In the EU project TURANDOT, researchers at Graz University of Technology's Institute of Thermal Turbomachinery and Machine Dynamics (ITTM) investigated a sharkskin-like coating (riblets) for engine blades. This makes aircraft more economical, cheaper and quieter.
The larger and slower the fan (the fan wheel at the front of the engine), the more efficient and quieter the engine. This is driven by the low-pressure turbine, which therefore also has a larger diameter. The larger this diameter is, the shorter and steeper ("more aggressive") the transition duct between the high-pressure and low-pressure turbine must be. A transition duct that is too short could cause a stall, resulting in a loss of pressure and thus reduced engine performance.
The project team has now been able to prove that a so-called riblet coating greatly improves the efficiency of the transition channel and thus the engine performance. This coating was developed by project partner bionic surface technologies. It is a sharkskin-like surface coating, consisting of nano- and micro-structured grooves (riblets), which reduces friction on the duct wall and thus the flow resistance. With this, the pressure loss in the transition duct can be reduced by up to 5 %, regardless of its geometry, which means considerable fuel savings. The engine manufacturer General Electric Aviation (Cincinnati, USA) now wants to use the developed technology in a new generation of engines.
