Spiral flow induced destabilizing force analysis and its reduction with a novel helix-comb gas seal

The circumferential spiral flow is the main cause of destabilizing tangential force. To control the circumferential spiral flow, the helix-comb seal is presented in this study. With the guiding role of helical teeth, the negative circumferential spiral flow can be generated. It can significantly suppress the circumferential flow within the seal gap. A 3D computational fluid dynamics method is employed to investigate the performance of helix-comb seal. From the parameter analysis, it is found that the minimum tangential force can be obtained with the helix angle of 15 deg. Tangential force decreases with the increasing helical tooth number and helical tooth height. Considering the rubbing between the helical teeth and rotor, helical tooth height should be slightly smaller than the height of its adjacent comb tooth. Comparisons are conducted between the labyrinth seal (with and without swirl brakes) and helix-comb seal. Results reveal that the three seals have a comparable sealing performance. Considering the destabilizing force, the helix-comb seal has the lowest tangential force and the best stability. The helix-comb seal provides a novel method to control self-excited vibration. (C) 2020 Elsevier Masson SAS. All rights reserved.