Progress in Aerospace Sciences最新文献

The aviation industry has seen a lot of innovation over the last 125 years. Advancements such as transatlantic flight and the development of avionics technologies and composite materials have changed how we think about what the future will hold. Advanced aviation technologies such as remotely piloted aircraft systems (i.e., “drones”) and urban air mobility may be the next revolution in the aviation industry. While many in the aviation industry look forward to greater inclusion of these technologies, the public may have a different perspective. This review aims to examine the factors that may influence one's perception of advanced aviation technologies. First, an overview of the technologies is presented to categorize the different types of drones and how they are used, followed by a discussion on the principles of technological adoption. Next, data from past studies investigating the public perception of drones and air taxis was collected and analyzed to discover if any patterns exist in terms of overall acceptance or mission preferences, and to determine the root causes of hesitancy towards this emerging technology. The trends suggest that drones have become increasingly accepted as public awareness rises, and missions that support the common good are viewed more favourably than commercial uses such as package delivery or air taxi services. The major obstacles include the perceived level of risk, pre-existing judgement as to the technological reliability, as well as the lack of perceived benefits when compared to existing technologies. Each of these topics are discussed and finally, a roadmap towards public acceptance is presented, incorporating the viewpoints of the public, drone users, and regulatory authorities. Together, this review discusses the current state of the field and what must be done to better integrate advanced aviation technologies into everyday life.

The aviation sector is experiencing an increasing pressure to reduce emissions via long-term strategies for a ceaselessly growing number of flight passengers. Aircraft currently in operation have typically been designed by considering the airframe somewhat separately from the propulsion system. In doing so, conventional aero-engine architectures are approaching their limits in terms of propulsive efficiency, with technological advancements yielding diminishing returns. A promising alternative architecture for improving the overall performance of the next generation of commercial aircraft relies upon boundary layer ingestion (BLI). This technology aerodynamically couples the airframe with a strategically positioned propulsion system to purposely ingest the airframe’s boundary layer flow. Nonetheless, there is a lack in consensus surrounding the interpretation and quantification of BLI benefits. This is primarily because conventional performance accounting methods breakdown in scenarios of strong aerodynamic coupling. Subsequently, there is a major challenge in defining appropriate performance metrics to provide a consistent measurement and comparison of the potential benefits. This review examines the various accounting methods and metrics that have been applied in evaluating BLI performance. These are discussed and critiqued in the context of both numerical and experimental models. Numerically, the geometric, aerodynamic and propulsive models are sorted by their orders of fidelity along with the plenitude of methods used for flow feature identification enabling a phenomenological understanding of BLI. Particular attention is then given to experimental BLI models with their different set-ups, methods and associated limitations and uncertainties. Finally, the numerous unconventional BLI aircraft concepts are categorised, compared and critiqued with reference to their associated design exploration and optimisation studies.

As climate change is exacerbated and existing resources are depleted, the need for sustainable industries becomes ever so important. Aviation is not an exception. Despite the overall carbon dioxide emissions related to the aviation sector accounts for 2%–4% currently, forecasts for air travel indicate an annual growth of 3%–5% and other industries present more potential to reduce carbon emissions once they recur to an increasing use of renewable energies. This option is more difficult in aeronautics since an efficient and lighter energy storage system is required and the current state of the art in battery technology is far from the specific energy densities of fossil fuels and its production is not friendly to the environment. Thus, a herculean effort to integrate several promising mitigation strategies in an efficient way is required. In this paper, a review of the most upfront solutions towards greener aviation is presented and categorized as follows: concepts of operations, energy storage, propulsion systems, aerodynamics, structures, materials, and manufacturing processes. In the end, potential synergies between the different technologies to achieve green aviation are proposed.

Unconventional configuration aircraft are not often designed due to many problems, mainly with stability and trim. However, they could be very promising and these problems can be compensated by extraordinary performance characteristics. Therefore, despite the difficulties in the design process, they are chosen, giving a chance to design and build a truly competitive aircraft. Paper presents the analysis of flying qualities of most often used unconventional configurations: canard, flying wing, three surface tandem wing and box wing. The stability analysis is presented in terms of basic static stability and full 6 DoF dynamic analysis. The flying qualities based on airworthiness regulation and MIL specification are presented and commented. Examples of results related to real projects realized during the last decade are presented and discussed.

