101 research outputs found
System-level assessment of tail-mounted propellers for regional aircraft
No full textThree regional transport aircraft of different configuration are synthesized for the same design specification using an automated design routine. The first aircraft features wing-mounted propellers, the second aircraft features propellers mounted on the horizontal tail plane, while the last configuration replaces the horizontal and vertical tail with two ducted propellers mounted near the rear of the fuselage. These last two innovative configurations have the potential to reduce the cabin noise, while the ducted propeller could also reduce community noise. The analysis and design methods to size and analyze these configurations include weight and balance, stability and control, aerodynamic performance, and mission performance. Propeller slipstream effects are taken into account and demonstrated to play an important role in the sizing of the horizontal tail surface. A comparison study between the three aircraft for a harmonic mission of 1530km and 7500kg payload demonstrates that the aircraft with wing-mounted propellers has the lowest maximum take-off mass and burns the least amount of fuel. The two innovative configurations have slightly less performance, which is ultimately attributed to the large center-of-gravity excursion that stems from an aft-mounted propulsion system. A 3% increase in maximum takeoff weight is predicted along with a fuel burn increase between 5% and 10% for the innovative configurations, respectively. Further investigation of the underlying assumptions might improve these results in future studies.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Flight Performance and Propulsio
Supporting MDO through dynamic workflow (re)generation
No full textThe use of advancements in computing technology has enabled designers to perform more thorough and more detailed design studies. Multidisciplinary Design Optimization (MDO) architectures provide users with guidelines on how to structure their MDO problem, including the linking of disciplines and how to perform the optimization. However, complex MDO problems can consist of tens of disciplines and hundreds of design variables. Thus, the set-up of these problems can be complex and time consuming. In an attempt to reduce the time required and complexity of this set up, the main goal in this thesis is: "To develop and demonstrate a methodology for automatic workflow (re)generation to support MDO". The method to fulfill these requirements consists of three main steps. The first is the automatic generation of microworkflows, workflows representing the different disciplines of the problem. The user will need to specify the inputs, outputs and operations, after which the workflows are automatically generated. The second step involves the automatic storage of workflows. Workflows are stored in a graph database, allowing the addition of semantics to the data. Adding semantics allows a reasoner to understand what the data means, enabling the inferring of data not explicitly defined. OWL (Web Ontology Language) ontologies are used to supply structure to the workflow data and add semantics. In addition, materialization scripts are present to regenerate stored workflows. The final step of the implementation involves the automatic generation of simulation workflows according to different MDO architectures. This generation involves the materialization and adjustment of microworkflows and the creation of a ‘higher level’ workflow that links the disciplines and performs the optimization. The implementation of the automatic architecture generation has been validated using three case studies of varying complexity, amount of disciplines and discipline couplings. These case studies have shown a reduction of 93 to 98 % of time spent on the generation of simulation workflows representing the problem using an MDO architecture. In addition, the approach reduces the required user expertise and minimizes the amount of information the user needs to provide.Aerospace EngineeringFlight Performance and Propulsio
Drag reduction through a streamlined aerodynamic design process: Development and implementation of a methodology to accelerate the aerodynamic design process in the preliminary phase of car design
No full textContinuous innovation is very important to stay competitive in today’s world. Automotive manufacturers are an excellent example of this evolution when looking to new vehicle concepts. But also behind the scene, they have to be innovative in order to be able to keep up this progression. Aerodynamics has a large influence on the total performance of the car, and therefore fulfils a very important role in this innovation story. Aerodynamics is absolutely not straightforward which makes it on the one hand difficult to deal with and to estimate it influences, but on the other hand, this creates an improvement potential. Today’s passenger cars are already aerodynamically optimised to a fairly large extent, meaning improvements become rather marginal. To be able to keep this tendency of improving in the future, the aerodynamic design process has to be adapted. The focus of this work will be on the reduction of the air resistance of cars, which has a large influence on