Modeling of the unsteady aerodynamic force of turbine blades considering nonuniform vane pitch

Abstract

The nonuniform vane spacing of a turbine is a crucial technique for reducing the unsteady aerodynamic excitation force of the downstream blades, but it still lacks a quick and accurate forecast approach for its suppression effect. Employing the rectangular wave, we propose a modeling strategy for the unsteady aerodynamic force of turbine blades and construct a fast prediction model (FPM) for the excitation force. The model takes into account the physical mechanism of wake and potential field variations induced by vane nonuniformity and has reliable accuracy and robustness. The results demonstrate that FPM can rapidly predict the suppression benefit of the aerodynamic force on blades under a wide design range, and most of the errors in the forecast results of the maximum amplitude change rate are less than 10% compared with the numerical simulation. In addition, to guide the nonuniform configuration design, the suppression characteristic diagram is formed based on FPM and the nonuniform vane spacing law, through which the excitation suppression effect of the nonuniform scheme can be evaluated. The characteristic diagram shows that the scheme with a larger nonuniform pitch variation range and a smaller period ratio can achieve a more significant excitation reduction.