Flow-Field in a Linear Vane Cascade With Endwall Fillet and Film-Cooling

Abstract

Fillets at the junction of blade and endwall are employed to passively control the endwall secondary flows and total pressure losses in the cascade flow-field investigations. Film-cooling of the endwall using the slots at the entrance of blade passage is also investigated in the cascade setup to actively control the flow-field. The present paper reports the experimental measurements of the flow-field in a linear vane cascade that employs the endwall fillet and film cooling flow. The objectives are to investigate the additional effects of the film-flow on the secondary flows and total pressure losses in the cascade when the fillet is present. The fillet is employed at the vane-endwall junction from the leading edge to the throat region of the cascade passage. The film-cooling flow is provided from two slots located at the entrance of vane-passage simulating the platform gaps between the rotor/stator or combustor/NGV (nozzle guide vane) discs in the gas turbine. The vane-profile and cascade geometry are obtained from the first-stage of the GE-E3 gas turbine engine. The inlet Reynolds number based on the actual-chord of the vane is 2.0E+05. The inlet blowing ratio of the film cooling flow is varied between 1.1 and 2.3 as the density ratio of the film-flow to mainstream remains constant at 1.0. As the cascade is housed in an atmospheric wind tunnel, the measurements are obtained in the incompressible flow regime. The measurements include the distributions of endwall pressure, flow angles, axial vorticity, and total pressure losses along the vane passage. The results indicate the flow yaw angle and axial vorticity in the filleted passage without the film-cooling are reduced in the endwall region compared to the baseline case (no fillet and film cooling). Consequently, the passage vortex, which is the primary secondary flow, is weakened reducing the total pressure losses in the filleted passage. As the film-cooling flow is introduced in the filleted passage, the yaw angle in the endwall region is reduced further weakening the pitchwise-flow responsible for the development and strengthening of the passage vortex. The total pressure losses are also reduced further with the film-cooling flows and with the increasing blowing ratios. The film coverage of the endwall will be better as the passage vortex is weakened in the filleted passage. The present investigation is important for reducing the aerodynamic losses and improving of the film-cooling effectiveness in the gas turbine cascade.