Title

Effect Of Increasing Pitch-To-Diameter Ratio On The Film Cooling Effectiveness Of Shaped And Cylindrical Holes Embedded In Trenches

Abstract

The continuous push for higher gas turbine inlet temperatures and operating efficiencies has led to increasingly sophisticated film cooling schemes. One such setup - trench cooling - consists of having film cooling holes embedded inside a gap, commonly called a trench. The coolant hits the downstream trench wall which forces it to spread laterally, resulting in more even film coverage downstream. Recent literature has focused on the effect that trenching has on cylindrical cooling holes only. In addition, researchers have limited their findings to a narrow range of pitch-to-diameter ratios (P/D). The current trends in the turbine industry of increasing or maintaining film cooling effectiveness while reducing the amount of coolant used dictate that P/D be increased, meaning less holes per row. In this study, we address both cylindrical and fan-shaped holes embedded in trenches. Tests have been conducted on 8 test plates with one row of cooling holes each varying the pitch-to-diameter ratio from 4 to 12 (12 configurations in total), and the blowing ratios from 0.5 to 2.0. We investigate the effect that P/D has on film cooling effectiveness for both hole geometries and compare them to similarly pitched baseline plates - fan and cylindrical - not in trenches. It is a known fact that increasing the pitch between holes, while maintaining all other conditions constant, decreases the average film effectiveness, however trenching has been shown to significantly increase film coverage. In this study, it has been shown that film cooling effectiveness of a cylindrical configuration can be maintained by the addition of a trench while cutting the number of holes in half. We also explore the behavior of shaped trenched holes, of which little has been said and find that their performance is actually hurt by trenching. Copyright © 2009 by ASME.

Publication Date

12-1-2009

Publication Title

Proceedings of the ASME Turbo Expo

Volume

3

Issue

PART B

Number of Pages

863-872

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

DOI Link

https://doi.org/10.1115/GT2009-60080

Socpus ID

77953190468 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/77953190468

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