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In the context of increasing need for step change in civil aeroplane energy efficiency, many innovative concepts are based on the idea of increasing integration of the traditionally segregated subsystems, the most prominent ones p...
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In the context of increasing need for step change in civil aeroplane energy efficiency, many innovative concepts are based on the idea of increasing integration of the traditionally segregated subsystems, the most prominent ones particularly relying on synergies between the propulsive system and the airframe. This paper presents a first step in building a multi-disciplinary platform for directly coupled airframe-engine (propulsive system) mission preliminary sizing and off-design performance estimation, constructed around commercial software Pacelab APD™ and PROOSIS™. The developed framework enables the user to mission-size an airframe (Pacelab APD) by directly querying a pre-sized engine model (PROOSIS). The infrastructure that enables direct communication between the two programs is based on open source methods, and is enabled by UDP sockets. Operational verification of the developed framework is performed on a short-medium range case study - Airbus A320-200 aeroplane and CFM56 engine cycle models. Several mission design loops and off-design simulations were carried out in order to assess the flexibility and robustness of the coupled environment. The preliminary results are coherent with respect to experience and theoretical expectations: for fixed aerodynamic and weight characteristics, at constant maximum takeoff weight the aeroplane range increases with increased engine bypass ratio and overall pressure ratio; the range is reduced with increasing engine non-propulsive offtakes in off-design operation. In turn, opposite tendencies were captured for the aeroplane maximum takeoff weight for a fixed objective range. The coupled operation for the studied test cases behaves robustly as long as the engine model is pre-sized and initialised carefully to match the aeroplane operating envelope. The average calculation time of a complete coupled mission sizing is of order of one minute. The presented work is a first step in a long-term effort to create a framework for multi-disciplinary sizing and performance simulations of innovative aeroplane concepts, with full system transparency available to the designer.
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Modern aviation has been focusing on hybrid-electric propulsion in recent years, aiming for concepts with lower atmospheric and acoustic pollution to improve social acceptance of the sector. Development of such new enabling techno...
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Modern aviation has been focusing on hybrid-electric propulsion in recent years, aiming for concepts with lower atmospheric and acoustic pollution to improve social acceptance of the sector. Development of such new enabling technologies results in emergence of whole new aircraft concepts like Electric Vertical Take-Off and Landing (eVTOL) for urban air mobility. The present work focuses on the preliminary design of a hybrid-electric Vertical Take-Off and Landing (VTOL) air vehicle with multiple ducted fans. A theoretical preliminary sizing model is proposed and then implemented in Pacelab APD™, a commercial preliminary design tool developed by PACE Aerospace Engineering and Information Technology GmbH. The performance deck for electric ducted fans is developed in parallel using PROOSIS™, a separate dedicated propulsive system simulation software, using flight conditions as input and providing appropriate performance characteristics as output. The targeted powertrain is completed with a turbogenerator, also modelled in PROOSIS as a generic turboshaft engine with an additional electric generator efficiency accounting. After having sized it at cruise condition, a specific fuel consumption map is retrieved. A typical urban air mobility operational framework is considered when building the design mission - composed of vertical take-off, hover, cruise and vertical landing - as well as a range of off-design use case scenarios. Power requirement in vertical flight segments is also estimated. An example of the developed model application in Pacelab APD is provided; it is inspired by existing concepts on the market. It presents a hybrid-electric powertrain with eight ducted fans and a fully composite airframe. The model is implemented in a customized version of APD, along with coding of the missing engineering objects and the propulsive system performance decks exported from PROOSIS. The design mission is then simulated and analysed, suggesting a feasible aircraft solution, which is later subject to sensitivity studies.
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摘要 :
Modern aviation has been focusing on hybrid-electric propulsion in recent years, aiming for concepts with lower atmospheric and acoustic pollution to improve social acceptance of the sector. Development of such new enabling techno...