its top speed and fuel consumption. Especially the latter is very important today and will even gain more importance for future cars. Earlier research has shown that 70% of the reduction of the air resistance and the corresponding Cx value is done during the preliminary aerodynamic design phase. This phase is characterised by a high design freedom and a low level of detail of the corresponding design. Due to this, this early phase invites for shape optimisation of the basic aerodynamic shape having much more potential to achieve a lower Cx value. At the end of this phase, all fundamental parameters, dimensions etc. that define the final car will be fixed in order to begin the further detailed design during which detail optimisation is only possible anymore. This fundamental difference between the early phase and subsequent detailed design is responsible for their difference in influence on the final achieved Cx value and reduction. In order to achieve a successful aerodynamic design in terms of air resistance, the importance of that early design phase cannot be underestimated. To prevent aerodynamic improvements from stagnating, this preliminary design phase has to be fully exploited. Those preliminary phase can be split into three specific sub phases, namely the initial phase, preliminary studies and concept phase. In the first, the high level targets of the car design will be determined, which the final design should comply with. After this, as much as possible information and knowledge about the design has to be gathered during the so called preliminary studies. This knowledge will be used to formulate thoughtful concepts for the subsequent concept phase where they will be assessed and developed further until one final design concept remains which should comply with all the earlier defined high level targets. The quality of the information and knowledge gathered during those preliminary studies is therefore critical for a comprehensive final design. This is valid for the whole aerodynamic design and by extension also the total car design. But as already said, this work focuses on the design of the car exterior in terms of Cx value. It was observed in this work that the current situation has potential for improvement. More specifically, it was noticed that the aerodynamic department is occupied mainly with detail optimisation instead of the more favourable shape optimisation during those preliminary studies. The reason for this is due to a combination of their minor influence on the car exterior design compared to the aesthetics department and the current process flow during those studies. This current process flow is very inefficient and contains too much time-consuming and repetitive manual work. This combined with the short timespan of those preliminary studies lead to a limitation of the gathered knowledge of the car exterior design that is investigated. This is the main reason why the aerodynamicists are currently doing mainly detail instead of shape optimisation. For the latter, more investigations of higher quality (higher order) are required, which the current inefficient process flow does not allow for. Therefore, the aerodynamicists are limited to detail optimisation because of this, which is explained more into detail in this work. Thus, adapting the current process flow to allow the aerodynamic department to do shape instead of detail optimisation was found to be the main solution to improve and further reduce the Cx value and prevent it from stagnating in the future. The current process flow of those preliminary studies was analysed in this work and a suggested methodology that could accomplish those improvements was formulated based on this. The main difference of this methodology compared to the current situation is the implemented closed-loop instead of the open-loop modelling of the aerodynamic behaviour during those preliminary studies. This requires a fully automated process flow, which is missing in the current situation. In order to be able to also work out this suggested methodology to a fully working process flow, an automated generation of the geometric variants have to provided. This was achieved by developing a parametric geometry model capable of instantly delivering the required geometric variant without human interaction. The parametric model is an approximation of the real car exterior geometry, but its accuracy was proved with relevant CFD simulations. The closed-loop surrogate modelling is realised by using a MATLAB-based toolbox, called SuMo-toolbox, which is implemented in the software framework of the developed methodology. A secure shell connection between this software framework in MATLAB and the Linux machine, on which the simulations are done, assures a stable and fully automated process flow. After this working out of the presented methodology, a reality-based use-case was done to estimate its potential for improvements compared to the current situation. Promising results were already obtained which also confirm the promised theoretical improvements in praxis. Also conclusions and recommendations for future work or alternative implementations and extensions of this methodology are formulated in this work. This work was meant as an initial step and incentive to apply this methodology in the current industry. Before this could be possible, further research and work has to be done to make it practically implementable. This new process flow means a drastic change of the current one. It is typical for large companies to be unwilling to take this step. But if this methodology could be further developed so that it could fulfil its supposed role, namely improving and further reducing the Cx value of cars, it will become an important tool in the (near) future for manufacturers to become or stay ahead of their competitors. Certainly in today’s world of increasingly strict economics, its role cannot be underestimated.Flight Performance & PropulsionAerospace Engineerin
