Dust concentration measuring instrument based on light scattering method

Abstract

The invention discloses a dust concentration measuring instrument based on a light scattering method. The dust concentration measuring instrument comprises a laser emitting unit, a scattered light collecting unit, a gas path unit and a control unit. The gas path unit meets the Reynolds number-Stokes number cooperation criterion, the particle distribution uniformity is improved, and the sampling deviation caused by fluid detuning of a traditional gas path is solved. The particle retention rate model calculates the retention rate based on the Stokes sedimentation velocity and the cavity length so as to correct the light intensity signal and reduce the underestimation of the concentration of PM2.5-PM10. Non-linear compensation adopts a hyperbolic tangent function to suppress high-concentration saturation errors and expand the equipment range. The complex refractive index drift is dynamically corrected by a temperature and humidity-refractive index compensation algorithm, and the environmental interference error is remarkably reduced at high humidity. In addition, the scattered light collecting unit restrains noise through light path angular domain constraint, and the air path unit adopts a two-stage compression air inlet to enhance the particle conveying efficiency. The measuring instrument is suitable for the field of industrial environmental protection and health monitoring, and the full-scale measurement precision and robustness are comprehensively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental detection, and in particular to a dust concentration measuring instrument based on a light scattering method. Background Art

[0002] Light scattering dust concentration measurement technology has been widely used in industrial environmental protection, occupational health monitoring and other fields due to its advantages such as fast response speed and non-contact measurement. Its basic principle is to detect the intensity of scattered light (complex refractive index) of particles by irradiating the dust-laden airflow with laser and invert the concentration value. However, the existing technology still has the following key bottlenecks: (1) The gas path structure of the traditional measuring instrument does not fully consider the fluid dynamics effect. During the transmission process, particles are unevenly distributed due to gravity sedimentation or turbulent diffusion, resulting in detuning of the Stokes number (Stk) and the Reynolds number (Re), which significantly reduces the representativeness of the sampling. (2) When the dust concentration exceeds the critical threshold, the scattered light intensity and concentration have a nonlinear relationship. The output signal of the existing sensor is severely saturated, resulting in a sharp drop in measurement accuracy under high concentration conditions. (3) Changes in air temperature and humidity will change the complex refractive index of particles, which directly affects the scattering phase function. The existing system lacks a dynamic refractive index compensation mechanism, and the error can reach more than 30% in complex environments. (4) The retention time of particles in the sensor cavity is related to the sedimentation velocity. Traditional methods ignore the attenuation effect of the retention rate on the light intensity signal, resulting in an underestimation of the concentration.

[0003] While some improvements attempt to mitigate these issues through hardware optimization (such as multi-stage gas path design) or simple linear compensation, they fail to address the coupled effects of fluid dynamics constraints, signal nonlinearity, and environmental interference. Therefore, a high-precision dust concentration meter that integrates gas path parameter optimization, dynamic compensation algorithms, and environmental adaptive mechanisms is urgently needed. Summary of the Invention

[0004] In order to overcome the above-mentioned defects in the prior art, the present invention provides a dust concentration measuring instrument based on a light scattering method.

[0005] The technical solution adopted by the present invention is as follows: a dust concentration measuring instrument based on light scattering method, comprising a laser emitting unit, a scattered light collecting unit, an air path unit and a control unit, wherein the air path unit satisfies the Reynolds number-Stokes number synergy criterion.

[0006]

[0007]

[0008] in, is the Reynolds number, is the Stokes number, is the air flow velocity, is the hydraulic diameter of the gas path, is the kinematic viscosity of air, is the particle density, is the particle size, is the air dynamic viscosity; The control unit executes a dynamic compensation algorithm, including: a. Particle retention rate model

[0009]

[0010] in, is the particle retention rate, is the Stokes settling velocity of the particle, is the sensor cavity length, is the corrected light intensity signal, is the measured light intensity signal; b. Nonlinear compensation function

[0011] in, is the concentration value after compensation, is the original output concentration of the sensor, is the saturation concentration threshold, is the hyperbolic tangent function.

