Department of Mechanical Engineering

Hot gas ingestion in gas turbines

Experimental and CFD studies to understand hot gas ingress in gas turbines for the design of effective rims seals to reduce parasitic sealing flow requirements.

Turbine rotor disks are among the most highly stressed components in the engine, where metal temperatures must be limited to ensure acceptable life, integrity, and reliability. Rim seals are fitted at the periphery of the wheel-space between the turbine disk and its adjacent stator to reduce the ingress of hot mainstream gases.

The ingress is principally caused by circumferential pressure asymmetries in the mainstream annulus, radially outward of the rim seal. A superposed sealing (purge) flow, bled from the compressor, is used to cool the rotor disk and to prevent, or at least dilute the ingress to a tolerable level. Superfluous use of this purge air can reduce the cycle efficiency, and it is important to understand the fluid dynamics governing rim-seal performance.

Our two test facilities dedicated to the study of ingestion

  • A single-stage facility (built 2009) designed to investigate ingress into the wheel-space of a single-stage rotor-stator system.
  • A 1.5-stage facility (built 2013) designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disc.

Both test facilities are fluid-dynamically-scaled and operate at incompressible flow conditions, far removed from the harsh environment of the engine which is not conducive to experimental measurements.

CAD model showing the TRC 1.5-stage gas turbine test facilityThe rigs feature interchangeable rim-seal components, offering significant flexibility and expediency in terms of data collection over a wide range of sealing-flow rates. They were both specifically designed to enable an efficient method of ranking and quantifying the performance of generic and engine-specific seal geometries.

The Turbomachinery Research Centre has investigated the effects of ingestion experimentally, theoretically and computationally for almost a decade and has published over 30 conference/journal papers on the topic.