EXPERIMENTAL STUDY OF EFFECT OF SOLID PARTICLES ON TURBULENCE OF GAS IN TWO PHASE FLOWS

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EXPERIMENTAL STUDY OF EFFECT OF SOLID PARTICLES
ON TURBULENCE OF GAS IN TWO - PHASE FLOWS

• Medhat Hussainov
• Laboratory of Multiphase Media PhysicsTallinn
  University of Technology
• Estonia

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Introduction

• Dispersion of solid particles in turbulence
  flows is of importance in many nature and
  industrial processes. The transport of pollutants
  in the atmosphere and oceans, pulverized coal
  particles in furnaces and slurries in pipes are
  typical examples of these flows.
• It is well known that particles affect the
  parameters of turbulence. The influence of the
  particle on the turbulence intensity is of the
  most importance.

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OUTLOOK

• Overview of the criteria of particle influence on
  turbulence
• The experimental results on two-phase
  grid-generated turbulence
• New criterion parameter of particle influence on
  turbulence
• Conclusions

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Criteria of the effect of particle on the
turbulence intensity
Gore and Crowe (1989)
Particle size
Decreasing the turbulence intensity
Integral length scale
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Criteria of the effect of particle on the
turbulence intensity
G. Hetsroni (1989)
- Increasing the turbulence intensity
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Criteria of the effect of particle on the
turbulence intensity
S. Elghobashi (1991)
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• The main objectiveof our investigations is to
  clarify the dependence of change in the turbulent
  intensity on the phases velocity slip.
• The distinctive featureof our experiments was to
  provide of various velocity slip for the same
  particles without changing of flow parameters.

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Experimental facility
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Experimental conditions
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The decay curves behind different grids
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Turbulence intensity
vs the flow mass loading at the location X450 mm
vs the velocity slip at the location X365 mm
Dash lines denote the turbulence intensity for
various grids in the single-phase flow.
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The change of the turbulence intensity by
particles vs StE
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The change of the turbulence intensity by
particles
vs ReL for different values of Rep
vs Rep at the location X365 mm
() - Hussainov, M., Kartushinsky, A., Kohnen,
G., Sommerfeld, M. 1999.
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The change of the turbulence intensity by
particles vs Rep/ReL
flow mass loading æ0.14 kg dust/kg air
() - Hussainov, M., Kartushinsky, A., Kohnen,
G., Sommerfeld, M. 1999.
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The change of the turbulence intensity by
particles vs Rep/ReL
flow mass loading æ0.14 kg/kg
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Conclusions

• The turbulence intensity in dependence on the
  flow mass loading is linear up to concentration 1
  kg/kg
• The turbulence attenuation increases with
  decrease in Stokes number in the case of Stokes
  number gt 1
• The ratio between particle Reynolds number Rep
  and turbulence Reynolds number ReL is proposed as
  criterion for considering the combined influence
  of the parameters of the dispersed phase and the
  initial single-phase flow on the turbulence
  intensity of carrier phase
• The value of the ratio Rep/ReL of 0.4 is the
  limit for our experiments and that value
  determines the character of the particle
  influence on the turbulence at Rep/ReL lt 0.4,
  the turbulence intensity is attenuated and at
  Rep/ReL gt 0.4, it is enhanced.