scattering matrix analysis of fire and non-fire aerosols
TRANSCRIPT
Scattering Matrix Analysis of Fire and
Non-fire Aerosols
Qixing Zhang, Yongming ZhangState Key Laboratory of Fire Science,
University of Science & Technology of China
Introduction of SKLFS@USTC
University of Science and Technology of China (USTC)
Located in Hefei, Anhui Province
About 15500 students (2016), 1800 faculty members
Member of C9 League of Top Chinese Universities
Established the first graduate school in China
Leader in fields like quantum manipulation, nanotechnology, high temperature superconductivity, speech processing, fire science
Introduction of SKLFS@USTC
State Key Laboratory of Fire Science (SKLFS)
National research institution in the field of fire science
One of the world’s largest organizations dedicated to fire research and education.
Introduction of SKLFS@USTC
State Key Laboratory of Fire Science (SKLFS)
Fire detection Section
Past Research Activities: Development of fire detection system in large volume space (with height greater than 12 m)
Two Channel VideoSurveillance Systems
Introduction of SKLFS@USTC
State Key Laboratory of Fire Science (SKLFS)
Fire detection Section
Past Research Activities: Development of fire detection system in large volume space
Light section smoke detection system
Introduction of SKLFS@USTC
State Key Laboratory of Fire Science (SKLFS)
Fire detection section
Past Research Activities: Development of fire detection technology in large volume space
Detection and automatic suppression system
Introduction of SKLFS@USTC
State Key Laboratory of Fire Science (SKLFS)
Fire detection section
Ongoing Research Activities: Low false alarm rate smoke detection (http://smoke.ustc.edu.cn)
Motivation of the scattering matrix study
Exploring the possibility of polarized light scattering for reliable optical smoke detector
Experimental measurement
Measurement principle
inc
inc
inc
inc
VUQI
)()()()(
θθθθ
sca
sca
sca
sca
VUQI
θ
Scattering light
Incident light
• Light beam can be represented by four Stokes parameters
VUQI total intensity
± 90o polarization± 45o polarizationcircular polarization
Experimental measurement
Scattering matrix (Mueller matrix)
The transformation from incident light to scattering light can be represented by Mueller matrix:
incsca F II ⋅= )()( θθ Scattering matrixMeasurement andModeling
𝐹𝐹 𝜃𝜃 =
)𝐹𝐹11(𝜃𝜃 )𝐹𝐹12(𝜃𝜃 0 0)𝐹𝐹12(𝜃𝜃 )𝐹𝐹22(𝜃𝜃 0 0
0 0 )𝐹𝐹33(𝜃𝜃 )𝐹𝐹34(𝜃𝜃0 0 )−𝐹𝐹34(𝜃𝜃 )𝐹𝐹44(𝜃𝜃
𝐹𝐹11 𝜃𝜃 (well-known as phase function) reflects the intensity from incident light to scattering
𝐹𝐹22 𝜃𝜃 can be used to evaluate the total nonsphericity
−𝐹𝐹12 𝜃𝜃 /𝐹𝐹11 𝜃𝜃 iscommonly called the degreeof linear polarization
Experimental measurement
Experimental setup
FUNCTION GE NE RATO R
Output100.00kHz
LaserGlan polarizer EO Modulator
Industrial computer
lock-in amplifier Pre amplifier
Pre amplifier
Sterpper motor Monitor PMT
Detector PMT
Rotation arm
Data acquisition board
Beam stop
Function generator
Beam spilitter
Photo diode
Polarizer1/4λ plate
Measurement: 16 elementsof Mueller scattering matrixScattering angle range: 5°~160°
Laser source: diode laserwith wavelength of 532nm
Experimental measurement
Generation of fire and non-fire aerosols
Flaming heptane Smoldering cotton
Generator: ATM226Water droplet
Generator: RG1000Dust
Home-made ChamberTest fire
Experimental measurement
Flaming n-heptane and smoldering cotton fire
Mie theory is applicable for smoke particles of smoldering cotton fire, but not applicable for flaming n-heptane fire
Experimental measurement Scattering matrices of smokes particles different
fuels and different combustion conditions
scotton swood fheptane fpolyu fwood0
20
40
60
80
100
120
140
160
180 Smax11 /Smin
11
scotton swood fheptane fpolyu fwood0.0
0.2
0.4
0.6
0.8
1.0
1.2 Min of S22/S11(a)
(b)
(c)
(d)
(e)
scotton: smouldering cotton swood: smouldering wood fwood: flaming wood fheptane: flaming n-heptanefpolyu: flaming polyurethane.
