Evaluation of Various Numerical Methods for Blade Row Interaction in Turbomachinery

Abstract The flow within turbomachinery is inherently unsteady, thereby the unsteady rotor-stator interaction usually has a large effect on the performance of multistage turbomachines. However, fully unsteady simulations are still too time-consuming for in the routine design of turbomachinery, thus, the steady simulation with mixing-plane method that neglects the interaction is still widely used. Some reduced-order unsteady methods, such as harmonic balance (HB) method and space-time gradient (STG) method, have been proposed to simulate the unsteady periodic flow for the purpose of reducing CPU time consumption with sufficient accuracy. In this work, four mixing-plane methods, the HB method, and the STG method are implemented into the open source CFL3D solver. Effect of these methods on predicting unsteady rotor-stator interaction are evaluated in two flow cases, including a quasi-three-dimensional radial slice of a turbine stage and a 1.5-stage high-speed axial compressor. Results show that both the high-order HB and STG methods own the similar ability as the conventional unsteady simulation in predicting the wake transmitting from upstream to downstream, while the steady mixing-plane methods fail. Numerical results of the 1.5 stage compressor show that the wake of the first row can reach the third blade row. And this phenomenon can be also clearly captured by HB and STG methods. Fourier analysis method is used to analyze the interaction in different blade rows to evaluate various numerical methods.