Abstract
A design for a new high lift system that features a morphing wing leading edge “droop nose” has the potential to generate high lift coefficients whilst mitigating airframe noise emissions. This seamless, continuous, and stepless flexible droop nose potentially offers improvements to stall and compressor requirements for an internally-blown active Coandă trailing edge flap. A full-scale, span-trimmed three-dimensional droop nose was manufactured and ground-tested based on results obtained from new design synthesis tools. A new component of the droop nose is the hybrid fiberglass-elastomeric skin that is tailored in stiffness to meet morphing curvature requirements and spanwise bending resistance. A manufacturing concept of the novel skin was established that led to an adequate manufacturing quality. The skin was driven and supported by two optimized kinematic ribs and conventional actuators and overall shape results show good agreement apart from the region closest to the leading edge. Kinematic trajectory measurements showed that the kinematics met the target trajectories well, with and without the influence of the skin, and it was deemed that the error in curvature is due to a higher than expected skin stiffness in the hybrid layer. Calculated actuator torque levels and strain measurements corroborate this inference. The lessons learned show that means of adjustment post-assembly are needed, and a reduction of torque, energy and a better curvature distribution may be achieved if the skin at the spar junction is allowed to move relative to the main wing. Careful aerodynamic, structural, actuation and manufacturing trade-off studies would be needed to determine the overall performance benefit.
Highlights
In recent works, it has been shown that a new high-lift system capable of quietly generating very high lift coefficients can potentially address some of the current challenges in aviation [1,2,3]
The leading edge device is a gapless flexible morphing droop nose that undergoes a large shape and curvature transformation (90 deg. camber line variation at the leading edge line) between clean and drooped configurations. It has been shown in [2,3,4] that this type of leading edge device is mandatory for such a high lift system in contrast with current slats or even rigidly moving droop noses
The morphing droop nose protects against aerodynamic stall given the high flow turning produced by the trailing edge devices and produces a pressure-gradient that could reduce the internal compressor requirements, whilst mitigating airframe noise generation that would be borne from gapped-devices
Summary
The high-lift system under consideration, being key in addressing the above challenges, is shown in Figure 2 and features a simple trailing edge flap with 65 deg. Camber line variation at the leading edge line) between clean and drooped configurations. It has been shown in [2,3,4] that this type of leading edge device is mandatory for such a high lift system in contrast with current slats or even rigidly moving droop noses. The morphing droop nose protects against aerodynamic stall given the high flow turning produced by the trailing edge devices and produces a pressure-gradient that could reduce the internal compressor requirements, whilst mitigating airframe noise generation that would be borne from gapped-devices
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