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This paper presents a 3D thermo-mechanical modelling method to calculate compressor local tip running clearances. The method requires a solid geometry representation of the compressor casings and main engine structures, including local geometry features such as thrust lugs, gearbox, sump, offtake bosses and struts. The finite element model is capable of predicting asymmetric temperature and displacement distributions for transient and steady-state conditions as a result of thermal, pressure and mechanical loads (e.g. thrust, gas torques, gravity, gusts, etc). This methodology has been applied to calculate local tip clearances on the intermediate pressure compressor of a civil aero-engine. The results from the 3D solid model have been compared to those obtained with more conventional analysis tools (i.e. 2D axisymmetric thermo-mechanical models and 3D isothermal shell and beam models) in order to build confidence in the new methodology. Local tip running clearances were measured on the intermediate pressure compressor by means of capacitance probes. Measured local closures for a typical square cycle including a low power idle phase and high power max take-off phase have been compared to predicted local closures to establish the validity of the new methodology.Copyright © 2008 by ASME |