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Modern aviation has been focusing on hybrid-electric propulsion in recent years, aiming for concepts with lower atmospheric and acoustic pollution to improve social acceptance of the sector. Development of such new enabling technologies results in emergence of whole new aircraft concepts like Electric Vertical Take-Off and Landing (eVTOL) for urban air mobility. The present work focuses on the preliminary design of a hybrid-electric Vertical Take-Off and Landing (VTOL) air vehicle with multiple ducted fans. A theoretical preliminary sizing model is proposed and then implemented in Pacelab APDIM, a commercial preliminary design tool developed by PACE Aerospace Engineering and Information Technology GmbH. The performance deck for electric ducted fans is developed in parallel using PROOSIS1M, a separate dedicated propulsive system simulation software, using flight conditions as input and providing appropriate performance characteristics as output. The targeted powertrain is completed with a turbogenerator, also modelled in PROOSIS as a generic turboshaft engine with an additional electric generator efficiency accounting. After having sized it at cruise condition, a specific fuel consumption map is retrieved. A typical urban air mobility operational framework is considered when building the design mission - composed of vertical take-off, hover, cruise and vertical landing - as well as a range of off-design use case scenarios. Power requirement in vertical flight segments is also estimated. An example of the developed model application in Pacelab APD is provided; it is inspired by existing concepts on the market. It presents a hybrid-electric powertrain with eight ducted fans and a fully composite airframe. The model is implemented in a customized version of APD, along with coding of the missing engineering objects and the propulsive system performance decks exported from PROOSIS. The design mission is then simulated and analysed, suggesting a feasible aircraft solution, which is later subject to sensitivity studies.
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The dropping of Precision Aerial Delivery Systems (PADS) aims at reaching the "higher, further and more reliable" triptych. Since the 2000s, the development of precise GPS and IMU position systems, and better estimation of wind an...
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The dropping of Precision Aerial Delivery Systems (PADS) aims at reaching the "higher, further and more reliable" triptych. Since the 2000s, the development of precise GPS and IMU position systems, and better estimation of wind and flight status have made possible more efficient control of PADS under a ram-air parachute. These allowed drops at ever-higher altitude and at ever further from target point. Nevertheless, the precision of the touchdown, involving the double issue of reaching a target point and the smoothness of the touchdown, has often shown shortcomings or at least a lack of reliability in the expected precision. Among the factors contributing to landing errors, unforeseen wind changes in the surface atmospheric layer are among the main causes of error. This is followed by inaccuracies in status estimation (sensors, real-time management, filtering), then by command modeling errors or also errors related to GNC algorithms. The necessary completeness and the proven complexity of mastering these aspects, generates development costs and significant experimental needs for a result that is not necessarily up to the level of the work. To overcome these limits of the "physical" (φ) or classic approach, a study was launched within the French Armament Procurement Agency DGA associated with its affiliated school ISAE-SUPAERO, to assess the possible relevance of applying Artificial Intelligence to manage the guidance and control of a load under a ram-air parachute, therefore by a so-called "AI" approach, and hence to improve the precision of PADS. Thus, the work reported here assesses the contribution of Reinforcement Learning (RL) technologies to the guidance of PADS. To do this, we will present the learning platform used, as well as its coupling to a ram-air parachute flight simulator based on the 9DDL flight dynamics model developed by ONERA [02]. We present the chosen RL algorithm, the learning process and some stability improvements in order to anticipate the reality gap between simulation and reality. A complementary work is also done to evaluate the robustness of the approach as for example here to make the comparison between different models (3DOF to 9DOF). At the end, the obtained results are then compared in the simulator against a classical approach based on the φ laws. These prerequisites lay the foundations for an evaluation of the relevance of the results obtained with regard to a double cross validation using a real mini-PADS prototype (EOLE).
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Aircraft operational performance is one of the key drivers to airline profitability and punctuality. Along with safety and technical performance, aircraft operational performance needs to be projected from the early stages of deve...
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Aircraft operational performance is one of the key drivers to airline profitability and punctuality. Along with safety and technical performance, aircraft operational performance needs to be projected from the early stages of development to design an aircraft that can fully meet the expectations of airlines and passengers. The ability of a system to meet its operational requirements in terms of reliability, availability and costs is termed as 'Operability'. This paper proposes a method to model the operability of an aircraft during early design and use it to predict its operational performance. Initially, in-service data is used to create a reference baseline for a system of interest. For a new design, the designers evaluate the changes (deltas) in terms of few high-level metrics from an operations point of view called Consolidated Operability Metrics. An operability model is developed using Bayesian networks that is then used to project the changes in operational performance of the new design in comparison to the baseline. This method will help aircraft architects in conducting trade-off studies during early design from an operational point of view.
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A reduced-order model to estimate the aerodynamic forces and moments of a propeller at incidence angle from 0° to 90° was presented. The objective was to provide an inexpensive and effective approach to analyse propeller perform...
