CN-121994658-A - Holographic imaging-Raman spectrum coupling water sediment multi-parameter online measurement method and device

CN121994658ACN 121994658 ACN121994658 ACN 121994658ACN-121994658-A

Abstract

The invention discloses a holographic imaging-Raman spectrum coupling water sediment multi-parameter on-line measurement method, which comprises the steps of using parallel monochromatic laser to irradiate a sediment suspension water sample in holographic measurement, recording an interference fringe pattern formed by interaction of light and suspended sediment particles by using a holographic camera, obtaining morphology, particle size and concentration of the sediment particles through holographic reconstruction, parameter extraction and analysis, using parallel high-coherence laser with different wavebands to focus the sediment suspension water sample in Raman measurement, recording a Raman spectrum formed by Raman scattering of the light and the particles by using a Raman spectrometer, and comparing to obtain the composition of the sediment particles. The invention also discloses an online measurement device corresponding to the method. The method and the device provided by the invention can realize multi-parameter synchronous on-line measurement of suspended sediment of the flowing water body, and effectively solve the problems of easy influence on the result, complex system, high cost, incomplete measurement parameters and the like of the existing measurement method.

Inventors

WU XUECHENG
Lu Rou
ZHU DIAN
LIN ZHIMING
JIN QIWEN
WU YINGCHUN
YAO LONGCHAO
ZHENG CHENGHANG
GAO XIANG
LI CHENGHAO
DONG JIAYAO

Assignees

浙江大学

Dates

Publication Date: 20260508
Application Date: 20241104

Claims (10)

