7. Conclusion
The effect of free air inflow on particle separation performance
at the upper part of the gas-cyclone was examined by use of experimental
and CFD studies and the following conclusions are
obtained.
(1) The 50% cut size with the free air inflow cyclone is smaller
than that without the free air inflow cyclone under the same
pressure drop condition.
(2) The optimum flow ratio defined by the free air inflow rate to
main flow rate is approximately 0.4. The cyclone with four
slit inlets of free air shows higher particle separation performance
compared to other types.
(3) The free air inflow rate increases with the increase of slits,
but the main flow rate decreases under the constant pressure
drop condition. For a flow ratio greater than 0.4, the
50% cut size again increases due to the decrease of the main
flow rate.
(4) From the simulation results, the rotational and downward
flow velocity in the upper cylindrical part with the free air
inflow cyclone is greater than that without the free air
inflow cyclone.
(5) Particle trajectory simulation indicated that particles entering
into the cyclone tend to move to the circular wall region
smoothly in the case of the free air inflow cyclone. The reason
for this phenomena is due to the increased rotational
and downward fluid velocity.