Supersonic Civil Transport Research Articles

Multipoint Aerodynamic Shape Optimization for Subsonic and Supersonic Regimes

The second generation of supersonic civil transport has to match ambitious targets in terms of efficiency to be economically and environmentally viable. Computational fluid dynamics-based design optimization offers a powerful approach to address the complex tradeoffs intrinsic to this novel configuration. This approach is applied to the design of airfoils and wings at both supersonic cruise conditions and lower-speed, off-design conditions. Single and multipoint optimizations are performed to minimize drag over an ideal supersonic aircraft flight envelope and assess the influence of physical and numerical parameters on optimization accuracy and robustness. To obtain more favorable design tradeoffs between different flight regimes, morphing leading- and trailing-edge capabilities are introduced and their benefits are quantified against fixed-wing shapes. The optimized layouts outperform baseline supersonic reference designs over a range of flight conditions, with drag reductions from 4 up to 86% for airfoils and between 24 and 74% reductions relative to a reference wing. The results demonstrate that the proposed approach enables the fast and effective design of highly efficient wings, capturing nonintuitive tradeoffs and offering more in-depth physical insight into the optimal layouts.

Take-off thrust and noise control for supersonic civil transport engines

Take-off thrust and noise control for supersonic civil transport engines

Supersonic wing-body wave drag co-ordinated optimisation based on FCE methodology

AbstractWave drag reduction is important for the aerodynamic performance optimisation of supersonic cruise aircrafts, such as the supersonic civil transport and the supersonic cruise missile. In this paper a method of the supersonic wing-body wave drag optimisation, the wave drag co-optimisation based on far-field composite elements (CoFCE), is proposed based on class-shape-transformation (CST) parameterisation. Wave drag optimisation cases of a supersonic civil transport wing-body are presented, including the optimisation results and computation cost analyses. It is suggested that the supersonic wing-body wave drag can be significantly reduced by the proposed method with relatively small numbers of design parameter. In the optimisation case presented in this paper a 45% wave drag reduction is achieved. The wave drag optimised configuration also achieved significant lift to drag ratio improvements in small angles-of-attack supersonic cruise flight conditions.

Supersonic Wing–Body Two-Level Wave Drag Optimization Using Extended Far-Field Composite-Element Methodology

The wave drag is an important factor that affects the supersonic flight efficiency and is closely related to the aircraft’s cross-sectional area distribution. A reasonable cross-sectional area distribution determines supersonic aircraft wave drag reduction. In this paper, an exploration of the supersonic aircraft wing–body shape parameterization using the class-shape-refinement-transformation technique and the method of extended far-field composite-element (EFCE) supersonic wing–body wave drag optimization are proposed. The method was applied to a supersonic civil transport wing–body shape optimization, yielding a 40.5% reduction of wave drag coefficient. In this way, the goal of reducing the wave drag in sufficient precision without any lift penalty was achieved. The EFCE wave drag optimization method is available in the conceptual design process of supersonic cruise aircraft to achieve high lift-to-drag ratio characteristics in supersonic flight conditions.

Supersonic Bi-Directional Flying Wing Wave Drag Optimization Based on Alternative Form of CST Method

Bi-directional Flying Wing (BFW) is a new supersonic civil transport shape concept that aims to meet the conflict requirements of high speed cruise and low speed take-off/landing missions. In this paper the Class-Shape-Transformation (CST) shape parameterization method is modified to represent the BFW shape, and new basis functions suitable for the BFW airfoil representation are constructed. The Far-field Composite Element (FCE) wave drag optimization is performed on both the flat bottom and symmetric BFW configurations, and the drag reduction effects and result precision are surveyed. It is suggested that significant wave drag reduction can be achieved by the FCE optimization for both the flat bottom and the symmetric BFW configurations. The wave drag coefficients with sufficient precision can be obtained in the FCE optimization of the symmetric configuration; while the FCE optimization results of the flat bottom one are not accurate enough.

Nonlinear acoustic wave propagation in inhomogeneous moving media.

Extensive theoretical analysis, numerical studies, and both large-scale and laboratory-scale experiments have been dedicated to the problem of shock wave propagation in air during recent years. The current interest is motivated by supersonic civil transport which is necessarily affected by problems of sonic boom propagation in the atmosphere. The high-amplitude shock wave generated by a supersonic aircraft propagates through the atmosphere toward the ground and generates an acoustic field with non-uniform pressure distribution. Temporal characteristics and spatial structure of the sonic boom are influenced by aircraft trajectory, nonlinear effects, and diffraction and scattering by inhomogeneities. We review recent results from various teams based on a generalized KZK-type equation that includes the effects of a moving inhomogeneous media. Statistical analysis of the numerical solutions is performed, and the results are compared to experimental data obtained in the controlled laboratory-scale experiments conducted in the Ecole Centrale de Lyon anechoic wind tunnel.

