Role of Figures of Merit in Design Optimization and Technology Assessment

Jensen, S. C.; Rettie, I. H.; Barber, Edward A.

doi:10.2514/3.57468

Cited by 44 publications

(11 citation statements)

References 1 publication

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“…However, this technique does not guarantee that the thrust is equal to drag at cruise conditions, or that the calculated payload mass will meet mission requirements. Additionally, a low take-off mass is desired in order to minimize the total costs associated with the construction and operation of an actual HST vehicle [22]. For these reasons, application of optimization methods is required in order to generate practical results.…”

Section: Optimization Approachmentioning

confidence: 99%

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Multidisciplinary Design Optimization of Hypersonic Transport Configurations using Waveriders

Lobbia

Suzuki

2014

19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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A multidisciplinary design method for generating hypersonic transport (HST) configurations using waveriders is presented. Waveriders generated from osculating cone flowfields are used as the initial platform for the vehicle, and various modifications required for the mission are implemented. The propulsion system assumes the use of ramjets and lowbypass turbofans with hydrocarbon fuel. Empirical estimates of the structure weight of the configuration are combined with a method for calculating the total mission fuel requirements. Design optimization is performed using both evolutionary and hill-climbing techniques to allow a thorough search of the design space; optimization variables include freestream, geometric, engine design, and mission parameters. A baseline 250 seat configuration was generated, and demonstrated the ability of the model to create optimized designs that meet mission requirements. Trades were conducted to investigate mission assumption and modeling sensitivities, and it was found that the total HST mass saw only small changes due to payload size, cruise range, and ramjet combustion efficiency assumptions. However, applying additional margin to the mass sizing technique resulted in a more than 40% increase in total mass, which indicates a relatively high sensitivity to mass estimating errors. Finally, a top level comparison with a modern subsonic transport indicated that, although HSTs can cut travel time by one-fifth, they will have to overcome economic challenges associated with higher total mass and lower overall fuel efficiency. Nomenclature ‫ܣ‬= area ‫ܣ‬ ௫ = max cross-sectional area a, b, c, d, e, f, g = objective function weighting constantsat constant pressure ݂ = fuel/air ratio ‫ܦ‬ = drag ‫ܦ‬ = hydraulic diameter ‫ܧ‬ ௐ = wave drag efficiency factor ℎ = height (i.e. thickness); enthalpy ‫ܫ‬ ௦ = specific impulse ݈ = length ‫ܮ‬ = lift 1 AIAA Member 2 Professor, Department of Advanced Energy, 5-1-5 Kashiwanoha; Senior AIAA Member Downloaded by CORNELL UNIVERSITY on July 30, 2015 | http://arc.aiaa.org | ݉ = mass; slope used in cubic spline interpolation (if selected) ‫ܯ‬ = Mach number ݉ሶ = mass flow rate ݉ ௨ = fuel mass ݉ ௬ௗ = calculated payload mass ݉ ௬ௗ ᇱ = desired payload mass ݉ ௦௧௨௧௨ = structure mass ݉ ௧௧ = total mass at take-off ݊ = population size for genetic algorithm optimization ܰ = number of variables in optimization ‫‬ = pressure ‫ݍ‬ = dynamic pressure ܴ݁ = Reynolds number ܶ = thrust; temperature ‫ܥܨܵܶ‬ = thrust-specific fuel consumption ‫ݓ‬ = width ‫ݔ‬ = streamwise direction coordinate ‫ݕ‬ = vertical direction coordinate ‫ݖ‬ = spanwise direction coordinate ∆ℎ = heat of reaction ߚ = shock wave angle ߟ = combustion efficiency ߛ = ratio of specific heats ߶ = equivalence ratio ߠ = rational function parameter; angle ߠ ̅ = boundary layer momentum thickness parameter Subscipts 0 = stagnation conditions 0-10 = station numbers in engine analysis ܽ = air ݂ = fuel ‫ݐݏ‬ = stoichiometric conditions ‫ܧܶ‬ = trailing edge location (i.e. baseplane) ∞ = freestream conditions

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Section: Optimization Approachmentioning

confidence: 99%

“…The take-off mass of a vehicle is frequently an indication of the total life cycle cost of the aircraft [22], thus estimation of these values can provide an indication of the overall economic viability of a design.…”

Section: Vehicle Mass Sizingmentioning

confidence: 99%

Multidisciplinary Design Optimization of Hypersonic Transport Configurations using Waveriders

Lobbia

Suzuki

2014

19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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“…Various goals can be considered when designing an air vehicle [11,12], with an appropriate definition of the objective function for each goal. Possible goals may be minimum takeoff gross weight (TOGW), minimum fuel/emissions, and maximum lift-to-drag ratio.…”

Section: Tbw Problem Statementmentioning

confidence: 99%

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

Gur

Schetz

Mason

2011

Journal of Aircraft

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This paper describes a study of the effects of several key aerodynamic considerations on the conceptual design of minimum-fuel/emissions, long-range transport, transonic, 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 a multidisciplinary optimization process, which takes into account both aerodynamic and structural considerations. This 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 two-dimensional lift coefficient, 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 propulsion apparatus. All of these studies illustrate the large potential of the truss-braced wing along with additional dragreduction technologies, which may substantially decrease the fuel weight and vehicle emissions.

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“…A key to the successful use of such methods is the selection of a suitable objective function(s) [2,3,12]. Many studies use minimum takeoff gross weight (TOGW) as a surrogate for cost combining capital cost and operating cost.…”

mentioning

confidence: 99%

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

Shirley

Schetz

Kapania

et al. 2014

Journal of Aircraft

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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 wingmounted engine truss-braced wing configuration, where the pseudo-Pareto front almost became an asymptote to a lift/drag ratio of ∼45. Also, one can look across all the configurations and compare attractive designs from each to search for an overall best aircraft design.

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Role of Figures of Merit in Design Optimization and Technology Assessment

Cited by 44 publications

References 1 publication

Multidisciplinary Design Optimization of Hypersonic Transport Configurations using Waveriders

Multidisciplinary Design Optimization of Hypersonic Transport Configurations using Waveriders

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

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

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