Device and method for measuring content of free water in fuel oil on line based on extinction spectrometry and image method

Abstract

The invention relates to a fuel oil free water content on-line measuring device and method based on an extinction spectrometry and an image method. The device comprises a pipeline connecting device, a fuel oil pipeline is connected into the pipeline connecting device, the pipeline connecting device comprises a measuring section, and a measuring area for fuel oil to flow through is formed in the measuring section; the first optical emission unit is used for emitting first incident light to a measurement area; the first optical detection unit is used for receiving transmission light obtained after the first incident light penetrates through a measurement area and is subjected to extinction through free water particles in fuel oil, and outputting corresponding spectral intensity data; the second optical emission unit is used for emitting second incident light to the measurement area to form backlight illumination; the second optical detection unit is used for acquiring a backlight particle image formed after the second incident light passes through the measurement area; and the upper computer is electrically connected with the first optical detection unit and the second optical detection unit. The extinction spectrometry and the image method are combined for use, so that the accuracy of measuring the content of the free water with wide particle size distribution is improved.

Description

Technical Field

[0001] This invention relates to the field of multiphase flow testing technology, and in particular to an online measurement device and method for free water content in fuel oil based on extinction spectroscopy and image methods. Background Technology

[0002] To ensure flight safety, aircraft engine fuel systems must be designed to resist contamination and be validated through fuel contamination tests. These tests require injecting a specific amount of water into the system to prepare fuel with the theoretical contamination concentration for testing. The accuracy of the free water content in the fuel directly affects the test results. The main methods for measuring free water content in fuel are the Karl Fischer method and near-infrared spectroscopy. The Karl Fischer method offers accurate sampling and analysis, but it can only be performed offline, is cumbersome, and uses toxic reagents. Near-infrared spectroscopy offers advantages such as wide applicability, high speed, and no interference, but the system requires precise pre-calibration, and the calibration model is affected by numerous factors, making it difficult to use for real-time detection.

[0003] Patent document CN111851144A describes a test strip for detecting free water in aviation fuel, its preparation method, and a detection device. The test strip comprises: filter paper and a mixture of potassium ferricyanide, ferrous sulfate, and a chelating agent loaded on the surface of the filter paper. The preparation method of the test strip includes: immersing the filter paper in a K3[Fe(CN)6] solution, followed by drying to obtain an intermediate test strip; and coating the surface of the intermediate test strip with a powder mixture of FeSO4 and the chelating agent. This method is simple and easy to operate, and can be detected visually, but it cannot accurately quantify the free water content and is susceptible to human error.

[0004] Therefore, in order to more accurately control the free water content of fuel during the experiment, it is urgent to develop a reliable online measurement device and method for the free water content of fuel. Summary of the Invention

[0005] Therefore, this invention provides an online measurement device and method for free water content in fuel based on extinction spectroscopy and image analysis. This device enables online monitoring of free water content in fuel. By acquiring images and spectral data of free water through a non-contact optical system, it can more promptly reflect the numerical value of free water content in fuel. If a deviation from the required test value is observed, the tester can activate water injection or dewatering equipment for correction. By combining extinction spectroscopy and image analysis, the accuracy of measuring free water content with a wide particle size distribution is improved.

