火灾烟颗粒与非火灾干扰颗粒光散射特性的研究
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摘要
烟雾是火灾早期最重要的特征参量之一,火灾探测领域应用最广泛的光电感烟探测技术正是基于烟颗粒的光散射原理进行火灾探测。对烟颗粒的光散射进行模拟计算是研究火灾烟颗粒光散射特性的重要手段,目前对于火灾烟颗粒光散射的数值计算多采用球形或椭球模型,实际上,火灾烟颗粒的形貌与球形和椭球均存在显著差异,烟颗粒的SEM图像表明,烟颗粒具有近似分形的结构。本文利用DDA方法计算了随机取向的火灾烟颗粒分形凝团以及同体积的球形颗粒的光散射Muller矩阵,并对两者的归一化Muller矩阵元素随散射角的分布进行了比较。结果表明:火灾烟颗粒分形模型和球形模型的归一化矩阵元素F1 2 (θ) / F11(θ)、F2 2 (θ) / F11(θ)和F3 4 (θ) / F11(θ)随散射角的分布情况存在显著差异;利用两种模型的光散射矩阵元素F2 2 (θ)/ F11(θ)的差异,可以有效区分烟颗粒与球形干扰颗粒。
现有的光电感烟探测器通过直接探测火灾中生成的烟颗粒散射光的光强进行火灾报警,容易受非火灾烟雾颗粒如水汽、粉尘等干扰而发生误报,其中粉尘是一种广泛存在的误报源。目前烟颗粒光散射特征的研究多针对单个凝团,实际上烟雾是具有近似分形结构、基本颗粒数N近似服从对数正态分布、空间随机取向的烟颗粒群。因此,烟颗粒群光散射的计算必须对烟颗粒凝团的粒径及空间取向进行统计平均。本文利用DDA方法计算了服从一定粒径分布的随机取向的烟颗粒群和粉尘颗粒的光散射Muller矩阵,比较了两者光散射矩阵元素随散射角分布的差异。结果表明:烟颗粒和粉尘颗粒的光散射Muller矩阵元素F1 1 (θ) / F11(0)、F2 2 (θ) / F11(θ)、F3 3 (θ) / F11(θ)、F4 4 (θ) / F11(θ)、F1 2 (θ) / F11(θ)和F3 4 (θ) / F11(θ)随散射角的分布存在显著差异。其中光散射矩阵元素F2 2 (θ) / F11(θ)的差异实验中较容易测得,利用两者光散射矩阵元素F2 2 (θ)/ F11(θ)随散射角分布的差异便可有效地区分烟颗粒和粉尘颗粒,这对降低光电感烟探测器的误报率具有重要意义。
Smoke is one of the most important characteristics of early fires. Photoelectric smoke detection technology, based on the principle of light scattering of particles, has been widely used in the field of fire detection. It is important to research light scattering from fire smoke particles by numerical calculation. Traditionally, spherical or spheroid models were used to approximate the shape of smoke particles for light scattering calculations. But actually, smoke particles have a similar fractal structure, which is different from spherical structure. Using the discrete-dipole approximation method, the light scattering Muller matrices were computed for the randomly oriented fractal aggregate, as well as the spherical particle with the same volume of aggregate, and then both normalized Muller matrix elements were compared. The results indicate that the angle distributions of the normalized matrix elements F1 1 (θ) / F11(0)、F2 2 (θ) / F11(θ) and F3 4 (θ) / F11(θ) have significant differences between the fractal model and spherical model. We can discriminate spherical non-fire aerosols from smoke particles, using the difference of F2 2 (θ) / F11(θ) between fractal model and spherical model.
Because of only sensing the intensity of scattered light by smoke particles for fire alarm, photoelectric smoke detector is often interfered by non-fire smoke particles, such as water vapor, dust and other nuisance. Presently, most study on light scattering from smoke particles are focused on single aggregate. In fact, the smoke has a similar fractal structure. The number of primary particles approximately obeys log-normal distribution, and aggregates are in random orientation. Calculation of light scattering from particles must be averaged statistically in aggregate sizes and spatial orientations. Using the discrete-dipole approximation method, the scattering Muller matrices were computed for the randomly oriented smoke particles with a certain size distribution, as well as the dust particle. Both normalized Muller matrix elements were compared and analyzed. The results show that there are significant differences between the angle distributions of the normalized matrix elements F1 1 (θ) / F11(0), F2 2 (θ)/ F11(θ), F3 3 (θ) / F11(θ), F4 4 (θ) / F11(θ), F1 2 (θ) / F11(θ) and F3 4 (θ) / F11(θ) for smoke particles and dust particle. Matrix elements F2 2 (θ) / F11(θ) can be easily measured in experiment, so we can discriminate dust from smoke particles, using the difference of F2 2 (θ)/ F11(θ) between them. It could be an effective way to reduce false alarm rate of photoelectric smoke detectors.
