scattering matrix analysis of fire and non-fire aerosols

Scattering Matrix Analysis of Fire and

Non-fire Aerosols

Qixing Zhang, Yongming ZhangState Key Laboratory of Fire Science,

University of Science & Technology of China

Outline

Introduction to SKLFS@USTC

Motivation

Experimental measurement

Modelling

Summary

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


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.



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



Fire detection Section

Past Research Activities: Development of fire detection system in large volume space

Light section smoke detection system



Fire detection section

Past Research Activities: Development of fire detection technology in large volume space

Detection and automatic suppression system



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


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


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 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


Generation of fire and non-fire aerosols

Flaming heptane Smoldering cotton

Generator: ATM226Water droplet

Generator: RG1000Dust

Home-made ChamberTest fire


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


Mie fit of scattering matrices of Flaming n-heptane

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.


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


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


Non-fire aerosols: Dust particles


Non-fire aerosols: Comparison between dust, water droplet, and smoke

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

Morphology by SEM

Fly ash Fly ash

Dust Dust

Morphology reconstruction

Elemental analysis

CHNS Element Composition

Flaming wood 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?


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.

Qixing Zhang, SKLFS,

Email: [email protected]

http://smoke.ustc.edu.cn

Thank you for your attention

mailto:[email protected]

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 Sensitivity study


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


Sensitivity study

scattering matrix analysis of fire and non-fire aerosols

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