Aerothermal Performance of a Nozzle Vane Cascade With a Generic Nonuniform Inlet Flow Condition—Part I: Influence of Nonuniformity Location

In this paper, the modifications induced by the presence of an inlet flow nonuniformity on the aerodynamic performance of a nozzle vane cascade are experimentally assessed. Tests were carried out in a six vane linear cascade whose profile is typical of a first stage nozzle guide vane of a modern heavy-duty gas turbine. An obstruction was located in the wind tunnel inlet section to produce a nonuniform flow upstream of the leading edge plane. The cascade was tested in an atmospheric wind tunnel at an inlet Mach number Ma₁ = 0.12, with a high turbulence intensity (Tu₁ = 9%) and variable obstruction tangential and axial positions, as well as tangential extension. The presented results show that an inlet flow nonuniformity influences the stagnation point position when it faces the vane leading edge from the suction side. A relevant increase of both 2D and secondary losses is observed when the nonuniformity is aligned to the vane leading edge. When it is instead located in between the passage, it does not affect the stagnation point location, in the meanwhile allowing a reduction in the secondary loss.