Numerical Simulation Of The Gas Flow Field Under Viscous Flow Condition Inside The Spiral Grooved Drag Structure

The spiral grooved drag structure is widely used for its simple structure and can achieve a high compression ratio. Determined by its own characteristics, the pumping performance of the spiral grooved drag structure is closely related to its geometry. Many researchers have focused on optimizing spiral grooved drag structure to improve its pumping efficiency.The gas flow condition inside the spiral grooved drag structure changes from turbulent flow to molecular flow during pumping process. Under different gas flow state, different researching approaches must be used. This paper uses ANSYS CFX to study the gas flow field under viscous flow state in the spiral grooved drag structure.First, this paper studied the gas flow field in the spiral grooved drag structure under constant compression ratio. The simulation results show that the product of the average pressure and characteristic length of the flow channel is quite linear in the flow channel. The average and normalized pressure increases exponentially in the extraction channel. Vortices are generated in the extraction channel, and become larger with the increasing pressure.How geometric parameters of the spiral grooved drag structure affect its pumping performance under viscous flow was also studied. The simulation results show that the pumping speed increases with the increase of the rotor outer diameter; reduces with the increase of the inner diameter at the inlet end and the inner diameter at the outlet end; first increases and then reduces with the increase of the rotor height and the increase of the pitch, and there is a maximum. In the range of subsonic, the pumping speed increases with the increase of the rotor speed. When the number of rotor blades is greater than or equal to three, the pumping speed reduces with the increase of the number of leaves.