[0012] Preferably, the optical path parameters of the scattered light collecting unit satisfy

[0013]

[0014]

[0015]

[0016]

[0017] in is the laser wavelength, 、 is the polar angle of the spherical coordinate system, 、 is the azimuth in the spherical coordinate system.

[0018] Preferably, the air circuit unit has a two-stage compression air inlet, which satisfies

[0019]

[0020] in, is the compression ratio, 、 are the cross-sectional areas of the inlet and throat of the air inlet pipe of the air circuit unit, is the axial length of the air inlet pipe of the air path unit.

[0021] Preferably, the control unit executes a temperature and humidity-refractive index compensation algorithm

[0022] in, is the effective complex refractive index, is the reference complex refractive index, is the refractive index correction amplitude, is the measured value of relative humidity, is the humidity reference standard, is the humidity impact index.

[0023] Preferably, when the relative humidity When the effective refractive index formula is updated

[0024] in, , , .

[0025] Preferably, the Stokes settling velocity of the particles

[0026] in, is the acceleration due to gravity.

[0027] The second technical solution adopted by the present invention is as follows: a method for dynamic compensation of dust concentration of a dust concentration measuring instrument based on a light scattering method, comprising the following steps: Step 1: Calculate the particle retention rate using the particle retention rate model , obtain the corrected light intensity signal ; Step 2: Use the corrected light intensity signal Calculate the base complex refractive index ; Step 3: Calculate the effective complex refractive index using the temperature and humidity-refractive index compensation algorithm ; Step 4: Calculate the original output concentration of the sensor using the light scattering inversion algorithm ; Step 5: Obtain the compensated concentration value through the nonlinear compensation function .

[0028] The present invention has the following beneficial effects: 1. Improved gas transmission efficiency: The gas path unit is optimized through the Reynolds number-Stokes number synergy principle to improve the uniformity of particle distribution and the matching degree between Stokes settling velocity and air flow velocity, thus solving the sampling deviation problem caused by Reynolds number-Stokes number detuning in traditional gas paths. 2. High-concentration nonlinear error suppression: Using the hyperbolic tangent compensation function, the measurement range is extended to more than 2.5 times that of conventional equipment, reducing the nonlinear error near the saturation concentration threshold; 3. Dynamic compensation for environmental interference: Based on the temperature, humidity and refractive index algorithm, the complex refractive index change is corrected in real time. When the relative humidity is 40-90%, the humidity sensitivity is reduced, and the refractive index drift is significantly suppressed under high temperature conditions. 4. Accurate correction of retention effect: The particle retention rate model eliminates sedimentation losses and reduces the underestimation rate of PM2.5-PM10 particle concentrations; 5.Optimization of optical signal-to-noise ratio: The scattered light collection unit meets the optical path constraints, effectively suppresses edge scattering noise, and improves signal stability; 6. Comprehensive performance breakthrough: Two-stage compression gas circuit combined with dynamic compensation algorithm improves full-range measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structural principle of an embodiment of the present invention.

[0030] Figure 2 1 is a schematic diagram of the overall measurement process of an embodiment of the present invention.

[0031] Figure 3 2 is a schematic diagram of a dynamic compensation process according to an embodiment of the present invention.

[0032] Laser emitting unit 1; scattered light collecting unit 2; gas path unit 3; control unit 4, reflector 5. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the embodiments and drawings.

[0034] In the embodiment, Figure 1-Figure 3 As shown, a dust concentration measuring instrument based on the light scattering method includes a laser emitting unit 1, a scattered light collecting unit 2, an air path unit 3 and a control unit 4.

[0035] Gas circuit unit 3 meets the Reynolds number-Stokes number synergy criterion

[0036]

[0037]

[0038] in, is the Reynolds number, is the Stokes number, is the air flow velocity, is the hydraulic diameter of the gas path, is the kinematic viscosity of air, is the particle density, is the particle size, is the dynamic viscosity of air.

