Study of Tandem Rotor Dual Wake Interaction With Downstream Stator Under Unsteady Numerical Approach

Abstract

Abstract This paper highlights the intricate rotor-stator interaction between a tandem bladed rotor and a single-bladed stator in the light of unsteady numerical simulations. With the promising pressure rise capability of the tandem bladed compressor stage, it becomes obligatory to investigate the rotor-stator interaction owing to its dominant effect on overall stage performance. The multi-passage rotor-stator unsteady simulations have been performed using transformation methods in ANSYS CFX. Due to the presence of two highly loaded rotor blades, the tandem rotor exhibits peculiar rotor-stator interaction in terms of multiple wake impingement on the stator. Incorporating tandem blading on the rotor instead of the stator (which is more common) has some aerodynamic leverage but it also constricts the design envelope in terms of choice of blade axial overlap and percentage pitch. This results in managing the desired loading by varying blade overlap from hub to shroud with careful loading distribution. The variation of aerodynamic loading from hub to tip for both the rotor blades results in spanwise varying wake strength. The initially distinct wake structures merge with a certain frequency resulting into a thicker wake. This changes the incidence on the downstream stator. Additionally, the rotor blades are highly loaded in the tip region which results in the complex interaction between end-wall boundary layer and tip leakage flow. Cumulatively, these conditions constitute a challenging aerodynamic field for the downstream stator. The incidence change caused by the velocity defect at the rotor exit plane affects the aerodynamic loading of the stator. The tip leakage flow behavior is entirely different in a tandem bladed rotor due to the presence of blade overlap. The study focuses on the qualitative interaction between the rotor wakes and blockage with the downstream stator and put forwards some aspects of the tandem rotor-single stator stage design especially for core compressors of aero engine application.