Improvement of the Aerothermal Environment for a 90° Turning Duct by an Endwall Boundary Layer Fence

ABSTRACT An endwall boundary layer fence technique was adapted to impr ove the aerothermal environment of a gas turbine passage. The shape optimization of the fence was performed to maximize the improvement. The turbine passage was simulated by a 90° turning duct (ReD=360,000). The main purpose of the present investigation was to focus on finding a endwall boundary layer fence with minimum total pressure loss in the passage and heat transfer coefficient on the endwall of the duct. Anothor objective function was to minimize the area on the endw all of the duct. An approximate optimization method was used for the investigation to secure th e computational efficiency. Results indicated that a significant improvement in aerodynamic environ ment can be achieved through the application of the fence. Improvement of the thermal environment was smaller than that of the aerodynamic enviroment.초 록 본 논문에서는 가스터빈 유로의 열유동 환경을 개선하기 위해 끝벽면 경계층 판을 이용한 방법을 적용하였으며, 이 방법에 의한 효과를 최대화하기 위해 경계층 판의 형상에 대한 최적화를 수행하였다. 터빈 유로를 모사하기 위해 90° 곡관을 이용하였다. 터빈 유로에서의 전압력 손실과 유로 끝벽면에서의 열전달 계수, 그리고 끝벽면 면적을 최소화하는 곙계층 판 형상 도출을 연구의 목적으로 하였으며, 최적화 과정의 효율성을 위해 근사 최적화 기법을 적용하였다. 연구결과를 통해, 최적화된 경계층 판에 의한 상당한 공력환경 개선을 확인할 수 있었으며, 열환경 개선 정도는 공력환경 개선정도에 비해 작게 나타났다.Key Words: Endwall Boundary Layer Fence(끝벽면 곙계층 판), Optimization(최적화), Secondary Flow(2차 유동), 90° Turning Duct(90° 곡관)

[1]  J. Whitelaw,et al.  Curved Ducts With Strong Secondary Motion: Velocity Measurements of Developing Laminar and Turbulent Flow , 1982 .

[2]  T. H. Ko,et al.  A numerical study on entropy generation and optimization for laminar forced convection in a rectangular curved duct with longitudinal ribs , 2006 .

[3]  Douglas C. Montgomery,et al.  Response Surface Methodology: Process and Product Optimization Using Designed Experiments , 1995 .

[4]  Cengiz Camci,et al.  Secondary flow and forced convection heat transfer near endwall boundary layer fences in a 90° turning duct , 2002 .

[5]  R. L. Iman,et al.  Latin hypercube sampling (program user's guide). [LHC, in FORTRAN] , 1980 .

[6]  S. Orszag,et al.  Development of turbulence models for shear flows by a double expansion technique , 1992 .

[7]  Karen A. Thole,et al.  Computational Design and Experimental Evaluation of Using a Leading Edge Fillet on a Gas Turbine Vane , 2001 .

[8]  Tsutomu Adachi,et al.  Secondary Flow Control and Loss Reduction in a Turbine Cascade Using Endwall Fences , 1989 .

[9]  T. Simon,et al.  Effectiveness of the Gas Turbine Endwall Fences in Secondary Flow Control at Elevated Freestream Turbulence Levels , 1993 .

[10]  B. V. Leer,et al.  Towards the ultimate conservative difference scheme V. A second-order sequel to Godunov's method , 1979 .

[11]  Passage Flow Structure and Its Influence on Endwall Heat Transfer in a 90 deg Turning Duct: Mean Flow and High Resolution Endwall Heat Transfer Experiments , 1997 .