The influence of hydrocyclone eccentricity on the outlet flow field was studied by experimental method when the same hydrocyclone was matched with different sizes of outlet limiting region. The results showed that when the ratio of the boundary size (L) to the characteristic size (D) of the hydrocyclone was less than a certain value (L/D=33)

there was an attachment point between the jet at the outlet of the hydrocyclone and the wall of the hydrocyclone. The outlet flow field changed from contraction type to expansion type; for the contractile flow field

the eccentricity of the hydrocyclone had a great influence on the outlet flow field

especially the radial velocity field

the minimum value changed from -4 m/s to 1 m/s; while for the expanding outlet flow field

the eccentricity of the hydrocyclone had little effect

for example

the minimum axial velocity was around -44 m/s

and the minimum radial velocity was -1 m/s. In order to reduce the influence of hydrocyclone eccentricity

the outlet flow field can be expanded by increasing the combined swirl number and reducing the ratio of the outlet limiting region to the characteristic dimension of the hydrocyclone.