Applicability of heat pipes and impingement cooling for axial compressor tip clearance control: a preliminary investigation

Abstract This publication presents the results of a numerical analysis aimed at assessing the applicability of thermal tip clearance control (TCC) to the fore-to-last stage of a 10-stage high-pressure compressor system. The chosen geometry is representative for the HPC rear stages of a modern middle-sized turbofan, designed for large business jets and regional airliners. Simplified models for two TCC concepts were implemented, isolated and in combination: external impingement cooling and heat pipes. The analysis was performed by means of finite-element thermostructural simulations. Transient operational cycles, derived from a meanline model, along with empiric correlations for heat convection provided the required boundary conditions. Qualitative similarity to selected previous works in terms of temperature, stress and clearance evolutions was achieved. The combination of concepts demonstrated its potential as a TCC system with up to 0.45% reductions in rotor and stator clearances. Calculated heat pipe temperatures and heat fluxes were inside the estimated operational limitations. Regarding stresses, some local concentrations were observed, without significant impact in critical stress regions. A slam cycle analysis showed that, while blade rubbing remains a possibility, it can be mitigated by robust cooling control. All in all, the concept was deemed worthy of more detailed studies.