Investigation of three dimensional viscous unsteady flow and excitation force of turbomachinery stage

Flow in turbomachinery is inherently unsteady. The unsteady flow has effect on aerodynamic performance of turbomachinery and induces excitation force leading to vibration of blade, so it is necessary to investigate unsteady flow in turbomachinery stage. Based on the CFD software CFX, the numerical model and calculation method was developed by adopting RNG k-ε turbulence model, dual time step method, sliding interface model and structure grid, and then the flow field varied with time was studied. It is seen that the time-averaged unsteady isentropic efficiency is lower than that from steady analysis. Meanwhile, the unsteady aerodynamic load and excitation force factor were obtained too, and the excitation force factor is agreement with the data which comes from engineering practice and is widely used by engineers. The numerical results will do benefit to understand the effect of unsteady flow on aerodynamic performance of turbomachinery and provide essential parameters for response and fatigue analysis of blade.