CN-122015980-A - Flow measurement device and method based on fluorescent tracer time difference method

CN122015980ACN 122015980 ACN122015980 ACN 122015980ACN-122015980-A

Abstract

A flow measurement device and method based on a fluorescent tracer time difference method relates to the technical field of flow measurement with flow velocity based on the fluorescent tracer time difference method, and comprises a tracer injection unit, a U-shaped fluorescent flow detection groove, a double detection unit, a first fluorescent detection unit, a second fluorescent detection unit, a signal processing and controlling unit and a pressure liquid level unit, wherein the tracer injection unit comprises a tracer liquid storage cavity, a control pump/valve and an injection hole. The first fluorescence detection unit and the second fluorescence detection unit are positioned on two sides of the axial distance of the injection hole, and the distance is L. According to the tracer release time T0, the fluorescence signal occurrence time T1 and T2, the high concentration peak time T1 and T2, the fluorescence signal curve, the water flow direction is judged, the flow speed is calculated, and meanwhile, the flow is measured according to the liquid level data of the pressure liquid level unit.

Inventors

JIN LI
JIN JIAN
ZHU JIAHUA
CHENG JIE
ZHAO RAN
XIONG DONGDONG
SONG JIANFENG

Assignees

浙江小桥流水环境科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260306

Claims (10)

1. The flow measuring method based on the fluorescent tracer time difference method adopts a first fluorescent detection unit and a second fluorescent detection unit which are symmetrically arranged, wherein the two detection units are positioned at two sides of the same injection point in a flow channel, the axial distances are equal, and the two detection units are L, and the flow measuring method is characterized by comprising the following steps: S1, initializing a system, self-checking a signal processing and control unit and setting a fluorescent tracer release period; S2, releasing a fluorescent tracer, and injecting the fluorescent tracer into the flow channel through the injection point at the time T0; S3, double-channel synchronous fluorescence monitoring, namely converting an optical signal into an electric signal with high signal-to-noise ratio and transmitting the electric signal to a signal processor; The method comprises the steps of S4, signal analysis and peak time extraction, wherein a signal processor carries out real-time analysis on two paths of signals, and the first fluorescent detection unit and the second fluorescent detection unit are utilized to synchronously monitor fluorescent signals in a U-shaped groove and acquire the following time parameters, namely, the time T1 when the first fluorescent detection unit detects the fluorescent signals for the first time and the peak time T1 of the fluorescent intensity thereof, the time T2 when the second fluorescent detection unit detects the fluorescent signals for the first time and the peak time T2 of the fluorescent intensity thereof; step S5, state judgment and flow rate calculation, namely calculating the flow rate V of the fluid and judging the flow direction based on the time parameters T0, T1, T2, T1 and T2 and the fixed distance L; Step S6, based on the flow velocity V calculated in step S5, the cross-sectional area a is obtained by combining the liquid level data of the pressure liquid level unit, and the volume flow is calculated according to the formula q=v×a.
2. The method according to claim 1, wherein calculating the flow rate and determining the flow direction in step S5 specifically comprises: If T1 is equal to T2, and the two fluorescence signal curves show low-concentration gaussian distribution characteristics which change synchronously, determining that the fluid flow velocity is zero, namely v=0; If the first fluorescent detection unit does not detect the fluorescent signal, the second fluorescent detection unit detects that the fluorescent signal exists at the time T2 and the peak appears at the time T2, the tracer diffusion speed is insufficient to reach the first fluorescent detection unit in a countercurrent manner, the water flow direction is judged to be the direction from the first fluorescent detection unit to the second fluorescent detection unit, and the flow rate is calculated according to the formula V=L/(T2-T0), otherwise, the flow direction is judged to be opposite, and the flow rate is calculated according to the formula V=L/(T1-T0); if the first fluorescent detection unit detects that the fluorescent signal exists at the time T1, the second fluorescent detection unit detects the fluorescent signal at the time T2 and the peak appears at the time T2, the water flow direction is judged to be the direction from the first fluorescent detection unit to the second fluorescent detection unit, and the peripheral diffusion of the tracer is enough to reach the first fluorescent detection unit; by simultaneous equations: t2 - T0 = L / (V + V Diffusion of ) t1 - T0 = L / (V Diffusion of - V) conversely, when the flow direction is opposite: t1 - T0 = L / (V + V Diffusion of ) t2 - T0 = L / (V Diffusion of - V) solving to obtain the actual flow velocity V of the fluid and the diffusion velocity V Diffusion of of the tracer.
3. A flow measurement device based on the fluorescent tracer time difference method for implementing the method of claim 1 or 2, comprising: A tracer injection unit comprising a tracer reservoir (1), an injection hole (3) in communication with the control pump/valve (2) for injecting a fluorescent tracer into the flow channel at a time T0; The U-shaped fluorescent flow detection groove and the double detection units are symmetrically arranged on two sides of the axial direction of the injection hole (3) in the U-shaped fluorescent flow detection groove and the double detection units, the axial distance between the two detection units and the injection hole (3) is L, and the optical path axis of the U-shaped fluorescent flow detection groove is perpendicular to the flow direction of fluid; The signal processing and control unit (6) is electrically connected with the control pump/valve (2), the first fluorescence detection unit (4), the second fluorescence detection unit (5) and the pressure liquid level unit (7) and is configured to control the action of the fluorescent tracer injection unit; recording appear for the first time times T1 and T2 and peak times T1 and T2 when the first fluorescence detection unit (4) and the second fluorescence detection unit (5) detect fluorescence signals; calculating a flow velocity V and judging a flow direction based on T0, T1, T2, T1, T2 and a distance L; And the pressure liquid level unit (7) is connected with the signal processing and control unit (6) and is used for monitoring the liquid level and further calculating the cross-sectional area A.
4. A device according to claim 3, characterized in that the U-shaped fluorescent flow-through detection groove provides a rigid mounting reference for the first (4) and second (5) fluorescent detection units, ensuring that the accuracy of the distance L is not affected by thermal expansion and contraction or mechanical stress.
5. A device according to claim 3, characterized in that the first fluorescence detection unit (4) and the second fluorescence detection unit (5) each comprise: The excitation light source is used for emitting excitation light with preset wavelength; The photoelectric detector is used for receiving the fluorescent signal; And the optical lens and the optical filter set are used for focusing the excitation light and filtering the fluorescence signal.
6. The apparatus of claim 5, wherein the excitation light source is an LED or a laser diode of a predetermined wavelength and the photodetector is a photodiode.
7. The device of claim 4, wherein the distance L is tailored to be 0.1 meter, 0.15 meter, or 0.2 meter depending on the micro-flow measurement range.
8. A device 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 to determine peak times T1 and T2 by means of a first derivative zero crossing detection algorithm or a gaussian fitting algorithm.
9. A device according to claim 3, wherein the rigid structure of the U-shaped fluorescent flow-through detection cell is made of stainless steel or engineering plastic to ensure long term stability of the two detection spot positions.
10. A device according to claim 3, characterized in that the signal processing and control unit (6) is further configured to automatically perform the calculation of the formula Q = V x a based on the cross-sectional area a and the calculated flow velocity V and to output volumetric flow data.

