Film Cooling From a Row of Holes Embedded in Transverse Slots

Abstract

Film cooling performance for a row of cylindrical holes can be enhanced by embedding the row in transverse slots. The geometry of the transverse slot greatly affects the cooling performance downstream of injection. The effect of the slot exit area and edge shape is investigated. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 7150 at three different coolant-to-mainstream blowing ratios of 0.5, 1.0, and 1.5. The results show that the film cooling holes provide higher film effectiveness when embedded in a slot. However, in some geometries when the slot begins at the upstream edge of the hole, the film effectiveness diminishes. The heat transfer coefficient enhancement due to the embedding is not significantly higher compared to the typical unembedded cylindrical hole. The overall heat flux ratio comparing film cooling with embedded holes to unembedded holes shows that the full slot and downstream slot spacing after the hole exit produce the highest heat flux reduction. The holes-in-slot geometry is certainly very promising.

Film cooling effectiveness and flow structures for novel upstream steps

“…Certain configurations of cylindrical holes embedded in transverse trenches have been shown to perform similarly to shaped holes, and trenches would be cheaper to manufacture than shaped holes. Several studies have investigated various trench configurations such as Bunker [14], Waye and Bogard [15], Lu et al [16], Harrison and Bogard [17], Jia et al [18], Zuniga and Kapat [19].…”

A Review of Hole Geometry and Coolant Density Effect on Film Cooling

“…Results showed the radial angle shaped hole. Lu et al (2005) investigated the film cooling performance for a row of cylindrical holes by embedding the row in transverse slots. Transverse slots could be formed around the holes in the event that the blade surface is sprayed with TBC leaving the holes embedded in trenches.…”

Multi-field coupling analysis on the film-cooling with transverse and arched trenches

“…Due to the depth under the surface, the coolant jet may be attached to the surface under the higher blowing ratio. Lu (Lu et al, 2005) found that the trench depth of 0.75D was optimum. Dorrington (Dorrington et al, 2007) investigated the trench width and found that the narrow trench performed better film-cooling effectiveness at shallow trench.…”