Prediction of the surge line of multi-stage axial compressors

The calculation method presented intends to predict the surge line of a multi-stage axial compressor, starts from the knowledge of its complete geometry and from the aerodynamical characteristics of the blading of each stage. The stability of the flow is studied on each stream surface, deduced from a radial equilibrium calculation, using the Lyapunov theory applied to the partial differential equations system, established from the continuity, momentum and energy unsteady equations, linearized around the steady state running point under consideration. Satisfactory results are obtained and the short calculation delay involved by the numerical model allows to perform thorough parametrical studies during the early phase of development of new jet engines.