Engines with high bypass ratio are more efficient than those with a smaller bypass ratio. However, the increasing nacelle diameter going along with this modification poses challenges for aircraft designers, as compliant with ground clearance regulations requires a close wing-engine coupling.
To avoid collision with the engine nacelle during take-off and landing a partial cut-back of the leading edge devices of a commercial passenger airplane wing is inevitable.
The problem being addressed in the INAFLOWT project is the local flow separation (and hence local lift reduction) due to the close coupling of the promising ultra high-bypass ratio engine to the wing and interference with its leading-edge high lift system.
This project is important to society since the local flow separation reduces the overall efficiency of the airplane in the takeoff and landing phase. On the other hand, the use of ultra-high-bypass-ratio engine is a promising way for reduction of fuel consumption and reduction of environmental footprint of air transportation.
The overall objectives of the project are to overcome the local flow separation by means of applying innovative active flow control technology. This technology, developed by the 5 teams of researchers and validated by both extensive computational fluid mechanics and two scales of wind tunnel testing at , is aimed to solve the local boundary layer separation at low energetic cost and low mass flow compared to the current state-of-the-art.
The chosen AFC method uses steady suction through a series of holes placed around the 1.5% chords location on the inboard side of the engine pylon. This location has been chosen based on CFD findings and validated experimentally in the small scale test.
Next, pulsed blowing from 4-6 span locations was added using a fluidic oscillator that is part of the SaOB actuator, placed around 12% chords of the same region. Both AFC locations were chosen to comply with existing AFC panels on the large scale model. Significant lift recovery and a certain degree of drag reduction was obtained by the efficient combination of the two AFC methods.
Comprehensive series of CFD simulations were conducted to predict the effects of steady suction and pulsed blowing alone and in combination on the large scale model.
Two scales of the SaOB actuator array were adapted, 3D printed and tested. Performance goals were met and an array was printed at TAU along with AFC panels and existing flow distribution system and sent to TSAGI for testing.
Baseline and AFC tests began at TSAGI T-101 large scale tunnel during Dec-2019. Preliminary encouraging result were obtained but after 11 runs the WT broke. Due to the Pandemic tests resumed only on Sep-21 and test plan was completed.
The final results show a good lift recovery due to the combination of steady suction and pulsed created by a six-synchronized SaOB array. The results correspond well and show superiority above to those of the AFLONEXT project, but using less that half the mass flow rate.
More importantly, the project demonstrated the capability to design, develop and apply an innovative AFC method, using two scales of wind tunnels testing, comprehensive steady and unsteady CFD and show good agreement between all components of the research project.
A series of publications has been presented in major European and world conferences and are prepared for Journal submissions.
