Interaction Effects of Fan With Short Aero-Intake: A Multi-Objective Optimization Study With Modeling of Flow Coupling

The stronger coupling between the turbomachinery and the air inlet becomes more relevant in next-generation turbofan engines with low-pressure ratio fans and compact nacelles. This study presents a numerical investigation of the interaction between a transonic fan and a short aero-intake in terms of intake geometric design and fan modeling. The inlet design space is first explored in cruise and takeoff conditions, and the three-dimensional geometry is optimized in a multipoint and multi-objective formulation using a Bayesian solver to minimize the inlet distortion at takeoff and the total pressure losses in cruise. Flow coupling at high incidence is ensured through a body force model of the fan. The Pareto frontier highlights the conflicting nature of intake design between high incidence and high-speed performance. A selected individual from the Pareto is further examined by running unsteady full-annulus sliding-mesh simulations at a high angle of attack upon inlet separation. The detailed comparison of the flow field and the turbomachinery performance indicates an accurate reproduction of the inlet flow coupling through the body force model. Although lacking in fully replicating specific flow features near the tip of the blade, the simplified method allows reconstructing the blade response to inlet distortion and capturing the main flow structures. The study thus highlights the suitability of the adopted approach to simulate the mutual interaction between the fan and the inlet flow and provides an efficient method for the optimization of short-intake designs.