The INFRa Rig: Experimental and Numerical Investigation of Fan Intake Interaction Under Crosswind Conditions

Abstract Crosswind significantly impacts the stability and operability of turbofan engines, yet experimental data on large-scale, coupled propulsion systems under such conditions is limited. This study introduces the INFRa rig, a test platform designed to investigate future Ultra High Bypass Ratio (UHBR) propulsion systems under varying operational conditions. The INFRa fan is a down scaled, state-of-the-art turbofan with a cruise fan pressure ratio of 1.37 according to a bypass ratio of 10–12, coupled to a short axisymmetric intake (L/D = 0.36). The coupled propulsion system is tested across a range of crosswind velocities (0–38 knots) and power settings. The intake aerodynamics of this coupled system are compared to those of an aspirated, smaller-scale intake without fan coupling, to evaluate the fan’s impact on intake performance. Additionally, the effect of varying crosswinds on fan stage performance is analyzed, highlighting unsteady flow separation in the intake that, depending on crosswind intensity, reattaches before the AIP. The separation bubble oscillates at a frequency approximately 30% below the first engine order. Unsteady RANS simulations conducted at takeoff speed and 30 knots crosswind support the experimental findings, revealing that the fan experiences a non-homogeneous work input and stagnation pressure rise. Overall, experimental and numerical data show qualitatively good agreement, with some discrepancies in capturing the separation/reattachment process on the intake’s windward side.