In gas turbine engines, film cooling holes are often fed by an internal crossflow, with flow normal to the direction of the external flow around the airfoil. Many experimental studies have used a quiescent plenum to feed model film cooling holes and thus do not account for the effects of internal crossflow. In this study, an experimental flat plate facility was constructed to study the effects of internal crossflow on a row of cylindrical compound angle film cooling holes. There are relatively few studies available in literature that focus on the effects of crossflow on film cooling performance, with no studies examining the effects of internal crossflow on film cooling with round, compound angled holes. A crossflow channel allowed for coolant to flow alternately in either direction perpendicular to the mainstream flow. Experimental conditions were scaled to match realistic turbine engine conditions at low speeds. Cylindrical compound angle film cooling holes were operated at blowing ratios ranging from 0.5 to 2.0 and at a density ratio (DR) of 1.5. The results from the crossflow experiments were compared to a baseline plenum-fed configuration. This study showed that significantly greater adiabatic effectiveness was achieved for crossflow counter to the direction of coolant injection.
Early stage gas turbine blades feature complicated internal geometries in order to enhance internal heat transfer and to supply coolant for film cooling. Most film cooling experiments decouple the effect of internal coolant feed from external film cooling effectiveness, even though engine parts are commonly fed by cross-flow and feature internal rib turbulators which can affect film cooling. Experiments measuring adiabatic effectiveness were conducted to investigate the effects of turbulated perpendicular cross-flow on a row of 45 deg compound angle cylindrical film cooling holes for a total of eight internal rib configurations. The ribs were angled to the direction of prevailing internal cross-flow at two different angles: 45 deg or 135 deg. The ribs were also positioned at two different spanwise locations relative to the cooling holes: in the middle of the cooling hole pitch and slightly intersecting the holes. Experiments were conducted at a density ratio of DR = 1.5 for a range of blowing ratios including M = 0.5, 0.75, 1.0, 1.5, and 2.0. This study demonstrates that peak effectiveness can be attained through the optimization of cross-flow direction relative to the compound angle direction and rib configuration, verifying the importance of hole inlet conditions in film cooling experiments. It was found that ribs tend to reduce adiabatic effectiveness relative to a baseline, smooth-walled configuration. Rib configurations that directed the internal coolant forward in the direction of the mainstream resulted in higher peak adiabatic effectiveness. However, no other parameters could consistently be identified correlating to increased film cooling performance. It is likely that a combination of factors is responsible for influencing performance, including internal local pressure caused by the ribs, the internal channel flow field, in-hole vortices, and jet exit velocity profiles. This study also attempted to replicate the possibility that film cooling holes may intersect ribs and found that a hole which partially intersects a rib still maintains moderate levels of effectiveness.
In gas turbine engines, film cooling holes are often fed by an internal cross-flow, with flow normal to the direction of the external flow around the airfoil. Many experimental studies have used a quiescent plenum to feed model film cooling holes and thus do not account for the effects of internal cross-flow. In this study, an experimental flat plate facility was constructed to study the effects of internal cross-flow on a row of cylindrical compound angle film cooling holes. Operating conditions were scaled, based on coolant hole Reynolds number and turbulence level, to match realistic turbine engine conditions. A cross-flow channel allowed for coolant to flow alternately in either direction perpendicular to the mainstream flow. Film cooling holes were operated at blowing ratios ranging from 0.5 to 2.0 at a density ratio of 1.5. There are relatively few studies available in literature that focus on the effects of cross-flow on film cooling performance, with no studies examining the effects of internal cross-flow on film cooling with round, compound angled holes. This study showed that significantly greater adiabatic effectiveness was achieved for cross-flow in the opposite direction of the span-wise direction of the coolant holes and provides possible explanations for this result.
Early stage gas turbine blades feature complicated internal geometries in order to enhance internal heat transfer and to supply coolant for film cooling. Most film cooling experiments decouple the effect of internal coolant feed from external film cooling effectiveness, even though engine parts are commonly fed by cross-flow and feature internal rib turbulators which can affect film cooling. Experiments measuring adiabatic effectiveness were conducted to investigate the effects of turbulated perpendicular cross-flow on a row of 45° compound angle cylindrical film cooling holes for a total of eight internal rib configurations. The ribs were angled to the direction of prevailing internal cross-flow at two different angles: 45° or 135°. The ribs were also positioned at two different span-wise locations relative to the cooling holes: in the middle of the cooling hole pitch, and slightly intersecting the holes. Experiments were conducted at a density ratio of DR = 1.5 for a range of blowing ratios including M = 0.5, 0.75, 1.0, 1.5, and 2.0. This study demonstrates that peak effectiveness can be attained through the optimization of cross-flow direction relative to the compound angle direction and rib configuration, verifying the importance of hole inlet conditions in film cooling experiments. It was found that ribs tend to reduce adiabatic effectiveness relative to a baseline, smooth-walled configuration. Rib configurations that directed the internal coolant forward in the direction of the mainstream resulted in higher peak adiabatic effectiveness. However, no other parameters could consistently be identified correlating to increased film cooling performance. It is likely that a combination of factors is responsible for influencing performance, including internal local pressure caused by the ribs, the internal channel flow field, in-hole vortices, and jet exit velocity profiles. This study also attempted to replicate the possibility that film cooling holes may intersect ribs and found that a hole which partially intersects a rib still maintains moderate levels of effectiveness.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.