1. The holographic imaging-Raman spectrum coupling water sediment multi-parameter online measurement method is characterized by comprising the following steps of: (1) Sampling at constant speed at the axial depth of the pressure pipeline, and introducing the obtained sediment suspension into a measuring channel; (2) The method comprises the steps that monochromatic laser beams generated by a holographic laser are modulated to form parallel beams, the beams are divided into object light and reference light through a spectroscope, the object light irradiates suspended sediment particles in sediment suspension in a measuring flow channel, holographic images of the sediment particles are formed by interference between the object light and the reference light on a target surface of the holographic camera, and the holographic images are recorded by the holographic camera; (3) The high coherence laser beam generated by the Raman laser is modulated to form a parallel beam, the beam is focused on suspended sediment particles through a microscope objective after being reflected by a dichroic mirror, part of the beam is inelastically scattered to form Raman scattered light and penetrates through the dichroic mirror, and a Raman spectrum is recorded by a Raman spectrometer; (4) Reconstructing a holographic image by utilizing a holographic reconstruction algorithm, and extracting and analyzing parameters of sediment particles in a reconstruction result, wherein the parameters comprise particle size, concentration and morphology; (5) Comparing the Raman spectrum with a known substance spectrum database, and analyzing to obtain the chemical composition of suspended sediment particles; Wherein, the wave band of the monochromatic laser beam generated by the holographic laser is different from the wave band of the high coherence laser beam generated by the Raman laser.
2. The method for online measurement of sediment in water body through holographic imaging-Raman spectrum coupling according to claim 1 is characterized in that in the step (2), when an off-axis holographic light path structure is adopted for measurement, monochromatic laser beams generated by a holographic laser device are filtered, expanded and collimated to form parallel beams, the parallel beams are divided into two beams through a spectroscope, one beam is used as object light to irradiate suspended sediment particles in a measuring flow channel and interact with the suspended sediment particles, the other beam is used as reference light to interfere with the object light passing through the measuring flow channel and form a holographic image of sediment particle field on a camera target surface, when the coaxial holographic light path structure is adopted for measurement, an original reference light path is blocked, the parallel beams which are used as object light irradiate suspended sediment particles in the measuring flow channel, part of the beams interact with the particles to form object light, and the rest of the beams directly pass through the measuring flow channel to form reference light, and interfere with the two beams and form the holographic image of sediment particle field on the camera target surface.
3. The holographic imaging-Raman spectrum coupling water sediment multi-parameter online measurement method according to claim 1 is characterized in that in the step (3), laser beams generated by a Raman laser are filtered, expanded and collimated to form parallel beams, the parallel beams are reflected by a dichroic mirror and focused on suspended sediment particles in a measurement flow channel through a first microscope objective, a small part of the beams are subjected to Raman scattering, and Raman scattered light is collimated into parallel beams through the microscope objective and then transmitted through the dichroic mirror, and the parallel beams are recorded by a spectrometer after being reflected and focused.
4. The holographic imaging-Raman spectrum coupling water sediment multiple parameter online measurement method is characterized in that in the step (4), a wavelet algorithm, a Fresnel algorithm, a convolution reconstruction or an angular spectrum reconstruction algorithm is adopted in the holographic reconstruction algorithm, sediment particles in a reconstruction result are subjected to parameter extraction and analysis, particle contour and morphology characteristic information are extracted from a reconstruction graph through a self-adaptive threshold algorithm, optical intensity information is analyzed and calculated to obtain three-dimensional space position information of the particles, images are binarized after the sediment particles are identified, particle sizes of the sediment particles are calculated according to particle pixel areas and camera target sizes and calibration results, the mass of all the sediment particles in a measurement field is accumulated, the volume of the holographic measurement field is combined, and finally concentration parameters of the sediment particles are obtained.
5. The holographic imaging-Raman spectrum coupling water sediment multi-parameter online measurement method according to claim 1 is characterized in that in the step (5), the specific method comprises the steps of preprocessing Raman spectrum, including background correction, noise filtration and baseline correction, detecting the peak position and intensity of the preprocessed Raman spectrum, separating overlapped Raman peaks to obtain Raman peaks corresponding to single components, comparing the positions of the Raman peaks with a known substance spectrum database after frequency correction, identifying the components of sediment particles, and quantitatively analyzing the proportion of the sediment particles.
6. A holographic imaging-raman spectrum coupled water sediment multiparameter on-line measuring device employing the method of any one of claims 1-5, said device comprising: The constant-speed sampling system is used for sampling at constant speed at the axial depth of the pressure pipeline and introducing the obtained sediment suspension into the measuring channel; The holographic measurement system is used for modulating monochromatic laser beams generated by the holographic laser to form parallel beams, the beams are divided into object light and reference light by the spectroscope, the object light irradiates suspended sediment particles in sediment suspension in the measurement flow channel, holographic images of the sediment particles are formed by interference between the object light and the reference light on the target surface of the holographic camera, and the holographic images are recorded by the holographic camera; The Raman measurement system is used for modulating high-coherence laser beams generated by the Raman laser to form parallel beams, reflecting the parallel beams by the dichroic mirror, focusing the parallel beams on suspended sediment particles by the micro objective lens, and recording Raman spectra by the Raman spectrometer after part of the light forms Raman scattered light through inelastic scattering and penetrates through the dichroic mirror; The data processing system comprises a holographic data processing system and a Raman spectrum processing system, wherein the holographic data processing system utilizes a holographic reconstruction algorithm to reconstruct a holographic image, and performs parameter extraction and analysis on sediment particles in a reconstruction result, wherein the parameters comprise particle size, concentration and morphology characteristics, and the Raman spectrum processing system compares a Raman spectrum with a known substance spectrum database and analyzes to obtain the chemical composition of suspended sediment particles.
7. The holographic imaging-Raman spectrum coupling water sediment multi-parameter online measurement device is characterized in that the constant-speed sampling system comprises a sampling head, a sampling tube, a static pressure hole, a static pressure tube, a differential pressure meter, a PID controller and a variable-frequency sampling pump, wherein the sampling head is used for sampling at the central axis height of a pressure pipeline, the arrangement direction is the direction facing the incoming flow, the surface of the sampling head is designed to be a conical surface, the variable-frequency sampling pump is used for taking water from the pressure pipeline through the sampling head and the sampling tube, the static pressure holes inside and outside the sampling tube can respectively measure the static pressure inside and outside the sampling tube and conduct the static pressure to the differential pressure meter through the static pressure tube, and the PID controller is used for analyzing the electric signals transmitted by the differential pressure meter and adjusting the water taking speed of the variable-frequency sampling pump so that the electric signals are consistent with the flow velocity inside the pressure steel tube and realizing constant-speed sampling.
8. The holographic imaging-Raman spectrum coupled water sediment multi-parameter on-line measuring device is characterized in that an optical path structure of the holographic measuring system is that when an off-axis holographic optical path structure is used for measuring, laser emitted by a holographic laser is formed into parallel light through a first spatial filter and a first collimating lens, the parallel light is divided into two orthogonal parallel light through a first beam splitting cube, one light is reflected by a first reflecting mirror along an original direction and irradiates suspended sediment particles in a measuring flow channel to generate scattering, the suspended sediment particles are modulated through a first microscopic objective lens to serve as object light, the other light is reflected by a second reflecting mirror along an orthogonal direction, the second microscopic objective lens is modulated to serve as reference light and is combined with the object light at a second beam splitting cube, interference is generated between the reference light and the reference light, a particle field holographic image formed by interference fringes is formed on a target surface of the holographic camera after the holographic laser is filtered through a band-pass filter, the parallel light formed by modulating the reference light passes through the first beam splitting cube, the first beam splitting cube is reflected by the first reflecting mirror and irradiates suspended sediment particles in the measuring flow channel to generate scattering, and the suspended sediment particles are formed into interference fringes directly through the two holographic filter particles on the target flow channel after the interference fringes are formed by the two holographic filter particles.
9. The holographic imaging-Raman spectrum coupling water sediment multi-parameter on-line measuring device according to claim 6, wherein the Raman measuring system has an optical path structure that when in measurement, laser emitted by the Raman laser forms parallel light through the second spatial filter and the second collimating lens, a part of the light is reflected by the dichroic mirror, the first microscopic objective lens focuses and raman scatters with suspended sediment particles in the measuring flow channel, the part of scattered light is collimated into parallel light through the first microscopic objective lens, passes through the dichroic mirror after passing through the notch filter, and is recorded by the Raman spectrometer after being reflected by the third reflecting mirror and focused by the focusing lens.
10. The holographic imaging-Raman spectrum coupling water sediment multi-parameter online measurement device is characterized in that a linear polarized point light source is adopted by a holographic laser, the wavelength is 532nm, the power is 50 mW-5W, the holographic camera is an area array camera, the pixel target surface is 1M-16M, the minimum exposure time is 1 mu s-10 mu s, the sampling frequency is higher than 1Hz, the linear polarized point light source is adopted by a Raman laser, the wavelength is 785nm, the power is 50 mW-5W, the Raman spectrum measurement range is 100cm -1 -3200cm -1 , and the spectrum resolution is smaller than 1cm -1 .

