A characteristic-based 1D axial compressor model for stall and surge simulations

A low-order unsteady one-dimensional axial compressor and combustor model has been developed at Cranfield University as part of a larger unsteady gas turbine engine model, with the ability to simulate compressor stall and surge. The flow is resolved using the 1D unsteady Euler equations and source terms are used to model bleed extraction (and addition), pressure losses, and heat and work exchange. Species tracking is used in the combustor part of the model, using a semi-coupled approach, to keep track of the combustion products and unburnt fuel in the main gas path. The equations are solved using a Roe Approximate Riemann Solver, modified to handle the high magnitude, transient source terms necessary for this simulation. The performance of the compressor during the transient surge event is described by a set of compressor characteristics, including reverse flow and rotating stall regions, obtained from a validated 3D throughflow code, ACRoSS. To replicate the exact response of multi-stage compressors, stage-by-stage characteristics are used during reverse flow.

The low-order method presented is successfully verified against ACRoSS for a high-power surge event of a coupled IPC and HPC configuration. The rate at which the total pressure at the outlet of the HPC collapses was calculated to be within 1%. This approach presents a faster alternative to high-fidelity CFD and can be used to investigate the compressor stall behaviour within minutes during the early design phase.