现有的光电感烟探测器通过直接探测火灾中生成的烟颗粒散射光的光强进行火灾报警,容易受非火灾烟雾颗粒如水汽、粉尘等干扰而发生误报,其中粉尘是一种广泛存在的误报源。目前烟颗粒光散射特征的研究多针对单个凝团,实际上烟雾是具有近似分形结构、基本颗粒数N近似服从对数正态分布、空间随机取向的烟颗粒群。因此,烟颗粒群光散射的计算必须对烟颗粒凝团的粒径及空间取向进行统计平均。本文利用DDA方法计算了服从一定粒径分布的随机取向的烟颗粒群和粉尘颗粒的光散射Muller矩阵,比较了两者光散射矩阵元素随散射角分布的差异。结果表明:烟颗粒和粉尘颗粒的光散射Muller矩阵元素F1 1 (θ) / F11(0)、F2 2 (θ) / F11(θ)、F3 3 (θ) / F11(θ)、F4 4 (θ) / F11(θ)、F1 2 (θ) / F11(θ)和F3 4 (θ) / F11(θ)随散射角的分布存在显著差异。其中光散射矩阵元素F2 2 (θ) / F11(θ)的差异实验中较容易测得,利用两者光散射矩阵元素F2 2 (θ)/ F11(θ)随散射角分布的差异便可有效地区分烟颗粒和粉尘颗粒,这对降低光电感烟探测器的误报率具有重要意义。
Smoke is one of the most important characteristics of early fires. Photoelectric smoke detection technology, based on the principle of light scattering of particles, has been widely used in the field of fire detection. It is important to research light scattering from fire smoke particles by numerical calculation. Traditionally, spherical or spheroid models were used to approximate the shape of smoke particles for light scattering calculations. But actually, smoke particles have a similar fractal structure, which is different from spherical structure. Using the discrete-dipole approximation method, the light scattering Muller matrices were computed for the randomly oriented fractal aggregate, as well as the spherical particle with the same volume of aggregate, and then both normalized Muller matrix elements were compared. The results indicate that the angle distributions of the normalized matrix elements F1 1 (θ) / F11(0)、F2 2 (θ) / F11(θ) and F3 4 (θ) / F11(θ) have significant differences between the fractal model and spherical model. We can discriminate spherical non-fire aerosols from smoke particles, using the difference of F2 2 (θ) / F11(θ) between fractal model and spherical model.
Because of only sensing the intensity of scattered light by smoke particles for fire alarm, photoelectric smoke detector is often interfered by non-fire smoke particles, such as water vapor, dust and other nuisance. Presently, most study on light scattering from smoke particles are focused on single aggregate. In fact, the smoke has a similar fractal structure. The number of primary particles approximately obeys log-normal distribution, and aggregates are in random orientation. Calculation of light scattering from particles must be averaged statistically in aggregate sizes and spatial orientations. Using the discrete-dipole approximation method, the scattering Muller matrices were computed for the randomly oriented smoke particles with a certain size distribution, as well as the dust particle. Both normalized Muller matrix elements were compared and analyzed. The results show that there are significant differences between the angle distributions of the normalized matrix elements F1 1 (θ) / F11(0), F2 2 (θ)/ F11(θ), F3 3 (θ) / F11(θ), F4 4 (θ) / F11(θ), F1 2 (θ) / F11(θ) and F3 4 (θ) / F11(θ) for smoke particles and dust particle. Matrix elements F2 2 (θ) / F11(θ) can be easily measured in experiment, so we can discriminate dust from smoke particles, using the difference of F2 2 (θ)/ F11(θ) between them. It could be an effective way to reduce false alarm rate of photoelectric smoke detectors.
