Abstract： In order to research the effect of axial clearance on hydraulic performance of a stock pump,3D turbulent numerical simulation was carried out for a semi-open centrifugal stock pump with three kinds of axial clearances by the computational fluid dynamics software Fluent under the conditions of 0.7 to 1.3 times of design flow rate.The simulations were conducted on mediums of clean water and pulp fiber suspensions,respectively,and in which the standard k-ε turbulent model and SIMPLEC algorithm were adopted.The simulation results show that the head and efficiency both decrease with the increasing of clearance when taking clean water as media.The velocity distribution in impeller and clearance is in accordance with that of clean water when taking pulp fiber suspensions as medium.The method of properly increasing the blade outlet angle is proposed to reduce the low-velocity regions,while the latter causes flow distortion at the condition that the volume fraction of pulp fiber suspensions is of 2%.When the rigidity effect is of no more action due to the clearance increases,the overall performance of the pump would be decreased.Due to the impact of axial clearance,the pressure and velocity between the suction side and pressure side of blades are of great variation,and the transmission capacity will increase for a small axial clearance and a certain volume fraction of pulp fiber.Compared with test data,it shows that the semi-open pulp stock pump will work well when tip clearance is 1.0 mm,and the numerical simulated results agree with that of the tested.
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