[0006] To address the aforementioned technical problems, this invention provides an online measurement device for free water content in fuel oil based on extinction spectroscopy and image methods. This online measurement device is installed between the contaminated fuel injection device and the fuel pipeline at the test specimen inlet, and includes: A pipeline connection device is connected to a fuel pipeline, the pipeline connection device including a measuring section, the measuring section forming a measuring area for fuel flow; The extinction spectrum measurement optical path includes a first optical emitting unit and a first optical detection unit, which are respectively disposed on both radial sides of the pipeline connection device. The first optical emitting unit is used to emit first incident light into the measurement area; the first optical detection unit is used to receive the transmitted light after the first incident light passes through the measurement area and is extinct by free water particles in the fuel, and output the corresponding spectral intensity data. The backlight imaging optical path includes a second optical emitting unit and a second optical detection unit, which are respectively disposed on both sides of the other radial direction of the pipeline connection device. The second optical emitting unit is used to emit a second incident light into the measurement area to form backlight illumination; the second optical detection unit is used to acquire the backlight particle image formed after the second incident light passes through the measurement area. A host computer is electrically connected to the first optical detection unit and the second optical detection unit, respectively; wherein, the host computer is configured as follows: Based on the spectral intensity data, the total extinction within the measurement area is obtained; Based on the backlit particle image, the particle size distribution and quantity of large-diameter free water particles are obtained. Based on the Mie scattering theory, the first extinction value corresponding to the large-diameter free water particles is calculated; Subtracting the first extinction value from the total extinction value yields the second extinction value corresponding to the small-diameter free water particles. Based on the second extinction value, the particle size distribution and quantity of small-diameter free water particles are obtained by inversion according to Lambbeer's law; The particle size distribution and quantity of the large-diameter free water particles and the small-diameter free water particles are combined to obtain the free water content in the fuel.

[0007] In one embodiment of the present invention, the first optical emitting unit includes an optical fiber light source.

[0008] In one embodiment of the present invention, the first optical detection unit includes a linear array spectrometer.

[0009] In one embodiment of the present invention, the second optical emitting unit includes an LED parallel light source.

[0010] In one embodiment of the present invention, the second optical detection unit includes a lens and an image acquisition camera connected thereto, wherein the image acquisition camera is a CMOS or CCD camera.

[0011] In one embodiment of the present invention, the pipeline connection device includes a square pipe section, transition sections connected to both ends of the square pipe section along the axial direction, and a circular pipe section connected to each of the transition sections. The square pipe section is configured as the measuring section. The measuring section has a first measuring window at both ends along the first radial direction and a second measuring window at both ends along the second radial direction. The first radial direction and the second radial direction are orthogonal.

[0012] In one embodiment of the present invention, each of the circular pipe segments is provided with a flange at its outer end for connection to a fuel line.

[0013] In one embodiment of the present invention, the first measuring window and the second measuring window are made of optical quartz glass.

[0014] In one embodiment of the present invention, the particle size of the large-diameter free water particles is greater than 10 μm; the particle size of the large-diameter free water particles is less than 10 μm.

[0015] This invention also provides an online measurement method for free water content in fuel based on extinction spectroscopy and image methods. Utilizing the aforementioned online measurement device for free water content in fuel based on extinction spectroscopy and image methods, the method includes: An extinction spectral measurement optical path and a backlight imaging optical path were constructed based on a fiber optic light source, a linear array spectrometer, an LED parallel light source, and an image acquisition camera to ensure that the measurement areas of the two are consistent. Start the image acquisition camera and linear array spectrometer; adjust the exposure time, gain and image size of the image acquisition camera so that the maximum gray level of the image is less than the saturated gray level; adjust the integration time of the linear array spectrometer so that the spectral signal intensity is within the measurable range; and keep the exposure time and frame rate of the image acquisition camera consistent with the integration time and frame rate of the linear array spectrometer so as to obtain free water particle information at the same time. The image acquisition camera and the linear array spectrometer simultaneously perform imaging and signal acquisition, and save the acquired backlit particle images and spectral intensity data to the host computer. After performing filtering, noise reduction, background removal, threshold segmentation and binarization on the backlit particle image, the free water particle objects in the measurement area are identified. Combined with the lens magnification and calibration parameters, the particle size distribution and quantity of large-diameter free water particles are calculated. Based on the spectral intensity data, the total extinction within the measurement segment was calculated; The first extinction value corresponding to large-diameter free water particles was calculated based on Mie scattering theory. Subtracting the first extinction value from the total extinction value yields the second extinction value corresponding to the small-diameter free water particles. Based on the second extinction value, the particle size distribution and quantity of small-diameter free water particles are obtained by inversion according to Lambbeer's law; The particle size distribution and quantity of the large-diameter free water particles and the small-diameter free water particles are combined to obtain the total free water content in the fuel.

