A review of installation effects of ultra-high bypass ratio engines

The adoption of ultra-high bypass ratio (UHBPR) engines has been long recognised to bring about reduction of specific fuel consumption and noise emission. In the need to fulfil ambitious environmental targets and mitigate the aviation sector impact, they represent a smoother technology change, compared to futuristic aircraft designs featuring electric, distributed and boundary layer ingesting propulsion. However, the challenges related to UHBPR adoption can prevent a real system performance improvement, due to interdependent counteracting factors and enhanced interference between engine and airframe. This paper reviews the installation effects on underwing-mounted UHBPR turbofan engines, first presenting the cycle design studies and how they are affected by considering integration. The advancements in nacelle components modelling and optimisation are then reviewed, where new numerical models, statistical methods and optimisation algorithms are employed to tackle the inherently multi-objective problems. The computational estimation of installation effects and the studies on optimal engine position are also presented, highlighting the overall effect on the aerodynamic characteristics. Finally, the wind tunnel tests using powered engine simulators are discussed. The tools developed to quantify the thrust and drag figures of installed propulsors and obtain indications on their best underwing location now allow quite accurate estimations, both in numerical and experimental simulations. The higher level of interaction and the increased mutual sensitivity of engine operation and wing flow field, however, suggest the need to elaborate closely coupled methods to correctly replicate these effects and an assessment of current wind tunnel practices for the design and operation of powered engine simulators