Description

Flow measurement device and method based on fluorescent tracer time difference method Technical Field The invention relates to the technical field of fluid measurement, in particular to a flow measurement device and method based on a fluorescent tracer time difference method and a low fluorescent tracer time difference method. The device and the method are suitable for measuring the flow velocity and the flow direction of the fluid in the fields of environment on-line monitoring (such as groundwater infiltration monitoring) and the like, and can uniquely identify the state of zero flow velocity (static state). Specifically, the invention realizes accurate discrimination and measurement of micro-flow, bidirectional flow and static fluid by the collaborative design of the symmetrically arranged double fluorescent detection units and the U-shaped detection groove and by combining the injection of the fluorescent tracer and accurate time difference detection, and solves the problem of limitation of the traditional flow measurement technology based on the fluorescent tracer time difference method under the condition of low flow velocity. Background Flow measurement based on fluorescent tracer time difference method has wide application in the fields of hydraulic engineering, environmental monitoring, industrial production and the like. The traditional flow measuring instrument (such as a Pitot tube and a turbine flowmeter) based on the fluorescent tracer time difference method is based on the fluid dynamic pressure or mechanical motion principle, and has the problems of measurement failure caused by insufficient signal response under the condition of low flow rate/micro flow rate, complex structure and high cost of high-precision optical equipment such as a laser Doppler flow rate meter (LDA) and the like, difficulty in adapting to field environment, easiness in interference of bubbles and temperature change under the micro flow rate, difficulty in capturing time difference, waveform distortion and the like. Flow measurement (such as groundwater infiltration and slope thin-layer water flow) based on a fluorescent tracer time difference method has extremely high requirements on equipment sensitivity and bidirectional flow detection capability, but the existing flowmeter is limited by minimum detection and is difficult to meet the requirements. Although the fluorescence detection method is introduced into the field due to high sensitivity, the prior proposal has obvious defects that single-point/asymmetric detection cannot judge the flow direction and the zero flow speed state, the diffusion signal of the tracer in static fluid is easy to be misjudged as low flow speed, part of the system depends on a mechanical structure, the difficult problem of flow measurement based on the time difference method of the fluorescent tracer is not really solved, and the anti-interference capability and the environmental adaptability are not enough. Aiming at the defects of the prior art, a flow measurement scheme based on a fluorescent tracer time difference method, which has high sensitivity, low cost and strong environmental adaptability and can realize bidirectional flow detection and zero flow rate identification, is urgently needed in the field. Disclosure of Invention The invention provides a flow measuring device and a flow measuring method based on a fluorescent tracer time difference method, which are characterized in that integrated design of symmetrically arranged double fluorescent detection units and U-shaped detection grooves is adopted, and the flow velocity calculation, the flow direction judgment and the zero flow velocity identification are realized by accurately recording the characteristic parameters of the fluorescent signals. The invention provides a flow measuring device and a flow measuring method based on a fluorescent tracer time difference method, which are characterized in that integrated design of symmetrically arranged double fluorescent detection units and U-shaped detection grooves is adopted, and the flow velocity calculation, the flow direction judgment and the zero flow velocity identification are realized by accurately recording the characteristic parameters of the fluorescent signals. In a first aspect, a flow measurement method based on a fluorescent tracer time difference method The first fluorescent detection unit and the second fluorescent detection unit which are symmetrically arranged are adopted, the two detection units are positioned at two sides of the same injection point in the flow channel and have equal axial distance, all are preset fixed distances L, and the method is characterized by comprising the following steps: The method comprises the steps of S1, initializing a system, self-checking a signal processing and control unit, setting a tracer release period, S2, releasing a fluorescent tracer, injecting the fluorescent tracer into a flow channel through an injection point at th