[0016] The technical solution of the present invention has the following advantages compared with the prior art: This invention discloses an online measurement device and method for free water content in fuel oil based on extinction spectroscopy and image analysis. By combining extinction spectroscopy and image analysis, the complementary advantages of these two optical detection principles are fully utilized. This combination can cover a wide particle size distribution in fuel oil, from submicron to hundreds of micrometers, achieving high-precision online detection across the entire particle size range and avoiding the distortion problems associated with single detection methods. By acquiring image and spectral data of free water through a non-contact optical system, the numerical value of free water content in fuel oil can be reflected more promptly. If a deviation from the required experimental value is observed, the operator can activate water injection or dewatering equipment for correction. The combined use of extinction spectroscopy and image analysis improves the accuracy of measuring free water content across a wide particle size distribution. Attached Figure Description

[0017] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the online measuring device of the present invention.

[0019] Figure 2 These are the original images captured using the image method in this invention.

[0020] Figure 3 This is a schematic diagram of the arrangement of the online measurement device in this invention.

[0021] Figure 4 This is a schematic diagram of the pipeline connection device in this invention.

[0022] Explanation of reference numerals on the accompanying drawings: 1. First optical transmitting unit; 11. Fiber optic light source; 2. First optical detection unit; 21. Linear array spectrometer; 3. Second optical emission unit; 31. LED parallel light source; 4. Second optical detection unit; 41. CMOS or CCD camera; 5. Lens; 6. Pipeline connection device; 60. Measuring section; 61. Square pipe section; 62. Transition section; 63. Circular pipe section; 64. First measuring window; 65. Second measuring window; 66. Flange; 7. Host computer; 81. Test specimen; 82. Fuel line; 83. Contaminated fuel storage tank; 84. Fuel injection pump. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0024] In this invention, when directions (up, down, left, right, front, and back) are described, it is only for the convenience of describing the technical solution of this invention, and does not indicate or imply that the technical features referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0025] In this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number. In the description of this invention, the terms "first" and "second" are used only to distinguish technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0026] In this invention, unless otherwise explicitly defined, the terms "setting," "installing," and "connecting" should be interpreted broadly. For example, they can refer to a direct connection or an indirect connection through an intermediate medium; a fixed connection, a detachable connection, or an integrally formed connection; a mechanical connection, an electrical connection, or a connection capable of mutual communication; or the internal connection of two components or the interaction between two components. Those skilled in the art can reasonably determine the specific meaning of the above terms in this invention based on the specific content of the technical solution.

[0027] Example 1 Reference Figure 1 As shown in the figure, this embodiment presents an online fuel free water content measurement device based on extinction spectroscopy and image methods, referring to... Figure 3 As shown, the online measuring device is located between the contaminated fuel injection device and the fuel line 82 at the inlet of the test piece 81. The contaminated fuel injection device includes a connected contaminated fuel storage tank 83 and a fuel injection pump 84. A fuel line 82 is provided between the fuel injection pump 84 and the inlet of the test piece 81.

