Dedicated to change
Aerodynamic efficiency as key enabler for flying greener.
With the thriving aviation industry and the ever-increasing air traffic, it is up to the aeronautical community to take responsibility by developing new and innovative technologies that are environmentally friendly.
One major field of research and development of environmental friendly aircraft is higher aerodynamic efficiency. The objective is to reduce the drag for the lift needed. Drag is the aerodynamic force that the engines have to overcome in order to propel the aircraft. Therefore, less drag results in less fuel consumption, which in turn reduces the CO2 and NOX emissions.
Various ideas and concepts exist, which potentially increase the aerodynamic efficiency of transport aircraft. The Holy Grail for aerodynamicists is the application of laminar flow control. Laminar flow occurs when a fluid flows in smooth parallel paths or layers with no disruption in-between. Its counterpart is turbulent flow, which is characterized by irregular fluctuations in all directions. For objects moving through fluids where the flow is turbulent, such as wings moving through air, the associated drag is up to ten times higher compared flow that is fully laminar.
Looking at the airflow around today’s conventional wings, a transition from laminar to turbulent occurs very close to the leading edge. Consequently, most of the wing area is covered with turbulent flow. Since the wings account for about 18% of the total aircraft drag, the application of laminar flow control will have a significant positive impact on aerodynamic efficiency.
For future mid- to long-range aircraft, Hybrid Laminar Flow Control (HLFC) is the most promising technology of all available flow control methods. By combining boundary layer suction over the first 15-20% of the wing chord with an airfoil design optimized for HLFC, the transition from laminar to turbulent is relocated downstream to 50% of chord length. This leads to a significant drag reduction in the order of 5-8% which in turn improves the fuel efficiency by 4-7% per flight. On a typical long-haul missions such as from Frankfurt (FRA) to Los Angeles (LAX), a distance of over 9000 km, today’s aircraft burn more than 60 tons of fuel. An aircraft with HLFC applied on the wings would require somewhere between 2 to 5 tons less, each flight. Scaled to annual values, HLFC is able to save 1 to 2 thousands of tons of fuel per aircraft. That translates to more than 3 thousand tons of CO2 saved.