Design of short intakes for ultra-high bypass engines: preliminary exploration at fixed incidence

Short inlet designs for ultra-high bypass engines exhibit a stronger fan/intake interaction. The reduced flow straightening capability exposes the fan to increased incidence effects and radial flows, altering its stability margin, efficiency and thrust. On the other hand, the fan suction allows the intake to operate at high incidence without separation. The impact of the inlet design parameters for a short duct is investigated using a coupled fan model based on a body force method. Their influence on total pressure losses and distortion levels at the take-off rotation point is evaluated on a global and a local basis, to highlight their combined and individual effect. The analysis identifies suitable ranges for optimal metrics values, providing a starting set of variables to be considered for the design of shorter intake ducts.