[0028] The online measurement device includes: Pipeline connection device 6 is connected to fuel pipeline 82. The pipeline connection device 6 includes a measuring section 60, in which a measuring area for fuel flow is formed. The extinction spectrum measurement optical path includes a first optical emitting unit 1 and a first optical detection unit 2, which are respectively disposed on both radial sides of the pipeline connection device 6. The first optical emitting unit 1 is used to emit first incident light into the measurement area; the first optical detection unit 2 is used to receive the transmitted light after the first incident light passes through the measurement area and is extinct by free water particles in the fuel, and output the corresponding spectral intensity data. The backlight imaging optical path includes a second optical emitting unit 3 and a second optical detection unit 4, respectively disposed on both sides of the other radial direction of the pipeline connecting device 6. The second optical emitting unit 3 is used to emit a second incident light into the measurement area to form backlight illumination; the second optical detection unit 4 is used to acquire the backlight particle image formed after the second incident light passes through the measurement area; (refer to...) Figure 2 As shown; The host computer 7 is electrically connected to the first optical detection unit 2 and the second optical detection unit 4, respectively; wherein, the host computer 7 is configured as follows: Based on the spectral intensity data, the total extinction within the measurement area is obtained; Based on the backlit particle image, the particle size distribution and quantity of large-diameter free water particles are obtained. Based on the Mie scattering theory, calculate the first extinction value corresponding to the large-diameter free water particles; Subtracting the first extinction value from the total extinction value yields the second extinction value corresponding to the small-diameter free water particles. Based on the second extinction value, the particle size distribution and number of small-diameter free water particles are obtained by inversion according to the Beer-Lambert law. The particle size distribution and quantity of the large-diameter free water particles and the small-diameter free water particles are combined to obtain the free water content in the fuel.

[0029] For example, the first optical emitting unit 1 includes an optical fiber light source 11; the first optical detection unit 2 includes a linear array spectrometer 21; the second optical emitting unit 3 includes an LED parallel light source 31; and the second optical detection unit 4 includes a lens 5 and an image acquisition camera connected thereto, wherein the image acquisition camera is a CMOS or CCD camera 41.

[0030] Understandably, the extinction spectrum measurement optical path is as follows: the fiber optic light source 11 is incident on the particle to be measured, and the data is automatically acquired by the linear array spectrometer 21 via the host computer 7. The backlight imaging optical path is as follows: the LED parallel light source 31 is incident on the particle to be measured, and the backlight image of the particle captured by the image acquisition camera is acquired by the host computer 7.

[0031] It should be noted that the design of the measuring section 60 connected to the fuel line 82 has a significant impact on the test results. Therefore, this embodiment has the following settings: (Refer to...) Figure 4 As shown, the pipeline connection device 6 includes a square tube section 61, transition sections 62 connected to both axial ends of the square tube section 61, and circular tube sections 63 connected to each of the transition sections 62. The square tube section 61 is configured as the measuring section 60. The measuring section 60 has first measuring windows 64 at both ends along a first radial direction and second measuring windows 65 at both ends along a second radial direction. The first and second radial directions are orthogonal. By designing the measuring section 60 as a square tube, imaging distortion is avoided to prevent measurement errors. Typically, the test pipeline is a circular tube. To avoid local eddies at the connection point where the circular tube transitions to a square tube, affecting particle flow, a transition section 62 (circular to square) needs to be designed at the connection between the square tube section 61 and the circular tube section 63 to allow the fluid to smoothly and stably complete the flow transition.

[0032] Specifically, each of the circular pipe segments 63 is provided with a flange 66 at its outer end for connecting to the fuel line 82. The first measuring window 64 and the second measuring window 65 are made of optical quartz glass, with smooth inner and outer surfaces free of scratches and contamination.

[0033] It should be noted that the large-diameter free water particles have a particle size greater than 10 μm (≥10 μm); the large-diameter free water particles have a particle size less than 10 μm (<10 μm). The particle size distribution of free water particles in fuel oil is wide, ranging from submicron to hundreds of micrometers, making it difficult to achieve high-precision online measurement of its content using a single measurement method. Image methods have high measurement accuracy for particles with a diameter greater than approximately 10 μm, while extinction methods are more suitable for detecting particles with a diameter less than approximately 10 μm. For the discretely distributed free water particles in fuel oil, this embodiment designs an online measurement optical path structure for fuel oil free water content based on the synergy of extinction spectroscopy and image methods. In the backlight imaging optical path, the parallel light emitted by the LED parallel light source 31 passes through the fuel oil to be measured and is received by the imaging system to form a particle backlight image; in the linear array spectral imaging optical path, the incident light from the wide-wavelength fiber optic light source 11 passes through the fuel medium and is received and imaged by the linear array spectrometer 21. The algorithm processing module of the host computer 7 processes the data, using image analysis to identify and measure the particle size distribution and quantity of larger free water particles in the fuel, and using extinction spectroscopy to obtain the light intensity attenuation information of smaller free water particles. Subsequently, based on the large particle distribution results obtained from the image analysis, Mie scattering theory is used to calculate their extinction contribution. Then, the total light intensity attenuation measured by the spectrometer is subtracted from the extinction value corresponding to the large particles to obtain the extinction amount of the small particles, thus achieving separate calculations and total content inversion for large and small free water particles.