[0039] The control unit 4 executes a dynamic compensation algorithm, including: a. Particle retention rate model

[0040]

[0041] in, is the particle retention rate, is the Stokes settling velocity of the particle, is the sensor cavity length, is the corrected light intensity signal, is the measured light intensity signal; b. Nonlinear compensation function

[0042] in, is the concentration value after compensation, is the original output concentration of the sensor, is the saturation concentration threshold, is the hyperbolic tangent function.

[0043] This embodiment adopts the Reynolds number-Stokes number synergy criterion, that is, , ensuring even distribution of particulate matter in the gas path, resolving sampling bias caused by fluid detuning in traditional equipment and improving representativeness. A particle retention rate model corrects for light intensity signal attenuation due to gravitational settling, reducing underestimation of PM2.5-PM10 particle concentrations. A nonlinear compensation function employs a hyperbolic tangent function to suppress nonlinear errors in high-concentration saturation regions, extending the measurement range to over 2.5 times that of conventional equipment.

[0044] In the embodiment, the optical path parameters of the scattered light collecting unit 2 satisfy

[0045]

[0046]

[0047]

[0048]

[0049] in is the laser wavelength, 、 is the polar angle of the spherical coordinate system, 、 This embodiment effectively suppresses edge scattering noise and improves signal stability and detection sensitivity by constraining the scattering angle range and wavelength correlation.

[0050] In the embodiment, the air circuit unit 3 has a two-stage compression air inlet to meet

[0051]

[0052] in, is the compression ratio, 、 are the cross-sectional areas of the inlet and throat of the air inlet pipe of the air circuit unit 3, is the axial length of the air inlet pipe of air path unit 3. The two-stage compression air inlet design accelerates airflow and reduces turbulent diffusion, enhancing particle transport efficiency and combining with dynamic algorithms to achieve improved full-range accuracy.

[0053] Preferably, the control unit 4 executes a temperature and humidity-refractive index compensation algorithm

[0054] in, is the effective complex refractive index, is the reference complex refractive index, is the refractive index correction amplitude, is the measured value of relative humidity, is the humidity reference standard, The humidity impact index (RHI) is a temperature-humidity-refractive index algorithm that corrects complex refractive index drift in real time, significantly reducing humidity sensitivity within a relative humidity range of 40% to 90%, and significantly reducing errors in complex environments.

[0055] In the embodiment, when the relative humidity of the environment is When the effective refractive index formula is updated

[0056] in, , , When relative humidity When it is too large, a segmented correction formula is used to solve the problem of nonlinear drift of refractive index under extreme humidity and improve measurement robustness.

[0057] In the embodiment, the Stokes settling velocity of the particle

[0058] in, is the acceleration due to gravity. The Stokes settling velocity formula provides a physical basis for the retention rate model, ensuring more reliable correction of settling losses for PM2.5-PM10 particles.

[0059] In the embodiment, Figure 2 As shown in the figure, the complete steps for measuring dust concentration are as follows, focusing on the dynamic compensation process: Step 1. Correct the light intensity signal based on particle retention rate.

[0060] Air sampling: The air to be tested is sucked in at a stable flow rate through an air pump.

[0061] Particle pretreatment: Filter out large particles first to ensure smooth airflow through the detection area.

[0062] Retention rate correction: Calculate the proportion of particles that actually pass through the laser area (retention rate) and amplify and compensate the original light intensity signal.

[0063] Step 2. Calculation of the base complex refractive index.

[0064] Light scattering detection: Laser is used to illuminate the particles, and the side detector receives the scattered light intensity.

[0065] Benchmark parameter calibration: Under standard temperature and humidity conditions, the “basic optical properties” of the particles, namely the benchmark complex refractive index, are inferred based on the corrected light intensity signal.

