For the purpose of improving turbine efficiency,a detailed investigation of flow field near rim seal region in the main annulus is absolutely essential.Purge flow egressed from the seal gap penetrates the hub boundary layer and travels along with the secondary flow in the main path.The propagation of the purge flow and its influence on the turbine performance are crucial and cannot be neglected in the aerodynamic and thermal design.In addition,the interaction of vane wake and blade potential field also has a significant impact on the turbine stage performance.In this study,flow field between inlet guide vanes (IGV) and rotor blades was experimentally investigated at specific positions with the help of a two-dimensional particle image velocimetry (2-D PIV).A phase-locking technique was also employed to capture the images of flow field at different rotor blade positions.Data acquired characterizes the impact of emergent purge flow on the flow structures within the main annulus.The impacts of vane wake and blade potential field on the flow fields were analyzed through characterizations provided by the time-averaged field results.Finally,flow fields at different main flow rates and under different seal gap widths were also presented and assessed.