Further validation of NHM in two-stage counter-rotating compressor

The nonlinear harmonic method (NHM) has been used to examine and analyze the unsteady rotor-rotor interaction of the two-stage counter-rotating compressor. To validate the NHM simulation results, the predicted characteristics of aerodynamic parameters were compared with the measured data and rigorous full-annulus unsteady simulations at typical working conditions. Based on the NHM deterministic stresses have been post-processed to compare to the full-annulus simulation to analyze distinct sources of unsteadiness. The NHM deliver accurate results at design points compared to full annulus results. The limits of the NHM are reached as soon as rotating stall effects occur as the theory foundation of the NHM, Fourier transformation, is no longer valid.