Advise, Formalize and Integrate MDO Architectures: A Methodology and Implementation
No full textFlight Performance and Propulsio
The Oval Fuselage: A New Structural Design Concept for Blended Wing Body Cabins
No full textFaced with the decreasing fossil fuel reserves and the need to decrease its environmental footprint, the aviation industry is searching for alternative fuels and more fuel efficient engines and aircraft. With the current designs reaching their limits, the industry has turned its attention to the family of all lifting bodies. Particularly blended wing body aircraft have received much interest, a combination of a lifting fuselage and a flying wing. It is commonly believed that this design has a high aerodynamic efficiency and lower structural weight fraction, which both contribute to a higher fuel efficiency. Though the concept has been around since World War II, no flying full-scale aircraft with a pressurized cabin currently exists. Additionally, the pressure cabins have so far been dictated by the aerodynamic design of the centre body. This thesis presents an alternative approach in blended wing body design, which has its roots in the design of conventional aircraft. For current aircraft a method called the `inside-out approach' is used, where the design of the fuselage is dictated by the requirements for the passenger and cargo compartment. Following this approach a blended wing body cabin consisting of four tangentially connected arcs, forming an oval fuselage cross-section with no need for an aerodynamic outer surface is designed. The arcs are supported by vertical and horizontal members, doubling as walls, floors and ceiling for the cabin. The research presented in this thesis describes the geometry determination and weight estimation for this new design, for pressurization, wing bending loads and longitudinal fuselage stresses. The weight estimation method that has been developed determines the thicknesses of the structural members per oval fuselage cross section, described by the four arcs and horizontal and vertical members, for a certain cabin geometry and the aforementioned loads. An imposed airfoil shape over the centre line of the cabin restricts the height of each oval cross-section. By placing these oval cross-sections in sequence, and interpolating between two neighbouring sections, a three-dimensional fuselage can be created that follows the airfoil shape. This airfoil-shaped fuselage is combined with outer wing sections, vertical tail planes, engines and landing gears to generate a complete blended wing body model. This model is analyzed by means of a Matlab optimization tool, which was adapted from a pre-existing blended wing body design tool. In this tool, the developed fuselage weight estimation is combined with a wing-weight estimation and an operative empty weight estimation to calculate the total operative empty weight. Three different conceptual design studies of blended wing body configurations, for 200, 400 and 800 passengers, have been optimized and assessed to investigate the feasibility of the new structural cabin design. These designs have been compared to another blended wing body cabin design and to conventional aircraft. In comparison to other blended wing bodies a lower fuel consumption, lower operative empty weight and longer range were found for the same maximum take-off weight and the same payload. A 400 passenger `oval-fuselage' blended wing body showed the most promising results with a 13% lower empty weight, a 6% better fuel consumption and almost 29% longer range. In comparison to the conventional airliners, this particular blended wing body showed a fuel consumption per transported kilogram that was 10% lower than that of the best performing conventional aircraft, the Boeing 777-200LR.Flight Performance and PropulsionAerospace Engineerin
Scalability analysis of radical technologies to various aircraft class: Part 1: initial designs
No full textVarious research initiatives in hybrid-electric/sustainable aviation typically address only a single vehicle or single vehicle class. However, novel propulsion and energy solutions can be expected to be differently applied in different vehicle classes. The objective of the EU funded research project CHYLA (Credible HYbrid eLectric Aircraft) is to identify areas suitable for scaling, as well as limitations or challenges for development for the applications of key radical technologies on different classes of aircraft. This article provides an overview of the design approach followed for the CHYLA project, as well as initial radical designs and comparison to the CHYLA baselines. These provide the starting point for both the sensitivity study which will be presented in a later scalability assessment and economical assessments in the CHYLA project. A variety of regional, short medium range and large aircraft has been designed, all according to the same TLAR yet without detailed tuning of important power control variables. Results are distinguishable between concepts and provide sufficient detail to capture the necessary effects. The reduction of fuel consumption will require detailed assessment and fine tuning, though reductions may be achievable for regional and possibly SMR aircraft
