Experimental and computational studies of the turbulent flow field in a model gas turbine disk cavity have been carried out. The experiments were performed in a rig which features a rotor disk-stator disk configuration with stator vanes, rotor blades, and rim discouragers with axial overlap. Particle Image Velocimetry was used to map the flow field in the cavity at three positions along the axial gap between the disks for various mainstream and secondary air flow rates, and rotor speeds. Static pressure distribution in the cavity at the stator disk and the circumferential distribution of the same at the mainstream passage outer shroud were measured.
A recirculation region developed radially inboard in the disk cavity where a strong radial outflow was found close to the rotor disk and a weak radial inflow near the stator disk. This is the source region where the rotation of the core fluid is minimal, its radial extent increasing with the secondary air flow rate. Radially outboard, in the core region, the flow was rotation-dominated except when the secondary air flow rate was high.
The peak-to-peak amplitude of the circumferential pressure asymmetry in the mainstream flow path increased as the square of the main air flow rate, attained its maximum value at the stator vane exit, and decreased rapidly downstream. For the experiments performed, no circumferential pressure asymmetry could be found in the disk cavity, even near its rim. The rotating fluid in the core region of the cavity gave rise to an adverse radial pressure gradient, its magnitude increasing as the secondary air flow rate decreased. This feature can facilitate ingress of mainstream gas into the cavity.
Concurrently with the experiments, the flow field was simulated numerically using the commercial CFD code FLUENT/UNS. The agreement between the measurements and the computed results is generally good.