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박세진(Sehjin Park),최석민(Seok Min Choi),손호성(Ho-seong Sohn),정희윤(Heeyoon Chung),조형희(Hyung Hee Cho) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
In real turbine blades, the direction of secondary flow channel is generally perpendicular to the direction of main flow. Thus, this study performs the numerical analysis to investigate the effects of the direction of secondary flow on the film cooling effectiveness of double-jet film cooling. The secondary flow is fed from two different directions, one is parallel and the other is normal to the direction of main stream. The blowing rate is 1 and the lateral injection angle is 22.5°. The numerical analysis is performed by using CFX, and the k-ε model is used for the turbulence model. When the secondary flow is supplied from the normal channel, blowing rates of both holes are different. Blowing rate of first hole is bigger than blowing rate of second hole. However, both blowing rates of holes are similar in the parallel secondary flow channel case. The asymmetrical film cooling effectiveness is obtained from the normal channel case because of different blowing rate. Similar blowing rates in the parallel channel case make anti-kidney vortex well, so the laterally averaged film cooling effectiveness of the parallel channel case is bigger than of the normal channel case.
박세진(Sehjin Park),최석민(Seok Min Choi),손호성(Ho-seong Sohn),정희윤(Heeyoon Chung),조형희(Hyung Hee Cho) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.7
막냉각에 관한 많은 연구들은 주유동과 이차유로가 평행한 형태로 연구가 이루어졌다. 하지만 실제 터빈 블레이드에서 이차유로의 방향은 일반적으로 주유동의 방향에 수직한 형태이다. 그래서 본 연구에서는 이차유동의 방향이 이중분사 막냉각의 효율에 미치는 영향을 수치해석을 통해 알아보고자 한다. 분사율은 1, 2이고 횡방향 분사각은 22.5°이다. 분사율이 1일 때 평행 형상에서는 안티키드니 와류가 잘 형성되어 막냉각 효율이 수직 형상의 경우보다 더 높다. 반면에 분사율이 2일 때 수직 형상의 막냉각 효율은 평행 형상보다 향상되었다. 많은 유량의 제트가 서로 반대 방향으로 분사되기 때문에 두 형상 모두 막냉각 효율이 높게 나타난다. 하지만 안티키드니 와류의 영향은 다른 분사율보다 상대적으로 작다. Several studies of film cooling were accomplished with a secondary flow channel parallel to the main flow. In real turbine blades, however, the direction of the secondary flow channel is generally normal to the main flow. Thus, this study performs a numerical analysis to investigate the effects of the direction of secondary flow on the effectiveness of double-jet film cooling. The blowing ratio is 1 and 2, and the lateral injection angle is 22.5°. The parallel channel case creates a well-developed anti-kidney vortex with a blowing ratio of 1, and the laterally averaged film cooling effectiveness of the parallel channel is enhanced compared to the normal channel. The normal channel shows higher performance with a blowing ratio of 2. Both cases show high film cooling effectiveness. These phenomena can be attributed to a high blowing ratio and flow rate rather than an anti-kidney vortex.
후방분사 원형 홀과 시스터 홀이 막냉각 효율에 미치는 영향
박세진(Sehjin Park),홍창우(Chang Woo Hong),김정주(JeongJu Kim),서원직(Won Jik Seo),조형희(Hyung Hee Cho) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Film cooling is one of cooling technologies which protects hot components of gas turbine by injecting the coolant jets through holes. Among various holes, cylindrical holes are mainly used for film cooling because of their easy fabrication. However, they obtain low film cooling effectiveness at high blowing ratios. Therefore, numerical analyses were performed to improve film cooling effectiveness of cylindrical holes by arranging forward and backward injection cylindrical holes. Forward and backward injection cylindrical holes composed one primary hole and two sister holes of which the cross-section area is a half of the primary hole cross-section area. Backward injection cylindrical holes improved film cooling effectiveness regardless of their arrangements. The case, arranged with a backward injection cylindrical hole in the primary hole and forward injection cylindrical holes in sister holes, obtained the highest film cooling effectiveness among three cases at a blowing ratio of 1.