Scalability analysis of radical technologies to various aircraft class: Part 2: Sensitivity Analysis
No full textThis study aims at providing a landscape of opportunities and limitations for hybrid-electric aircraft (HEA) and hydrogen-powered aircraft by investigating several technological combinations applied to three aircraft classes: Regional (REG), Short-Medium Range (SMR) and Large Passenger Aircraft (LPA). The preliminary sizing of HEA using different hybrid-electric powertrain architectures, combined with various distributed propulsion layouts is conducted. The resulting HEA are then compared to a conventional design, on the basis of several performance metrics, for variations in harmonic range and passenger capacity. Throughout the design space considered, it is found that opportunities for radical aircraft design are scarce and offer limited prospective.<br/
Structural Sizing Method for Propulsive Empennage System: Weight Estimation of Ducted Propeller Systems that Provide Longitudinal and Lateral Stability
No full textFlight Performance and Propulsion department of Aerospace Engineering, Delft University of Technology has proposed an effective and sustainable solution to the main challenges aviation is currently facing, namely the raising concerns regarding the environmental and health impact of the industry. Delft University Unconventional Concept (DUUC) has a conventional fuselage coupled with clean wing that is expected to facilitate laminar flow. Furthermore, two ducted propellers are positioned aft on the tail cone installed via pylons. The ducts are designed such that they perform multiple functions: they provide sufficient longitudinal and directional stability, resulting in no tail-configuration and possible weight reduction, improve propulsive performance by increasing static thrust, assure higher safety in blade-loss and reduce cabin and community noise. This research proposes a physics-based design-sensitive weight estimation method of such propulsive empennage suitable for conceptual design phase.Aerospace Engineerin
Semi-Analytical Weight Estimation Method for Fuselages with Oval Cross-Section
No full textThis paper presents a semi-analytical method for the weight estimation of fuselages with an oval cross-section, applied to blended wing body aircraft. The weight estimation of the fuselage primary structure is based on a structural analysis of two-dimensional crosssections and it is completed by a set of empirical relations for the weight estimation of the secondary structure and non-structural items. A conceptual design study on a stable (5% static margin), 400-passenger blended wing body aircraft has been performed with the weight estimation method implemented in an aircraft conceptual-design program. A top level requirement for the harmonic range of 15,200km was imposed on the design. From the anaylis a maximum take-off weight of 395 metric tons has been found, with an operative empty weight fraction of 45% and a fuselage airframe weight of 47.3 metric tons (amounting to 26% of the operative empty weight). The results of this study are presented in comparison to the Boeing 777-200LR airliner, showing a slightly higher operative empty weight fraction, a lower fuel consumption of 2.05kg per passenger per 100km.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin
Range equation for hybrid-electric aircraft with constant power split
No full textThere has been a surge in research related to hybrid-/ electric propulsion (HEP) over the past decade, since this technology has the potential to reduce the energy consumption and in-flight emissions of commercial aircraft and, therefore, to bring the aviation sector closer to the sustainability targets established by the European Commission [1] and NASA [2]. Previous studies have shown that hybrid-electric [3,4] and fully-electric [5] general-aviation aircraft can lead to a reduction in both emissions and operating costs for short ranges, when compared with fuel-based alternatives. However, due to the enormous energy and power requirements of large passenger aircraft, fully battery-based propulsion is not a viable option to substantially reduce the climate impact of the aviation sector as a whole [6], unless the mission range is significantly reduced, or unrealistically high battery energy densities are assumed [7]. For this reason, hybrid architectures (especially parallel [8–10] and turboelectric [11–14] ones) are often investigated as a potential solution for large passenger aircraft.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Flight Performance and Propulsio
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