Incidence Effect on the Aero-Thermal Performance of a Film Cooled Nozzle Vane Cascade

Abstract

In the present paper, the influence of inlet flow incidence on the aerodynamic and thermal performance of a film cooled linear nozzle vane cascade is fully assessed. Tests have been carried out on a solid and a cooled cascade. In the cooled cascade, coolant is ejected at the end wall through a slot located upstream of the leading edge plane. Moreover, a vane showerhead cooling system is also realized through four rows of cylindrical holes. The cascade was tested at a high inlet turbulence intensity level (Tu1 = 9%) and at a constant inlet Mach number of 0.12 and nominal cooling condition, varying the inlet flow angle in the range ±20 deg. The aero-thermal characterization of vane platform was obtained through five-hole probe and end wall adiabatic film cooling effectiveness measurements. Vane load distributions and surface flow visualizations supported the discussion of the results. A relevant negative impact of positive inlet flow incidence on the cooled cascade aerodynamic and thermal performance was detected. A negligible influence was instead observed at negative incidence, even at the lowest tested value of −20 deg.

Rotor Cascade Assessment at Off-Design Condition: An Aerodynamic Investigation on Platform Cooling

“…The flow angle measured at the theoretical 0 • incidence case is considered as a reference. The slightly negative incidence measured at the theoretical 0 • case is probably due to the turbulence generator, which induces a flow deviation upstream of the cascade, similar to [21,28].…”

“…Whatever the motivation, a reduced mass flow at fixed rotational speed translates into a negative incidence to the first rotor blade cascade for a subsonic flow condition, resulting in a reduction in secondary flows and related losses [20]. But, incidence along the blade span can significantly vary, due to the complex flow coming from the stator, resulting from the interaction between swirling combustion gases, coolant flow emerging from the combustor to stator interface gap, and stator secondary flows [21][22][23]. All these make the flow pattern interacting with the sealing flow emerging from the stator to rotor interface gap highly complicated, impacting its sealing and cooling capabilities.…”