Improvement and verification of low-speed aerodynamic characteristics of a supersonic civil transport aircraft

For supersonic civil transport aircraft, the low-speed aerodynamic characteristics form an important factor in its operational capabilities and in its economic viability. Low drag is a prerequisite to meet the present and future noise and emissions requirements. The application of concepts for leading-edge devices aiming at an improvement of low-speed aerodynamic efficiency is investigated. From computational analysis of a series of leading-edge flap designs, the two most promising devices are selected for experimental verification, viz. a doublehinge leading-edge flap and a deep-hinge leading edge flap design. In the course of comparing experimental and computational results, discrepancies are observed that are satisfactorily dealt with by adding the wind tunnel struts and the strut-wing connections in the computational analysis. Reynolds number extrapolations from wind tunnel scale to full-scale are obtained using computional fluid dynamics (CFD). It is concluded that the design approach based on CFD has significantly contributed to the success of configuration development, meeting the target efficiency improvement. Furthermore, the influences of geometrical details that differ in the design phase and the validation phase have been assessed.

A 2xxx aluminum alloy crept at medium temperature: role of thermal activation on dislocation mechanisms

Fuselage skin of the future supersonic civil transport aircraft requires a material resistant to long-term creep at temperatures ranging from 100 to 130 °C. A candidate is the 2650 aluminum alloy which presents such properties at relatively high temperatures (130°C=0.43Tmelting). From an accelerated creep test conducted at 150 °C under a 280 MPa load and subsequent observations of the dislocation microstructures by transmission electron microscopy, the role of thermal activation on dislocation mechanisms is analyzed. It appears that thermal activation favors cross-slip activity and allows dislocations to glide in non-close-packed planes, namely the {0 0 1} planes. This is the first time that evidence of primary {0 0 1} glide is reported. Associated to a strain-assisted decrease of the precipitate density, thermal activation softens the material and seems to contribute to the acceleration of the strain rate (tertiary stage) by facilitating bypassing of precipitates and the production of mobile dislocations. The different creep stages are explained in terms of individual dislocation mechanisms and not by referring to the evolution of dislocation substructures.

A 2xxx aluminum alloy crept at medium temperature: role of thermal activation on dislocation mechanisms

Fuselage skin of the future supersonic civil transport aircraft requires a material resistant to long-term creep at temperatures ranging from 100 to 130 °C. A candidate is the 2650 aluminum alloy which presents such properties at relatively high temperatures ( 130 °C =0.43 T melting ). From an accelerated creep test conducted at 150 °C under a 280 MPa load and subsequent observations of the dislocation microstructures by transmission electron microscopy, the role of thermal activation on dislocation mechanisms is analyzed. It appears that thermal activation favors cross-slip activity and allows dislocations to glide in non-close-packed planes, namely the {0 0 1} planes. This is the first time that evidence of primary {0 0 1} glide is reported. Associated to a strain-assisted decrease of the precipitate density, thermal activation softens the material and seems to contribute to the acceleration of the strain rate (tertiary stage) by facilitating bypassing of precipitates and the production of mobile dislocations. The different creep stages are explained in terms of individual dislocation mechanisms and not by referring to the evolution of dislocation substructures.

Comparisons of Open-Hole Fatigue Strength Characteristics between Candidate High Temperature Polymer Matrix Composites for the Next Generation Aircraft(Composite 1)

One of critical technological issues for the realization of the supersonic transportation(SST) is to ensure the long-term high temperature structural integrity of advanced polymer matrix composite system. This research has been conducted as a part of long-term durability performance of composites and structures in Japan Supersonic Research Program for 2^<nd> Generation Supersonic Civil Transport. The final goal is to achieve through long-term and short-term tests under conditions simulating SST flight, development of associated predictive and accelerated test methods, and assessment of durability performances for design. This paper summarizes open-hole fatigue behavior for the interesting and candidate high temperature polymer matrix composites.

Creep resistance of aluminium alloys for the next generation supersonic civil transport aircrafts

Characterization of the creep resistance of 30 newly developed aluminium alloys is made for structural applications of the next generation Supersonic Civil Transport Aircafts (SCT). These materials refer to the 2xxx, 6xxx and 8xxx aluminium alloy series. Creep behaviour is ranked to the usability and applicability of the alloys according to performance. A procedure is developed for validating the criteria of extrapolating creep data.

Variable cycle jet engines for a Mach 2·7 supersonic civil transport

AbstractThe aim of the work outlined in this paper is to compare three different variable cycle jet engine concepts for future SSTs. These engines are: the turbofan-turbojet, the mid-tandem fan engine and the double bypass engine. The comparison is carried out on the basis of unin-stalled and installed performance, handling and sizing issues.This preliminary analysis compares SFC, size, variable geometry and cycle changes for each engine. The installed performance was estimated by calculating the air friction, the pre-entry and the afterbody drags, together with the wave drag due to the shock waves. A sizing calculation was carried out for the whole nacelle. The uninstalled and installed fuel bill, for two standard missions, is also estimated.These preliminary results indicate that the turbofan-turbojet and the mid-tandem fan engines are quite similar in terms of general suitability. The mid-tandem fan appears to be an attractive proposition from the point of view of sizing, however, this comes with a small penalty in fuel consumption. The present double bypass engine was found to be the least attractive for the application, although the differences are small.

