The importance of unmanned aircraft systems (UAS) is rapidly increasing in various fields of aerospace development. Modern military UASs require a compact full-engine integration to optimize the use of the limited installation space and to prevent radar reflections from the easily detectable fan. These goals are commonly achieved by highly bent intake ducts or by the position of the intake’s inlet section. However, an inconvenient position and an extremely compact intake shape can lead to strong flow inhomogeneities and influence the engine’s stability and performance. Previous studies at the Institute of Jet Propulsion (IJP) have focused on evaluating the flow distortions at the isolated intake duct. The effect of the external flow and the aircraft configuration was neglected. In this work, the impact of external flow on the intake aerodynamics for different aircraft intake configurations at various flight conditions, such as angles of attack or flight Mach numbers, is investigated. A generic remote carrier is used as a virtual test platform on an overall mission that covers most of the aircraft’s flight envelope. The intake systems investigated comprise strongly bent ducts and flush-intake configurations. Different flow inhomogeneities parameters allow detailed consideration of diverse aerodynamic phenomena along the intake and their impact on the Aerodynamic Interface Plane (AIP) flow. As an example, one parameter is the distorted mass flow fraction based on the average deviation from the mean total pressure. Traditional turbomachinery distortion parameters such as the DC60 or SC60 are also analyzed to allow a comparison with existing engine integration studies at the IJP and the open literature. In addition, these evaluation capabilities also enable the use of different flow distortion parameters as input to the IJP’s Engine Mission Simulation System (EMSS) to study the effects on compressor behavior and engine performance (see ASME Turbo Expo 2024 by J. Remiger). For this study, the steady-state RANS simulations of the entire remote carrier were performed using ANSYS CFX flow solver. Initial low-fidelity simulations were done using the EMSS to calculate the flight conditions and, therefore, the boundary conditions for the CFD setup. The study reveals that the external flow significantly influences the flow inhomogeneities in the intake and, therefore, cannot be neglected by evaluating an applicable flight case of a coupled aircraft and intake system. It turned out that a change in the angle of attack and the axial positioning of the intake caused a significant variation in the inflow condition. This major impact is noticeable in the distortion parameters along the intakes and leads to a sharp change in the distortion pattern at the AIP.     «

The importance of unmanned aircraft systems (UAS) is rapidly increasing in various fields of aerospace development. Modern military UASs require a compact full-engine integration to optimize the use of the limited installation space and to prevent radar reflections from the easily detectable fan. These goals are commonly achieved by highly bent intake ducts or by the position of the intake’s inlet section. However, an inconvenient position and an extremely compact intake shape can lead to strong...     »