Description

Holographic imaging-Raman spectrum coupling water sediment multi-parameter online measurement method and device Technical Field The invention belongs to the field of multiphase flow measurement, and particularly relates to a holographic imaging-Raman spectrum coupling water sediment multi-parameter on-line measurement method and device. Background The water energy is used as renewable energy with the most huge scale, and the reduction of greenhouse gas emission is of great significance, so that the stability and reliability of the operation of the core power generation equipment are also important points of the industry. At present, the construction of hydropower stations in China is mainly oriented to western high-altitude areas, rivers in the areas have the characteristics of high water head, high capacity, high sand content and the like, and suspended sediment particles moving at high speed in the rivers can erode and destroy the upstream face of a hydroelectric generating set, so that the operation safety and the power generation efficiency of the hydropower stations are seriously affected. Research shows that the particle size, hardness and morphology of suspended sediment particles can directly influence the abrasion degree of equipment, so that real-time measurement and analysis of various parameters of the suspended sediment particles are realized, and the method has important significance in reducing the operation and maintenance cost of the equipment, proving the operation stability of a unit, improving the generating efficiency of the unit and prolonging the service life of the unit. The traditional sediment measurement method mainly comprises an off-line measurement method, such as a drying method, a filtering method, a replacement method and the like, and can ensure high-precision and high-range measurement results, but has complex operation and poor timeliness, and cannot meet the measurement requirement of hydropower station environment for quick response. To overcome the deficiencies of the conventional methods, optical and acoustic based on-line particle measurement techniques have evolved. The method mainly comprises the steps of measuring the sand content or particle size of particles based on the principle that light beams act on the surfaces of silt particles to generate refraction, diffraction or absorption, and can be divided into a laser diffraction-based instrument and an infrared light back scattering-based instrument according to different specific measuring principles, for example, a China patent with publication number of CN115112536A discloses a method for quickly measuring the sand content of suspended substances, a corresponding relation between turbidity and the sand content is established through experiments, the turbidity of a water body to be measured is measured through a turbidity meter, so that the sand content is quickly obtained, and the acoustic method is widely applied to monitoring of suspended substances due to the unique in-situ measuring advantages of the acoustic method, and is similar to optical technology in working principle, and the difference is that the acoustic method is used for determining the concentration of the suspended substances by analyzing reflected signals of the emitted acoustic waves, for example, the China patent with publication number of CN219179300U discloses a suspended substance sand content measuring device based on an acoustic detection module, and the suspended substance sand content measuring device is small in operation labor intensity and high in detection efficiency through the arrangement of an ultrasonic probe and a silt measuring unit. In addition, devices that are more sophisticated based on acoustic technology development include acoustic backscatter sensors and acoustic doppler flowmeters. However, although some mature particle measurement technologies and methods exist at present, aiming at the measurement requirements of suspended sediment of the hydropower station flowing water, no related technology capable of simultaneously completing multi-parameter online measurement of particle size, concentration, components and the like of suspended sediment particles exists at present, for example, the Chinese patent with publication number CN219104651U realizes synchronous measurement of sediment particle-level distribution and sediment content by utilizing a laser diffraction principle, but cannot realize identification and distinguishing of components, in addition, the existing online measurement methods of parameters such as sediment content, particle size distribution and the like are easy to be influenced by the shape, type, concentration of the suspended sediment particles, and challenge the measurement accuracy and reliability under complex and changeable environments, and meanwhile, the existing sediment component measurement methods still have the problems of high preparation requirements of test samples, complex syst