Experiment on Gas Ingestion Through Axial-Flow Turbine Rim Seals

Abstract

It has been suggested by researchers that ingestion, through rim seals, of mainstream gas into axial-flow turbine disk cavities is a consequence of the prevailing unsteady three-dimensional flow field. The cause–effect relationship is complex—to help understand it, experiments were performed in a model single-stage turbine rig using two different vane-blade configurations. Selected measurements from one of the configurations were reported earlier (1999–2001). The second configuration is new, featuring smaller numbers of vanes and blades and a larger vane turning angle. Selected measurements are presented and compared to those from the first configuration. The measurements include unsteady and rotor revolution time-average static pressure spatial distributions, and spatial distribution, in the rotor-stator cavity, of time-average ingestion. The parameters in the experiments were the main airflow rate, the purge/seal airflow rate, and the rotor speed. Unsteady three-dimensional CFD simulation may be helpful in identifying the roles of the many intertwined phenomena in the ingestion process.

Flow mechanisms in axial turbine rim sealing

“…Experiments by Cao et al [11], Roy et al [32], Beard et.al. [33], Savov et al [34], Schädler et al [35], Jakoby et al [24] and Town et.al.…”

“…Radial rim seals were studied experimentally by Roy et al [32], Savov et al [34], and Town et al [36], as shown in figure 5 and table 2. The seal and cavity geometries were quite different in these cases, but all tests were conducted with a highly swirling annulus flow.…”

“…The earliest report of sub blade passing frequency unsteadiness in radial rim seals was given by Roy et al [32]. In this experiment unsteady pressure measurements were recorded within the cavity up to the rim seal region at different purge flow conditions.…”

“…Zhou et al [45] reported URANS solutions for a 14.4 o sector model with blades and vanes for a simple double seal configuration tested at Arizona State University [32]. Ingestion was shown to be underpredicted compared to measurements and the authors suggested that this may be due to rotating low pressure zones being supressed by the small sector periodicity.…”

Experimental and Analytical Assessment of Cavity Modes in a Gas Turbine Wheelspace

“…They concluded that reducing the radial gap has a larger effect on sealing effectiveness than that associated with increasing the axial overlap. Figure 10 in Roy [14], where results are presented for several non-dimensional flowrates cw -the ratio of purge mass flowrate through the seal to the product of the fluid viscosity p and the seal radius b, i.e. cW = _.…”