04 - Propulsion
MULTI-POINT DESIGN OPTIMIZATION OF A HIGH BYPASS RATIO FAN BLADE
S. Qiu¹, X.Y. Deng¹; ¹AVIC Commercial Aircraft Engine CO.LTD, China
The overall aerodynamic performance of the fan blade of a high bypass ratio aero engine is not only determined by its conventional aerodynamic parameters, such as pressure ratio and efficiency, but also the mass flow ratio of ingested water in the bypass duct during rain ingestion airworthiness test. To ensure the engine reliablity, the larger percentage of ingested water passing through the bypass duct is always desirable.In conventional fan blade airfoil design practice, the pressure ratio and efficiency are first preliminarily determined for the design point, usually the cruise condition, and the mass flow ratio of ingested water in bypass duct is then calculated for the approach condition for the accessment of its rain ingestion performance. With this approach, many iterations are usually needed before the ideal design results can be obtained, and such interations can be a considerable part of the design cost. To accelerate the design procedure, a multi-point optimization method is proposed in this paper to consider the multipal factors, i.e. the pressure ratio, efficiency and the mass flow ratio of ingested water, all together. In this method, the Bezier curve is used to parameterize the fan blade. The geometrical parameters are used as variables while the pressure ratio, efficiency, and the mass flow ratio of ingested water in bypass duct of the fan blade are used as the objective functions. The flow-field of fan rotor under water ingestion conditions is evaluated by ANSYS CFX. An Eulerian-Lagrangian approach is used in formulating the flow and droplet governing equations in the rotating reference frame. In order to resolve the difficulty of this high-dimensional multi-objective optimization problem, the NSGA-II algorithm is used to obtain a more complete picture regarding the trade-off among pressure ratio,efficiency and water mass ratio in bypass duct under three typical conditions. A multi-point design optimization of a typical high bypass ratio fan blade