Measurements of ingress in upstream and downstream turbine wheel-spaces

This paper presents measurements of concentration and pressure in a new, highly instrumented and versatile, 1.5-stage gas turbine facility. The rig, which has been specifically designed for investigations related to hot gas ingestion, features interchangeable rim-seals, blading configurations and the capability of operating at a wide range of flow coefficients. The turbine section includes an upstream and a downstream wheel-space on either side of a rotor disc featuring turned blades. Measurements of CO2 concentration and steady static pressure were used to assess the pressure field in the turbine annulus and to investigate the performance of a radial clearance rim seal in both wheel-spaces. The wealth of data presented will be of great significance for CFD validation studies considering downstream cavities. Pressure measurements were made at various locations in the turbine annulus for a range of flow coefficients. In the annulus upstream of the rotor blades ΔCp1/2, the non-dimensional pressure difference, was shown to increase linearly with CF. Downstream however, ΔCp1/2 reaches a minimum at a CF close to the operating point. The radial variation in concentration effectiveness in the upstream and downstream wheel-spaces is provided for a range of sealing flow rates. In both cases the concentration on the stator walls was virtually invariant with radius and equal to that in the rotating core. The results also showed that for the same effectiveness, a smaller value of non-dimensional sealing flow is required in the downstream wheel-space, indicating a weaker driver for ingress.