Truss-braced Wing Configuration Research Articles

Numerical Investigation of Bio-Aviation Fuel: Dubai’s Future Perspective

As part of the United Arab Emirates’ and the world’s aviation goal of reaching net-zero greenhouse gas emissions by 2050, this paper studied the potential of successfully implementing both biofuel “drop-in” alternatives and aerodynamically efficient configurations to decarbonize the aviation industry. By investigating various proposed designs through a PUGH analysis, it was concluded that the optimum design has a Transonic Truss-Braced Wing configuration and runs on 60% biofuel. Although the design stipulates a 1.3% increase in weight, this does not negate the reduction in emissions and fuel consumption. This study also explored the various types of biofuels and found camelina seeds to be the best choice. The effects of biofuels in comparison with Jet-A fuel were further deliberated in a fuel combustion simulation performed on the Ansys-Fluent software. The results of the simulation showed a reduction of 50% in carbon monoxide (CO) and 24% in carbon dioxide (CO2) emissions when burning camelina biofuel rather than Jet-A, making it an ideal alternative to those conventional jet fuels. A primary cost analysis of biofuel applications showed an increase of 453 USD (1653.18 AED) per passenger flying on board 100%-biofuel-powered aircrafts. Yet, considering the trend of the cost increase with the biofuel blend ratio, a solution may exist to the increased cost of biofuel-powered aircrafts.

Design of a slotted, natural-laminar-flow airfoil for commercial transport applications

Slotted, natural-laminar-flow (SNLF) airfoils are a novel aerodynamic concept that enable significant performance improvements over conventional, single-element NLF airfoils. The S207, SNLF airfoil has been designed using requirements derived from a transonic, truss-braced wing commercial aircraft configuration. The airfoil is designed for a cruise Reynolds number of 13.2×106 and it exhibits a drag divergence Mach number exceeding 0.71. At these conditions, low drag is predicted to occur between lift coefficients of 0.40 and 0.79. The S207 airfoil exhibits a range-based figure of merit nearly triple that of a turbulent airfoil representative of modern commercial transport aircraft. Slotted configurations also have benefits for low-speed, high-lift conditions representative of approach. The S207 airfoil exhibits a low-speed, maximum lift coefficient in excess of 2.1, and is limited by compressibility effects around the leading edge. Incorporation of this airfoil onto a transonic, truss-braced wing configuration shows strong potential for meeting mid- and far-term goals for reducing aircraft fuel/energy consumption.

Conceptual design and analysis of an affordable truss-braced wing regional jet aircraft

A regional, turbofan-powered, 72-passenger, transport aircraft with very high aspect ratio truss-braced wings is developed with an affordable methodology from an existing 52 passenger, conventional twin-turboprop aircraft. At first, the ration behind the selection of the truss-braced wing configuration is discussed. Next, the methodologies for the sizing, weight, aerodynamics, performance, and cost analysis are presented and validated against existing regional aircraft. The variant configurations and their design features are then discussed. Finally, sensitivity analysis is carried out to investigate the effects of the wing aspect ratio and engine bypass ratio on the aircraft weight, aerodynamics, and cost. It has been found that the penalties associated with the wing weight will prevent the acceptable realization of the high aspect ratio wing benefits, but when it is combined with the very high bypass ratio engines, a 17% reduction in the mission fuel weight is achieved. In contrast, the cost analysis has revealed that the application of higher aspect ratio wings in the truss-braced wing configuration may increase the development and maintenance costs. Consequently, with aspect ratios higher than 24, eventually, these costs may outperform the associated fuel cost reductions.

Minimum Induced Drag Conditions for Truss-Braced Wings

Traditional monoplane aircraft have been used for many decades. A promising improvement is represented by truss-braced wing configurations because studies have shown potential advantages in terms of fuel savings and overall efficiency. These investigations have been carried out in relatively complex multidisciplinary design and optimization computational frameworks, and thus some theoretical questions regarding the optimal conditions under which the induced drag is minimized need to be specifically addressed. This is achieved in this paper by extending the variationally derived theoretical model that the authors developed for nonplanar wings, closed systems, and multiwings to handle multiple closed paths (typical situation in the case of truss-braced wings) within the wing system. A regularization procedure, based on splines and preserving the continuity of the function and its first and second derivative, is introduced to address the geometrical corners. It is verified that, under optimal conditions, the actual value of the induced drag is a global minimum and that there is an infinite number of possible aerodynamic loads achieving the optimum. In some of them, the central part of the upper wing is more loaded, whereas in other cases, the lower wing and outer portions of the upper wing carry more aerodynamic forces. Finally, it is shown that a jury should be unloaded or at most have constant circulation to avoid penalty on the induced drag.

Aeroelastic Applications of a Variable-Geometry Raked Wingtip

This study investigates the effects of a variable-geometry raked wingtip on the aeroelastic behavior and the maneuverability of transport aircraft with very large aspect-ratio truss-braced wings. These truss-braced wing designs are obtained from the multidisciplinary design optimization environment presented here while minimizing the fuel burn of a double-aisle aircraft having a flight mission similar to that of a Boeing 777-200 long-range aircraft. The wingtip can be swept forward and aft relative to the wing by a novel control effector mechanism. Results show that a variable-geometry raked wingtip can be used to achieve required roll control by judiciously sweeping it relative to the wing at various flight conditions. It has an added benefit that it can also be used for flutter avoidance. Such benefits of the variable-geometry raked wingtip allow the operation of truss-braced wing configurations, which have up to 10% lower fuel burn than comparable optimized conventional cantilever wing designs. Without the variable-geometry raked wingtip, such configurations fail to meet the required flutter speed and roll control capability. The variable-geometry raked wingtip is thus an enabling technology for truss-braced wing aircraft and other large aspect-ratio configurations.

