically on both sides of the injection hole (3) with a first fluorescence detection unit (4) and a second fluorescence detection unit (5). The axial distance between the two detection units and the injection hole (3) is L, and their optical path axis is perpendicular to the fluid flow direction. The signal processing and control unit (6) is electrically connected to the control pump / valve (2), the first fluorescence detection unit (4), the second fluorescence detection unit (5), and the pressure level unit (7), and is configured to: control the operation of the fluorescent tracer injection unit; Record the first appearance time t1, t2 and peak time T1, T2 of the fluorescence signal detected by the first fluorescence detection unit (4) and the second fluorescence detection unit (5); Based on T0, t1, t2, T1, T2 and distance L, calculate the flow velocity V and determine the flow direction; The pressure level unit (7) is connected to the signal processing and control unit (6) to monitor the liquid level and then calculate the cross-sectional area A.
4. The apparatus according to claim 3, characterized in that, The U-shaped fluorescence flow detection groove provides a rigid mounting reference for the first fluorescence detection unit (4) and the second fluorescence detection unit (5), ensuring that the accuracy of the distance L is not affected by thermal expansion and contraction or mechanical stress.
5. The apparatus according to claim 3, characterized in that, Both the first fluorescence detection unit (4) and the second fluorescence detection unit (5) include: An excitation light source is used to emit excitation light of a preset wavelength; A photodetector is used to receive fluorescence signals; An optical lens and filter assembly are used to focus the excitation light and filter the fluorescence signal.
6. The apparatus according to claim 5, characterized in that: The excitation source is an LED or laser diode with a preset wavelength, and the photodetector is a photodiode.
7. The apparatus according to claim 4, characterized in that, The distance L is customized to 0.1 m, 0.15 m or 0.2 m according to the microflow rate measurement range.
8. The apparatus according to claim 3, characterized in that, The signal processing and control unit (6) is further configured to identify the peak value of the fluorescence intensity and determine the peak times T1 and T2 by means of a first derivative zero-crossing detection algorithm or a Gaussian fitting algorithm.
9. The apparatus according to claim 3, characterized in that, The rigid structure of the U-shaped fluorescence flow detection groove is made of stainless steel or engineering plastic to ensure the long-term stability of the positions of the two detection points.
10. The apparatus according to claim 3, characterized in that, The signal processing and control unit (6) is also configured to automatically execute the calculation of the formula Q = V × A based on the cross-sectional area A and the calculated flow velocity V, and output the volumetric flow rate data.