The Use of CFD to Generate Heat Transfer Boundary Conditions for a Rotor-Stator Cavity in a Compressor Drum Thermal Model

In an engine design process, thermo-mechanical analyses of compressor drums and casings are undertaken, to predict component temperatures and displacements, which are ultimately used for material selection, blade clearance control and lifing of components. The thermal boundary conditions are sourced from a small number of standard flow field and heat transfer solutions, leading to a reliance on engine thermocouple tests to provide calibration factors on the boundary conditions, which with changes in inlet flows and cavity geometry from the tested arrangements are unproven, limiting the ability to readacross the test information into new designs. Given that the thermal boundary conditions in compressor drum and casing components are largely driven by complex flow physics, in the absence of suitable test information, CFD methods can be used to provide boundary specification of the thermo-mechanical problem, incorporating the complex physics involved. Without the insight of the flow field solution in complex flow regions, specification of the boundary conditions is rather subjective and mostly based on intuition. This study shows the use of CFD to provide the boundary conditions for the rotor-stator cavity at the front of an IP compressor drum. The CFD is run adiabatically and through a set of unit heat transfer cases on separate sections of the cavity wall, at key points in the flight cycle. The analyses provide appropriately characterized thermal boundary conditions (specifically heat transfer coefficients and adiabatic wall temperatures) that are transferred into the thermo-mechanical model, which can then be run through a wide range of cycles without the need for further CFD calculations.