Design of Novel Asymmetric Variable-Clearance Spiral Tooth Profile and Experimental Investigation of Internal Flow Characteristics

Existing asymmetric vortex structures suffer from issues such as pressure imbalance in the working chamber and pressure fluctuations at the exhaust port. Against this backdrop, research on vortex vacuum pump profile lines was conducted. By applying composite profile lines from symmetric vortex profiles to asymmetric vortex profiles, a novel asymmetric vortex profile was constructed. An asymmetric arc modification method is proposed to resolve meshing challenges. The curve equation for an asymmetric variable-clearance scroll tooth profile is designed. To ensure efficient and stable operation of the scroll mechanism, the pressure imbalance between the two working chambers can be mitigated through a gradient-varying meshing clearance. The fundamental parameters of the asymmetric vortex vacuum pump were determined, the volumes and internal volume ratios of each chamber were calculated, and the variation patterns of the working chamber area were analyzed. Concurrently, the influence of the offset coefficient on backlash was examined to achieve performance optimization. This study employs a novel asymmetric profile design incorporating an offset coefficient j to form a variable clearance meshing structure, significantly improving the flow field performance within the vortex vacuum pump. Simulation results demonstrate that this design increases the compression chamber pressure balance ratio from 1:0.767 to 1:0.992. When j=0.2, the pressure pulsation rate decreases by 38.5%, and the flow pulsation rate decreases by 18.2%. Experimental validation demonstrates that under a 20 kPa pressure differential, the new pump achieves an average flow rate of 10.5 m³/h with a pressure pulsation range of only 0−1.9 kPa, outperforming conventional pumps and fully showcasing its advantages in suppressing pulsation and enhancing flow stability.