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This paper aims to describe the selection of the ideal variable inlet concept group by using results of aerodynamic investigations, system safety analyses and integration studies.

Aerodynamic and functional inlet requirements are explained and variable inlet concept groups are introduced. The concept evaluation by means of a weighted point rating is presented. The respective concept groups are analysed and evaluated regarding economic, functional and safety requirements.

By means of this evaluation, the concept group that adjusts the inlet geometry by rigid segment repositioning is identified as most suitable concept group.

The early selection of the most suitable concept group enables more detailed subsequent concept investigations, potentially enabling the technology of variable inlets for future commercial aircraft.

This paper presents a broad survey of the structural problems associated with variable geometry for aircraft. Variable sweep allows an aircraft to fly throughout a broad regime of speed and altitude efficiently and without excessive power requirements. Tailored lift drag, improved ride quality, lessening of fatigue damage, and reasonable control sensitivities are advantages. Structural problems fall into two general categories: (1) Because of the number of wing positions, the equivalent of many fixed‐wing aircraft must be investigated, analysed and tested; (2) there are unusual problems which have heretofore not been important considerations in design. Category (1) presents the problem of managing and assimilating large amounts of data. Computer pogrammes and a family of cross‐plots assist greatly. Category (2) presents new fail‐safe criteria, a large lumber of possible flutter‐critical configurations, unavoidable free play in mechanisms which affect flutter speeds, dynamic loads, pivot mechanism bearing life, and requires high reliability in materials. Analyses and wind‐tunnel tests have shown that free play in mechanical joints may or may not cause significant service problems depending upon the mechanical arrangement selected and the actual degree of free play under service conditions.

This paper aims to design an optimal shape for an annular S-duct, considering both energy losses and exit flow uniformity, starting from a given baseline design. Moreover, this paper seeks to identify the design factors that affect the optimal annular S-duct designs.

The author has carried out computational fluid dynamic (CFD)-based shape optimization relative to five distinct numerical objectives, to understand their interrelations in optimal designs. Starting from a given baseline S-duct design, they have applied control node-induced shape deformations and high-order polynomial response surfaces for modeling the functional relationships between the shape variables and the numerical objectives. A statistical correlation analysis is carried out across the optimal designs.

The author has shown by single-objective optimization that the two typical goals in S-duct design, energy loss minimization and exit flow uniformity, are mutually contradictory. He has presented a multi-objective solution for an optimal shape, reducing the total pressure loss by 15.6 per cent and the normalized absolute radial exit velocity by 34.2 per cent relative to a baseline design. For each of the five numerical objectives, the best optimization results are obtained by using high-order polynomial models.

The methodology is applicable to axisymmetric two-dimensional geometry models.

This paper applies a recently introduced shape optimization methodology to annular S-ducts, and, it is, to the author’s knowledge, the first paper to point out that the two widely studied design objectives for annular S-ducts are contradictory. This paper also addresses the value of using high-order polynomial response surface models in CFD-based shape optimization.

The purpose of this paper is to theoretically analyze an innovative form of variable bearing configuration having four pads with unique adjustability principle operated under journal misaligned conditions. The parameters such as load positions, degrees of misalignment (DM) and pad adjustment configurations influencing the steady-state performance of the four-pad adjustable bearing are detailed in this paper.

The proposed adjustable pad geometry possesses the ability to undergo radial and tilt motions in both inward and outward directions. Analysis is carried out by considering journal misalignment in vertical and horizontal planes with bearing modelled for load-on-pad and load-between-pad configurations. The film thickness equation derived to incorporate the radial and tilt adjustment parameters is further modified to accommodate the different load orientations and misaligned journal conditions. The pressure field equation is solved by applying finite-difference technique combined with Gauss Siedel iterative method.

At higher DM, peak pressures generated in the minimum film thickness region near the pad ends highly influences the bearing load carrying capacity. Results indicated that the adjustable four-pad bearing geometry is highly efficient in withstanding the journal misalignment by radially displacing and tilting the four pads in negative directions.

For bearing designers, this research highlights the importance of considering the misalignment factor during the design stages of an adjustable journal bearing. The proposed adjustability concept is proven to be effective enough to improve the bearing performance and, in turn, withstand the journal misalignment.

