Film Cooling Effectiveness Distributions on a Turbine Blade Cascade Platform With Stator-Rotor Purge and Discrete Film Hole Flows

Abstract

An experimental investigation to obtain detailed film cooling effectiveness distributions on a cooled turbine blade platform within a linear cascade has been completed. The Reynolds number of the freestream flow is 3.1×105, and the platform has a labyrinthlike seal upstream of the blades to model a realistic stator-rotor seal configuration. An additional coolant is supplied to the downstream half of the platform via discrete film cooling holes. The coolant flow rate through the upstream seal varies from 0.5% to 2.0% of the mainstream flow, while the blowing ratio of the coolant through the discrete holes varies from 0.5 to 2.0 (based on the mainstream velocity at the exit of the cascade). Detailed film cooling effectiveness distributions are obtained using the pressure sensitive paint (PSP) technique under a wide range of coolant flow conditions and various freestream turbulence levels (0.75% or 13.4%). The PSP technique clearly shows how adversely the coolant is affected by the passage induced flow. With only purge flow from the upstream seal, the coolant flow rate must exceed 1.5% of the mainstream flow in order to adequately cover the entire passage. However, if discrete film holes are used on the downstream half of the passage, the platform can be protected while using less coolant (i.e., the seal flow rate can be reduced).

Turbine Blade Film Cooling Using PSP Technique

“…Using coolant (at 0.5% to 2% of mainstream passage mass flow rate) with DR = 1.0, it was concluded that using typical advanced rotor-stator seals reduces film cooling effectiveness compared with conventional inclined slots. Wright et al (2008) used discrete film cooling holes in addition to the inclined slots to improve film coverage. Wright et al (2009) tested the effect of upstream wakes generated by wake rods and delta wings to simulate the effect of upstream stator wakes and end-wall vortices, with the conclusion that the delta wings produce a larger negative effect on film cooling.…”

Influence of different film cooling arrangements on endwall cooling

“…The results indicated the existence of a strong interference between the cooling jets and the endwall secondary flows. PSP technique was also used by Wright et al [20] cooling effectiveness distributions on a blade platform with both purge flow and discrete film holes. Takeishi et al [21] investigated the influence of film cooling jet on leading edge horseshoe vortex employing LIF, PIV techniques.…”

Film cooling effectiveness distribution of cylindrical hole injections at different locations on a vane endwall

“…The results indicated the existence of a strong interference between the cooling jets and the endwall secondary flows. PSP technique was also used by Wright et al [20] to study the film cooling effectiveness distributions on a blade platform with both purge flow and discrete film holes. Takeishi et al [21] investigated the influence of film cooling jet on leading edge horseshoe vortex employing LIF, PIV techniques.…”