1,720,966 research outputs found
A hierarchical life cycle cost model for a set of aero-engine components
No full textThe aero-engine is probably the most complex and vital part of civil and military aircrafts, and it is usually an important cost element of the aircraft at acquisition and operation periods. The reduction of acquisition, operation and support costs for civil and defence sectors is going to be the main driving force for aero-engine manufacturers during the next decades. Additionally, it is a well known fact that the maintenance costs of aero-engines can surpass their acquisition costs by a factor of two. Therefore, efficient and accurate prediction of aero-engine maintenance life cycle cost is vitally important for aero-engine manufacturers. For this paper we restrict ourselves to a simplified problem that deals with the life cycle cost of a set of
aero-engine components, such as high pressure turbine blades, in isolation of other components of the engine. These engine components are assumed be suffering from a number of different deterioration mechanisms that may force that component to be repaired or replaced at predetermined shop visits. A hierarchical and object oriented costing model will be presented and its scope, extensibility and maintainability will be discussed
Design and flight test of a civil unmanned aerial vehicle for maritime patrol: the use of 3D-printed structural components
No full textThis paper describes the design of the “Spotter” unmanned aerial vehicle, developed by the University of Southampton as part of the 2SEAS-3i European Interreg project. Spotter is a twin engine, 4m wing span, fixed-wing aircraft which has been designed to perform long-endurance, all-weather patrol missions in coastal and maritime environments. Reliability and safety have been among the strongest design drivers of this project; Spotter is able to survive the failure of one engine and of any single control surface. A modular approach has been adopted for the payload unit in order to allow the users to rapidly interchange the sensors required to perform different missions.One of the most innovative aspects of Spotter is the extensive use of the Selective Laser Sintering (SLS) technology (also known as 3D printing) for many of the components of its airframe. By eliminating tooling and manual labour, the 3D printing technology allows the designer to produce complex and high-performance structures at a relatively low cost and within hours of the completion of the design. Spotter and a sub-20kg version, codenamed 2SEAS-20, have undergone an extensive flight test campaign, totalling hundreds of autonomous flights (including autonomous take-off and landings) and many flight hours. This has provided the opportunity to test the reliability and robustness of the system and to gain a deeper insight into the opportunities and problems presented by the use of 3D printed structures for large airframe components
Design and implementation of a low cost mini quadrotor for vision based maneuvers in GPS denied environments
No full textThis paper presents the design and implementation detail of an advanced mini quadrotor system, including the low cost commercial-off-the-shelf (COTS) electronics and advanced control algorithm. The proposed quadrotor has a gross takeoff weight of 758g and 360mm frame diagonal size. It is capable of semi-autonomous maneuver in GPS denied environments, solely relying on onboard sensors and computers. A globally defined quadrotor model is formularized, and a nonlinear velocity tracking controller is implemented on the special Euclidean group SE(3). An optical flow and ultrasonic-based onboard downward-facing camera is used as the primary sensor to provide velocity and altitude measurement feedback for the controller. The control and sensor fusion algorithm is developed under Arduino compatible open source electronics.</p
Spatiotemporal ground risk mapping for uncrewed aircraft systems operations
No full textIn this paper we propose the use of spatiotemporal population density data in the analysis of ground risk posed by uncrewed aircraft system (UAS) operations. The spatiotemporal population density maps are generated through the combination of authoritative data sources, open source geospatial databases, and past works to dynamically classify proportions of a population to their expected daily activities based upon a given time. This adds a further dimension to analysis allowing evaluation and optimization of ground risk, both spatially and temporally. This approach is used to analyze the ground risk posed under ballistic and gliding descents of a parameterized UAS along a case study path. An open source tool is implemented as part of this work to aid the decision making of operators and promote safer UAS operations
Strategic jet engine system design in light of uncertain fuel and carbon prices
No full textThis paper presents a project that is investigating which cruise speed the next generation of short-haul aircraft with 150 seats should fly at and which combination of advanced engine technologies should be employed in order to make the profit generated by the aircraft robust to uncertain fuel and carbon prices in Europe in 2030. To answer this question, an optimization loop is being set up in MATLAB consisting of five modules, including an aircraft design, a travel demand, a modal shift, a flight profile, and an engine design element. The first three modules were tested in a preliminary study that analyzed the effect of high and low fuel and carbon prices on the optimum aircraft design and its ideal cruise speed. The results indicate that if oil and CO2 prices were to rise significantly, a slower turboprop aircraft would be more profitable in terms of Surplus Value in comparison to a conventional turbofan design. If prices were to reduce, however, a faster turbofan aircraft would offer a superior business case. The study also showed that making realistic Surplus Value predictions is more difficult than forecasting costs
Modelling the life cycle cost of aero-engine maintenance