引文
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[9]黄朝军,刘亚锋,吴振森.烟尘簇团粒子光学截面和散射矩阵的数值计算[J].物理学报, 2007, 56(7):4068-4074.
[10]类成新,张化福,刘汉法.随机分布烟尘簇团粒子缪勒矩阵的数值计算[J].物理学报, 2009, 58(10):7168-7175.
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[25] Kimura H . Light-scattering properties of fractal aggregates: numerical calculations by a superposition technique and the discrete-dipole approximation[J]. Quantitative Spectroscopy & Radiative Transfer, 2001, 70:581-594.
[26] Manickavasagam S, Menguc M P. Scattering Matrix Elements of Fractal-Like Soot Agglomerates[J]. Applied Optics 1997, 36(6):1337-1351.
[27]余其铮.辐射换热原理[M].哈尔滨:哈尔滨工业大学出版社, 2000.
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[32] Filippov A V, Zurita M, Rosner D E. Fractal-like Aggregates: Relation between Morphology and Physical Properties[J]. Journal of Colloid and Interface Science, 2000, 229:261–273.
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[37]Klusek C, Manickavasagam S, Mengü? M P. Compendium of scattering Matrix Element Profiles for Soot Agglomerates[J]. Journal of Quantitative Spectroscopy & Radiative Transfer, 2003, 79:839-859.
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[39] Xie Q Y, Zhang H P, Wan Y T, Zhang Y M, Qiao L F. Characteristics of light scattering by smoke particles based on spheroid models [J]. Journal of Quantitative Spectroscopy & Radiative Transfer, 2007, 107(1): 72–82.
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[2]王殊,窦征.火灾探测及其信号处理[M].武汉:华中理工大学出版社, 1998.
[3] Fleming J, Photoelectric vs. Ionization Detectors - A Review of the Literature [A]. Proceedings of Fire Suppression and Detection Research Application Symposium, Natl. Fire Protection Association, 1998, 18-59.
[4] Loephe M, Ryser P, Tompkin C, Wieser D. Optical Properties of Fire and Non-fire Aerosols [J]. Fire Safety Journal, 1997, 29(2-3):185–194.
[5] Wang A Z, Wang J, Yang Z L, et al. Research on Dust-proof Performance of Photoelectric Smoke Detector[C]. AUBE’04 13th International Conference on Automatic Fire Detection Proceedings. Germany: ZVD University Duisburg-Essen 2004:636–646.
[6]范维澄,孙金华,陆守香.火灾风险评估方法学[M].北京:科学出版社, 2004.
[7] Xu R L. Particle Characterization: Light Scattering Methods[M]. New York, Boston, Dordrecht, London, Moscow: Kluwer Academic Publishers, 2002.
[8] Xie Q Y, Zhang Y M, Yuan H Y, Zhao J H, Qiao L F,Jiang Y L. A spheroid model used to analyze effects of nonsphericityof smoke particles on light scattering patterns[J]. Journal of University of Science And Technology of China, 2006, 36(3): 320-327.
[9]黄朝军,刘亚锋,吴振森.烟尘簇团粒子光学截面和散射矩阵的数值计算[J].物理学报, 2007, 56(7):4068-4074.
[10]类成新,张化福,刘汉法.随机分布烟尘簇团粒子缪勒矩阵的数值计算[J].物理学报, 2009, 58(10):7168-7175.
[11] Keller A, Loepfe M, Nebiker P, Burtscher H. On-line Determination of the Optical Properties of Particles Produced by Test Fires[J]. Fire Safety Journal, 2006, 41(4):266–273.
[12]谢启源.火灾烟颗粒光散射模型的研究[D].合肥:中国科学技术大学, 2006.
[13]刘长盛,刘文保.大气辐射学[M].南京:南京大学出版社, 1990.
[14] Aden A L. Electromagnetic scattering from spheres with sizes comparable to the wavelength[J]. Apply Physics, 1951, 22:601-605.
[15]阮立明,齐宏,王圣刚.采用DDA方法分析非球形粒子辐射特性[J].哈尔滨工业大学学报, 2008, 40(3):413-418.
[16] Waterman P C. Matrix Methods in Potential Theory and Electromagnetic Scattering[J]. Journal of Applied Physics, 1979, 50(7):4550–4566.
[17] Mishchenko M I, Travis L D, Mackowski D W. T-Matrix Computations of Light Scattering by Nonspherical Particles: A Review[J]. Journal of Quantitative Spectroscopy and Radiative Transfer, 1996, 55(5):535–575.
