Fan casing contouring under consideration of aeroacoustics, mechanics, aeroelasticity and whole engine performance

Aircraft propulsion will continue to rely on gas turbine technology for the next decades to come. Thus, to achieve environmental agreements, ensure engine safety and retain economic competitiveness, ongoing development with a multidisciplinary design approach is indispensable. In the present study the multi criteria analysis of the fan, a decisive component in modern aero engines, is examined. In particular the interaction of the fan blades with the fan casing is analyzed and an appropriate design approach including automatic optimization is used. As one part of the disciplines conjunction an automated aeroacoustic approach is realized. The aerodynamic and acoustic fitness functions and constraints are based on Reynolds-Averaged Navier-Stokes (RANS) simulations of the fan stage. A fast analytical prediction tool for fan noise, PropNoise, which has been under development since recent years and already validated on several test cases, is used. Preliminary studies have shown that the flow in the rotor tip region is a major contributor to the broadband noise emission. Based on this, the optimization process focuses on the variation of the casing contour around the fan blades. The impact of the modified flow field in the rotor tip region concerning the aeroelastic behavior is also investigated. As aeroelastic evaluation requires a high level of know-how and is very time consuming, it is linked to the optimization process chain by a discrete evaluation of selected members. This allows a simultaneous adjustment of the design in case of aeroelastic issues. Furthermore, the impact of the fan modifications regarding the overall engine performance is evaluated. Off-design cycle calculations allow incorporating such detailed studies in a global engine optimization