The compressors in modern aero engines have reached overall pressure ratios of up to 60:1, which are likely to increase in future designs. This requires shorter blades in the latter stages of the high pressure compressor (HPC), leading to decreased stage efficiency and a reduced stability margin. Tighter tip clearances are therefore needed, but only a clear and complete understanding of the compressor rotor growth can guide the engine designer in predicting them. In the HPC, rotor discs contain cavities, where air diverted from previous stages is used for cooling purposes. The knowledge of the temperature distribution along the disc radius is crucial for both blade tip clearance design and to ensure the mechanical integrity of the rotor.

This paper presents the design of a recently commissioned rig, which is used to investigate the heat transfer in a heated compressor cavity with an engine representative geometry. It features an overhung design where air is drawn through the annular section between a stationary shaft and a disc pack containing the cavity. The external shroud of the discs is encapsulated by circular heaters, simulating the heating effect of the hot air passing through the compressor stage. Measurements of temperature and heat flux on the cavity surfaces are used to study the thermal effects of the flow structure (which is dominated by buoyancy forces). These thermal effects are investigated with respect to the relevant non-dimensional parameters (rotational Reynolds, Grashof and Rossby numbers). The geometry of the cavity is flexible in design - the cob thickness can be changed in order to understand its influence. The through-flow can also be heated, to replicate additional engine operating conditions (for example, during some transient cases). Temperatures and unsteady pressures in the core of the cavity can also be captured, while high frequency pressure sensors on the disc surface can provide information on the flow structure. The rig can acquire data during both steady-state and transient tests, resulting in a powerful tool to investigate an extensive range of engine conditions. \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \* \*


Design and Testing of a Rig to Investigate Buoyancy-Induced Heat Transfer in Aero-Engine Compressor Rotors

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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