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Characterization of the PVC phenomena in the exhaust of a cyclone dust separator

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Abstract

A laboratory scale cyclone dust separator with swirl numbers varying from 3.043 to 1.790 was used to examine the effects of different downstream pipework configurations, flowrates and swirl numbers upon the size, shape, and position of the precessing vortex core. Also examined was the effect the precessing vortex core had on the reverse flow zone, and the relationship between the two.

It was concluded that the reverse flow zone displaced the central vortex core to create the precessing vortex core. The reverse flow zone would then provide feedback for the precessing vortex core, and precess around the central axis about 30 degrees behind the precessing vortex core (P.V.C).

The size and position of the P.V.C was effected by changes in Reynolds number, and any additions of downstream systems to the cyclone would also affect the strength of the P.V.C.

The P.V.C would squeeze and accelerate the flow through a constriction set up between the outer limits of the core and of the exit diameter wall.

Spiral engulfment vortices were produced on the outside of the flow and served as the initial entrainment mechanism for external flow.

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Abbreviations

A t :

tangential inlet area (m2)

b :

length of internal tangential inlet (m)

c :

length of top cylindrical body of cyclone (m)

D :

cyclone exhaust diameter (m)

Di :

internal pipework diameter (m)

De :

external pipework diameter (m)

G φ :

axial flux of angular momentum (kg m2s−2)

G x :

axial flux of axial momentum (kg m s−2)

h :

length of internal section of the vortex finder (m)

l :

length of main body of cyclone (m)

L :

length of pipework (m)

M i :

input mass flow of air

Q :

flowrate (m3/s)

R :

radius (m)

Re :

Reynolds number, defined as 4Q/ (πDv)

R b :

radius of cone base of cyclone (m)

R x :

radius of exhaust (m)

R 0 :

radius of cyclone main body (m)

S :

swirl number, defined as {G φ/(G xRx)}

Sg :

geometric swirl number, defined as {πR xR0/At}

p :

pressure (N/m2)

r :

radial position (m)

u :

time-mean axial velocity (m/s)

v :

time-mean radial velocity (m/s)

w :

time-mean swirl velocity (m/s)

ϱ :

density (kg/m3)

gq :

cyclone cone angle (degree)

υ :

kinematic viscosity (m2/s)

λ :

wavelength (m)

α :

vortex exponent

′:

fluctuating

—:

average

L.D.A:

Laser Doppler Anemometry

PCOV:

Precessional Centre of the Vortex

P.V.C:

Precessing Vortex Core

Q.F.V:

Quantitative Flow Visualisation

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Authors and Affiliations

  1. Division of Mechanical Engineering and Energy Studies, University of Wales College of Cardiff, PO Box 917, CF2 1XH, Cardiff

    P. A. Yazdabadi & N. Syred

Authors
  1. P. A. Yazdabadi
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  2. A. J. Griffiths
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  3. N. Syred
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Additional information

The authors wish to acknowledge the financial assistance provided by British Petroleum for this research. P. Yazdabadi acknowledges the award of a SERC Total Technology studentship.

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Yazdabadi, P.A., Griffiths, A.J. & Syred, N. Characterization of the PVC phenomena in the exhaust of a cyclone dust separator. Experiments in Fluids 17, 84–95 (1994). https://doi.org/10.1007/BF02412807

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