Sealing Flow Requirements for a Rotating Disk With External Swirling Flow

Abstract

Experiments have been performed to investigate the sealing flow requirements for a shrouded, rotating disk with external swirling flow. In some gas turbine applications, it is desirable to provide sealing flow to prevent ingress of process gas into the cavity between the turbine disk and its stator. The tangential or swirl component in flow leaving the nozzles can significantly affect the amount of flow required to seal the turbine disk. The experimental flow model used water as a working fluid and was hydrodynamically scaled to match conditions typical of hot gas expander turbines used for energy recovery in the petrochemical industry. Flow in the seal gap was observed using a stream of dye injected on the stator face near the periphery. Differential pressures were measured on the stator face and related to the observed direction of flow on the stator face. The pressures and sealing flows were normalized by the disk and gap geometry and the applied flow conditions, then compared to published data for shrouded, rotating disks with no applied, external flow. For tests where the external tangential velocity was roughly equal to twice the rim speed of the disk, sealing flow requirements were found to be 1.5 to 2.0 times greater than for a disk without the applied, external flow.