[0066] Step 3. Dynamic compensation of temperature and humidity.

[0067] Environmental parameter monitoring: real-time collection of temperature and humidity sensor data.

[0068] Optical property correction: Dynamically adjust the complex refractive index value based on the current temperature and humidity compared to standard conditions to compensate for the optical property deviation caused by water film attached to the particle surface when the humidity increases or temperature changes.

[0069] Step 4. Invert the original concentration using Mie scattering.

[0070] Concentration inversion calculation: Calculate the preliminary concentration value using the compensated complex refractive index and light intensity signal combined with the preset typical particle size distribution model.

[0071] Step 5. Non-linear concentration compensation.

[0072] Nonlinear compensation function calibration: Hyperbolic tangent function is used to suppress nonlinear errors in high concentration saturation areas.

[0073] Final output: Output the calibrated concentration value and automatically reset to zero regularly to prevent zero drift.

[0074] Obviously, the above embodiments of the present invention are merely examples for illustrating the present invention and are not intended to limit the implementation of the present invention. Other obvious changes or modifications derived from the essence of the present invention still fall within the scope of protection of the present invention.

Claims

1. A dust concentration measuring instrument based on a light scattering method, comprising a laser emitting unit (1), a scattered light collecting unit (2), an air path unit (3) and a control unit (4), characterized in that: The gas circuit unit (3) satisfies the Reynolds number-Stokes number synergy criterion in, is the Reynolds number, is the Stokes number, is the air flow velocity, is the hydraulic diameter of the gas path, is the kinematic viscosity of air, is the particle density, is the particle size, is the air dynamic viscosity; The control unit (4) executes a dynamic compensation algorithm, including: a. Particle retention rate model in, is the particle retention rate, is the Stokes settling velocity of the particle, is the sensor cavity length, is the corrected light intensity signal, is the measured light intensity signal; b. Nonlinear compensation function in, is the concentration value after compensation, is the original output concentration of the sensor, is the saturation concentration threshold, is the hyperbolic tangent function.

2. The dust concentration measuring instrument based on the light scattering method according to claim 1, characterized in that: The optical path parameters of the scattered light collecting unit (2) satisfy in is the laser wavelength, 、 is the polar angle of the spherical coordinate system, 、 is the azimuth in the spherical coordinate system.

3. The dust concentration measuring instrument based on the light scattering method according to claim 1, characterized in that: The air circuit unit (3) has a two-stage compression air inlet, which satisfies in, is the compression ratio, 、 are the cross-sectional areas of the inlet and throat of the air inlet pipe of the air circuit unit (3), is the axial length of the air inlet pipe of the air path unit (3).

4. The dust concentration measuring instrument based on the light scattering method according to claim 1, characterized in that: The control unit (4) executes a temperature and humidity-refractive index compensation algorithm in, is the effective complex refractive index, is the reference complex refractive index, is the refractive index correction amplitude, is the measured value of relative humidity, is the humidity reference standard, is the humidity impact index.

5. The dust concentration measuring instrument based on the light scattering method according to claim 4, characterized in that: When the relative humidity When the effective refractive index formula is updated in, , , .

6. The dust concentration measuring instrument based on the light scattering method according to claim 1, characterized in that: The Stokes settling velocity of the particle in, is the acceleration due to gravity.

7. The method for dynamic compensation of dust concentration of a dust concentration measuring instrument based on light scattering method according to any one of claims 1 to 6, characterized in that Here are the steps: Step 1: Calculate the particle retention rate using the particle retention rate model , obtain the corrected light intensity signal ; Step 2: Use the corrected light intensity signal Calculate the base complex refractive index ; Step 3: Calculate the effective complex refractive index using the temperature and humidity-refractive index compensation algorithm ; Step 4: Calculate the original output concentration of the sensor using the light scattering inversion algorithm ; Step 5: Obtain the compensated concentration value through the nonlinear compensation function .

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