Propulsion/airframe Integration Study of an Ultra High Bypass Ratio Turbofan and a Slotted, Natural-Laminar-Flow Wing

Next-generation aircraft concepts such as the transonic truss-braced wing, integrate ultra-high-bypass-ratio turbofan engines and natural-laminar-flow wings. Slotted, natural-laminar-flow technology shows the potential to further reduce fuel burn. Currently, propulsion/airframe integration effects between the engine and wing are not well characterized. A representative N+3 turbofan engine model was created by scaling a NASA reference engine to the fan diameter and cruise thrust requirements of the transonic truss-brace wing. NASA's OVERFLOW computational fluid dynamics code was used to characterize a semi-infinite slotted, natural-laminar-flow wing and a representative N+3 turbofan both installed and in isolation to quantify the influence of propulsion/airframe integration on interference drag. Four engine positions were investigated: trailing-edge/over-wing, leading-edge/over-wing, leading-edge/under-wing, and trailing-edge/under-wing. It was determined that leading-edge/over-wing and trailing-edge/under-wing mounted nacelles created similar or less interference drag than conventional leading-edge under-wing nacelles at cruise conditions. The trailing-edge/under-wing had the minimum interference drag of all configurations considered. These findings show the need for full 3-D wing integration testing to accurately place the engine.