Comparative Assessment of Strut-Braced and Truss-Braced Wing Configurations Using Multidisciplinary Design Optimization

This paper presents a study of aircraft featuring truss-braced wing configurations that have been optimized for minimum fuel consumption using multidisciplinary design optimization. The investigation proceeds following an earlier Boeing Subsonic Ultra Green Aircraft Research study, which selected the truss-braced wing concept as the most promising of several concept vehicles. This comes from the fact that a significantly higher-aspect-ratio wing could achieve substantial reductions in induced drag but requires major structural changes to support such a large span. This problem was explored through the use of a multidisciplinary design and analysis environment implemented in ModelCenter®. Optimization was performed using ModelCenter’s Design Explorer and Darwin genetic algorithm optimizers. Using the multidisciplinary environment, a large multidimensional design space, featuring design variables spread across the major aircraft design disciplines, was explored. Configurations featuring a strut-braced wing and truss-braced wings with one and two juries were evaluated for different span limits. Subsequently, different laminar wing design options were investigated in conjunction with lift augmentation system options. The multidisciplinary optimization used for this investigation was able to produce candidate designs with the desired attributes and performance improvements while satisfying all relevant geometric and performance constraints.

Tradeoffs of Wing Weight and Lift/Drag in Design of Medium-Range Transport Aircraft

Wing design involves many compromises, but none more important than the one between aerodynamics, represented by lift-to-drag ratio, and structural weight. Multidisciplinary design optimization is used to compare the effect of configuration changes on wing weight and lift/drag ratio for 1) cantilever, 2) strut-braced, and 3) truss-braced wing aircraft for a medium-range, transonic, 162 passenger mission. Pseudo-Pareto fronts are generated to illustrate maximum lift/drag ratio compared to minimum wing weight. Lower lift/drag ratio aircraft have a shorter, more highly swept wing, with a change in taper at 75% semispan. Higher lft/drag ratio aircraft have much greater span and maximum chord at 33% semispan. To increase lift/drag ratio, both wing-weight and takeoff gross weight penalties must be paid. However, there are high lift/drag ratio designs with low wing-weight penalty that are clearly displayed by the pseudo-Pareto front. Fuel weight minima were found in the high lift/drag ratio and low wing-weight region of the pseudo-Pareto front for the truss-braced wing with both fuselage-mounted and wing-mounted engine configurations and for the cantilever configuration. An interesting pseudo-Pareto front was observed for the wing-mounted engine truss-braced wing configuration, where the pseudo-Pareto front almost became an asymptote to a lift/drag ratio of . Also, one can look across all the configurations and compare attractive designs from each to search for an overall best aircraft design.

Aerodynamic Considerations in the Design of Truss-Braced-Wing Aircraft

The paper describes a study of the effects of several key aerodynamic considerations on the conceptual design of minimum fuel / emissions, long range transport, truss-braced wing aircraft configurations. This unconventional configuration has a large benefit over conventional cantilever wing configurations. The truss system enables an increased aspect ratio with lower sweep, thickness ratio, and chords, thus exploiting natural laminar flow. The design problem is solved by an MDO process, which takes into account both aerodynamic and structural considerations. The paper contains several studies, each of which investigates the dependency of the design space on a specific aerodynamic parameter such as the extent of laminar flow on the wing, cruise Mach number, maximum cruise twodimensional lift coefficient, the supercritical characteristics of the airfoil, winglet influence, and intersection fairing design. In addition, various fuselage drag reduction technologies are investigated: fuselage relaminarization, surface riblets, tailless arrangements and Goldschmied apparatus. All of these studies illustrate large potential of the truss-braced wing along with additional drag reduction technologies, which may substantially decrease the fuel weight and vehicle emissions. The paper emphasizes the importance of appropriate wing section airfoils, which can satisfy various contradicting criteria of natural laminar flow, supercritical characteristics, high lift coefficient, and low drag coefficient. Finally, these studies illustrate the importance of fuselage drag reduction for a low induced drag, NLF aircraft like a truss-braced wing configuration.

Development of a framework for truss-braced wing conceptual MDO

The paper describes the development of a multidisciplinary design optimization framework for conceptual design of truss-braced wing configurations. This unconventional configuration requires specialized analysis tools supported by a modular and flexible framework to accommodate different configurations. While the previous framework developed at Virginia Tech was a monolithic Fortran-77 code, the need for more flexibility for complex truss-braced wing configurations was addressed by the development of this new framework, which is based on Phoenix Integration ModelCenterTM environment. The framework uses updated structural and aerodynamic design modules that enable a more general geometry definition. The new framework, thus, provides a foundation for future design concepts, especially multi-member truss-braced wing configurations. The fuel saving potential of these truss-braced wing configurations is presented by comparing different truss designs with gradually increased level of complexity.