Analysis of unsteady blade row interaction using nonlinear harmonic approach

An efficient nonlinear harmonic methodology has been developed for predicting unsteady blade row interaction effects in multistage axial Row compressors. Flow variables are decomposed into time-averaged variables and unsteady disturbances, resulting in the time-averaged equations with the deterministic stress terms depending on the unsteady disturbances. The nonlinear interaction between the time-averaged flowfield and the unsteady parts are included by a simultaneous pseudotime integration approach,leading to a strongly coupled solution. The rotor/stator interface treatment follows a flux-averaged characteristic-based mixing-plane approach and includes the deterministic stress terms due to upstream running potential disturbances and downstream running wakes, resulting in the continuous nature of all parameters across the interface. The basic computational methodology is applied to the three-dimensional Navier-Stokes equations and validated against several cases. Results show that this method is much more efficient than the conventional nonlinear time-domain methods in modeling the unsteady blade row interaction effects.