A new rotating test facility for the experimental characterisation of shaft seals

Abstract

Turbomachinery shaft seals suffer from rubs caused by thermal growth, assembly misalignment and rotor dynamic vibration at engine start-up and shut-down. Rubs are detrimental to performance, leading to a decrease in overall efficiency and costly corrective maintenance. In recent years, compliant seals have been developed, allowing for variable clearances and a reduced frequency of seal rubs. The design goal for compliant seals is therefore, to maintain a tight clearance between rotating and non-rotating parts, throughout the transient conditions experienced in engines. This paper presents the design of a new high-speed rotating test facility developed for the performance characterisation of turbine shaft seals. The rig features a 254 mm diameter rotor, capable of rotating at speeds of up to 15,000 rpm (equivalent to rotor surface speeds up to 200 m/s). The maximum pressure difference across a seal is 3.5 bar. In the first experimental campaign, the performance of a labyrinth seal was investigated. The rotordynamic coefficients of the seal were calculated by exciting the casing with an electromagnetic shaker. The leakage performance, direct and cross-coupled seal stiffnesses and effective damping coefficients are determined.