超音波旅客機の環境適合性に関する一考察

The research of the next generation supersonic civil transport is being conducted extensively in a few countries. The major environmental problems of the supersonic civil transport are sonic boom, noise and engine emissions. In this paper, we evaluated potentialities of future supersonic civil transport from a viewpoint of sonic boom and airport noise. We defined three factors: boom factor, the degree of the influence by the sonic boom, CT factor and C2T factor, both representing the cost and time saving effects. The calculation results show that the supersonic civil transport had reasonable values of CT and C2T with acceptable range of boom factor in the pacific oversea flight.

The technical aspects of supersonic civil transport aircraft

The paper discusses those technical aspects of a supersonic civil transport aircraft which peculiarly distinguish it from conventional subsonic civil aircraft. The physical, economic and ecological environments in which the supersonic transport must operate are considered and the main stepping stones to the development of the supersonic transport are traced. It shows that the basic differences between the supersonic transport and subsonic transports can be traced to two causes - the high-temperature environment and the disparity between subsonic and supersonic aerodynamics. The considerations which lead to the choice of speed, configuration and powerplant are considered and some details of their impact on specific areas are discussed. Finally, Concorde is used to illustrate the development of a practical supersonic transport and the development, from both theory and experiment, of the practical parameters and features for such a vehicle.

The effects of runway roughness on the dynamic response of airplanes

The purpose of this paper is to show the application of the perturbation technique in the study of the random response of a multidegree-of-freedom nonlinear system simulating an airplane moving with constant velocity along a runway whose profile is represented by a stationary random process. Using the pertinent characteristics of a supersonic civil transport being designed in the U.S.A., numerical results are produced for the response of a simplified idealization of the airplane.

Difficulties and Advantages of Supersonic Civil Transport—A Discussion

We have heard that the SST project is the largest and most expensive project ever undertaken. It is fairly large and it is expensive. When making comparisons, however, it is important to remember that major developments in aviation have rarely been cheap. For some civil projects the subsidy has been indirect. For example, the present generation of successful American long range air liners, notably the Boeing 707, has succeeded to a large family of military progenitors and thereby enjoyed its massive inheritance. Even so, funds spent on the 707 development must have been substantial, for many hundreds of aircraft needed to be sold before the break-even point was reached. Those firms in the USA, lacking the advantage of a military ancestor, must have seen the prospect of profitability in the civil field, in straight competition with those better placed, as an illusive difference between two very large sums—launching expenditure and prospective income.Now, and in the future, all civil projects everywhere must fight for existence without benefit of feed-back from a related defence project.The question is whether to fight at all in this remorseless arena. Presumably nearly all at a meeting of the Royal Aeronautical Society would not agree that this country should reject the challenge.

Difficulties and Advantages of Supersonic Civil Transport—A Discussion

THE SST project is the largest, most expensive and most dubious project ever undertaken in the development of civil aircraft. It is dubious because of the concern about the side effects of supersonic flying on a regular basis, the main one being the sonic boom. Apparently the more one learns about the sonic boom, the more intractable it appears.The project is unique in that in Europe it was instigated by, and financed by, the Governments for airlines and not by airlines. A similar, although not exactly the same, pattern is followed in the USA.Another main characteristic of the SST is that no airline has ever asked for it, but the project existing has tempted a few airlines to put in tentative orders, which has encouraged other airlines out of fear to put in other orders.The general run of technical unknowns is pretty well-known, one of them being how to get rid of the heat caused by the friction of the air at the high speeds involved. However, probably the greatest doubt lies in the improbability that the SST will be able to be profitable in operation. I agree that it is possible to make any given number of calculations on this matter, all with reasonable degrees of honesty, and half of them will show that airlines will make money and the other half will show the opposite. This is merely a measure of our lack of knowledge of these aircraft.

Engines for Supersonic Civil Transport Aircraft

Because of its high overall pressure ratio and good propulsive efficiency, the jet engine is very efficient for supersonic propulsion. A high thrust per unit power plant frontal area and per unit weight are primary requirements and these imply high combustion temperatures. For a Mach 2.0 aircraft, engine design problems other than this are not outside existing experience but additional problems, such as bearing cooling, become more serious at cruise Mach Numbers approaching 3.0. A variable intake is essential and the method of geometry variation and control requirements are described. Variable propulsion nozzle design is also an area of vital importance and it is not claimed that an entirely satisfactory solution, giving good performance with low drag in the transonic phase, has yet been achieved. The ‘sonic boom’ phenomenon can have an important influence on engine design, in that it may determine the maximum altitude at which the aircraft has to fly subsonically. Should this be appreciably above the tropopause, then it will not only influence the amount of thrust installed but may also dictate the fitment of reheat for the transonic acceleration. Take‐off noise is a requirement which can influence both the installed thrust and the choice of engine type. Despite the lack of firm standards for field noise and ‘coast‐over’ noise, there is good reason to believe that the noise levels of a supersonic transport need not exceed those of the quieter long‐range subsonic transports in service at this time.