Dynamic stall has been a technical challenge and a fluid dynamical subject of interest for more than fifty years; but in the last decade significant advances have been made in the understanding, prediction, modeling, and control of dynamic stall on rotors. This paper provides a summary of the state of the art of dynamic stall experiments and future directions in the understanding of dynamic stall on rotors. Experimental data sets are discussed, as well the direction of future research for control of dynamic stall. Coordinated testing between airfoils and rotating blades, as well as close integration between computational and experimental studies were found to be productive approaches. Advanced analysis methods, including statistical methods, modal representations, and artificial intelligence methods have led to significant advances in the understanding of dynamic stall. Investigations of dynamic stall control devices have allowed many useful targeted investigations of the transition to separated flow, but have not yet resulted in a commercially implemented device.

The main features and key problems in the development of air-breathing electric propulsion (ABEP) are outlined. Qualitative differences between ABEP and its closest predecessor, electric propulsion (EP), are highlighted. The necessary conditions for the long-term maintenance of spacecraft with ABEP in ultra-low (120–250 km) orbits (ULEO) are formulated. EP technologies, which have the best prospects for application in future ABEP, are shown. Estimates of the feasibility of long-term missions in ULEO are presented, including those based on the integrated optimization of the layout of spacecraft with ABEP and solar arrays. The main results of investigations of spacecraft maneuverability are described.

The review uses the results of studies published mainly in recent years. At the same time, some historical facts of first practical steps in EP- and ABEP-technology development, which remained out of the attention of a wide audience due to different reasons, are described. The authors felt free of giving their own assessment of a number of the results presented in key areas of the research.

Sustainable alternative fuels, or SAFs, are recognized to have lower carbon footprints and emit fewer greenhouse emissions. As a carbon-neutral alternative and intended drop-in fuels, SAFs would be an appropriate path forward for sustainable aviation. Current approved drop-in fuels enable 50% blending of SAFs, which decreases CO₂ emissions up to 40%. However, CO₂ emissions can be reduced much further by using 100% SAFs or hydrogen. Comprehensive analysis of SAFs in terms of their operational performance, impact on gaseous and particulate emissions, seal swell, engine and fuel systems compatibility, blow-off limits, ignition and relight, vibrations, and noise is essential to move towards 100% SAFs. Furthermore, SAF has been demonstrated to reduce other emissions like NOx, particulate and CO₂ emissions subjective to the fuel production pathways. Therefore, engineering novel fuels and innovative production pathways may lower emissions and reduce the costs of aircraft system design and operation, resulting in cheaper air travel. This study thoroughly examined and discussed all the aspects mentioned above. Hydrogen, a potential competitor for SAFs, has also been analyzed in this study in terms of future production capability to meet aviation needs and the impact of hydrogen combustion on design changes, emissions, and fuel systems. Furthermore, to reduce experimental costs related to SAFs, this study explored approaches for modeling and predicting novel fuel performance in the preliminary stages of fuel assessment.

Designing an airframe is a complex process as it requires knowledge from multiple disciplines such as aerodynamics, structural mechanics, manufacturing, flight dynamics, which individually lead to very different optimal designs. Furthermore, the growing use of Carbon Fibre Reinforced Plastics (CFRP), while allowing for more design freedom, has at the same time increased the complexity of the structural designers job. This has sparked the development of Multidisciplinary Design Optimization (MDO), a framework aimed at integrating intelligence from multiple disciplines in one optimal design. Initially employed as a tool to coordinate the work of several design teams over months, MDO is now becoming an integrated software procedure which has evolved over the decades and has become a prominent tool in modern design of aerostructures.

A modern challenge in airframe design is the early use of MDO, motivated by a pressing industrial need for an increased level of detail at the beginning of the design process, to minimize late setbacks in product development. Originally employed only during preliminary design, MDO has recently being pushed into early evaluation of conceptual designs with the outlook of becoming established in the conceptual stage. Using MDO during conceptual design is a promising way to address the paradox of design. By improving each concept, evaluating whether it is capable of meeting the design requirements and computing the sensitivities of various performance measures with respect to a design change, MDO enables designers to gain valuable knowledge in a design phase, in which most of the design freedom is still available.

We hereby exhibit the contemporary trends of MDO with specific focus on composite aircraft and aerial vehicles. We present the recent developments and current state-of-the-art, describing the contemporary challenges and requirements for innovation that are in the development process by academic and industrial researchers, as well as the challenges designers face in further improving the MDO workflow. Within the European OptiMACS project, we devised a novel holistic MDO approach to integrate a number of solutions to challenges identified as industrial technological gaps. These include two-stage optimization for layers of composites, addressing the presence of process-induced distortions and consideration of advanced failure criteria, including refined local models in early design stages, and seamlessly integrating software tools in the design process. The proposed methods are integrated and tested for structural case studies and the obtained results show the potential benefits of their integration into MDO tools.