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가스터빈 회전 블레이드 내 이차유로에서의 종횡비 특성 연구
김경민(Kyung-Min Kim),김윤영(Yun-Young Kim),이동호(Dong-Ho Rhee),조형희(Hyung-Hee Cho) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
The present study investigates heat/mass transfer characteristics in rotating two-pass ducts of three different aspect ratios with 90°-ribbed surfaces. The rotating duct has aspect ratios (W/H) of 0.5, 1.0 and 2.0 with a fixed hydraulic diameter (D<SUB>h</SUB>) of 26.7 ㎜. Each pass of the duct is connected with a 180-turning region with a round-shaped divider tip. 90°-rib turbulators are attached on the leading and trailing sides of the duct in parallel arrangements. The pitch to rib-height ratio (p/e) is 10 and the rib-height to hydraulic diameter ratio (e/D<SUB>h</SUB>) is 0.056. The Reynolds number based on the hydraulic diameter is set to 10,000 and the rotation number ranges from 0.0 to 0.20. Detailed local heat/mass transfer coefficients are measured using a naphthalene sublimation technique, and two-side heating condition is applied to simulate the actual gas turbine blade exposed to hot gas stream. The results show that the interaction among the vortices produced by the 180°-turn, the rib turbulators and the duct rotation. The turning region produces a pair of vortex cells. The rib turbulators disturb the main flow by producing reattachment and separation near the ribbed surfaces. The rotation of duct generates a secondary flow induced by Coriolis force. As the Rotation number increases, difference on heat/mass transfer between the leading and trailing surfaces increases. For the 90-ribbed duct, the averaged Sherwood number ratios increase as the aspect ratio increases for almost the tested Rotation numbers.