Due to the complexity of working conditions and physical fields,the clearance flow field of the magnetic fluid sealing device for the main shaft of hydraulic turbine has always been a difficult point in the research of magnetic fluid seal.To study the flow characteristics of magnetic fluid in the clearance of the magnetic fluid sealing device for the main shaft of a hydraulic turbine,a numerical model of the flow field in the seal clearance of the main shaft was established and verified through experiments.The influence of the seal clearance,the width of the pole tooth,the height of the pole tooth and the width of the pole tooth slot on the flow of the magnetic fluid was studied by numerical calculation.The results show that the magnetic fluid near the pole tooth is not affected by the structural parameters and basically remains stationary.When the seal clearance is less than 0.6 mm,the magnetic fluid in the clearance basically does not flow.When the seal clearance exceeds 0.6 mm,the magnetic fluid near the pole slot and permanent magnet increases with the increase of the seal clearance,and the speed increases linearly.The flow of magnetic fluid near the pole tooth slot and permanent magnet decreases with the increase of the width of the pole tooth,and the velocity decreases linearly at first,decreases sharply at the width of the pole tooth from 3.0 mm to 3.5 mm,and finally tends to be stable.With the gradual increase of the height of the pole teeth and the width of the pole tooth slot,the magnetic fluid flow near the pole teeth and the permanent magnet will weaken.The magnetic fluid velocity near the pole teeth and slots will decrease sharply at the the height of the pole tooth from 1.0 mm to 3.5 mm and the width of the pole teeth from 3.0 mm to 12 mm and finally become stable,while the magnetic fluid velocity near the permanent magnet has been decreasing linearly.