Research on novel labyrinth type seals combined with diaphragms and hole diaphragms: Leakage and rotordynamic coefficients

Two new combined seals, the diaphragm labyrinth seal with partial holes (DLSH) and the hole diaphragm-diaphragm labyrinth seal (HDDLS) are proposed in this paper. The computational fluid dynamics (CFD) method was used for circumferentially discontinuous seal calculations. An experimental system under static operation conditions was established. The results show effective damping of the DLSH and HDDLS significantly influenced by preswirl, whereas such influence is weakened on effective stiffness dependence of DLSH. The calculation results show that leakage of HDDLS can be reduced compared to DLSH, even though the only difference between these two seals is the installation direction. The experiments show that HDDLS can reduce 4.69 % leakage than DLSH's at 250 kPa inlet-to-outlet pressure drop. And the corresponding throttling ability studies of each seal blade show that existence of hole-diaphragms, which are near the inlet boundary, will reform pressure drop contribution of each blades in axial direction. Axial pressure drops of DLSH are balanced and reduced in HDDLS. Further comparisons on DLSH, HDDLS and their components, diaphragm labyrinth seal (DLS) and hole diaphragm labyrinth seal (HDLS), verify the advantageously initial design ideas of combing hole-diaphragm and diaphragm.