[0034] By acquiring images and spectral data of free water through a non-contact optical system, the value of free water content in fuel can be reflected more promptly. If there is a trend of deviation from the test requirements, the tester can turn on the water injection or water removal equipment for correction. By combining the extinction spectroscopy method and the image method, the accuracy of measuring the free water content with a wide particle size distribution is improved.

[0035] Example 2 This embodiment provides an online measurement method for free water content in fuel oil based on extinction spectroscopy and image methods. Utilizing the aforementioned online measurement device for free water content in fuel oil based on extinction spectroscopy and image methods, the method includes: S1. Based on fiber optic light source 11, linear array spectrometer 21, LED parallel light source 31, and image acquisition camera, construct the extinction spectrum measurement optical path and the backlight imaging optical path to ensure that the measurement areas of the two are consistent. S2. Start the image acquisition camera and linear array spectrometer 21; adjust the exposure time, gain and image size of the image acquisition camera so that the maximum gray value of the image is less than the saturated gray value; adjust the integration time of the linear array spectrometer 21 so that the intensity of the spectral signal is within the measurable range; and make the exposure time and frame rate of the image acquisition camera consistent with the integration time and frame rate of the linear array spectrometer 21 so as to realize the free water particle information at the same time. S3. The image acquisition camera and the linear array spectrometer 21 simultaneously perform imaging and signal acquisition, and save the acquired backlight particle images and spectral intensity data to the host computer 7. S4. After performing filtering, noise reduction, background removal, threshold segmentation and binarization on the backlit particle image, identify the free water particle objects in the measurement area. Combined with the magnification of lens 5 and calibration parameters, calculate the particle size distribution and quantity of large-diameter free water particles. S5. Based on the spectral intensity data, the total extinction within the measurement segment 60 is calculated; S6. Calculate the first extinction value corresponding to large-diameter free water particles based on Mie scattering theory; S7. Subtract the first extinction value from the total extinction amount to obtain the second extinction value corresponding to the small-diameter free water particles; S8. Based on the second extinction value, the particle size distribution and number of small-diameter free water particles are obtained by inversion according to Lambbeer's law; S9. The particle size distribution and quantity of the large-diameter free water particles and the small-diameter free water particles are combined to obtain the total free water content in the fuel.

[0036] Example 3 This embodiment provides an online measurement method for free water content in fuel based on extinction spectroscopy and image method. It utilizes an online measurement device for free water content in fuel based on extinction spectroscopy and image method, which mainly includes: fiber optic light source 11, linear array spectrometer 21, LED parallel light source 31, CMOS camera, lens 5, and host computer 7.

[0037] The fiber optic light source 11 has a power of 50W and a wavelength range of 200–1000nm; The linear array spectrometer 21 has a resolution of 1×1360 and a wavelength range of 380–850 nm. The LED parallel light source 31 has a power of 10W and an emission wavelength of 532nm; The CMOS camera has a resolution of 2064×1544, a maximum frame rate of 160 frames per second, and a maximum output bit depth of 12-bit grayscale image. The lens 5 is connected to a CMOS camera and is used to acquire backlit imaging images.