[18] Mishchenko M I, Videen G, Babenko V A, et al. T-matrix Theory of Electromagnetic Scattering by Particles and Its Applications: A Comprehensive Reference Database[J]. Journal of Quantitative Spectroscopy and Radiative Transfer, 2004, 88(1-3):357–406.
[19]Devoe H. Optical Properties of Molecular Aggregate. I . Classical Model of Electronic Absorption and Refraction[J]. The Journal of Chemical Physics, 1964, 41(2):393–400.
[20] Purcell E M, Pennypacker C R. Scattering and Absorption of Light by Nonsphercial Dielectric Grains[J]. The Astrophysical Journal, 1973, 186:705–714.
[21] Draine B T, Flatau P J. Discrete-Dipole Approximation for Scattering Calculations[J]. Journal of the Optical Society of America A, 1994, 11(4):1491–1499.
[22]疏学明,方俊,邵荃,袁宏永.火灾烟雾颗粒的光学散射特性研究[J].中国工程科学, 2005, 7(1):45-49.
[23]赵建华,袁宏永,范维澄,陈涛.用消光系数比表征火灾烟雾的分类特征[J].物理学报, 2002, 51(3):700-704.
[24] Lumme K, Rahola J, Hovenie J W. Light scattering by dense clusters of spheres [J]. ICARUS 1997, 126(2):455-469.
[25] Kimura H . Light-scattering properties of fractal aggregates: numerical calculations by a superposition technique and the discrete-dipole approximation[J]. Quantitative Spectroscopy & Radiative Transfer, 2001, 70:581-594.
[26] Manickavasagam S, Menguc M P. Scattering Matrix Elements of Fractal-Like Soot Agglomerates[J]. Applied Optics 1997, 36(6):1337-1351.
[27]余其铮.辐射换热原理[M].哈尔滨:哈尔滨工业大学出版社, 2000.
[28] Wauben W M, Dehaan J F, Hovenier J W, Influence of Particle shape on the polarized radiation in planetary atmospheres[J]. JQSRT, 1993, 50(3):237-246.
[29] Wriedt T . A review of elastic light scattering theories[J]. Particle and particle Systems Characterization, 1998(15):67-74.
[30] Yang P, Liou K N , Mishchenko M I, et al. Efficient finite-difference time-domain scheme for light scattering by dielectric particles: application to aerosols[J]. Applied optics, 2000, 39(21):3727-3737.
[31] Kalashnikova O V, Sokolik I N. Modeling the radiative properties of nonspherical soil-derived mineral aerosols[J]. JQSRT, 2004, 87:137-166.
[32] Filippov A V, Zurita M, Rosner D E. Fractal-like Aggregates: Relation between Morphology and Physical Properties[J]. Journal of Colloid and Interface Science, 2000, 229:261–273.
[33]廖延彪.偏振光学[M].北京:科学出版社, 2003.
[34] R.M.A.阿查姆, N.M.罢夏拉著,梁明基等译.椭圆偏振测量术和偏振光[M].北京:科学出版社, 1986.
[35]乔利锋.火灾烟颗粒光散射模型的研究[D].合肥:中国科学技术大学, 2008.
[36]乔利锋,张永明,谢启源,方俊,王进军.火灾烟颗粒的分形结构形状模拟与光散射计算[J].物理学报, 2007, 56(11): 6736-6741.
[37]Klusek C, Manickavasagam S, Mengü? M P. Compendium of scattering Matrix Element Profiles for Soot Agglomerates[J]. Journal of Quantitative Spectroscopy & Radiative Transfer, 2003, 79:839-859.
[38] Ahrens M. Home Smoke Alarms -the Data as Context for Decision[R]. Batterymarch Park, Quincy, MA: National Fire Protection Association, 2008.
[39] Xie Q Y, Zhang H P, Wan Y T, Zhang Y M, Qiao L F. Characteristics of light scattering by smoke particles based on spheroid models [J]. Journal of Quantitative Spectroscopy & Radiative Transfer, 2007, 107(1): 72–82.
[40]疏学明,郑魁,袁宏永,姚斌.火灾标准火烟雾颗粒测量及粒径尺度分布函数研究[J].中国工程科学, 2005,7(8):51-55.
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