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A reduced-order model to estimate the aerodynamic forces and moments of a propeller at incidence angle from 0° to 90° was presented. The objective was to provide an inexpensive and effective approach to analyse propeller performance of a vertical/short take-off and landing aerial vehicle during transition flight. The model was based on blade element theory and was coupled with an extended momentum theory or Pitt & Peters inflow model to include the asymmetrical flow condition. The aerofoil aerodynamic data was provided by an empirical model that extended lift and drag polar to a broad angle-of-attack range suitable in transition flight. Furthermore a rotational stall delay model and a radial flow correction model have been incorporated to include primary 3-dimensional effects. The result has been presented and compared with past experiment and unsteady Reynolds-averaged Navier-Stokes solution under similar conditions.
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A reduced-order model to estimate the aerodynamic forces and moments of a propeller at incidence angle from 0° to 90° was presented. The objective was to provide an inexpensive and effective approach to analyse propeller perform...
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A reduced-order model to estimate the aerodynamic forces and moments of a propeller at incidence angle from 0° to 90° was presented. The objective was to provide an inexpensive and effective approach to analyse propeller performance of a vertical/short take-off and landing aerial vehicle during transition flight. The model was based on blade element theory and was coupled with an extended momentum theory or Pitt & Peters inflow model to include the asymmetrical flow condition. The aerofoil aerodynamic data was provided by an empirical model that extended lift and drag polar to a broad angle-of-attack range suitable in transition flight. Furthermore a rotational stall delay model and a radial flow correction model have been incorporated to include primary 3-dimensional effects. The result has been presented and compared with past experiment and unsteady Reynolds-averaged Navier-Stokes solution under similar conditions.
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This paper addresses safe path planning problem in urban environments under onboard sensor availability uncertainty. In this context, an approach based on Mixed-Observability Markov Decision Process (MOMDP) is presented. Such a mo...
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This paper addresses safe path planning problem in urban environments under onboard sensor availability uncertainty. In this context, an approach based on Mixed-Observability Markov Decision Process (MOMDP) is presented. Such a model enables the planner to deal with a priori probabilistic sensor availability and path execution error propagation, the which depends on the navigation solution. Due to modelling particularities of this safe path planning problem, such as bounded hidden and fully observable state variables, discrete actions and particular transition function form, the belief state update function becomes a complex step that cannot be ignored during planning. Recent advances in Partially Observable Markov Decision Process (POMDP) solving have proposed a planning algorithm called POMCP, which is based on Monte-Carlo Tree Search method. It allows the planner to work on the history of the action-observation pairs without the need to compute belief state updates. Thereby, this paper proposes to apply a POMCP-like algorithm to solve the addressed MOMDP safe path planning problem. The obtained results show the feasibility of the approach and the impact of considering different a priori probabilistic sensor availability on the result policy.
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This paper addresses safe path planning problem in urban environments under onboard sensor availability uncertainty. In this context, an approach based on Mixed-Observability Markov Decision Process (MOMDP) is presented. Such a mo...
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This paper addresses safe path planning problem in urban environments under onboard sensor availability uncertainty. In this context, an approach based on Mixed-Observability Markov Decision Process (MOMDP) is presented. Such a model enables the planner to deal with a priori probabilistic sensor availability and path execution error propagation, the which depends on the navigation solution. Due to modelling particularities of this safe path planning problem, such as bounded hidden and fully observable state variables, discrete actions and particular transition function form, the belief state update function becomes a complex step that cannot be ignored during planning. Recent advances in Partially Observable Markov Decision Process (POMDP) solving have proposed a planning algorithm called POMCP, which is based on Monte-Carlo Tree Search method. It allows the planner to work on the history of the action-observation pairs without the need to compute belief state updates. Thereby, this paper proposes to apply a POMCP-like algorithm to solve the addressed MOMDP safe path planning problem. The obtained results show the feasibility of the approach and the impact of considering different a priori probabilistic sensor availability on the result policy.
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With more complex aircraft architectures, fast and cost-effective design iterations are key to improve overall fuel efficiency. This paper proposes to revisit a low-order unsteady modeling approach to replace costly full annulus U...
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With more complex aircraft architectures, fast and cost-effective design iterations are key to improve overall fuel efficiency. This paper proposes to revisit a low-order unsteady modeling approach to replace costly full annulus URANS simulation. Unsteady Body Force Methods (UBFM) could allow a significant cost reduction for fan distortion ingestion and operability assessment. In this approach, the bladed area in the computational domain is replaced by source terms in the Navier Stokes equations, and the cost of the simulation is reduced by a factor of 26. The operability of the fan is evaluated with and without distortion in order to assess the accuracy of the model. Previously published results of URANS simulations performed on the same fan subject to an unsteady vortex ingestion arc used as reference.1 The results show that our UBFM is able to predict rotating stall cells, with patterns and rotating speed similar to the URANS data.
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