Calculating stall and surge transients

Many aspects of the aerodynamic operation and the mechanical integrity of an aeroengine are determined by the stall and surge transients of the compression system. A, physically based, blockage-mixing method and a novel blockage-transport equation are presented that can be used to estimate blade row operation at severe off-design conditions. The blockage-mixing method is proposed based on an analysis of the large separations that are present within a blade passage during reverse-flow (negative axial velocity) conditions. A time accurate computational simulation has been developed, based on the blockage-mixing method, which solves for the moderate to long lengthscale compressible unsteady flowfield within a compression system. The flow through each blade row is resolved in the axial, circumferential and radial directions. Calculated stall and surge events are compared with experimental data and the ability to calculate an aeroengine transient is demonstrated. The simulation is presented as a computational tool for estimating the aerodynamic loads during compression system instability events.