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

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.