Enhanced rotordynamic performance under various structural arrangements of hole diaphragm labyrinth seal

Abstract

In this study, we study the influence of five drilling hole arrangements on the rotordynamic and leakage performance of hole diaphragm labyrinth seal (HDLS) type seals with precise CFD analysis. Key findings reveal that hole distance significantly affects direct and cross-coupled stiffness, thereby impacting stability and leakage. Notably, the smallest hole in rectangle four holes(RF)-HDLS does not yield the minimum leakage. Vortex structure analysis, employing the Q-criterion, elucidate horizontal two holes(HT)-HDLS's superior leakage reduction owing to enhanced turbulence eddy dissipation. Seals with larger hole diameters, down single hole(DS)-HDLS and up single hole(US)-HDLS, demonstrate stable rotordynamic performance, with DS-HDLS exhibiting a notable 106.3% improvement in cross-coupled stiffness. In contrast, seals with holes positioned farther away, DS-HDLS, US-HDLS and vertical two holes(VT)-HDLS, experienced increased leakage with whirl frequency. HT-HDLS and RF-HDLS displayed a decrease, attributed to the stronger centrifugal effect. Comparing to center single hole(CS)-HDLS, VT-HDLS and US-HDLS achieved a significant 159.3% direct stiffness improvement and 432.7% reduction in cross-coupled stiffness. Despite a maximum 4.2% leakage increase, this substantial enhancement in rotor stability should not be overlooked. Moreover, all seals exhibited lower leakage rates than the traditional labyrinth seal.

Keywords

• Hole diaphragm
• Labyrinth seal
• Rotordynamic characteristics
• Leakage performance