The gas phase flow fields in cyclone separators in the same size are simulated with different flow parameters.The diameter of the cyclone was 300 mm.The inlet velocities range from 0.5 to 30 m·s-1

the gas temperatures range from 293 to 1273 K

and the pressures in the cyclone separator are from 0.1 to 6.5 MPa

which are the flow parameters usually used in the industry.Based on the simulation results

the effect of flow parameters on the similarity of dimensionless velocity is investigated.The similarity criterion of flow field in the model and prototype is also analyzed.The results show that the flow fields are similar for different flow parameters

but the dimensionless velocities are different.When the inlet velocity is higher than 20 m·s-1

or the pressure is higher than 3.0 MPa

the Euler number approaches a constant. It is not affected by Reynolds number

so the flow field keeps approximate similarity.When the temperature is higher than 1000 K

the influence of Reynolds number on Euler number is very weak

so that the flow field also keeps self-similarity.Moreover

the mechanics of the self-similarity of flow field is discussed in view of the energy losses and the relationship between Euler and Reynolds number.