Experiments 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 time-average static pressure spatial distributions, and spatial distribution, in the rotor-stator cavity, of time-average ingestion. The parameters in the experiments were: main air flow rate, purge/seal air flow rate, and 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 Jakoby et al., 24 Schädler et al., 34 Roy et al., 35 Savov et al., 36 Town et al. 37 and Beard et al.…”

Numerical Simulation of the Flow Interaction Between Turbine Main Annulus and Disc Cavities

“…Interaction between the blade and vane flows may also be important. Recent CFD and experimental studies [3,[11][12][13] have shown that at low sealing flow rates unsteady flow features, unrelated to the blade passing frequency, are important and that complete 360 deg models may be required to fully represent these features. Flow structures similar to those identified for ingestion due to disc pumping have been identified in CFD solutions, and confirmed experimentally by unsteady pressure measurements.…”

The Design of a Steady Aero Thermal Research Turbine (START) for Studying Secondary Flow Leakages and Airfoil Heat Transfer

“…Therefore, the main gas path annulus was reduced to include span locations only from the hub to mid-span on the airfoils, resulting in half-span turbine vanes and blades. This approach has been successfully performed and reported in the literature by other researchers including Feiereisen [30] and Roy [13][14], and allowed the air flow capacity requirements to be cut approximately by half for Phase 1. Current plans for the long term Phase 2 operation include doubling the air mass flow rate capability to near 11.4 kg/s (25 lbm/s) by adding a second identical large compressor, in parallel with the first compressor, that will allow studies to be performed using full span airfoils, larger turbine disk diameters, higher rotational speeds (higher Re), and additional turbine stages.…”