[0038] The steps for online measurement are as follows: S1, Press Figure 1 The measurement device is arranged as shown to ensure that the measurement areas of the spectral imaging optical path and the backlight imaging optical path coincide, and to ensure that the camera and the spectrometer collect data from the same area.

[0039] S2. Focus the CMOS camera to the center of the measurement area and adjust the light intensity input of the linear array spectrometer 21 to a suitable range to ensure stable signal acquisition.

[0040] S3. Arrange the 532nm LED parallel light source 31 and the CMOS camera in the same horizontal straight line, and arrange the fiber optic light source 11 and the linear array spectrometer 21 in the vertical direction.

[0041] Open the camera acquisition software and adjust the camera exposure time τ to make the image grayscale distribution moderate and the maximum grayscale value less than the saturation grayscale value. At the same time, turn on the spectrometer and adjust its integration time so that the received light intensity is within the range that the spectrometer can display.

[0042] The exposure time of the CMOS camera is synchronized with the integration time of the linear array spectrometer to ensure that the image and the spectral signal are acquired at the same time.

[0043] S4, the CMOS camera and the linear array spectrometer 21 simultaneously perform imaging and signal acquisition, and save the acquired backlight particle images and spectral intensity data to the host computer 7.

[0044] S5. Process the spectral data and the backlight particle image separately: First, after processing the backlit particle image including filtering and denoising, background removal, threshold segmentation, and binarization, free water particles within the measurement area are identified. Combining the magnification of lens 5 and calibration parameters, the particle size distribution and quantity of large-diameter free water particles are calculated. Based on spectral intensity data, the total extinction within the measurement segment 60 is calculated. The first extinction value corresponding to the large-diameter free water particles is calculated according to Mie scattering theory. The first extinction value is subtracted from the total extinction to obtain the second extinction value corresponding to the small-diameter free water particles. Based on the second extinction value, the particle size distribution and quantity of small-diameter free water particles are obtained by inversion according to the Lambbeer law. The particle size distribution and quantity of the large-diameter and small-diameter free water particles are then fused to obtain the total free water content in the fuel.

[0045] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0046] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0047] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0048] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0049] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, 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. An online measurement device for free water content in fuel oil based on extinction spectroscopy and image methods, characterized in that, The online measuring device is located between the contaminated fuel injection device and the fuel line (82) at the inlet of the test piece (81), and includes: A pipeline connection device (6) is connected to a fuel pipeline (82). The pipeline connection device (6) includes a measuring section (60), in which a measuring area for fuel flow is formed. The extinction spectrum measurement optical path includes a first optical emission unit (1) and a first optical detection unit (2), which are respectively arranged on both sides of the pipeline connection device (6). The first optical emission unit (1) is used to emit a first incident light into the measurement area; the first optical detection unit (2) is used to receive the transmitted light after the first incident light passes through the measurement area and is extinct by free water particles in the fuel, and output the corresponding spectral intensity data. The backlight imaging optical path includes a second optical emitting unit (3) and a second optical detection unit (4), which are respectively disposed on both sides of the other radial direction of the pipeline connection device (6). The second optical emitting unit (3) is used to emit a second incident light into the measurement area to form backlight illumination; the second optical detection unit (4) is used to acquire the backlight particle image formed after the second incident light passes through the measurement area. The host computer (7) is electrically connected to the first optical detection unit (2) and the second optical detection unit (4), respectively; wherein, the host computer (7) is configured as follows: Based on the spectral intensity data, the total extinction within the measurement area is obtained; Based on the backlit particle image, the particle size distribution and quantity of large-diameter free water particles are obtained. Based on the Mie scattering theory, the first extinction value corresponding to the large-diameter free water particles is calculated; Subtracting the first extinction value from the total extinction value yields the second extinction value corresponding to the small-diameter free water particles. Based on the second extinction value, the particle size distribution and quantity of small-diameter free water particles are obtained by inversion according to Lambbeer's law; The particle size distribution and quantity of the large-diameter free water particles and the small-diameter free water particles are combined to obtain the free water content in the fuel.

