Abstract:The flow field and fluidinduced force between the rotor and the stator of the labyrinth seal are directly affected the vibration and stability of the rotor.To understand the flow field and fluidinduced force characteristics of the labyrinth seal,the rotary straightthrough labyrinth gas seal were selected as the research object,the effects of the inlet length on the leakage,flow field and fluidinduced force of the rotary straightthrough labyrinth gas seal were investigated by using the steadyCFD analysis methods.The the leakage flow rates,velocity streamlines,total pressure distributions,pressure forces,and viscous forces of the labyrinth gas seal for different inlet lengths without and with preswirl were computed.The results show that with the increasing of inlet length,the leakage flow rates is firstly increased and then decreased,and the pressure forces and viscous forces are firstly increased and then decreased rapidly.The inlet length influences the flow field of the straightthrough labyrinth gas seal,and there is a specific inlet length to maximize the pressure forces and viscous forces on the surface of the rotor.The preswirl results in the decrease of the leakage flow rates,the pressure forces and viscous forces.