Study of Particle Size Measurement by the Extinction Method in Flame
The laser extinction method (LEM) is particularly suitable for measuring particle sizes in flames because this method, which is based on the Beer–Lambert law, is non-intrusive and easy to implement. In the LEM, the interpretation of the extinction data is usually developed under the assumption that...
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| Fformat: | Erthygl |
| Iaith: | English |
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MDPI AG
2023-06-01
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| Cyfres: | Energies |
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| Mynediad Ar-lein: | https://www.mdpi.com/1996-1073/16/12/4792 |
| _version_ | 1827737543224852480 |
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| author | Hengsheng Xiang Bo Cheng Chengfei Zhang Wensheng Qiao |
| author_facet | Hengsheng Xiang Bo Cheng Chengfei Zhang Wensheng Qiao |
| author_sort | Hengsheng Xiang |
| collection | DOAJ |
| description | The laser extinction method (LEM) is particularly suitable for measuring particle sizes in flames because this method, which is based on the Beer–Lambert law, is non-intrusive and easy to implement. In the LEM, the interpretation of the extinction data is usually developed under the assumption that light extinction due to scattering is a result of the superposition of single scattering by individual particles; however, this could be violated for flames with dense concentrations of particles in which multiple scattering could occur. Quantifying the effect of multiple scattering under general conditions is still a formidable problem. In this work, we carried out a series of careful measurements of the laser extinction using standard particles of various known sizes, number densities and optical path lengths, all under the condition that the acceptance angle of the detector was limited to nearly zero. Combined with a four-flux model, we quantitatively analyzed the effect of multiple scattering on the size measurement using the LEM. The results show that the effect of multiple scattering could be ignored when the optical thickness is less than two under strict restrictions on the detector acceptance angle. Guided by this, the size distribution of an alumina (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>Al</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>3</mn></msub></mrow></semantics></math></inline-formula>) particle sample was measured by the LEM with dual wavelengths. Parameterized distributions were solved with the help of graph plotting, and the results compared well with the measurement from the Malvern particle size analyzer. The same method was then used to measure the particle size distribution in the plume of a solid rocket motor (SRM). The use of an off-axis parabolic mirror in the experimental setup could suppress the jitter of light passing through the SRM plume, and the particle size in the plume of the measured SRM was in the order of microns. |
| first_indexed | 2024-03-11T02:30:26Z |
| format | Article |
| id | doaj.art-0ca4966b76d0462dbb01b8d36f7adf8f |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-03-11T02:30:26Z |
| publishDate | 2023-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-0ca4966b76d0462dbb01b8d36f7adf8f2023-11-18T10:14:10ZengMDPI AGEnergies1996-10732023-06-011612479210.3390/en16124792Study of Particle Size Measurement by the Extinction Method in FlameHengsheng Xiang0Bo Cheng1Chengfei Zhang2Wensheng Qiao3Center for Combustion Energy, Tsinghua University, Beijing 100084, ChinaThe Sixth Institute, 601 Branch of China Aeronautical Science and Technology Corporation, Hohhot 010076, ChinaThe Sixth Institute, 601 Branch of China Aeronautical Science and Technology Corporation, Hohhot 010076, ChinaThe Sixth Institute, 601 Branch of China Aeronautical Science and Technology Corporation, Hohhot 010076, ChinaThe laser extinction method (LEM) is particularly suitable for measuring particle sizes in flames because this method, which is based on the Beer–Lambert law, is non-intrusive and easy to implement. In the LEM, the interpretation of the extinction data is usually developed under the assumption that light extinction due to scattering is a result of the superposition of single scattering by individual particles; however, this could be violated for flames with dense concentrations of particles in which multiple scattering could occur. Quantifying the effect of multiple scattering under general conditions is still a formidable problem. In this work, we carried out a series of careful measurements of the laser extinction using standard particles of various known sizes, number densities and optical path lengths, all under the condition that the acceptance angle of the detector was limited to nearly zero. Combined with a four-flux model, we quantitatively analyzed the effect of multiple scattering on the size measurement using the LEM. The results show that the effect of multiple scattering could be ignored when the optical thickness is less than two under strict restrictions on the detector acceptance angle. Guided by this, the size distribution of an alumina (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>Al</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>3</mn></msub></mrow></semantics></math></inline-formula>) particle sample was measured by the LEM with dual wavelengths. Parameterized distributions were solved with the help of graph plotting, and the results compared well with the measurement from the Malvern particle size analyzer. The same method was then used to measure the particle size distribution in the plume of a solid rocket motor (SRM). The use of an off-axis parabolic mirror in the experimental setup could suppress the jitter of light passing through the SRM plume, and the particle size in the plume of the measured SRM was in the order of microns.https://www.mdpi.com/1996-1073/16/12/4792laser extinction methodmultiple scatteringparticle size distributionlight jitter |
| spellingShingle | Hengsheng Xiang Bo Cheng Chengfei Zhang Wensheng Qiao Study of Particle Size Measurement by the Extinction Method in Flame Energies laser extinction method multiple scattering particle size distribution light jitter |
| title | Study of Particle Size Measurement by the Extinction Method in Flame |
| title_full | Study of Particle Size Measurement by the Extinction Method in Flame |
| title_fullStr | Study of Particle Size Measurement by the Extinction Method in Flame |
| title_full_unstemmed | Study of Particle Size Measurement by the Extinction Method in Flame |
| title_short | Study of Particle Size Measurement by the Extinction Method in Flame |
| title_sort | study of particle size measurement by the extinction method in flame |
| topic | laser extinction method multiple scattering particle size distribution light jitter |
| url | https://www.mdpi.com/1996-1073/16/12/4792 |
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