2. The online measurement device for free water content in fuel oil based on extinction spectroscopy and image method according to claim 1, characterized in that, The first optical emitting unit (1) includes an optical fiber light source (11).

3. The online measurement device for free water content in fuel oil based on extinction spectroscopy and image method according to claim 1, characterized in that, The first optical detection unit (2) includes a linear array spectrometer (21).

4. The online measurement device for free water content in fuel oil based on extinction spectroscopy and image method according to claim 1, characterized in that, The second optical emission unit (3) includes an LED parallel light source (31).

5. The online measurement device for free water content in fuel oil based on extinction spectroscopy and image method according to claim 1, characterized in that, The second optical detection unit (4) includes a lens (5) and an image acquisition camera connected thereto, wherein the image acquisition camera is a CMOS or CCD camera (41).

6. The online measurement device for free water content in fuel oil based on extinction spectroscopy and image method according to claim 1, characterized in that, The pipeline connection device (6) includes a square tube section (61), a transition section (62) connected to both ends of the square tube section (61) along the axial direction, and a circular tube section (63) connected to each of the transition sections (62). The square tube section (61) is configured as the measuring section (60). The measuring section (60) has a first measuring window (64) at both ends along the first radial direction and a second measuring window (65) at both ends along the second radial direction. The first radial direction and the second radial direction are orthogonal.

7. The online measurement device for free water content in fuel oil based on extinction spectroscopy and image method according to claim 6, characterized in that, Each of the circular pipe sections (63) has a flange (66) at its outer end for connecting to the fuel line (82).

8. The online measurement device for free water content in fuel oil based on extinction spectroscopy and image method according to claim 6, characterized in that, The first measurement window (64) and the second measurement window (65) are made of optical quartz glass.

9. The online measurement device for free water content in fuel oil based on extinction spectroscopy and image method according to claim 1, characterized in that, The large-diameter free water particles have a particle size of 10 μm or more; the large-diameter free water particles have a particle size of 10 μm or less.

10. An online method for measuring the free water content of fuel oil based on extinction spectroscopy and image methods, characterized in that, The method of using the online fuel free water content measurement device based on extinction spectroscopy and image method according to any one of claims 1-9 includes: Based on the fiber optic light source (11), linear array spectrometer (21), LED parallel light source (31), and image acquisition camera, construct the extinction spectrum measurement optical path and the backlight imaging optical path to ensure that the measurement areas of the two are consistent; Start the image acquisition camera and the linear array spectrometer (21); adjust the exposure time, gain and image size of the image acquisition camera so that the maximum gray value of the image is less than the saturated gray value; adjust the integration time of the linear array spectrometer (21) so that the intensity of the spectral signal is within the measurable range; and make the exposure time and frame rate of the image acquisition camera consistent with the integration time and frame rate of the linear array spectrometer (21) so as to realize the free water particle information at the same time. The image acquisition camera and the linear array spectrometer (21) perform imaging and signal acquisition simultaneously, and save the acquired backlight particle images and spectral intensity data to the host computer (7). After performing filtering, noise reduction, background removal, threshold segmentation and binarization on the backlit particle image, the free water particle objects in the measurement area are identified. Combined with the magnification of the lens (5) and the calibration parameters, the particle size distribution and quantity of large-diameter free water particles are calculated. Based on the spectral intensity data, the total extinction within the measurement segment (60) is calculated; The first extinction value corresponding to large-diameter free water particles was calculated based on Mie scattering theory. Subtracting the first extinction value from the total extinction value yields the second extinction value corresponding to the small-diameter free water particles. Based on the second extinction value, the particle size distribution and quantity of small-diameter free water particles are obtained by inversion according to Lambbeer's law; The particle size distribution and quantity of the large-diameter free water particles and the small-diameter free water particles are combined to obtain the total free water content in the fuel.

Images