JAXA is undertaking research to reduce fric tion drag on wings and improve the fuel efficiency of aircraft. It is known that an effective way to reduce friction drag is a natural laminar flow design that maintains laminar boundary-layer flow over the surfaces of the wing. However, because insects get stuck to the leading edge of aircraft wings ...[more]
- December 22, 2014
- Verification of the effect of applying Krueger flaps
Environmental performance criteria for passenger aircraft have become more and more demanding, including considerations such as less fuel-consumption, low airport community noise, and low exhaust gas emissions, including those of nitrogen oxides (NOx), with increased air traffic volume. Satisfying these demands would give Japanese aircraft and aero engine manufacturers technological superiority, enabling them to compete more effectively on the global stage in developing the next generation of passenger aircraft.
To provide solutions for such strong demands for environmental performances, we conduct R&D of “Eco-wing technology”, which consists of developing “Airframe drag reduction technology” and “Composite structure design technology”, as well as “System evaluation technology” to evaluate the effects of those technologies.
Targeting small-size aircraft with capacity of 100–150 passengers, we aim to achieve the following two main goals related to the environmental performance of airframes.
- A) Aircraft will be at least 30% more fuel efficient than existing aircraft by development and application of the following technologies:
- (1) 20% reduction of structural weight through establishment of structural design technologies using composite materials
- (2) 15% reduction in specific fuel consumption (SFC) during cruising through “aFJR” project, which conducts demonstration of next-generation advanced Fan Jet Research
- (3) 7% increase in the lift-to-drag (L/D) ratio during cruising through application of advanced low-drag technologies
We also aim to evaluate the effects of the technologies presented above.
B) Airport community noise shall be reduced by 20 dB to satisfy the requirements of ICAO Chapter 4. This goal can be achieved through R&D of “green engine technology” and “flight demonstration of airframe noise reduction technology (FQUROH)” because we expect to reduce noise caused by engine/airframe interference by combining findings from these research activities.
For further noise reduction we are developing a method to calculate and verify shielding effects of engine noise by airframe arrangement.
Airframe drag reduction technology
We shall develop technologies to reduce aerodynamic drag by 7% through a combination of the following aerodynamics and structural approaches. Then we verify these technologies through flight demonstrations.
- (1) By adopting a design method that suppresses the boundary layer transition, increase laminar flow area on the airfoil, and thereby reduce friction drag
- (2) By developing a particular riblet pattern that is effective at reducing the turbulence frictional resistance, and by producing and applying an easy-to-coat method that can create an optimum riblet surface on the airframe, reduce friction drag in the turbulence boundary layer.
- (3) By optimizing the lift distribution of the main wing with morphing flap surfaces and wingtip devices, reduce the induced resistance.
Composite structure design technology
With the aim of achieving 20% reduction in total weight compared to that of a metallic material structure, we promote R&D of lightweight composite material structure design technology, including technical verification using a full-scale main wing structure, by pursuing the following objectives.
- (1) Improving structural design technology of composite material, such as improving design accuracy at high load density structure areas, complicated curved structure areas, and ply drop-off areas, and acquiring technologies to produce composite material plates having uniform thickness
- (2) Promote development of multilayer technology that enables production of a thinner layer and which increases efficiency in lamination in pre-preg processes, thereby supporting further improvement of (1) and (3)
- (3) Develop highly accurate structural analytical technology and its verification test that enables composite material structure design using minimum plate thickness with post-buckling design technology
Environmentally friendly aircraft system
We are developing tools to evaluate the aircraft performance improvement achieved by the technologies presented above.
An advanced method for engine noise propagation analysis is under development to predict engine/airframe interference and noise shielding effects with high accuracy, thereby enabling optimal design of airframe arrangements for low noise.
Furthermore, these tools are used to create new aircraft concepts such as Blended Wing Body (BWB), which might reduce fuel consumption by 50% and reduce noise around airports by 30 dB compared with results obtained for current conventional tube-and-wing aircraft.