Design optimization of a high bypass ratio fan rotor against water ingestion

Abstract

Performance deterioration of a high bypass turbofan engine due to water ingestion is a major concern in the operation of gas turbines. The paper describes an optimization strategy to tackle the water ingestion problems on gas turbine engines, combined with design of experiment, response surface models and genetic algorithm. This study concentrates on reducing the level of water ingestion in the core engine system of a turbofan engine, seeking to perform the design optimisation of a fan rotor to maximize the mass flow of ingested water in bypass duct without sacrificing the fan rotor aero performance. 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. Data points for response evaluations are selected by Latin hypercube design and three dimensional Navier-Stokes analysis is carried out at these sample points. The quadratic response surface model is used to approximate the relationships between the design variables and flow parameters. The genetic algorithm is applied to the response surface model to perform global optimization to obtain the optimum design. The results of a parametric study of the effects of geometry of fan rotor on engine operating characteristics at rain ingestion condition are presented. As a result of this optimization, the aerodynamic performance is successfully increased. It is found that the strategy of this paper provides a reliable design optimization method for turbomachinery rotor at rain ingestion condition within reasonable computing cost.