Experimental measurement
The retrieval of the size distribution and refractive index of spherical particles
Four parameters: n, k, σ, d
Experimental data SmeasureCalculation data Scal
Calculation of measure calS S∆ = − ∑
Minimization of via optimization technique
Retrieval of size distribution and refractive index information
∆
0 20 40 60 80 100 120 140 160 180 200
-0.6
-0.4
-0.2
0.0
0.2
0.4
S 12/S
11
Angle
fit with lognormal distribution (σ=1.5, d=2.56µm)measurement data of water droplets
Experimental measurement
The retrieval of the size distribution and refractive index of spherical particles
SmokeSmouldering
cottonSmouldering
wood
Measurement S11 S12 S34 S44 S11 S12 S34 S44
GMD 170nm 469nm
GSD 2.335 1.561
Refractive Index 1.49+0.01i 1.51+0.005i
Summary of experimental measurement
Distinguish between flaming fire, smoldering fire, dust
Smoldering fire can be well described by Lorenz Mie theory, and dust and flaming fire can not
Only measured test fire, real fire is complicated in combustion temperature, fuel? Representative?
Light scattering modelling
Microstructure: Size, Refractive index, Morphology
Modelling light scattering, and verified by experimental results
Then we can investigate numerically with varied parameters to reflect the complicated real circumstance
Morphology by SEM
Smouldering cotton fire
Smouldering wood fire Flaming polyurethane fire
Flaming n-heptane fire
Light Scattering Modelling method
T-matrix Mie DDA: Discrete Dipole Approximation
Fractal Aggregates Spherical RandomMorphology:
Size: <1um <1um >1um
0.56 0.001-0.1 0k value:
Flaming fire soot Smoldering fire DustParticle:
Discussion about cooking aerosol
Cooking Aerosol Morphology: spherical, described by Mie theory Size: <1um Refractive index: m=n+ki with k (0.01-0.1)
Cooking aerosol and smoldering aerosol Similar in all three aspects: morphology, size,
absorption, difficult to distinguish Multi-criteria sensor? Time-dependent
information?
Discussion about cooking aerosol
Rawad Saleh; Zezhen Cheng; Khairallah Atwi; Environ. Sci. Technol. Lett. 5, 508-513.
Cooking aerosol
Cooking Aerosol: lots of PAHs Assume to be more absorptive than smoldering particles
Summary
Measured scattering matrices as functions of the scattering angle for smoke particles from five test fires and several non-fire aerosols were presented.
Distinguish between flaming fire, smoldering fire, and dust can be achieved using scattering matrices
Scattering of smoke from smoldering fires can be well described by Lorenz-Mie theory; Particle size distribution and refractive index of smoke from two smoldering fires were inferred
We think cooking aerosol is similar to smoldering fire aerosol in size, refractive index, and morphology.
Discussion about cooking aerosol Measurement results from literature
Degree of polarization, same as −𝐹𝐹12 𝜃𝜃 /𝐹𝐹11 𝜃𝜃
M. Loepfe et al; Fire Safety Journal. Vol. 29, 1997. pp185-194
Discussion about cooking aerosol
Particle size distribution variationSmoldering cotton Smoldering wood
D. Tian et al; Environmental Science, 2012. vol 33, No. 6, (In Chinese)
Western cooking Chinese pot cooking