Film Cooling Enhancement with Surface Restructure
Discrete-hole film cooling is used extensively in turbine components. In past decades, many research works concerning this technique have been published. Recently, efforts have been directed at seeking technologies that would increase film cooling effectiveness. Particularly, surface reshaping through protective coatings, such as a thermal barrier coating (TBC), is very attractive to turbine designers because extra machining work is not needed for its application. In the present work, film cooling enhancement with surface restructure is experimentally studied using an infrared (IR) imaging technique.
The first surface structure studied is the surface with flow-aligned blockers. The studied configurations include single-hole and three-hole-row structures. The single-hole case is used for studying the effects of blocker design parameters, which include blocker height (0.2D, 0.4D, and 0.6D), distance between two neighboring blockers (0.8D, D, and 1.2D), blocker length (2, 4, and 6), and blowing ratio M (0.43 and 0.93). The design with the best performance is chosen for the three-hole-row cases.
The second surface shape studied, is the so-called upstream ramp, which is placed in front of a row of film cooling holes. Investigated geometrical parameters include upstream ramp angles (8.5o, 15o, and 24o) and blowing ratio M (0.29, 0.43, 0.57, 0.93, and 1.36). Detailed local film cooling effectiveness and heat transfer coefficient are measured using an IR imaging technique.
The third film cooling concept is the so-called trenched film cooling holes, i.e., film cooling holes sitting in a transverse groove. The film cooling structure for this experimental test consists of a three-hole row embedded in a trench 0.5D in depth and 2D in width, where D is the diameter of the holes. Five blowing ratios (0.29, 0.43, 0.57, 0.93, and 1.36) are tested. Based on the tested results, the three film cooling schemes are also compared.
To implement the experimental work, a test system, which employs a FLIR infrared system to obtain local heat transfer characteristics of both two- and three-temperature problems, is developed. Detailed theoretical issues of data reduction and experimental procedures are presented.
Advisor:Laura Schaefer; Minking K. Chyu; Gerald H. Meier; Sung K. Cho
School:University of Pittsburgh
School Location:USA - Pennsylvania
Source Type:Master's Thesis
Date of Publication:01/28/2009