No full textThis paper presents an approach of modelling the maintenance Life Cycle Cost (LCC) of an aero-engine which links the capabilities of hierarchical modelling and discrete-event simulation (DES) tools. It follows up on work previously done on a component level hierarchical cost estimation model. It is concluded that, as the calculation of a LCC involves a highly diverse set of representations and processes, it is undesirable to use a single software tool to undertake this task. This work seeks to demonstrate how different modelling paradigms should be used in tandem to produce an elegant solution. The individual parts of the model and the results generated are presented and discussed. Essentially, the approach shows how a design parameter can be linked to the resultant LCC to help form cause and effect relationships
Better design decisions through operational modeling during the early design phases
No full textThis work presents an operational simulation based on a unique mission ontology that enables recreating any aviation scenario using a small set of parameters. The tool is designed to suit the early design phases where time pressures, uncertainties and knowledge gaps peak. It is embedded in a stack of software allowing early design phase optimization based on operational constraints. This stack was used to design and build several Unmanned Aerial Vehicles. Two case studies demonstrate how the tool can act as a decision support or optimization tool, leading to improved designs and better operations. It is found that early design decisions can be based on a more rigorous analysis and that it is possible to optimize both the design and the operational environment by employing an operational simulation
Cost-driven build orientation and bin packing of parts in Selective Laser Melting (SLM)
No full textSelective Laser Melting (SLM) is an additive manufacturing process capable of producing mixed batches of parts simultaneously within a single build. The build orientation of a part in SLM is a key process parameter, affecting the build cost, time and quality, as well as batch size. Choosing an optimal arrangement of multiple heterogeneous parts inside the SLM machine also presents a challenging irregular bin packing problem. Since the two problems are interdependent, this paper addresses the combined problem of finding an optimal build orientation and two-dimensional irregular bin packing solution of a mixed batch of parts across identical SLM machines. We address this problem specifically in the context of low-volume high-variety (LVHV) production in the aerospace sector, using total build cost as the objective function. To solve this problem, we present an Iterative Tabu Search Procedure (ITSP), which consists of six distinct stages. We test each stage in the ITSP on 27 manually generated instances, based on 68 unique geometries ranging in convexity and size, including six real-life components from the aerospace industry. Two of the six stages, which are driven by support structure volume, returned the highest improvement in cost. Overall, the results showed an average cost improvement of 16.2% over the initial solution. The initial solution of the procedure was benchmarked against a commercial software, showing comparable results
Approaches to modeling the gas-turbine maintenance process
Full text linkDiscrete-event modeling has long been used for logistics and scheduling problems, while multi--agent modelling closely matches human decision-making process. In this paper a metric-based comparison between the traditional discrete-event and the emerging agent-based modeling approaches is reported. The case study involved the implementation of two functionally identical models based on a realistic, non-trivial, civil aircraft gas turbine global repair operation. The size, structural complexity, and coupling metrics from the two models were used to gauge the benefits and drawbacks of each modeling paradigm. The agent-based model was significantly better than the discrete-event model in terms of execution times, scalability, understandability, modifiability, and structural flexibility. In contrast, and importantly in an engineering context, the discrete-event model guaranteed predictable and repeatable results and was comparatively easy to test because of its single-threaded operation. However, neither modeling approach on its own possesses all these characteristics nor can each handle the wide range of resolutions and scales frequently encountered in problems exemplified by the case study scenario. It is recognized that agent-based modeling can emulate high-level human decision-making and communication closely while discrete-event modeling provides a good fit for low-level sequential processes such as those found in manufacturing and logistics
Quantifying uncertainties during the early design stage of a gas turbine disc by utilizing a bayesian framework
No full textQuantifying uncertainties regarding the grain size of the turbine disk has been identified as a crucial aspect for the preliminary design stage. The reason for that is because the grain size is correlated to the life of the component which should preferably be maximized or at least quantified to the best of the designer’s abilities. In the grand scheme of things, this ultimately translates into a potential competitive advantage for the aero engine company. The prime focus of this paper is the investigation of material properties which was done by combining simulation and experimental data within a Bayesian framework in order to enhance the decision making process during the preliminary design stage. The aim of the case study presented here was to show how the physical processes can be modelled using a Bayesian network which updates prior probability distributions with real data in order to obtain more accurate predictors of reality. The first part of the paper explains the theory behind the framework, while the latter half shows some results as well as some conclusions which can be drawn.</p
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