Arguments in favour of selecting a cruising speed of about M=2.0 for a long‐range supersonic transport aircraft have been given by Morgan, and Kuchemann has shown that the slender wing shapes provide the basis for the layout of the aircraft, and has given the general properties which would lead to the achievement of optimum cruising lift‐drag ratios. The four components of supersonic drag were considered and with reference to a datum wing it was shown that the layout selected for best cruising efficiency alone would not give the lightest aircraft for the required duty if the influence of off‐design performance and component weights were taken into account. The parameter s/l was shown to be the effective variable and it was suggested that layouts having reduced wing area and increased span to length ratios (s/l) were likely to be the most successful. Bearing in mind the extra power required, calculations indicated that a reduction in plan area from the datum could give lower approach speed, reduced take‐off distance and a reduction in noise intensity. Further trends in this direction indicate aircraft shapes having a high percentage of their total volume contained within the fuselage, and it might then be possible to produce a favourable interference force between the wing and fuselage flow fields and so to improve the lift‐drag ratios which had been assumed in the derivation of these shapes. In the discussion that followed it was considered that forward view promised to be as good as for current subsonic aircraft, and the author stated that mock‐ups to investigate this item were being prepared. It was considered that the expense and complication of variable geometry were not acceptable in a first generation supersonic transport.

A new design‐for‐manufacturing method, called the geometric tailoring (GT), and the associated digital interface concept have been developed that enable the design activities to be separated from the manufacturing activities. Conditions for the successful application of this method are investigated. The GT method is demonstrated for rapid prototyping and rapid tooling technologies, where prototype parts are required to match the production properties as closely as possible. This method is embodied in a system called the rapid tooling testbed (RTTB). Research work is presented on GT and the distributed computing environment underlying the RTTB. Examples are summarized from the usage of this method and testbed.

Analytical target cascading (ATC) is a hierarchical multi‐level design methodology. According to the state‐of‐the‐art, it is confirmed that for problems with unattainable targets, strict design consistency cannot be achieved with finite weighting factors. This paper aims to address these issues.

A new formulation is proposed to improve the ATC convergence. The weighted sum of deviation metric is transformed into a multi‐objective formulation. An original optimization problem with a single global optimal solution is used as a benchmark.

It is found that carrying out an industrial application to design optimally a tram traction system demonstrates the efficiency of the proposed solution.

This paper is of value in showing how to improve the convergence of a multi‐level optimization algorithm by best management of the consistency constraints.

Suggests that the next civil supersonic passenger aircraft project will pose a number of challenges. The propulsion system for this aircraft will have to achieve economic operation for both supersonic and subsonic cruise modes. In addition, the current and intended noise and pollutant emissions legislation will have to be met. Suggests that, while there are a number of proposed engines for the next generation civil supersonic aircraft, they all exhibit difficulties in meeting the compromises inherent in the engine duty. Offers a novel solution based on a unique design. Discusses the underlying issues and presents the design based on retractable fans driven by a single stage double pass tip turbine.

Already in service or under development are over a dozen or more aircraft and missiles in the general Mach 2 to 5 bracket using air breathing propulsion systems. Other major high speed projects are also at the study stage. While the subsonic combustion ramjet can span this field and beyond, the turbine engine has to transmute through a number of basic configurations to maintain an optimum mode of propulsion as Mach number increases. At present the ramjet is confined to use in missiles and the turbine engine is primarily an aircraft power unit. The trend is apparent already, however, for the turbine engine to move closer to a ramjet cycle when used above Mach 3. The following paper summarizes the features of the major high speed aircraft and missiles in being or soon to be built.

This paper aims to reveal the influence of selected geometric parameters on the aerodynamic performance of circular variable aero engine inlets in transonic and supersonic civil aviation.

The trade-off in inlet design and aerodynamic evaluation parameters is presented. The approach to investigate the dependencies between the aerodynamic and geometric parameters at different flight conditions by means of a parametric design study is introduced.

The dependencies of inlet drag and efficiency from geometric parameters at flight speeds of Mach 0.95 up to Mach 1.6 are identified. Although entailing additional weight, the inlet length represents the parameter with the highest potential for drag reduction by up to 50% in the selected design space. Ideal geometries for variable pitot inlets are determined. After considering weight, their potential range benefit nearly disappears for subsonic applications, but remains above 20% for supersonic flight at Mach 1.6.

Hence, the technology of circular variable pitot inlets for supersonic transport aircraft could be a way to achieve the ambitious ecological, safety and economic goals for future civil aviation.