A parametric study of the effects of inlet distortion on fan aerodynamic stability

The performance and aerodynamic stability of fan blades operating in a circumferentially non-uniform inlet flow is a key concern in the design of turbofan engines. With the recent trends in the design of civil engines with shorter inlet ducts (such as low-speed fans), or boundary layer ingesting engines, quick and reliable modelling of rotor/distortion interactions is becoming very important. The aim of this paper is to study the effects of inlet distortions on the aerodynamic stability of a fan blade and to identify the parameters that have a major impact on the stability of the blade. NASA rotor 67, for which a significant amount of measured data is available, was used for this study. In the first part of this study, the behavior of the fan with inlet distortion at near stall condition is analyzed, and it is shown how rotating stall is triggered. In the second part of this study, unsteady simulations with inlet distortion were performed to study how parameters, such as exit duct length and distortion strength, influence the stall margin of the blade.