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Dual optical fibre measurements of the particle concentration in gas/solid flows

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Abstract

Numerous optical probe designs to measure particle volume fraction have been proposed in the literature. Unfortunately, almost all of them suffer from an ill-defined measurement volume, poor sensitivity or require frequent and tedious calibration. We propose an improvement in the design of a dual optical fibre probe. It has a well-defined measuring volume and a near-linear sensitivity. A general calibration theory for optical fibre probes is also proposed. The design and the theory have been tested in a simple experimental set-up with encouraging results.

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Abbreviations

a :

probe glass thickness (m)

b :

glare diameter (m)

d p :

particle diameter (m)

dS :

surface element (m2)

D :

optical fibre diameter (m)

f :

maximum packing signal, function of distance to the probe (V)

g :

radial distribution, function of particle volume fraction

h :

probe sensitivity, function of distance to the probe (V)

I :

intensity of light reflected off a particle (V)

l :

light ray length (m)

N :

number of elements

n p :

number of particles

p :

penetration depth of light distribution, function of distance and particle volume fraction (m−1)

q :

glare correction, function of probe geometry and particle size

r :

distance to the probe surface (m)

r ′:

distance from the probe surface to the first particle in a given direction ( θ, φ) in a given suspension (m)

R :

probe receptivity to light, function of angle of incidence and distance to particle

S :

probe response signal (V)

S 0 :

probe response at zero volume fraction of particles (V)

S dense :

probe response at maximum packing of particles (V)

V cyl :

cylinder volume (m3)

V p :

particle volume (m3)

z :

independent length variable (m)

α p :

volume fraction of particles

α p,max :

volume fraction of particles at maximum packing

β :

angle between incident and receiving optical fibre (rad)

δ :

exponent

γ :

exponent

θ :

altitude angle in spherical coordinates (rad)

φ :

azimuthal angle in spherical coordinates (rad)

λ :

mean free path of light (m)

σ :

dimensionless probe response signal

ξ :

dimensionless reciprocal mean free path of light

η :

dimensionless distance to probe surface

ζ :

independent dimensionless length

~:

instantaneous value

<>:

expectancy value

References

  • Almstedt AE (1985) Measurement of bubble behaviour in a pressurized fluidized bed burning coal using capacitance probes, part 2. In: Proc 8th Int FBC Conf, Houston, USA, pp 89–98

  • Bellino I, Bergougnoux L, Misguich-Ripault J, Firpo JL (2000) Particle size effects on an optical fiber sensor response. Powder Technol 115:68–74

    Article  Google Scholar 

  • Hartge EU, Li Y, Werther J (1986) Analysis of the local structure of the two phase flow in a fast fluidized bed. In: Basu P (ed) Circulating fluidized bed technology. Pergamon, Oxford, pp 153–160

  • Johnsson H, Johnsson F (2001) Measurements of local solids volume-fraction in fluidized bed boilers. Powder Technol 115:13–26

    Article  CAS  Google Scholar 

  • Krohn DA (1986) In: DePaula RP, Udd E (eds) Fiber optic and laser sensors IV, SPIE vol 718, p 2

  • Lischer DJ, Louge MY (1992) Optical fiber measurements of particle concentration in dense suspensions: calibration and simulation. Appl Opt 31:5106–5113

    CAS  Google Scholar 

  • Maxwell JC (1892) Electricity and magnetism. Clarendon, Oxford

  • Olowson PA, Almstedt AE (1990) Influence of pressure and fluidization velocity on the bubble behaviour and gas flow distribution in a fluidized bed. Chem Eng Sci 45:1733–1741

    Article  CAS  Google Scholar 

  • Reh L, Li J (1991) Measurement of voidage in fluidized beds by optical probes. In: Basu P (ed) Circulating fluidized bed technology, vol 3. Pergamon, New York

  • Rensner D, Werther J (1991) Modeling and application of a fiber optical measuring system for higher concentrated multiphase flow. In: Proc 4th int conf laser anemometry, ASME, Cleveland, pp 753–761

  • Tontrup C, Gruy F (2000) Light backscattering by fine nonabsorbing suspended particles. Powder Technol 107:1–12

    Article  CAS  Google Scholar 

  • van Wachem BGM, Shouten JC, van den Bleek CM, Krishna R, Sinclair JL (2001) Comparative analysis of CFD models of dense gas–solid systems. AIChE J 47:1035–1051

    CAS  Google Scholar 

  • Werther J (1997) Measurement techniques in fluidized beds. In: Proc 4th world conference on experimental heat transfer, fluid-dynamics and thermodynamics, Brussels, 2–6 June 1997

  • Werther J, Hage B, Rudnick C (1996) A comparison of laser Doppler and single-fibre reflection probes for the measurement of the velocity of solids in a gas-solid circulating fluidized bed. Chem Eng Proc 35:381–391

    Article  CAS  Google Scholar 

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Acknowledgements

The authors wish to thank SCA Hygiene Products, AstraZeneca R&D Mölndal and the SSF programme Multiphase Flow for their financial support. We also thank Lars Jernqvist and Uno Hansson for building the probe and the electronics.

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Authors and Affiliations

  1. Thermo and Fluid Dynamics, Chalmers University of Technology, S-412 96, Göteborg, Sweden

    R. Rundqvist, A. Magnusson, B. G. M. van Wachem & A. E. Almstedt

Authors
  1. R. Rundqvist
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  2. A. Magnusson
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  3. B. G. M. van Wachem
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  4. A. E. Almstedt
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Correspondence to R. Rundqvist.

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Rundqvist, R., Magnusson, A., van Wachem, B.G.M. et al. Dual optical fibre measurements of the particle concentration in gas/solid flows. Exp Fluids 35, 572–579 (2003). https://doi.org/10.1007/s00348-003-0703-0

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  • DOI: https://doi.org/10.1007/s00348-003-0703-0

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