Effects of Upstream Endwall Film Cooling on a Vane Cascade Flowfield

Abstract

The effects of film-cooling on the endwall region flow and aerodynamic losses are investigated experimentally as the film-flow is delivered from the slots in the endwall upstream of a linear vane cascade. Four slots inclined at 30° deliver the film-jet parallel to the main flow at four blowing ratios between 1.1 and 2.3 and at a temperature ratio of 1.0. The slots are employed in two configurations pitchwise-all four slots open (case-1) and two middle slots open (case-2). The inlet Reynolds number to the cascade is 2.0E+05. Measurements of the blade surface pressure, axial vorticities, yaw angles, and total pressure loss distributions along the cascade are reported with and without (Baseline) the film-cooling flow. The results show the film-flow changes the orientations, distributions,and strength of the endwall secondary flows and boundary layer. The case-1 of film-cooling provides more massflux and momentum than the case-2 affecting the passage vortex legs. The overall total pressure losses at the cascade exit are always lower for the film-cooling cases than for the Baseline. The overall losses are also lower at the low blowing ratios, but higher at the high blowing ratios for the film-cooling case-1 than for the case-2. NomenclatureC, C ax , P, S = true blade-chord, axial blade-chord, pitch, span C P,Blade = blade surface static pressure coefficient C pt,loss , C Pt,Loss = total pressure loss coefficient M = passage mass flow rate MFR, M in = mass fraction ratio, inlet blowing ratio P b,x = pressure on blade surface P s,r , P t,r = (static pressure, total pressure) at reference plane P t,x , P t,box = local total pressure at exit, total pressure in plenum box PS, SS, TE = pressure-side, suction-side, trailing edge Re = inlet Reynolds number based on actual-chord U = freestream velocity (X, Y, Z) = local Cartesian coordinates (X G , Y G , Z G ) = global Cartesian coordinates Lower Case u, v, w = velocity components along (X, Y, Z) s = blade surface coordinate Greek δ = boundary layer thickness Δ = change in related quantity ω = vorticity ρ = density

Influences of large fillets on endwall flows in a vane cascade with upstream slot film-cooling

“…For the fillet-1 in Figs. Because of the high turning of streamlines [23,36] and yaw angles (shown later in Fig. 14) toward the suction side in endwall region, the coolant streams also turn toward the suction side and low values of θ concentrate at the suction side of plane-3 for the baseline-1 in Figs.…”

“…Note that the measurement plane-4 in Fig. 1(b) is located about 7 mm upstream in reference to the exit plane in [23].…”

“…The results of [15][16][17][18][19] show the interactions of the coolant flows from 3 slots with the endwall flows intensify the passage vortex and secondary flow losses. However, the secondary flows in the vane cascade of [20][21][22][23] become weak with the film-cooling flows from the special slot geometry in the upstream endwall. The results of [20,23] with the angled purge-cooling indicate the reduced flow turnings relative to the mid-span streamlines weaken the passage vortex and total-pressure losses at the cascade exit.…”

“…However, the secondary flows in the vane cascade of [20][21][22][23] become weak with the film-cooling flows from the special slot geometry in the upstream endwall. The results of [20,23] with the angled purge-cooling indicate the reduced flow turnings relative to the mid-span streamlines weaken the passage vortex and total-pressure losses at the cascade exit. Oke and Simonson [24] measure the temperature field to show the film-cooling flow distributions on the endwall with different arrangements of the slot bleed at the cascade inlet.…”

“…However, the effects of large fillets on the film-cooled endwall flow-field and coolant distributions with the upstream slot-bleed flow in the cascade have not been investigated in detail. The flow results of slot-bleed in [23] are presented without the filleted vanes. Mahmood and Arnachellan [28] provide flow properties with the slot-bleed in a filleted vane cascade.…”