The INFRa Rig: Validating High-Fidelity Fan-Intake Simulations in a Crosswind Facility

Abstract

Abstract. This study addresses the numerical and experimental investigation of a low-pressure ratio fan at takeoff representative operating conditions including crosswind. It explores this by qualifying high-fidelity numerical setups of a crosswind facility and by validating the numerical results with test data. In this work, we introduce the integrated Nacelle fan rig assembly (INFRa) fan, which represents a downscaled state-of-the-art propulsor with a cruise fan pressure ratio of 1.37, targeting a bypass ratio of 10-12. In the numerical study, we investigate the fan-intake interaction with two axisymmetric flight intakes under clean inflow conditions. The main difference is the different area ratio between the intake throat and the fan inlet. However, the average intake-induced variations at the fan inlet have only a small effect on the fan performance. Furthermore, the numerical data of one intake are validated by experimental data. In a subsequent step, the propulsion unit is subjected to a 30 knot crosswind. The crosswind leads to a strong acceleration of the flow around the intake highlight area. This leads to unsteady flow separation, which reattaches before the flow enters the fan blade. It is found that the frequency of the separation bubble is 25.2% (CFD) or 28.5% (experiments) lower than the first engine order, respectively. The flow separation results in a highly distorted inflow to the fan. Therefore, the fan performance varies along the circumference. The distinct frequency of the separation bubble, as well as the fan performance data are validated with experiments.